Keywords: hardward module components, digital signature
Network Working Group R. Housley
Request for Comments: 4108 Vigil Security
Category: Standards Track August 2005
Using Cryptographic Message Syntax (CMS) to Protect Firmware Packages
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes the use of the Cryptographic Message Syntax
(CMS) to protect firmware packages, which provide object code for one
or more hardware module components. CMS is specified in RFC 3852. A
digital signature is used to protect the firmware package from
undetected modification and to provide data origin authentication.
Encryption is optionally used to protect the firmware package from
disclosure, and compression is optionally used to reduce the size of
the protected firmware package. A firmware package loading receipt
can optionally be generated to acknowledge the successful loading of
a firmware package. Similarly, a firmware package load error report
can optionally be generated to convey the failure to load a firmware
package.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
Table of Contents
1. Introduction ....................................................3
1.1. Terminology ................................................5
1.2. Architectural Elements .....................................5
1.2.1. Hardware Module Requirements ........................7
1.2.2. Firmware Package Requirements .......................8
1.2.3. Bootstrap Loader Requirements .......................9
1.2.3.1. Legacy Stale Version Processing ...........11
1.2.3.2. Preferred Stale Version Processing ........12
1.2.4. Trust Anchors ......................................12
1.2.5. Cryptographic and Compression Algorithm
Requirements .......................................13
1.3. Hardware Module Security Architecture .....................14
1.4. ASN.1 Encoding ............................................14
1.5. Protected Firmware Package Loading ........................15
2. Firmware Package Protection ....................................15
2.1. Firmware Package Protection CMS Content Type Profile ......18
2.1.1. ContentInfo ........................................18
2.1.2. SignedData .........................................18
2.1.2.1. SignerInfo ................................19
2.1.2.2. EncapsulatedContentInfo ...................20
2.1.3. EncryptedData ......................................20
2.1.3.1. EncryptedContentInfo ......................21
2.1.4. CompressedData .....................................21
2.1.4.1. EncapsulatedContentInfo ...................22
2.1.5. FirmwarePkgData ....................................22
2.2. Signed Attributes .........................................22
2.2.1. Content Type .......................................23
2.2.2. Message Digest .....................................24
2.2.3. Firmware Package Identifier ........................24
2.2.4. Target Hardware Module Identifiers .................25
2.2.5. Decrypt Key Identifier .............................26
2.2.6. Implemented Crypto Algorithms ......................26
2.2.7. Implemented Compression Algorithms .................27
2.2.8. Community Identifiers ..............................27
2.2.9. Firmware Package Information .......................29
2.2.10. Firmware Package Message Digest ...................30
2.2.11. Signing Time ......................................30
2.2.12. Content Hints .....................................31
2.2.13. Signing Certificate ...............................31
2.3. Unsigned Attributes .......................................32
2.3.1. Wrapped Firmware Decryption Key ....................33
3. Firmware Package Load Receipt ..................................34
3.1. Firmware Package Load Receipt CMS Content Type Profile ....36
3.1.1. ContentInfo ........................................36
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
3.1.2. SignedData .........................................36
3.1.2.1. SignerInfo ................................37
3.1.2.2. EncapsulatedContentInfo ...................38
3.1.3. FirmwarePackageLoadReceipt .........................38
3.2. Signed Attributes .........................................40
3.2.1. Content Type .......................................40
3.2.2. Message Digest .....................................40
3.2.3. Signing Time .......................................40
4. Firmware Package Load Error ....................................41
4.1. Firmware Package Load Error CMS Content Type Profile ......42
4.1.1. ContentInfo ........................................42
4.1.2. SignedData .........................................43
4.1.2.1. SignerInfo ................................43
4.1.2.2. EncapsulatedContentInfo ...................43
4.1.3. FirmwarePackageLoadError ...........................43
4.2. Signed Attributes .........................................49
4.2.1. Content Type .......................................49
4.2.2. Message Digest .....................................49
4.2.3. Signing Time .......................................50
5. Hardware Module Name ...........................................50
6. Security Considerations ........................................51
6.1. Cryptographic Keys and Algorithms .........................51
6.2. Random Number Generation ..................................51
6.3. Stale Firmware Package Version Number .....................52
6.4. Community Identifiers .....................................53
7. References .....................................................54
7.1. Normative References ......................................54
7.2. Informative References ....................................54
Appendix A: ASN.1 Module ..........................................56
1. Introduction
This document describes the use of the Cryptographic Message Syntax
(CMS) [CMS] to protect firmware packages. This document also
describes the use of CMS for receipts and error reports for firmware
package loading. The CMS is a data protection encapsulation syntax
that makes use of ASN.1 [X.208-88, X.209-88]. The protected firmware
package can be associated with any particular hardware module;
however, this specification was written with the requirements of
cryptographic hardware modules in mind, as these modules have strong
security requirements.
The firmware package contains object code for one or more
programmable components that make up the hardware module. The
firmware package, which is treated as an opaque binary object, is
digitally signed. Optional encryption and compression are also
supported. When all three are used, the firmware package is
compressed, then encrypted, and then signed. Compression simply
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reduces the size of the firmware package, allowing more efficient
processing and transmission. Encryption protects the firmware
package from disclosure, which allows transmission of sensitive
firmware packages over insecure links. The encryption algorithm and
mode employed may also provide integrity, protecting the firmware
package from undetected modification. The encryption protects
proprietary algorithms, classified algorithms, trade secrets, and
implementation techniques. The digital signature protects the
firmware package from undetected modification and provides data
origin authentication. The digital signature allows the hardware
module to confirm that the firmware package comes from an acceptable
source.
If encryption is used, the firmware-decryption key must be made
available to the hardware module via a secure path. The key might be
delivered via physical media or via an independent electronic path.
One optional mechanism for distributing the firmware-decryption key
is specified in Section 2.3.1, but any secure key distribution
mechanism is acceptable.
The signature verification public key must be made available to the
hardware module in a manner that preserves its integrity and confirms
its source. CMS supports the transfer of certificates, and this
facility can be used to transfer a certificate that contains the
signature verification public key (a firmware-signing certificate).
However, use of this facility introduces a level of indirection.
Ultimately, a trust anchor public key must be made available to the
hardware module. Section 1.2 establishes a requirement that the
hardware module store one or more trust anchors.
Hardware modules may not be capable of accessing certificate
repositories or delegated path discovery (DPD) servers [DPD&DPV] to
acquire certificates needed to complete a certification path. Thus,
it is the responsibility of the firmware package signer to include
sufficient certificates to enable each module to validate the
firmware-signer certificate (see Section 2.1.2). Similarly, hardware
modules may not be capable of accessing a certificate revocation list
(CRL) repository, an OCSP responder [OCSP], or a delegated path
validation (DPV) server [DPD&DPV] to acquire revocation status
information. Thus, if the firmware package signature cannot be
validated solely with the trust anchor public key and the hardware
module is not capable of performing full certification path
validation, then it is the responsibility of the entity loading a
package into a hardware module to validate the firmware-signer
certification path prior to loading the package into a hardware
module. The means by which this external certificate revocation
status checking is performed is beyond the scope of this
specification.
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Hardware modules will only accept firmware packages with a valid
digital signature. The signature is either validated directly using
the trust anchor public key or using a firmware-signer certification
path that is validated to the trust anchor public key. Thus, the
trust anchors define the set of entities that can create firmware
packages for the hardware module.
The disposition of a previously loaded firmware package after the
successful validation of another firmware package is beyond the scope
of this specification. The amount of memory available to the
hardware module will determine the range of alternatives.
In some cases, hardware modules can generate receipts to acknowledge
the loading of a particular firmware package. Such receipts can be
used to determine which hardware modules need to receive an updated
firmware package whenever a flaw in an earlier firmware package is
discovered. Hardware modules can also generate error reports to
indicate the unsuccessful firmware package loading. To implement
either receipt or error report generation, the hardware module is
required to have a unique permanent serial number. Receipts and
error reports can be either signed or unsigned. To generate
digitally signed receipts or error reports, a hardware module MUST be
issued its own private signature key and a certificate that contains
the corresponding signature validation public key. In order to save
memory with the hardware module, the hardware module might store a
certificate designator instead of the certificate itself. The
private signature key requires secure storage.
1.1. Terminology
In this document, the key words MUST, MUST NOT, REQUIRED, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL are to be interpreted as
described in [STDWORDS].
1.2. Architectural Elements
The architecture includes the hardware module, the firmware package,
and a bootstrap loader. The bootstrap loader MUST have access to one
or more trusted public keys, called trust anchors, to validate the
signature on the firmware package. If a signed firmware package load
receipt or error report is created on behalf of the hardware module,
then the bootstrap loader MUST have access to a private signature key
to generate the signature and the signer identifier for the
corresponding signature validation certificate or its designator. A
signature validation certificate MAY be included to aid signature
validation. To implement this optional capability, the hardware
module MUST have a unique serial number and a private signature key;
the hardware module MAY also include a certificate that contains the
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corresponding signature validation public key. These items MUST be
installed in the hardware module before it is deployed. The private
key and certificate can be generated and installed as part of the
hardware module manufacture process. Figure 1 illustrates these
architectural elements.
ASN.1 object identifiers are the preferred means of naming the
architectural elements.
Details of managing the trust anchors are beyond the scope of this
specification. However, one or more trust anchors MUST be installed
in the hardware module using a secure process before it is deployed.
These trust anchors provide a means of controlling the acceptable
sources of firmware packages. The hardware module vendor can include
provisions for secure, remote management of trust anchors. One
approach is to include trust anchors in the firmware packages
themselves. This approach is analogous to the optional capability
described later for updating the bootstrap loader.
In a cryptographic hardware module, the firmware package might
implement many different cryptographic algorithms.
When the firmware package is encrypted, the firmware-decryption key
and the firmware package MUST both be provided to the hardware
module. The firmware-decryption key is necessary to use the
associated firmware package. Generally, separate distribution
mechanisms will be employed for the firmware-decryption key and the
firmware package. An optional mechanism for securely distributing
the firmware-decryption key with the firmware package is specified in
Section 2.3.1.
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+------------------------------------------------------+
| Hardware Module |
| |
| +---------------+ +--------------------------+ |
| | Bootstrap | | Firmware Package | |
| | Loader | | | |
| +---------------+ | +------------------+ | |
| | : Firmware Package : | |
| +---------------+ | : Identifier and : | |
| | Trust | | : Version Number : | |
| | Anchor(s) | | +------------------+ | |
| +---------------+ | | |
| | +-------------+ | |
| +---------------+ | : Algorithm 1 : | |
| | Serial Num. | | +-+-----------+-+ | |
| +---------------+ | : Algorithm 2 : | |
| | +-+-----------+-+ | |
| +---------------+ | : Algorithm n : | |
| | Hardware | | +-------------+ | |
| | Module Type | | | |
| +---------------+ +--------------------------+ |
| |
| +------------------------------------+ |
| | Optional Private Signature Key & | |
| | Signature Validation Certificate | |
| | or the Certificate Designator | |
| +------------------------------------+ |
| |
+------------------------------------------------------+
Figure 1. Architectural Elements
1.2.1. Hardware Module Requirements
Many different vendors develop hardware modules, and each vendor
typically identifies its modules by product type (family) and
revision level. A unique object identifier MUST name each hardware
module type and revision.
Each hardware module within a hardware module family SHOULD have a
unique permanent serial number. However, if the optional receipt or
error report generation capability is implemented, then the hardware
module MUST have a unique permanent serial number. If the optional
receipt or error report signature capability is implemented, then the
hardware module MUST have a private signature key and a certificate
containing the corresponding public signature validation key or its
designator. If a serial number is present, the bootstrap loader uses
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it for authorization decisions (see Section 2.2.8), receipt
generation (see Section 3), and error report generation (see
Section 4).
When the hardware module includes more than one firmware-programmable
component, the bootstrap loader distributes components of the package
to the appropriate components within the hardware module after the
firmware package is validated. The bootstrap loader is discussed
further in Section 1.2.3.
1.2.2. Firmware Package Requirements
Two approaches to naming firmware packages are supported: legacy and
preferred. Firmware package names are placed in a CMS signed
attribute, not in the firmware package itself.
Legacy firmware package names are simply octet strings, and no
structure is assumed. This firmware package name form is supported
in order to facilitate existing configuration management systems. We
assume that the firmware signer and the bootstrap loader will
understand any internal structure to the octet string. In
particular, given two legacy firmware package names, we assume that
the firmware signer and the bootstrap loader will be able to
determine which one represents the newer version of the firmware
package. This capability is necessary to implement the stale version
feature. If a firmware package with a disastrous flaw is released,
subsequent firmware package versions MAY designate a stale legacy
firmware package name in order to prevent subsequent rollback to the
stale version or versions earlier than the stale version.
Preferred firmware package names are a combination of the firmware
package object identifier and a version number. A unique object
identifier MUST identify the collection of features that characterize
the firmware package. For example, firmware packages for a cable
modem and a wireless LAN network interface card warrant distinct
object identifiers. Similarly, firmware packages that implement
distinct suites of cryptographic algorithms and modes of operation,
or that emulate different (non-programmable) cryptographic devices
warrant distinct object identifiers. The version number MUST
identify a particular build or release of the firmware package. The
version number MUST be a monotonically increasing non-negative
integer. Generally, an earlier version is replaced with a later one.
If a firmware package with a disastrous flaw is released, subsequent
firmware package versions MAY designate a stale version number to
prevent subsequent rollback to the stale version or versions earlier
than the stale version.
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Firmware packages are developed to run on one or more hardware module
type. The firmware package digital signature MUST bind the list of
supported hardware module object identifiers to the firmware package.
In many cases, the firmware package signature will be validated
directly with the trust anchor public key, avoiding the need to
construct certification paths. Alternatively, the trust anchor can
delegate firmware package signing to another public key through a
certification path. In the latter case, the firmware package SHOULD
contain the certificates needed to construct the certification path
that begins with a certificate issued by the trust anchors and ends
with a certificate issued to the firmware package signer.
The firmware package MAY contain a list of community identifiers.
These identifiers name the hardware modules that are authorized to
load the firmware package. If the firmware package contains a list
of community identifiers, then the bootstrap loader MUST reject the
firmware package if the hardware module is not a member of one of the
identified communities.
When a hardware module includes multiple programmable components, the
firmware package SHOULD contain executable code for all of the
components. Internal tagging within the firmware package MUST tell
the bootstrap loader which portion of the overall firmware package is
intended for each component; however, this tagging is expected to be
specific to each hardware module. Because this specification treats
the firmware package as an opaque binary object, the format of the
firmware package is beyond the scope of this specification.
1.2.3. Bootstrap Loader Requirements
The bootstrap loader MUST have access to a physical interface and any
related driver or protocol software necessary to obtain a firmware
package. The same interface SHOULD be used to deliver receipts and
error reports. Details of the physical interface as well as the
driver or protocol software are beyond the scope of this
specification.
The bootstrap loader can be a permanent part of the hardware module,
or it can be replaced by loading a firmware package. In Figure 1,
the bootstrap loader is implemented as separate logic within the
hardware module. Not all hardware modules will include the ability
to replace or update the bootstrap loader, and this specification
does not mandate such support.
If the bootstrap loader can be loaded by a firmware package, an
initial bootstrap loader MUST be installed in non-volatile memory
prior to deployment. All bootstrap loaders, including an initial
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bootstrap loader if one is employed, MUST meet the requirements in
this section. However, the firmware package containing the bootstrap
loader MAY also contain other routines.
The bootstrap loader requires access to cryptographic routines.
These routines can be implemented specifically for the bootstrap
loader, or they can be shared with other hardware module features.
The bootstrap loader MUST have access to a one-way hash function and
digital signature verification routines to validate the digital
signature on the firmware package and to validate the certification
path for the firmware-signing certificate.
If firmware packages are encrypted, the bootstrap loader MUST have
access to a decryption routine. Access to a corresponding encryption
function is not required, since hardware modules need not be capable
of generating firmware packages. Because some symmetric encryption
algorithm implementations (such as AES [AES]) employ separate logic
for encryption and decryption, some hardware module savings might
result.
If firmware packages are compressed, the bootstrap loader MUST also
have access to a decompression function. This function can be
implemented specifically for the bootstrap loader, or it can be
shared with other hardware module features. Access to a
corresponding compression function is not required, since hardware
modules need not be capable of generating firmware packages.
If the optional receipt generation or error report capability is
supported, the bootstrap loader MUST have access to the hardware
module serial number and the object identifier for the hardware
module type. If the optional signed receipt generation or signed
error report capability is supported, the bootstrap loader MUST also
have access to a one-way hash function and digital signature
routines, the hardware module private signing key, and the
corresponding signature validation certificate or its designator.
The bootstrap loader requires access to one or more trusted public
keys, called trust anchors, to validate the firmware package digital
signature. One or more trust anchors MUST be installed in non-
volatile memory prior to deployment. The bootstrap loader MUST
reject a firmware package if it cannot validate the signature, which
MAY require the construction of a valid certification path from the
firmware-signing certificate to one of the trust anchors [PROFILE].
However, in many cases, the firmware package signature will be
validated directly with the trust anchor public key, avoiding the
need to construct certification paths.
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The bootstrap loader MUST reject a firmware package if the list of
supported hardware module type identifiers within the firmware
package does not include the object identifier of the hardware
module.
The bootstrap loader MUST reject a firmware package if the firmware
package includes a list of community identifiers and the hardware
module is not a member of one of the listed communities. The means
of determining community membership is beyond the scope of this
specification.
The bootstrap loader MUST reject a firmware package if it cannot
successfully decrypt the firmware package using the firmware-
decryption key available to the hardware module. The firmware
package contains an identifier of the firmware-decryption key needed
for decryption.
When an earlier version of a firmware package is replacing a later
one, the bootstrap loader SHOULD generate a warning. The manner in
which a warning is generated is highly dependent on the hardware
module and the environment in which it is being used. If a firmware
package with a disastrous flaw is released and subsequent firmware
package versions designate a stale version, the bootstrap loader
SHOULD prevent loading of the stale version and versions earlier than
the stale version.
1.2.3.1. Legacy Stale Version Processing
In case a firmware package with a disastrous flaw is released,
subsequent firmware package versions that employ the legacy firmware
package name form MAY include a stale legacy firmware package name to
prevent subsequent rollback to the stale version or versions earlier
than the stale version. As described in the Security Considerations
section of this document, the inclusion of a stale legacy firmware
package name in a firmware package cannot completely prevent
subsequent use of the stale firmware package. However, many hardware
modules are expected to have very few firmware packages written for
them, allowing the stale firmware package version feature to provide
important protections.
Non-volatile storage for stale version numbers is needed. The number
of stale legacy firmware package names that can be stored depends on
the amount of storage that is available. When a firmware package is
loaded and it contains a stale legacy firmware package name, then it
SHOULD be added to a list kept in non-volatile storage. When
subsequent firmware packages are loaded, the legacy firmware package
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name of the new package is compared to the list in non-volatile
storage. If the legacy firmware package name represents the same
version or an older version of a member of the list, then the new
firmware packages SHOULD be rejected.
The amount of non-volatile storage that needs to be dedicated to
saving legacy firmware package names and stale legacy firmware
packages names depends on the number of firmware packages that are
likely to be developed for the hardware module.
1.2.3.2. Preferred Stale Version Processing
If a firmware package with a disastrous flaw is released, subsequent
firmware package versions that employ preferred firmware package name
form MAY include a stale version number to prevent subsequent
rollback to the stale version or versions earlier than the stale
version. As described in the Security Considerations section of this
document, the inclusion of a stale version number in a firmware
package cannot completely prevent subsequent use of the stale
firmware package. However, many hardware modules are expected to
have very few firmware packages written for them, allowing the stale
firmware package version feature to provide important protections.
Non-volatile storage for stale version numbers is needed. The number
of stale version numbers that can be stored depends on the amount of
storage that is available. When a firmware package is loaded and it
contains a stale version number, then the object identifier of the
firmware package and the stale version number SHOULD be added to a
list that is kept in non-volatile storage. When subsequent firmware
packages are loaded, the object identifier and version number of the
new package are compared to the list in non-volatile storage. If the
object identifier matches and the version number is less than or
equal to the stale version number, then the new firmware packages
SHOULD be rejected.
The amount of non-volatile storage that needs to be dedicated to
saving firmware package identifiers and stale version numbers depends
on the number of firmware packages that are likely to be developed
for the hardware module.
1.2.4. Trust Anchors
A trust anchor MUST consist of a public key signature algorithm and
an associated public key, which MAY optionally include parameters. A
trust anchor MUST also include a public key identifier. A trust
anchor MAY also include an X.500 distinguished name.
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The trust anchor public key is used in conjunction with the signature
validation algorithm in two different ways. First, the trust anchor
public key is used directly to validate the firmware package
signature. Second, the trust anchor public key is used to validate
an X.509 certification path, and then the subject public key in the
final certificate in the certification path is used to validate the
firmware package signature.
The public key names the trust anchor, and each public key has a
public key identifier. The public key identifier identifies the
trust anchor as the signer when it is used directly to validate
firmware package signatures. This key identifier can be stored with
the trust anchor, or it can be computed from the public key whenever
needed.
The optional trusted X.500 distinguished name MUST be present in
order for the trust anchor public key to be used to validate an X.509
certification path. Without an X.500 distinguished name,
certification path construction cannot use the trust anchor.
1.2.5. Cryptographic and Compression Algorithm Requirements
A firmware package for a cryptographic hardware module includes
cryptographic algorithm implementations. In addition, a firmware
package for a non-cryptographic hardware module will likely include
cryptographic algorithm implementations to support the bootstrap
loader in the validation of firmware packages.
A unique algorithm object identifier MUST be assigned for each
cryptographic algorithm and mode implemented by a firmware package.
A unique algorithm object identifier MUST also be assigned for each
compression algorithm implemented by a firmware package. The
algorithm object identifiers can be used to determine whether a
particular firmware package satisfies the needs of a particular
application. To facilitate the development of algorithm-agile
applications, the cryptographic module interface SHOULD allow
applications to query the cryptographic module for the object
identifiers associated with each cryptographic algorithm contained in
the currently loaded firmware package. Applications SHOULD also be
able to query the cryptographic module to determine attributes
associated with each algorithm. Such attributes might include the
algorithm type (symmetric encryption, asymmetric encryption, key
agreement, one-way hash function, digital signature, and so on), the
algorithm block size or modulus size, and parameters for asymmetric
algorithms. This specification does not establish the conventions
for the retrieval of algorithm identifiers or algorithm attributes.
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1.3. Hardware Module Security Architecture
The bootstrap loader MAY be permanently stored in read-only memory or
separately loaded into non-volatile memory as discussed above.
In most hardware module designs, the firmware package execution
environment offers a single address space. If it does, the firmware
package SHOULD contain a complete firmware package load for the
hardware module. In this situation, the firmware package does not
contain a partial or incremental set of functions. A complete
firmware package load will minimize complexity and avoid potential
security problems. From a complexity perspective, the incremental
loading of packages makes it necessary for each package to identify
any other packages that are required (its dependencies), and the
bootstrap loader needs to verify that all of the dependencies are
satisfied before attempting to execute the firmware package. When a
hardware module is based on a general purpose processor or a digital
signal processor, it is dangerous to allow arbitrary packages to be
loaded simultaneously unless there is a reference monitor to ensure
that independent portions of the code cannot interfere with one
another. Also, it is difficult to evaluate arbitrary combinations of
software modules [SECREQMTS]. For these reasons, a complete firmware
package load is RECOMMENDED; however, this specification allows the
firmware signer to identify dependencies between firmware packages in
order to handle all situations.
The firmware packages MAY have dependencies on routines provided by
other firmware packages. To minimize the security evaluation
complexity of a hardware module employing such a design, the firmware
package MUST identify the package identifiers (and the minimum
version numbers when the preferred firmware package name form is
used) of the packages upon which it depends. The bootstrap loader
MUST reject a firmware package load if it contains a dependency on a
firmware package that is not available.
Loading a firmware package can impact the satisfactory resolution of
dependencies of other firmware packages that are already part of the
hardware module configuration. For this reason, the bootstrap loader
MUST reject the loading of a firmware package if the dependencies of
any firmware package in the resulting configurations will be
unsatisfied.
1.4. ASN.1 Encoding
The CMS uses Abstract Syntax Notation One (ASN.1) [X.208-88,
X.209-88]. ASN.1 is a formal notation used for describing data
protocols, regardless of the programming language used by the
implementation. Encoding rules describe how the values defined in
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ASN.1 will be represented for transmission. The Basic Encoding Rules
(BER) are the most widely employed rule set, but they offer more than
one way to represent data structures. For example, definite length
encoding and indefinite length encoding are supported. This
flexibility is not desirable when digital signatures are used. As a
result, the Distinguished Encoding Rules (DER) [X.509-88] were
invented. DER is a subset of BER that ensures a single way to
represent a given value. For example, DER always employs definite
length encoding.
In this specification, digitally signed structures MUST be encoded
with DER. Other structures do not require DER, but the use of
definite length encoding is strongly RECOMMENDED. By always using
definite length encoding, the bootstrap loader will have fewer
options to implement. In situations where there is very high
confidence that only definite length encoding will be used, support
for indefinite length decoding MAY be omitted.
1.5. Protected Firmware Package Loading
This document does not attempt to specify a physical interface, any
related driver software, or a protocol necessary for loading firmware
packages. Many different delivery mechanisms are envisioned,
including portable memory devices, file transfer, and web pages.
Section 2 of this specification defines the format that MUST be
presented to the hardware module regardless of the interface that is
used. This specification also specifies the format of the response
that MAY be generated by the hardware module. Section 3 of this
specification defines the format that MAY be returned by the hardware
module when a firmware package loads successfully. Section 4 of this
specification defines the format that MAY be returned by the hardware
module when a firmware package load is unsuccessful. The firmware
package load receipts and firmware package load error reports can be
either signed or unsigned.
2. Firmware Package Protection
The Cryptographic Message Syntax (CMS) is used to protect a firmware
package, which is treated as an opaque binary object. A digital
signature is used to protect the firmware package from undetected
modification and to provide data origin authentication. Encryption
is optionally used to protect the firmware package from disclosure,
and compression is optionally used to reduce the size of the
protected firmware package. The CMS ContentInfo content type MUST
always be present, and it MUST encapsulate the CMS SignedData content
type. If the firmware package is encrypted, then the CMS SignedData
content type MUST encapsulate the CMS EncryptedData content type. If
the firmware package is compressed, then either the CMS SignedData
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
content type (when encryption is not used) or the CMS EncryptedData
content type (when encryption is used) MUST encapsulate the CMS
CompressedData content type. Finally, (1) the CMS SignedData content
type (when neither encryption nor compression is used), (2) the CMS
EncryptedData content type (when encryption is used, but compression
is not), or (3) the CMS CompressedData content type (when compression
is used) MUST encapsulate the simple firmware package using the
FirmwarePkgData content type defined in this specification (see
Section 2.1.5).
The firmware package protection is summarized as follows (see [CMS]
for the full syntax):
ContentInfo {
contentType id-signedData, -- (1.2.840.113549.1.7.2)
content SignedData
}
SignedData {
version CMSVersion, -- always set to 3
digestAlgorithms DigestAlgorithmIdentifiers, -- Only one
encapContentInfo EncapsulatedContentInfo,
certificates CertificateSet, -- Signer cert. path
crls CertificateRevocationLists, -- Optional
signerInfos SET OF SignerInfo -- Only one
}
SignerInfo {
version CMSVersion, -- always set to 3
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs SignedAttributes, -- Required
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs UnsignedAttributes -- Optional
}
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
EncapsulatedContentInfo {
eContentType id-encryptedData, -- (1.2.840.113549.1.7.6)
-- OR --
id-ct-compressedData,
-- (1.2.840.113549.1.9.16.1.9)
-- OR --
id-ct-firmwarePackage,
-- (1.2.840.113549.1.9.16.1.16)
eContent OCTET STRING
} -- Contains EncryptedData OR
-- CompressedData OR
-- FirmwarePkgData
EncryptedData {
version CMSVersion, -- Always set to 0
encryptedContentInfo EncryptedContentInfo,
unprotectedAttrs UnprotectedAttributes -- Omit
}
EncryptedContentInfo {
contentType id-ct-compressedData,
-- (1.2.840.113549.1.9.16.1.9)
-- OR --
id-ct-firmwarePackage,
-- (1.2.840.113549.1.9.16.1.16)
contentEncryptionAlgorithm ContentEncryptionAlgorithmIdentifier,
encryptedContent OCTET STRING
} -- Contains CompressedData OR
-- FirmwarePkgData
CompressedData {
version CMSVersion, -- Always set to 0
compressionAlgorithm CompressionAlgorithmIdentifier,
encapContentInfo EncapsulatedContentInfo
}
EncapsulatedContentInfo {
eContentType id-ct-firmwarePackage,
-- (1.2.840.113549.1.9.16.1.16)
eContent OCTET STRING -- Contains FirmwarePkgData
}
FirmwarePkgData OCTET STRING -- Contains firmware package
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
2.1. Firmware Package Protection CMS Content Type Profile
This section specifies the conventions for using the CMS ContentInfo,
SignedData, EncryptedData, and CompressedData content types. It also
defines the FirmwarePkgData content type.
2.1.1. ContentInfo
The CMS requires that the outermost encapsulation be ContentInfo
[CMS]. The fields of ContentInfo are used as follows:
contentType indicates the type of the associated content, and in
this case, the encapsulated type is always SignedData. The
id-signedData (1.2.840.113549.1.7.2) object identifier MUST be
present in this field.
content holds the associated content, and in this case, the
content field MUST contain SignedData.
2.1.2. SignedData
The SignedData content type [CMS] contains the signed firmware
package (which might be compressed, encrypted, or compressed and then
encrypted prior to signature), the certificates needed to validate
the signature, and one digital signature value. The fields of
SignedData are used as follows:
version is the syntax version number, and in this case, it MUST be
set to 3.
digestAlgorithms is a collection of message digest algorithm
identifiers, and in this case, it MUST contain a single message
digest algorithm identifier. The message digest algorithm
employed by the firmware package signer MUST be present.
encapContentInfo contains the signed content, consisting of a content
type identifier and the content itself. The use of the
EncapsulatedContentInfo type is discussed further in Section
2.1.2.2.
certificates is an optional collection of certificates. If the trust
anchor signed the firmware package directly, then certificates
SHOULD be omitted. If it did not, then certificates SHOULD
include the X.509 certificate of the firmware package signer. The
set of certificates SHOULD be sufficient for the bootstrap loader
to construct a certification path from the trust anchor to the
firmware-signer's certificate. PKCS#6 extended certificates
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
[PKCS#6] and attribute certificates (either version 1 or
version 2) [X.509-97, X.509-00, ACPROFILE] MUST NOT be included in
the set of certificates.
crls is an optional collection of certificate revocation lists
(CRLs), and in this case, CRLs SHOULD NOT be included by the
firmware package signer. It is anticipated that firmware packages
may be generated, signed, and made available in repositories for
downloading into hardware modules. In such contexts, it would be
difficult for the firmware package signer to include timely CRLs
in the firmware package. However, because the CRLs are not
covered by the signature, timely CRLs MAY be inserted by some
other party before the firmware package is delivered to the
hardware module.
signerInfos is a collection of per-signer information, and in this
case, the collection MUST contain exactly one SignerInfo. The use
of the SignerInfo type is discussed further in Section 2.1.2.1.
2.1.2.1. SignerInfo
The firmware package signer is represented in the SignerInfo type.
The fields of SignerInfo are used as follows:
version is the syntax version number, and it MUST be 3.
sid identifies the signer's public key. CMS supports two
alternatives: issuerAndSerialNumber and subjectKeyIdentifier.
However, the bootstrap loader MUST support the
subjectKeyIdentifier alternative, which identifies the signer's
public key directly. When this public key is contained in a
certificate, this identifier SHOULD appear in the X.509
subjectKeyIdentifier extension.
digestAlgorithm identifies the message digest algorithm, and any
associated parameters, used by the firmware package signer. It
MUST contain the message digest algorithms employed by the
firmware package signer. (Note that this message digest algorithm
identifier MUST be the same as the one carried in the
digestAlgorithms value in SignedData.)
signedAttrs is an optional collection of attributes that are signed
along with the content. The signedAttrs are optional in the CMS,
but in this specification, signedAttrs are REQUIRED for the
firmware package; however, implementations MUST ignore
unrecognized signed attributes. The SET OF attributes MUST be DER
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
encoded [X.509-88]. Section 2.2 of this document lists the
attributes that MUST be included in the collection; other
attributes MAY be included as well.
signatureAlgorithm identifies the signature algorithm, and any
associated parameters, used by the firmware package signer to
generate the digital signature.
signature is the digital signature value.
unsignedAttrs is an optional SET of attributes that are not signed.
As described in Section 2.3, this set can only contain a single
instance of the wrapped-firmware-decryption-key attribute and no
others.
2.1.2.2. EncapsulatedContentInfo
The EncapsulatedContentInfo content type encapsulates the firmware
package, which might be compressed, encrypted, or compressed and then
encrypted prior to signature. The firmware package, in any of these
formats, is carried within the EncapsulatedContentInfo type. The
fields of EncapsulatedContentInfo are used as follows:
eContentType is an object identifier that uniquely specifies the
content type, and in this case, the value MUST be id-encryptedData
(1.2.840.113549.1.7.6), id-ct-compressedData
(1.2.840.113549.1.9.16.1.9), or id-ct-firmwarePackage
(1.2.840.113549.1.9.16.1.16). When eContentType contains id-
encryptedData, the firmware package was encrypted prior to
signing, and may also have been compressed prior to encryption.
When it contains id-ct-compressedData, the firmware package was
compressed prior to signing, but was not encrypted. When it
contains id-ct-firmwarePackage, the firmware package was not
compressed or encrypted prior to signing.
eContent contains the signed firmware package, which might also be
encrypted, compressed, or compressed and then encrypted, prior to
signing. The content is encoded as an octet string. The eContent
octet string need not be DER encoded.
2.1.3. EncryptedData
The EncryptedData content type [CMS] contains the encrypted firmware
package (which might be compressed prior to encryption). However, if
the firmware package was not encrypted, the EncryptedData content
type is not present. The fields of EncryptedData are used as
follows:
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
version is the syntax version number, and in this case, version MUST
be 0.
encryptedContentInfo is the encrypted content information. The use
of the EncryptedContentInfo type is discussed further in Section
2.1.3.1.
unprotectedAttrs is an optional collection of unencrypted attributes,
and in this case, unprotectedAttrs MUST NOT be present.
2.1.3.1. EncryptedContentInfo
The encrypted firmware package, which might be compressed prior to
encryption, is encapsulated in the EncryptedContentInfo type. The
fields of EncryptedContentInfo are used as follows:
contentType indicates the type of content, and in this case, it MUST
contain either id-ct-compressedData (1.2.840.113549.1.9.16.1.9) or
id-ct-firmwarePackage (1.2.840.113549.1.9.16.1.16). When it
contains id-ct-compressedData, then the firmware package was
compressed prior to encryption. When it contains id-ct-
firmwarePackage, then the firmware package was not compressed
prior to encryption.
contentEncryptionAlgorithm identifies the firmware-encryption
algorithm, and any associated parameters, used to encrypt the
firmware package.
encryptedContent is the result of encrypting the firmware package.
The field is optional; however, in this case, it MUST be present.
2.1.4. CompressedData
The CompressedData content type [COMPRESS] contains the compressed
firmware package. If the firmware package was not compressed, then
the CompressedData content type is not present. The fields of
CompressedData are used as follows:
version is the syntax version number; in this case, it MUST be 0.
compressionAlgorithm identifies the compression algorithm, and any
associated parameters, used to compress the firmware package.
encapContentInfo is the compressed content, consisting of a content
type identifier and the content itself. The use of the
EncapsulatedContentInfo type is discussed further in Section
2.1.4.1.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
2.1.4.1. EncapsulatedContentInfo
The CompressedData content type encapsulates the compressed firmware
package, and it is carried within the EncapsulatedContentInfo type.
The fields of EncapsulatedContentInfo are used as follows:
eContentType is an object identifier that uniquely specifies the
content type, and in this case, it MUST be the value of id-ct-
firmwarePackage (1.2.840.113549.1.9.16.1.16).
eContent is the compressed firmware package, encoded as an octet
string. The eContent octet string need not be DER encoded.
2.1.5. FirmwarePkgData
The FirmwarePkgData content type contains the firmware package. It
is a straightforward encapsulation in an octet string, and it need
not be DER encoded.
The FirmwarePkgData content type is identified by the id-ct-
firmwarePackage object identifier:
id-ct-firmwarePackage OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 16 }
The FirmwarePkgData content type is a simple octet string:
FirmwarePkgData ::= OCTET STRING
2.2. Signed Attributes
The firmware package signer MUST digitally sign a collection of
attributes along with the firmware package. Each attribute in the
collection MUST be DER encoded [X.509-88]. The syntax for attributes
is defined in [CMS], but it is repeated here for convenience:
Attribute ::= SEQUENCE {
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue }
AttributeValue ::= ANY
Each of the attributes used with this profile has a single attribute
value, even though the syntax is defined as a SET OF AttributeValue.
There MUST be exactly one instance of AttributeValue present.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The SignedAttributes syntax within signerInfo is defined as a SET OF
Attribute. The SignedAttributes MUST include only one instance of
any particular attribute.
The firmware package signer MUST include the following four
attributes: content-type, message-digest, firmware-package-
identifier, and target-hardware-module-identifiers.
If the firmware package is encrypted, then the firmware package
signer MUST also include the decrypt-key-identifier attribute.
If the firmware package implements cryptographic algorithms, then the
firmware package signer MAY also include the implemented-crypto-
algorithms attribute. Similarly, if the firmware package implements
compression algorithms, then the firmware package signer MAY also
include the implemented-compress-algorithms attribute.
If the firmware package is intended for use only by specific
communities, then the firmware package signer MUST also include the
community-identifiers attribute.
If the firmware package depends on the presence of one or more other
firmware packages to operate properly, then the firmware package
signer SHOULD also include the firmware-package-info attribute. For
example, the firmware-package-info attribute dependencies field might
indicate that the firmware package contains a dependency on a
particular bootstrap loader or separation kernel.
The firmware package signer SHOULD also include the three following
attributes: firmware-package-message-digest, signing-time, and
content-hints. Additionally, if the firmware package signer has a
certificate (meaning that the firmware package signer is not always
configured as a trust anchor), then the firmware package signer
SHOULD also include the signing-certificate attribute.
The firmware package signer MAY include any other attribute that it
deems appropriate.
2.2.1. Content Type
The firmware package signer MUST include a content-type attribute
with the value of id-encryptedData (1.2.840.113549.1.7.6), id-ct-
compressedData (1.2.840.113549.1.9.16.1.9), or id-ct-firmwarePackage
(1.2.840.113549.1.9.16.1.16). When it contains id-encryptedData, the
firmware package was encrypted prior to signing. When it contains
id-ct-compressedData, the firmware package was compressed prior to
signing, but was not encrypted. When it contains
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
id-ct-firmwarePackage, the firmware package was not compressed or
encrypted prior to signing. Section 11.1 of [CMS] defines the
content-type attribute.
2.2.2. Message Digest
The firmware package signer MUST include a message-digest attribute,
having as its value the message digest computed on the
encapContentInfo eContent octet string, as defined in Section
2.1.2.2. This octet string contains the firmware package, and it MAY
be compressed, encrypted, or both compressed and encrypted. Section
11.2 of [CMS] defines the message-digest attribute.
2.2.3. Firmware Package Identifier
The firmware-package-identifier attribute names the protected
firmware package. Two approaches to naming firmware packages are
supported: legacy and preferred. The firmware package signer MUST
include a firmware-package-identifier attribute using one of these
name forms.
A legacy firmware package name is an octet string, and no structure
within the octet string is assumed.
A preferred firmware package name is a combination of an object
identifier and a version number. The object identifier names a
collection of functions implemented by the firmware package, and the
version number is a non-negative integer that identifies a particular
build or release of the firmware package.
If a firmware package with a disastrous flaw is released, the
firmware package that repairs the previously distributed flaw MAY
designate a stale firmware package version to prevent the reloading
of the flawed version. The hardware module bootstrap loader SHOULD
prevent subsequent rollback to the stale version or versions earlier
than the stale version. When the legacy firmware package name form
is used, the stale version is indicated by a stale legacy firmware
package name, which is an octet string. We assume that the firmware
package signer and the bootstrap loader can determine whether a given
legacy firmware package name represents a version that is more recent
than the stale one. When the preferred firmware package name form is
used, the stale version is indicated by a stale version number, which
is an integer.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The following object identifier identifies the firmware-package-
identifier attribute:
id-aa-firmwarePackageID OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 35 }
The firmware-package-identifier attribute values have ASN.1 type
FirmwarePackageIdentifier:
FirmwarePackageIdentifier ::= SEQUENCE {
name PreferredOrLegacyPackageIdentifier,
stale PreferredOrLegacyStalePackageIdentifier OPTIONAL }
PreferredOrLegacyPackageIdentifier ::= CHOICE {
preferred PreferredPackageIdentifier,
legacy OCTET STRING }
PreferredPackageIdentifier ::= SEQUENCE {
fwPkgID OBJECT IDENTIFIER,
verNum INTEGER (0..MAX) }
PreferredOrLegacyStalePackageIdentifier ::= CHOICE {
preferredStaleVerNum INTEGER (0..MAX),
legacyStaleVersion OCTET STRING }
2.2.4. Target Hardware Module Identifiers
The target-hardware-module-identifiers attribute names the types of
hardware modules that the firmware package supports. A unique object
identifier names each supported hardware model type and revision.
The bootstrap loader MUST reject the firmware package if its own
hardware module type identifier is not listed in the target-
hardware-module-identifiers attribute.
The following object identifier identifies the target-hardware-
module-identifiers attribute:
id-aa-targetHardwareIDs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 36 }
The target-hardware-module-identifiers attribute values have ASN.1
type TargetHardwareIdentifiers:
TargetHardwareIdentifiers ::= SEQUENCE OF OBJECT IDENTIFIER
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
2.2.5. Decrypt Key Identifier
The decrypt-key-identifier attribute names the symmetric key needed
to decrypt the encapsulated firmware package. The CMS EncryptedData
content type is used when the firmware package is encrypted. The
decrypt-key-identifier signed attribute is carried in the SignedData
content type that encapsulates EncryptedData content type, naming the
symmetric key needed to decrypt the firmware package. No particular
structure is imposed on the key identifier. The means by which the
firmware-decryption key is securely distributed to all modules that
are authorized to use the associated firmware package is beyond the
scope of this specification; however, an optional mechanism for
securely distributing the firmware-decryption key with the firmware
package is specified in Section 2.3.1.
The following object identifier identifies the decrypt-key-identifier
attribute:
id-aa-decryptKeyID OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 37 }
The decrypt-key-identifier attribute values have ASN.1 type
DecryptKeyIdentifier:
DecryptKeyIdentifier ::= OCTET STRING
2.2.6. Implemented Crypto Algorithms
The implemented-crypto-algorithms attribute MAY be present in the
SignedAttributes, and it names the cryptographic algorithms that are
implemented by the firmware package and available to applications.
Only those algorithms that are made available at the interface of the
cryptographic module are listed. Any cryptographic algorithm that is
used internally and is not accessible via the cryptographic module
interface MUST NOT be listed. For example, if the firmware package
implements the decryption algorithm for future firmware package
installations and this algorithm is not made available for other
uses, then the firmware-decryption algorithm would not be listed.
The object identifier portion of AlgorithmIdentifier identifies an
algorithm and its mode of use. No algorithm parameters are included.
Cryptographic algorithms include traffic-encryption algorithms, key-
encryption algorithms, key transport algorithms, key agreement
algorithms, one-way hash algorithms, and digital signature
algorithms. Cryptographic algorithms do not include compression
algorithms.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The following object identifier identifies the implemented-crypto-
algorithms attribute:
id-aa-implCryptoAlgs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 38 }
The implemented-crypto-algorithms attribute values have ASN.1 type
ImplementedCryptoAlgorithms:
ImplementedCryptoAlgorithms ::= SEQUENCE OF OBJECT IDENTIFIER
2.2.7. Implemented Compression Algorithms
The implemented-compress-algorithms attribute MAY be present in the
SignedAttributes, and it names the compression algorithms that are
implemented by the firmware package and available to applications.
Only those algorithms that are made available at the interface of the
hardware module are listed. Any compression algorithm that is used
internally and is not accessible via the hardware module interface
MUST NOT be listed. For example, if the firmware package implements
a decompression algorithm for future firmware package installations
and this algorithm is not made available for other uses, then the
firmware-decompression algorithm would not be listed.
The object identifier portion of AlgorithmIdentifier identifies a
compression algorithm. No algorithm parameters are included.
The following object identifier identifies the implemented-compress-
algorithms attribute:
id-aa-implCompressAlgs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 43 }
The implemented-compress-algorithms attribute values have ASN.1 type
ImplementedCompressAlgorithms:
ImplementedCompressAlgorithms ::= SEQUENCE OF OBJECT IDENTIFIER
2.2.8. Community Identifiers
If present in the SignedAttributes, the community-identifiers
attribute names the communities that are permitted to execute the
firmware package. The bootstrap loader MUST reject the firmware
package if the hardware module is not a member of one of the
identified communities. The means of assigning community membership
is beyond the scope of this specification.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The community-identifiers attributes names the authorized communities
by a list of community object identifiers, by a list of specific
hardware modules, or by a combination of the two lists. A specific
hardware module is specified by the combination of the hardware
module identifier (as defined in Section 2.2.4) and a serial number.
To facilitate compact representation of serial numbers, a contiguous
block can be specified by the lowest authorized serial number and the
highest authorized serial number. Alternatively, all of the serial
numbers associated with a hardware module family identifier can be
specified with the NULL value.
If the bootstrap loader does not have a mechanism for obtaining a
list of object identifiers that identify the communities to which the
hardware module is a member, then the bootstrap loader MUST behave as
though the list is empty. Similarly, if the bootstrap loader does
not have access to the hardware module serial number, then the
bootstrap loader MUST behave as though the hardware module is not
included on the list of authorized hardware modules.
The following object identifier identifies the community-identifiers
attribute:
id-aa-communityIdentifiers OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 40 }
The community-identifiers attribute values have ASN.1 type
CommunityIdentifiers:
CommunityIdentifiers ::= SEQUENCE OF CommunityIdentifier
CommunityIdentifier ::= CHOICE {
communityOID OBJECT IDENTIFIER,
hwModuleList HardwareModules }
HardwareModules ::= SEQUENCE {
hwType OBJECT IDENTIFIER,
hwSerialEntries SEQUENCE OF HardwareSerialEntry }
HardwareSerialEntry ::= CHOICE {
all NULL,
single OCTET STRING,
block SEQUENCE {
low OCTET STRING,
high OCTET STRING } }
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
2.2.9. Firmware Package Information
If a hardware module supports more than one type of firmware package,
then the firmware package signer SHOULD include the firmware-
package-info attribute with a populated fwPkgType field to identify
the firmware package type. This value can aid the bootstrap loader
in the correct placement of the firmware package within the hardware
module. The firmware package type is an INTEGER, and the meaning of
the integer value is specific to each hardware module. For example,
a hardware module could assign different integer values for a
bootstrap loader, a separation kernel, and an application.
Some hardware module architectures permit one firmware package to use
routines provided by another. If the firmware package contains a
dependency on another, then the firmware package signer SHOULD also
include the firmware-package-info attribute with a populated
dependencies field. If the firmware package does not depend on any
other firmware packages, then the firmware package signer MUST NOT
include the firmware-package-info attribute with a populated
dependencies field.
Firmware package dependencies are identified by the firmware package
identifier or by information contained in the firmware package
itself, and in either case the bootstrap loader ensures that the
dependencies are met. The bootstrap loader MUST reject a firmware
package load if it identifies a dependency on a firmware package that
is not already loaded. Also, the bootstrap loader MUST reject a
firmware package load if the action will result in a configuration
where the dependencies of an already loaded firmware package will no
longer be satisfied. As described in Section 2.2.3, two approaches
to naming firmware packages are supported: legacy and preferred.
When the legacy firmware package name form is used, the dependency is
indicated by a legacy firmware package name. We assume that the
firmware package signer and the bootstrap loader can determine
whether a given legacy firmware package name represents the named
version of an acceptable newer version. When the preferred firmware
package name form is used, an object identifier and an integer are
provided. The object identifier MUST exactly match the object
identifier portion of a preferred firmware package name associated
with a firmware package that is already loaded, and the integer MUST
be less than or equal to the integer portion of the preferred
firmware package name associated with the same firmware package.
That is, the dependency specifies the minimum value of the version
that is acceptable.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The following object identifier identifies the firmware-package-info
attribute:
id-aa-firmwarePackageInfo OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 42 }
The firmware-package-info attribute values have ASN.1 type
FirmwarePackageInfo:
FirmwarePackageInfo ::= SEQUENCE {
fwPkgType INTEGER OPTIONAL,
dependencies SEQUENCE OF
PreferredOrLegacyPackageIdentifier OPTIONAL }
2.2.10. Firmware Package Message Digest
The firmware package signer SHOULD include a firmware-package-
message-digest attribute, which provides the message digest algorithm
and the message digest value computed on the firmware package. The
message digest is computed on the firmware package prior to any
compression, encryption, or signature processing. The bootstrap
loader MAY use this message digest to confirm that the intended
firmware package has been recovered after all of the layers of
encapsulation are removed.
The following object identifier identifies the firmware-package-
message-digest attribute:
id-aa-fwPkgMessageDigest OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 41 }
The firmware-package-message-digest attribute values have ASN.1 type
FirmwarePackageMessageDigest:
FirmwarePackageMessageDigest ::= SEQUENCE {
algorithm AlgorithmIdentifier,
msgDigest OCTET STRING }
2.2.11. Signing Time
The firmware package signer SHOULD include a signing-time attribute,
specifying the time at which the signature was applied to the
firmware package. Section 11.3 of [CMS] defines the signing-time
attribute.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
2.2.12. Content Hints
The firmware package signer SHOULD include a content-hints attribute,
including a brief text description of the firmware package. The text
is encoded in UTF-8, which supports most of the world's writing
systems [UTF-8]. Section 2.9 of [ESS] defines the content-hints
attribute.
When multiple layers of encapsulation are employed, the content-hints
attribute is included in the outermost SignedData to provide
information about the innermost content. In this case, the content-
hints attribute provides a brief text description of the firmware
package, which can help a person select the correct firmware package
when more than one is available.
When the preferred firmware package name forms are used, the
content-hints attribute can provide a linkage to a legacy firmware
package name. This is especially helpful when an existing
configuration management system is in use, but the features
associated with the preferred firmware package name are deemed
useful. A firmware package name associated with such a configuration
management system might look something like
"R1234.C0(AJ11).D62.A02.11(b)." Including these firmware package
names in the text description may be helpful to developers by
providing a clear linkage between the two name forms.
The content-hints attribute contains two fields, and in this case,
both fields MUST be present. The fields of ContentHints are used as
follows:
contentDescription provides a brief text description of the firmware
package.
contentType provides the content type of the inner most content type,
and in this case, it MUST be id-ct-firmwarePackage
(1.2.840.113549.1.9.16.1.16).
2.2.13. Signing Certificate
When the firmware-signer's public key is contained in a certificate,
the firmware package signer SHOULD include a signing-certificate
attribute to identify the certificate that was employed. However, if
the firmware package signature does not have a certificate (meaning
that the signature will only be validated with the trust anchor
public key), then the firmware package signer is unable to include a
signing-certificate attribute. Section 5.4 of [ESS] defines this
attribute.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The signing-certificate attribute contains two fields: certs and
policies. The certs field MUST be present, and the policies field
MAY be present. The fields of SigningCertificate are used as
follows:
certs contains a sequence of certificate identifiers. In this case,
sequence of certificate identifiers contains a single entry. The
certs field MUST contain only the certificate identifier of the
certificate that contains the public key used to verify the
firmware package signature. The certs field uses the ESSCertID
syntax specified in Section 5.4 of [ESS], and it is comprised of
the SHA-1 hash [SHA1] of the entire ASN.1 DER encoded certificate
and, optionally, the certificate issuer and the certificate serial
number. The SHA-1 hash value MUST be present. The certificate
issuer and the certificate serial number SHOULD be present.
policies is optional; when it is present, it contains a sequence of
policy information. The policies field, when present, MUST
contain only one entry, and that entry MUST match one of the
certificate policies in the certificate policies extension of the
certificate that contains the public key used to verify the
firmware package signature. The policies field uses the
PolicyInformation syntax specified in Section 4.2.1.5 of
[PROFILE], and it is comprised of the certificate policy object
identifier and, optionally, certificate policy qualifiers. The
certificate policy object identifier MUST be present. The
certificate policy qualifiers SHOULD NOT be present.
2.3. Unsigned Attributes
CMS allows a SET of unsigned attributes to be included; however, in
this specification, the set MUST be absent or include a single
instance of the wrapped-firmware-decryption-key attribute. Because
the digital signature does not cover this attribute, it can be
altered at any point in the delivery path from the firmware package
signer to the hardware module. This property can be employed to
distribute the firmware-decryption key along with an encrypted and
signed firmware package, allowing the firmware-decryption key to be
wrapped with a different key-encryption key for each link in the
distribution chain.
The syntax for attributes is defined in [CMS], and it is repeated at
the beginning of Section 2.2 of this document for convenience. Each
of the attributes used with this profile has a single attribute
value, even though the syntax is defined as a SET OF AttributeValue.
There MUST be exactly one instance of AttributeValue present.
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The UnsignedAttributes syntax within signerInfo is defined as a SET
OF Attribute. The UnsignedAttributes MUST include only one instance
of any particular attribute.
2.3.1. Wrapped Firmware Decryption Key
The firmware package signer, or any other party in the distribution
chain, MAY include a wrapped-firmware-decryption-key attribute.
The following object identifier identifies the wrapped-firmware-
decryption-key attribute:
id-aa-wrappedFirmwareKey OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 39 }
The wrapped-firmware-decryption-key attribute values have ASN.1 type
of EnvelopedData. Section 6 of [CMS] defines the EnvelopedData
content type, which is used to construct the value of the attribute.
EnvelopedData permits the firmware-decryption key to be protected
using symmetric or asymmetric techniques. The EnvelopedData does not
include an encrypted content; rather, the EnvelopedData feature of
having the encrypted content in another location is employed. The
encrypted content is found in the eContent field of the EncryptedData
structure. The firmware-decryption key is contained in the
recipientInfos field. Section 6 of [CMS] refers to this key as the
content-encryption key.
The EnvelopedData syntax supports many different key management
algorithms. Four general techniques are supported: key transport,
key agreement, symmetric key-encryption keys, and passwords.
The EnvelopedData content type is profiled for the wrapped-firmware-
decryption-key attribute. The EnvelopedData fields are described
fully in Section 6 of [CMS]. Additional rules apply when
EnvelopedData is used as a wrapped-firmware-decryption-key attribute.
Within the EnvelopedData structure, the following apply:
- The set of certificates included in OriginatorInfo MUST NOT
include certificates with a type of extendedCertificate,
v1AttrCert, or v2AttrCert [X.509-97, X.509-00, ACPROFILE]. The
optional crls field MAY be present.
- The optional unprotectedAttrs field MUST NOT be present.
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Within the EncryptedContentInfo structure, the following apply:
- contentType MUST match the content type object identifier carried
in the contentType field within the EncryptedContentInfo structure
of EncryptedData as described in Section 2.1.3.1.
- contentEncryptionAlgorithm identifies the firmware-encryption
algorithm, and any associated parameters, used to encrypt the
firmware package carried in the encryptedContent field of the
EncryptedContentInfo structure of EncryptedData. Therefore, it
MUST exactly match the value of the EncryptedContentInfo structure
of EncryptedData as described in Section 2.1.3.1.
- encryptedContent is optional, and in this case, it MUST NOT be
present.
3. Firmware Package Load Receipt
The Cryptographic Message Syntax (CMS) is used to indicate that a
firmware package loaded successfully. Support for firmware package
load receipts is OPTIONAL. However, those hardware modules that
choose to generate such receipts MUST follow the conventions
specified in this section. Because not all hardware modules will
have private signature keys, the firmware package load receipt can be
either signed or unsigned. Use of the signed firmware package load
receipt is RECOMMENDED.
Hardware modules that support receipt generation MUST have a unique
serial number. Hardware modules that support signed receipt
generation MUST have a private signature key to sign the receipt and
the corresponding signature validation certificate or its designator.
The designator is the certificate issuer name and the certificate
serial number, or it is the public key identifier. Memory-
constrained hardware modules will generally store the public key
identifier since it requires less storage.
The unsigned firmware package load receipt is encapsulated by
ContentInfo. Alternatively, the signed firmware package load receipt
is encapsulated by SignedData, which is in turn encapsulated by
ContentInfo.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The firmware package load receipt is summarized as follows (see [CMS]
for the full syntax):
ContentInfo {
contentType id-signedData, -- (1.2.840.113549.1.7.2)
-- OR --
id-ct-firmwareLoadReceipt,
-- (1.2.840.113549.1.9.16.1.17)
content SignedData
-- OR --
FirmwarePackageLoadReceipt
}
SignedData {
version CMSVersion, -- always set to 3
digestAlgorithms DigestAlgorithmIdentifiers, -- Only one
encapContentInfo EncapsulatedContentInfo,
certificates CertificateSet, -- Optional Module certificate
crls CertificateRevocationLists, -- Optional
signerInfos SET OF SignerInfo -- Only one
}
SignerInfo {
version CMSVersion, -- either set to 1 or 3
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs SignedAttributes, -- Required
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs UnsignedAttributes -- Omit
}
EncapsulatedContentInfo {
eContentType id-ct-firmwareLoadReceipt,
-- (1.2.840.113549.1.9.16.1.17)
eContent OCTET STRING -- Contains receipt
}
FirmwarePackageLoadReceipt {
version INTEGER, -- The DEFAULT is always used
hwType OBJECT IDENTIFIER, -- Hardware module type
hwSerialNum OCTET STRING, -- H/W module serial number
fwPkgName PreferredOrLegacyPackageIdentifier,
trustAnchorKeyID OCTET STRING, -- Optional
decryptKeyID OCTET STRING -- Optional
}
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
3.1. Firmware Package Load Receipt CMS Content Type Profile
This section specifies the conventions for using the CMS ContentInfo
and SignedData content types for firmware package load receipts. It
also defines the firmware package load receipt content type.
3.1.1. ContentInfo
The CMS requires that the outermost encapsulation be ContentInfo
[CMS]. The fields of ContentInfo are used as follows:
contentType indicates the type of the associated content. If the
firmware package load receipt is signed, then the encapsulated
type MUST be SignedData, and the id-signedData
(1.2.840.113549.1.7.2) object identifier MUST be present in this
field. If the receipt is not signed, then the encapsulated type
MUST be FirmwarePackageLoadReceipt, and the id-ct-
firmwareLoadReceipt (1.2.840.113549.1.9.16.1.17) object identifier
MUST be present in this field.
content holds the associated content. If the firmware package load
receipt is signed, then this field MUST contain the SignedData.
If the receipt is not signed, then this field MUST contain the
FirmwarePackageLoadReceipt.
3.1.2. SignedData
The SignedData content type contains the firmware package load
receipt and one digital signature. If the hardware module locally
stores its certificate, then the certificate can be included as well.
The fields of SignedData are used as follows:
version is the syntax version number, and in this case, it MUST be
set to 3.
digestAlgorithms is a collection of message digest algorithm
identifiers, and in this case, it MUST contain a single message
digest algorithm identifier. The message digest algorithms
employed by the hardware module MUST be present.
encapContentInfo is the signed content, consisting of a content type
identifier and the content itself. The use of the
EncapsulatedContentInfo type is discussed further in Section
3.1.2.2.
certificates is an optional collection of certificates. If the
hardware module locally stores its certificate, then the X.509
certificate of the hardware module SHOULD be included. If the
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
hardware module does not, then the certificates field is omitted.
PKCS#6 extended certificates [PKCS#6] and attribute certificates
(either version 1 or version 2) [X.509-97, X.509-00, ACPROFILE]
MUST NOT be included in the set of certificates.
crls is an optional collection of certificate revocation lists
(CRLs). CRLs MAY be included, but they will normally be omitted
since hardware modules will not generally have access to the most
recent CRL. Signed receipt recipients SHOULD be able to handle
the presence of the optional crls field.
signerInfos is a collection of per-signer information, and in this
case, the collection MUST contain exactly one SignerInfo. The use
of the SignerInfo type is discussed further in Section 3.1.2.1.
3.1.2.1. SignerInfo
The hardware module is represented in the SignerInfo type. The
fields of SignerInfo are used as follows:
version is the syntax version number, and it MUST be either 1 or 3,
depending on the method used to identify the hardware module's
public key. The use of the subjectKeyIdentifier is RECOMMENDED,
which results in the use of version 3.
sid specifies the hardware module's certificate (and thereby the
hardware module's public key). CMS supports two alternatives:
issuerAndSerialNumber and subjectKeyIdentifier. The hardware
module MUST support one or both of the alternatives for receipt
generation; however, the support of subjectKeyIdentifier is
RECOMMENDED. The issuerAndSerialNumber alternative identifies the
hardware module's certificate by the issuer's distinguished name
and the certificate serial number. The identified certificate, in
turn, contains the hardware module's public key. The
subjectKeyIdentifier alternative identifies the hardware module's
public key directly. When this public key is contained in a
certificate, this identifier SHOULD appear in the X.509
subjectKeyIdentifier extension.
digestAlgorithm identifies the message digest algorithm, and any
associated parameters, used by the hardware module. It MUST
contain the message digest algorithms employed to sign the
receipt. (Note that this message digest algorithm identifier MUST
be the same as the one carried in the digestAlgorithms value in
SignedData.)
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
signedAttrs is an optional collection of attributes that are signed
along with the content. The signedAttrs are optional in the CMS,
but in this specification, signedAttrs are REQUIRED for use with
the firmware package load receipt content. The SET OF attributes
MUST be DER encoded [X.509-88]. Section 3.2 of this document
lists the attributes that MUST be included in the collection.
Other attributes MAY be included, but the recipient will ignore
any unrecognized signed attributes.
signatureAlgorithm identifies the signature algorithm, and any
associated parameters, used to sign the receipt.
signature is the digital signature.
unsignedAttrs is an optional collection of attributes that are not
signed, and in this case, there MUST NOT be any unsigned
attributes present.
3.1.2.2. EncapsulatedContentInfo
The FirmwarePackageLoadReceipt is encapsulated in an OCTET STRING,
and it is carried within the EncapsulatedContentInfo type. The
fields of EncapsulatedContentInfo are used as follows:
eContentType is an object identifier that uniquely specifies the
content type, and in this case, it MUST be the value of id-ct-
firmwareLoadReceipt (1.2.840.113549.1.9.16.1.17).
eContent is the firmware package load receipt, encapsulated in an
OCTET STRING. The eContent octet string need not be DER encoded.
3.1.3. FirmwarePackageLoadReceipt
The following object identifier identifies the firmware package load
receipt content type:
id-ct-firmwareLoadReceipt OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 17 }
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The firmware package load receipt content type has the ASN.1 type
FirmwarePackageLoadReceipt:
FirmwarePackageLoadReceipt ::= SEQUENCE {
version FWReceiptVersion DEFAULT v1,
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING,
fwPkgName PreferredOrLegacyPackageIdentifier,
trustAnchorKeyID OCTET STRING OPTIONAL,
decryptKeyID [1] OCTET STRING OPTIONAL }
FWReceiptVersion ::= INTEGER { v1(1) }
The fields of the FirmwarePackageLoadReceipt type have the following
meanings:
version is an integer that provides the syntax version number for
compatibility with future revisions of this specification.
Implementations that conform to this specification MUST set the
version to the default value, which is v1.
hwType is an object identifier that identifies the type of hardware
module on which the firmware package was loaded.
hwSerialNum is the serial number of the hardware module on which the
firmware package was loaded. No particular structure is imposed
on the serial number; it need not be an integer. However, the
combination of the hwType and hwSerialNum uniquely identifies the
hardware module.
fwPkgName identifies the firmware package that was loaded. As
described in Section 2.2.3, two approaches to naming firmware
packages are supported: legacy and preferred. A legacy firmware
package name is an octet string. A preferred firmware package
name is a combination of the firmware package object identifier
and an integer version number.
trustAnchorKeyID is optional, and when it is present, it identifies
the trust anchor that was used to validate the firmware package
signature.
decryptKeyID is optional, and when it is present, it identifies the
firmware-decryption key that was used to decrypt the firmware
package.
The firmware package load receipt MUST include the version, hwType,
hwSerialNum, and fwPkgName fields, and it SHOULD include the
trustAnchorKeyID field. The firmware package load receipt MUST NOT
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
include the decryptKeyID, unless the firmware package associated with
the receipt is encrypted, the firmware-decryption key is available to
the hardware module, and the firmware package was successfully
decrypted.
3.2. Signed Attributes
The hardware module MUST digitally sign a collection of attributes
along with the firmware package load receipt. Each attribute in the
collection MUST be DER encoded [X.509-88]. The syntax for attributes
is defined in [CMS], and it was repeated in Section 2.2 for
convenience.
Each of the attributes used with this profile has a single attribute
value, even though the syntax is defined as a SET OF AttributeValue.
There MUST be exactly one instance of AttributeValue present.
The SignedAttributes syntax within signerInfo is defined as a SET OF
Attributes. The SignedAttributes MUST include only one instance of
any particular attribute.
The hardware module MUST include the content-type and message-digest
attributes. If the hardware module includes a real-time clock, then
the hardware module SHOULD also include the signing-time attribute.
The hardware module MAY include any other attribute that it deems
appropriate.
3.2.1. Content Type
The hardware module MUST include a content-type attribute with the
value of id-ct-firmwareLoadReceipt (1.2.840.113549.1.9.16.1.17).
Section 11.1 of [CMS] defines the content-type attribute.
3.2.2. Message Digest
The hardware module MUST include a message-digest attribute, having
as its value the message digest of the FirmwarePackageLoadReceipt
content. Section 11.2 of [CMS] defines the message-digest attribute.
3.2.3. Signing Time
If the hardware module includes a real-time clock, then the hardware
module SHOULD include a signing-time attribute, specifying the time
at which the receipt was generated. Section 11.3 of [CMS] defines
the signing-time attribute.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
4. Firmware Package Load Error
The Cryptographic Message Syntax (CMS) is used to indicate that an
error has occurred while attempting to load a protected firmware
package. Support for firmware package load error reports is
OPTIONAL. However, those hardware modules that choose to generate
such error reports MUST follow the conventions specified in this
section. Not all hardware modules have private signature keys;
therefore the firmware package load error report can be either signed
or unsigned. Use of the signed firmware package error report is
RECOMMENDED.
Hardware modules that support error report generation MUST have a
unique serial number. Hardware modules that support signed error
report generation MUST also have a private signature key to sign the
error report and the corresponding signature validation certificate
or its designator. The designator is the certificate issuer name and
the certificate serial number, or it is the public key identifier.
Memory-constrained hardware modules will generally store the public
key identifier since it requires less storage.
The unsigned firmware package load error report is encapsulated by
ContentInfo. Alternatively, the signed firmware package load error
report is encapsulated by SignedData, which is in turn encapsulated
by ContentInfo.
The firmware package load error report is summarized as follows (see
[CMS] for the full syntax):
ContentInfo {
contentType id-signedData, -- (1.2.840.113549.1.7.2)
-- OR --
id-ct-firmwareLoadError,
-- (1.2.840.113549.1.9.16.1.18)
content SignedData
-- OR --
FirmwarePackageLoadError
}
SignedData {
version CMSVersion, -- Always set to 3
digestAlgorithms DigestAlgorithmIdentifiers, -- Only one
encapContentInfo EncapsulatedContentInfo,
certificates CertificateSet, -- Optional Module certificate
crls CertificateRevocationLists, -- Optional
signerInfos SET OF SignerInfo -- Only one
}
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
SignerInfo {
version CMSVersion, -- either set to 1 or 3
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs SignedAttributes, -- Required
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs UnsignedAttributes -- Omit
}
EncapsulatedContentInfo {
eContentType id-ct-firmwareLoadError,
-- (1.2.840.113549.1.9.16.1.18)
eContent OCTET STRING -- Contains error report
}
FirmwarePackageLoadError {
version INTEGER, -- The DEFAULT is always used
hwType OBJECT IDENTIFIER, -- Hardware module type
hwSerialNum OCTET STRING, -- H/W module serial number
errorCode FirmwarePackageLoadErrorCode -- Error identifier
vendorErrorCode VendorErrorCode, -- Optional
fwPkgName PreferredOrLegacyPackageIdentifier, -- Optional
config SEQUENCE OF CurrentFWConfig, -- Optional
}
CurrentFWConfig { -- Repeated for each package in configuration
fwPkgType INTEGER, -- Firmware package type; Optional
fwPkgName PreferredOrLegacyPackageIdentifier
}
4.1. Firmware Package Load Error CMS Content Type Profile
This section specifies the conventions for using the CMS ContentInfo
and SignedData content types for firmware package load error reports.
It also defines the firmware package load error content type.
4.1.1. ContentInfo
The CMS requires that the outermost encapsulation be ContentInfo
[CMS]. The fields of ContentInfo are used as follows:
contentType indicates the type of the associated content. If the
firmware package load error report is signed, then the
encapsulated type MUST be SignedData, and the id-signedData
(1.2.840.113549.1.7.2) object identifier MUST be present in this
field. If the report is not signed, then the encapsulated type
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
MUST be FirmwarePackageLoadError, and the id-ct-firmwareLoadError
(1.2.840.113549.1.9.16.1.18) object identifier MUST be present in
this field.
content holds the associated content. If the firmware package load
error report is signed, then this field MUST contain the
SignedData. If the report is not signed, then this field MUST
contain the FirmwarePackageLoadError.
4.1.2. SignedData
The SignedData content type contains the firmware package load error
report and one digital signature. If the hardware module locally
stores its certificate, then the certificate can be included as well.
The fields of SignedData are used exactly as described in Section
3.1.2.
4.1.2.1. SignerInfo
The hardware module is represented in the SignerInfo type. The
fields of SignerInfo are used exactly as described in Section
3.1.2.1.
4.1.2.2. EncapsulatedContentInfo
The FirmwarePackageLoadError is encapsulated in an OCTET STRING, and
it is carried within the EncapsulatedContentInfo type. The fields of
EncapsulatedContentInfo are used as follows:
eContentType is an object identifier that uniquely specifies the
content type, and in this case, it MUST be the value of id-ct-
firmwareLoadError (1.2.840.113549.1.9.16.1.18).
eContent is the firmware package load error report, encapsulated in
an OCTET STRING. The eContent octet string need not be DER
encoded.
4.1.3. FirmwarePackageLoadError
The following object identifier identifies the firmware package load
error report content type:
id-ct-firmwareLoadError OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 18 }
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The firmware package load error report content type has the ASN.1
type FirmwarePackageLoadError:
FirmwarePackageLoadError ::= SEQUENCE {
version FWErrorVersion DEFAULT v1,
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING,
errorCode FirmwarePackageLoadErrorCode,
vendorErrorCode VendorLoadErrorCode OPTIONAL,
fwPkgName PreferredOrLegacyPackageIdentifier OPTIONAL,
config [1] SEQUENCE OF CurrentFWConfig OPTIONAL }
FWErrorVersion ::= INTEGER { v1(1) }
CurrentFWConfig ::= SEQUENCE {
fwPkgType INTEGER OPTIONAL,
fwPkgName PreferredOrLegacyPackageIdentifier }
FirmwarePackageLoadErrorCode ::= ENUMERATED {
decodeFailure (1),
badContentInfo (2),
badSignedData (3),
badEncapContent (4),
badCertificate (5),
badSignerInfo (6),
badSignedAttrs (7),
badUnsignedAttrs (8),
missingContent (9),
noTrustAnchor (10),
notAuthorized (11),
badDigestAlgorithm (12),
badSignatureAlgorithm (13),
unsupportedKeySize (14),
signatureFailure (15),
contentTypeMismatch (16),
badEncryptedData (17),
unprotectedAttrsPresent (18),
badEncryptContent (19),
badEncryptAlgorithm (20),
missingCiphertext (21),
noDecryptKey (22),
decryptFailure (23),
badCompressAlgorithm (24),
missingCompressedContent (25),
decompressFailure (26),
wrongHardware (27),
stalePackage (28),
notInCommunity (29),
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
unsupportedPackageType (30),
missingDependency (31),
wrongDependencyVersion (32),
insufficientMemory (33),
badFirmware (34),
unsupportedParameters (35),
breaksDependency (36),
otherError (99) }
VendorLoadErrorCode ::= INTEGER
The fields of the FirmwarePackageLoadError type have the following
meanings:
version is an integer, and it provides the syntax version number for
compatibility with future revisions of this specification.
Implementations that conform to this specification MUST set the
version to the default value, which is v1.
hwType is an object identifier that identifies the type of hardware
module on which the firmware package load was attempted.
hwSerialNum is the serial number of the hardware module on which the
firmware package load was attempted. No particular structure is
imposed on the serial number; it need not be an integer. However,
the combination of the hwType and hwSerialNum uniquely identifies
the hardware module.
errorCode identifies the error that occurred.
vendorErrorCode is optional; however, it MUST be present if the
errorCode contains a value of otherError. When errorCode contains
a value other than otherError, the vendorErrorCode can provide
vendor-specific supplemental information.
fwPkgName is optional. When it is present, it identifies the
firmware package that was being loaded when the error occurred.
As described in Section 2.2.3, two approaches to naming firmware
packages are supported: legacy and preferred. A legacy firmware
package name is an octet string. A preferred firmware package
name is a combination of the firmware package object identifier
and an integer version number.
config identifies the current firmware configuration. The field is
OPTIONAL, but support for this field is RECOMMENDED for hardware
modules that permit the loading of more than one firmware package.
One instance of CurrentFWConfig is used to provide information
about each firmware package in hardware module.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
The fields of the CurrentFWConfig type have the following meanings:
fwPkgType identifies the firmware package type. The firmware package
type is an INTEGER, and the meaning of the integer value is
specific to each hardware module.
fwPkgName identifies the firmware package. As described in Section
2.2.3, two approaches to naming firmware packages are supported:
legacy and preferred. A legacy firmware package name is an octet
string. A preferred firmware package name is a combination of the
firmware package object identifier and an integer version number.
The errorCode values have the following meanings:
decodeFailure: The ASN.1 decode of the firmware package load failed.
The provided input did not conform to BER, or it was not ASN.1 at
all.
badContentInfo: Invalid ContentInfo syntax, or the contentType
carried within the ContentInfo is unknown or unsupported.
badSignedData: Invalid SignedData syntax, the version is unknown or
unsupported, or more than one entry is present in
digestAlgorithms.
badEncapContent: Invalid EncapsulatedContentInfo syntax, or the
contentType carried within the eContentType is unknown or
unsupported. This error can be generated due to problems located
in SignedData or CompressedData.
badCertificate: Invalid syntax for one or more certificates in
CertificateSet.
badSignerInfo: Invalid SignerInfo syntax, or the version is unknown
or unsupported.
badSignedAttrs: Invalid signedAttrs syntax within SignerInfo.
badUnsignedAttrs: The unsignedAttrs within SignerInfo contains an
attribute other than the wrapped-firmware-decryption-key
attribute, which is the only unsigned attribute supported by this
specification.
missingContent: The optional eContent is missing in
EncapsulatedContentInfo, which is required in this specification.
This error can be generated due to problems located in SignedData
or CompressedData.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
noTrustAnchor: Two situations can lead to this error. In one case,
the subjectKeyIdentifier does not identify the public key of a
trust anchor or a certification path that terminates with an
installed trust anchor. In the other case, the
issuerAndSerialNumber does not identify the public key of a trust
anchor or a certification path that terminates with an installed
trust anchor.
notAuthorized: The sid within SignerInfo leads to an installed trust
anchor, but that trust anchor is not an authorized firmware
package signer.
badDigestAlgorithm: The digestAlgorithm in either SignerInfo or
SignedData is unknown or unsupported.
badSignatureAlgorithm: The signatureAlgorithm in SignerInfo is
unknown or unsupported.
unsupportedKeySize: The signatureAlgorithm in SignerInfo is known and
supported, but the firmware package signature could not be
validated because an unsupported key size was employed by the
signer.
signatureFailure: The signatureAlgorithm in SignerInfo is known and
supported, but the signature in signature in SignerInfo could not
be validated.
contentTypeMismatch: The contentType carried within the eContentType
does not match the content type carried in the signed attribute.
badEncryptedData: Invalid EncryptedData syntax; the version is
unknown or unsupported.
unprotectedAttrsPresent: EncryptedData contains unprotectedAttrs,
which are not permitted in this specification.
badEncryptContent: Invalid EncryptedContentInfo syntax, or the
contentType carried within the contentType is unknown or
unsupported.
badEncryptAlgorithm: The firmware-encryption algorithm identified by
contentEncryptionAlgorithm in EncryptedContentInfo is unknown or
unsupported.
missingCiphertext: The optional encryptedContent is missing in
EncryptedContentInfo, which is required in this specification.
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noDecryptKey: The hardware module does not have the firmware-
decryption key named in the decrypt key identifier signed
attribute.
decryptFailure: The firmware package did not decrypt properly.
badCompressAlgorithm: The compression algorithm identified by
compressionAlgorithm in CompressedData is unknown or unsupported.
missingCompressedContent: The optional eContent is missing in
EncapsulatedContentInfo, which is required in this specification.
decompressFailure: The firmware package did not decompress properly.
wrongHardware: The processing hardware module is not listed in the
target hardware module identifiers signed attribute.
stalePackage: The firmware package is rejected because it is stale.
notInCommunity: The hardware module is not a member of the community
described in the community identifiers signed attribute.
unsupportedPackageType: The firmware package type identified in the
firmware package information signed attribute is not supported by
the combination of the hardware module and the bootstrap loader.
missingDependency: The firmware package being loaded depends on
routines that are part of another firmware package, but that
firmware package is not available.
wrongDependencyVersion: The firmware package being loaded depends on
routines that are part of the another firmware package, and the
available version of that package has an older version number than
is required. The available firmware package does not fulfill the
dependencies.
insufficientMemory: The firmware package could not be loaded because
the hardware module did not have sufficient memory.
badFirmware: The signature on the firmware package was validated, but
the firmware package itself was not in an acceptable format. The
details will be specific to each hardware module. For example, a
hardware module that is composed of multiple firmware-programmable
components could not find the internal tagging within the firmware
package to distribute executable code to each of the components.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
unsupportedParameters: The signature on the firmware package could
not be validated because the signer used signature algorithm
parameters that are not supported by the hardware module signature
verification routines.
breaksDependency: Another firmware package has a dependency that can
no longer be satisfied if the firmware package being loaded is
accepted.
otherError: An error occurred that does not fit any of the previous
error codes.
4.2. Signed Attributes
The hardware module MUST digitally sign a collection of attributes
along with the firmware package load error report. Each attribute in
the collection MUST be DER encoded [X.509-88]. The syntax for
attributes is defined in [CMS], and it was repeated in Section 2.2
for convenience.
Each of the attributes used with this profile has a single attribute
value, even though the syntax is defined as a SET OF AttributeValue.
There MUST be exactly one instance of AttributeValue present.
The SignedAttributes syntax within signerInfo is defined as a SET OF
Attributes. The SignedAttributes MUST include only one instance of
any particular attribute.
The hardware module MUST include the content-type and message-digest
attributes. If the hardware module includes a real-time clock, then
the hardware module SHOULD also include the signing-time attribute.
The hardware module MAY include any other attribute that it deems
appropriate.
4.2.1. Content Type
The hardware module MUST include a content-type attribute with the
value of id-ct-firmwareLoadError (1.2.840.113549.1.9.16.1.18).
Section 11.1 of [CMS] defines the content-type attribute.
4.2.2. Message Digest
The hardware module MUST include a message-digest attribute, having
as its value the message digest of the FirmwarePackageLoadError
content. Section 11.2 of [CMS] defines the message-digest attribute.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
4.2.3. Signing Time
If the hardware module includes a real-time clock, then hardware
module SHOULD include a signing-time attribute, specifying the time
at which the firmware package load error report was generated.
Section 11.3 of [CMS] defines the signing-time attribute.
5. Hardware Module Name
Support for firmware package load receipts, as discussed in Section
3, is OPTIONAL, and support for the firmware package load error
reports, as discussed in Section 4, is OPTIONAL. Hardware modules
that support receipt or error report generation MUST have unique
serial numbers. Further, hardware modules that support signed
receipt or error report generation MUST have private signature keys
and corresponding signature validation certificates [PROFILE] or
their designators. The conventions for hardware module naming in the
signature validation certificates are specified in this section.
The hardware module vendor or a trusted third party MUST issue the
signature validation certificate prior to deployment of the hardware
module. The certificate is likely to be issued at the time of
manufacture. The subject alternative name in this certificate
identifies the hardware module. The subject distinguished name is
empty, but a critical subject alternative name extension contains the
hardware module name, using the otherName choice within the
GeneralName structure.
The hardware module name form is identified by the id-on-
hardwareModuleName object identifier:
id-on-hardwareModuleName OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) on(8) 4 }
A HardwareModuleName is composed of an object identifier and an octet
string:
HardwareModuleName ::= SEQUENCE {
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING }
The fields of the HardwareModuleName type have the following
meanings:
hwType is an object identifier that identifies the type of hardware
module. A unique object identifier names a hardware model and
revision.
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hwSerialNum is the serial number of the hardware module. No
particular structure is imposed on the serial number; it need not
be an integer. However, the combination of the hwType and
hwSerialNum uniquely identifies the hardware module.
6. Security Considerations
This document describes the use of the Cryptographic Message Syntax
(CMS) to protect firmware packages; therefore, the security
considerations discussed in [CMS] apply to this specification as
well.
The conventions specified in this document raise a few security
considerations of their own.
6.1. Cryptographic Keys and Algorithms
Private signature keys must be protected. Compromise of the private
key used to sign firmware packages permits unauthorized parties to
generate firmware packages that are acceptable to hardware modules.
Compromise of the hardware module private key allows unauthorized
parties to generate signed firmware package load receipts and error
reports.
The firmware-decryption key must be protected. Compromise of the key
may result in the disclosure of the firmware package to unauthorized
parties.
Cryptographic algorithms become weaker with time. As new
cryptanalysis techniques are developed and computing performance
improves, the work factor to break a particular cryptographic
algorithm will be reduced. The ability to change the firmware
package provides an opportunity to update or replace cryptographic
algorithms. Although this capability is desirable, cryptographic
algorithm replacement can lead to interoperability failures.
Therefore, the rollout of new cryptographic algorithms must be
managed. Generally, the previous generation of cryptographic
algorithms and their replacements need to be supported at the same
time in order to facilitate an orderly transition.
6.2. Random Number Generation
When firmware packages are encrypted, the source of the firmware
package must randomly generate firmware-encryption keys. Also, the
generation of public/private signature key pairs relies on a random
numbers. The use of inadequate pseudo-random number generators
(PRNGs) to generate cryptographic keys can result in little or no
security. An attacker may find it much easier to reproduce the PRNG
Housley Standards Track [Page 51]
RFC 4108 Using CMS to Protect Firmware Packages August 2005
environment that produced the keys, searching the resulting small set
of possibilities, rather than brute-force searching the whole key
space. The generation of quality random numbers is difficult. RFC
4086 [RANDOM] offers important guidance in this area.
6.3. Stale Firmware Package Version Number
The firmware signer determines whether a stale version number is
included. The policy of the firmware signer needs to consider many
factors. Consider the flaw found by Ian Goldberg and David Wagner in
the random number generator of the Netscape browser in 1996 [DDJ].
This flaw completely undermines confidentiality protection. A
firmware signer might use the stale version number to ensure that
upgraded hardware modules do not resume use of the flawed firmware.
However, another firmware signer may not consider this an appropriate
situation to employ the stale version number, preferring to delegate
this decision to someone closer to the operation of the hardware
module. Such a person is likely to be in a better position to
evaluate whether other bugs introduced in the newer firmware package
impose worse operational concerns than the confidentiality concern
caused by the flawed random number generator. For example, a user
who never uses the encryption feature of the flawed Netscape browser
will determine the most appropriate version to use without
considering the random number flaw or its fix.
The stale version number is especially useful when the security
interests of the person choosing which firmware package version to
load into a particular hardware module do not align with the security
interests of the firmware package signer. For example, stale version
numbers may be useful in hardware modules that provide digital rights
management (DRM). Also, stale version numbers will be useful when
the deployment organization (as opposed to the firmware package
vendor) is the firmware signer. Further, stale version numbers will
be useful for firmware packages that need to be trusted to implement
organizational (as opposed to the deployment organization) security
policy, regardless of whether the firmware signer is the deployment
organization or the vendor. For example, hardware devices employed
by the military will probably make use of stale version numbers.
The use of a stale version number in a firmware package that employs
the preferred firmware package name form cannot completely prevent
subsequent use of the stale firmware package. Despite this
shortcoming, the feature is included since it is useful in some
important situations. By loading different types of firmware
packages, each with its own stale firmware package version number
until the internal storage for the stale version number is exceeded,
the user can circumvent the mechanism. Consider a hardware module
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
that has storage for two stale version numbers. Suppose that FWPKG-A
version 3 is loaded, indicating that FWPKG-A version 2 is stale. The
user can sequentially load the following:
- FWPKG-B version 8, indicating that FWPKG-B version 4 is stale.
(Note: The internal storage indicates that FWPKG-A version 2
and FWPKG-B version 4 are stale.)
- FWPKG-C version 5, indicating that FWPKG-C version 3 is stale.
(Note: The internal storage indicates that FWPKG-B version 4
and FWPKG-C version 3 are stale.)
- FWPKG-A version 2.
Because many hardware modules are expected to have very few firmware
packages written for them, the stale firmware package version feature
provides important protections. The amount of non-volatile storage
that needs to be dedicated to saving firmware package identifiers and
version numbers depends on the number of firmware packages that are
likely to be developed for the hardware module.
The use of legacy firmware package name form does not improve this
situation. In fact, the legacy firmware package names are usually
larger than an object identifier. Thus, comparable stale version
protection requires more memory.
A firmware signer can ensure that stale version numbers are honored
by limiting the number of different types of firmware packages that
are signed. If all of the hardware modules are able to store a stale
version number for each of the different types of firmware package,
then the hardware module will be able to provide the desired
protection. This requires the firmware signer to have a deep
understanding of all of the hardware modules that might accept the
firmware package.
6.4. Community Identifiers
When a firmware package includes a community identifier, the
confidence that the package is only used by the intended community
depends on the mechanism used to configure community membership.
This document does not specify a mechanism for the assignment of
community membership to hardware modules, and the various
alternatives have different security properties. Also, the authority
that makes community identifier assignments to hardware modules might
be different than the authority that generates firmware packages.
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
7. References
7.1. Normative References
[COMPRESS] Gutmann, P., "Compressed Data Content Type for
Cryptographic Message Syntax (CMS)", RFC 3274, June
2002.
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", RFC
3852, July 2004.
[ESS] Hoffman, P., "Enhanced Security Services for S/MIME",
RFC 2634, June 1999.
[PROFILE] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002.
[SHA1] National Institute of Standards and Technology. FIPS
Pub 180-1: Secure Hash Standard. 17 April 1995.
[STDWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[X.208-88] CCITT. Recommendation X.208: Specification of Abstract
Syntax Notation One (ASN.1). 1988.
[X.209-88] CCITT. Recommendation X.209: Specification of Basic
Encoding Rules for Abstract Syntax Notation One (ASN.1).
1988.
[X.509-88] CCITT. Recommendation X.509: The Directory -
Authentication Framework. 1988.
7.2. Informative References
[ACPROFILE] Farrell, S. and R. Housley, "An Internet Attribute
Certificate Profile for Authorization", RFC 3281, April
2002.
[AES] National Institute of Standards and Technology. FIPS
Pub 197: Advanced Encryption Standard (AES). 26
November 2001.
Housley Standards Track [Page 54]
RFC 4108 Using CMS to Protect Firmware Packages August 2005
[DDJ] Goldberg, I. and D. Wagner. "Randomness and the
Netscape Browser." Dr. Dobb's Journal, January 1996.
[DPD&DPV] Pinkas, D. and R. Housley, "Delegated Path Validation
and Delegated Path Discovery Protocol Requirements", RFC
3379, September 2002.
[OCSP] Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
Adams, "X.509 Internet Public Key Infrastructure Online
Certificate Status Protocol - OCSP", RFC 2560, June
1999.
[PKCS#6] RSA Laboratories. PKCS #6: Extended-Certificate Syntax
Standard, Version 1.5. November 1993.
[RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC
4086, June 2005.
[SECREQMTS] National Institute of Standards and Technology. FIPS
Pub 140-2: Security Requirements for Cryptographic
Modules. 25 May 2001.
[X.509-97] ITU-T. Recommendation X.509: The Directory -
Authentication Framework. 1997.
[X.509-00] ITU-T. Recommendation X.509: The Directory -
Authentication Framework. 2000.
Housley Standards Track [Page 55]
RFC 4108 Using CMS to Protect Firmware Packages August 2005
Appendix A: ASN.1 Module
The ASN.1 module contained in this appendix defines the structures
that are needed to implement the CMS-based firmware package wrapper.
It is expected to be used in conjunction with the ASN.1 modules in
[CMS], [COMPRESS], and [PROFILE].
CMSFirmwareWrapper
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) cms-firmware-wrap(22) }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
IMPORTS
EnvelopedData
FROM CryptographicMessageSyntax -- [CMS]
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0) cms-2004(24) };
-- Firmware Package Content Type and Object Identifier
id-ct-firmwarePackage OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 16 }
FirmwarePkgData ::= OCTET STRING
-- Firmware Package Signed Attributes and Object Identifiers
id-aa-firmwarePackageID OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 35 }
FirmwarePackageIdentifier ::= SEQUENCE {
name PreferredOrLegacyPackageIdentifier,
stale PreferredOrLegacyStalePackageIdentifier OPTIONAL }
PreferredOrLegacyPackageIdentifier ::= CHOICE {
preferred PreferredPackageIdentifier,
legacy OCTET STRING }
PreferredPackageIdentifier ::= SEQUENCE {
fwPkgID OBJECT IDENTIFIER,
verNum INTEGER (0..MAX) }
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PreferredOrLegacyStalePackageIdentifier ::= CHOICE {
preferredStaleVerNum INTEGER (0..MAX),
legacyStaleVersion OCTET STRING }
id-aa-targetHardwareIDs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 36 }
TargetHardwareIdentifiers ::= SEQUENCE OF OBJECT IDENTIFIER
id-aa-decryptKeyID OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 37 }
DecryptKeyIdentifier ::= OCTET STRING
id-aa-implCryptoAlgs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 38 }
ImplementedCryptoAlgorithms ::= SEQUENCE OF OBJECT IDENTIFIER
id-aa-implCompressAlgs OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 43 }
ImplementedCompressAlgorithms ::= SEQUENCE OF OBJECT IDENTIFIER
id-aa-communityIdentifiers OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 40 }
CommunityIdentifiers ::= SEQUENCE OF CommunityIdentifier
CommunityIdentifier ::= CHOICE {
communityOID OBJECT IDENTIFIER,
hwModuleList HardwareModules }
HardwareModules ::= SEQUENCE {
hwType OBJECT IDENTIFIER,
hwSerialEntries SEQUENCE OF HardwareSerialEntry }
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
HardwareSerialEntry ::= CHOICE {
all NULL,
single OCTET STRING,
block SEQUENCE {
low OCTET STRING,
high OCTET STRING } }
id-aa-firmwarePackageInfo OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 42 }
FirmwarePackageInfo ::= SEQUENCE {
fwPkgType INTEGER OPTIONAL,
dependencies SEQUENCE OF
PreferredOrLegacyPackageIdentifier OPTIONAL }
-- Firmware Package Unsigned Attributes and Object Identifiers
id-aa-wrappedFirmwareKey OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 39 }
WrappedFirmwareKey ::= EnvelopedData
-- Firmware Package Load Receipt Content Type and Object Identifier
id-ct-firmwareLoadReceipt OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 17 }
FirmwarePackageLoadReceipt ::= SEQUENCE {
version FWReceiptVersion DEFAULT v1,
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING,
fwPkgName PreferredOrLegacyPackageIdentifier,
trustAnchorKeyID OCTET STRING OPTIONAL,
decryptKeyID [1] OCTET STRING OPTIONAL }
FWReceiptVersion ::= INTEGER { v1(1) }
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RFC 4108 Using CMS to Protect Firmware Packages August 2005
-- Firmware Package Load Error Report Content Type
-- and Object Identifier
id-ct-firmwareLoadError OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) ct(1) 18 }
FirmwarePackageLoadError ::= SEQUENCE {
version FWErrorVersion DEFAULT v1,
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING,
errorCode FirmwarePackageLoadErrorCode,
vendorErrorCode VendorLoadErrorCode OPTIONAL,
fwPkgName PreferredOrLegacyPackageIdentifier OPTIONAL,
config [1] SEQUENCE OF CurrentFWConfig OPTIONAL }
FWErrorVersion ::= INTEGER { v1(1) }
CurrentFWConfig ::= SEQUENCE {
fwPkgType INTEGER OPTIONAL,
fwPkgName PreferredOrLegacyPackageIdentifier }
FirmwarePackageLoadErrorCode ::= ENUMERATED {
decodeFailure (1),
badContentInfo (2),
badSignedData (3),
badEncapContent (4),
badCertificate (5),
badSignerInfo (6),
badSignedAttrs (7),
badUnsignedAttrs (8),
missingContent (9),
noTrustAnchor (10),
notAuthorized (11),
badDigestAlgorithm (12),
badSignatureAlgorithm (13),
unsupportedKeySize (14),
signatureFailure (15),
contentTypeMismatch (16),
badEncryptedData (17),
unprotectedAttrsPresent (18),
badEncryptContent (19),
badEncryptAlgorithm (20),
missingCiphertext (21),
noDecryptKey (22),
decryptFailure (23),
badCompressAlgorithm (24),
missingCompressedContent (25),
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decompressFailure (26),
wrongHardware (27),
stalePackage (28),
notInCommunity (29),
unsupportedPackageType (30),
missingDependency (31),
wrongDependencyVersion (32),
insufficientMemory (33),
badFirmware (34),
unsupportedParameters (35),
breaksDependency (36),
otherError (99) }
VendorLoadErrorCode ::= INTEGER
-- Other Name syntax for Hardware Module Name
id-on-hardwareModuleName OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) on(8) 4 }
HardwareModuleName ::= SEQUENCE {
hwType OBJECT IDENTIFIER,
hwSerialNum OCTET STRING }
END
Author's Address
Russell Housley
Vigil Security, LLC
918 Spring Knoll Drive
Herndon, VA 20170
USA
EMail: housley@vigilsec.com
Housley Standards Track [Page 60]
RFC 4108 Using CMS to Protect Firmware Packages August 2005
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
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OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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The IETF invites any interested party to bring to its attention any
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this standard. Please address the information to the IETF at ietf-
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Housley Standards Track [Page 61]