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