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, 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, 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, SSL_VERIFY_PEER, verify_callback_client_dane);
1874
1875   if (!DANESSL_library_init())
1876     return tls_error(US"library init", host, NULL);
1877   if (DANESSL_CTX_init(client_ctx) <= 0)
1878     return tls_error(US"context init", host, NULL);
1879   }
1880 else
1881
1882 #endif
1883
1884   if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob, client_static_cbinfo))
1885       != OK)
1886     return rc;
1887
1888 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1889   return tls_error(US"SSL_new", host, NULL);
1890 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1891 SSL_set_fd(client_ssl, fd);
1892 SSL_set_connect_state(client_ssl);
1893
1894 if (ob->tls_sni)
1895   {
1896   if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1897     return FAIL;
1898   if (tls_out.sni == NULL)
1899     {
1900     DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1901     }
1902   else if (!Ustrlen(tls_out.sni))
1903     tls_out.sni = NULL;
1904   else
1905     {
1906 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1907     DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1908     SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1909 #else
1910     DEBUG(D_tls)
1911       debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1912           tls_out.sni);
1913 #endif
1914     }
1915   }
1916
1917 #ifdef EXPERIMENTAL_DANE
1918 if (tlsa_dnsa)
1919   if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa)) != OK)
1920     return rc;
1921 #endif
1922
1923 #ifndef DISABLE_OCSP
1924 /* Request certificate status at connection-time.  If the server
1925 does OCSP stapling we will get the callback (set in tls_init()) */
1926 # ifdef EXPERIMENTAL_DANE
1927 if (request_ocsp)
1928   {
1929   const uschar * s;
1930   if (  ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
1931      || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
1932      )
1933     {   /* Re-eval now $tls_out_tlsa_usage is populated.  If
1934         this means we avoid the OCSP request, we wasted the setup
1935         cost in tls_init(). */
1936     require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
1937     request_ocsp = require_ocsp
1938       || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
1939     }
1940   }
1941 # endif
1942
1943 if (request_ocsp)
1944   {
1945   SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1946   client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1947   tls_out.ocsp = OCSP_NOT_RESP;
1948   }
1949 #endif
1950
1951 #ifdef EXPERIMENTAL_EVENT
1952 client_static_cbinfo->event_action = tb->event_action;
1953 #endif
1954
1955 /* There doesn't seem to be a built-in timeout on connection. */
1956
1957 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1958 sigalrm_seen = FALSE;
1959 alarm(ob->command_timeout);
1960 rc = SSL_connect(client_ssl);
1961 alarm(0);
1962
1963 #ifdef EXPERIMENTAL_DANE
1964 if (tlsa_dnsa)
1965   DANESSL_cleanup(client_ssl);
1966 #endif
1967
1968 if (rc <= 0)
1969   return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1970
1971 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1972
1973 /* Beware anonymous ciphers which lead to server_cert being NULL */
1974 /*XXX server_cert is never freed... use X509_free() */
1975 server_cert = SSL_get_peer_certificate (client_ssl);
1976 if (server_cert)
1977   {
1978   tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1979     CS txt, sizeof(txt));
1980   tls_out.peerdn = txt;         /*XXX a static buffer... */
1981   }
1982 else
1983   tls_out.peerdn = NULL;
1984
1985 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1986 tls_out.cipher = cipherbuf;
1987
1988 /* Record the certificate we presented */
1989   {
1990   X509 * crt = SSL_get_certificate(client_ssl);
1991   tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1992   }
1993
1994 tls_out.active = fd;
1995 return OK;
1996 }
1997
1998
1999
2000
2001
2002 /*************************************************
2003 *            TLS version of getc                 *
2004 *************************************************/
2005
2006 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2007 it refills the buffer via the SSL reading function.
2008
2009 Arguments:  none
2010 Returns:    the next character or EOF
2011
2012 Only used by the server-side TLS.
2013 */
2014
2015 int
2016 tls_getc(void)
2017 {
2018 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2019   {
2020   int error;
2021   int inbytes;
2022
2023   DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2024     ssl_xfer_buffer, ssl_xfer_buffer_size);
2025
2026   if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2027   inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
2028   error = SSL_get_error(server_ssl, inbytes);
2029   alarm(0);
2030
2031   /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2032   closed down, not that the socket itself has been closed down. Revert to
2033   non-SSL handling. */
2034
2035   if (error == SSL_ERROR_ZERO_RETURN)
2036     {
2037     DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2038
2039     receive_getc = smtp_getc;
2040     receive_ungetc = smtp_ungetc;
2041     receive_feof = smtp_feof;
2042     receive_ferror = smtp_ferror;
2043     receive_smtp_buffered = smtp_buffered;
2044
2045     SSL_free(server_ssl);
2046     server_ssl = NULL;
2047     tls_in.active = -1;
2048     tls_in.bits = 0;
2049     tls_in.cipher = NULL;
2050     tls_in.peerdn = NULL;
2051     tls_in.sni = NULL;
2052
2053     return smtp_getc();
2054     }
2055
2056   /* Handle genuine errors */
2057
2058   else if (error == SSL_ERROR_SSL)
2059     {
2060     ERR_error_string(ERR_get_error(), ssl_errstring);
2061     log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2062     ssl_xfer_error = 1;
2063     return EOF;
2064     }
2065
2066   else if (error != SSL_ERROR_NONE)
2067     {
2068     DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2069     ssl_xfer_error = 1;
2070     return EOF;
2071     }
2072
2073 #ifndef DISABLE_DKIM
2074   dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2075 #endif
2076   ssl_xfer_buffer_hwm = inbytes;
2077   ssl_xfer_buffer_lwm = 0;
2078   }
2079
2080 /* Something in the buffer; return next uschar */
2081
2082 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2083 }
2084
2085
2086
2087 /*************************************************
2088 *          Read bytes from TLS channel           *
2089 *************************************************/
2090
2091 /*
2092 Arguments:
2093   buff      buffer of data
2094   len       size of buffer
2095
2096 Returns:    the number of bytes read
2097             -1 after a failed read
2098
2099 Only used by the client-side TLS.
2100 */
2101
2102 int
2103 tls_read(BOOL is_server, uschar *buff, size_t len)
2104 {
2105 SSL *ssl = is_server ? server_ssl : client_ssl;
2106 int inbytes;
2107 int error;
2108
2109 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2110   buff, (unsigned int)len);
2111
2112 inbytes = SSL_read(ssl, CS buff, len);
2113 error = SSL_get_error(ssl, inbytes);
2114
2115 if (error == SSL_ERROR_ZERO_RETURN)
2116   {
2117   DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2118   return -1;
2119   }
2120 else if (error != SSL_ERROR_NONE)
2121   {
2122   return -1;
2123   }
2124
2125 return inbytes;
2126 }
2127
2128
2129
2130
2131
2132 /*************************************************
2133 *         Write bytes down TLS channel           *
2134 *************************************************/
2135
2136 /*
2137 Arguments:
2138   is_server channel specifier
2139   buff      buffer of data
2140   len       number of bytes
2141
2142 Returns:    the number of bytes after a successful write,
2143             -1 after a failed write
2144
2145 Used by both server-side and client-side TLS.
2146 */
2147
2148 int
2149 tls_write(BOOL is_server, const uschar *buff, size_t len)
2150 {
2151 int outbytes;
2152 int error;
2153 int left = len;
2154 SSL *ssl = is_server ? server_ssl : client_ssl;
2155
2156 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
2157 while (left > 0)
2158   {
2159   DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2160   outbytes = SSL_write(ssl, CS buff, left);
2161   error = SSL_get_error(ssl, outbytes);
2162   DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2163   switch (error)
2164     {
2165     case SSL_ERROR_SSL:
2166     ERR_error_string(ERR_get_error(), ssl_errstring);
2167     log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2168     return -1;
2169
2170     case SSL_ERROR_NONE:
2171     left -= outbytes;
2172     buff += outbytes;
2173     break;
2174
2175     case SSL_ERROR_ZERO_RETURN:
2176     log_write(0, LOG_MAIN, "SSL channel closed on write");
2177     return -1;
2178
2179     case SSL_ERROR_SYSCALL:
2180     log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2181       sender_fullhost ? sender_fullhost : US"<unknown>",
2182       strerror(errno));
2183
2184     default:
2185     log_write(0, LOG_MAIN, "SSL_write error %d", error);
2186     return -1;
2187     }
2188   }
2189 return len;
2190 }
2191
2192
2193
2194 /*************************************************
2195 *         Close down a TLS session               *
2196 *************************************************/
2197
2198 /* This is also called from within a delivery subprocess forked from the
2199 daemon, to shut down the TLS library, without actually doing a shutdown (which
2200 would tamper with the SSL session in the parent process).
2201
2202 Arguments:   TRUE if SSL_shutdown is to be called
2203 Returns:     nothing
2204
2205 Used by both server-side and client-side TLS.
2206 */
2207
2208 void
2209 tls_close(BOOL is_server, BOOL shutdown)
2210 {
2211 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2212 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2213
2214 if (*fdp < 0) return;  /* TLS was not active */
2215
2216 if (shutdown)
2217   {
2218   DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2219   SSL_shutdown(*sslp);
2220   }
2221
2222 SSL_free(*sslp);
2223 *sslp = NULL;
2224
2225 *fdp = -1;
2226 }
2227
2228
2229
2230
2231 /*************************************************
2232 *  Let tls_require_ciphers be checked at startup *
2233 *************************************************/
2234
2235 /* The tls_require_ciphers option, if set, must be something which the
2236 library can parse.
2237
2238 Returns:     NULL on success, or error message
2239 */
2240
2241 uschar *
2242 tls_validate_require_cipher(void)
2243 {
2244 SSL_CTX *ctx;
2245 uschar *s, *expciphers, *err;
2246
2247 /* this duplicates from tls_init(), we need a better "init just global
2248 state, for no specific purpose" singleton function of our own */
2249
2250 SSL_load_error_strings();
2251 OpenSSL_add_ssl_algorithms();
2252 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2253 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2254 list of available digests. */
2255 EVP_add_digest(EVP_sha256());
2256 #endif
2257
2258 if (!(tls_require_ciphers && *tls_require_ciphers))
2259   return NULL;
2260
2261 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
2262   return US"failed to expand tls_require_ciphers";
2263
2264 if (!(expciphers && *expciphers))
2265   return NULL;
2266
2267 /* normalisation ripped from above */
2268 s = expciphers;
2269 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2270
2271 err = NULL;
2272
2273 ctx = SSL_CTX_new(SSLv23_server_method());
2274 if (!ctx)
2275   {
2276   ERR_error_string(ERR_get_error(), ssl_errstring);
2277   return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2278   }
2279
2280 DEBUG(D_tls)
2281   debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2282
2283 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2284   {
2285   ERR_error_string(ERR_get_error(), ssl_errstring);
2286   err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2287   }
2288
2289 SSL_CTX_free(ctx);
2290
2291 return err;
2292 }
2293
2294
2295
2296
2297 /*************************************************
2298 *         Report the library versions.           *
2299 *************************************************/
2300
2301 /* There have historically been some issues with binary compatibility in
2302 OpenSSL libraries; if Exim (like many other applications) is built against
2303 one version of OpenSSL but the run-time linker picks up another version,
2304 it can result in serious failures, including crashing with a SIGSEGV.  So
2305 report the version found by the compiler and the run-time version.
2306
2307 Note: some OS vendors backport security fixes without changing the version
2308 number/string, and the version date remains unchanged.  The _build_ date
2309 will change, so we can more usefully assist with version diagnosis by also
2310 reporting the build date.
2311
2312 Arguments:   a FILE* to print the results to
2313 Returns:     nothing
2314 */
2315
2316 void
2317 tls_version_report(FILE *f)
2318 {
2319 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2320            "                          Runtime: %s\n"
2321            "                                 : %s\n",
2322            OPENSSL_VERSION_TEXT,
2323            SSLeay_version(SSLEAY_VERSION),
2324            SSLeay_version(SSLEAY_BUILT_ON));
2325 /* third line is 38 characters for the %s and the line is 73 chars long;
2326 the OpenSSL output includes a "built on: " prefix already. */
2327 }
2328
2329
2330
2331
2332 /*************************************************
2333 *            Random number generation            *
2334 *************************************************/
2335
2336 /* Pseudo-random number generation.  The result is not expected to be
2337 cryptographically strong but not so weak that someone will shoot themselves
2338 in the foot using it as a nonce in input in some email header scheme or
2339 whatever weirdness they'll twist this into.  The result should handle fork()
2340 and avoid repeating sequences.  OpenSSL handles that for us.
2341
2342 Arguments:
2343   max       range maximum
2344 Returns     a random number in range [0, max-1]
2345 */
2346
2347 int
2348 vaguely_random_number(int max)
2349 {
2350 unsigned int r;
2351 int i, needed_len;
2352 static pid_t pidlast = 0;
2353 pid_t pidnow;
2354 uschar *p;
2355 uschar smallbuf[sizeof(r)];
2356
2357 if (max <= 1)
2358   return 0;
2359
2360 pidnow = getpid();
2361 if (pidnow != pidlast)
2362   {
2363   /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2364   is unique for each thread", this doesn't apparently apply across processes,
2365   so our own warning from vaguely_random_number_fallback() applies here too.
2366   Fix per PostgreSQL. */
2367   if (pidlast != 0)
2368     RAND_cleanup();
2369   pidlast = pidnow;
2370   }
2371
2372 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2373 if (!RAND_status())
2374   {
2375   randstuff r;
2376   gettimeofday(&r.tv, NULL);
2377   r.p = getpid();
2378
2379   RAND_seed((uschar *)(&r), sizeof(r));
2380   }
2381 /* We're after pseudo-random, not random; if we still don't have enough data
2382 in the internal PRNG then our options are limited.  We could sleep and hope
2383 for entropy to come along (prayer technique) but if the system is so depleted
2384 in the first place then something is likely to just keep taking it.  Instead,
2385 we'll just take whatever little bit of pseudo-random we can still manage to
2386 get. */
2387
2388 needed_len = sizeof(r);
2389 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2390 asked for a number less than 10. */
2391 for (r = max, i = 0; r; ++i)
2392   r >>= 1;
2393 i = (i + 7) / 8;
2394 if (i < needed_len)
2395   needed_len = i;
2396
2397 /* We do not care if crypto-strong */
2398 i = RAND_pseudo_bytes(smallbuf, needed_len);
2399 if (i < 0)
2400   {
2401   DEBUG(D_all)
2402     debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2403   return vaguely_random_number_fallback(max);
2404   }
2405
2406 r = 0;
2407 for (p = smallbuf; needed_len; --needed_len, ++p)
2408   {
2409   r *= 256;
2410   r += *p;
2411   }
2412
2413 /* We don't particularly care about weighted results; if someone wants
2414 smooth distribution and cares enough then they should submit a patch then. */
2415 return r % max;
2416 }
2417
2418
2419
2420
2421 /*************************************************
2422 *        OpenSSL option parse                    *
2423 *************************************************/
2424
2425 /* Parse one option for tls_openssl_options_parse below
2426
2427 Arguments:
2428   name    one option name
2429   value   place to store a value for it
2430 Returns   success or failure in parsing
2431 */
2432
2433 struct exim_openssl_option {
2434   uschar *name;
2435   long    value;
2436 };
2437 /* We could use a macro to expand, but we need the ifdef and not all the
2438 options document which version they were introduced in.  Policylet: include
2439 all options unless explicitly for DTLS, let the administrator choose which
2440 to apply.
2441
2442 This list is current as of:
2443   ==>  1.0.1b  <==
2444 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2445 */
2446 static struct exim_openssl_option exim_openssl_options[] = {
2447 /* KEEP SORTED ALPHABETICALLY! */
2448 #ifdef SSL_OP_ALL
2449   { US"all", SSL_OP_ALL },
2450 #endif
2451 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2452   { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2453 #endif
2454 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2455   { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2456 #endif
2457 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2458   { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2459 #endif
2460 #ifdef SSL_OP_EPHEMERAL_RSA
2461   { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2462 #endif
2463 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2464   { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2465 #endif
2466 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2467   { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2468 #endif
2469 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2470   { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2471 #endif
2472 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2473   { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2474 #endif
2475 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2476   { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2477 #endif
2478 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2479   { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2480 #endif
2481 #ifdef SSL_OP_NO_COMPRESSION
2482   { US"no_compression", SSL_OP_NO_COMPRESSION },
2483 #endif
2484 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2485   { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2486 #endif
2487 #ifdef SSL_OP_NO_SSLv2
2488   { US"no_sslv2", SSL_OP_NO_SSLv2 },
2489 #endif
2490 #ifdef SSL_OP_NO_SSLv3
2491   { US"no_sslv3", SSL_OP_NO_SSLv3 },
2492 #endif
2493 #ifdef SSL_OP_NO_TICKET
2494   { US"no_ticket", SSL_OP_NO_TICKET },
2495 #endif
2496 #ifdef SSL_OP_NO_TLSv1
2497   { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2498 #endif
2499 #ifdef SSL_OP_NO_TLSv1_1
2500 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2501   /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2502 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2503 #else
2504   { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2505 #endif
2506 #endif
2507 #ifdef SSL_OP_NO_TLSv1_2
2508   { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2509 #endif
2510 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2511   { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2512 #endif
2513 #ifdef SSL_OP_SINGLE_DH_USE
2514   { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2515 #endif
2516 #ifdef SSL_OP_SINGLE_ECDH_USE
2517   { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2518 #endif
2519 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2520   { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2521 #endif
2522 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2523   { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2524 #endif
2525 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2526   { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2527 #endif
2528 #ifdef SSL_OP_TLS_D5_BUG
2529   { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2530 #endif
2531 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2532   { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2533 #endif
2534 };
2535 static int exim_openssl_options_size =
2536   sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2537
2538
2539 static BOOL
2540 tls_openssl_one_option_parse(uschar *name, long *value)
2541 {
2542 int first = 0;
2543 int last = exim_openssl_options_size;
2544 while (last > first)
2545   {
2546   int middle = (first + last)/2;
2547   int c = Ustrcmp(name, exim_openssl_options[middle].name);
2548   if (c == 0)
2549     {
2550     *value = exim_openssl_options[middle].value;
2551     return TRUE;
2552     }
2553   else if (c > 0)
2554     first = middle + 1;
2555   else
2556     last = middle;
2557   }
2558 return FALSE;
2559 }
2560
2561
2562
2563
2564 /*************************************************
2565 *        OpenSSL option parsing logic            *
2566 *************************************************/
2567
2568 /* OpenSSL has a number of compatibility options which an administrator might
2569 reasonably wish to set.  Interpret a list similarly to decode_bits(), so that
2570 we look like log_selector.
2571
2572 Arguments:
2573   option_spec  the administrator-supplied string of options
2574   results      ptr to long storage for the options bitmap
2575 Returns        success or failure
2576 */
2577
2578 BOOL
2579 tls_openssl_options_parse(uschar *option_spec, long *results)
2580 {
2581 long result, item;
2582 uschar *s, *end;
2583 uschar keep_c;
2584 BOOL adding, item_parsed;
2585
2586 result = 0L;
2587 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2588  * from default because it increases BEAST susceptibility. */
2589 #ifdef SSL_OP_NO_SSLv2
2590 result |= SSL_OP_NO_SSLv2;
2591 #endif
2592
2593 if (option_spec == NULL)
2594   {
2595   *results = result;
2596   return TRUE;
2597   }
2598
2599 for (s=option_spec; *s != '\0'; /**/)
2600   {
2601   while (isspace(*s)) ++s;
2602   if (*s == '\0')
2603     break;
2604   if (*s != '+' && *s != '-')
2605     {
2606     DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2607         "+ or - expected but found \"%s\"\n", s);
2608     return FALSE;
2609     }
2610   adding = *s++ == '+';
2611   for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2612   keep_c = *end;
2613   *end = '\0';
2614   item_parsed = tls_openssl_one_option_parse(s, &item);
2615   if (!item_parsed)
2616     {
2617     DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2618     return FALSE;
2619     }
2620   DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2621       adding ? "adding" : "removing", result, item, s);
2622   if (adding)
2623     result |= item;
2624   else
2625     result &= ~item;
2626   *end = keep_c;
2627   s = end;
2628   }
2629
2630 *results = result;
2631 return TRUE;
2632 }
2633
2634 /* vi: aw ai sw=2
2635 */
2636 /* End of tls-openssl.c */