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client2.c (5872B)
1 #! /usr/bin/env sheepy
2
3 /*
4 client2 and server2 are following request/response model.
5
6 Steps in client
7 - generate keys
8 - connect to server
9 - send signature, identity public key, session public key, write 0 for id key and signature if
10 the client doesn't have an id
11 - check server identity with signature, store nonce
12 - store remote public key
13 - send encrypted message
14 - get encrypted response
15
16 Steps in server
17 - generate keys
18 - start event loop
19 - store remote session public key
20 - check identity with signature
21 - send signature, identity public key, session public key, nonce
22 - get encrypted message
23 - send encrypted response
24
25 This version uses secret/symetric key encryption after the key exchange.
26
27 For more nonce randomness, the server can provide the first nonce with the public keys when the session opens
28
29 >> when sending large amount of data, use stream functions
30 >> use aead functions only if there are metadata
31 >> privelege separation: have a seperate process with the secrets
32 >> to change id: sign id public key, sign id public key and signature and the new id public key with the new id key
33
34 */
35
36 #include "libsheepyObject.h"
37
38 #include <sys/types.h>
39 #include <sys/socket.h>
40 #include <netdb.h>
41 #include <netinet/in.h>
42
43 #include "sel.h"
44
45 int main(int ac, char **av) {
46
47 setLogMode(LOG_FUNC);
48
49 if (not selInit()) ret 1;
50
51 // generate keys
52 bool isKnownServer = no;
53 const char* remoteIdFilename = "remoteId.bin";
54 bool sendClientIdToServer = yes;
55
56 newKeys();
57 newSignKeys();
58
59 // load server id if possible
60 if (isPath(remoteIdFilename)) {
61 logI("Server is known");
62 pError0(bLReadFile(remoteIdFilename, remoteId, sizeof(remoteId)));
63 isKnownServer = yes;
64 }
65
66 char *msg = "Hello";
67
68 logI("message: %s\n", msg);
69
70
71 // connect to server
72 int sock;
73 struct sockaddr_in server;
74 struct hostent *hp;
75 int mysock;
76 char buf[128*1024];
77 int rval;
78
79 sock = socket(AF_INET, SOCK_STREAM, 0);
80 if (sock < 0){
81 perror("Failed to create socket");
82 }
83
84 server.sin_family = AF_INET;
85
86 hp = gethostbyname(av[1]);
87 if (hp==0) {
88 perror("gethostbyname failed");
89 close(sock);
90 exit(1);
91 }
92
93 memcpy(&server.sin_addr, hp->h_addr, hp->h_length);
94 server.sin_port = htons(5000);
95
96 if (connect(sock,(struct sockaddr *) &server, sizeof(server))){
97 perror("connect failed");
98 close(sock);
99 exit(1);
100 }
101
102 void snd(void *buf, size_t sz) {
103 logVarG(sz);
104 if(send(sock, buf, sz, 0) < 0){
105 perror("send failed");
106 close(sock);
107 exit(1);
108 }
109 }
110
111 void rcv(void *buf, size_t sz) {
112 while (sz > 0) {
113 rval = recv(sock, buf, sz, MSG_WAITALL);
114 if (rval < 0) {
115 perror("reading message");
116 exit(1);
117 }
118 else if (rval == 0) {
119 logI("Ending connection");
120 close(sock);
121 exit(0);
122 }
123 sz -= rval;
124 }
125 logVarG(rval);
126 }
127
128 // send public key
129 // store remote public key
130 void getServerPublicKey(void) {
131 u8 exchange[crypto_sign_BYTES + crypto_sign_PUBLICKEYBYTES + sizeof(keys.publicKey)] = init0Var;
132 memcpy(exchange+crypto_sign_BYTES+crypto_sign_PUBLICKEYBYTES, &keys.publicKey, sizeof(keys.publicKey));
133 if (not sendClientIdToServer) {
134 snd(exchange, sizeof(exchange));
135 }
136 else {
137 // send client id
138 // sign keys with id key
139 memcpy(exchange+crypto_sign_BYTES, &identityKeys.publicKey, sizeof(identityKeys.publicKey));
140 u8 signed_message[sizeof(exchange)] = init0Var;
141 unsigned long long signed_message_len = 0;
142 crypto_sign(signed_message, &signed_message_len, exchange+crypto_sign_BYTES, sizeof(exchange)-crypto_sign_BYTES, identityKeys.secretKey);
143 snd(signed_message, sizeof(signed_message));
144 }
145
146 u8 serverInfo[crypto_sign_BYTES + crypto_sign_PUBLICKEYBYTES + sizeof(keys.remotePublicKey) + crypto_box_NONCEBYTES] = init0Var;
147 rcv(serverInfo, sizeof(serverInfo));
148
149 // check remote server
150 u8 unsigned_message[crypto_sign_PUBLICKEYBYTES + sizeof(keys.remotePublicKey) + crypto_box_NONCEBYTES] = init0Var;
151 unsigned long long unsigned_message_len;
152 const u8 *idPublicKey = remoteId;
153 if (not isKnownServer) {
154 // TOFU - trust on first use
155 idPublicKey = serverInfo + crypto_sign_BYTES;
156 }
157
158 if (crypto_sign_open(unsigned_message, &unsigned_message_len, serverInfo, sizeof(serverInfo), idPublicKey) != 0) {
159 logE("Incorrect signature!");
160 }
161 else {
162 logP("Correct signature");
163 }
164
165 memcpy(keys.remotePublicKey, unsigned_message + crypto_sign_PUBLICKEYBYTES, sizeof(keys.remotePublicKey));
166 memcpy(sessionKeys.nonce, unsigned_message + crypto_sign_PUBLICKEYBYTES + sizeof(keys.remotePublicKey), crypto_box_NONCEBYTES);
167
168 if (not isKnownServer) {
169 // store server id key
170 pError0(writeFile(remoteIdFilename, (u8*)idPublicKey, crypto_sign_PUBLICKEYBYTES));
171 logI("Saved server id");
172 }
173
174 logD("Remote public key");
175 loghex(keys.remotePublicKey, sizeof(keys.remotePublicKey));
176 put;
177
178 // key exchange
179 if (not computeSharedKeys(CLIENT_SESSION_KEYS)) {
180 logE("Invalid server key");
181 exit(1);
182 }
183 }
184
185 getServerPublicKey();
186
187 // send encrypted message
188 // *nonce is incremented by after sending or receiving a message
189 // *nonce is allowed to wrap from the max value
190 u64 *nonce = (u64*)sessionKeys.nonce;
191 logVarG(*nonce);
192 int len = selEncrypt(buf, sizeof(buf), msg, strlen(msg));
193 inc *nonce;
194
195 logVarG(len);
196
197 snd(&len, sizeof(len));
198 snd(buf, len);
199
200 // get encrypted response
201 rcv(&len, sizeof(len));
202 rcv(buf, len);
203
204 u8 decrypted[1000];
205 logVarG(*nonce);
206 len = selDecrypt(decrypted, sizeof(decrypted), buf, len);
207 inc *nonce;
208
209 if (!len) {
210 logE("failed to decrypt");
211 ret 1;
212 }
213
214 decrypted[len] = 0;
215
216 logI("decrypted: %s", decrypted);
217
218 close(sock);
219 }
220 // vim: set expandtab ts=2 sw=2: