src/src/tls-openssl.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2015 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* Portions Copyright (c) The OpenSSL Project 1999 */
   9
  10 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
  11 library. It is #included into the tls.c file when that library is used. The
  12 code herein is based on a patch that was originally contributed by Steve
  13 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
  14
  15 No cryptographic code is included in Exim. All this module does is to call
  16 functions from the OpenSSL library. */
  17
  18
  19 /* Heading stuff */
  20
  21 #include <openssl/lhash.h>
  22 #include <openssl/ssl.h>
  23 #include <openssl/err.h>
  24 #include <openssl/rand.h>
  25 #ifndef OPENSSL_NO_ECDH
  26 # include <openssl/ec.h>
  27 #endif
  28 #ifndef DISABLE_OCSP
  29 # include <openssl/ocsp.h>
  30 #endif
  31 #ifdef EXPERIMENTAL_DANE
  32 # include <danessl.h>
  33 #endif
  34
  35
  36 #ifndef DISABLE_OCSP
  37 # define EXIM_OCSP_SKEW_SECONDS (300L)
  38 # define EXIM_OCSP_MAX_AGE (-1L)
  39 #endif
  40
  41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
  42 # define EXIM_HAVE_OPENSSL_TLSEXT
  43 #endif
  44
  45 /*
  46  * X509_check_host provides sane certificate hostname checking, but was added
  47  * to OpenSSL late, after other projects forked off the code-base.  So in
  48  * addition to guarding against the base version number, beware that LibreSSL
  49  * does not (at this time) support this function.
  50  *
  51  * If LibreSSL gains a different API, perhaps via libtls, then we'll probably
  52  * opt to disentangle and ask a LibreSSL user to provide glue for a third
  53  * crypto provider for libtls instead of continuing to tie the OpenSSL glue
  54  * into even twistier knots.  If LibreSSL gains the same API, we can just
  55  * change this guard and punt the issue for a while longer.
  56  */
  57 #ifndef LIBRESSL_VERSION_NUMBER
  58 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
  59 #  define EXIM_HAVE_OPENSSL_CHECKHOST
  60 # endif
  61 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
  62     && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
  63 #  define EXIM_HAVE_OPENSSL_CHECKHOST
  64 # endif
  65
  66 # if !defined(OPENSSL_NO_ECDH)
  67 #  if OPENSSL_VERSION_NUMBER >= 0x0090800fL
  68 #   define EXIM_HAVE_ECDH
  69 #  endif
  70 #  if OPENSSL_VERSION_NUMBER >= 0x10002000L
  71 #   define EXIM_HAVE_OPENSSL_ECDH_AUTO
  72 #   define EXIM_HAVE_OPENSSL_EC_NIST2NID
  73 #  endif
  74 # endif
  75 #endif
  76
  77 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
  78 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
  79 # define DISABLE_OCSP
  80 #endif
  81
  82 /* Structure for collecting random data for seeding. */
  83
  84 typedef struct randstuff {
  85   struct timeval tv;
  86   pid_t          p;
  87 } randstuff;
  88
  89 /* Local static variables */
  90
  91 static BOOL client_verify_callback_called = FALSE;
  92 static BOOL server_verify_callback_called = FALSE;
  93 static const uschar *sid_ctx = US"exim";
  94
  95 /* We have three different contexts to care about.
  96
  97 Simple case: client, `client_ctx`
  98  As a client, we can be doing a callout or cut-through delivery while receiving
  99  a message.  So we have a client context, which should have options initialised
 100  from the SMTP Transport.
 101
 102 Server:
 103  There are two cases: with and without ServerNameIndication from the client.
 104  Given TLS SNI, we can be using different keys, certs and various other
 105  configuration settings, because they're re-expanded with $tls_sni set.  This
 106  allows vhosting with TLS.  This SNI is sent in the handshake.
 107  A client might not send SNI, so we need a fallback, and an initial setup too.
 108  So as a server, we start out using `server_ctx`.
 109  If SNI is sent by the client, then we as server, mid-negotiation, try to clone
 110  `server_sni` from `server_ctx` and then initialise settings by re-expanding
 111  configuration.
 112 */
 113
 114 static SSL_CTX *client_ctx = NULL;
 115 static SSL_CTX *server_ctx = NULL;
 116 static SSL     *client_ssl = NULL;
 117 static SSL     *server_ssl = NULL;
 118
 119 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 120 static SSL_CTX *server_sni = NULL;
 121 #endif
 122
 123 static char ssl_errstring[256];
 124
 125 static int  ssl_session_timeout = 200;
 126 static BOOL client_verify_optional = FALSE;
 127 static BOOL server_verify_optional = FALSE;
 128
 129 static BOOL reexpand_tls_files_for_sni = FALSE;
 130
 131
 132 typedef struct tls_ext_ctx_cb {
 133   uschar *certificate;
 134   uschar *privatekey;
 135 #ifndef DISABLE_OCSP
 136   BOOL is_server;
 137   union {
 138     struct {
 139       uschar        *file;
 140       uschar        *file_expanded;
 141       OCSP_RESPONSE *response;
 142     } server;
 143     struct {
 144       X509_STORE    *verify_store;      /* non-null if status requested */
 145       BOOL          verify_required;
 146     } client;
 147   } u_ocsp;
 148 #endif
 149   uschar *dhparam;
 150   /* these are cached from first expand */
 151   uschar *server_cipher_list;
 152   /* only passed down to tls_error: */
 153   host_item *host;
 154   const uschar * verify_cert_hostnames;
 155 #ifdef EXPERIMENTAL_EVENT
 156   uschar * event_action;
 157 #endif
 158 } tls_ext_ctx_cb;
 159
 160 /* should figure out a cleanup of API to handle state preserved per
 161 implementation, for various reasons, which can be void * in the APIs.
 162 For now, we hack around it. */
 163 tls_ext_ctx_cb *client_static_cbinfo = NULL;
 164 tls_ext_ctx_cb *server_static_cbinfo = NULL;
 165
 166 static int
 167 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
 168     int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
 169
 170 /* Callbacks */
 171 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 172 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
 173 #endif
 174 #ifndef DISABLE_OCSP
 175 static int tls_server_stapling_cb(SSL *s, void *arg);
 176 #endif
 177
 178
 179 /*************************************************
 180 *               Handle TLS error                 *
 181 *************************************************/
 182
 183 /* Called from lots of places when errors occur before actually starting to do
 184 the TLS handshake, that is, while the session is still in clear. Always returns
 185 DEFER for a server and FAIL for a client so that most calls can use "return
 186 tls_error(...)" to do this processing and then give an appropriate return. A
 187 single function is used for both server and client, because it is called from
 188 some shared functions.
 189
 190 Argument:
 191   prefix    text to include in the logged error
 192   host      NULL if setting up a server;
 193             the connected host if setting up a client
 194   msg       error message or NULL if we should ask OpenSSL
 195
 196 Returns:    OK/DEFER/FAIL
 197 */
 198
 199 static int
 200 tls_error(uschar * prefix, const host_item * host, uschar *  msg)
 201 {
 202 if (!msg)
 203   {
 204   ERR_error_string(ERR_get_error(), ssl_errstring);
 205   msg = (uschar *)ssl_errstring;
 206   }
 207
 208 if (host)
 209   {
 210   log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection (%s): %s",
 211     host->name, host->address, prefix, msg);
 212   return FAIL;
 213   }
 214 else
 215   {
 216   uschar *conn_info = smtp_get_connection_info();
 217   if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
 218     conn_info += 5;
 219   /* I'd like to get separated H= here, but too hard for now */
 220   log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
 221     conn_info, prefix, msg);
 222   return DEFER;
 223   }
 224 }
 225
 226
 227
 228 /*************************************************
 229 *        Callback to generate RSA key            *
 230 *************************************************/
 231
 232 /*
 233 Arguments:
 234   s          SSL connection
 235   export     not used
 236   keylength  keylength
 237
 238 Returns:     pointer to generated key
 239 */
 240
 241 static RSA *
 242 rsa_callback(SSL *s, int export, int keylength)
 243 {
 244 RSA *rsa_key;
 245 export = export;     /* Shut picky compilers up */
 246 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
 247 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
 248 if (rsa_key == NULL)
 249   {
 250   ERR_error_string(ERR_get_error(), ssl_errstring);
 251   log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
 252     ssl_errstring);
 253   return NULL;
 254   }
 255 return rsa_key;
 256 }
 257
 258
 259
 260 /* Extreme debug
 261 #ifndef DISABLE_OCSP
 262 void
 263 x509_store_dump_cert_s_names(X509_STORE * store)
 264 {
 265 STACK_OF(X509_OBJECT) * roots= store->objs;
 266 int i;
 267 static uschar name[256];
 268
 269 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
 270   {
 271   X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
 272   if(tmp_obj->type == X509_LU_X509)
 273     {
 274     X509 * current_cert= tmp_obj->data.x509;
 275     X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
 276         name[sizeof(name)-1] = '\0';
 277     debug_printf(" %s\n", name);
 278     }
 279   }
 280 }
 281 #endif
 282 */
 283
 284
 285 #ifdef EXPERIMENTAL_EVENT
 286 static int
 287 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
 288   BOOL *calledp, const BOOL *optionalp, const uschar * what)
 289 {
 290 uschar * ev;
 291 uschar * yield;
 292 X509 * old_cert;
 293
 294 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
 295 if (ev)
 296   {
 297   old_cert = tlsp->peercert;
 298   tlsp->peercert = X509_dup(cert);
 299   /* NB we do not bother setting peerdn */
 300   if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
 301     {
 302     log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
 303                 "depth=%d cert=%s: %s",
 304               tlsp == &tls_out ? deliver_host_address : sender_host_address,
 305               what, depth, dn, yield);
 306     *calledp = TRUE;
 307     if (!*optionalp)
 308       {
 309       if (old_cert) tlsp->peercert = old_cert;  /* restore 1st failing cert */
 310       return 1;                     /* reject (leaving peercert set) */
 311       }
 312     DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
 313       "(host in tls_try_verify_hosts)\n");
 314     }
 315   X509_free(tlsp->peercert);
 316   tlsp->peercert = old_cert;
 317   }
 318 return 0;
 319 }
 320 #endif
 321
 322 /*************************************************
 323 *        Callback for verification               *
 324 *************************************************/
 325
 326 /* The SSL library does certificate verification if set up to do so. This
 327 callback has the current yes/no state is in "state". If verification succeeded,
 328 we set the certificate-verified flag. If verification failed, what happens
 329 depends on whether the client is required to present a verifiable certificate
 330 or not.
 331
 332 If verification is optional, we change the state to yes, but still log the
 333 verification error. For some reason (it really would help to have proper
 334 documentation of OpenSSL), this callback function then gets called again, this
 335 time with state = 1.  We must take care not to set the private verified flag on
 336 the second time through.
 337
 338 Note: this function is not called if the client fails to present a certificate
 339 when asked. We get here only if a certificate has been received. Handling of
 340 optional verification for this case is done when requesting SSL to verify, by
 341 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
 342
 343 May be called multiple times for different issues with a certificate, even
 344 for a given "depth" in the certificate chain.
 345
 346 Arguments:
 347   state      current yes/no state as 1/0
 348   x509ctx    certificate information.
 349   client     TRUE for client startup, FALSE for server startup
 350
 351 Returns:     1 if verified, 0 if not
 352 */
 353
 354 static int
 355 verify_callback(int state, X509_STORE_CTX *x509ctx,
 356   tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
 357 {
 358 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
 359 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
 360 uschar dn[256];
 361
 362 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
 363 dn[sizeof(dn)-1] = '\0';
 364
 365 if (state == 0)
 366   {
 367   log_write(0, LOG_MAIN, "[%s] SSL verify error: depth=%d error=%s cert=%s",
 368         tlsp == &tls_out ? deliver_host_address : sender_host_address,
 369     depth,
 370     X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
 371     dn);
 372   *calledp = TRUE;
 373   if (!*optionalp)
 374     {
 375     if (!tlsp->peercert)
 376       tlsp->peercert = X509_dup(cert);  /* record failing cert */
 377     return 0;                           /* reject */
 378     }
 379   DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
 380     "tls_try_verify_hosts)\n");
 381   }
 382
 383 else if (depth != 0)
 384   {
 385   DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
 386 #ifndef DISABLE_OCSP
 387   if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
 388     {   /* client, wanting stapling  */
 389     /* Add the server cert's signing chain as the one
 390     for the verification of the OCSP stapled information. */
 391
 392     if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
 393                              cert))
 394       ERR_clear_error();
 395     }
 396 #endif
 397 #ifdef EXPERIMENTAL_EVENT
 398     if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
 399       return 0;                         /* reject, with peercert set */
 400 #endif
 401   }
 402 else
 403   {
 404   const uschar * verify_cert_hostnames;
 405
 406   if (  tlsp == &tls_out
 407      && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
 408         /* client, wanting hostname check */
 409     {
 410
 411 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
 412 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
 413 #  define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
 414 # endif
 415 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
 416 #  define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
 417 # endif
 418     int sep = 0;
 419     const uschar * list = verify_cert_hostnames;
 420     uschar * name;
 421     int rc;
 422     while ((name = string_nextinlist(&list, &sep, NULL, 0)))
 423       if ((rc = X509_check_host(cert, name, 0,
 424                   X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
 425                   | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
 426                   NULL)))
 427         {
 428         if (rc < 0)
 429           {
 430           log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
 431                 tlsp == &tls_out ? deliver_host_address : sender_host_address);
 432           name = NULL;
 433           }
 434         break;
 435         }
 436     if (!name)
 437 #else
 438     if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
 439 #endif
 440       {
 441       log_write(0, LOG_MAIN,
 442                 "[%s] SSL verify error: certificate name mismatch: \"%s\"",
 443                 tlsp == &tls_out ? deliver_host_address : sender_host_address,
 444                 dn);
 445       *calledp = TRUE;
 446       if (!*optionalp)
 447         {
 448         if (!tlsp->peercert)
 449           tlsp->peercert = X509_dup(cert);      /* record failing cert */
 450         return 0;                               /* reject */
 451         }
 452       DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
 453         "tls_try_verify_hosts)\n");
 454       }
 455     }
 456
 457 #ifdef EXPERIMENTAL_EVENT
 458   if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
 459     return 0;                           /* reject, with peercert set */
 460 #endif
 461
 462   DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
 463     *calledp ? "" : " authenticated", dn);
 464   if (!*calledp) tlsp->certificate_verified = TRUE;
 465   *calledp = TRUE;
 466   }
 467
 468 return 1;   /* accept, at least for this level */
 469 }
 470
 471 static int
 472 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
 473 {
 474 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
 475 }
 476
 477 static int
 478 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
 479 {
 480 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
 481 }
 482
 483
 484 #ifdef EXPERIMENTAL_DANE
 485
 486 /* This gets called *by* the dane library verify callback, which interposes
 487 itself.
 488 */
 489 static int
 490 verify_callback_client_dane(int state, X509_STORE_CTX * x509ctx)
 491 {
 492 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
 493 uschar dn[256];
 494 #ifdef EXPERIMENTAL_EVENT
 495 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
 496 BOOL dummy_called, optional = FALSE;
 497 #endif
 498
 499 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
 500 dn[sizeof(dn)-1] = '\0';
 501
 502 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s\n", dn);
 503
 504 #ifdef EXPERIMENTAL_EVENT
 505   if (verify_event(&tls_out, cert, depth, dn,
 506           &dummy_called, &optional, US"DANE"))
 507     return 0;                           /* reject, with peercert set */
 508 #endif
 509
 510 if (state == 1)
 511   tls_out.dane_verified =
 512   tls_out.certificate_verified = TRUE;
 513 return 1;
 514 }
 515
 516 #endif  /*EXPERIMENTAL_DANE*/
 517
 518
 519 /*************************************************
 520 *           Information callback                 *
 521 *************************************************/
 522
 523 /* The SSL library functions call this from time to time to indicate what they
 524 are doing. We copy the string to the debugging output when TLS debugging has
 525 been requested.
 526
 527 Arguments:
 528   s         the SSL connection
 529   where
 530   ret
 531
 532 Returns:    nothing
 533 */
 534
 535 static void
 536 info_callback(SSL *s, int where, int ret)
 537 {
 538 where = where;
 539 ret = ret;
 540 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
 541 }
 542
 543
 544
 545 /*************************************************
 546 *                Initialize for DH               *
 547 *************************************************/
 548
 549 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
 550
 551 Arguments:
 552   sctx      The current SSL CTX (inbound or outbound)
 553   dhparam   DH parameter file or fixed parameter identity string
 554   host      connected host, if client; NULL if server
 555
 556 Returns:    TRUE if OK (nothing to set up, or setup worked)
 557 */
 558
 559 static BOOL
 560 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host)
 561 {
 562 BIO *bio;
 563 DH *dh;
 564 uschar *dhexpanded;
 565 const char *pem;
 566
 567 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
 568   return FALSE;
 569
 570 if (!dhexpanded || !*dhexpanded)
 571   bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
 572 else if (dhexpanded[0] == '/')
 573   {
 574   if (!(bio = BIO_new_file(CS dhexpanded, "r")))
 575     {
 576     tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
 577           host, US strerror(errno));
 578     return FALSE;
 579     }
 580   }
 581 else
 582   {
 583   if (Ustrcmp(dhexpanded, "none") == 0)
 584     {
 585     DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
 586     return TRUE;
 587     }
 588
 589   if (!(pem = std_dh_prime_named(dhexpanded)))
 590     {
 591     tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
 592         host, US strerror(errno));
 593     return FALSE;
 594     }
 595   bio = BIO_new_mem_buf(CS pem, -1);
 596   }
 597
 598 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
 599   {
 600   BIO_free(bio);
 601   tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
 602       host, NULL);
 603   return FALSE;
 604   }
 605
 606 /* Even if it is larger, we silently return success rather than cause things
 607  * to fail out, so that a too-large DH will not knock out all TLS; it's a
 608  * debatable choice. */
 609 if ((8*DH_size(dh)) > tls_dh_max_bits)
 610   {
 611   DEBUG(D_tls)
 612     debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
 613         8*DH_size(dh), tls_dh_max_bits);
 614   }
 615 else
 616   {
 617   SSL_CTX_set_tmp_dh(sctx, dh);
 618   DEBUG(D_tls)
 619     debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
 620       dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
 621   }
 622
 623 DH_free(dh);
 624 BIO_free(bio);
 625
 626 return TRUE;
 627 }
 628
 629
 630
 631
 632 /*************************************************
 633 *               Initialize for ECDH              *
 634 *************************************************/
 635
 636 /* Load parameters for ECDH encryption.
 637
 638 For now, we stick to NIST P-256 because: it's simple and easy to configure;
 639 it avoids any patent issues that might bite redistributors; despite events in
 640 the news and concerns over curve choices, we're not cryptographers, we're not
 641 pretending to be, and this is "good enough" to be better than no support,
 642 protecting against most adversaries.  Given another year or two, there might
 643 be sufficient clarity about a "right" way forward to let us make an informed
 644 decision, instead of a knee-jerk reaction.
 645
 646 Longer-term, we should look at supporting both various named curves and
 647 external files generated with "openssl ecparam", much as we do for init_dh().
 648 We should also support "none" as a value, to explicitly avoid initialisation.
 649
 650 Patches welcome.
 651
 652 Arguments:
 653   sctx      The current SSL CTX (inbound or outbound)
 654   host      connected host, if client; NULL if server
 655
 656 Returns:    TRUE if OK (nothing to set up, or setup worked)
 657 */
 658
 659 static BOOL
 660 init_ecdh(SSL_CTX * sctx, host_item * host)
 661 {
 662 #ifdef OPENSSL_NO_ECDH
 663 return TRUE;
 664 #else
 665
 666 EC_KEY * ecdh;
 667 uschar * exp_curve;
 668 int nid;
 669 BOOL rv;
 670
 671 if (host)       /* No ECDH setup for clients, only for servers */
 672   return TRUE;
 673
 674 # ifndef EXIM_HAVE_ECDH
 675 DEBUG(D_tls)
 676   debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
 677 return TRUE;
 678 # else
 679
 680 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve))
 681   return FALSE;
 682 if (!exp_curve || !*exp_curve)
 683   return TRUE;
 684
 685 #  ifdef EXIM_HAVE_OPENSSL_ECDH_AUTO
 686 /* check if new enough library to support auto ECDH temp key parameter selection */
 687 if (Ustrcmp(exp_curve, "auto") == 0)
 688   {
 689   DEBUG(D_tls) debug_printf(
 690     "ECDH temp key parameter settings: OpenSSL 1.2+ autoselection\n");
 691   SSL_CTX_set_ecdh_auto(sctx, 1);
 692   return TRUE;
 693   }
 694 #  endif
 695
 696 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
 697 if (  (nid = OBJ_sn2nid       (CCS exp_curve)) == NID_undef
 698 #   ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
 699    && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
 700 #   endif
 701    )
 702   {
 703   tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'",
 704       exp_curve),
 705     host, NULL);
 706   return FALSE;
 707   }
 708
 709 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
 710   {
 711   tls_error(US"Unable to create ec curve", host, NULL);
 712   return FALSE;
 713   }
 714
 715 /* The "tmp" in the name here refers to setting a temporary key
 716 not to the stability of the interface. */
 717
 718 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
 719   tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL);
 720 else
 721   DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
 722
 723 EC_KEY_free(ecdh);
 724 return !rv;
 725
 726 # endif /*EXIM_HAVE_ECDH*/
 727 #endif /*OPENSSL_NO_ECDH*/
 728 }
 729
 730
 731
 732
 733 #ifndef DISABLE_OCSP
 734 /*************************************************
 735 *       Load OCSP information into state         *
 736 *************************************************/
 737
 738 /* Called to load the server OCSP response from the given file into memory, once
 739 caller has determined this is needed.  Checks validity.  Debugs a message
 740 if invalid.
 741
 742 ASSUMES: single response, for single cert.
 743
 744 Arguments:
 745   sctx            the SSL_CTX* to update
 746   cbinfo          various parts of session state
 747   expanded        the filename putatively holding an OCSP response
 748
 749 */
 750
 751 static void
 752 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
 753 {
 754 BIO *bio;
 755 OCSP_RESPONSE *resp;
 756 OCSP_BASICRESP *basic_response;
 757 OCSP_SINGLERESP *single_response;
 758 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
 759 X509_STORE *store;
 760 unsigned long verify_flags;
 761 int status, reason, i;
 762
 763 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
 764 if (cbinfo->u_ocsp.server.response)
 765   {
 766   OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
 767   cbinfo->u_ocsp.server.response = NULL;
 768   }
 769
 770 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
 771 if (!bio)
 772   {
 773   DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
 774       cbinfo->u_ocsp.server.file_expanded);
 775   return;
 776   }
 777
 778 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
 779 BIO_free(bio);
 780 if (!resp)
 781   {
 782   DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
 783   return;
 784   }
 785
 786 status = OCSP_response_status(resp);
 787 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
 788   {
 789   DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
 790       OCSP_response_status_str(status), status);
 791   goto bad;
 792   }
 793
 794 basic_response = OCSP_response_get1_basic(resp);
 795 if (!basic_response)
 796   {
 797   DEBUG(D_tls)
 798     debug_printf("OCSP response parse error: unable to extract basic response.\n");
 799   goto bad;
 800   }
 801
 802 store = SSL_CTX_get_cert_store(sctx);
 803 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
 804
 805 /* May need to expose ability to adjust those flags?
 806 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
 807 OCSP_TRUSTOTHER OCSP_NOINTERN */
 808
 809 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
 810 if (i <= 0)
 811   {
 812   DEBUG(D_tls) {
 813     ERR_error_string(ERR_get_error(), ssl_errstring);
 814     debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
 815     }
 816   goto bad;
 817   }
 818
 819 /* Here's the simplifying assumption: there's only one response, for the
 820 one certificate we use, and nothing for anything else in a chain.  If this
 821 proves false, we need to extract a cert id from our issued cert
 822 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
 823 right cert in the stack and then calls OCSP_single_get0_status()).
 824
 825 I'm hoping to avoid reworking a bunch more of how we handle state here. */
 826 single_response = OCSP_resp_get0(basic_response, 0);
 827 if (!single_response)
 828   {
 829   DEBUG(D_tls)
 830     debug_printf("Unable to get first response from OCSP basic response.\n");
 831   goto bad;
 832   }
 833
 834 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
 835 if (status != V_OCSP_CERTSTATUS_GOOD)
 836   {
 837   DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
 838       OCSP_cert_status_str(status), status,
 839       OCSP_crl_reason_str(reason), reason);
 840   goto bad;
 841   }
 842
 843 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
 844   {
 845   DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
 846   goto bad;
 847   }
 848
 849 supply_response:
 850   cbinfo->u_ocsp.server.response = resp;
 851 return;
 852
 853 bad:
 854   if (running_in_test_harness)
 855     {
 856     extern char ** environ;
 857     uschar ** p;
 858     for (p = USS environ; *p != NULL; p++)
 859       if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
 860         {
 861         DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
 862         goto supply_response;
 863         }
 864     }
 865 return;
 866 }
 867 #endif  /*!DISABLE_OCSP*/
 868
 869
 870
 871
 872 /*************************************************
 873 *        Expand key and cert file specs          *
 874 *************************************************/
 875
 876 /* Called once during tls_init and possibly again during TLS setup, for a
 877 new context, if Server Name Indication was used and tls_sni was seen in
 878 the certificate string.
 879
 880 Arguments:
 881   sctx            the SSL_CTX* to update
 882   cbinfo          various parts of session state
 883
 884 Returns:          OK/DEFER/FAIL
 885 */
 886
 887 static int
 888 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
 889 {
 890 uschar *expanded;
 891
 892 if (cbinfo->certificate == NULL)
 893   return OK;
 894
 895 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
 896     Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
 897     Ustrstr(cbinfo->certificate, US"tls_out_sni")
 898    )
 899   reexpand_tls_files_for_sni = TRUE;
 900
 901 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
 902   return DEFER;
 903
 904 if (expanded != NULL)
 905   {
 906   DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
 907   if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
 908     return tls_error(string_sprintf(
 909       "SSL_CTX_use_certificate_chain_file file=%s", expanded),
 910         cbinfo->host, NULL);
 911   }
 912
 913 if (cbinfo->privatekey != NULL &&
 914     !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
 915   return DEFER;
 916
 917 /* If expansion was forced to fail, key_expanded will be NULL. If the result
 918 of the expansion is an empty string, ignore it also, and assume the private
 919 key is in the same file as the certificate. */
 920
 921 if (expanded != NULL && *expanded != 0)
 922   {
 923   DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
 924   if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
 925     return tls_error(string_sprintf(
 926       "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
 927   }
 928
 929 #ifndef DISABLE_OCSP
 930 if (cbinfo->is_server &&  cbinfo->u_ocsp.server.file != NULL)
 931   {
 932   if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
 933     return DEFER;
 934
 935   if (expanded != NULL && *expanded != 0)
 936     {
 937     DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
 938     if (cbinfo->u_ocsp.server.file_expanded &&
 939         (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
 940       {
 941       DEBUG(D_tls)
 942         debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
 943       } else {
 944         ocsp_load_response(sctx, cbinfo, expanded);
 945       }
 946     }
 947   }
 948 #endif
 949
 950 return OK;
 951 }
 952
 953
 954
 955
 956 /*************************************************
 957 *            Callback to handle SNI              *
 958 *************************************************/
 959
 960 /* Called when acting as server during the TLS session setup if a Server Name
 961 Indication extension was sent by the client.
 962
 963 API documentation is OpenSSL s_server.c implementation.
 964
 965 Arguments:
 966   s               SSL* of the current session
 967   ad              unknown (part of OpenSSL API) (unused)
 968   arg             Callback of "our" registered data
 969
 970 Returns:          SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
 971 */
 972
 973 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 974 static int
 975 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
 976 {
 977 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
 978 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
 979 int rc;
 980 int old_pool = store_pool;
 981
 982 if (!servername)
 983   return SSL_TLSEXT_ERR_OK;
 984
 985 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
 986     reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
 987
 988 /* Make the extension value available for expansion */
 989 store_pool = POOL_PERM;
 990 tls_in.sni = string_copy(US servername);
 991 store_pool = old_pool;
 992
 993 if (!reexpand_tls_files_for_sni)
 994   return SSL_TLSEXT_ERR_OK;
 995
 996 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
 997 not confident that memcpy wouldn't break some internal reference counting.
 998 Especially since there's a references struct member, which would be off. */
 999
1000 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1001   {
1002   ERR_error_string(ERR_get_error(), ssl_errstring);
1003   DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1004   return SSL_TLSEXT_ERR_NOACK;
1005   }
1006
1007 /* Not sure how many of these are actually needed, since SSL object
1008 already exists.  Might even need this selfsame callback, for reneg? */
1009
1010 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1011 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1012 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1013 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1014 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1015 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1016
1017 if (  !init_dh(server_sni, cbinfo->dhparam, NULL)
1018    || !init_ecdh(server_sni, NULL)
1019    )
1020   return SSL_TLSEXT_ERR_NOACK;
1021
1022 if (cbinfo->server_cipher_list)
1023   SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1024 #ifndef DISABLE_OCSP
1025 if (cbinfo->u_ocsp.server.file)
1026   {
1027   SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1028   SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1029   }
1030 #endif
1031
1032 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
1033 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
1034
1035 /* do this after setup_certs, because this can require the certs for verifying
1036 OCSP information. */
1037 if ((rc = tls_expand_session_files(server_sni, cbinfo)) != OK)
1038   return SSL_TLSEXT_ERR_NOACK;
1039
1040 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1041 SSL_set_SSL_CTX(s, server_sni);
1042
1043 return SSL_TLSEXT_ERR_OK;
1044 }
1045 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1046
1047
1048
1049
1050 #ifndef DISABLE_OCSP
1051
1052 /*************************************************
1053 *        Callback to handle OCSP Stapling        *
1054 *************************************************/
1055
1056 /* Called when acting as server during the TLS session setup if the client
1057 requests OCSP information with a Certificate Status Request.
1058
1059 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1060 project.
1061
1062 */
1063
1064 static int
1065 tls_server_stapling_cb(SSL *s, void *arg)
1066 {
1067 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1068 uschar *response_der;
1069 int response_der_len;
1070
1071 DEBUG(D_tls)
1072   debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1073     cbinfo->u_ocsp.server.response ? "have" : "lack");
1074
1075 tls_in.ocsp = OCSP_NOT_RESP;
1076 if (!cbinfo->u_ocsp.server.response)
1077   return SSL_TLSEXT_ERR_NOACK;
1078
1079 response_der = NULL;
1080 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1081                       &response_der);
1082 if (response_der_len <= 0)
1083   return SSL_TLSEXT_ERR_NOACK;
1084
1085 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1086 tls_in.ocsp = OCSP_VFIED;
1087 return SSL_TLSEXT_ERR_OK;
1088 }
1089
1090
1091 static void
1092 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1093 {
1094 BIO_printf(bp, "\t%s: ", str);
1095 ASN1_GENERALIZEDTIME_print(bp, time);
1096 BIO_puts(bp, "\n");
1097 }
1098
1099 static int
1100 tls_client_stapling_cb(SSL *s, void *arg)
1101 {
1102 tls_ext_ctx_cb * cbinfo = arg;
1103 const unsigned char * p;
1104 int len;
1105 OCSP_RESPONSE * rsp;
1106 OCSP_BASICRESP * bs;
1107 int i;
1108
1109 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1110 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1111 if(!p)
1112  {
1113   /* Expect this when we requested ocsp but got none */
1114   if (  cbinfo->u_ocsp.client.verify_required
1115      && log_extra_selector & LX_tls_cipher)
1116     log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1117   else
1118     DEBUG(D_tls) debug_printf(" null\n");
1119   return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1120  }
1121
1122 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1123  {
1124   tls_out.ocsp = OCSP_FAILED;
1125   if (log_extra_selector & LX_tls_cipher)
1126     log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1127   else
1128     DEBUG(D_tls) debug_printf(" parse error\n");
1129   return 0;
1130  }
1131
1132 if(!(bs = OCSP_response_get1_basic(rsp)))
1133   {
1134   tls_out.ocsp = OCSP_FAILED;
1135   if (log_extra_selector & LX_tls_cipher)
1136     log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1137   else
1138     DEBUG(D_tls) debug_printf(" error parsing response\n");
1139   OCSP_RESPONSE_free(rsp);
1140   return 0;
1141   }
1142
1143 /* We'd check the nonce here if we'd put one in the request. */
1144 /* However that would defeat cacheability on the server so we don't. */
1145
1146 /* This section of code reworked from OpenSSL apps source;
1147    The OpenSSL Project retains copyright:
1148    Copyright (c) 1999 The OpenSSL Project.  All rights reserved.
1149 */
1150   {
1151     BIO * bp = NULL;
1152     int status, reason;
1153     ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1154
1155     DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1156
1157     /*OCSP_RESPONSE_print(bp, rsp, 0);   extreme debug: stapling content */
1158
1159     /* Use the chain that verified the server cert to verify the stapled info */
1160     /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1161
1162     if ((i = OCSP_basic_verify(bs, NULL,
1163               cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1164       {
1165       tls_out.ocsp = OCSP_FAILED;
1166       if (log_extra_selector & LX_tls_cipher)
1167         log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1168       BIO_printf(bp, "OCSP response verify failure\n");
1169       ERR_print_errors(bp);
1170       i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1171       goto out;
1172       }
1173
1174     BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1175
1176       {
1177       STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1178       OCSP_SINGLERESP * single;
1179
1180       if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1181         {
1182         tls_out.ocsp = OCSP_FAILED;
1183         log_write(0, LOG_MAIN, "OCSP stapling "
1184             "with multiple responses not handled");
1185         i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1186         goto out;
1187         }
1188       single = OCSP_resp_get0(bs, 0);
1189       status = OCSP_single_get0_status(single, &reason, &rev,
1190                   &thisupd, &nextupd);
1191       }
1192
1193     DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1194     DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1195     if (!OCSP_check_validity(thisupd, nextupd,
1196           EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1197       {
1198       tls_out.ocsp = OCSP_FAILED;
1199       DEBUG(D_tls) ERR_print_errors(bp);
1200       log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1201       i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1202       }
1203     else
1204       {
1205       DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1206                     OCSP_cert_status_str(status));
1207       switch(status)
1208         {
1209         case V_OCSP_CERTSTATUS_GOOD:
1210           tls_out.ocsp = OCSP_VFIED;
1211           i = 1;
1212           break;
1213         case V_OCSP_CERTSTATUS_REVOKED:
1214           tls_out.ocsp = OCSP_FAILED;
1215           log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1216               reason != -1 ? "; reason: " : "",
1217               reason != -1 ? OCSP_crl_reason_str(reason) : "");
1218           DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1219           i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1220           break;
1221         default:
1222           tls_out.ocsp = OCSP_FAILED;
1223           log_write(0, LOG_MAIN,
1224               "Server certificate status unknown, in OCSP stapling");
1225           i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1226           break;
1227         }
1228       }
1229   out:
1230     BIO_free(bp);
1231   }
1232
1233 OCSP_RESPONSE_free(rsp);
1234 return i;
1235 }
1236 #endif  /*!DISABLE_OCSP*/
1237
1238
1239 /*************************************************
1240 *            Initialize for TLS                  *
1241 *************************************************/
1242
1243 /* Called from both server and client code, to do preliminary initialization
1244 of the library.  We allocate and return a context structure.
1245
1246 Arguments:
1247   ctxp            returned SSL context
1248   host            connected host, if client; NULL if server
1249   dhparam         DH parameter file
1250   certificate     certificate file
1251   privatekey      private key
1252   ocsp_file       file of stapling info (server); flag for require ocsp (client)
1253   addr            address if client; NULL if server (for some randomness)
1254   cbp             place to put allocated callback context
1255
1256 Returns:          OK/DEFER/FAIL
1257 */
1258
1259 static int
1260 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1261   uschar *privatekey,
1262 #ifndef DISABLE_OCSP
1263   uschar *ocsp_file,
1264 #endif
1265   address_item *addr, tls_ext_ctx_cb ** cbp)
1266 {
1267 long init_options;
1268 int rc;
1269 BOOL okay;
1270 tls_ext_ctx_cb * cbinfo;
1271
1272 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1273 cbinfo->certificate = certificate;
1274 cbinfo->privatekey = privatekey;
1275 #ifndef DISABLE_OCSP
1276 if ((cbinfo->is_server = host==NULL))
1277   {
1278   cbinfo->u_ocsp.server.file = ocsp_file;
1279   cbinfo->u_ocsp.server.file_expanded = NULL;
1280   cbinfo->u_ocsp.server.response = NULL;
1281   }
1282 else
1283   cbinfo->u_ocsp.client.verify_store = NULL;
1284 #endif
1285 cbinfo->dhparam = dhparam;
1286 cbinfo->server_cipher_list = NULL;
1287 cbinfo->host = host;
1288 #ifdef EXPERIMENTAL_EVENT
1289 cbinfo->event_action = NULL;
1290 #endif
1291
1292 SSL_load_error_strings();          /* basic set up */
1293 OpenSSL_add_ssl_algorithms();
1294
1295 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1296 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1297 list of available digests. */
1298 EVP_add_digest(EVP_sha256());
1299 #endif
1300
1301 /* Create a context.
1302 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1303 negotiation in the different methods; as far as I can tell, the only
1304 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1305 when OpenSSL is built without SSLv2 support.
1306 By disabling with openssl_options, we can let admins re-enable with the
1307 existing knob. */
1308
1309 *ctxp = SSL_CTX_new((host == NULL)?
1310   SSLv23_server_method() : SSLv23_client_method());
1311
1312 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1313
1314 /* It turns out that we need to seed the random number generator this early in
1315 order to get the full complement of ciphers to work. It took me roughly a day
1316 of work to discover this by experiment.
1317
1318 On systems that have /dev/urandom, SSL may automatically seed itself from
1319 there. Otherwise, we have to make something up as best we can. Double check
1320 afterwards. */
1321
1322 if (!RAND_status())
1323   {
1324   randstuff r;
1325   gettimeofday(&r.tv, NULL);
1326   r.p = getpid();
1327
1328   RAND_seed((uschar *)(&r), sizeof(r));
1329   RAND_seed((uschar *)big_buffer, big_buffer_size);
1330   if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1331
1332   if (!RAND_status())
1333     return tls_error(US"RAND_status", host,
1334       US"unable to seed random number generator");
1335   }
1336
1337 /* Set up the information callback, which outputs if debugging is at a suitable
1338 level. */
1339
1340 DEBUG(D_tls) SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1341
1342 /* Automatically re-try reads/writes after renegotiation. */
1343 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1344
1345 /* Apply administrator-supplied work-arounds.
1346 Historically we applied just one requested option,
1347 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1348 moved to an administrator-controlled list of options to specify and
1349 grandfathered in the first one as the default value for "openssl_options".
1350
1351 No OpenSSL version number checks: the options we accept depend upon the
1352 availability of the option value macros from OpenSSL.  */
1353
1354 okay = tls_openssl_options_parse(openssl_options, &init_options);
1355 if (!okay)
1356   return tls_error(US"openssl_options parsing failed", host, NULL);
1357
1358 if (init_options)
1359   {
1360   DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1361   if (!(SSL_CTX_set_options(*ctxp, init_options)))
1362     return tls_error(string_sprintf(
1363           "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1364   }
1365 else
1366   DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1367
1368 /* Initialize with DH parameters if supplied */
1369 /* Initialize ECDH temp key parameter selection */
1370
1371 if (  !init_dh(*ctxp, dhparam, host)
1372    || !init_ecdh(*ctxp, host)
1373    )
1374   return DEFER;
1375
1376 /* Set up certificate and key (and perhaps OCSP info) */
1377
1378 rc = tls_expand_session_files(*ctxp, cbinfo);
1379 if (rc != OK) return rc;
1380
1381 /* If we need to handle SNI, do so */
1382 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1383 if (host == NULL)               /* server */
1384   {
1385 # ifndef DISABLE_OCSP
1386   /* We check u_ocsp.server.file, not server.response, because we care about if
1387   the option exists, not what the current expansion might be, as SNI might
1388   change the certificate and OCSP file in use between now and the time the
1389   callback is invoked. */
1390   if (cbinfo->u_ocsp.server.file)
1391     {
1392     SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1393     SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1394     }
1395 # endif
1396   /* We always do this, so that $tls_sni is available even if not used in
1397   tls_certificate */
1398   SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1399   SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1400   }
1401 # ifndef DISABLE_OCSP
1402 else                    /* client */
1403   if(ocsp_file)         /* wanting stapling */
1404     {
1405     if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1406       {
1407       DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1408       return FAIL;
1409       }
1410     SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1411     SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1412     }
1413 # endif
1414 #endif
1415
1416 cbinfo->verify_cert_hostnames = NULL;
1417
1418 /* Set up the RSA callback */
1419
1420 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1421
1422 /* Finally, set the timeout, and we are done */
1423
1424 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1425 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1426
1427 *cbp = cbinfo;
1428
1429 return OK;
1430 }
1431
1432
1433
1434
1435 /*************************************************
1436 *           Get name of cipher in use            *
1437 *************************************************/
1438
1439 /*
1440 Argument:   pointer to an SSL structure for the connection
1441             buffer to use for answer
1442             size of buffer
1443             pointer to number of bits for cipher
1444 Returns:    nothing
1445 */
1446
1447 static void
1448 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1449 {
1450 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1451 yet reflect that.  It should be a safe change anyway, even 0.9.8 versions have
1452 the accessor functions use const in the prototype. */
1453 const SSL_CIPHER *c;
1454 const uschar *ver;
1455
1456 ver = (const uschar *)SSL_get_version(ssl);
1457
1458 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1459 SSL_CIPHER_get_bits(c, bits);
1460
1461 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1462   SSL_CIPHER_get_name(c), *bits);
1463
1464 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1465 }
1466
1467
1468 static void
1469 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1470 {
1471 /*XXX we might consider a list-of-certs variable for the cert chain.
1472 SSL_get_peer_cert_chain(SSL*).  We'd need a new variable type and support
1473 in list-handling functions, also consider the difference between the entire
1474 chain and the elements sent by the peer. */
1475
1476 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1477 if (!tlsp->peercert)
1478   tlsp->peercert = SSL_get_peer_certificate(ssl);
1479 /* Beware anonymous ciphers which lead to server_cert being NULL */
1480 if (tlsp->peercert)
1481   {
1482   X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1483   peerdn[bsize-1] = '\0';
1484   tlsp->peerdn = peerdn;                /*XXX a static buffer... */
1485   }
1486 else
1487   tlsp->peerdn = NULL;
1488 }
1489
1490
1491
1492
1493
1494 /*************************************************
1495 *        Set up for verifying certificates       *
1496 *************************************************/
1497
1498 /* Called by both client and server startup
1499
1500 Arguments:
1501   sctx          SSL_CTX* to initialise
1502   certs         certs file or NULL
1503   crl           CRL file or NULL
1504   host          NULL in a server; the remote host in a client
1505   optional      TRUE if called from a server for a host in tls_try_verify_hosts;
1506                 otherwise passed as FALSE
1507   cert_vfy_cb   Callback function for certificate verification
1508
1509 Returns:        OK/DEFER/FAIL
1510 */
1511
1512 static int
1513 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1514     int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1515 {
1516 uschar *expcerts, *expcrl;
1517
1518 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1519   return DEFER;
1520
1521 if (expcerts != NULL && *expcerts != '\0')
1522   {
1523   if (Ustrcmp(expcerts, "system") == 0)
1524     {
1525     /* Tell the library to use its compiled-in location for the system default
1526     CA bundle, only */
1527
1528     if (!SSL_CTX_set_default_verify_paths(sctx))
1529       return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1530     }
1531   else
1532     {
1533     struct stat statbuf;
1534
1535     /* Tell the library to use its compiled-in location for the system default
1536     CA bundle. Those given by the exim config are additional to these */
1537
1538     if (!SSL_CTX_set_default_verify_paths(sctx))
1539       return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1540
1541     if (Ustat(expcerts, &statbuf) < 0)
1542       {
1543       log_write(0, LOG_MAIN|LOG_PANIC,
1544         "failed to stat %s for certificates", expcerts);
1545       return DEFER;
1546       }
1547     else
1548       {
1549       uschar *file, *dir;
1550       if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1551         { file = NULL; dir = expcerts; }
1552       else
1553         { file = expcerts; dir = NULL; }
1554
1555       /* If a certificate file is empty, the next function fails with an
1556       unhelpful error message. If we skip it, we get the correct behaviour (no
1557       certificates are recognized, but the error message is still misleading (it
1558       says no certificate was supplied.) But this is better. */
1559
1560       if ((file == NULL || statbuf.st_size > 0) &&
1561             !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1562         return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1563
1564       /* Load the list of CAs for which we will accept certs, for sending
1565       to the client.  This is only for the one-file tls_verify_certificates
1566       variant.
1567       If a list isn't loaded into the server, but
1568       some verify locations are set, the server end appears to make
1569       a wildcard reqest for client certs.
1570       Meanwhile, the client library as deafult behaviour *ignores* the list
1571       we send over the wire - see man SSL_CTX_set_client_cert_cb.
1572       Because of this, and that the dir variant is likely only used for
1573       the public-CA bundle (not for a private CA), not worth fixing.
1574       */
1575       if (file != NULL)
1576         {
1577         STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1578   DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1579                                     sk_X509_NAME_num(names));
1580         SSL_CTX_set_client_CA_list(sctx, names);
1581         }
1582       }
1583     }
1584
1585   /* Handle a certificate revocation list. */
1586
1587   #if OPENSSL_VERSION_NUMBER > 0x00907000L
1588
1589   /* This bit of code is now the version supplied by Lars Mainka. (I have
1590    * merely reformatted it into the Exim code style.)
1591
1592    * "From here I changed the code to add support for multiple crl's
1593    * in pem format in one file or to support hashed directory entries in
1594    * pem format instead of a file. This method now uses the library function
1595    * X509_STORE_load_locations to add the CRL location to the SSL context.
1596    * OpenSSL will then handle the verify against CA certs and CRLs by
1597    * itself in the verify callback." */
1598
1599   if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1600   if (expcrl != NULL && *expcrl != 0)
1601     {
1602     struct stat statbufcrl;
1603     if (Ustat(expcrl, &statbufcrl) < 0)
1604       {
1605       log_write(0, LOG_MAIN|LOG_PANIC,
1606         "failed to stat %s for certificates revocation lists", expcrl);
1607       return DEFER;
1608       }
1609     else
1610       {
1611       /* is it a file or directory? */
1612       uschar *file, *dir;
1613       X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1614       if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1615         {
1616         file = NULL;
1617         dir = expcrl;
1618         DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1619         }
1620       else
1621         {
1622         file = expcrl;
1623         dir = NULL;
1624         DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1625         }
1626       if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1627         return tls_error(US"X509_STORE_load_locations", host, NULL);
1628
1629       /* setting the flags to check against the complete crl chain */
1630
1631       X509_STORE_set_flags(cvstore,
1632         X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1633       }
1634     }
1635
1636   #endif  /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1637
1638   /* If verification is optional, don't fail if no certificate */
1639
1640   SSL_CTX_set_verify(sctx,
1641     SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1642     cert_vfy_cb);
1643   }
1644
1645 return OK;
1646 }
1647
1648
1649
1650 /*************************************************
1651 *       Start a TLS session in a server          *
1652 *************************************************/
1653
1654 /* This is called when Exim is running as a server, after having received
1655 the STARTTLS command. It must respond to that command, and then negotiate
1656 a TLS session.
1657
1658 Arguments:
1659   require_ciphers   allowed ciphers
1660
1661 Returns:            OK on success
1662                     DEFER for errors before the start of the negotiation
1663                     FAIL for errors during the negotation; the server can't
1664                       continue running.
1665 */
1666
1667 int
1668 tls_server_start(const uschar *require_ciphers)
1669 {
1670 int rc;
1671 uschar *expciphers;
1672 tls_ext_ctx_cb *cbinfo;
1673 static uschar peerdn[256];
1674 static uschar cipherbuf[256];
1675
1676 /* Check for previous activation */
1677
1678 if (tls_in.active >= 0)
1679   {
1680   tls_error(US"STARTTLS received after TLS started", NULL, US"");
1681   smtp_printf("554 Already in TLS\r\n");
1682   return FAIL;
1683   }
1684
1685 /* Initialize the SSL library. If it fails, it will already have logged
1686 the error. */
1687
1688 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1689 #ifndef DISABLE_OCSP
1690     tls_ocsp_file,
1691 #endif
1692     NULL, &server_static_cbinfo);
1693 if (rc != OK) return rc;
1694 cbinfo = server_static_cbinfo;
1695
1696 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1697   return FAIL;
1698
1699 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1700 were historically separated by underscores. So that I can use either form in my
1701 tests, and also for general convenience, we turn underscores into hyphens here.
1702 */
1703
1704 if (expciphers != NULL)
1705   {
1706   uschar *s = expciphers;
1707   while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1708   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1709   if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1710     return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1711   cbinfo->server_cipher_list = expciphers;
1712   }
1713
1714 /* If this is a host for which certificate verification is mandatory or
1715 optional, set up appropriately. */
1716
1717 tls_in.certificate_verified = FALSE;
1718 #ifdef EXPERIMENTAL_DANE
1719 tls_in.dane_verified = FALSE;
1720 #endif
1721 server_verify_callback_called = FALSE;
1722
1723 if (verify_check_host(&tls_verify_hosts) == OK)
1724   {
1725   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1726                         FALSE, verify_callback_server);
1727   if (rc != OK) return rc;
1728   server_verify_optional = FALSE;
1729   }
1730 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1731   {
1732   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1733                         TRUE, verify_callback_server);
1734   if (rc != OK) return rc;
1735   server_verify_optional = TRUE;
1736   }
1737
1738 /* Prepare for new connection */
1739
1740 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1741
1742 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1743  *
1744  * With the SSL_clear(), we get strange interoperability bugs with
1745  * OpenSSL 1.0.1b and TLS1.1/1.2.  It looks as though this may be a bug in
1746  * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1747  *
1748  * The SSL_clear() call is to let an existing SSL* be reused, typically after
1749  * session shutdown.  In this case, we have a brand new object and there's no
1750  * obvious reason to immediately clear it.  I'm guessing that this was
1751  * originally added because of incomplete initialisation which the clear fixed,
1752  * in some historic release.
1753  */
1754
1755 /* Set context and tell client to go ahead, except in the case of TLS startup
1756 on connection, where outputting anything now upsets the clients and tends to
1757 make them disconnect. We need to have an explicit fflush() here, to force out
1758 the response. Other smtp_printf() calls do not need it, because in non-TLS
1759 mode, the fflush() happens when smtp_getc() is called. */
1760
1761 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1762 if (!tls_in.on_connect)
1763   {
1764   smtp_printf("220 TLS go ahead\r\n");
1765   fflush(smtp_out);
1766   }
1767
1768 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1769 that the OpenSSL library doesn't. */
1770
1771 SSL_set_wfd(server_ssl, fileno(smtp_out));
1772 SSL_set_rfd(server_ssl, fileno(smtp_in));
1773 SSL_set_accept_state(server_ssl);
1774
1775 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1776
1777 sigalrm_seen = FALSE;
1778 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1779 rc = SSL_accept(server_ssl);
1780 alarm(0);
1781
1782 if (rc <= 0)
1783   {
1784   tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1785   if (ERR_get_error() == 0)
1786     log_write(0, LOG_MAIN,
1787         "TLS client disconnected cleanly (rejected our certificate?)");
1788   return FAIL;
1789   }
1790
1791 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1792
1793 /* TLS has been set up. Adjust the input functions to read via TLS,
1794 and initialize things. */
1795
1796 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
1797
1798 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1799 tls_in.cipher = cipherbuf;
1800
1801 DEBUG(D_tls)
1802   {
1803   uschar buf[2048];
1804   if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1805     debug_printf("Shared ciphers: %s\n", buf);
1806   }
1807
1808 /* Record the certificate we presented */
1809   {
1810   X509 * crt = SSL_get_certificate(server_ssl);
1811   tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1812   }
1813
1814 /* Only used by the server-side tls (tls_in), including tls_getc.
1815    Client-side (tls_out) reads (seem to?) go via
1816    smtp_read_response()/ip_recv().
1817    Hence no need to duplicate for _in and _out.
1818  */
1819 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1820 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1821 ssl_xfer_eof = ssl_xfer_error = 0;
1822
1823 receive_getc = tls_getc;
1824 receive_ungetc = tls_ungetc;
1825 receive_feof = tls_feof;
1826 receive_ferror = tls_ferror;
1827 receive_smtp_buffered = tls_smtp_buffered;
1828
1829 tls_in.active = fileno(smtp_out);
1830 return OK;
1831 }
1832
1833
1834
1835
1836 static int
1837 tls_client_basic_ctx_init(SSL_CTX * ctx,
1838     host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo
1839                           )
1840 {
1841 int rc;
1842 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1843    set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1844    the specified host patterns if one of them is defined */
1845
1846 if (  (  !ob->tls_verify_hosts
1847       && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
1848       )
1849    || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
1850    )
1851   client_verify_optional = FALSE;
1852 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
1853   client_verify_optional = TRUE;
1854 else
1855   return OK;
1856
1857 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
1858       ob->tls_crl, host, client_verify_optional, verify_callback_client)) != OK)
1859   return rc;
1860
1861 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
1862   {
1863   cbinfo->verify_cert_hostnames =
1864 #ifdef EXPERIMENTAL_INTERNATIONAL
1865     string_domain_utf8_to_alabel(host->name, NULL);
1866 #else
1867     host->name;
1868 #endif
1869   DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1870                     cbinfo->verify_cert_hostnames);
1871   }
1872 return OK;
1873 }
1874
1875
1876 #ifdef EXPERIMENTAL_DANE
1877 static int
1878 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa)
1879 {
1880 dns_record * rr;
1881 dns_scan dnss;
1882 const char * hostnames[2] = { CS host->name, NULL };
1883 int found = 0;
1884
1885 if (DANESSL_init(ssl, NULL, hostnames) != 1)
1886   return tls_error(US"hostnames load", host, NULL);
1887
1888 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
1889      rr;
1890      rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
1891     ) if (rr->type == T_TLSA)
1892   {
1893   uschar * p = rr->data;
1894   uint8_t usage, selector, mtype;
1895   const char * mdname;
1896
1897   usage = *p++;
1898
1899   /* Only DANE-TA(2) and DANE-EE(3) are supported */
1900   if (usage != 2 && usage != 3) continue;
1901
1902   selector = *p++;
1903   mtype = *p++;
1904
1905   switch (mtype)
1906     {
1907     default: continue;  /* Only match-types 0, 1, 2 are supported */
1908     case 0:  mdname = NULL; break;
1909     case 1:  mdname = "sha256"; break;
1910     case 2:  mdname = "sha512"; break;
1911     }
1912
1913   found++;
1914   switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
1915     {
1916     default:
1917     case 0:     /* action not taken */
1918       return tls_error(US"tlsa load", host, NULL);
1919     case 1:     break;
1920     }
1921
1922   tls_out.tlsa_usage |= 1<<usage;
1923   }
1924
1925 if (found)
1926   return OK;
1927
1928 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
1929 return DEFER;
1930 }
1931 #endif  /*EXPERIMENTAL_DANE*/
1932
1933
1934
1935 /*************************************************
1936 *    Start a TLS session in a client             *
1937 *************************************************/
1938
1939 /* Called from the smtp transport after STARTTLS has been accepted.
1940
1941 Argument:
1942   fd               the fd of the connection
1943   host             connected host (for messages)
1944   addr             the first address
1945   tb               transport (always smtp)
1946   tlsa_dnsa        tlsa lookup, if DANE, else null
1947
1948 Returns:           OK on success
1949                    FAIL otherwise - note that tls_error() will not give DEFER
1950                      because this is not a server
1951 */
1952
1953 int
1954 tls_client_start(int fd, host_item *host, address_item *addr,
1955   transport_instance *tb
1956 #ifdef EXPERIMENTAL_DANE
1957   , dns_answer * tlsa_dnsa
1958 #endif
1959   )
1960 {
1961 smtp_transport_options_block * ob =
1962   (smtp_transport_options_block *)tb->options_block;
1963 static uschar peerdn[256];
1964 uschar * expciphers;
1965 int rc;
1966 static uschar cipherbuf[256];
1967
1968 #ifndef DISABLE_OCSP
1969 BOOL request_ocsp = FALSE;
1970 BOOL require_ocsp = FALSE;
1971 #endif
1972
1973 #ifdef EXPERIMENTAL_DANE
1974 tls_out.tlsa_usage = 0;
1975 #endif
1976
1977 #ifndef DISABLE_OCSP
1978   {
1979 # ifdef EXPERIMENTAL_DANE
1980   if (  tlsa_dnsa
1981      && ob->hosts_request_ocsp[0] == '*'
1982      && ob->hosts_request_ocsp[1] == '\0'
1983      )
1984     {
1985     /* Unchanged from default.  Use a safer one under DANE */
1986     request_ocsp = TRUE;
1987     ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
1988                                       "   {= {4}{$tls_out_tlsa_usage}} } "
1989                                  " {*}{}}";
1990     }
1991 # endif
1992
1993   if ((require_ocsp =
1994         verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
1995     request_ocsp = TRUE;
1996   else
1997 # ifdef EXPERIMENTAL_DANE
1998     if (!request_ocsp)
1999 # endif
2000       request_ocsp =
2001         verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2002   }
2003 #endif
2004
2005 rc = tls_init(&client_ctx, host, NULL,
2006     ob->tls_certificate, ob->tls_privatekey,
2007 #ifndef DISABLE_OCSP
2008     (void *)(long)request_ocsp,
2009 #endif
2010     addr, &client_static_cbinfo);
2011 if (rc != OK) return rc;
2012
2013 tls_out.certificate_verified = FALSE;
2014 client_verify_callback_called = FALSE;
2015
2016 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2017     &expciphers))
2018   return FAIL;
2019
2020 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2021 are separated by underscores. So that I can use either form in my tests, and
2022 also for general convenience, we turn underscores into hyphens here. */
2023
2024 if (expciphers != NULL)
2025   {
2026   uschar *s = expciphers;
2027   while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2028   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2029   if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2030     return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
2031   }
2032
2033 #ifdef EXPERIMENTAL_DANE
2034 if (tlsa_dnsa)
2035   {
2036   SSL_CTX_set_verify(client_ctx,
2037     SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2038     verify_callback_client_dane);
2039
2040   if (!DANESSL_library_init())
2041     return tls_error(US"library init", host, NULL);
2042   if (DANESSL_CTX_init(client_ctx) <= 0)
2043     return tls_error(US"context init", host, NULL);
2044   }
2045 else
2046
2047 #endif
2048
2049   if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob, client_static_cbinfo))
2050       != OK)
2051     return rc;
2052
2053 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2054   return tls_error(US"SSL_new", host, NULL);
2055 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2056 SSL_set_fd(client_ssl, fd);
2057 SSL_set_connect_state(client_ssl);
2058
2059 if (ob->tls_sni)
2060   {
2061   if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
2062     return FAIL;
2063   if (tls_out.sni == NULL)
2064     {
2065     DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2066     }
2067   else if (!Ustrlen(tls_out.sni))
2068     tls_out.sni = NULL;
2069   else
2070     {
2071 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2072     DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2073     SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2074 #else
2075     DEBUG(D_tls)
2076       debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
2077           tls_out.sni);
2078 #endif
2079     }
2080   }
2081
2082 #ifdef EXPERIMENTAL_DANE
2083 if (tlsa_dnsa)
2084   if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa)) != OK)
2085     return rc;
2086 #endif
2087
2088 #ifndef DISABLE_OCSP
2089 /* Request certificate status at connection-time.  If the server
2090 does OCSP stapling we will get the callback (set in tls_init()) */
2091 # ifdef EXPERIMENTAL_DANE
2092 if (request_ocsp)
2093   {
2094   const uschar * s;
2095   if (  ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2096      || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2097      )
2098     {   /* Re-eval now $tls_out_tlsa_usage is populated.  If
2099         this means we avoid the OCSP request, we wasted the setup
2100         cost in tls_init(). */
2101     require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2102     request_ocsp = require_ocsp
2103       || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2104     }
2105   }
2106 # endif
2107
2108 if (request_ocsp)
2109   {
2110   SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2111   client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2112   tls_out.ocsp = OCSP_NOT_RESP;
2113   }
2114 #endif
2115
2116 #ifdef EXPERIMENTAL_EVENT
2117 client_static_cbinfo->event_action = tb->event_action;
2118 #endif
2119
2120 /* There doesn't seem to be a built-in timeout on connection. */
2121
2122 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2123 sigalrm_seen = FALSE;
2124 alarm(ob->command_timeout);
2125 rc = SSL_connect(client_ssl);
2126 alarm(0);
2127
2128 #ifdef EXPERIMENTAL_DANE
2129 if (tlsa_dnsa)
2130   DANESSL_cleanup(client_ssl);
2131 #endif
2132
2133 if (rc <= 0)
2134   return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
2135
2136 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2137
2138 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2139
2140 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2141 tls_out.cipher = cipherbuf;
2142
2143 /* Record the certificate we presented */
2144   {
2145   X509 * crt = SSL_get_certificate(client_ssl);
2146   tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2147   }
2148
2149 tls_out.active = fd;
2150 return OK;
2151 }
2152
2153
2154
2155
2156
2157 /*************************************************
2158 *            TLS version of getc                 *
2159 *************************************************/
2160
2161 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2162 it refills the buffer via the SSL reading function.
2163
2164 Arguments:  none
2165 Returns:    the next character or EOF
2166
2167 Only used by the server-side TLS.
2168 */
2169
2170 int
2171 tls_getc(void)
2172 {
2173 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2174   {
2175   int error;
2176   int inbytes;
2177
2178   DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2179     ssl_xfer_buffer, ssl_xfer_buffer_size);
2180
2181   if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2182   inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
2183   error = SSL_get_error(server_ssl, inbytes);
2184   alarm(0);
2185
2186   /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2187   closed down, not that the socket itself has been closed down. Revert to
2188   non-SSL handling. */
2189
2190   if (error == SSL_ERROR_ZERO_RETURN)
2191     {
2192     DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2193
2194     receive_getc = smtp_getc;
2195     receive_ungetc = smtp_ungetc;
2196     receive_feof = smtp_feof;
2197     receive_ferror = smtp_ferror;
2198     receive_smtp_buffered = smtp_buffered;
2199
2200     SSL_free(server_ssl);
2201     server_ssl = NULL;
2202     tls_in.active = -1;
2203     tls_in.bits = 0;
2204     tls_in.cipher = NULL;
2205     tls_in.peerdn = NULL;
2206     tls_in.sni = NULL;
2207
2208     return smtp_getc();
2209     }
2210
2211   /* Handle genuine errors */
2212
2213   else if (error == SSL_ERROR_SSL)
2214     {
2215     ERR_error_string(ERR_get_error(), ssl_errstring);
2216     log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2217     ssl_xfer_error = 1;
2218     return EOF;
2219     }
2220
2221   else if (error != SSL_ERROR_NONE)
2222     {
2223     DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2224     ssl_xfer_error = 1;
2225     return EOF;
2226     }
2227
2228 #ifndef DISABLE_DKIM
2229   dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2230 #endif
2231   ssl_xfer_buffer_hwm = inbytes;
2232   ssl_xfer_buffer_lwm = 0;
2233   }
2234
2235 /* Something in the buffer; return next uschar */
2236
2237 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2238 }
2239
2240
2241
2242 /*************************************************
2243 *          Read bytes from TLS channel           *
2244 *************************************************/
2245
2246 /*
2247 Arguments:
2248   buff      buffer of data
2249   len       size of buffer
2250
2251 Returns:    the number of bytes read
2252             -1 after a failed read
2253
2254 Only used by the client-side TLS.
2255 */
2256
2257 int
2258 tls_read(BOOL is_server, uschar *buff, size_t len)
2259 {
2260 SSL *ssl = is_server ? server_ssl : client_ssl;
2261 int inbytes;
2262 int error;
2263
2264 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2265   buff, (unsigned int)len);
2266
2267 inbytes = SSL_read(ssl, CS buff, len);
2268 error = SSL_get_error(ssl, inbytes);
2269
2270 if (error == SSL_ERROR_ZERO_RETURN)
2271   {
2272   DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2273   return -1;
2274   }
2275 else if (error != SSL_ERROR_NONE)
2276   {
2277   return -1;
2278   }
2279
2280 return inbytes;
2281 }
2282
2283
2284
2285
2286
2287 /*************************************************
2288 *         Write bytes down TLS channel           *
2289 *************************************************/
2290
2291 /*
2292 Arguments:
2293   is_server channel specifier
2294   buff      buffer of data
2295   len       number of bytes
2296
2297 Returns:    the number of bytes after a successful write,
2298             -1 after a failed write
2299
2300 Used by both server-side and client-side TLS.
2301 */
2302
2303 int
2304 tls_write(BOOL is_server, const uschar *buff, size_t len)
2305 {
2306 int outbytes;
2307 int error;
2308 int left = len;
2309 SSL *ssl = is_server ? server_ssl : client_ssl;
2310
2311 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
2312 while (left > 0)
2313   {
2314   DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2315   outbytes = SSL_write(ssl, CS buff, left);
2316   error = SSL_get_error(ssl, outbytes);
2317   DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2318   switch (error)
2319     {
2320     case SSL_ERROR_SSL:
2321     ERR_error_string(ERR_get_error(), ssl_errstring);
2322     log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2323     return -1;
2324
2325     case SSL_ERROR_NONE:
2326     left -= outbytes;
2327     buff += outbytes;
2328     break;
2329
2330     case SSL_ERROR_ZERO_RETURN:
2331     log_write(0, LOG_MAIN, "SSL channel closed on write");
2332     return -1;
2333
2334     case SSL_ERROR_SYSCALL:
2335     log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2336       sender_fullhost ? sender_fullhost : US"<unknown>",
2337       strerror(errno));
2338
2339     default:
2340     log_write(0, LOG_MAIN, "SSL_write error %d", error);
2341     return -1;
2342     }
2343   }
2344 return len;
2345 }
2346
2347
2348
2349 /*************************************************
2350 *         Close down a TLS session               *
2351 *************************************************/
2352
2353 /* This is also called from within a delivery subprocess forked from the
2354 daemon, to shut down the TLS library, without actually doing a shutdown (which
2355 would tamper with the SSL session in the parent process).
2356
2357 Arguments:   TRUE if SSL_shutdown is to be called
2358 Returns:     nothing
2359
2360 Used by both server-side and client-side TLS.
2361 */
2362
2363 void
2364 tls_close(BOOL is_server, BOOL shutdown)
2365 {
2366 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2367 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2368
2369 if (*fdp < 0) return;  /* TLS was not active */
2370
2371 if (shutdown)
2372   {
2373   DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2374   SSL_shutdown(*sslp);
2375   }
2376
2377 SSL_free(*sslp);
2378 *sslp = NULL;
2379
2380 *fdp = -1;
2381 }
2382
2383
2384
2385
2386 /*************************************************
2387 *  Let tls_require_ciphers be checked at startup *
2388 *************************************************/
2389
2390 /* The tls_require_ciphers option, if set, must be something which the
2391 library can parse.
2392
2393 Returns:     NULL on success, or error message
2394 */
2395
2396 uschar *
2397 tls_validate_require_cipher(void)
2398 {
2399 SSL_CTX *ctx;
2400 uschar *s, *expciphers, *err;
2401
2402 /* this duplicates from tls_init(), we need a better "init just global
2403 state, for no specific purpose" singleton function of our own */
2404
2405 SSL_load_error_strings();
2406 OpenSSL_add_ssl_algorithms();
2407 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2408 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2409 list of available digests. */
2410 EVP_add_digest(EVP_sha256());
2411 #endif
2412
2413 if (!(tls_require_ciphers && *tls_require_ciphers))
2414   return NULL;
2415
2416 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
2417   return US"failed to expand tls_require_ciphers";
2418
2419 if (!(expciphers && *expciphers))
2420   return NULL;
2421
2422 /* normalisation ripped from above */
2423 s = expciphers;
2424 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2425
2426 err = NULL;
2427
2428 ctx = SSL_CTX_new(SSLv23_server_method());
2429 if (!ctx)
2430   {
2431   ERR_error_string(ERR_get_error(), ssl_errstring);
2432   return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2433   }
2434
2435 DEBUG(D_tls)
2436   debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2437
2438 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2439   {
2440   ERR_error_string(ERR_get_error(), ssl_errstring);
2441   err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2442   }
2443
2444 SSL_CTX_free(ctx);
2445
2446 return err;
2447 }
2448
2449
2450
2451
2452 /*************************************************
2453 *         Report the library versions.           *
2454 *************************************************/
2455
2456 /* There have historically been some issues with binary compatibility in
2457 OpenSSL libraries; if Exim (like many other applications) is built against
2458 one version of OpenSSL but the run-time linker picks up another version,
2459 it can result in serious failures, including crashing with a SIGSEGV.  So
2460 report the version found by the compiler and the run-time version.
2461
2462 Note: some OS vendors backport security fixes without changing the version
2463 number/string, and the version date remains unchanged.  The _build_ date
2464 will change, so we can more usefully assist with version diagnosis by also
2465 reporting the build date.
2466
2467 Arguments:   a FILE* to print the results to
2468 Returns:     nothing
2469 */
2470
2471 void
2472 tls_version_report(FILE *f)
2473 {
2474 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2475            "                          Runtime: %s\n"
2476            "                                 : %s\n",
2477            OPENSSL_VERSION_TEXT,
2478            SSLeay_version(SSLEAY_VERSION),
2479            SSLeay_version(SSLEAY_BUILT_ON));
2480 /* third line is 38 characters for the %s and the line is 73 chars long;
2481 the OpenSSL output includes a "built on: " prefix already. */
2482 }
2483
2484
2485
2486
2487 /*************************************************
2488 *            Random number generation            *
2489 *************************************************/
2490
2491 /* Pseudo-random number generation.  The result is not expected to be
2492 cryptographically strong but not so weak that someone will shoot themselves
2493 in the foot using it as a nonce in input in some email header scheme or
2494 whatever weirdness they'll twist this into.  The result should handle fork()
2495 and avoid repeating sequences.  OpenSSL handles that for us.
2496
2497 Arguments:
2498   max       range maximum
2499 Returns     a random number in range [0, max-1]
2500 */
2501
2502 int
2503 vaguely_random_number(int max)
2504 {
2505 unsigned int r;
2506 int i, needed_len;
2507 static pid_t pidlast = 0;
2508 pid_t pidnow;
2509 uschar *p;
2510 uschar smallbuf[sizeof(r)];
2511
2512 if (max <= 1)
2513   return 0;
2514
2515 pidnow = getpid();
2516 if (pidnow != pidlast)
2517   {
2518   /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2519   is unique for each thread", this doesn't apparently apply across processes,
2520   so our own warning from vaguely_random_number_fallback() applies here too.
2521   Fix per PostgreSQL. */
2522   if (pidlast != 0)
2523     RAND_cleanup();
2524   pidlast = pidnow;
2525   }
2526
2527 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2528 if (!RAND_status())
2529   {
2530   randstuff r;
2531   gettimeofday(&r.tv, NULL);
2532   r.p = getpid();
2533
2534   RAND_seed((uschar *)(&r), sizeof(r));
2535   }
2536 /* We're after pseudo-random, not random; if we still don't have enough data
2537 in the internal PRNG then our options are limited.  We could sleep and hope
2538 for entropy to come along (prayer technique) but if the system is so depleted
2539 in the first place then something is likely to just keep taking it.  Instead,
2540 we'll just take whatever little bit of pseudo-random we can still manage to
2541 get. */
2542
2543 needed_len = sizeof(r);
2544 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2545 asked for a number less than 10. */
2546 for (r = max, i = 0; r; ++i)
2547   r >>= 1;
2548 i = (i + 7) / 8;
2549 if (i < needed_len)
2550   needed_len = i;
2551
2552 /* We do not care if crypto-strong */
2553 i = RAND_pseudo_bytes(smallbuf, needed_len);
2554 if (i < 0)
2555   {
2556   DEBUG(D_all)
2557     debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2558   return vaguely_random_number_fallback(max);
2559   }
2560
2561 r = 0;
2562 for (p = smallbuf; needed_len; --needed_len, ++p)
2563   {
2564   r *= 256;
2565   r += *p;
2566   }
2567
2568 /* We don't particularly care about weighted results; if someone wants
2569 smooth distribution and cares enough then they should submit a patch then. */
2570 return r % max;
2571 }
2572
2573
2574
2575
2576 /*************************************************
2577 *        OpenSSL option parse                    *
2578 *************************************************/
2579
2580 /* Parse one option for tls_openssl_options_parse below
2581
2582 Arguments:
2583   name    one option name
2584   value   place to store a value for it
2585 Returns   success or failure in parsing
2586 */
2587
2588 struct exim_openssl_option {
2589   uschar *name;
2590   long    value;
2591 };
2592 /* We could use a macro to expand, but we need the ifdef and not all the
2593 options document which version they were introduced in.  Policylet: include
2594 all options unless explicitly for DTLS, let the administrator choose which
2595 to apply.
2596
2597 This list is current as of:
2598   ==>  1.0.1b  <==
2599 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2600 */
2601 static struct exim_openssl_option exim_openssl_options[] = {
2602 /* KEEP SORTED ALPHABETICALLY! */
2603 #ifdef SSL_OP_ALL
2604   { US"all", SSL_OP_ALL },
2605 #endif
2606 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2607   { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2608 #endif
2609 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2610   { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2611 #endif
2612 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2613   { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2614 #endif
2615 #ifdef SSL_OP_EPHEMERAL_RSA
2616   { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2617 #endif
2618 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2619   { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2620 #endif
2621 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2622   { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2623 #endif
2624 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2625   { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2626 #endif
2627 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2628   { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2629 #endif
2630 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2631   { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2632 #endif
2633 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2634   { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2635 #endif
2636 #ifdef SSL_OP_NO_COMPRESSION
2637   { US"no_compression", SSL_OP_NO_COMPRESSION },
2638 #endif
2639 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2640   { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2641 #endif
2642 #ifdef SSL_OP_NO_SSLv2
2643   { US"no_sslv2", SSL_OP_NO_SSLv2 },
2644 #endif
2645 #ifdef SSL_OP_NO_SSLv3
2646   { US"no_sslv3", SSL_OP_NO_SSLv3 },
2647 #endif
2648 #ifdef SSL_OP_NO_TICKET
2649   { US"no_ticket", SSL_OP_NO_TICKET },
2650 #endif
2651 #ifdef SSL_OP_NO_TLSv1
2652   { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2653 #endif
2654 #ifdef SSL_OP_NO_TLSv1_1
2655 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2656   /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2657 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2658 #else
2659   { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2660 #endif
2661 #endif
2662 #ifdef SSL_OP_NO_TLSv1_2
2663   { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2664 #endif
2665 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2666   { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2667 #endif
2668 #ifdef SSL_OP_SINGLE_DH_USE
2669   { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2670 #endif
2671 #ifdef SSL_OP_SINGLE_ECDH_USE
2672   { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2673 #endif
2674 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2675   { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2676 #endif
2677 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2678   { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2679 #endif
2680 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2681   { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2682 #endif
2683 #ifdef SSL_OP_TLS_D5_BUG
2684   { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2685 #endif
2686 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2687   { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2688 #endif
2689 };
2690 static int exim_openssl_options_size =
2691   sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2692
2693
2694 static BOOL
2695 tls_openssl_one_option_parse(uschar *name, long *value)
2696 {
2697 int first = 0;
2698 int last = exim_openssl_options_size;
2699 while (last > first)
2700   {
2701   int middle = (first + last)/2;
2702   int c = Ustrcmp(name, exim_openssl_options[middle].name);
2703   if (c == 0)
2704     {
2705     *value = exim_openssl_options[middle].value;
2706     return TRUE;
2707     }
2708   else if (c > 0)
2709     first = middle + 1;
2710   else
2711     last = middle;
2712   }
2713 return FALSE;
2714 }
2715
2716
2717
2718
2719 /*************************************************
2720 *        OpenSSL option parsing logic            *
2721 *************************************************/
2722
2723 /* OpenSSL has a number of compatibility options which an administrator might
2724 reasonably wish to set.  Interpret a list similarly to decode_bits(), so that
2725 we look like log_selector.
2726
2727 Arguments:
2728   option_spec  the administrator-supplied string of options
2729   results      ptr to long storage for the options bitmap
2730 Returns        success or failure
2731 */
2732
2733 BOOL
2734 tls_openssl_options_parse(uschar *option_spec, long *results)
2735 {
2736 long result, item;
2737 uschar *s, *end;
2738 uschar keep_c;
2739 BOOL adding, item_parsed;
2740
2741 result = 0L;
2742 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2743  * from default because it increases BEAST susceptibility. */
2744 #ifdef SSL_OP_NO_SSLv2
2745 result |= SSL_OP_NO_SSLv2;
2746 #endif
2747
2748 if (option_spec == NULL)
2749   {
2750   *results = result;
2751   return TRUE;
2752   }
2753
2754 for (s=option_spec; *s != '\0'; /**/)
2755   {
2756   while (isspace(*s)) ++s;
2757   if (*s == '\0')
2758     break;
2759   if (*s != '+' && *s != '-')
2760     {
2761     DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2762         "+ or - expected but found \"%s\"\n", s);
2763     return FALSE;
2764     }
2765   adding = *s++ == '+';
2766   for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2767   keep_c = *end;
2768   *end = '\0';
2769   item_parsed = tls_openssl_one_option_parse(s, &item);
2770   if (!item_parsed)
2771     {
2772     DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2773     return FALSE;
2774     }
2775   DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2776       adding ? "adding" : "removing", result, item, s);
2777   if (adding)
2778     result |= item;
2779   else
2780     result &= ~item;
2781   *end = keep_c;
2782   s = end;
2783   }
2784
2785 *results = result;
2786 return TRUE;
2787 }
2788
2789 /* vi: aw ai sw=2
2790 */
2791 /* End of tls-openssl.c */