citadel/modules/crypto/serv_crypto.c

   1 // Copyright (c) 1987-2021 by the citadel.org team
   2 //
   3 // This program is open source software; you can redistribute it and/or modify
   4 // it under the terms of the GNU General Public License version 3.
   5 //
   6 // This program is distributed in the hope that it will be useful,
   7 // but WITHOUT ANY WARRANTY; without even the implied warranty of
   8 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9 // GNU General Public License for more details.
  10
  11 #include <string.h>
  12 #include <unistd.h>
  13 #include <sys/stat.h>
  14 #include <sys/types.h>
  15 #include "sysdep.h"
  16
  17 #ifdef HAVE_OPENSSL
  18 #include <openssl/ssl.h>
  19 #include <openssl/err.h>
  20 #include <openssl/rand.h>
  21 #endif
  22
  23 #include <time.h>
  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 <libcitadel.h>
  35 #include "server.h"
  36 #include "serv_crypto.h"
  37 #include "sysdep_decls.h"
  38 #include "citadel.h"
  39 #include "config.h"
  40 #include "ctdl_module.h"
  41
  42 #ifdef HAVE_OPENSSL
  43 SSL_CTX *ssl_ctx;                       // SSL context
  44
  45
  46 void generate_key(char *keyfilename) {
  47         int ret = 0;
  48         RSA *rsa = NULL;
  49         BIGNUM *bne = NULL;
  50         int bits = 2048;
  51         unsigned long e = RSA_F4;
  52         FILE *fp;
  53
  54         if (access(keyfilename, R_OK) == 0) {
  55                 return;
  56         }
  57
  58         syslog(LOG_INFO, "crypto: generating RSA key pair");
  59
  60         // generate rsa key
  61         bne = BN_new();
  62         ret = BN_set_word(bne,e);
  63         if (ret != 1) {
  64                 goto free_all;
  65         }
  66
  67         rsa = RSA_new();
  68         ret = RSA_generate_key_ex(rsa, bits, bne, NULL);
  69         if (ret != 1) {
  70                 goto free_all;
  71         }
  72
  73         // write the key file
  74         fp = fopen(keyfilename, "w");
  75         if (fp != NULL) {
  76                 chmod(keyfilename, 0600);
  77                 if (PEM_write_RSAPrivateKey(fp, // the file
  78                                         rsa,    // the key
  79                                         NULL,   // no enc
  80                                         NULL,   // no passphrase
  81                                         0,      // no passphrase
  82                                         NULL,   // no callback
  83                                         NULL    // no callback
  84                 ) != 1) {
  85                         syslog(LOG_ERR, "crypto: cannot write key: %s", ERR_reason_error_string(ERR_get_error()));
  86                         unlink(keyfilename);
  87                 }
  88                 fclose(fp);
  89         }
  90
  91     // free the memory we used
  92 free_all:
  93     RSA_free(rsa);
  94     BN_free(bne);
  95 }
  96
  97
  98 void init_ssl(void) {
  99         const SSL_METHOD *ssl_method;
 100         RSA *rsa = NULL;
 101         X509_REQ *req = NULL;
 102         X509 *cer = NULL;
 103         EVP_PKEY *pk = NULL;
 104         EVP_PKEY *req_pkey = NULL;
 105         X509_NAME *name = NULL;
 106         FILE *fp;
 107
 108         // Initialize SSL transport layer
 109         SSL_library_init();
 110         SSL_load_error_strings();
 111         ssl_method = SSLv23_server_method();
 112         if (!(ssl_ctx = SSL_CTX_new(ssl_method))) {
 113                 syslog(LOG_ERR, "crypto: SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 114                 return;
 115         }
 116         if (!(SSL_CTX_set_cipher_list(ssl_ctx, CIT_CIPHERS))) {
 117                 syslog(LOG_ERR, "crypto: No ciphers available");
 118                 SSL_CTX_free(ssl_ctx);
 119                 ssl_ctx = NULL;
 120                 return;
 121         }
 122
 123         mkdir(ctdl_key_dir, 0700);              // If the keys directory does not exist, create it
 124         generate_key(file_crpt_file_key);       // If a private key does not exist, create it
 125
 126         // If there is no certificate file on disk, we will be generating a self-signed certificate
 127         // in the next step.  Therefore, if we have neither a CSR nor a certificate, generate
 128         // the CSR in this step so that the next step may commence.
 129         if ( (access(file_crpt_file_cer, R_OK) != 0) && (access(file_crpt_file_csr, R_OK) != 0) ) {
 130                 syslog(LOG_INFO, "crypto: generating a generic certificate signing request.");
 131
 132                 // Read our key from the file.  No, we don't just keep this
 133                 // in memory from the above key-generation function, because
 134                 // there is the possibility that the key was already on disk
 135                 // and we didn't just generate it now.
 136                 fp = fopen(file_crpt_file_key, "r");
 137                 if (fp) {
 138                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 139                         fclose(fp);
 140                 }
 141
 142                 if (rsa) {
 143
 144                         // Create a public key from the private key
 145                         if (pk=EVP_PKEY_new(), pk != NULL) {
 146                                 EVP_PKEY_assign_RSA(pk, rsa);
 147                                 if (req = X509_REQ_new(), req != NULL) {
 148
 149                                         // Set the public key
 150                                         X509_REQ_set_pubkey(req, pk);
 151                                         X509_REQ_set_version(req, 0L);
 152
 153                                         name = X509_REQ_get_subject_name(req);
 154
 155                                         // Tell it who we are
 156                                         X509_NAME_add_entry_by_txt(name, "C", MBSTRING_ASC, (unsigned const char *)"ZZ", -1, -1, 0);
 157                                         X509_NAME_add_entry_by_txt(name, "ST", MBSTRING_ASC, (unsigned const char *)"The World", -1, -1, 0);
 158                                         X509_NAME_add_entry_by_txt(name, "L", MBSTRING_ASC, (unsigned const char *)"My Location", -1, -1, 0);
 159                                         X509_NAME_add_entry_by_txt(name, "O", MBSTRING_ASC, (unsigned const char *)"Generic certificate", -1, -1, 0);
 160                                         X509_NAME_add_entry_by_txt(name, "OU", MBSTRING_ASC, (unsigned const char *)"Citadel server", -1, -1, 0);
 161                                         X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC, (unsigned const char *)"*", -1, -1, 0);
 162                                         X509_REQ_set_subject_name(req, name);
 163
 164                                         // Sign the CSR
 165                                         if (!X509_REQ_sign(req, pk, EVP_md5())) {
 166                                                 syslog(LOG_ERR, "crypto: X509_REQ_sign(): error");
 167                                         }
 168                                         else {
 169                                                 // Write it to disk
 170                                                 fp = fopen(file_crpt_file_csr, "w");
 171                                                 if (fp != NULL) {
 172                                                         chmod(file_crpt_file_csr, 0600);
 173                                                         PEM_write_X509_REQ(fp, req);
 174                                                         fclose(fp);
 175                                                 }
 176                                         }
 177
 178                                         X509_REQ_free(req);
 179                                 }
 180                         }
 181
 182                         RSA_free(rsa);
 183                 }
 184
 185                 else {
 186                         syslog(LOG_ERR, "crypto: unable to read private key.");
 187                 }
 188         }
 189
 190         // Generate a self-signed certificate if we don't have one.
 191         if (access(file_crpt_file_cer, R_OK) != 0) {
 192                 syslog(LOG_INFO, "crypto: generating a generic self-signed certificate.");
 193
 194                 // Same deal as before: always read the key from disk because
 195                 // it may or may not have just been generated.
 196                 fp = fopen(file_crpt_file_key, "r");
 197                 if (fp) {
 198                         rsa = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 199                         fclose(fp);
 200                 }
 201
 202                 // This also holds true for the CSR.
 203                 req = NULL;
 204                 cer = NULL;
 205                 pk = NULL;
 206                 if (rsa) {
 207                         if (pk=EVP_PKEY_new(), pk != NULL) {
 208                                 EVP_PKEY_assign_RSA(pk, rsa);
 209                         }
 210
 211                         fp = fopen(file_crpt_file_csr, "r");
 212                         if (fp) {
 213                                 req = PEM_read_X509_REQ(fp, NULL, NULL, NULL);
 214                                 fclose(fp);
 215                         }
 216
 217                         if (req) {
 218                                 if (cer = X509_new(), cer != NULL) {
 219                                         ASN1_INTEGER_set(X509_get_serialNumber(cer), 0);
 220                                         X509_set_issuer_name(cer, X509_REQ_get_subject_name(req));
 221                                         X509_set_subject_name(cer, X509_REQ_get_subject_name(req));
 222                                         X509_gmtime_adj(X509_get_notBefore(cer),0);
 223                                         X509_gmtime_adj(X509_get_notAfter(cer),(long)60*60*24*SIGN_DAYS);
 224                                         req_pkey = X509_REQ_get_pubkey(req);
 225                                         X509_set_pubkey(cer, req_pkey);
 226                                         EVP_PKEY_free(req_pkey);
 227
 228                                         // Sign the cert
 229                                         if (!X509_sign(cer, pk, EVP_md5())) {
 230                                                 syslog(LOG_ERR, "crypto: X509_sign() error");
 231                                         }
 232                                         else {
 233                                                 // Write it to disk.
 234                                                 fp = fopen(file_crpt_file_cer, "w");
 235                                                 if (fp != NULL) {
 236                                                         chmod(file_crpt_file_cer, 0600);
 237                                                         PEM_write_X509(fp, cer);
 238                                                         fclose(fp);
 239                                                 }
 240                                         }
 241                                         X509_free(cer);
 242                                 }
 243                         }
 244
 245                         RSA_free(rsa);
 246                 }
 247         }
 248
 249         // Now try to bind to the key and certificate.
 250         SSL_CTX_use_certificate_chain_file(ssl_ctx, file_crpt_file_cer);
 251         SSL_CTX_use_PrivateKey_file(ssl_ctx, file_crpt_file_key, SSL_FILETYPE_PEM);
 252         if ( !SSL_CTX_check_private_key(ssl_ctx) ) {
 253                 syslog(LOG_ERR, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
 254         }
 255
 256         // Finally let the server know we're here
 257         CtdlRegisterProtoHook(cmd_stls, "STLS", "Start SSL/TLS session");
 258         CtdlRegisterProtoHook(cmd_gtls, "GTLS", "Get SSL/TLS session status");
 259         CtdlRegisterSessionHook(endtls, EVT_STOP, PRIO_STOP + 10);
 260 }
 261
 262
 263 // client_write_ssl() Send binary data to the client encrypted.
 264 void client_write_ssl(const char *buf, int nbytes) {
 265         int retval;
 266         int nremain;
 267         char junk[1];
 268
 269         nremain = nbytes;
 270
 271         while (nremain > 0) {
 272                 if (SSL_want_write(CC->ssl)) {
 273                         if ((SSL_read(CC->ssl, junk, 0)) < 1) {
 274                                 syslog(LOG_DEBUG, "crypto: SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 275                         }
 276                 }
 277                 retval =
 278                     SSL_write(CC->ssl, &buf[nbytes - nremain], nremain);
 279                 if (retval < 1) {
 280                         long errval;
 281
 282                         errval = SSL_get_error(CC->ssl, retval);
 283                         if (errval == SSL_ERROR_WANT_READ ||
 284                             errval == SSL_ERROR_WANT_WRITE) {
 285                                 sleep(1);
 286                                 continue;
 287                         }
 288                         syslog(LOG_DEBUG, "crypto: SSL_write got error %ld, ret %d", errval, retval);
 289                         if (retval == -1) {
 290                                 syslog(LOG_DEBUG, "crypto: errno is %d", errno);
 291                         }
 292                         endtls();
 293                         client_write(&buf[nbytes - nremain], nremain);
 294                         return;
 295                 }
 296                 nremain -= retval;
 297         }
 298 }
 299
 300
 301 // read data from the encrypted layer.
 302 int client_read_sslbuffer(StrBuf *buf, int timeout) {
 303         char sbuf[16384];       // OpenSSL communicates in 16k blocks, so let's speak its native tongue.
 304         int rlen;
 305         char junk[1];
 306         SSL *pssl = CC->ssl;
 307
 308         if (pssl == NULL) return(-1);
 309
 310         while (1) {
 311                 if (SSL_want_read(pssl)) {
 312                         if ((SSL_write(pssl, junk, 0)) < 1) {
 313                                 syslog(LOG_DEBUG, "crypto: SSL_write in client_read");
 314                         }
 315                 }
 316                 rlen = SSL_read(pssl, sbuf, sizeof(sbuf));
 317                 if (rlen < 1) {
 318                         long errval;
 319
 320                         errval = SSL_get_error(pssl, rlen);
 321                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 322                                 sleep(1);
 323                                 continue;
 324                         }
 325                         syslog(LOG_DEBUG, "crypto: SSL_read got error %ld", errval);
 326                         endtls();
 327                         return (-1);
 328                 }
 329                 StrBufAppendBufPlain(buf, sbuf, rlen, 0);
 330                 return rlen;
 331         }
 332         return (0);
 333 }
 334
 335
 336 int client_readline_sslbuffer(StrBuf *Line, StrBuf *IOBuf, const char **Pos, int timeout) {
 337         const char *pos = NULL;
 338         const char *pLF;
 339         int len, rlen;
 340         int nSuccessLess = 0;
 341         const char *pch = NULL;
 342
 343         if ((Line == NULL) || (Pos == NULL) || (IOBuf == NULL))
 344         {
 345                 if (Pos != NULL)
 346                 {
 347                         *Pos = NULL;
 348                 }
 349                 return -1;
 350         }
 351
 352         pos = *Pos;
 353         if ((StrLength(IOBuf) > 0) && (pos != NULL) && (pos < ChrPtr(IOBuf) + StrLength(IOBuf)))
 354         {
 355                 pch = pos;
 356                 pch = strchr(pch, '\n');
 357
 358                 if (pch == NULL) {
 359                         StrBufAppendBufPlain(Line, pos, StrLength(IOBuf) - (pos - ChrPtr(IOBuf)), 0);
 360                         FlushStrBuf(IOBuf);
 361                         *Pos = NULL;
 362                 }
 363                 else {
 364                         int n = 0;
 365                         if ((pch > ChrPtr(IOBuf)) &&
 366                             (*(pch - 1) == '\r')) {
 367                                 n = 1;
 368                         }
 369                         StrBufAppendBufPlain(Line, pos,
 370                                              (pch - pos - n), 0);
 371
 372                         if (StrLength(IOBuf) <= (pch - ChrPtr(IOBuf) + 1)) {
 373                                 FlushStrBuf(IOBuf);
 374                                 *Pos = NULL;
 375                         }
 376                         else
 377                                 *Pos = pch + 1;
 378                         return StrLength(Line);
 379                 }
 380         }
 381
 382         pLF = NULL;
 383         while ((nSuccessLess < timeout) &&
 384                (pLF == NULL) &&
 385                (CC->ssl != NULL)) {
 386
 387                 rlen = client_read_sslbuffer(IOBuf, timeout);
 388                 if (rlen < 1) {
 389                         return -1;
 390                 }
 391                 else if (rlen > 0) {
 392                         pLF = strchr(ChrPtr(IOBuf), '\n');
 393                 }
 394         }
 395         *Pos = NULL;
 396         if (pLF != NULL) {
 397                 pos = ChrPtr(IOBuf);
 398                 len = pLF - pos;
 399                 if (len > 0 && (*(pLF - 1) == '\r') )
 400                         len --;
 401                 StrBufAppendBufPlain(Line, pos, len, 0);
 402                 if (pLF + 1 >= ChrPtr(IOBuf) + StrLength(IOBuf))
 403                 {
 404                         FlushStrBuf(IOBuf);
 405                 }
 406                 else
 407                         *Pos = pLF + 1;
 408                 return StrLength(Line);
 409         }
 410         return -1;
 411 }
 412
 413
 414 int client_read_sslblob(StrBuf *Target, long bytes, int timeout) {
 415         long baselen;
 416         long RemainRead;
 417         int retval = 0;
 418
 419         baselen = StrLength(Target);
 420
 421         if (StrLength(CC->RecvBuf.Buf) > 0) {
 422                 long RemainLen;
 423                 long TotalLen;
 424                 const char *pchs;
 425
 426                 if (CC->RecvBuf.ReadWritePointer == NULL) {
 427                         CC->RecvBuf.ReadWritePointer = ChrPtr(CC->RecvBuf.Buf);
 428                 }
 429                 pchs = ChrPtr(CC->RecvBuf.Buf);
 430                 TotalLen = StrLength(CC->RecvBuf.Buf);
 431                 RemainLen = TotalLen - (pchs - CC->RecvBuf.ReadWritePointer);
 432                 if (RemainLen > bytes) {
 433                         RemainLen = bytes;
 434                 }
 435                 if (RemainLen > 0) {
 436                         StrBufAppendBufPlain(Target, CC->RecvBuf.ReadWritePointer, RemainLen, 0);
 437                         CC->RecvBuf.ReadWritePointer += RemainLen;
 438                 }
 439                 if ((ChrPtr(CC->RecvBuf.Buf) + StrLength(CC->RecvBuf.Buf)) <= CC->RecvBuf.ReadWritePointer) {
 440                         CC->RecvBuf.ReadWritePointer = NULL;
 441                         FlushStrBuf(CC->RecvBuf.Buf);
 442                 }
 443         }
 444
 445         if (StrLength(Target) >= bytes + baselen) {
 446                 return 1;
 447         }
 448
 449         CC->RecvBuf.ReadWritePointer = NULL;
 450
 451         while ((StrLength(Target) < bytes + baselen) && (retval >= 0)) {
 452                 retval = client_read_sslbuffer(CC->RecvBuf.Buf, timeout);
 453                 if (retval >= 0) {
 454                         RemainRead = bytes - (StrLength (Target) - baselen);
 455                         if (RemainRead < StrLength(CC->RecvBuf.Buf)) {
 456                                 StrBufAppendBufPlain(
 457                                         Target,
 458                                         ChrPtr(CC->RecvBuf.Buf),
 459                                         RemainRead, 0);
 460                                 CC->RecvBuf.ReadWritePointer = ChrPtr(CC->RecvBuf.Buf) + RemainRead;
 461                                 break;
 462                         }
 463                         StrBufAppendBuf(Target, CC->RecvBuf.Buf, 0);    // todo: Buf > bytes?
 464                         FlushStrBuf(CC->RecvBuf.Buf);
 465                 }
 466                 else {
 467                         FlushStrBuf(CC->RecvBuf.Buf);
 468                         return -1;
 469
 470                 }
 471         }
 472         return 1;
 473 }
 474
 475
 476 // CtdlStartTLS() starts SSL/TLS encryption for the current session.  It
 477 // must be supplied with pre-generated strings for responses of "ok," "no
 478 // support for TLS," and "error" so that we can use this in any protocol.
 479 void CtdlStartTLS(char *ok_response, char *nosup_response, char *error_response) {
 480         int retval, bits, alg_bits;
 481
 482         if (CC->redirect_ssl) {
 483                 syslog(LOG_ERR, "crypto: attempt to begin SSL on an already encrypted connection");
 484                 if (error_response != NULL) {
 485                         cprintf("%s", error_response);
 486                 }
 487                 return;
 488         }
 489
 490         if (!ssl_ctx) {
 491                 syslog(LOG_ERR, "crypto: SSL failed: no ssl_ctx exists?");
 492                 if (nosup_response != NULL) cprintf("%s", nosup_response);
 493                 return;
 494         }
 495         if (!(CC->ssl = SSL_new(ssl_ctx))) {
 496                 syslog(LOG_ERR, "crypto: SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 497                 if (error_response != NULL) {
 498                         cprintf("%s", error_response);
 499                 }
 500                 return;
 501         }
 502         if (!(SSL_set_fd(CC->ssl, CC->client_socket))) {
 503                 syslog(LOG_ERR, "crypto: SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 504                 SSL_free(CC->ssl);
 505                 CC->ssl = NULL;
 506                 if (error_response != NULL) cprintf("%s", error_response);
 507                 return;
 508         }
 509         if (ok_response != NULL) cprintf("%s", ok_response);
 510         retval = SSL_accept(CC->ssl);
 511         if (retval < 1) {
 512                 // Can't notify the client of an error here; they will
 513                 // discover the problem at the SSL layer and should
 514                 // revert to unencrypted communications.
 515                 long errval;
 516                 char error_string[128];
 517
 518                 errval = SSL_get_error(CC->ssl, retval);
 519                 syslog(LOG_ERR, "crypto: SSL_accept failed: retval=%d, errval=%ld, err=%s",
 520                         retval,
 521                         errval,
 522                         ERR_error_string(errval, error_string)
 523                 );
 524                 SSL_free(CC->ssl);
 525                 CC->ssl = NULL;
 526                 return;
 527         }
 528         // BIO_set_close(CC->ssl->rbio, BIO_NOCLOSE); not needed anymore in openssl 1.1 ?
 529         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl), &alg_bits);
 530         syslog(LOG_INFO, "crypto: SSL/TLS using %s on %s (%d of %d bits)",
 531                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 532                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 533                 bits, alg_bits
 534         );
 535         CC->redirect_ssl = 1;
 536 }
 537
 538
 539 // cmd_stls() starts SSL/TLS encryption for the current session
 540 void cmd_stls(char *params) {
 541         char ok_response[SIZ];
 542         char nosup_response[SIZ];
 543         char error_response[SIZ];
 544
 545         unbuffer_output();
 546
 547         sprintf(ok_response, "%d Begin TLS negotiation now\n", CIT_OK);
 548         sprintf(nosup_response, "%d TLS not supported here\n", ERROR + CMD_NOT_SUPPORTED);
 549         sprintf(error_response, "%d TLS negotiation error\n", ERROR + INTERNAL_ERROR);
 550
 551         CtdlStartTLS(ok_response, nosup_response, error_response);
 552 }
 553
 554
 555 // cmd_gtls() returns status info about the TLS connection
 556 void cmd_gtls(char *params) {
 557         int bits, alg_bits;
 558
 559         if (!CC->ssl || !CC->redirect_ssl) {
 560                 cprintf("%d Session is not encrypted.\n", ERROR);
 561                 return;
 562         }
 563         bits =
 564             SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl),
 565                                 &alg_bits);
 566         cprintf("%d %s|%s|%d|%d\n", CIT_OK,
 567                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 568                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 569                 alg_bits, bits);
 570 }
 571
 572
 573 // endtls() shuts down the TLS connection
 574 //
 575 // WARNING:  This may make your session vulnerable to a known plaintext
 576 // attack in the current implmentation.
 577 void endtls(void) {
 578         if (!CC->ssl) {
 579                 CC->redirect_ssl = 0;
 580                 return;
 581         }
 582
 583         syslog(LOG_INFO, "crypto: ending SSL/TLS");
 584         SSL_shutdown(CC->ssl);
 585         SSL_free(CC->ssl);
 586         CC->ssl = NULL;
 587         CC->redirect_ssl = 0;
 588 }
 589
 590 #endif  // HAVE_OPENSSL