citadel/serv_crypto.c

   1 /* $Id$ */
   2
   3 #include <string.h>
   4 #include <unistd.h>
   5 #include <sys/types.h>
   6 #include "sysdep.h"
   7
   8 #ifdef HAVE_OPENSSL
   9 #include <openssl/ssl.h>
  10 #include <openssl/err.h>
  11 #include <openssl/rand.h>
  12 #endif
  13
  14 #if TIME_WITH_SYS_TIME
  15 # include <sys/time.h>
  16 # include <time.h>
  17 #else
  18 # if HAVE_SYS_TIME_H
  19 #  include <sys/time.h>
  20 # else
  21 #  include <time.h>
  22 # endif
  23 #endif
  24
  25 #ifdef HAVE_PTHREAD_H
  26 #include <pthread.h>
  27 #endif
  28
  29 #ifdef HAVE_SYS_SELECT_H
  30 #include <sys/select.h>
  31 #endif
  32
  33 #include <stdio.h>
  34 #include "server.h"
  35 #include "serv_crypto.h"
  36 #include "sysdep_decls.h"
  37 #include "serv_extensions.h"
  38
  39
  40 #ifdef HAVE_OPENSSL
  41 SSL_CTX *ssl_ctx;               /* SSL context */
  42 pthread_mutex_t **SSLCritters;  /* Things needing locking */
  43
  44 static unsigned long id_callback(void)
  45 {
  46         return (unsigned long) pthread_self();
  47 }
  48
  49  /*
  50   * Set up the cert things on the server side. We do need both the
  51   * private key (in key_file) and the cert (in cert_file).
  52   * Both files may be identical.
  53   *
  54   * This function is taken from OpenSSL apps/s_cb.c
  55   */
  56
  57 static int set_cert_stuff(SSL_CTX * ctx,
  58                           const char *cert_file, const char *key_file)
  59 {
  60         if (cert_file != NULL) {
  61                 if (SSL_CTX_use_certificate_file(ctx, cert_file,
  62                                                  SSL_FILETYPE_PEM) <= 0) {
  63                         lprintf(3, "unable to get certificate from '%s'",
  64                                 cert_file);
  65                         return (0);
  66                 }
  67                 if (key_file == NULL)
  68                         key_file = cert_file;
  69                 if (SSL_CTX_use_PrivateKey_file(ctx, key_file,
  70                                                 SSL_FILETYPE_PEM) <= 0) {
  71                         lprintf(3, "unable to get private key from '%s'",
  72                                 key_file);
  73                         return (0);
  74                 }
  75                 /* Now we know that a key and cert have been set against
  76                  * the SSL context */
  77                 if (!SSL_CTX_check_private_key(ctx)) {
  78                         lprintf(3,
  79                                 "Private key does not match the certificate public key");
  80                         return (0);
  81                 }
  82         }
  83         return (1);
  84 }
  85
  86
  87 void init_ssl(void)
  88 {
  89         SSL_METHOD *ssl_method;
  90         DH *dh;
  91
  92         if (!access("/var/run/egd-pool", F_OK))
  93                 RAND_egd("/var/run/egd-pool");
  94
  95         if (!RAND_status()) {
  96                 lprintf(2,
  97                         "PRNG not adequately seeded, won't do SSL/TLS\n");
  98                 return;
  99         }
 100         SSLCritters =
 101             mallok(CRYPTO_num_locks() * sizeof(pthread_mutex_t *));
 102         if (!SSLCritters) {
 103                 lprintf(1, "citserver: can't allocate memory!!\n");
 104                 /* Nothing's been initialized, just die */
 105                 exit(1);
 106         } else {
 107                 int a;
 108
 109                 for (a = 0; a < CRYPTO_num_locks(); a++) {
 110                         SSLCritters[a] = mallok(sizeof(pthread_mutex_t));
 111                         if (!SSLCritters[a]) {
 112                                 lprintf(1,
 113                                         "citserver: can't allocate memory!!\n");
 114                                 /* Nothing's been initialized, just die */
 115                                 exit(1);
 116                         }
 117                         pthread_mutex_init(SSLCritters[a], NULL);
 118                 }
 119         }
 120
 121         /*
 122          * Initialize SSL transport layer
 123          */
 124         SSL_library_init();
 125         SSL_load_error_strings();
 126         ssl_method = SSLv23_server_method();
 127         if (!(ssl_ctx = SSL_CTX_new(ssl_method))) {
 128                 lprintf(2, "SSL_CTX_new failed: %s\n",
 129                         ERR_reason_error_string(ERR_get_error()));
 130                 return;
 131         }
 132         if (!(SSL_CTX_set_cipher_list(ssl_ctx, CIT_CIPHERS))) {
 133                 lprintf(2, "SSL: No ciphers available\n");
 134                 SSL_CTX_free(ssl_ctx);
 135                 ssl_ctx = NULL;
 136                 return;
 137         }
 138 #if 0
 139 #if SSLEAY_VERSION_NUMBER >= 0x00906000L
 140         SSL_CTX_set_mode(ssl_ctx, SSL_CTX_get_mode(ssl_ctx) |
 141                          SSL_MODE_AUTO_RETRY);
 142 #endif
 143 #endif
 144
 145         CRYPTO_set_locking_callback(ssl_lock);
 146         CRYPTO_set_id_callback(id_callback);
 147
 148         /* Load DH parameters into the context */
 149         dh = DH_new();
 150         if (!dh) {
 151                 lprintf(2, "init_ssl() can't allocate a DH object: %s\n",
 152                         ERR_reason_error_string(ERR_get_error()));
 153                 SSL_CTX_free(ssl_ctx);
 154                 ssl_ctx = NULL;
 155                 return;
 156         }
 157         if (!(BN_hex2bn(&(dh->p), DH_P))) {
 158                 lprintf(2, "init_ssl() can't assign DH_P: %s\n",
 159                         ERR_reason_error_string(ERR_get_error()));
 160                 SSL_CTX_free(ssl_ctx);
 161                 ssl_ctx = NULL;
 162                 return;
 163         }
 164         if (!(BN_hex2bn(&(dh->g), DH_G))) {
 165                 lprintf(2, "init_ssl() can't assign DH_G: %s\n",
 166                         ERR_reason_error_string(ERR_get_error()));
 167                 SSL_CTX_free(ssl_ctx);
 168                 ssl_ctx = NULL;
 169                 return;
 170         }
 171         dh->length = DH_L;
 172         SSL_CTX_set_tmp_dh(ssl_ctx, dh);
 173         DH_free(dh);
 174
 175         /* Get our certificates in order */
 176         if (set_cert_stuff(ssl_ctx,
 177                            BBSDIR "/keys/citadel.cer",
 178                            BBSDIR "/keys/citadel.key") != 1) {
 179
 180                 lprintf(3, "SSL ERROR: cert is bad!\n");
 181
 182         }
 183
 184         /* Finally let the server know we're here */
 185         CtdlRegisterProtoHook(cmd_stls, "STLS", "Start SSL/TLS session");
 186         CtdlRegisterProtoHook(cmd_gtls, "GTLS",
 187                               "Get SSL/TLS session status");
 188         CtdlRegisterSessionHook(endtls, EVT_STOP);
 189 }
 190
 191
 192 /*
 193  * client_write_ssl() Send binary data to the client encrypted.
 194  */
 195 void client_write_ssl(char *buf, int nbytes)
 196 {
 197         int retval;
 198         int nremain;
 199         char junk[1];
 200
 201         nremain = nbytes;
 202
 203         while (nremain > 0) {
 204                 if (SSL_want_write(CC->ssl)) {
 205                         if ((SSL_read(CC->ssl, junk, 0)) < 1) {
 206                                 lprintf(9, "SSL_read in client_write:\n");
 207                                 ERR_print_errors_fp(stderr);
 208                         }
 209                 }
 210                 retval =
 211                     SSL_write(CC->ssl, &buf[nbytes - nremain], nremain);
 212                 if (retval < 1) {
 213                         long errval;
 214
 215                         errval = SSL_get_error(CC->ssl, retval);
 216                         if (errval == SSL_ERROR_WANT_READ ||
 217                             errval == SSL_ERROR_WANT_WRITE) {
 218                                 sleep(1);
 219                                 continue;
 220                         }
 221                         lprintf(9, "SSL_write got error %ld, ret %d\n", errval, retval);
 222                         if (retval == -1)
 223                                 lprintf(9, "errno is %d\n", errno);
 224                         endtls();
 225                         client_write(&buf[nbytes - nremain], nremain);
 226                         return;
 227                 }
 228                 nremain -= retval;
 229         }
 230 }
 231
 232
 233 /*
 234  * client_read_ssl() - read data from the encrypted layer.
 235  */
 236 int client_read_ssl(char *buf, int bytes, int timeout)
 237 {
 238 #if 0
 239         fd_set rfds;
 240         struct timeval tv;
 241         int retval;
 242         int s;
 243 #endif
 244         int len, rlen;
 245         char junk[1];
 246
 247         len = 0;
 248         while (len < bytes) {
 249 #if 0
 250                 /*
 251                  * This code is disabled because we don't need it when
 252                  * using blocking reads (which we are). -IO
 253                  */
 254                 FD_ZERO(&rfds);
 255                 s = BIO_get_fd(CC->ssl->rbio, NULL);
 256                 FD_SET(s, &rfds);
 257                 tv.tv_sec = timeout;
 258                 tv.tv_usec = 0;
 259
 260                 retval = select(s + 1, &rfds, NULL, NULL, &tv);
 261
 262                 if (FD_ISSET(s, &rfds) == 0) {
 263                         return (0);
 264                 }
 265
 266 #endif
 267                 if (SSL_want_read(CC->ssl)) {
 268                         if ((SSL_write(CC->ssl, junk, 0)) < 1) {
 269                                 lprintf(9, "SSL_write in client_read:\n");
 270                                 ERR_print_errors_fp(stderr);
 271                         }
 272                 }
 273                 rlen = SSL_read(CC->ssl, &buf[len], bytes - len);
 274                 if (rlen < 1) {
 275                         long errval;
 276
 277                         errval = SSL_get_error(CC->ssl, rlen);
 278                         if (errval == SSL_ERROR_WANT_READ ||
 279                             errval == SSL_ERROR_WANT_WRITE) {
 280                                 sleep(1);
 281                                 continue;
 282                         }
 283                         lprintf(9, "SSL_read got error %ld\n", errval);
 284                         endtls();
 285                         return (client_read_to
 286                                 (&buf[len], bytes - len, timeout));
 287                 }
 288                 len += rlen;
 289         }
 290         return (1);
 291 }
 292
 293
 294 /*
 295  * CtdlStartTLS() starts SSL/TLS encryption for the current session.  It
 296  * must be supplied with pre-generated strings for responses of "ok," "no
 297  * support for TLS," and "error" so that we can use this in any protocol.
 298  */
 299 void CtdlStartTLS(char *ok_response, char *nosup_response,
 300                         char *error_response) {
 301
 302         int retval, bits, alg_bits;
 303
 304         if (!ssl_ctx) {
 305                 cprintf("%s", nosup_response);
 306                 return;
 307         }
 308         if (!(CC->ssl = SSL_new(ssl_ctx))) {
 309                 lprintf(2, "SSL_new failed: %s\n",
 310                                 ERR_reason_error_string(ERR_get_error()));
 311                 cprintf("%s", error_response);
 312                 return;
 313         }
 314         if (!(SSL_set_fd(CC->ssl, CC->client_socket))) {
 315                 lprintf(2, "SSL_set_fd failed: %s\n",
 316                         ERR_reason_error_string(ERR_get_error()));
 317                 SSL_free(CC->ssl);
 318                 CC->ssl = NULL;
 319                 cprintf("%s", error_response);
 320                 return;
 321         }
 322         cprintf("%s", ok_response);
 323         retval = SSL_accept(CC->ssl);
 324         if (retval < 1) {
 325                 /*
 326                  * Can't notify the client of an error here; they will
 327                  * discover the problem at the SSL layer and should
 328                  * revert to unencrypted communications.
 329                  */
 330                 long errval;
 331
 332                 errval = SSL_get_error(CC->ssl, retval);
 333                 lprintf(2, "SSL_accept failed: %s\n",
 334                         ERR_reason_error_string(ERR_get_error()));
 335                 SSL_free(CC->ssl);
 336                 CC->ssl = NULL;
 337                 return;
 338         }
 339         BIO_set_close(CC->ssl->rbio, BIO_NOCLOSE);
 340         bits =
 341             SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl),
 342                                 &alg_bits);
 343         lprintf(3, "SSL/TLS using %s on %s (%d of %d bits)\n",
 344                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 345                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 346                 bits, alg_bits);
 347         CC->redirect_ssl = 1;
 348 }
 349
 350
 351 /*
 352  * cmd_stls() starts SSL/TLS encryption for the current session
 353  */
 354 void cmd_stls(char *params)
 355 {
 356         char ok_response[SIZ];
 357         char nosup_response[SIZ];
 358         char error_response[SIZ];
 359
 360         sprintf(ok_response,
 361                 "%d Begin TLS negotiation now\n",
 362                 CIT_OK);
 363         sprintf(nosup_response,
 364                 "%d TLS not supported here\n",
 365                 ERROR + CMD_NOT_SUPPORTED);
 366         sprintf(error_response,
 367                 "%d TLS negotiation error\n",
 368                 ERROR + INTERNAL_ERROR);
 369
 370         CtdlStartTLS(ok_response, nosup_response, error_response);
 371 }
 372
 373
 374 /*
 375  * cmd_gtls() returns status info about the TLS connection
 376  */
 377 void cmd_gtls(char *params)
 378 {
 379         int bits, alg_bits;
 380
 381         if (!CC->ssl || !CC->redirect_ssl) {
 382                 cprintf("%d Session is not encrypted.\n", ERROR);
 383                 return;
 384         }
 385         bits =
 386             SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl),
 387                                 &alg_bits);
 388         cprintf("%d %s|%s|%d|%d\n", CIT_OK,
 389                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 390                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 391                 alg_bits, bits);
 392 }
 393
 394
 395 /*
 396  * endtls() shuts down the TLS connection
 397  *
 398  * WARNING:  This may make your session vulnerable to a known plaintext
 399  * attack in the current implmentation.
 400  */
 401 void endtls(void)
 402 {
 403         lprintf(7, "Ending SSL/TLS\n");
 404
 405         if (!CC->ssl) {
 406                 CC->redirect_ssl = 0;
 407                 return;
 408         }
 409
 410         SSL_shutdown(CC->ssl);
 411         SSL_free(CC->ssl);
 412         CC->ssl = NULL;
 413         CC->redirect_ssl = 0;
 414 }
 415
 416
 417 /*
 418  * ssl_lock() callback for OpenSSL mutex locks
 419  */
 420 void ssl_lock(int mode, int n, const char *file, int line)
 421 {
 422         if (mode & CRYPTO_LOCK)
 423                 pthread_mutex_lock(SSLCritters[n]);
 424         else
 425                 pthread_mutex_unlock(SSLCritters[n]);
 426 }
 427 #endif                          /* HAVE_OPENSSL */