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