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
  29 #ifndef DISABLE_OCSP
  30 # define EXIM_OCSP_SKEW_SECONDS (300L)
  31 # define EXIM_OCSP_MAX_AGE (-1L)
  32 #endif
  33
  34 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
  35 # define EXIM_HAVE_OPENSSL_TLSEXT
  36 #endif
  37
  38 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
  39 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
  40 # define DISABLE_OCSP
  41 #endif
  42
  43 /* Structure for collecting random data for seeding. */
  44
  45 typedef struct randstuff {
  46   struct timeval tv;
  47   pid_t          p;
  48 } randstuff;
  49
  50 /* Local static variables */
  51
  52 static BOOL client_verify_callback_called = FALSE;
  53 static BOOL server_verify_callback_called = FALSE;
  54 static const uschar *sid_ctx = US"exim";
  55
  56 /* We have three different contexts to care about.
  57
  58 Simple case: client, `client_ctx`
  59  As a client, we can be doing a callout or cut-through delivery while receiving
  60  a message.  So we have a client context, which should have options initialised
  61  from the SMTP Transport.
  62
  63 Server:
  64  There are two cases: with and without ServerNameIndication from the client.
  65  Given TLS SNI, we can be using different keys, certs and various other
  66  configuration settings, because they're re-expanded with $tls_sni set.  This
  67  allows vhosting with TLS.  This SNI is sent in the handshake.
  68  A client might not send SNI, so we need a fallback, and an initial setup too.
  69  So as a server, we start out using `server_ctx`.
  70  If SNI is sent by the client, then we as server, mid-negotiation, try to clone
  71  `server_sni` from `server_ctx` and then initialise settings by re-expanding
  72  configuration.
  73 */
  74
  75 static SSL_CTX *client_ctx = NULL;
  76 static SSL_CTX *server_ctx = NULL;
  77 static SSL     *client_ssl = NULL;
  78 static SSL     *server_ssl = NULL;
  79
  80 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
  81 static SSL_CTX *server_sni = NULL;
  82 #endif
  83
  84 static char ssl_errstring[256];
  85
  86 static int  ssl_session_timeout = 200;
  87 static BOOL client_verify_optional = FALSE;
  88 static BOOL server_verify_optional = FALSE;
  89
  90 static BOOL reexpand_tls_files_for_sni = FALSE;
  91
  92
  93 typedef struct tls_ext_ctx_cb {
  94   uschar *certificate;
  95   uschar *privatekey;
  96 #ifndef DISABLE_OCSP
  97   BOOL is_server;
  98   union {
  99     struct {
 100       uschar        *file;
 101       uschar        *file_expanded;
 102       OCSP_RESPONSE *response;
 103     } server;
 104     struct {
 105       X509_STORE    *verify_store;      /* non-null if status requested */
 106       BOOL          verify_required;
 107     } client;
 108   } u_ocsp;
 109 #endif
 110   uschar *dhparam;
 111   /* these are cached from first expand */
 112   uschar *server_cipher_list;
 113   /* only passed down to tls_error: */
 114   host_item *host;
 115
 116 #ifdef EXPERIMENTAL_CERTNAMES
 117   uschar * verify_cert_hostnames;
 118 #endif
 119 } tls_ext_ctx_cb;
 120
 121 /* should figure out a cleanup of API to handle state preserved per
 122 implementation, for various reasons, which can be void * in the APIs.
 123 For now, we hack around it. */
 124 tls_ext_ctx_cb *client_static_cbinfo = NULL;
 125 tls_ext_ctx_cb *server_static_cbinfo = NULL;
 126
 127 static int
 128 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
 129     int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
 130
 131 /* Callbacks */
 132 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 133 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
 134 #endif
 135 #ifndef DISABLE_OCSP
 136 static int tls_server_stapling_cb(SSL *s, void *arg);
 137 #endif
 138
 139
 140 /*************************************************
 141 *               Handle TLS error                 *
 142 *************************************************/
 143
 144 /* Called from lots of places when errors occur before actually starting to do
 145 the TLS handshake, that is, while the session is still in clear. Always returns
 146 DEFER for a server and FAIL for a client so that most calls can use "return
 147 tls_error(...)" to do this processing and then give an appropriate return. A
 148 single function is used for both server and client, because it is called from
 149 some shared functions.
 150
 151 Argument:
 152   prefix    text to include in the logged error
 153   host      NULL if setting up a server;
 154             the connected host if setting up a client
 155   msg       error message or NULL if we should ask OpenSSL
 156
 157 Returns:    OK/DEFER/FAIL
 158 */
 159
 160 static int
 161 tls_error(uschar *prefix, host_item *host, uschar *msg)
 162 {
 163 if (msg == NULL)
 164   {
 165   ERR_error_string(ERR_get_error(), ssl_errstring);
 166   msg = (uschar *)ssl_errstring;
 167   }
 168
 169 if (host == NULL)
 170   {
 171   uschar *conn_info = smtp_get_connection_info();
 172   if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
 173     conn_info += 5;
 174   log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
 175     conn_info, prefix, msg);
 176   return DEFER;
 177   }
 178 else
 179   {
 180   log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
 181     host->name, host->address, prefix, msg);
 182   return FAIL;
 183   }
 184 }
 185
 186
 187
 188 /*************************************************
 189 *        Callback to generate RSA key            *
 190 *************************************************/
 191
 192 /*
 193 Arguments:
 194   s          SSL connection
 195   export     not used
 196   keylength  keylength
 197
 198 Returns:     pointer to generated key
 199 */
 200
 201 static RSA *
 202 rsa_callback(SSL *s, int export, int keylength)
 203 {
 204 RSA *rsa_key;
 205 export = export;     /* Shut picky compilers up */
 206 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
 207 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
 208 if (rsa_key == NULL)
 209   {
 210   ERR_error_string(ERR_get_error(), ssl_errstring);
 211   log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
 212     ssl_errstring);
 213   return NULL;
 214   }
 215 return rsa_key;
 216 }
 217
 218
 219
 220 /* Extreme debug
 221 #ifndef DISABLE_OCSP
 222 void
 223 x509_store_dump_cert_s_names(X509_STORE * store)
 224 {
 225 STACK_OF(X509_OBJECT) * roots= store->objs;
 226 int i;
 227 static uschar name[256];
 228
 229 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
 230   {
 231   X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
 232   if(tmp_obj->type == X509_LU_X509)
 233     {
 234     X509 * current_cert= tmp_obj->data.x509;
 235     X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
 236     debug_printf(" %s\n", name);
 237     }
 238   }
 239 }
 240 #endif
 241 */
 242
 243
 244 /*************************************************
 245 *        Callback for verification               *
 246 *************************************************/
 247
 248 /* The SSL library does certificate verification if set up to do so. This
 249 callback has the current yes/no state is in "state". If verification succeeded,
 250 we set up the tls_peerdn string. If verification failed, what happens depends
 251 on whether the client is required to present a verifiable certificate or not.
 252
 253 If verification is optional, we change the state to yes, but still log the
 254 verification error. For some reason (it really would help to have proper
 255 documentation of OpenSSL), this callback function then gets called again, this
 256 time with state = 1. In fact, that's useful, because we can set up the peerdn
 257 value, but we must take care not to set the private verified flag on the second
 258 time through.
 259
 260 Note: this function is not called if the client fails to present a certificate
 261 when asked. We get here only if a certificate has been received. Handling of
 262 optional verification for this case is done when requesting SSL to verify, by
 263 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
 264
 265 Arguments:
 266   state      current yes/no state as 1/0
 267   x509ctx    certificate information.
 268   client     TRUE for client startup, FALSE for server startup
 269
 270 Returns:     1 if verified, 0 if not
 271 */
 272
 273 static int
 274 verify_callback(int state, X509_STORE_CTX *x509ctx,
 275   tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
 276 {
 277 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
 278 static uschar txt[256];
 279
 280 X509_NAME_oneline(X509_get_subject_name(cert), CS txt, sizeof(txt));
 281
 282 if (state == 0)
 283   {
 284   log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
 285     X509_STORE_CTX_get_error_depth(x509ctx),
 286     X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
 287     txt);
 288   tlsp->certificate_verified = FALSE;
 289   *calledp = TRUE;
 290   if (!*optionalp)
 291     {
 292     tlsp->peercert = X509_dup(cert);
 293     return 0;                       /* reject */
 294     }
 295   DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
 296     "tls_try_verify_hosts)\n");
 297   }
 298
 299 else if (X509_STORE_CTX_get_error_depth(x509ctx) != 0)
 300   {
 301   DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n",
 302      X509_STORE_CTX_get_error_depth(x509ctx), txt);
 303 #ifndef DISABLE_OCSP
 304   if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
 305     {   /* client, wanting stapling  */
 306     /* Add the server cert's signing chain as the one
 307     for the verification of the OCSP stapled information. */
 308
 309     if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
 310                              cert))
 311       ERR_clear_error();
 312     }
 313 #endif
 314   }
 315 else
 316   {
 317 #ifdef EXPERIMENTAL_CERTNAMES
 318   uschar * verify_cert_hostnames;
 319 #endif
 320
 321   tlsp->peerdn = txt;
 322   tlsp->peercert = X509_dup(cert);
 323
 324 #ifdef EXPERIMENTAL_CERTNAMES
 325   if (  tlsp == &tls_out
 326      && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
 327         /* client, wanting hostname check */
 328
 329 # if OPENSSL_VERSION_NUMBER >= 0x010100000L || OPENSSL_VERSION_NUMBER >= 0x010002000L
 330 #  ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
 331 #   define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
 332 #  endif
 333     {
 334     int sep = 0;
 335     uschar * list = verify_cert_hostnames;
 336     uschar * name;
 337     int rc;
 338     while ((name = string_nextinlist(&list, &sep, NULL, 0)))
 339       if ((rc = X509_check_host(cert, name, 0,
 340                   X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS)))
 341         {
 342         if (rc < 0)
 343           {
 344           log_write(0, LOG_MAIN, "SSL verify error: internal error\n");
 345           name = NULL;
 346           }
 347         break;
 348         }
 349     if (!name)
 350       {
 351       log_write(0, LOG_MAIN,
 352         "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
 353       return 0;                         /* reject */
 354       }
 355     }
 356 # else
 357     if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
 358       {
 359       log_write(0, LOG_MAIN,
 360         "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
 361       return 0;                         /* reject */
 362       }
 363 # endif
 364 #endif
 365
 366   DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
 367     *calledp ? "" : " authenticated", txt);
 368   if (!*calledp) tlsp->certificate_verified = TRUE;
 369   *calledp = TRUE;
 370   }
 371
 372 return 1;   /* accept */
 373 }
 374
 375 static int
 376 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
 377 {
 378 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
 379 }
 380
 381 static int
 382 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
 383 {
 384 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
 385 }
 386
 387
 388
 389 /*************************************************
 390 *           Information callback                 *
 391 *************************************************/
 392
 393 /* The SSL library functions call this from time to time to indicate what they
 394 are doing. We copy the string to the debugging output when TLS debugging has
 395 been requested.
 396
 397 Arguments:
 398   s         the SSL connection
 399   where
 400   ret
 401
 402 Returns:    nothing
 403 */
 404
 405 static void
 406 info_callback(SSL *s, int where, int ret)
 407 {
 408 where = where;
 409 ret = ret;
 410 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
 411 }
 412
 413
 414
 415 /*************************************************
 416 *                Initialize for DH               *
 417 *************************************************/
 418
 419 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
 420
 421 Arguments:
 422   dhparam   DH parameter file or fixed parameter identity string
 423   host      connected host, if client; NULL if server
 424
 425 Returns:    TRUE if OK (nothing to set up, or setup worked)
 426 */
 427
 428 static BOOL
 429 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
 430 {
 431 BIO *bio;
 432 DH *dh;
 433 uschar *dhexpanded;
 434 const char *pem;
 435
 436 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
 437   return FALSE;
 438
 439 if (!dhexpanded || !*dhexpanded)
 440   bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
 441 else if (dhexpanded[0] == '/')
 442   {
 443   if (!(bio = BIO_new_file(CS dhexpanded, "r")))
 444     {
 445     tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
 446           host, US strerror(errno));
 447     return FALSE;
 448     }
 449   }
 450 else
 451   {
 452   if (Ustrcmp(dhexpanded, "none") == 0)
 453     {
 454     DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
 455     return TRUE;
 456     }
 457
 458   if (!(pem = std_dh_prime_named(dhexpanded)))
 459     {
 460     tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
 461         host, US strerror(errno));
 462     return FALSE;
 463     }
 464   bio = BIO_new_mem_buf(CS pem, -1);
 465   }
 466
 467 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
 468   {
 469   BIO_free(bio);
 470   tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
 471       host, NULL);
 472   return FALSE;
 473   }
 474
 475 /* Even if it is larger, we silently return success rather than cause things
 476  * to fail out, so that a too-large DH will not knock out all TLS; it's a
 477  * debatable choice. */
 478 if ((8*DH_size(dh)) > tls_dh_max_bits)
 479   {
 480   DEBUG(D_tls)
 481     debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
 482         8*DH_size(dh), tls_dh_max_bits);
 483   }
 484 else
 485   {
 486   SSL_CTX_set_tmp_dh(sctx, dh);
 487   DEBUG(D_tls)
 488     debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
 489       dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
 490   }
 491
 492 DH_free(dh);
 493 BIO_free(bio);
 494
 495 return TRUE;
 496 }
 497
 498
 499
 500
 501 #ifndef DISABLE_OCSP
 502 /*************************************************
 503 *       Load OCSP information into state         *
 504 *************************************************/
 505
 506 /* Called to load the server OCSP response from the given file into memory, once
 507 caller has determined this is needed.  Checks validity.  Debugs a message
 508 if invalid.
 509
 510 ASSUMES: single response, for single cert.
 511
 512 Arguments:
 513   sctx            the SSL_CTX* to update
 514   cbinfo          various parts of session state
 515   expanded        the filename putatively holding an OCSP response
 516
 517 */
 518
 519 static void
 520 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
 521 {
 522 BIO *bio;
 523 OCSP_RESPONSE *resp;
 524 OCSP_BASICRESP *basic_response;
 525 OCSP_SINGLERESP *single_response;
 526 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
 527 X509_STORE *store;
 528 unsigned long verify_flags;
 529 int status, reason, i;
 530
 531 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
 532 if (cbinfo->u_ocsp.server.response)
 533   {
 534   OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
 535   cbinfo->u_ocsp.server.response = NULL;
 536   }
 537
 538 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
 539 if (!bio)
 540   {
 541   DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
 542       cbinfo->u_ocsp.server.file_expanded);
 543   return;
 544   }
 545
 546 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
 547 BIO_free(bio);
 548 if (!resp)
 549   {
 550   DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
 551   return;
 552   }
 553
 554 status = OCSP_response_status(resp);
 555 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
 556   {
 557   DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
 558       OCSP_response_status_str(status), status);
 559   goto bad;
 560   }
 561
 562 basic_response = OCSP_response_get1_basic(resp);
 563 if (!basic_response)
 564   {
 565   DEBUG(D_tls)
 566     debug_printf("OCSP response parse error: unable to extract basic response.\n");
 567   goto bad;
 568   }
 569
 570 store = SSL_CTX_get_cert_store(sctx);
 571 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
 572
 573 /* May need to expose ability to adjust those flags?
 574 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
 575 OCSP_TRUSTOTHER OCSP_NOINTERN */
 576
 577 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
 578 if (i <= 0)
 579   {
 580   DEBUG(D_tls) {
 581     ERR_error_string(ERR_get_error(), ssl_errstring);
 582     debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
 583     }
 584   goto bad;
 585   }
 586
 587 /* Here's the simplifying assumption: there's only one response, for the
 588 one certificate we use, and nothing for anything else in a chain.  If this
 589 proves false, we need to extract a cert id from our issued cert
 590 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
 591 right cert in the stack and then calls OCSP_single_get0_status()).
 592
 593 I'm hoping to avoid reworking a bunch more of how we handle state here. */
 594 single_response = OCSP_resp_get0(basic_response, 0);
 595 if (!single_response)
 596   {
 597   DEBUG(D_tls)
 598     debug_printf("Unable to get first response from OCSP basic response.\n");
 599   goto bad;
 600   }
 601
 602 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
 603 if (status != V_OCSP_CERTSTATUS_GOOD)
 604   {
 605   DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
 606       OCSP_cert_status_str(status), status,
 607       OCSP_crl_reason_str(reason), reason);
 608   goto bad;
 609   }
 610
 611 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
 612   {
 613   DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
 614   goto bad;
 615   }
 616
 617 supply_response:
 618   cbinfo->u_ocsp.server.response = resp;
 619 return;
 620
 621 bad:
 622   if (running_in_test_harness)
 623     {
 624     extern char ** environ;
 625     uschar ** p;
 626     if (environ) for (p = USS environ; *p != NULL; p++)
 627       if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
 628         {
 629         DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
 630         goto supply_response;
 631         }
 632     }
 633 return;
 634 }
 635 #endif  /*!DISABLE_OCSP*/
 636
 637
 638
 639
 640 /*************************************************
 641 *        Expand key and cert file specs          *
 642 *************************************************/
 643
 644 /* Called once during tls_init and possibly again during TLS setup, for a
 645 new context, if Server Name Indication was used and tls_sni was seen in
 646 the certificate string.
 647
 648 Arguments:
 649   sctx            the SSL_CTX* to update
 650   cbinfo          various parts of session state
 651
 652 Returns:          OK/DEFER/FAIL
 653 */
 654
 655 static int
 656 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
 657 {
 658 uschar *expanded;
 659
 660 if (cbinfo->certificate == NULL)
 661   return OK;
 662
 663 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
 664     Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
 665     Ustrstr(cbinfo->certificate, US"tls_out_sni")
 666    )
 667   reexpand_tls_files_for_sni = TRUE;
 668
 669 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
 670   return DEFER;
 671
 672 if (expanded != NULL)
 673   {
 674   DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
 675   if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
 676     return tls_error(string_sprintf(
 677       "SSL_CTX_use_certificate_chain_file file=%s", expanded),
 678         cbinfo->host, NULL);
 679   }
 680
 681 if (cbinfo->privatekey != NULL &&
 682     !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
 683   return DEFER;
 684
 685 /* If expansion was forced to fail, key_expanded will be NULL. If the result
 686 of the expansion is an empty string, ignore it also, and assume the private
 687 key is in the same file as the certificate. */
 688
 689 if (expanded != NULL && *expanded != 0)
 690   {
 691   DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
 692   if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
 693     return tls_error(string_sprintf(
 694       "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
 695   }
 696
 697 #ifndef DISABLE_OCSP
 698 if (cbinfo->is_server &&  cbinfo->u_ocsp.server.file != NULL)
 699   {
 700   if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
 701     return DEFER;
 702
 703   if (expanded != NULL && *expanded != 0)
 704     {
 705     DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
 706     if (cbinfo->u_ocsp.server.file_expanded &&
 707         (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
 708       {
 709       DEBUG(D_tls)
 710         debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
 711       } else {
 712         ocsp_load_response(sctx, cbinfo, expanded);
 713       }
 714     }
 715   }
 716 #endif
 717
 718 return OK;
 719 }
 720
 721
 722
 723
 724 /*************************************************
 725 *            Callback to handle SNI              *
 726 *************************************************/
 727
 728 /* Called when acting as server during the TLS session setup if a Server Name
 729 Indication extension was sent by the client.
 730
 731 API documentation is OpenSSL s_server.c implementation.
 732
 733 Arguments:
 734   s               SSL* of the current session
 735   ad              unknown (part of OpenSSL API) (unused)
 736   arg             Callback of "our" registered data
 737
 738 Returns:          SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
 739 */
 740
 741 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 742 static int
 743 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
 744 {
 745 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
 746 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
 747 int rc;
 748 int old_pool = store_pool;
 749
 750 if (!servername)
 751   return SSL_TLSEXT_ERR_OK;
 752
 753 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
 754     reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
 755
 756 /* Make the extension value available for expansion */
 757 store_pool = POOL_PERM;
 758 tls_in.sni = string_copy(US servername);
 759 store_pool = old_pool;
 760
 761 if (!reexpand_tls_files_for_sni)
 762   return SSL_TLSEXT_ERR_OK;
 763
 764 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
 765 not confident that memcpy wouldn't break some internal reference counting.
 766 Especially since there's a references struct member, which would be off. */
 767
 768 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
 769   {
 770   ERR_error_string(ERR_get_error(), ssl_errstring);
 771   DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
 772   return SSL_TLSEXT_ERR_NOACK;
 773   }
 774
 775 /* Not sure how many of these are actually needed, since SSL object
 776 already exists.  Might even need this selfsame callback, for reneg? */
 777
 778 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
 779 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
 780 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
 781 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
 782 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
 783 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
 784 if (cbinfo->server_cipher_list)
 785   SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
 786 #ifndef DISABLE_OCSP
 787 if (cbinfo->u_ocsp.server.file)
 788   {
 789   SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
 790   SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
 791   }
 792 #endif
 793
 794 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
 795 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
 796
 797 /* do this after setup_certs, because this can require the certs for verifying
 798 OCSP information. */
 799 rc = tls_expand_session_files(server_sni, cbinfo);
 800 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
 801
 802 if (!init_dh(server_sni, cbinfo->dhparam, NULL))
 803   return SSL_TLSEXT_ERR_NOACK;
 804
 805 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
 806 SSL_set_SSL_CTX(s, server_sni);
 807
 808 return SSL_TLSEXT_ERR_OK;
 809 }
 810 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
 811
 812
 813
 814
 815 #ifndef DISABLE_OCSP
 816
 817 /*************************************************
 818 *        Callback to handle OCSP Stapling        *
 819 *************************************************/
 820
 821 /* Called when acting as server during the TLS session setup if the client
 822 requests OCSP information with a Certificate Status Request.
 823
 824 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
 825 project.
 826
 827 */
 828
 829 static int
 830 tls_server_stapling_cb(SSL *s, void *arg)
 831 {
 832 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
 833 uschar *response_der;
 834 int response_der_len;
 835
 836 DEBUG(D_tls)
 837   debug_printf("Received TLS status request (OCSP stapling); %s response.",
 838     cbinfo->u_ocsp.server.response ? "have" : "lack");
 839
 840 tls_in.ocsp = OCSP_NOT_RESP;
 841 if (!cbinfo->u_ocsp.server.response)
 842   return SSL_TLSEXT_ERR_NOACK;
 843
 844 response_der = NULL;
 845 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
 846                       &response_der);
 847 if (response_der_len <= 0)
 848   return SSL_TLSEXT_ERR_NOACK;
 849
 850 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
 851 tls_in.ocsp = OCSP_VFIED;
 852 return SSL_TLSEXT_ERR_OK;
 853 }
 854
 855
 856 static void
 857 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
 858 {
 859 BIO_printf(bp, "\t%s: ", str);
 860 ASN1_GENERALIZEDTIME_print(bp, time);
 861 BIO_puts(bp, "\n");
 862 }
 863
 864 static int
 865 tls_client_stapling_cb(SSL *s, void *arg)
 866 {
 867 tls_ext_ctx_cb * cbinfo = arg;
 868 const unsigned char * p;
 869 int len;
 870 OCSP_RESPONSE * rsp;
 871 OCSP_BASICRESP * bs;
 872 int i;
 873
 874 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
 875 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
 876 if(!p)
 877  {
 878   /* Expect this when we requested ocsp but got none */
 879   if (  cbinfo->u_ocsp.client.verify_required
 880      && log_extra_selector & LX_tls_cipher)
 881     log_write(0, LOG_MAIN, "Received TLS status callback, null content");
 882   else
 883     DEBUG(D_tls) debug_printf(" null\n");
 884   return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 885  }
 886
 887 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
 888  {
 889   tls_out.ocsp = OCSP_FAILED;
 890   if (log_extra_selector & LX_tls_cipher)
 891     log_write(0, LOG_MAIN, "Received TLS status response, parse error");
 892   else
 893     DEBUG(D_tls) debug_printf(" parse error\n");
 894   return 0;
 895  }
 896
 897 if(!(bs = OCSP_response_get1_basic(rsp)))
 898   {
 899   tls_out.ocsp = OCSP_FAILED;
 900   if (log_extra_selector & LX_tls_cipher)
 901     log_write(0, LOG_MAIN, "Received TLS status response, error parsing response");
 902   else
 903     DEBUG(D_tls) debug_printf(" error parsing response\n");
 904   OCSP_RESPONSE_free(rsp);
 905   return 0;
 906   }
 907
 908 /* We'd check the nonce here if we'd put one in the request. */
 909 /* However that would defeat cacheability on the server so we don't. */
 910
 911 /* This section of code reworked from OpenSSL apps source;
 912    The OpenSSL Project retains copyright:
 913    Copyright (c) 1999 The OpenSSL Project.  All rights reserved.
 914 */
 915   {
 916     BIO * bp = NULL;
 917     int status, reason;
 918     ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
 919
 920     DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
 921
 922     /*OCSP_RESPONSE_print(bp, rsp, 0);   extreme debug: stapling content */
 923
 924     /* Use the chain that verified the server cert to verify the stapled info */
 925     /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
 926
 927     if ((i = OCSP_basic_verify(bs, NULL,
 928               cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
 929       {
 930       tls_out.ocsp = OCSP_FAILED;
 931       BIO_printf(bp, "OCSP response verify failure\n");
 932       ERR_print_errors(bp);
 933       i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 934       goto out;
 935       }
 936
 937     BIO_printf(bp, "OCSP response well-formed and signed OK\n");
 938
 939       {
 940       STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
 941       OCSP_SINGLERESP * single;
 942
 943       if (sk_OCSP_SINGLERESP_num(sresp) != 1)
 944         {
 945         tls_out.ocsp = OCSP_FAILED;
 946         log_write(0, LOG_MAIN, "OCSP stapling "
 947             "with multiple responses not handled");
 948         i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 949         goto out;
 950         }
 951       single = OCSP_resp_get0(bs, 0);
 952       status = OCSP_single_get0_status(single, &reason, &rev,
 953                   &thisupd, &nextupd);
 954       }
 955
 956     DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
 957     DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
 958     if (!OCSP_check_validity(thisupd, nextupd,
 959           EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
 960       {
 961       tls_out.ocsp = OCSP_FAILED;
 962       DEBUG(D_tls) ERR_print_errors(bp);
 963       log_write(0, LOG_MAIN, "Server OSCP dates invalid");
 964       i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 965       }
 966     else
 967       {
 968       DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
 969                     OCSP_cert_status_str(status));
 970       switch(status)
 971         {
 972         case V_OCSP_CERTSTATUS_GOOD:
 973           tls_out.ocsp = OCSP_VFIED;
 974           i = 1;
 975           break;
 976         case V_OCSP_CERTSTATUS_REVOKED:
 977           tls_out.ocsp = OCSP_FAILED;
 978           log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
 979               reason != -1 ? "; reason: " : "",
 980               reason != -1 ? OCSP_crl_reason_str(reason) : "");
 981           DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
 982           i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 983           break;
 984         default:
 985           tls_out.ocsp = OCSP_FAILED;
 986           log_write(0, LOG_MAIN,
 987               "Server certificate status unknown, in OCSP stapling");
 988           i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
 989           break;
 990         }
 991       }
 992   out:
 993     BIO_free(bp);
 994   }
 995
 996 OCSP_RESPONSE_free(rsp);
 997 return i;
 998 }
 999 #endif  /*!DISABLE_OCSP*/
1000
1001
1002
1003 /*************************************************
1004 *            Initialize for TLS                  *
1005 *************************************************/
1006
1007 /* Called from both server and client code, to do preliminary initialization
1008 of the library.  We allocate and return a context structure.
1009
1010 Arguments:
1011   host            connected host, if client; NULL if server
1012   dhparam         DH parameter file
1013   certificate     certificate file
1014   privatekey      private key
1015   ocsp_file       file of stapling info (server); flag for require ocsp (client)
1016   addr            address if client; NULL if server (for some randomness)
1017   cbp             place to put allocated context
1018
1019 Returns:          OK/DEFER/FAIL
1020 */
1021
1022 static int
1023 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1024   uschar *privatekey,
1025 #ifndef DISABLE_OCSP
1026   uschar *ocsp_file,
1027 #endif
1028   address_item *addr, tls_ext_ctx_cb ** cbp)
1029 {
1030 long init_options;
1031 int rc;
1032 BOOL okay;
1033 tls_ext_ctx_cb *cbinfo;
1034
1035 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1036 cbinfo->certificate = certificate;
1037 cbinfo->privatekey = privatekey;
1038 #ifndef DISABLE_OCSP
1039 if ((cbinfo->is_server = host==NULL))
1040   {
1041   cbinfo->u_ocsp.server.file = ocsp_file;
1042   cbinfo->u_ocsp.server.file_expanded = NULL;
1043   cbinfo->u_ocsp.server.response = NULL;
1044   }
1045 else
1046   cbinfo->u_ocsp.client.verify_store = NULL;
1047 #endif
1048 cbinfo->dhparam = dhparam;
1049 cbinfo->server_cipher_list = NULL;
1050 cbinfo->host = host;
1051
1052 SSL_load_error_strings();          /* basic set up */
1053 OpenSSL_add_ssl_algorithms();
1054
1055 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1056 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1057 list of available digests. */
1058 EVP_add_digest(EVP_sha256());
1059 #endif
1060
1061 /* Create a context.
1062 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1063 negotiation in the different methods; as far as I can tell, the only
1064 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1065 when OpenSSL is built without SSLv2 support.
1066 By disabling with openssl_options, we can let admins re-enable with the
1067 existing knob. */
1068
1069 *ctxp = SSL_CTX_new((host == NULL)?
1070   SSLv23_server_method() : SSLv23_client_method());
1071
1072 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1073
1074 /* It turns out that we need to seed the random number generator this early in
1075 order to get the full complement of ciphers to work. It took me roughly a day
1076 of work to discover this by experiment.
1077
1078 On systems that have /dev/urandom, SSL may automatically seed itself from
1079 there. Otherwise, we have to make something up as best we can. Double check
1080 afterwards. */
1081
1082 if (!RAND_status())
1083   {
1084   randstuff r;
1085   gettimeofday(&r.tv, NULL);
1086   r.p = getpid();
1087
1088   RAND_seed((uschar *)(&r), sizeof(r));
1089   RAND_seed((uschar *)big_buffer, big_buffer_size);
1090   if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1091
1092   if (!RAND_status())
1093     return tls_error(US"RAND_status", host,
1094       US"unable to seed random number generator");
1095   }
1096
1097 /* Set up the information callback, which outputs if debugging is at a suitable
1098 level. */
1099
1100 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1101
1102 /* Automatically re-try reads/writes after renegotiation. */
1103 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1104
1105 /* Apply administrator-supplied work-arounds.
1106 Historically we applied just one requested option,
1107 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1108 moved to an administrator-controlled list of options to specify and
1109 grandfathered in the first one as the default value for "openssl_options".
1110
1111 No OpenSSL version number checks: the options we accept depend upon the
1112 availability of the option value macros from OpenSSL.  */
1113
1114 okay = tls_openssl_options_parse(openssl_options, &init_options);
1115 if (!okay)
1116   return tls_error(US"openssl_options parsing failed", host, NULL);
1117
1118 if (init_options)
1119   {
1120   DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1121   if (!(SSL_CTX_set_options(*ctxp, init_options)))
1122     return tls_error(string_sprintf(
1123           "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1124   }
1125 else
1126   DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1127
1128 /* Initialize with DH parameters if supplied */
1129
1130 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1131
1132 /* Set up certificate and key (and perhaps OCSP info) */
1133
1134 rc = tls_expand_session_files(*ctxp, cbinfo);
1135 if (rc != OK) return rc;
1136
1137 /* If we need to handle SNI, do so */
1138 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1139 if (host == NULL)               /* server */
1140   {
1141 # ifndef DISABLE_OCSP
1142   /* We check u_ocsp.server.file, not server.response, because we care about if
1143   the option exists, not what the current expansion might be, as SNI might
1144   change the certificate and OCSP file in use between now and the time the
1145   callback is invoked. */
1146   if (cbinfo->u_ocsp.server.file)
1147     {
1148     SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1149     SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1150     }
1151 # endif
1152   /* We always do this, so that $tls_sni is available even if not used in
1153   tls_certificate */
1154   SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1155   SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1156   }
1157 # ifndef DISABLE_OCSP
1158 else                    /* client */
1159   if(ocsp_file)         /* wanting stapling */
1160     {
1161     if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1162       {
1163       DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1164       return FAIL;
1165       }
1166     SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1167     SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1168     }
1169 # endif
1170 #endif
1171
1172 #ifdef EXPERIMENTAL_CERTNAMES
1173 cbinfo->verify_cert_hostnames = NULL;
1174 #endif
1175
1176 /* Set up the RSA callback */
1177
1178 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1179
1180 /* Finally, set the timeout, and we are done */
1181
1182 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1183 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1184
1185 *cbp = cbinfo;
1186
1187 return OK;
1188 }
1189
1190
1191
1192
1193 /*************************************************
1194 *           Get name of cipher in use            *
1195 *************************************************/
1196
1197 /*
1198 Argument:   pointer to an SSL structure for the connection
1199             buffer to use for answer
1200             size of buffer
1201             pointer to number of bits for cipher
1202 Returns:    nothing
1203 */
1204
1205 static void
1206 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1207 {
1208 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1209 yet reflect that.  It should be a safe change anyway, even 0.9.8 versions have
1210 the accessor functions use const in the prototype. */
1211 const SSL_CIPHER *c;
1212 const uschar *ver;
1213
1214 ver = (const uschar *)SSL_get_version(ssl);
1215
1216 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1217 SSL_CIPHER_get_bits(c, bits);
1218
1219 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1220   SSL_CIPHER_get_name(c), *bits);
1221
1222 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1223 }
1224
1225
1226
1227
1228
1229 /*************************************************
1230 *        Set up for verifying certificates       *
1231 *************************************************/
1232
1233 /* Called by both client and server startup
1234
1235 Arguments:
1236   sctx          SSL_CTX* to initialise
1237   certs         certs file or NULL
1238   crl           CRL file or NULL
1239   host          NULL in a server; the remote host in a client
1240   optional      TRUE if called from a server for a host in tls_try_verify_hosts;
1241                 otherwise passed as FALSE
1242   cert_vfy_cb   Callback function for certificate verification
1243
1244 Returns:        OK/DEFER/FAIL
1245 */
1246
1247 static int
1248 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1249     int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1250 {
1251 uschar *expcerts, *expcrl;
1252
1253 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1254   return DEFER;
1255
1256 if (expcerts != NULL && *expcerts != '\0')
1257   {
1258   struct stat statbuf;
1259   if (!SSL_CTX_set_default_verify_paths(sctx))
1260     return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1261
1262   if (Ustat(expcerts, &statbuf) < 0)
1263     {
1264     log_write(0, LOG_MAIN|LOG_PANIC,
1265       "failed to stat %s for certificates", expcerts);
1266     return DEFER;
1267     }
1268   else
1269     {
1270     uschar *file, *dir;
1271     if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1272       { file = NULL; dir = expcerts; }
1273     else
1274       { file = expcerts; dir = NULL; }
1275
1276     /* If a certificate file is empty, the next function fails with an
1277     unhelpful error message. If we skip it, we get the correct behaviour (no
1278     certificates are recognized, but the error message is still misleading (it
1279     says no certificate was supplied.) But this is better. */
1280
1281     if ((file == NULL || statbuf.st_size > 0) &&
1282           !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1283       return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1284
1285     if (file != NULL)
1286       {
1287       SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1288       }
1289     }
1290
1291   /* Handle a certificate revocation list. */
1292
1293   #if OPENSSL_VERSION_NUMBER > 0x00907000L
1294
1295   /* This bit of code is now the version supplied by Lars Mainka. (I have
1296    * merely reformatted it into the Exim code style.)
1297
1298    * "From here I changed the code to add support for multiple crl's
1299    * in pem format in one file or to support hashed directory entries in
1300    * pem format instead of a file. This method now uses the library function
1301    * X509_STORE_load_locations to add the CRL location to the SSL context.
1302    * OpenSSL will then handle the verify against CA certs and CRLs by
1303    * itself in the verify callback." */
1304
1305   if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1306   if (expcrl != NULL && *expcrl != 0)
1307     {
1308     struct stat statbufcrl;
1309     if (Ustat(expcrl, &statbufcrl) < 0)
1310       {
1311       log_write(0, LOG_MAIN|LOG_PANIC,
1312         "failed to stat %s for certificates revocation lists", expcrl);
1313       return DEFER;
1314       }
1315     else
1316       {
1317       /* is it a file or directory? */
1318       uschar *file, *dir;
1319       X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1320       if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1321         {
1322         file = NULL;
1323         dir = expcrl;
1324         DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1325         }
1326       else
1327         {
1328         file = expcrl;
1329         dir = NULL;
1330         DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1331         }
1332       if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1333         return tls_error(US"X509_STORE_load_locations", host, NULL);
1334
1335       /* setting the flags to check against the complete crl chain */
1336
1337       X509_STORE_set_flags(cvstore,
1338         X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1339       }
1340     }
1341
1342   #endif  /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1343
1344   /* If verification is optional, don't fail if no certificate */
1345
1346   SSL_CTX_set_verify(sctx,
1347     SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1348     cert_vfy_cb);
1349   }
1350
1351 return OK;
1352 }
1353
1354
1355
1356 /*************************************************
1357 *       Start a TLS session in a server          *
1358 *************************************************/
1359
1360 /* This is called when Exim is running as a server, after having received
1361 the STARTTLS command. It must respond to that command, and then negotiate
1362 a TLS session.
1363
1364 Arguments:
1365   require_ciphers   allowed ciphers
1366
1367 Returns:            OK on success
1368                     DEFER for errors before the start of the negotiation
1369                     FAIL for errors during the negotation; the server can't
1370                       continue running.
1371 */
1372
1373 int
1374 tls_server_start(const uschar *require_ciphers)
1375 {
1376 int rc;
1377 uschar *expciphers;
1378 tls_ext_ctx_cb *cbinfo;
1379 static uschar cipherbuf[256];
1380
1381 /* Check for previous activation */
1382
1383 if (tls_in.active >= 0)
1384   {
1385   tls_error(US"STARTTLS received after TLS started", NULL, US"");
1386   smtp_printf("554 Already in TLS\r\n");
1387   return FAIL;
1388   }
1389
1390 /* Initialize the SSL library. If it fails, it will already have logged
1391 the error. */
1392
1393 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1394 #ifndef DISABLE_OCSP
1395     tls_ocsp_file,
1396 #endif
1397     NULL, &server_static_cbinfo);
1398 if (rc != OK) return rc;
1399 cbinfo = server_static_cbinfo;
1400
1401 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1402   return FAIL;
1403
1404 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1405 were historically separated by underscores. So that I can use either form in my
1406 tests, and also for general convenience, we turn underscores into hyphens here.
1407 */
1408
1409 if (expciphers != NULL)
1410   {
1411   uschar *s = expciphers;
1412   while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1413   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1414   if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1415     return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1416   cbinfo->server_cipher_list = expciphers;
1417   }
1418
1419 /* If this is a host for which certificate verification is mandatory or
1420 optional, set up appropriately. */
1421
1422 tls_in.certificate_verified = FALSE;
1423 server_verify_callback_called = FALSE;
1424
1425 if (verify_check_host(&tls_verify_hosts) == OK)
1426   {
1427   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1428                         FALSE, verify_callback_server);
1429   if (rc != OK) return rc;
1430   server_verify_optional = FALSE;
1431   }
1432 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1433   {
1434   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1435                         TRUE, verify_callback_server);
1436   if (rc != OK) return rc;
1437   server_verify_optional = TRUE;
1438   }
1439
1440 /* Prepare for new connection */
1441
1442 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1443
1444 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1445  *
1446  * With the SSL_clear(), we get strange interoperability bugs with
1447  * OpenSSL 1.0.1b and TLS1.1/1.2.  It looks as though this may be a bug in
1448  * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1449  *
1450  * The SSL_clear() call is to let an existing SSL* be reused, typically after
1451  * session shutdown.  In this case, we have a brand new object and there's no
1452  * obvious reason to immediately clear it.  I'm guessing that this was
1453  * originally added because of incomplete initialisation which the clear fixed,
1454  * in some historic release.
1455  */
1456
1457 /* Set context and tell client to go ahead, except in the case of TLS startup
1458 on connection, where outputting anything now upsets the clients and tends to
1459 make them disconnect. We need to have an explicit fflush() here, to force out
1460 the response. Other smtp_printf() calls do not need it, because in non-TLS
1461 mode, the fflush() happens when smtp_getc() is called. */
1462
1463 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1464 if (!tls_in.on_connect)
1465   {
1466   smtp_printf("220 TLS go ahead\r\n");
1467   fflush(smtp_out);
1468   }
1469
1470 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1471 that the OpenSSL library doesn't. */
1472
1473 SSL_set_wfd(server_ssl, fileno(smtp_out));
1474 SSL_set_rfd(server_ssl, fileno(smtp_in));
1475 SSL_set_accept_state(server_ssl);
1476
1477 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1478
1479 sigalrm_seen = FALSE;
1480 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1481 rc = SSL_accept(server_ssl);
1482 alarm(0);
1483
1484 if (rc <= 0)
1485   {
1486   tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1487   if (ERR_get_error() == 0)
1488     log_write(0, LOG_MAIN,
1489         "TLS client disconnected cleanly (rejected our certificate?)");
1490   return FAIL;
1491   }
1492
1493 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1494
1495 /* TLS has been set up. Adjust the input functions to read via TLS,
1496 and initialize things. */
1497
1498 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1499 tls_in.cipher = cipherbuf;
1500
1501 DEBUG(D_tls)
1502   {
1503   uschar buf[2048];
1504   if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1505     debug_printf("Shared ciphers: %s\n", buf);
1506   }
1507
1508 /* Record the certificate we presented */
1509   {
1510   X509 * crt = SSL_get_certificate(server_ssl);
1511   tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1512   }
1513
1514 /* Only used by the server-side tls (tls_in), including tls_getc.
1515    Client-side (tls_out) reads (seem to?) go via
1516    smtp_read_response()/ip_recv().
1517    Hence no need to duplicate for _in and _out.
1518  */
1519 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1520 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1521 ssl_xfer_eof = ssl_xfer_error = 0;
1522
1523 receive_getc = tls_getc;
1524 receive_ungetc = tls_ungetc;
1525 receive_feof = tls_feof;
1526 receive_ferror = tls_ferror;
1527 receive_smtp_buffered = tls_smtp_buffered;
1528
1529 tls_in.active = fileno(smtp_out);
1530 return OK;
1531 }
1532
1533
1534
1535
1536
1537 /*************************************************
1538 *    Start a TLS session in a client             *
1539 *************************************************/
1540
1541 /* Called from the smtp transport after STARTTLS has been accepted.
1542
1543 Argument:
1544   fd               the fd of the connection
1545   host             connected host (for messages)
1546   addr             the first address
1547   ob               smtp transport options
1548
1549 Returns:           OK on success
1550                    FAIL otherwise - note that tls_error() will not give DEFER
1551                      because this is not a server
1552 */
1553
1554 int
1555 tls_client_start(int fd, host_item *host, address_item *addr,
1556   void *v_ob)
1557 {
1558 smtp_transport_options_block * ob = v_ob;
1559 static uschar txt[256];
1560 uschar *expciphers;
1561 X509* server_cert;
1562 int rc;
1563 static uschar cipherbuf[256];
1564 #ifndef DISABLE_OCSP
1565 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1566   NULL, host->name, host->address, NULL) == OK;
1567 BOOL request_ocsp = require_ocsp ? TRUE
1568   : verify_check_this_host(&ob->hosts_request_ocsp,
1569       NULL, host->name, host->address, NULL) == OK;
1570 #endif
1571
1572 rc = tls_init(&client_ctx, host, NULL,
1573     ob->tls_certificate, ob->tls_privatekey,
1574 #ifndef DISABLE_OCSP
1575     (void *)(long)request_ocsp,
1576 #endif
1577     addr, &client_static_cbinfo);
1578 if (rc != OK) return rc;
1579
1580 tls_out.certificate_verified = FALSE;
1581 client_verify_callback_called = FALSE;
1582
1583 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1584     &expciphers))
1585   return FAIL;
1586
1587 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1588 are separated by underscores. So that I can use either form in my tests, and
1589 also for general convenience, we turn underscores into hyphens here. */
1590
1591 if (expciphers != NULL)
1592   {
1593   uschar *s = expciphers;
1594   while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1595   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1596   if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1597     return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1598   }
1599
1600 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1601    set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1602    the specified host patterns if one of them is defined */
1603
1604 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1605     (verify_check_host(&ob->tls_verify_hosts) == OK))
1606   {
1607   if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1608         ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1609     return rc;
1610   client_verify_optional = FALSE;
1611
1612 #ifdef EXPERIMENTAL_CERTNAMES
1613   if (ob->tls_verify_cert_hostnames)
1614     {
1615     if (!expand_check(ob->tls_verify_cert_hostnames,
1616                       US"tls_verify_cert_hostnames",
1617                       &client_static_cbinfo->verify_cert_hostnames))
1618       return FAIL;
1619     if (client_static_cbinfo->verify_cert_hostnames)
1620       DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1621                       client_static_cbinfo->verify_cert_hostnames);
1622     }
1623 #endif
1624   }
1625 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1626   {
1627   if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1628         ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1629     return rc;
1630   client_verify_optional = TRUE;
1631   }
1632
1633 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1634   return tls_error(US"SSL_new", host, NULL);
1635 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1636 SSL_set_fd(client_ssl, fd);
1637 SSL_set_connect_state(client_ssl);
1638
1639 if (ob->tls_sni)
1640   {
1641   if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1642     return FAIL;
1643   if (tls_out.sni == NULL)
1644     {
1645     DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1646     }
1647   else if (!Ustrlen(tls_out.sni))
1648     tls_out.sni = NULL;
1649   else
1650     {
1651 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1652     DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1653     SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1654 #else
1655     DEBUG(D_tls)
1656       debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1657           tls_out.sni);
1658 #endif
1659     }
1660   }
1661
1662 #ifndef DISABLE_OCSP
1663 /* Request certificate status at connection-time.  If the server
1664 does OCSP stapling we will get the callback (set in tls_init()) */
1665 if (request_ocsp)
1666   {
1667   SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1668   client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1669   tls_out.ocsp = OCSP_NOT_RESP;
1670   }
1671 #endif
1672
1673 /* There doesn't seem to be a built-in timeout on connection. */
1674
1675 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1676 sigalrm_seen = FALSE;
1677 alarm(ob->command_timeout);
1678 rc = SSL_connect(client_ssl);
1679 alarm(0);
1680
1681 if (rc <= 0)
1682   return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1683
1684 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1685
1686 /* Beware anonymous ciphers which lead to server_cert being NULL */
1687 /*XXX server_cert is never freed... use X509_free() */
1688 server_cert = SSL_get_peer_certificate (client_ssl);
1689 if (server_cert)
1690   {
1691   tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1692     CS txt, sizeof(txt));
1693   tls_out.peerdn = txt;         /*XXX a static buffer... */
1694   }
1695 else
1696   tls_out.peerdn = NULL;
1697
1698 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1699 tls_out.cipher = cipherbuf;
1700
1701 /* Record the certificate we presented */
1702   {
1703   X509 * crt = SSL_get_certificate(client_ssl);
1704   tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1705   }
1706
1707 tls_out.active = fd;
1708 return OK;
1709 }
1710
1711
1712
1713
1714
1715 /*************************************************
1716 *            TLS version of getc                 *
1717 *************************************************/
1718
1719 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1720 it refills the buffer via the SSL reading function.
1721
1722 Arguments:  none
1723 Returns:    the next character or EOF
1724
1725 Only used by the server-side TLS.
1726 */
1727
1728 int
1729 tls_getc(void)
1730 {
1731 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1732   {
1733   int error;
1734   int inbytes;
1735
1736   DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1737     ssl_xfer_buffer, ssl_xfer_buffer_size);
1738
1739   if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1740   inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1741   error = SSL_get_error(server_ssl, inbytes);
1742   alarm(0);
1743
1744   /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1745   closed down, not that the socket itself has been closed down. Revert to
1746   non-SSL handling. */
1747
1748   if (error == SSL_ERROR_ZERO_RETURN)
1749     {
1750     DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1751
1752     receive_getc = smtp_getc;
1753     receive_ungetc = smtp_ungetc;
1754     receive_feof = smtp_feof;
1755     receive_ferror = smtp_ferror;
1756     receive_smtp_buffered = smtp_buffered;
1757
1758     SSL_free(server_ssl);
1759     server_ssl = NULL;
1760     tls_in.active = -1;
1761     tls_in.bits = 0;
1762     tls_in.cipher = NULL;
1763     tls_in.peerdn = NULL;
1764     tls_in.sni = NULL;
1765
1766     return smtp_getc();
1767     }
1768
1769   /* Handle genuine errors */
1770
1771   else if (error == SSL_ERROR_SSL)
1772     {
1773     ERR_error_string(ERR_get_error(), ssl_errstring);
1774     log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1775     ssl_xfer_error = 1;
1776     return EOF;
1777     }
1778
1779   else if (error != SSL_ERROR_NONE)
1780     {
1781     DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1782     ssl_xfer_error = 1;
1783     return EOF;
1784     }
1785
1786 #ifndef DISABLE_DKIM
1787   dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1788 #endif
1789   ssl_xfer_buffer_hwm = inbytes;
1790   ssl_xfer_buffer_lwm = 0;
1791   }
1792
1793 /* Something in the buffer; return next uschar */
1794
1795 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1796 }
1797
1798
1799
1800 /*************************************************
1801 *          Read bytes from TLS channel           *
1802 *************************************************/
1803
1804 /*
1805 Arguments:
1806   buff      buffer of data
1807   len       size of buffer
1808
1809 Returns:    the number of bytes read
1810             -1 after a failed read
1811
1812 Only used by the client-side TLS.
1813 */
1814
1815 int
1816 tls_read(BOOL is_server, uschar *buff, size_t len)
1817 {
1818 SSL *ssl = is_server ? server_ssl : client_ssl;
1819 int inbytes;
1820 int error;
1821
1822 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1823   buff, (unsigned int)len);
1824
1825 inbytes = SSL_read(ssl, CS buff, len);
1826 error = SSL_get_error(ssl, inbytes);
1827
1828 if (error == SSL_ERROR_ZERO_RETURN)
1829   {
1830   DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1831   return -1;
1832   }
1833 else if (error != SSL_ERROR_NONE)
1834   {
1835   return -1;
1836   }
1837
1838 return inbytes;
1839 }
1840
1841
1842
1843
1844
1845 /*************************************************
1846 *         Write bytes down TLS channel           *
1847 *************************************************/
1848
1849 /*
1850 Arguments:
1851   is_server channel specifier
1852   buff      buffer of data
1853   len       number of bytes
1854
1855 Returns:    the number of bytes after a successful write,
1856             -1 after a failed write
1857
1858 Used by both server-side and client-side TLS.
1859 */
1860
1861 int
1862 tls_write(BOOL is_server, const uschar *buff, size_t len)
1863 {
1864 int outbytes;
1865 int error;
1866 int left = len;
1867 SSL *ssl = is_server ? server_ssl : client_ssl;
1868
1869 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1870 while (left > 0)
1871   {
1872   DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1873   outbytes = SSL_write(ssl, CS buff, left);
1874   error = SSL_get_error(ssl, outbytes);
1875   DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1876   switch (error)
1877     {
1878     case SSL_ERROR_SSL:
1879     ERR_error_string(ERR_get_error(), ssl_errstring);
1880     log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1881     return -1;
1882
1883     case SSL_ERROR_NONE:
1884     left -= outbytes;
1885     buff += outbytes;
1886     break;
1887
1888     case SSL_ERROR_ZERO_RETURN:
1889     log_write(0, LOG_MAIN, "SSL channel closed on write");
1890     return -1;
1891
1892     case SSL_ERROR_SYSCALL:
1893     log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1894       sender_fullhost ? sender_fullhost : US"<unknown>",
1895       strerror(errno));
1896
1897     default:
1898     log_write(0, LOG_MAIN, "SSL_write error %d", error);
1899     return -1;
1900     }
1901   }
1902 return len;
1903 }
1904
1905
1906
1907 /*************************************************
1908 *         Close down a TLS session               *
1909 *************************************************/
1910
1911 /* This is also called from within a delivery subprocess forked from the
1912 daemon, to shut down the TLS library, without actually doing a shutdown (which
1913 would tamper with the SSL session in the parent process).
1914
1915 Arguments:   TRUE if SSL_shutdown is to be called
1916 Returns:     nothing
1917
1918 Used by both server-side and client-side TLS.
1919 */
1920
1921 void
1922 tls_close(BOOL is_server, BOOL shutdown)
1923 {
1924 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1925 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1926
1927 if (*fdp < 0) return;  /* TLS was not active */
1928
1929 if (shutdown)
1930   {
1931   DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1932   SSL_shutdown(*sslp);
1933   }
1934
1935 SSL_free(*sslp);
1936 *sslp = NULL;
1937
1938 *fdp = -1;
1939 }
1940
1941
1942
1943
1944 /*************************************************
1945 *  Let tls_require_ciphers be checked at startup *
1946 *************************************************/
1947
1948 /* The tls_require_ciphers option, if set, must be something which the
1949 library can parse.
1950
1951 Returns:     NULL on success, or error message
1952 */
1953
1954 uschar *
1955 tls_validate_require_cipher(void)
1956 {
1957 SSL_CTX *ctx;
1958 uschar *s, *expciphers, *err;
1959
1960 /* this duplicates from tls_init(), we need a better "init just global
1961 state, for no specific purpose" singleton function of our own */
1962
1963 SSL_load_error_strings();
1964 OpenSSL_add_ssl_algorithms();
1965 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1966 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1967 list of available digests. */
1968 EVP_add_digest(EVP_sha256());
1969 #endif
1970
1971 if (!(tls_require_ciphers && *tls_require_ciphers))
1972   return NULL;
1973
1974 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1975   return US"failed to expand tls_require_ciphers";
1976
1977 if (!(expciphers && *expciphers))
1978   return NULL;
1979
1980 /* normalisation ripped from above */
1981 s = expciphers;
1982 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1983
1984 err = NULL;
1985
1986 ctx = SSL_CTX_new(SSLv23_server_method());
1987 if (!ctx)
1988   {
1989   ERR_error_string(ERR_get_error(), ssl_errstring);
1990   return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1991   }
1992
1993 DEBUG(D_tls)
1994   debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1995
1996 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1997   {
1998   ERR_error_string(ERR_get_error(), ssl_errstring);
1999   err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2000   }
2001
2002 SSL_CTX_free(ctx);
2003
2004 return err;
2005 }
2006
2007
2008
2009
2010 /*************************************************
2011 *         Report the library versions.           *
2012 *************************************************/
2013
2014 /* There have historically been some issues with binary compatibility in
2015 OpenSSL libraries; if Exim (like many other applications) is built against
2016 one version of OpenSSL but the run-time linker picks up another version,
2017 it can result in serious failures, including crashing with a SIGSEGV.  So
2018 report the version found by the compiler and the run-time version.
2019
2020 Note: some OS vendors backport security fixes without changing the version
2021 number/string, and the version date remains unchanged.  The _build_ date
2022 will change, so we can more usefully assist with version diagnosis by also
2023 reporting the build date.
2024
2025 Arguments:   a FILE* to print the results to
2026 Returns:     nothing
2027 */
2028
2029 void
2030 tls_version_report(FILE *f)
2031 {
2032 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2033            "                          Runtime: %s\n"
2034            "                                 : %s\n",
2035            OPENSSL_VERSION_TEXT,
2036            SSLeay_version(SSLEAY_VERSION),
2037            SSLeay_version(SSLEAY_BUILT_ON));
2038 /* third line is 38 characters for the %s and the line is 73 chars long;
2039 the OpenSSL output includes a "built on: " prefix already. */
2040 }
2041
2042
2043
2044
2045 /*************************************************
2046 *            Random number generation            *
2047 *************************************************/
2048
2049 /* Pseudo-random number generation.  The result is not expected to be
2050 cryptographically strong but not so weak that someone will shoot themselves
2051 in the foot using it as a nonce in input in some email header scheme or
2052 whatever weirdness they'll twist this into.  The result should handle fork()
2053 and avoid repeating sequences.  OpenSSL handles that for us.
2054
2055 Arguments:
2056   max       range maximum
2057 Returns     a random number in range [0, max-1]
2058 */
2059
2060 int
2061 vaguely_random_number(int max)
2062 {
2063 unsigned int r;
2064 int i, needed_len;
2065 static pid_t pidlast = 0;
2066 pid_t pidnow;
2067 uschar *p;
2068 uschar smallbuf[sizeof(r)];
2069
2070 if (max <= 1)
2071   return 0;
2072
2073 pidnow = getpid();
2074 if (pidnow != pidlast)
2075   {
2076   /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2077   is unique for each thread", this doesn't apparently apply across processes,
2078   so our own warning from vaguely_random_number_fallback() applies here too.
2079   Fix per PostgreSQL. */
2080   if (pidlast != 0)
2081     RAND_cleanup();
2082   pidlast = pidnow;
2083   }
2084
2085 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2086 if (!RAND_status())
2087   {
2088   randstuff r;
2089   gettimeofday(&r.tv, NULL);
2090   r.p = getpid();
2091
2092   RAND_seed((uschar *)(&r), sizeof(r));
2093   }
2094 /* We're after pseudo-random, not random; if we still don't have enough data
2095 in the internal PRNG then our options are limited.  We could sleep and hope
2096 for entropy to come along (prayer technique) but if the system is so depleted
2097 in the first place then something is likely to just keep taking it.  Instead,
2098 we'll just take whatever little bit of pseudo-random we can still manage to
2099 get. */
2100
2101 needed_len = sizeof(r);
2102 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2103 asked for a number less than 10. */
2104 for (r = max, i = 0; r; ++i)
2105   r >>= 1;
2106 i = (i + 7) / 8;
2107 if (i < needed_len)
2108   needed_len = i;
2109
2110 /* We do not care if crypto-strong */
2111 i = RAND_pseudo_bytes(smallbuf, needed_len);
2112 if (i < 0)
2113   {
2114   DEBUG(D_all)
2115     debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2116   return vaguely_random_number_fallback(max);
2117   }
2118
2119 r = 0;
2120 for (p = smallbuf; needed_len; --needed_len, ++p)
2121   {
2122   r *= 256;
2123   r += *p;
2124   }
2125
2126 /* We don't particularly care about weighted results; if someone wants
2127 smooth distribution and cares enough then they should submit a patch then. */
2128 return r % max;
2129 }
2130
2131
2132
2133
2134 /*************************************************
2135 *        OpenSSL option parse                    *
2136 *************************************************/
2137
2138 /* Parse one option for tls_openssl_options_parse below
2139
2140 Arguments:
2141   name    one option name
2142   value   place to store a value for it
2143 Returns   success or failure in parsing
2144 */
2145
2146 struct exim_openssl_option {
2147   uschar *name;
2148   long    value;
2149 };
2150 /* We could use a macro to expand, but we need the ifdef and not all the
2151 options document which version they were introduced in.  Policylet: include
2152 all options unless explicitly for DTLS, let the administrator choose which
2153 to apply.
2154
2155 This list is current as of:
2156   ==>  1.0.1b  <==
2157 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2158 */
2159 static struct exim_openssl_option exim_openssl_options[] = {
2160 /* KEEP SORTED ALPHABETICALLY! */
2161 #ifdef SSL_OP_ALL
2162   { US"all", SSL_OP_ALL },
2163 #endif
2164 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2165   { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2166 #endif
2167 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2168   { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2169 #endif
2170 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2171   { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2172 #endif
2173 #ifdef SSL_OP_EPHEMERAL_RSA
2174   { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2175 #endif
2176 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2177   { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2178 #endif
2179 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2180   { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2181 #endif
2182 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2183   { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2184 #endif
2185 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2186   { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2187 #endif
2188 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2189   { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2190 #endif
2191 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2192   { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2193 #endif
2194 #ifdef SSL_OP_NO_COMPRESSION
2195   { US"no_compression", SSL_OP_NO_COMPRESSION },
2196 #endif
2197 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2198   { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2199 #endif
2200 #ifdef SSL_OP_NO_SSLv2
2201   { US"no_sslv2", SSL_OP_NO_SSLv2 },
2202 #endif
2203 #ifdef SSL_OP_NO_SSLv3
2204   { US"no_sslv3", SSL_OP_NO_SSLv3 },
2205 #endif
2206 #ifdef SSL_OP_NO_TICKET
2207   { US"no_ticket", SSL_OP_NO_TICKET },
2208 #endif
2209 #ifdef SSL_OP_NO_TLSv1
2210   { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2211 #endif
2212 #ifdef SSL_OP_NO_TLSv1_1
2213 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2214   /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2215 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2216 #else
2217   { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2218 #endif
2219 #endif
2220 #ifdef SSL_OP_NO_TLSv1_2
2221   { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2222 #endif
2223 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2224   { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2225 #endif
2226 #ifdef SSL_OP_SINGLE_DH_USE
2227   { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2228 #endif
2229 #ifdef SSL_OP_SINGLE_ECDH_USE
2230   { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2231 #endif
2232 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2233   { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2234 #endif
2235 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2236   { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2237 #endif
2238 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2239   { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2240 #endif
2241 #ifdef SSL_OP_TLS_D5_BUG
2242   { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2243 #endif
2244 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2245   { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2246 #endif
2247 };
2248 static int exim_openssl_options_size =
2249   sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2250
2251
2252 static BOOL
2253 tls_openssl_one_option_parse(uschar *name, long *value)
2254 {
2255 int first = 0;
2256 int last = exim_openssl_options_size;
2257 while (last > first)
2258   {
2259   int middle = (first + last)/2;
2260   int c = Ustrcmp(name, exim_openssl_options[middle].name);
2261   if (c == 0)
2262     {
2263     *value = exim_openssl_options[middle].value;
2264     return TRUE;
2265     }
2266   else if (c > 0)
2267     first = middle + 1;
2268   else
2269     last = middle;
2270   }
2271 return FALSE;
2272 }
2273
2274
2275
2276
2277 /*************************************************
2278 *        OpenSSL option parsing logic            *
2279 *************************************************/
2280
2281 /* OpenSSL has a number of compatibility options which an administrator might
2282 reasonably wish to set.  Interpret a list similarly to decode_bits(), so that
2283 we look like log_selector.
2284
2285 Arguments:
2286   option_spec  the administrator-supplied string of options
2287   results      ptr to long storage for the options bitmap
2288 Returns        success or failure
2289 */
2290
2291 BOOL
2292 tls_openssl_options_parse(uschar *option_spec, long *results)
2293 {
2294 long result, item;
2295 uschar *s, *end;
2296 uschar keep_c;
2297 BOOL adding, item_parsed;
2298
2299 result = 0L;
2300 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2301  * from default because it increases BEAST susceptibility. */
2302 #ifdef SSL_OP_NO_SSLv2
2303 result |= SSL_OP_NO_SSLv2;
2304 #endif
2305
2306 if (option_spec == NULL)
2307   {
2308   *results = result;
2309   return TRUE;
2310   }
2311
2312 for (s=option_spec; *s != '\0'; /**/)
2313   {
2314   while (isspace(*s)) ++s;
2315   if (*s == '\0')
2316     break;
2317   if (*s != '+' && *s != '-')
2318     {
2319     DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2320         "+ or - expected but found \"%s\"\n", s);
2321     return FALSE;
2322     }
2323   adding = *s++ == '+';
2324   for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2325   keep_c = *end;
2326   *end = '\0';
2327   item_parsed = tls_openssl_one_option_parse(s, &item);
2328   if (!item_parsed)
2329     {
2330     DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2331     return FALSE;
2332     }
2333   DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2334       adding ? "adding" : "removing", result, item, s);
2335   if (adding)
2336     result |= item;
2337   else
2338     result &= ~item;
2339   *end = keep_c;
2340   s = end;
2341   }
2342
2343 *results = result;
2344 return TRUE;
2345 }
2346
2347 /* vi: aw ai sw=2
2348 */
2349 /* End of tls-openssl.c */