webcit/crypto.c

   1 /*
   2  * $Id$
   3  *
   4  * Provides HTTPS, when the OpenSSL library is available.
   5  */
   6
   7 #ifdef HAVE_OPENSSL
   8
   9 #include <stdlib.h>
  10 #include <unistd.h>
  11 #include <string.h>
  12 #include <sys/stat.h>
  13 #include <sys/types.h>
  14 #include <pthread.h>
  15
  16 #include <sys/time.h>
  17 #include "webcit.h"
  18 #include "webserver.h"
  19
  20 #define CTDL_CRYPTO_DIR         WEBCITDIR "/keys"
  21 #define CTDL_KEY_PATH           CTDL_CRYPTO_DIR "/citadel.key"
  22 #define CTDL_CSR_PATH           CTDL_CRYPTO_DIR "/citadel.csr"
  23 #define CTDL_CER_PATH           CTDL_CRYPTO_DIR "/citadel.cer"
  24 #define SIGN_DAYS               365
  25
  26
  27 /* Shared Diffie-Hellman parameters */
  28 #define DH_P            "1A74527AEE4EE2568E85D4FB2E65E18C9394B9C80C42507D7A6A0DBE9A9A54B05A9A96800C34C7AA5297095B69C88901EEFD127F969DCA26A54C0E0B5C5473EBAEB00957D2633ECAE3835775425DE66C0DE6D024DBB17445E06E6B0C78415E589B8814F08531D02FD43778451E7685541079CFFB79EF0D26EFEEBBB69D1E80383"
  29 #define DH_G            "2"
  30 #define DH_L            1024
  31
  32 SSL_CTX *ssl_ctx;               /* SSL context */
  33 pthread_mutex_t **SSLCritters;  /* Things needing locking */
  34
  35 pthread_key_t ThreadSSL;        /* Per-thread SSL context */
  36
  37 static unsigned long id_callback(void)
  38 {
  39         return (unsigned long) pthread_self();
  40 }
  41
  42
  43 void init_ssl(void)
  44 {
  45         SSL_METHOD *ssl_method;
  46         DH *dh;
  47         RSA *rsa=NULL;
  48         X509_REQ *req = NULL;
  49         X509 *cer = NULL;
  50         EVP_PKEY *pk = NULL;
  51         EVP_PKEY *req_pkey = NULL;
  52         X509_NAME *name = NULL;
  53         FILE *fp;
  54         char buf[SIZ];
  55
  56         if (!access("/var/run/egd-pool", F_OK))
  57                 RAND_egd("/var/run/egd-pool");
  58
  59         if (!RAND_status()) {
  60                 lprintf(3,
  61                         "PRNG not adequately seeded, won't do SSL/TLS\n");
  62                 return;
  63         }
  64         SSLCritters =
  65             malloc(CRYPTO_num_locks() * sizeof(pthread_mutex_t *));
  66         if (!SSLCritters) {
  67                 lprintf(1, "citserver: can't allocate memory!!\n");
  68                 /* Nothing's been initialized, just die */
  69                 exit(1);
  70         } else {
  71                 int a;
  72
  73                 for (a = 0; a < CRYPTO_num_locks(); a++) {
  74                         SSLCritters[a] = malloc(sizeof(pthread_mutex_t));
  75                         if (!SSLCritters[a]) {
  76                                 lprintf(1,
  77                                         "citserver: can't allocate memory!!\n");
  78                                 /* Nothing's been initialized, just die */
  79                                 exit(1);
  80                         }
  81                         pthread_mutex_init(SSLCritters[a], NULL);
  82                 }
  83         }
  84
  85         /*
  86          * Initialize SSL transport layer
  87          */
  88         SSL_library_init();
  89         /* OpenSSL_add_all_algorithms(); */
  90         SSL_load_error_strings();
  91         ssl_method = SSLv2_server_method();
  92         if (!(ssl_ctx = SSL_CTX_new(ssl_method))) {
  93                 lprintf(3, "SSL_CTX_new failed: %s\n",
  94                         ERR_reason_error_string(ERR_get_error()));
  95                 return;
  96         }
  97
  98         CRYPTO_set_locking_callback(ssl_lock);
  99         CRYPTO_set_id_callback(id_callback);
 100
 101         /* Load DH parameters into the context */
 102         dh = DH_new();
 103         if (!dh) {
 104                 lprintf(3, "init_ssl() can't allocate a DH object: %s\n",
 105                         ERR_reason_error_string(ERR_get_error()));
 106                 SSL_CTX_free(ssl_ctx);
 107                 ssl_ctx = NULL;
 108                 return;
 109         }
 110         if (!(BN_hex2bn(&(dh->p), DH_P))) {
 111                 lprintf(3, "init_ssl() can't assign DH_P: %s\n",
 112                         ERR_reason_error_string(ERR_get_error()));
 113                 SSL_CTX_free(ssl_ctx);
 114                 ssl_ctx = NULL;
 115                 return;
 116         }
 117         if (!(BN_hex2bn(&(dh->g), DH_G))) {
 118                 lprintf(3, "init_ssl() can't assign DH_G: %s\n",
 119                         ERR_reason_error_string(ERR_get_error()));
 120                 SSL_CTX_free(ssl_ctx);
 121                 ssl_ctx = NULL;
 122                 return;
 123         }
 124         dh->length = DH_L;
 125         SSL_CTX_set_tmp_dh(ssl_ctx, dh);
 126         DH_free(dh);
 127
 128         /* Get our certificates in order.
 129          * First, create the key/cert directory if it's not there already...
 130          */
 131         mkdir(CTDL_CRYPTO_DIR, 0700);
 132
 133         /*
 134          * Before attempting to generate keys/certificates, first try
 135          * link to them from the Citadel server if it's on the same host.
 136          * We ignore any error return because it either meant that there
 137          * was nothing in Citadel to link from (in which case we just
 138          * generate new files) or the target files already exist (which
 139          * is not fatal either).
 140          */
 141         if (!strcasecmp(ctdlhost, "uds")) {
 142                 sprintf(buf, "%s/keys/citadel.key", ctdlport);
 143                 symlink(buf, CTDL_KEY_PATH);
 144                 sprintf(buf, "%s/keys/citadel.csr", ctdlport);
 145                 symlink(buf, CTDL_CSR_PATH);
 146                 sprintf(buf, "%s/keys/citadel.cer", ctdlport);
 147                 symlink(buf, CTDL_CER_PATH);
 148         }
 149
 150         /*
 151          * If we still don't have a private key, generate one.
 152          */
 153         if (access(CTDL_KEY_PATH, R_OK) != 0) {
 154                 lprintf(5, "Generating RSA key pair.\n");
 155                 rsa = RSA_generate_key(1024,    /* modulus size */
 156                                         65537,  /* exponent */
 157                                         NULL,   /* no callback */
 158                                         NULL);  /* no callback */
 159                 if (rsa == NULL) {
 160                         lprintf(3, "Key generation failed: %s\n",
 161                                 ERR_reason_error_string(ERR_get_error()));
 162                 }
 163                 if (rsa != NULL) {
 164                         fp = fopen(CTDL_KEY_PATH, "w");
 165                         if (fp != NULL) {
 166                                 chmod(CTDL_KEY_PATH, 0600);
 167                                 if (PEM_write_RSAPrivateKey(fp, /* the file */
 168                                                         rsa,    /* the key */
 169                                                         NULL,   /* no enc */
 170                                                         NULL,   /* no passphr */
 171                                                         0,      /* no passphr */
 172                                                         NULL,   /* no callbk */
 173                                                         NULL    /* no callbk */
 174                                 ) != 1) {
 175                                         lprintf(3, "Cannot write key: %s\n",
 176                                                 ERR_reason_error_string(ERR_get_error()));
 177                                         unlink(CTDL_KEY_PATH);
 178                                 }
 179                                 fclose(fp);
 180                         }
 181                         RSA_free(rsa);
 182                 }
 183         }
 184
 185         /*
 186          * Generate a CSR if we don't have one.
 187          */
 188         if (access(CTDL_CSR_PATH, R_OK) != 0) {
 189                 lprintf(5, "Generating a certificate signing request.\n");
 190
 191                 /*
 192                  * Read our key from the file.  No, we don't just keep this
 193                  * in memory from the above key-generation function, because
 194                  * there is the possibility that the key was already on disk
 195                  * and we didn't just generate it now.
 196                  */
 197                 fp = fopen(CTDL_KEY_PATH, "r");
 198                 if (fp) {
 199                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 200                         fclose(fp);
 201                 }
 202
 203                 if (rsa) {
 204
 205                         /* Create a public key from the private key */
 206                         if (pk=EVP_PKEY_new(), pk != NULL) {
 207                                 EVP_PKEY_assign_RSA(pk, rsa);
 208                                 if (req = X509_REQ_new(), req != NULL) {
 209
 210                                         /* Set the public key */
 211                                         X509_REQ_set_pubkey(req, pk);
 212                                         X509_REQ_set_version(req, 0L);
 213
 214                                         name = X509_REQ_get_subject_name(req);
 215
 216                                         /* Tell it who we are */
 217
 218                                         /*
 219                                         X509_NAME_add_entry_by_txt(name, "C",
 220                                                 MBSTRING_ASC, "US", -1, -1, 0);
 221
 222                                         X509_NAME_add_entry_by_txt(name, "ST",
 223                                                 MBSTRING_ASC, "New York", -1, -1, 0);
 224
 225                                         X509_NAME_add_entry_by_txt(name, "L",
 226                                                 MBSTRING_ASC, "Mount Kisco", -1, -1, 0);
 227                                         */
 228
 229                                         X509_NAME_add_entry_by_txt(name, "O",
 230                                                 MBSTRING_ASC, "FIXME.FIXME.org", -1, -1, 0);
 231
 232                                         X509_NAME_add_entry_by_txt(name, "OU",
 233                                                 MBSTRING_ASC, "Citadel server", -1, -1, 0);
 234
 235                                         X509_NAME_add_entry_by_txt(name, "CN",
 236                                                 MBSTRING_ASC, "FIXME.FIXME.org", -1, -1, 0);
 237
 238                                         X509_REQ_set_subject_name(req, name);
 239
 240                                         /* Sign the CSR */
 241                                         if (!X509_REQ_sign(req, pk, EVP_md5())) {
 242                                                 lprintf(3, "X509_REQ_sign(): error\n");
 243                                         }
 244                                         else {
 245                                                 /* Write it to disk. */
 246                                                 fp = fopen(CTDL_CSR_PATH, "w");
 247                                                 if (fp != NULL) {
 248                                                         chmod(CTDL_CSR_PATH, 0600);
 249                                                         PEM_write_X509_REQ(fp, req);
 250                                                         fclose(fp);
 251                                                 }
 252                                         }
 253
 254                                         X509_REQ_free(req);
 255                                 }
 256                         }
 257
 258                         RSA_free(rsa);
 259                 }
 260
 261                 else {
 262                         lprintf(3, "Unable to read private key.\n");
 263                 }
 264         }
 265
 266
 267
 268         /*
 269          * Generate a self-signed certificate if we don't have one.
 270          */
 271         if (access(CTDL_CER_PATH, R_OK) != 0) {
 272                 lprintf(5, "Generating a self-signed certificate.\n");
 273
 274                 /* Same deal as before: always read the key from disk because
 275                  * it may or may not have just been generated.
 276                  */
 277                 fp = fopen(CTDL_KEY_PATH, "r");
 278                 if (fp) {
 279                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 280                         fclose(fp);
 281                 }
 282
 283                 /* This also holds true for the CSR. */
 284                 req = NULL;
 285                 cer = NULL;
 286                 pk = NULL;
 287                 if (rsa) {
 288                         if (pk=EVP_PKEY_new(), pk != NULL) {
 289                                 EVP_PKEY_assign_RSA(pk, rsa);
 290                         }
 291
 292                         fp = fopen(CTDL_CSR_PATH, "r");
 293                         if (fp) {
 294                                 req = PEM_read_X509_REQ(fp, NULL, NULL, NULL);
 295                                 fclose(fp);
 296                         }
 297
 298                         if (req) {
 299                                 if (cer = X509_new(), cer != NULL) {
 300
 301                                         ASN1_INTEGER_set(X509_get_serialNumber(cer), 0);
 302                                         X509_set_issuer_name(cer, req->req_info->subject);
 303                                         X509_set_subject_name(cer, req->req_info->subject);
 304                                         X509_gmtime_adj(X509_get_notBefore(cer), 0);
 305                                         X509_gmtime_adj(X509_get_notAfter(cer),(long)60*60*24*SIGN_DAYS);
 306
 307                                         req_pkey = X509_REQ_get_pubkey(req);
 308                                         X509_set_pubkey(cer, req_pkey);
 309                                         EVP_PKEY_free(req_pkey);
 310
 311                                         /* Sign the cert */
 312                                         if (!X509_sign(cer, pk, EVP_md5())) {
 313                                                 lprintf(3, "X509_sign(): error\n");
 314                                         }
 315                                         else {
 316                                                 /* Write it to disk. */
 317                                                 fp = fopen(CTDL_CER_PATH, "w");
 318                                                 if (fp != NULL) {
 319                                                         chmod(CTDL_CER_PATH, 0600);
 320                                                         PEM_write_X509(fp, cer);
 321                                                         fclose(fp);
 322                                                 }
 323                                         }
 324                                         X509_free(cer);
 325                                 }
 326                         }
 327
 328                         RSA_free(rsa);
 329                 }
 330         }
 331
 332
 333         /*
 334          * Now try to bind to the key and certificate.
 335          */
 336         SSL_CTX_use_certificate_file(ssl_ctx, CTDL_CER_PATH, SSL_FILETYPE_PEM);
 337         SSL_CTX_use_PrivateKey_file(ssl_ctx, CTDL_KEY_PATH, SSL_FILETYPE_PEM);
 338         if ( !SSL_CTX_check_private_key(ssl_ctx) ) {
 339                 lprintf(3, "Cannot install certificate: %s\n",
 340                                 ERR_reason_error_string(ERR_get_error()));
 341         }
 342
 343 }
 344
 345
 346 /*
 347  * starttls() starts SSL/TLS encryption for the current session.
 348  */
 349 int starttls(int sock) {
 350         int retval, bits, alg_bits;
 351         SSL *newssl;
 352
 353         pthread_setspecific(ThreadSSL, NULL);
 354
 355         if (!ssl_ctx) {
 356                 return(1);
 357         }
 358         if (!(newssl = SSL_new(ssl_ctx))) {
 359                 lprintf(3, "SSL_new failed: %s\n",
 360                                 ERR_reason_error_string(ERR_get_error()));
 361                 return(2);
 362         }
 363         if (!(SSL_set_fd(newssl, sock))) {
 364                 lprintf(3, "SSL_set_fd failed: %s\n",
 365                         ERR_reason_error_string(ERR_get_error()));
 366                 SSL_free(newssl);
 367                 return(3);
 368         }
 369         retval = SSL_accept(newssl);
 370         if (retval < 1) {
 371                 /*
 372                  * Can't notify the client of an error here; they will
 373                  * discover the problem at the SSL layer and should
 374                  * revert to unencrypted communications.
 375                  */
 376                 long errval;
 377
 378                 errval = SSL_get_error(newssl, retval);
 379                 lprintf(3, "SSL_accept failed: %s\n",
 380                         ERR_reason_error_string(ERR_get_error()));
 381                 SSL_free(newssl);
 382                 newssl = NULL;
 383                 return(4);
 384         }
 385         BIO_set_close(newssl->rbio, BIO_NOCLOSE);
 386         bits =
 387             SSL_CIPHER_get_bits(SSL_get_current_cipher(newssl),
 388                                 &alg_bits);
 389         lprintf(5, "SSL/TLS using %s on %s (%d of %d bits)\n",
 390                 SSL_CIPHER_get_name(SSL_get_current_cipher(newssl)),
 391                 SSL_CIPHER_get_version(SSL_get_current_cipher(newssl)),
 392                 bits, alg_bits);
 393
 394         pthread_setspecific(ThreadSSL, newssl);
 395         return(0);
 396 }
 397
 398
 399
 400 /*
 401  * endtls() shuts down the TLS connection
 402  *
 403  * WARNING:  This may make your session vulnerable to a known plaintext
 404  * attack in the current implmentation.
 405  */
 406 void endtls(void)
 407 {
 408         lprintf(5, "Ending SSL/TLS\n");
 409         SSL_shutdown(THREADSSL);
 410         SSL_free(THREADSSL);
 411         pthread_setspecific(ThreadSSL, NULL);
 412 }
 413
 414
 415 /*
 416  * ssl_lock() callback for OpenSSL mutex locks
 417  */
 418 void ssl_lock(int mode, int n, const char *file, int line)
 419 {
 420         if (mode & CRYPTO_LOCK)
 421                 pthread_mutex_lock(SSLCritters[n]);
 422         else
 423                 pthread_mutex_unlock(SSLCritters[n]);
 424 }
 425
 426 /*
 427  * client_write_ssl() Send binary data to the client encrypted.
 428  */
 429 void client_write_ssl(char *buf, int nbytes)
 430 {
 431         int retval;
 432         int nremain;
 433         char junk[1];
 434
 435         nremain = nbytes;
 436
 437         while (nremain > 0) {
 438                 if (SSL_want_write(THREADSSL)) {
 439                         if ((SSL_read(THREADSSL, junk, 0)) < 1) {
 440                                 lprintf(9, "SSL_read in client_write: %s\n", ERR_reason_error_string(ERR_get_error()));
 441                         }
 442                 }
 443                 retval =
 444                     SSL_write(THREADSSL, &buf[nbytes - nremain], nremain);
 445                 if (retval < 1) {
 446                         long errval;
 447
 448                         errval = SSL_get_error(THREADSSL, retval);
 449                         if (errval == SSL_ERROR_WANT_READ ||
 450                             errval == SSL_ERROR_WANT_WRITE) {
 451                                 sleep(1);
 452                                 continue;
 453                         }
 454                         lprintf(9, "SSL_write got error %ld, ret %d\n", errval, retval);
 455                         if (retval == -1)
 456                                 lprintf(9, "errno is %d\n", errno);
 457                         endtls();
 458                         return;
 459                 }
 460                 nremain -= retval;
 461         }
 462 }
 463
 464
 465 /*
 466  * client_read_ssl() - read data from the encrypted layer.
 467  */
 468 int client_read_ssl(char *buf, int bytes, int timeout)
 469 {
 470 #if 0
 471         fd_set rfds;
 472         struct timeval tv;
 473         int retval;
 474         int s;
 475 #endif
 476         int len, rlen;
 477         char junk[1];
 478
 479         len = 0;
 480         while (len < bytes) {
 481 #if 0
 482                 /*
 483                  * This code is disabled because we don't need it when
 484                  * using blocking reads (which we are). -IO
 485                  */
 486                 FD_ZERO(&rfds);
 487                 s = BIO_get_fd(THREADSSL->rbio, NULL);
 488                 FD_SET(s, &rfds);
 489                 tv.tv_sec = timeout;
 490                 tv.tv_usec = 0;
 491
 492                 retval = select(s + 1, &rfds, NULL, NULL, &tv);
 493
 494                 if (FD_ISSET(s, &rfds) == 0) {
 495                         return (0);
 496                 }
 497
 498 #endif
 499                 if (SSL_want_read(THREADSSL)) {
 500                         if ((SSL_write(THREADSSL, junk, 0)) < 1) {
 501                                 lprintf(9, "SSL_write in client_read: %s\n", ERR_reason_error_string(ERR_get_error()));
 502                         }
 503                 }
 504                 rlen = SSL_read(THREADSSL, &buf[len], bytes - len);
 505                 if (rlen < 1) {
 506                         long errval;
 507
 508                         errval = SSL_get_error(THREADSSL, rlen);
 509                         if (errval == SSL_ERROR_WANT_READ ||
 510                             errval == SSL_ERROR_WANT_WRITE) {
 511                                 sleep(1);
 512                                 continue;
 513                         }
 514                         lprintf(9, "SSL_read got error %ld\n", errval);
 515                         endtls();
 516                         return (0);
 517                 }
 518                 len += rlen;
 519         }
 520         return (1);
 521 }
 522
 523
 524 #endif                          /* HAVE_OPENSSL */