src/src/tls-openssl.c

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