package/ead/src/tinysrp/tinysrp.c

   1 /* This bit implements a simple API for using the SRP library over sockets. */
   2
   3 #include <stdio.h>
   4 #include <string.h>
   5 #include <stdlib.h>
   6 #include <unistd.h>
   7 #include <sys/types.h>
   8 #include <sys/socket.h>
   9 #include "t_defines.h"
  10 #include "t_pwd.h"
  11 #include "t_server.h"
  12 #include "t_client.h"
  13 #include "tinysrp.h"
  14
  15 #ifndef MSG_WAITALL
  16 #ifdef linux
  17 #define MSG_WAITALL 0x100       /* somehow not defined on my box */
  18 #endif
  19 #endif
  20
  21 /* This is called by the client with a connected socket, username, and
  22 passphrase.  pass can be NULL in which case the user is queried. */
  23
  24 int tsrp_client_authenticate(int s, char *user, char *pass, TSRP_SESSION *tsrp)
  25 {
  26         int i, index;
  27         unsigned char username[MAXUSERLEN + 1], sbuf[MAXSALTLEN];
  28         unsigned char msgbuf[MAXPARAMLEN + 1], bbuf[MAXPARAMLEN];
  29         unsigned char passbuf[128], *skey;
  30         struct t_client *tc;
  31         struct t_preconf *tcp;          /* @@@ should go away */
  32         struct t_num salt, *A, B;
  33
  34         /* Send the username. */
  35
  36         i = strlen(user);
  37         if (i > MAXUSERLEN) {
  38                 i = MAXUSERLEN;
  39         }
  40         msgbuf[0] = i;
  41         memcpy(msgbuf + 1, user, i);
  42         if (send(s, msgbuf, i + 1, 0) < 0) {
  43                 return 0;
  44         }
  45         memcpy(username, user, i);
  46         username[i] = '\0';
  47
  48         /* Get the prime index and salt. */
  49
  50         i = recv(s, msgbuf, 2, MSG_WAITALL);
  51         if (i <= 0) {
  52                 return 0;
  53         }
  54         index = msgbuf[0];
  55         if (index <= 0 || index > t_getprecount()) {
  56                 return 0;
  57         }
  58         tcp = t_getpreparam(index - 1);
  59         salt.len = msgbuf[1];
  60         if (salt.len > MAXSALTLEN) {
  61                 return 0;
  62         }
  63         salt.data = sbuf;
  64         i = recv(s, sbuf, salt.len, MSG_WAITALL);
  65         if (i <= 0) {
  66                 return 0;
  67         }
  68
  69         /* @@@ t_clientopen() needs a variant that takes the index */
  70
  71         tc = t_clientopen(username, &tcp->modulus, &tcp->generator, &salt);
  72         if (tc == NULL) {
  73                 return 0;
  74         }
  75
  76         /* Calculate A and send it to the server. */
  77
  78         A = t_clientgenexp(tc);
  79         msgbuf[0] = A->len - 1;         /* len is max 256 */
  80         memcpy(msgbuf + 1, A->data, A->len);
  81         if (send(s, msgbuf, A->len + 1, 0) < 0) {
  82                 return 0;
  83         }
  84
  85         /* Ask the user for the passphrase. */
  86
  87         if (pass == NULL) {
  88                 t_getpass(passbuf, sizeof(passbuf), "Enter password:");
  89                 pass = passbuf;
  90         }
  91         t_clientpasswd(tc, pass);
  92
  93         /* Get B from the server. */
  94
  95         i = recv(s, msgbuf, 1, 0);
  96         if (i <= 0) {
  97                 return 0;
  98         }
  99         B.len = msgbuf[0] + 1;
 100         B.data = bbuf;
 101         i = recv(s, bbuf, B.len, MSG_WAITALL);
 102         if (i <= 0) {
 103                 return 0;
 104         }
 105
 106         /* Compute the session key. */
 107
 108         skey = t_clientgetkey(tc, &B);
 109         if (skey == NULL) {
 110                 return 0;
 111         }
 112
 113         /* Send the response. */
 114
 115         if (send(s, t_clientresponse(tc), RESPONSE_LEN, 0) < 0) {
 116                 return 0;
 117         }
 118
 119         /* Get the server's response. */
 120
 121         i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
 122         if (i <= 0) {
 123                 return 0;
 124         }
 125         if (t_clientverify(tc, msgbuf) != 0) {
 126                 return 0;
 127         }
 128
 129         /* All done.  Now copy the key and clean up. */
 130
 131         if (tsrp) {
 132                 memcpy(tsrp->username, username, strlen(username) + 1);
 133                 memcpy(tsrp->key, skey, SESSION_KEY_LEN);
 134         }
 135         t_clientclose(tc);
 136
 137         return 1;
 138 }
 139
 140 /* This is called by the server with a connected socket. */
 141
 142 int tsrp_server_authenticate(int s, TSRP_SESSION *tsrp)
 143 {
 144         int i, j;
 145         unsigned char username[MAXUSERLEN], *skey;
 146         unsigned char msgbuf[MAXPARAMLEN + 1], abuf[MAXPARAMLEN];
 147         struct t_server *ts;
 148         struct t_num A, *B;
 149
 150         /* Get the username. */
 151
 152         i = recv(s, msgbuf, 1, 0);
 153         if (i <= 0) {
 154                 return 0;
 155         }
 156         j = msgbuf[0];
 157         i = recv(s, username, j, MSG_WAITALL);
 158         if (i <= 0) {
 159                 return 0;
 160         }
 161         username[j] = '\0';
 162
 163         ts = t_serveropen(username);
 164         if (ts == NULL) {
 165                 return 0;
 166         }
 167
 168         /* Send the prime index and the salt. */
 169
 170         msgbuf[0] = ts->index;                  /* max 256 primes... */
 171         i = ts->s.len;
 172         msgbuf[1] = i;
 173         memcpy(msgbuf + 2, ts->s.data, i);
 174         if (send(s, msgbuf, i + 2, 0) < 0) {
 175                 return 0;
 176         }
 177
 178         /* Calculate B while we're waiting. */
 179
 180         B = t_servergenexp(ts);
 181
 182         /* Get A from the client. */
 183
 184         i = recv(s, msgbuf, 1, 0);
 185         if (i <= 0) {
 186                 return 0;
 187         }
 188         A.len = msgbuf[0] + 1;
 189         A.data = abuf;
 190         i = recv(s, abuf, A.len, MSG_WAITALL);
 191         if (i <= 0) {
 192                 return 0;
 193         }
 194
 195         /* Now send B. */
 196
 197         msgbuf[0] = B->len - 1;
 198         memcpy(msgbuf + 1, B->data, B->len);
 199         if (send(s, msgbuf, B->len + 1, 0) < 0) {
 200                 return 0;
 201         }
 202
 203         /* Calculate the session key while we're waiting. */
 204
 205         skey = t_servergetkey(ts, &A);
 206         if (skey == NULL) {
 207                 return 0;
 208         }
 209
 210         /* Get the response from the client. */
 211
 212         i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
 213         if (i <= 0) {
 214                 return 0;
 215         }
 216         if (t_serververify(ts, msgbuf) != 0) {
 217                 return 0;
 218         }
 219
 220         /* Client authenticated.  Now authenticate ourselves to the client. */
 221
 222         if (send(s, t_serverresponse(ts), RESPONSE_LEN, 0) < 0) {
 223                 return 0;
 224         }
 225
 226         /* Copy the key and clean up. */
 227
 228         if (tsrp) {
 229                 memcpy(tsrp->username, username, strlen(username) + 1);
 230                 memcpy(tsrp->key, skey, SESSION_KEY_LEN);
 231         }
 232         t_serverclose(ts);
 233
 234         return 1;
 235 }