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import "golang.org/x/oauth2/google/externalaccount"
Package externalaccount provides support for creating workload identity federation and workforce identity federation token sources that can be used to access Google Cloud resources from external identity providers.
Using workload identity federation, your application can access Google Cloud resources from Amazon Web Services (AWS), Microsoft Azure or any identity provider that supports OpenID Connect (OIDC) or SAML 2.0. Traditionally, applications running outside Google Cloud have used service account keys to access Google Cloud resources. Using identity federation, you can allow your workload to impersonate a service account. This lets you access Google Cloud resources directly, eliminating the maintenance and security burden associated with service account keys.
Follow the detailed instructions on how to configure Workload Identity Federation in various platforms:
Amazon Web Services (AWS): https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#aws Microsoft Azure: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#azure OIDC identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#oidc SAML 2.0 identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#saml
For OIDC and SAML providers, the library can retrieve tokens in fours ways: from a local file location (file-sourced credentials), from a server (URL-sourced credentials), from a local executable (executable-sourced credentials), or from a user defined function that returns an OIDC or SAML token. For file-sourced credentials, a background process needs to be continuously refreshing the file location with a new OIDC/SAML token prior to expiration. For tokens with one hour lifetimes, the token needs to be updated in the file every hour. The token can be stored directly as plain text or in JSON format. For URL-sourced credentials, a local server needs to host a GET endpoint to return the OIDC/SAML token. The response can be in plain text or JSON. Additional required request headers can also be specified. For executable-sourced credentials, an application needs to be available to output the OIDC/SAML token and other information in a JSON format. For more information on how these work (and how to implement executable-sourced credentials), please check out: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#create_a_credential_configuration
To use a custom function to supply the token, define a struct that implements the SubjectTokenSupplier interface for OIDC/SAML providers, or one that implements AwsSecurityCredentialsSupplier for AWS providers. This can then be used when building a Config. The golang.org/x/oauth2.TokenSource created from the config using NewTokenSource can then be used to access Google Cloud resources. For instance, you can create a new client from the cloud.google.com/go/storage package and pass in option.WithTokenSource(yourTokenSource))
Note that this library does not perform any validation on the token_url, token_info_url, or service_account_impersonation_url fields of the credential configuration. It is not recommended to use a credential configuration that you did not generate with the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
Workforce identity federation lets you use an external identity provider (IdP) to authenticate and authorize a workforce—a group of users, such as employees, partners, and contractors—using IAM, so that the users can access Google Cloud services. Workforce identity federation extends Google Cloud's identity capabilities to support syncless, attribute-based single sign on.
With workforce identity federation, your workforce can access Google Cloud resources using an external identity provider (IdP) that supports OpenID Connect (OIDC) or SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation Services (AD FS), Okta, and others.
Follow the detailed instructions on how to configure Workload Identity Federation in various platforms:
Azure AD: https://cloud.google.com/iam/docs/workforce-sign-in-azure-ad Okta: https://cloud.google.com/iam/docs/workforce-sign-in-okta OIDC identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#oidc SAML 2.0 identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#saml
For workforce identity federation, the library can retrieve tokens in four ways: from a local file location (file-sourced credentials), from a server (URL-sourced credentials), from a local executable (executable-sourced credentials), or from a user supplied function that returns an OIDC or SAML token. For file-sourced credentials, a background process needs to be continuously refreshing the file location with a new OIDC/SAML token prior to expiration. For tokens with one hour lifetimes, the token needs to be updated in the file every hour. The token can be stored directly as plain text or in JSON format. For URL-sourced credentials, a local server needs to host a GET endpoint to return the OIDC/SAML token. The response can be in plain text or JSON. Additional required request headers can also be specified. For executable-sourced credentials, an application needs to be available to output the OIDC/SAML token and other information in a JSON format. For more information on how these work (and how to implement executable-sourced credentials), please check out: https://cloud.google.com/iam/docs/workforce-obtaining-short-lived-credentials#generate_a_configuration_file_for_non-interactive_sign-in
To use a custom function to supply the token, define a struct that implements the SubjectTokenSupplier interface for OIDC/SAML providers. This can then be used when building a Config. The golang.org/x/oauth2.TokenSource created from the config using NewTokenSource can then be used access Google Cloud resources. For instance, you can create a new client from the cloud.google.com/go/storage package and pass in option.WithTokenSource(yourTokenSource))
Note that this library does not perform any validation on the token_url, token_info_url, or service_account_impersonation_url fields of the credential configuration. It is not recommended to use a credential configuration that you did not generate with the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
func NewTokenSource(ctx context.Context, conf Config) (oauth2.TokenSource, error)
NewTokenSource Returns an external account TokenSource using the provided external account config.
type AwsSecurityCredentials struct {
// AccessKeyId is the AWS Access Key ID - Required.
AccessKeyID string `json:"AccessKeyID"`
// SecretAccessKey is the AWS Secret Access Key - Required.
SecretAccessKey string `json:"SecretAccessKey"`
// SessionToken is the AWS Session token. This should be provided for temporary AWS security credentials - Optional.
SessionToken string `json:"Token"`
}
AwsSecurityCredentials models AWS security credentials.
type AwsSecurityCredentialsSupplier interface {
// AwsRegion should return the AWS region or an error.
AwsRegion(ctx context.Context, options SupplierOptions) (string, error)
// GetAwsSecurityCredentials should return a valid set of AwsSecurityCredentials or an error.
// The external account token source does not cache the returned security credentials, so caching
// logic should be implemented in the supplier to prevent multiple requests for the same security credentials.
AwsSecurityCredentials(ctx context.Context, options SupplierOptions) (*AwsSecurityCredentials, error)
}
AWSSecurityCredentialsSupplier can be used to supply AwsSecurityCredentials and an AWS Region to exchange for a GCP access token.
type Config struct {
// Audience is the Secure Token Service (STS) audience which contains the resource name for the workload
// identity pool or the workforce pool and the provider identifier in that pool. Required.
Audience string
// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec.
// Expected values include:
// “urn:ietf:params:oauth:token-type:jwt”
// “urn:ietf:params:oauth:token-type:id-token”
// “urn:ietf:params:oauth:token-type:saml2”
// “urn:ietf:params:aws:token-type:aws4_request”
// Required.
SubjectTokenType string
// TokenURL is the STS token exchange endpoint. If not provided, will default to
// https://sts.UNIVERSE_DOMAIN/v1/token, with UNIVERSE_DOMAIN set to the
// default service domain googleapis.com unless UniverseDomain is set.
// Optional.
TokenURL string
// TokenInfoURL is the token_info endpoint used to retrieve the account related information (
// user attributes like account identifier, eg. email, username, uid, etc). This is
// needed for gCloud session account identification. Optional.
TokenInfoURL string
// ServiceAccountImpersonationURL is the URL for the service account impersonation request. This is only
// required for workload identity pools when APIs to be accessed have not integrated with UberMint. Optional.
ServiceAccountImpersonationURL string
// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
// token will be valid for. If not provided, it will default to 3600. Optional.
ServiceAccountImpersonationLifetimeSeconds int
// ClientSecret is currently only required if token_info endpoint also
// needs to be called with the generated GCP access token. When provided, STS will be
// called with additional basic authentication using ClientId as username and ClientSecret as password. Optional.
ClientSecret string
// ClientID is only required in conjunction with ClientSecret, as described above. Optional.
ClientID string
// CredentialSource contains the necessary information to retrieve the token itself, as well
// as some environmental information. One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or
// CredentialSource must be provided. Optional.
CredentialSource *CredentialSource
// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
// will set the x-goog-user-project header which overrides the project associated with the credentials. Optional.
QuotaProjectID string
// Scopes contains the desired scopes for the returned access token. Optional.
Scopes []string
// WorkforcePoolUserProject is the workforce pool user project number when the credential
// corresponds to a workforce pool and not a workload identity pool.
// The underlying principal must still have serviceusage.services.use IAM
// permission to use the project for billing/quota. Optional.
WorkforcePoolUserProject string
// SubjectTokenSupplier is an optional token supplier for OIDC/SAML credentials.
// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
SubjectTokenSupplier SubjectTokenSupplier
// AwsSecurityCredentialsSupplier is an AWS Security Credential supplier for AWS credentials.
// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
AwsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
// UniverseDomain is the default service domain for a given Cloud universe.
// This value will be used in the default STS token URL. The default value
// is "googleapis.com". It will not be used if TokenURL is set. Optional.
UniverseDomain string
}
Config stores the configuration for fetching tokens with external credentials.
type CredentialSource struct {
// File is the location for file sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
File string `json:"file"`
// Url is the URL to call for URL sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
URL string `json:"url"`
// Headers are the headers to attach to the request for URL sourced credentials.
Headers map[string]string `json:"headers"`
// Executable is the configuration object for executable sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
Executable *ExecutableConfig `json:"executable"`
// EnvironmentID is the EnvironmentID used for AWS sourced credentials. This should start with "AWS".
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
EnvironmentID string `json:"environment_id"`
// RegionURL is the metadata URL to retrieve the region from for EC2 AWS credentials.
RegionURL string `json:"region_url"`
// RegionalCredVerificationURL is the AWS regional credential verification URL, will default to
// "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15" if not provided."
RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
// IMDSv2SessionTokenURL is the URL to retrieve the session token when using IMDSv2 in AWS.
IMDSv2SessionTokenURL string `json:"imdsv2_session_token_url"`
// Format is the format type for the subject token. Used for File and URL sourced credentials. Expected values are "text" or "json".
Format Format `json:"format"`
}
CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
type ExecutableConfig struct {
// Command is the the full command to run to retrieve the subject token.
// This can include arguments. Must be an absolute path for the program. Required.
Command string `json:"command"`
// TimeoutMillis is the timeout duration, in milliseconds. Defaults to 30000 milliseconds when not provided. Optional.
TimeoutMillis *int `json:"timeout_millis"`
// OutputFile is the absolute path to the output file where the executable will cache the response.
// If specified the auth libraries will first check this location before running the executable. Optional.
OutputFile string `json:"output_file"`
}
ExecutableConfig contains information needed for executable sourced credentials.
type Format struct {
// Type should be either "text" or "json". This determines whether the file or URL sourced credentials
// expect a simple text subject token or if the subject token will be contained in a JSON object.
// When not provided "text" type is assumed.
Type string `json:"type"`
// SubjectTokenFieldName is only required for JSON format. This is the field name that the credentials will check
// for the subject token in the file or URL response. This would be "access_token" for azure.
SubjectTokenFieldName string `json:"subject_token_field_name"`
}
Format contains information needed to retireve a subject token for URL or File sourced credentials.
type SubjectTokenSupplier interface {
// SubjectToken should return a valid subject token or an error.
// The external account token source does not cache the returned subject token, so caching
// logic should be implemented in the supplier to prevent multiple requests for the same subject token.
SubjectToken(ctx context.Context, options SupplierOptions) (string, error)
}
SubjectTokenSupplier can be used to supply a subject token to exchange for a GCP access token.
type SupplierOptions struct {
// Audience is the requested audience for the external account credential.
Audience string
// Subject token type is the requested subject token type for the external account credential. Expected values include:
// “urn:ietf:params:oauth:token-type:jwt”
// “urn:ietf:params:oauth:token-type:id-token”
// “urn:ietf:params:oauth:token-type:saml2”
// “urn:ietf:params:aws:token-type:aws4_request”
SubjectTokenType string
}
SupplierOptions contains information about the requested subject token or AWS security credentials from the Google external account credential.