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