citadel/modules/crypto/serv_crypto.c

   1 // Copyright (c) 1987-2022 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
  44 SSL_CTX *ssl_ctx = NULL;                // This SSL context is used for all sessions.
  45
  46
  47 // If a private key does not exist, generate one now.
  48 void generate_key(char *keyfilename) {
  49         int ret = 0;
  50         RSA *rsa = NULL;
  51         BIGNUM *bne = NULL;
  52         int bits = 2048;
  53         unsigned long e = RSA_F4;
  54         FILE *fp;
  55
  56         if (access(keyfilename, R_OK) == 0) {   // Already have one.
  57                 return;
  58         }
  59
  60         syslog(LOG_INFO, "crypto: generating RSA key pair");
  61
  62         // generate rsa key
  63         bne = BN_new();
  64         ret = BN_set_word(bne,e);
  65         if (ret != 1) {
  66                 goto free_all;
  67         }
  68
  69         rsa = RSA_new();
  70         ret = RSA_generate_key_ex(rsa, bits, bne, NULL);
  71         if (ret != 1) {
  72                 goto free_all;
  73         }
  74
  75         // write the key file
  76         fp = fopen(keyfilename, "w");
  77         if (fp != NULL) {
  78                 chmod(keyfilename, 0600);
  79                 if (PEM_write_RSAPrivateKey(fp, // the file
  80                                         rsa,    // the key
  81                                         NULL,   // no enc
  82                                         NULL,   // no passphrase
  83                                         0,      // no passphrase
  84                                         NULL,   // no callback
  85                                         NULL    // no callback
  86                 ) != 1) {
  87                         syslog(LOG_ERR, "crypto: cannot write key: %s", ERR_reason_error_string(ERR_get_error()));
  88                         unlink(keyfilename);
  89                 }
  90                 fclose(fp);
  91         }
  92
  93         // free the memory we used
  94 free_all:
  95         RSA_free(rsa);
  96         BN_free(bne);
  97 }
  98
  99
 100 // If a certificate does not exist, generate a self-signed one now.
 101 void generate_certificate(char *keyfilename, char *certfilename) {
 102         RSA *private_key = NULL;
 103         EVP_PKEY *public_key = NULL;
 104         X509_REQ *certificate_signing_request = NULL;
 105         X509_NAME *name = NULL;
 106         X509 *certificate = NULL;
 107         FILE *fp;
 108
 109         if (access(certfilename, R_OK) == 0) {                  // already have one.
 110                 return;
 111         }
 112
 113         syslog(LOG_INFO, "crypto: generating a self-signed certificate");
 114
 115         // Read in our private key.
 116         fp = fopen(keyfilename, "r");
 117         if (fp) {
 118                 private_key = PEM_read_RSAPrivateKey(fp, NULL, NULL, NULL);
 119                 fclose(fp);
 120         }
 121
 122         if (!private_key) {
 123                 syslog(LOG_ERR, "crypto: cannot read the private key");
 124                 return;
 125         }
 126
 127         // Create a public key from the private key
 128         public_key = EVP_PKEY_new();
 129         if (!public_key) {
 130                 syslog(LOG_ERR, "crypto: cannot allocate public key");
 131                 RSA_free(private_key);
 132                 return;
 133         }
 134         EVP_PKEY_assign_RSA(public_key, private_key);
 135
 136         // Create a certificate signing request
 137         certificate_signing_request = X509_REQ_new();
 138         if (!certificate_signing_request) {
 139                 syslog(LOG_ERR, "crypto: cannot allocate certificate signing request");
 140                 RSA_free(private_key);
 141                 EVP_PKEY_free(public_key);
 142                 return;
 143         }
 144
 145         // Assign the public key to the certificate signing request
 146         X509_REQ_set_pubkey(certificate_signing_request, public_key);
 147         X509_REQ_set_version(certificate_signing_request, 0L);
 148
 149         // Tell it who we are
 150         name = X509_REQ_get_subject_name(certificate_signing_request);
 151         X509_NAME_add_entry_by_txt(name, "C", MBSTRING_ASC, (unsigned const char *)"ZZ", -1, -1, 0);
 152         X509_NAME_add_entry_by_txt(name, "ST", MBSTRING_ASC, (unsigned const char *)"The World", -1, -1, 0);
 153         X509_NAME_add_entry_by_txt(name, "L", MBSTRING_ASC, (unsigned const char *)"My Location", -1, -1, 0);
 154         X509_NAME_add_entry_by_txt(name, "O", MBSTRING_ASC, (unsigned const char *)"Generic certificate", -1, -1, 0);
 155         X509_NAME_add_entry_by_txt(name, "OU", MBSTRING_ASC, (unsigned const char *)"Citadel server", -1, -1, 0);
 156         X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC, (unsigned const char *)"*", -1, -1, 0);
 157         X509_REQ_set_subject_name(certificate_signing_request, name);
 158
 159         // Sign the CSR
 160         if (!X509_REQ_sign(certificate_signing_request, public_key, EVP_md5())) {
 161                 syslog(LOG_ERR, "crypto: X509_REQ_sign(): error");
 162                 X509_REQ_free(certificate_signing_request);
 163                 RSA_free(private_key);
 164                 EVP_PKEY_free(public_key);
 165                 return;
 166         }
 167
 168         // Generate the self-signed certificate
 169         certificate = X509_new();
 170         if (!certificate) {
 171                 syslog(LOG_ERR, "crypto: cannot allocate X.509 certificate");
 172                 X509_REQ_free(certificate_signing_request);
 173                 RSA_free(private_key);
 174                 EVP_PKEY_free(public_key);
 175                 return;
 176         }
 177
 178         ASN1_INTEGER_set(X509_get_serialNumber(certificate), 0);
 179         X509_set_issuer_name(certificate, X509_REQ_get_subject_name(certificate_signing_request));
 180         X509_set_subject_name(certificate, X509_REQ_get_subject_name(certificate_signing_request));
 181         X509_gmtime_adj(X509_get_notBefore(certificate), 0);
 182         X509_gmtime_adj(X509_get_notAfter(certificate), (long)60*60*24*SIGN_DAYS);
 183         X509_set_pubkey(certificate, public_key);
 184         X509_REQ_free(certificate_signing_request);             // We're done with the CSR; free it
 185
 186         // Finally, sign the certificate with our private key.
 187         if (!X509_sign(certificate, public_key, EVP_md5())) {
 188                 syslog(LOG_ERR, "crypto: X509_sign() error");
 189                 X509_free(certificate);
 190                 RSA_free(private_key);
 191                 EVP_PKEY_free(public_key);
 192                 return;
 193         }
 194
 195         // Write the certificate to disk
 196         fp = fopen(certfilename, "w");
 197         if (fp != NULL) {
 198                 chmod(certfilename, 0600);
 199                 PEM_write_X509(fp, certificate);
 200                 fclose(fp);
 201         }
 202         else {
 203                 syslog(LOG_ERR, "crypto: %s: %m", certfilename);
 204         }
 205
 206         X509_free(certificate);
 207         EVP_PKEY_free(public_key);
 208         // RSA_free(private_key);                               // private_key is freed by EVP_PKEY_free() above
 209 }
 210
 211
 212 // Set the private key and certificate chain for the global SSL Context.
 213 // This is called during initialization, and can be called again later if the certificate changes.
 214 void bind_to_key_and_certificate(void) {
 215
 216         SSL_CTX *old_ctx, *new_ctx;
 217
 218         if (!(new_ctx = SSL_CTX_new(TLS_server_method()))) {
 219                 syslog(LOG_ERR, "crypto: SSL_CTX_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 220                 return;
 221         }
 222
 223         if (!(SSL_CTX_set_cipher_list(new_ctx, CIT_CIPHERS))) {
 224                 syslog(LOG_ERR, "crypto: No ciphers available");
 225                 SSL_CTX_free(new_ctx);
 226                 new_ctx = NULL;
 227                 return;
 228         }
 229
 230         syslog(LOG_DEBUG, "crypto: using certificate chain %s", file_crpt_file_cer);
 231         SSL_CTX_use_certificate_chain_file(new_ctx, file_crpt_file_cer);
 232
 233         syslog(LOG_DEBUG, "crypto: using private key %s", file_crpt_file_key);
 234         SSL_CTX_use_PrivateKey_file(new_ctx, file_crpt_file_key, SSL_FILETYPE_PEM);
 235         if ( !SSL_CTX_check_private_key(new_ctx) ) {
 236                 syslog(LOG_ERR, "crypto: cannot install certificate: %s", ERR_reason_error_string(ERR_get_error()));
 237         }
 238
 239         old_ctx = ssl_ctx;
 240         ssl_ctx = new_ctx;              // All future binds will use the new certificate
 241
 242         sleep(1);                       // Hopefully wait until all in-progress binds to the old certificate have completed
 243         SSL_CTX_free(old_ctx);
 244 }
 245
 246
 247 // Check the modification time of the key and certificate files.  Reload if either one changed.
 248 void update_key_and_cert_if_needed(void) {
 249         static time_t previous_mtime = 0;
 250         struct stat keystat;
 251         struct stat certstat;
 252
 253         if (stat(file_crpt_file_key, &keystat) != 0) {
 254                 syslog(LOG_ERR, "%s: %s", file_crpt_file_key, strerror(errno));
 255                 return;
 256         }
 257         if (stat(file_crpt_file_cer, &certstat) != 0) {
 258                 syslog(LOG_ERR, "%s: %s", file_crpt_file_cer, strerror(errno));
 259                 return;
 260         }
 261
 262         if ((keystat.st_mtime + certstat.st_mtime) != previous_mtime) {
 263                 bind_to_key_and_certificate();
 264                 previous_mtime = keystat.st_mtime + certstat.st_mtime;
 265         }
 266 }
 267
 268
 269 // Initialize the SSL/TLS subsystem.
 270 void init_ssl(void) {
 271         SSL_library_init();                                             // Initialize SSL transport layer
 272         SSL_load_error_strings();
 273
 274         mkdir(ctdl_key_dir, 0700);                                      // If the keys directory does not exist, create it
 275         generate_key(file_crpt_file_key);                               // If a private key does not exist, create it
 276         generate_certificate(file_crpt_file_key, file_crpt_file_cer);   // If a certificate does not exist, create it
 277         bind_to_key_and_certificate();                                  // Load key and cert from disk, and bind to them.
 278
 279         // Finally let the server know we're here
 280         CtdlRegisterProtoHook(cmd_stls, "STLS", "Start SSL/TLS session");
 281         CtdlRegisterProtoHook(cmd_gtls, "GTLS", "Get SSL/TLS session status");
 282         CtdlRegisterSessionHook(endtls, EVT_STOP, PRIO_STOP + 10);
 283 }
 284
 285
 286 // client_write_ssl() Send binary data to the client encrypted.
 287 void client_write_ssl(const char *buf, int nbytes) {
 288         int retval;
 289         int nremain;
 290         char junk[1];
 291
 292         nremain = nbytes;
 293
 294         while (nremain > 0) {
 295                 if (SSL_want_write(CC->ssl)) {
 296                         if ((SSL_read(CC->ssl, junk, 0)) < 1) {
 297                                 syslog(LOG_DEBUG, "crypto: SSL_read in client_write: %s", ERR_reason_error_string(ERR_get_error()));
 298                         }
 299                 }
 300                 retval =
 301                     SSL_write(CC->ssl, &buf[nbytes - nremain], nremain);
 302                 if (retval < 1) {
 303                         long errval;
 304
 305                         errval = SSL_get_error(CC->ssl, retval);
 306                         if (errval == SSL_ERROR_WANT_READ ||
 307                             errval == SSL_ERROR_WANT_WRITE) {
 308                                 sleep(1);
 309                                 continue;
 310                         }
 311                         syslog(LOG_DEBUG, "crypto: SSL_write got error %ld, ret %d", errval, retval);
 312                         if (retval == -1) {
 313                                 syslog(LOG_DEBUG, "crypto: errno is %d", errno);
 314                         }
 315                         endtls();
 316                         client_write(&buf[nbytes - nremain], nremain);
 317                         return;
 318                 }
 319                 nremain -= retval;
 320         }
 321 }
 322
 323
 324 // read data from the encrypted layer.
 325 int client_read_sslbuffer(StrBuf *buf, int timeout) {
 326         char sbuf[16384];       // OpenSSL communicates in 16k blocks, so let's speak its native tongue.
 327         int rlen;
 328         char junk[1];
 329         SSL *pssl = CC->ssl;
 330
 331         if (pssl == NULL) return(-1);
 332
 333         while (1) {
 334                 if (SSL_want_read(pssl)) {
 335                         if ((SSL_write(pssl, junk, 0)) < 1) {
 336                                 syslog(LOG_DEBUG, "crypto: SSL_write in client_read");
 337                         }
 338                 }
 339                 rlen = SSL_read(pssl, sbuf, sizeof(sbuf));
 340                 if (rlen < 1) {
 341                         long errval;
 342
 343                         errval = SSL_get_error(pssl, rlen);
 344                         if (errval == SSL_ERROR_WANT_READ || errval == SSL_ERROR_WANT_WRITE) {
 345                                 sleep(1);
 346                                 continue;
 347                         }
 348                         syslog(LOG_DEBUG, "crypto: SSL_read got error %ld", errval);
 349                         endtls();
 350                         return (-1);
 351                 }
 352                 StrBufAppendBufPlain(buf, sbuf, rlen, 0);
 353                 return rlen;
 354         }
 355         return (0);
 356 }
 357
 358
 359 int client_readline_sslbuffer(StrBuf *Line, StrBuf *IOBuf, const char **Pos, int timeout) {
 360         const char *pos = NULL;
 361         const char *pLF;
 362         int len, rlen;
 363         int nSuccessLess = 0;
 364         const char *pch = NULL;
 365
 366         if ((Line == NULL) || (Pos == NULL) || (IOBuf == NULL)) {
 367                 if (Pos != NULL) {
 368                         *Pos = NULL;
 369                 }
 370                 return -1;
 371         }
 372
 373         pos = *Pos;
 374         if ((StrLength(IOBuf) > 0) && (pos != NULL) && (pos < ChrPtr(IOBuf) + StrLength(IOBuf))) {
 375                 pch = pos;
 376                 pch = strchr(pch, '\n');
 377
 378                 if (pch == NULL) {
 379                         StrBufAppendBufPlain(Line, pos, StrLength(IOBuf) - (pos - ChrPtr(IOBuf)), 0);
 380                         FlushStrBuf(IOBuf);
 381                         *Pos = NULL;
 382                 }
 383                 else {
 384                         int n = 0;
 385                         if ((pch > ChrPtr(IOBuf)) &&
 386                             (*(pch - 1) == '\r')) {
 387                                 n = 1;
 388                         }
 389                         StrBufAppendBufPlain(Line, pos,
 390                                              (pch - pos - n), 0);
 391
 392                         if (StrLength(IOBuf) <= (pch - ChrPtr(IOBuf) + 1)) {
 393                                 FlushStrBuf(IOBuf);
 394                                 *Pos = NULL;
 395                         }
 396                         else
 397                                 *Pos = pch + 1;
 398                         return StrLength(Line);
 399                 }
 400         }
 401
 402         pLF = NULL;
 403         while ((nSuccessLess < timeout) &&
 404                (pLF == NULL) &&
 405                (CC->ssl != NULL)) {
 406
 407                 rlen = client_read_sslbuffer(IOBuf, timeout);
 408                 if (rlen < 1) {
 409                         return -1;
 410                 }
 411                 else if (rlen > 0) {
 412                         pLF = strchr(ChrPtr(IOBuf), '\n');
 413                 }
 414         }
 415         *Pos = NULL;
 416         if (pLF != NULL) {
 417                 pos = ChrPtr(IOBuf);
 418                 len = pLF - pos;
 419                 if (len > 0 && (*(pLF - 1) == '\r') )
 420                         len --;
 421                 StrBufAppendBufPlain(Line, pos, len, 0);
 422                 if (pLF + 1 >= ChrPtr(IOBuf) + StrLength(IOBuf))
 423                 {
 424                         FlushStrBuf(IOBuf);
 425                 }
 426                 else
 427                         *Pos = pLF + 1;
 428                 return StrLength(Line);
 429         }
 430         return -1;
 431 }
 432
 433
 434 int client_read_sslblob(StrBuf *Target, long bytes, int timeout) {
 435         long baselen;
 436         long RemainRead;
 437         int retval = 0;
 438
 439         baselen = StrLength(Target);
 440
 441         if (StrLength(CC->RecvBuf.Buf) > 0) {
 442                 long RemainLen;
 443                 long TotalLen;
 444                 const char *pchs;
 445
 446                 if (CC->RecvBuf.ReadWritePointer == NULL) {
 447                         CC->RecvBuf.ReadWritePointer = ChrPtr(CC->RecvBuf.Buf);
 448                 }
 449                 pchs = ChrPtr(CC->RecvBuf.Buf);
 450                 TotalLen = StrLength(CC->RecvBuf.Buf);
 451                 RemainLen = TotalLen - (pchs - CC->RecvBuf.ReadWritePointer);
 452                 if (RemainLen > bytes) {
 453                         RemainLen = bytes;
 454                 }
 455                 if (RemainLen > 0) {
 456                         StrBufAppendBufPlain(Target, CC->RecvBuf.ReadWritePointer, RemainLen, 0);
 457                         CC->RecvBuf.ReadWritePointer += RemainLen;
 458                 }
 459                 if ((ChrPtr(CC->RecvBuf.Buf) + StrLength(CC->RecvBuf.Buf)) <= CC->RecvBuf.ReadWritePointer) {
 460                         CC->RecvBuf.ReadWritePointer = NULL;
 461                         FlushStrBuf(CC->RecvBuf.Buf);
 462                 }
 463         }
 464
 465         if (StrLength(Target) >= bytes + baselen) {
 466                 return 1;
 467         }
 468
 469         CC->RecvBuf.ReadWritePointer = NULL;
 470
 471         while ((StrLength(Target) < bytes + baselen) && (retval >= 0)) {
 472                 retval = client_read_sslbuffer(CC->RecvBuf.Buf, timeout);
 473                 if (retval >= 0) {
 474                         RemainRead = bytes - (StrLength (Target) - baselen);
 475                         if (RemainRead < StrLength(CC->RecvBuf.Buf)) {
 476                                 StrBufAppendBufPlain(
 477                                         Target,
 478                                         ChrPtr(CC->RecvBuf.Buf),
 479                                         RemainRead, 0);
 480                                 CC->RecvBuf.ReadWritePointer = ChrPtr(CC->RecvBuf.Buf) + RemainRead;
 481                                 break;
 482                         }
 483                         StrBufAppendBuf(Target, CC->RecvBuf.Buf, 0);    // todo: Buf > bytes?
 484                         FlushStrBuf(CC->RecvBuf.Buf);
 485                 }
 486                 else {
 487                         FlushStrBuf(CC->RecvBuf.Buf);
 488                         return -1;
 489
 490                 }
 491         }
 492         return 1;
 493 }
 494
 495
 496 // CtdlStartTLS() starts SSL/TLS encryption for the current session.  It
 497 // must be supplied with pre-generated strings for responses of "ok," "no
 498 // support for TLS," and "error" so that we can use this in any protocol.
 499 void CtdlStartTLS(char *ok_response, char *nosup_response, char *error_response) {
 500         int retval, bits, alg_bits;
 501
 502         if (CC->redirect_ssl) {
 503                 syslog(LOG_ERR, "crypto: attempt to begin SSL on an already encrypted connection");
 504                 if (error_response != NULL) {
 505                         cprintf("%s", error_response);
 506                 }
 507                 return;
 508         }
 509
 510         if (!ssl_ctx) {
 511                 syslog(LOG_ERR, "crypto: SSL failed: context has not been initialized");
 512                 if (nosup_response != NULL) {
 513                         cprintf("%s", nosup_response);
 514                 }
 515                 return;
 516         }
 517
 518         update_key_and_cert_if_needed();                // did someone update the key or cert?  if so, re-bind them
 519
 520         if (!(CC->ssl = SSL_new(ssl_ctx))) {
 521                 syslog(LOG_ERR, "crypto: SSL_new failed: %s", ERR_reason_error_string(ERR_get_error()));
 522                 if (error_response != NULL) {
 523                         cprintf("%s", error_response);
 524                 }
 525                 return;
 526         }
 527         if (!(SSL_set_fd(CC->ssl, CC->client_socket))) {
 528                 syslog(LOG_ERR, "crypto: SSL_set_fd failed: %s", ERR_reason_error_string(ERR_get_error()));
 529                 SSL_free(CC->ssl);
 530                 CC->ssl = NULL;
 531                 if (error_response != NULL) {
 532                         cprintf("%s", error_response);
 533                 }
 534                 return;
 535         }
 536         if (ok_response != NULL) {
 537                 cprintf("%s", ok_response);
 538         }
 539         retval = SSL_accept(CC->ssl);
 540         if (retval < 1) {
 541                 // Can't notify the client of an error here; they will
 542                 // discover the problem at the SSL layer and should
 543                 // revert to unencrypted communications.
 544                 long errval;
 545                 char error_string[128];
 546
 547                 errval = SSL_get_error(CC->ssl, retval);
 548                 syslog(LOG_ERR, "crypto: SSL_accept failed: retval=%d, errval=%ld, err=%s",
 549                         retval,
 550                         errval,
 551                         ERR_error_string(errval, error_string)
 552                 );
 553                 SSL_free(CC->ssl);
 554                 CC->ssl = NULL;
 555                 return;
 556         }
 557         bits = SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl), &alg_bits);
 558         syslog(LOG_INFO, "crypto: SSL/TLS using %s on %s (%d of %d bits)",
 559                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 560                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 561                 bits, alg_bits
 562         );
 563         CC->redirect_ssl = 1;
 564 }
 565
 566
 567 // cmd_stls() starts SSL/TLS encryption for the current session
 568 void cmd_stls(char *params) {
 569         char ok_response[SIZ];
 570         char nosup_response[SIZ];
 571         char error_response[SIZ];
 572
 573         unbuffer_output();
 574
 575         sprintf(ok_response, "%d Begin TLS negotiation now\n", CIT_OK);
 576         sprintf(nosup_response, "%d TLS not supported here\n", ERROR + CMD_NOT_SUPPORTED);
 577         sprintf(error_response, "%d TLS negotiation error\n", ERROR + INTERNAL_ERROR);
 578
 579         CtdlStartTLS(ok_response, nosup_response, error_response);
 580 }
 581
 582
 583 // cmd_gtls() returns status info about the TLS connection
 584 void cmd_gtls(char *params) {
 585         int bits, alg_bits;
 586
 587         if (!CC->ssl || !CC->redirect_ssl) {
 588                 cprintf("%d Session is not encrypted.\n", ERROR);
 589                 return;
 590         }
 591         bits =
 592             SSL_CIPHER_get_bits(SSL_get_current_cipher(CC->ssl),
 593                                 &alg_bits);
 594         cprintf("%d %s|%s|%d|%d\n", CIT_OK,
 595                 SSL_CIPHER_get_version(SSL_get_current_cipher(CC->ssl)),
 596                 SSL_CIPHER_get_name(SSL_get_current_cipher(CC->ssl)),
 597                 alg_bits, bits);
 598 }
 599
 600
 601 // endtls() shuts down the TLS connection
 602 //
 603 // WARNING:  This may make your session vulnerable to a known plaintext
 604 // attack in the current implmentation.
 605 void endtls(void) {
 606         if (!CC->ssl) {
 607                 CC->redirect_ssl = 0;
 608                 return;
 609         }
 610
 611         syslog(LOG_INFO, "crypto: ending SSL/TLS");
 612         SSL_shutdown(CC->ssl);
 613         SSL_free(CC->ssl);
 614         CC->ssl = NULL;
 615         CC->redirect_ssl = 0;
 616 }
 617
 618 #endif  // HAVE_OPENSSL