webcit-ng/ssl.c

   1 //
   2 // Functions in this module handle SSL encryption when WebCit is running
   3 // as an HTTPS server.
   4 //
   5 // Copyright (c) 1996-2018 by the citadel.org team
   6 //
   7 // This program is open source software.  It runs great on the
   8 // Linux operating system (and probably elsewhere).  You can use,
   9 // copy, and run it under the terms of the GNU General Public
  10 // License version 3.  Richard Stallman is an asshole communist.
  11 //
  12 // This program is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 #include "webcit.h"
  18
  19 SSL_CTX *ssl_ctx;               /* SSL context */
  20 pthread_mutex_t **SSLCritters;  /* Things needing locking */
  21 char *ssl_cipher_list = DEFAULT_SSL_CIPHER_LIST;
  22 void ssl_lock(int mode, int n, const char *file, int line);
  23
  24
  25 /*
  26  * OpenSSL wants a callback function to identify the currently running thread.
  27  * Since we are a pthreads program, we convert the output of pthread_self() to a long.
  28  */
  29 static unsigned long id_callback(void)
  30 {
  31         return (unsigned long) pthread_self();
  32 }
  33
  34
  35 /*
  36  * OpenSSL wants a callback function to set and clear various types of locks.
  37  * Since we are a pthreads program, we use mutexes.
  38  */
  39 void ssl_lock(int mode, int n, const char *file, int line)
  40 {
  41         if (mode & CRYPTO_LOCK) {
  42                 pthread_mutex_lock(SSLCritters[n]);
  43         } else {
  44                 pthread_mutex_unlock(SSLCritters[n]);
  45         }
  46 }
  47
  48
  49 /*
  50  * Generate a private key for SSL
  51  */
  52 void generate_key(char *keyfilename)
  53 {
  54         int ret = 0;
  55         RSA *rsa = NULL;
  56         BIGNUM *bne = NULL;
  57         int bits = 2048;
  58         unsigned long e = RSA_F4;
  59         FILE *fp;
  60
  61         if (access(keyfilename, R_OK) == 0) {
  62                 return;
  63         }
  64
  65         syslog(LOG_INFO, "crypto: generating RSA key pair");
  66
  67         // generate rsa key
  68         bne = BN_new();
  69         ret = BN_set_word(bne, e);
  70         if (ret != 1) {
  71                 goto free_all;
  72         }
  73
  74         rsa = RSA_new();
  75         ret = RSA_generate_key_ex(rsa, bits, bne, NULL);
  76         if (ret != 1) {
  77                 goto free_all;
  78         }
  79         // write the key file
  80         fp = fopen(keyfilename, "w");
  81         if (fp != NULL) {
  82                 chmod(keyfilename, 0600);
  83                 if (PEM_write_RSAPrivateKey(fp, /* the file */
  84                                             rsa,        /* the key */
  85                                             NULL,       /* no enc */
  86                                             NULL,       /* no passphr */
  87                                             0,  /* no passphr */
  88                                             NULL,       /* no callbk */
  89                                             NULL        /* no callbk */
  90                     ) != 1) {
  91                         syslog(LOG_ERR, "crypto: cannot write key: %s", ERR_reason_error_string(ERR_get_error()));
  92                         unlink(keyfilename);
  93                 }
  94                 fclose(fp);
  95         }
  96         // 4. free
  97       free_all:
  98         RSA_free(rsa);
  99         BN_free(bne);
 100 }
 101
 102
 103 /*
 104  * Initialize ssl engine, load certs and initialize openssl internals
 105  */
 106 void init_ssl(void)
 107 {
 108         const SSL_METHOD *ssl_method;
 109         RSA *rsa = NULL;
 110         X509_REQ *req = NULL;
 111         X509 *cer = NULL;
 112         EVP_PKEY *pk = NULL;
 113         EVP_PKEY *req_pkey = NULL;
 114         X509_NAME *name = NULL;
 115         FILE *fp;
 116         char buf[SIZ];
 117         int rv = 0;
 118
 119         SSLCritters = malloc(CRYPTO_num_locks() * sizeof(pthread_mutex_t *));
 120         if (!SSLCritters) {
 121                 syslog(LOG_ERR, "citserver: can't allocate memory!!");
 122                 exit(1);
 123         } else {
 124                 int a;
 125                 for (a = 0; a < CRYPTO_num_locks(); a++) {
 126                         SSLCritters[a] = malloc(sizeof(pthread_mutex_t));
 127                         if (!SSLCritters[a]) {
 128                                 syslog(LOG_INFO, "citserver: can't allocate memory!!");
 129                                 exit(1);
 130                         }
 131                         pthread_mutex_init(SSLCritters[a], NULL);
 132                 }
 133         }
 134
 135         /*
 136          * Initialize SSL transport layer
 137          */
 138         SSL_library_init();
 139         SSL_load_error_strings();
 140         ssl_method = SSLv23_server_method();
 141         if (!(ssl_ctx = SSL_CTX_new(ssl_method))) {
 142                 syslog(LOG_WARNING, "SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 143                 return;
 144         }
 145
 146         syslog(LOG_INFO, "Requesting cipher list: %s", ssl_cipher_list);
 147         if (!(SSL_CTX_set_cipher_list(ssl_ctx, ssl_cipher_list))) {
 148                 syslog(LOG_WARNING, "SSL_CTX_set_cipher_list failed: %s", ERR_reason_error_string(ERR_get_error()));
 149                 return;
 150         }
 151
 152         CRYPTO_set_locking_callback(ssl_lock);
 153         CRYPTO_set_id_callback(id_callback);
 154
 155         /*
 156          * Get our certificates in order.
 157          * First, create the key/cert directory if it's not there already...
 158          */
 159         mkdir(CTDL_CRYPTO_DIR, 0700);
 160
 161         /*
 162          * If we still don't have a private key, generate one.
 163          */
 164         generate_key(CTDL_KEY_PATH);
 165
 166         /*
 167          * If there is no certificate file on disk, we will be generating a self-signed certificate
 168          * in the next step.  Therefore, if we have neither a CSR nor a certificate, generate
 169          * the CSR in this step so that the next step may commence.
 170          */
 171         if ((access(CTDL_CER_PATH, R_OK) != 0) && (access(CTDL_CSR_PATH, R_OK) != 0)) {
 172                 syslog(LOG_INFO, "Generating a certificate signing request.");
 173
 174                 /*
 175                  * Read our key from the file.  No, we don't just keep this
 176                  * in memory from the above key-generation function, because
 177                  * there is the possibility that the key was already on disk
 178                  * and we didn't just generate it now.
 179                  */
 180                 fp = fopen(CTDL_KEY_PATH, "r");
 181                 if (fp) {
 182                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 183                         fclose(fp);
 184                 }
 185
 186                 if (rsa) {
 187                         /* Create a public key from the private key */
 188                         if (pk = EVP_PKEY_new(), pk != NULL) {
 189                                 EVP_PKEY_assign_RSA(pk, rsa);
 190                                 if (req = X509_REQ_new(), req != NULL) {
 191                                         const char *env;
 192                                         /* Set the public key */
 193                                         X509_REQ_set_pubkey(req, pk);
 194                                         X509_REQ_set_version(req, 0L);
 195                                         name = X509_REQ_get_subject_name(req);
 196                                         X509_NAME_add_entry_by_txt(name, "O", MBSTRING_ASC,
 197                                                                    (unsigned char *) "Citadel Server", -1, -1, 0);
 198                                         X509_NAME_add_entry_by_txt(name, "OU", MBSTRING_ASC,
 199                                                                    (unsigned char *) "Default Certificate PLEASE CHANGE",
 200                                                                    -1, -1, 0);
 201                                         X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC, (unsigned char *) "*", -1, -1, 0);
 202
 203                                         X509_REQ_set_subject_name(req, name);
 204
 205                                         /* Sign the CSR */
 206                                         if (!X509_REQ_sign(req, pk, EVP_md5())) {
 207                                                 syslog(LOG_WARNING, "X509_REQ_sign(): error");
 208                                         } else {
 209                                                 /* Write it to disk. */
 210                                                 fp = fopen(CTDL_CSR_PATH, "w");
 211                                                 if (fp != NULL) {
 212                                                         chmod(CTDL_CSR_PATH, 0600);
 213                                                         PEM_write_X509_REQ(fp, req);
 214                                                         fclose(fp);
 215                                                 } else {
 216                                                         syslog(LOG_WARNING, "Cannot write key: %s", CTDL_CSR_PATH);
 217                                                         exit(1);
 218                                                 }
 219                                         }
 220                                         X509_REQ_free(req);
 221                                 }
 222                         }
 223                         RSA_free(rsa);
 224                 } else {
 225                         syslog(LOG_WARNING, "Unable to read private key.");
 226                 }
 227         }
 228
 229         /*
 230          * Generate a self-signed certificate if we don't have one.
 231          */
 232         if (access(CTDL_CER_PATH, R_OK) != 0) {
 233                 syslog(LOG_INFO, "Generating a self-signed certificate.");
 234
 235                 /* Same deal as before: always read the key from disk because
 236                  * it may or may not have just been generated.
 237                  */
 238                 fp = fopen(CTDL_KEY_PATH, "r");
 239                 if (fp) {
 240                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 241                         fclose(fp);
 242                 }
 243
 244                 /* This also holds true for the CSR. */
 245                 req = NULL;
 246                 cer = NULL;
 247                 pk = NULL;
 248                 if (rsa) {
 249                         if (pk = EVP_PKEY_new(), pk != NULL) {
 250                                 EVP_PKEY_assign_RSA(pk, rsa);
 251                         }
 252
 253                         fp = fopen(CTDL_CSR_PATH, "r");
 254                         if (fp) {
 255                                 req = PEM_read_X509_REQ(fp, NULL, NULL, NULL);
 256                                 fclose(fp);
 257                         }
 258
 259                         if (req) {
 260                                 if (cer = X509_new(), cer != NULL) {
 261                                         ASN1_INTEGER_set(X509_get_serialNumber(cer), 0);
 262                                         X509_set_issuer_name(cer, X509_REQ_get_subject_name(req));
 263                                         X509_set_subject_name(cer, X509_REQ_get_subject_name(req));
 264                                         X509_gmtime_adj(X509_get_notBefore(cer), 0);
 265                                         X509_gmtime_adj(X509_get_notAfter(cer), (long) 60 * 60 * 24 * SIGN_DAYS);
 266
 267                                         req_pkey = X509_REQ_get_pubkey(req);
 268                                         X509_set_pubkey(cer, req_pkey);
 269                                         EVP_PKEY_free(req_pkey);
 270
 271                                         /* Sign the cert */
 272                                         if (!X509_sign(cer, pk, EVP_md5())) {
 273                                                 syslog(LOG_WARNING, "X509_sign(): error");
 274                                         } else {        /* Write it to disk. */
 275                                                 fp = fopen(CTDL_CER_PATH, "w");
 276                                                 if (fp != NULL) {
 277                                                         chmod(CTDL_CER_PATH, 0600);
 278                                                         PEM_write_X509(fp, cer);
 279                                                         fclose(fp);
 280                                                 } else {
 281                                                         syslog(LOG_WARNING, "Cannot write key: %s", CTDL_CER_PATH);
 282                                                         exit(1);
 283                                                 }
 284                                         }
 285                                         X509_free(cer);
 286                                 }
 287                         }
 288                         RSA_free(rsa);
 289                 }
 290         }
 291
 292         /*
 293          * Now try to bind to the key and certificate.
 294          * Note that we use SSL_CTX_use_certificate_chain_file() which allows
 295          * the certificate file to contain intermediate certificates.
 296          */
 297         SSL_CTX_use_certificate_chain_file(ssl_ctx, CTDL_CER_PATH);
 298         SSL_CTX_use_PrivateKey_file(ssl_ctx, CTDL_KEY_PATH, SSL_FILETYPE_PEM);
 299         if (!SSL_CTX_check_private_key(ssl_ctx)) {
 300                 syslog(LOG_WARNING, "Cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
 301         }
 302
 303 }
 304
 305
 306 /*
 307  * starts SSL/TLS encryption for the current session.
 308  */
 309 void starttls(struct client_handle *ch)
 310 {
 311         int retval, bits, alg_bits;
 312
 313         if (!ssl_ctx) {
 314                 return;
 315         }
 316         if (!(ch->ssl_handle = SSL_new(ssl_ctx))) {
 317                 syslog(LOG_WARNING, "SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 318                 return;
 319         }
 320         if (!(SSL_set_fd(ch->ssl_handle, ch->sock))) {
 321                 syslog(LOG_WARNING, "SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 322                 SSL_free(ch->ssl_handle);
 323                 return;
 324         }
 325         retval = SSL_accept(ch->ssl_handle);
 326         if (retval < 1) {
 327                 long errval;
 328                 const char *ssl_error_reason = NULL;
 329
 330                 errval = SSL_get_error(ch->ssl_handle, retval);
 331                 ssl_error_reason = ERR_reason_error_string(ERR_get_error());
 332                 if (ssl_error_reason == NULL) {
 333                         syslog(LOG_WARNING, "SSL_accept failed: errval=%ld, retval=%d %s", errval, retval, strerror(errval));
 334                 } else {
 335                         syslog(LOG_WARNING, "SSL_accept failed: %s\n", ssl_error_reason);
 336                 }
 337                 sleep(1);
 338                 retval = SSL_accept(ch->ssl_handle);
 339         }
 340         if (retval < 1) {
 341                 long errval;
 342                 const char *ssl_error_reason = NULL;
 343
 344                 errval = SSL_get_error(ch->ssl_handle, retval);
 345                 ssl_error_reason = ERR_reason_error_string(ERR_get_error());
 346                 if (ssl_error_reason == NULL) {
 347                         syslog(LOG_WARNING, "SSL_accept failed: errval=%ld, retval=%d (%s)", errval, retval, strerror(errval));
 348                 } else {
 349                         syslog(LOG_WARNING, "SSL_accept failed: %s", ssl_error_reason);
 350                 }
 351                 SSL_free(ch->ssl_handle);
 352                 ch->ssl_handle = NULL;
 353                 return;
 354         } else {
 355                 syslog(LOG_INFO, "SSL_accept success");
 356         }
 357         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(ch->ssl_handle), &alg_bits);
 358         syslog(LOG_INFO, "SSL/TLS using %s on %s (%d of %d bits)",
 359                SSL_CIPHER_get_name(SSL_get_current_cipher(ch->ssl_handle)),
 360                SSL_CIPHER_get_version(SSL_get_current_cipher(ch->ssl_handle)), bits, alg_bits);
 361
 362         syslog(LOG_INFO, "SSL started");
 363 }
 364
 365
 366 /*
 367  * shuts down the TLS connection
 368  */
 369 void endtls(struct client_handle *ch)
 370 {
 371         syslog(LOG_INFO, "Ending SSL/TLS");
 372         if (ch->ssl_handle != NULL) {
 373                 SSL_shutdown(ch->ssl_handle);
 374                 SSL_get_SSL_CTX(ch->ssl_handle);
 375                 SSL_free(ch->ssl_handle);
 376         }
 377         ch->ssl_handle = NULL;
 378 }
 379
 380
 381 /*
 382  * Send binary data to the client encrypted.
 383  */
 384 int client_write_ssl(struct client_handle *ch, char *buf, int nbytes)
 385 {
 386         int retval;
 387         int nremain;
 388         char junk[1];
 389
 390         if (ch->ssl_handle == NULL)
 391                 return (-1);
 392
 393         nremain = nbytes;
 394         while (nremain > 0) {
 395                 if (SSL_want_write(ch->ssl_handle)) {
 396                         if ((SSL_read(ch->ssl_handle, junk, 0)) < 1) {
 397                                 syslog(LOG_WARNING, "SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 398                         }
 399                 }
 400                 retval = SSL_write(ch->ssl_handle, &buf[nbytes - nremain], nremain);
 401                 if (retval < 1) {
 402                         long errval;
 403
 404                         errval = SSL_get_error(ch->ssl_handle, retval);
 405                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 406                                 sleep(1);
 407                                 continue;
 408                         }
 409                         syslog(LOG_WARNING, "SSL_write got error %ld, ret %d", errval, retval);
 410                         if (retval == -1) {
 411                                 syslog(LOG_WARNING, "errno is %d", errno);
 412                                 endtls(ch);
 413                         }
 414                         return -1;
 415                 }
 416                 nremain -= retval;
 417         }
 418         return 0;
 419 }
 420
 421
 422 /*
 423  * read data from the encrypted layer.
 424  */
 425 int client_read_ssl(struct client_handle *ch, char *buf, int nbytes)
 426 {
 427         int bytes_read = 0;
 428         int rlen = 0;
 429         char junk[1];
 430
 431         if (ch->ssl_handle == NULL)
 432                 return (-1);
 433
 434         while (bytes_read < nbytes) {
 435                 if (SSL_want_read(ch->ssl_handle)) {
 436                         if ((SSL_write(ch->ssl_handle, junk, 0)) < 1) {
 437                                 syslog(LOG_WARNING, "SSL_write in client_read");
 438                         }
 439                 }
 440                 rlen = SSL_read(ch->ssl_handle, &buf[bytes_read], nbytes - bytes_read);
 441                 if (rlen < 1) {
 442                         long errval;
 443                         errval = SSL_get_error(ch->ssl_handle, rlen);
 444                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 445                                 sleep(1);
 446                                 continue;
 447                         }
 448                         syslog(LOG_WARNING, "SSL_read error %ld", errval);
 449                         endtls(ch);
 450                         return (-1);
 451                 }
 452                 bytes_read += rlen;
 453         }
 454         return (bytes_read);
 455 }