src/src/tls-openssl.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2018 */
   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 OPENSSL_NO_ECDH
  26 # include <openssl/ec.h>
  27 #endif
  28 #ifndef DISABLE_OCSP
  29 # include <openssl/ocsp.h>
  30 #endif
  31 #ifdef SUPPORT_DANE
  32 # include "danessl.h"
  33 #endif
  34
  35
  36 #ifndef DISABLE_OCSP
  37 # define EXIM_OCSP_SKEW_SECONDS (300L)
  38 # define EXIM_OCSP_MAX_AGE (-1L)
  39 #endif
  40
  41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
  42 # define EXIM_HAVE_OPENSSL_TLSEXT
  43 #endif
  44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
  45 # define EXIM_HAVE_RSA_GENKEY_EX
  46 #endif
  47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
  48 # define EXIM_HAVE_OCSP_RESP_COUNT
  49 #else
  50 # define EXIM_HAVE_EPHEM_RSA_KEX
  51 # define EXIM_HAVE_RAND_PSEUDO
  52 #endif
  53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
  54 # define EXIM_HAVE_SHA256
  55 #endif
  56
  57 /* X509_check_host provides sane certificate hostname checking, but was added
  58 to OpenSSL late, after other projects forked off the code-base.  So in
  59 addition to guarding against the base version number, beware that LibreSSL
  60 does not (at this time) support this function.
  61
  62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
  63 opt to disentangle and ask a LibreSSL user to provide glue for a third
  64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
  65 into even twistier knots.  If LibreSSL gains the same API, we can just
  66 change this guard and punt the issue for a while longer. */
  67
  68 #ifndef LIBRESSL_VERSION_NUMBER
  69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
  70 #  define EXIM_HAVE_OPENSSL_CHECKHOST
  71 #  define EXIM_HAVE_OPENSSL_DH_BITS
  72 #  define EXIM_HAVE_OPENSSL_TLS_METHOD
  73 #  define EXIM_HAVE_OPENSSL_KEYLOG
  74 # else
  75 #  define EXIM_NEED_OPENSSL_INIT
  76 # endif
  77 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
  78     && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
  79 #  define EXIM_HAVE_OPENSSL_CHECKHOST
  80 # endif
  81 #endif
  82
  83 #if !defined(LIBRESSL_VERSION_NUMBER) \
  84     || LIBRESSL_VERSION_NUMBER >= 0x20010000L
  85 # if !defined(OPENSSL_NO_ECDH)
  86 #  if OPENSSL_VERSION_NUMBER >= 0x0090800fL
  87 #   define EXIM_HAVE_ECDH
  88 #  endif
  89 #  if OPENSSL_VERSION_NUMBER >= 0x10002000L
  90 #   define EXIM_HAVE_OPENSSL_EC_NIST2NID
  91 #  endif
  92 # endif
  93 #endif
  94
  95 #ifndef LIBRESSL_VERSION_NUMBER
  96 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
  97 #  define OPENSSL_HAVE_KEYLOG_CB
  98 #  define OPENSSL_HAVE_NUM_TICKETS
  99 # endif
 100 #endif
 101
 102 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
 103 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
 104 # define DISABLE_OCSP
 105 #endif
 106
 107 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
 108 # include <openssl/x509v3.h>
 109 #endif
 110
 111 /*************************************************
 112 *        OpenSSL option parse                    *
 113 *************************************************/
 114
 115 typedef struct exim_openssl_option {
 116   uschar *name;
 117   long    value;
 118 } exim_openssl_option;
 119 /* We could use a macro to expand, but we need the ifdef and not all the
 120 options document which version they were introduced in.  Policylet: include
 121 all options unless explicitly for DTLS, let the administrator choose which
 122 to apply.
 123
 124 This list is current as of:
 125   ==>  1.0.1b  <==
 126 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
 127 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
 128 */
 129 static exim_openssl_option exim_openssl_options[] = {
 130 /* KEEP SORTED ALPHABETICALLY! */
 131 #ifdef SSL_OP_ALL
 132   { US"all", SSL_OP_ALL },
 133 #endif
 134 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
 135   { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
 136 #endif
 137 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
 138   { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
 139 #endif
 140 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
 141   { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
 142 #endif
 143 #ifdef SSL_OP_EPHEMERAL_RSA
 144   { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
 145 #endif
 146 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
 147   { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
 148 #endif
 149 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
 150   { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
 151 #endif
 152 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
 153   { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
 154 #endif
 155 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
 156   { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
 157 #endif
 158 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
 159   { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
 160 #endif
 161 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
 162   { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
 163 #endif
 164 #ifdef SSL_OP_NO_COMPRESSION
 165   { US"no_compression", SSL_OP_NO_COMPRESSION },
 166 #endif
 167 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
 168   { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
 169 #endif
 170 #ifdef SSL_OP_NO_SSLv2
 171   { US"no_sslv2", SSL_OP_NO_SSLv2 },
 172 #endif
 173 #ifdef SSL_OP_NO_SSLv3
 174   { US"no_sslv3", SSL_OP_NO_SSLv3 },
 175 #endif
 176 #ifdef SSL_OP_NO_TICKET
 177   { US"no_ticket", SSL_OP_NO_TICKET },
 178 #endif
 179 #ifdef SSL_OP_NO_TLSv1
 180   { US"no_tlsv1", SSL_OP_NO_TLSv1 },
 181 #endif
 182 #ifdef SSL_OP_NO_TLSv1_1
 183 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
 184   /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
 185 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
 186 #else
 187   { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
 188 #endif
 189 #endif
 190 #ifdef SSL_OP_NO_TLSv1_2
 191   { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
 192 #endif
 193 #ifdef SSL_OP_NO_TLSv1_3
 194   { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
 195 #endif
 196 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
 197   { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
 198 #endif
 199 #ifdef SSL_OP_SINGLE_DH_USE
 200   { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
 201 #endif
 202 #ifdef SSL_OP_SINGLE_ECDH_USE
 203   { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
 204 #endif
 205 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
 206   { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
 207 #endif
 208 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
 209   { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
 210 #endif
 211 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
 212   { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
 213 #endif
 214 #ifdef SSL_OP_TLS_D5_BUG
 215   { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
 216 #endif
 217 #ifdef SSL_OP_TLS_ROLLBACK_BUG
 218   { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
 219 #endif
 220 };
 221
 222 #ifndef MACRO_PREDEF
 223 static int exim_openssl_options_size = nelem(exim_openssl_options);
 224 #endif
 225
 226 #ifdef MACRO_PREDEF
 227 void
 228 options_tls(void)
 229 {
 230 uschar buf[64];
 231
 232 for (struct exim_openssl_option * o = exim_openssl_options;
 233      o < exim_openssl_options + nelem(exim_openssl_options); o++)
 234   {
 235   /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
 236   being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
 237
 238   spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
 239   builtin_macro_create(buf);
 240   }
 241 }
 242 #else
 243
 244 /******************************************************************************/
 245
 246 /* Structure for collecting random data for seeding. */
 247
 248 typedef struct randstuff {
 249   struct timeval tv;
 250   pid_t          p;
 251 } randstuff;
 252
 253 /* Local static variables */
 254
 255 static BOOL client_verify_callback_called = FALSE;
 256 static BOOL server_verify_callback_called = FALSE;
 257 static const uschar *sid_ctx = US"exim";
 258
 259 /* We have three different contexts to care about.
 260
 261 Simple case: client, `client_ctx`
 262  As a client, we can be doing a callout or cut-through delivery while receiving
 263  a message.  So we have a client context, which should have options initialised
 264  from the SMTP Transport.  We may also concurrently want to make TLS connections
 265  to utility daemons, so client-contexts are allocated and passed around in call
 266  args rather than using a gobal.
 267
 268 Server:
 269  There are two cases: with and without ServerNameIndication from the client.
 270  Given TLS SNI, we can be using different keys, certs and various other
 271  configuration settings, because they're re-expanded with $tls_sni set.  This
 272  allows vhosting with TLS.  This SNI is sent in the handshake.
 273  A client might not send SNI, so we need a fallback, and an initial setup too.
 274  So as a server, we start out using `server_ctx`.
 275  If SNI is sent by the client, then we as server, mid-negotiation, try to clone
 276  `server_sni` from `server_ctx` and then initialise settings by re-expanding
 277  configuration.
 278 */
 279
 280 typedef struct {
 281   SSL_CTX *     ctx;
 282   SSL *         ssl;
 283 } exim_openssl_client_tls_ctx;
 284
 285 static SSL_CTX *server_ctx = NULL;
 286 static SSL     *server_ssl = NULL;
 287
 288 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 289 static SSL_CTX *server_sni = NULL;
 290 #endif
 291
 292 static char ssl_errstring[256];
 293
 294 static int  ssl_session_timeout = 200;
 295 static BOOL client_verify_optional = FALSE;
 296 static BOOL server_verify_optional = FALSE;
 297
 298 static BOOL reexpand_tls_files_for_sni = FALSE;
 299
 300
 301 typedef struct tls_ext_ctx_cb {
 302   uschar *certificate;
 303   uschar *privatekey;
 304   BOOL is_server;
 305 #ifndef DISABLE_OCSP
 306   STACK_OF(X509) *verify_stack;         /* chain for verifying the proof */
 307   union {
 308     struct {
 309       uschar        *file;
 310       uschar        *file_expanded;
 311       OCSP_RESPONSE *response;
 312     } server;
 313     struct {
 314       X509_STORE    *verify_store;      /* non-null if status requested */
 315       BOOL          verify_required;
 316     } client;
 317   } u_ocsp;
 318 #endif
 319   uschar *dhparam;
 320   /* these are cached from first expand */
 321   uschar *server_cipher_list;
 322   /* only passed down to tls_error: */
 323   host_item *host;
 324   const uschar * verify_cert_hostnames;
 325 #ifndef DISABLE_EVENT
 326   uschar * event_action;
 327 #endif
 328 } tls_ext_ctx_cb;
 329
 330 /* should figure out a cleanup of API to handle state preserved per
 331 implementation, for various reasons, which can be void * in the APIs.
 332 For now, we hack around it. */
 333 tls_ext_ctx_cb *client_static_cbinfo = NULL;
 334 tls_ext_ctx_cb *server_static_cbinfo = NULL;
 335
 336 static int
 337 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
 338     int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
 339
 340 /* Callbacks */
 341 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
 342 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
 343 #endif
 344 #ifndef DISABLE_OCSP
 345 static int tls_server_stapling_cb(SSL *s, void *arg);
 346 #endif
 347
 348
 349 /*************************************************
 350 *               Handle TLS error                 *
 351 *************************************************/
 352
 353 /* Called from lots of places when errors occur before actually starting to do
 354 the TLS handshake, that is, while the session is still in clear. Always returns
 355 DEFER for a server and FAIL for a client so that most calls can use "return
 356 tls_error(...)" to do this processing and then give an appropriate return. A
 357 single function is used for both server and client, because it is called from
 358 some shared functions.
 359
 360 Argument:
 361   prefix    text to include in the logged error
 362   host      NULL if setting up a server;
 363             the connected host if setting up a client
 364   msg       error message or NULL if we should ask OpenSSL
 365   errstr    pointer to output error message
 366
 367 Returns:    OK/DEFER/FAIL
 368 */
 369
 370 static int
 371 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
 372 {
 373 if (!msg)
 374   {
 375   ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
 376   msg = US ssl_errstring;
 377   }
 378
 379 msg = string_sprintf("(%s): %s", prefix, msg);
 380 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
 381 if (errstr) *errstr = msg;
 382 return host ? FAIL : DEFER;
 383 }
 384
 385
 386
 387 /*************************************************
 388 *        Callback to generate RSA key            *
 389 *************************************************/
 390
 391 /*
 392 Arguments:
 393   s          SSL connection (not used)
 394   export     not used
 395   keylength  keylength
 396
 397 Returns:     pointer to generated key
 398 */
 399
 400 static RSA *
 401 rsa_callback(SSL *s, int export, int keylength)
 402 {
 403 RSA *rsa_key;
 404 #ifdef EXIM_HAVE_RSA_GENKEY_EX
 405 BIGNUM *bn = BN_new();
 406 #endif
 407
 408 export = export;     /* Shut picky compilers up */
 409 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
 410
 411 #ifdef EXIM_HAVE_RSA_GENKEY_EX
 412 if (  !BN_set_word(bn, (unsigned long)RSA_F4)
 413    || !(rsa_key = RSA_new())
 414    || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
 415    )
 416 #else
 417 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
 418 #endif
 419
 420   {
 421   ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
 422   log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
 423     ssl_errstring);
 424   return NULL;
 425   }
 426 return rsa_key;
 427 }
 428
 429
 430
 431 /* Extreme debug
 432 #ifndef DISABLE_OCSP
 433 void
 434 x509_store_dump_cert_s_names(X509_STORE * store)
 435 {
 436 STACK_OF(X509_OBJECT) * roots= store->objs;
 437 static uschar name[256];
 438
 439 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
 440   {
 441   X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
 442   if(tmp_obj->type == X509_LU_X509)
 443     {
 444     X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
 445     if (X509_NAME_oneline(sn, CS name, sizeof(name)))
 446       {
 447       name[sizeof(name)-1] = '\0';
 448       debug_printf(" %s\n", name);
 449       }
 450     }
 451   }
 452 }
 453 #endif
 454 */
 455
 456
 457 #ifndef DISABLE_EVENT
 458 static int
 459 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
 460   BOOL *calledp, const BOOL *optionalp, const uschar * what)
 461 {
 462 uschar * ev;
 463 uschar * yield;
 464 X509 * old_cert;
 465
 466 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
 467 if (ev)
 468   {
 469   DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
 470   old_cert = tlsp->peercert;
 471   tlsp->peercert = X509_dup(cert);
 472   /* NB we do not bother setting peerdn */
 473   if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
 474     {
 475     log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
 476                 "depth=%d cert=%s: %s",
 477               tlsp == &tls_out ? deliver_host_address : sender_host_address,
 478               what, depth, dn, yield);
 479     *calledp = TRUE;
 480     if (!*optionalp)
 481       {
 482       if (old_cert) tlsp->peercert = old_cert;  /* restore 1st failing cert */
 483       return 1;                     /* reject (leaving peercert set) */
 484       }
 485     DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
 486       "(host in tls_try_verify_hosts)\n");
 487     }
 488   X509_free(tlsp->peercert);
 489   tlsp->peercert = old_cert;
 490   }
 491 return 0;
 492 }
 493 #endif
 494
 495 /*************************************************
 496 *        Callback for verification               *
 497 *************************************************/
 498
 499 /* The SSL library does certificate verification if set up to do so. This
 500 callback has the current yes/no state is in "state". If verification succeeded,
 501 we set the certificate-verified flag. If verification failed, what happens
 502 depends on whether the client is required to present a verifiable certificate
 503 or not.
 504
 505 If verification is optional, we change the state to yes, but still log the
 506 verification error. For some reason (it really would help to have proper
 507 documentation of OpenSSL), this callback function then gets called again, this
 508 time with state = 1.  We must take care not to set the private verified flag on
 509 the second time through.
 510
 511 Note: this function is not called if the client fails to present a certificate
 512 when asked. We get here only if a certificate has been received. Handling of
 513 optional verification for this case is done when requesting SSL to verify, by
 514 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
 515
 516 May be called multiple times for different issues with a certificate, even
 517 for a given "depth" in the certificate chain.
 518
 519 Arguments:
 520   preverify_ok current yes/no state as 1/0
 521   x509ctx      certificate information.
 522   tlsp         per-direction (client vs. server) support data
 523   calledp      has-been-called flag
 524   optionalp    verification-is-optional flag
 525
 526 Returns:     0 if verification should fail, otherwise 1
 527 */
 528
 529 static int
 530 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
 531   tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
 532 {
 533 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
 534 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
 535 uschar dn[256];
 536
 537 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
 538   {
 539   DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
 540   log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
 541     tlsp == &tls_out ? deliver_host_address : sender_host_address);
 542   return 0;
 543   }
 544 dn[sizeof(dn)-1] = '\0';
 545
 546 if (preverify_ok == 0)
 547   {
 548   uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
 549       *verify_mode, sender_host_address)
 550     : US"";
 551   log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
 552     tlsp == &tls_out ? deliver_host_address : sender_host_address,
 553     extra, depth,
 554     X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
 555   *calledp = TRUE;
 556   if (!*optionalp)
 557     {
 558     if (!tlsp->peercert)
 559       tlsp->peercert = X509_dup(cert);  /* record failing cert */
 560     return 0;                           /* reject */
 561     }
 562   DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
 563     "tls_try_verify_hosts)\n");
 564   }
 565
 566 else if (depth != 0)
 567   {
 568   DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
 569 #ifndef DISABLE_OCSP
 570   if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
 571     {   /* client, wanting stapling  */
 572     /* Add the server cert's signing chain as the one
 573     for the verification of the OCSP stapled information. */
 574
 575     if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
 576                              cert))
 577       ERR_clear_error();
 578     sk_X509_push(client_static_cbinfo->verify_stack, cert);
 579     }
 580 #endif
 581 #ifndef DISABLE_EVENT
 582     if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
 583       return 0;                         /* reject, with peercert set */
 584 #endif
 585   }
 586 else
 587   {
 588   const uschar * verify_cert_hostnames;
 589
 590   if (  tlsp == &tls_out
 591      && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
 592         /* client, wanting hostname check */
 593     {
 594
 595 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
 596 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
 597 #  define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
 598 # endif
 599 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
 600 #  define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
 601 # endif
 602     int sep = 0;
 603     const uschar * list = verify_cert_hostnames;
 604     uschar * name;
 605     int rc;
 606     while ((name = string_nextinlist(&list, &sep, NULL, 0)))
 607       if ((rc = X509_check_host(cert, CCS name, 0,
 608                   X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
 609                   | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
 610                   NULL)))
 611         {
 612         if (rc < 0)
 613           {
 614           log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
 615             tlsp == &tls_out ? deliver_host_address : sender_host_address);
 616           name = NULL;
 617           }
 618         break;
 619         }
 620     if (!name)
 621 #else
 622     if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
 623 #endif
 624       {
 625       uschar * extra = verify_mode
 626         ? string_sprintf(" (during %c-verify for [%s])",
 627           *verify_mode, sender_host_address)
 628         : US"";
 629       log_write(0, LOG_MAIN,
 630         "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
 631         tlsp == &tls_out ? deliver_host_address : sender_host_address,
 632         extra, dn, verify_cert_hostnames);
 633       *calledp = TRUE;
 634       if (!*optionalp)
 635         {
 636         if (!tlsp->peercert)
 637           tlsp->peercert = X509_dup(cert);      /* record failing cert */
 638         return 0;                               /* reject */
 639         }
 640       DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
 641         "tls_try_verify_hosts)\n");
 642       }
 643     }
 644
 645 #ifndef DISABLE_EVENT
 646   if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
 647     return 0;                           /* reject, with peercert set */
 648 #endif
 649
 650   DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
 651     *calledp ? "" : " authenticated", dn);
 652   if (!*calledp) tlsp->certificate_verified = TRUE;
 653   *calledp = TRUE;
 654   }
 655
 656 return 1;   /* accept, at least for this level */
 657 }
 658
 659 static int
 660 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
 661 {
 662 return verify_callback(preverify_ok, x509ctx, &tls_out,
 663   &client_verify_callback_called, &client_verify_optional);
 664 }
 665
 666 static int
 667 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
 668 {
 669 return verify_callback(preverify_ok, x509ctx, &tls_in,
 670   &server_verify_callback_called, &server_verify_optional);
 671 }
 672
 673
 674 #ifdef SUPPORT_DANE
 675
 676 /* This gets called *by* the dane library verify callback, which interposes
 677 itself.
 678 */
 679 static int
 680 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
 681 {
 682 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
 683 uschar dn[256];
 684 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
 685 #ifndef DISABLE_EVENT
 686 BOOL dummy_called, optional = FALSE;
 687 #endif
 688
 689 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
 690   {
 691   DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
 692   log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
 693     deliver_host_address);
 694   return 0;
 695   }
 696 dn[sizeof(dn)-1] = '\0';
 697
 698 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
 699   preverify_ok ? "ok":"BAD", depth, dn);
 700
 701 #ifndef DISABLE_EVENT
 702   if (verify_event(&tls_out, cert, depth, dn,
 703           &dummy_called, &optional, US"DANE"))
 704     return 0;                           /* reject, with peercert set */
 705 #endif
 706
 707 if (preverify_ok == 1)
 708   {
 709   tls_out.dane_verified = tls_out.certificate_verified = TRUE;
 710 #ifndef DISABLE_OCSP
 711   if (client_static_cbinfo->u_ocsp.client.verify_store)
 712     {   /* client, wanting stapling  */
 713     /* Add the server cert's signing chain as the one
 714     for the verification of the OCSP stapled information. */
 715
 716     if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
 717                              cert))
 718       ERR_clear_error();
 719     sk_X509_push(client_static_cbinfo->verify_stack, cert);
 720     }
 721 #endif
 722   }
 723 else
 724   {
 725   int err = X509_STORE_CTX_get_error(x509ctx);
 726   DEBUG(D_tls)
 727     debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
 728   if (err == X509_V_ERR_APPLICATION_VERIFICATION)
 729     preverify_ok = 1;
 730   }
 731 return preverify_ok;
 732 }
 733
 734 #endif  /*SUPPORT_DANE*/
 735
 736
 737 /*************************************************
 738 *           Information callback                 *
 739 *************************************************/
 740
 741 /* The SSL library functions call this from time to time to indicate what they
 742 are doing. We copy the string to the debugging output when TLS debugging has
 743 been requested.
 744
 745 Arguments:
 746   s         the SSL connection
 747   where
 748   ret
 749
 750 Returns:    nothing
 751 */
 752
 753 static void
 754 info_callback(SSL *s, int where, int ret)
 755 {
 756 DEBUG(D_tls)
 757   {
 758   const uschar * str;
 759
 760   if (where & SSL_ST_CONNECT)
 761      str = US"SSL_connect";
 762   else if (where & SSL_ST_ACCEPT)
 763      str = US"SSL_accept";
 764   else
 765      str = US"SSL info (undefined)";
 766
 767   if (where & SSL_CB_LOOP)
 768      debug_printf("%s: %s\n", str, SSL_state_string_long(s));
 769   else if (where & SSL_CB_ALERT)
 770     debug_printf("SSL3 alert %s:%s:%s\n",
 771           str = where & SSL_CB_READ ? US"read" : US"write",
 772           SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
 773   else if (where & SSL_CB_EXIT)
 774      if (ret == 0)
 775         debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
 776      else if (ret < 0)
 777         debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
 778   else if (where & SSL_CB_HANDSHAKE_START)
 779      debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
 780   else if (where & SSL_CB_HANDSHAKE_DONE)
 781      debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
 782   }
 783 }
 784
 785 static void
 786 keylog_callback(const SSL *ssl, const char *line)
 787 {
 788 DEBUG(D_tls) debug_printf("%.200s\n", line);
 789 }
 790
 791
 792
 793 /*************************************************
 794 *                Initialize for DH               *
 795 *************************************************/
 796
 797 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
 798
 799 Arguments:
 800   sctx      The current SSL CTX (inbound or outbound)
 801   dhparam   DH parameter file or fixed parameter identity string
 802   host      connected host, if client; NULL if server
 803   errstr    error string pointer
 804
 805 Returns:    TRUE if OK (nothing to set up, or setup worked)
 806 */
 807
 808 static BOOL
 809 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
 810 {
 811 BIO *bio;
 812 DH *dh;
 813 uschar *dhexpanded;
 814 const char *pem;
 815 int dh_bitsize;
 816
 817 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
 818   return FALSE;
 819
 820 if (!dhexpanded || !*dhexpanded)
 821   bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
 822 else if (dhexpanded[0] == '/')
 823   {
 824   if (!(bio = BIO_new_file(CS dhexpanded, "r")))
 825     {
 826     tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
 827           host, US strerror(errno), errstr);
 828     return FALSE;
 829     }
 830   }
 831 else
 832   {
 833   if (Ustrcmp(dhexpanded, "none") == 0)
 834     {
 835     DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
 836     return TRUE;
 837     }
 838
 839   if (!(pem = std_dh_prime_named(dhexpanded)))
 840     {
 841     tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
 842         host, US strerror(errno), errstr);
 843     return FALSE;
 844     }
 845   bio = BIO_new_mem_buf(CS pem, -1);
 846   }
 847
 848 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
 849   {
 850   BIO_free(bio);
 851   tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
 852       host, NULL, errstr);
 853   return FALSE;
 854   }
 855
 856 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
 857  * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
 858  * 2236.  But older OpenSSL can only report in bytes (octets), not bits.
 859  * If someone wants to dance at the edge, then they can raise the limit or use
 860  * current libraries. */
 861 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
 862 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
 863  * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
 864 dh_bitsize = DH_bits(dh);
 865 #else
 866 dh_bitsize = 8 * DH_size(dh);
 867 #endif
 868
 869 /* Even if it is larger, we silently return success rather than cause things
 870  * to fail out, so that a too-large DH will not knock out all TLS; it's a
 871  * debatable choice. */
 872 if (dh_bitsize > tls_dh_max_bits)
 873   {
 874   DEBUG(D_tls)
 875     debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
 876         dh_bitsize, tls_dh_max_bits);
 877   }
 878 else
 879   {
 880   SSL_CTX_set_tmp_dh(sctx, dh);
 881   DEBUG(D_tls)
 882     debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
 883       dhexpanded ? dhexpanded : US"default", dh_bitsize);
 884   }
 885
 886 DH_free(dh);
 887 BIO_free(bio);
 888
 889 return TRUE;
 890 }
 891
 892
 893
 894
 895 /*************************************************
 896 *               Initialize for ECDH              *
 897 *************************************************/
 898
 899 /* Load parameters for ECDH encryption.
 900
 901 For now, we stick to NIST P-256 because: it's simple and easy to configure;
 902 it avoids any patent issues that might bite redistributors; despite events in
 903 the news and concerns over curve choices, we're not cryptographers, we're not
 904 pretending to be, and this is "good enough" to be better than no support,
 905 protecting against most adversaries.  Given another year or two, there might
 906 be sufficient clarity about a "right" way forward to let us make an informed
 907 decision, instead of a knee-jerk reaction.
 908
 909 Longer-term, we should look at supporting both various named curves and
 910 external files generated with "openssl ecparam", much as we do for init_dh().
 911 We should also support "none" as a value, to explicitly avoid initialisation.
 912
 913 Patches welcome.
 914
 915 Arguments:
 916   sctx      The current SSL CTX (inbound or outbound)
 917   host      connected host, if client; NULL if server
 918   errstr    error string pointer
 919
 920 Returns:    TRUE if OK (nothing to set up, or setup worked)
 921 */
 922
 923 static BOOL
 924 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
 925 {
 926 #ifdef OPENSSL_NO_ECDH
 927 return TRUE;
 928 #else
 929
 930 EC_KEY * ecdh;
 931 uschar * exp_curve;
 932 int nid;
 933 BOOL rv;
 934
 935 if (host)       /* No ECDH setup for clients, only for servers */
 936   return TRUE;
 937
 938 # ifndef EXIM_HAVE_ECDH
 939 DEBUG(D_tls)
 940   debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
 941 return TRUE;
 942 # else
 943
 944 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
 945   return FALSE;
 946 if (!exp_curve || !*exp_curve)
 947   return TRUE;
 948
 949 /* "auto" needs to be handled carefully.
 950  * OpenSSL <  1.0.2: we do not select anything, but fallback to prime256v1
 951  * OpenSSL <  1.1.0: we have to call SSL_CTX_set_ecdh_auto
 952  *                   (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
 953  * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
 954  *                   https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
 955  */
 956 if (Ustrcmp(exp_curve, "auto") == 0)
 957   {
 958 #if OPENSSL_VERSION_NUMBER < 0x10002000L
 959   DEBUG(D_tls) debug_printf(
 960     "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
 961   exp_curve = US"prime256v1";
 962 #else
 963 # if defined SSL_CTRL_SET_ECDH_AUTO
 964   DEBUG(D_tls) debug_printf(
 965     "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
 966   SSL_CTX_set_ecdh_auto(sctx, 1);
 967   return TRUE;
 968 # else
 969   DEBUG(D_tls) debug_printf(
 970     "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
 971   return TRUE;
 972 # endif
 973 #endif
 974   }
 975
 976 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
 977 if (  (nid = OBJ_sn2nid       (CCS exp_curve)) == NID_undef
 978 #   ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
 979    && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
 980 #   endif
 981    )
 982   {
 983   tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
 984     host, NULL, errstr);
 985   return FALSE;
 986   }
 987
 988 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
 989   {
 990   tls_error(US"Unable to create ec curve", host, NULL, errstr);
 991   return FALSE;
 992   }
 993
 994 /* The "tmp" in the name here refers to setting a temporary key
 995 not to the stability of the interface. */
 996
 997 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
 998   tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
 999 else
1000   DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1001
1002 EC_KEY_free(ecdh);
1003 return !rv;
1004
1005 # endif /*EXIM_HAVE_ECDH*/
1006 #endif /*OPENSSL_NO_ECDH*/
1007 }
1008
1009
1010
1011
1012 #ifndef DISABLE_OCSP
1013 /*************************************************
1014 *       Load OCSP information into state         *
1015 *************************************************/
1016 /* Called to load the server OCSP response from the given file into memory, once
1017 caller has determined this is needed.  Checks validity.  Debugs a message
1018 if invalid.
1019
1020 ASSUMES: single response, for single cert.
1021
1022 Arguments:
1023   sctx            the SSL_CTX* to update
1024   cbinfo          various parts of session state
1025   expanded        the filename putatively holding an OCSP response
1026
1027 */
1028
1029 static void
1030 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1031 {
1032 BIO * bio;
1033 OCSP_RESPONSE * resp;
1034 OCSP_BASICRESP * basic_response;
1035 OCSP_SINGLERESP * single_response;
1036 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1037 STACK_OF(X509) * sk;
1038 unsigned long verify_flags;
1039 int status, reason, i;
1040
1041 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1042 if (cbinfo->u_ocsp.server.response)
1043   {
1044   OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1045   cbinfo->u_ocsp.server.response = NULL;
1046   }
1047
1048 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1049   {
1050   DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1051       cbinfo->u_ocsp.server.file_expanded);
1052   return;
1053   }
1054
1055 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1056 BIO_free(bio);
1057 if (!resp)
1058   {
1059   DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1060   return;
1061   }
1062
1063 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1064   {
1065   DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1066       OCSP_response_status_str(status), status);
1067   goto bad;
1068   }
1069
1070 if (!(basic_response = OCSP_response_get1_basic(resp)))
1071   {
1072   DEBUG(D_tls)
1073     debug_printf("OCSP response parse error: unable to extract basic response.\n");
1074   goto bad;
1075   }
1076
1077 sk = cbinfo->verify_stack;
1078 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1079
1080 /* May need to expose ability to adjust those flags?
1081 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1082 OCSP_TRUSTOTHER OCSP_NOINTERN */
1083
1084 /* This does a full verify on the OCSP proof before we load it for serving
1085 up; possibly overkill - just date-checks might be nice enough.
1086
1087 OCSP_basic_verify takes a "store" arg, but does not
1088 use it for the chain verification, which is all we do
1089 when OCSP_NOVERIFY is set.  The content from the wire
1090 "basic_response" and a cert-stack "sk" are all that is used.
1091
1092 We have a stack, loaded in setup_certs() if tls_verify_certificates
1093 was a file (not a directory, or "system").  It is unfortunate we
1094 cannot used the connection context store, as that would neatly
1095 handle the "system" case too, but there seems to be no library
1096 function for getting a stack from a store.
1097 [ In OpenSSL 1.1 - ?  X509_STORE_CTX_get0_chain(ctx) ? ]
1098 We do not free the stack since it could be needed a second time for
1099 SNI handling.
1100
1101 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1102 be a public interface into the OpenSSL library (there's no manual entry) -
1103 But what with?  We also use OCSP_basic_verify in the client stapling callback.
1104 And there we NEED it; we must verify that status... unless the
1105 library does it for us anyway?  */
1106
1107 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1108   {
1109   DEBUG(D_tls)
1110     {
1111     ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1112     debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1113     }
1114   goto bad;
1115   }
1116
1117 /* Here's the simplifying assumption: there's only one response, for the
1118 one certificate we use, and nothing for anything else in a chain.  If this
1119 proves false, we need to extract a cert id from our issued cert
1120 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1121 right cert in the stack and then calls OCSP_single_get0_status()).
1122
1123 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1124
1125 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1126   {
1127   DEBUG(D_tls)
1128     debug_printf("Unable to get first response from OCSP basic response.\n");
1129   goto bad;
1130   }
1131
1132 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1133 if (status != V_OCSP_CERTSTATUS_GOOD)
1134   {
1135   DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1136       OCSP_cert_status_str(status), status,
1137       OCSP_crl_reason_str(reason), reason);
1138   goto bad;
1139   }
1140
1141 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1142   {
1143   DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1144   goto bad;
1145   }
1146
1147 supply_response:
1148   cbinfo->u_ocsp.server.response = resp;        /*XXX stack?*/
1149 return;
1150
1151 bad:
1152   if (f.running_in_test_harness)
1153     {
1154     extern char ** environ;
1155     if (environ) for (uschar ** p = USS environ; *p; p++)
1156       if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1157         {
1158         DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1159         goto supply_response;
1160         }
1161     }
1162 return;
1163 }
1164 #endif  /*!DISABLE_OCSP*/
1165
1166
1167
1168
1169 /* Create and install a selfsigned certificate, for use in server mode */
1170
1171 static int
1172 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1173 {
1174 X509 * x509 = NULL;
1175 EVP_PKEY * pkey;
1176 RSA * rsa;
1177 X509_NAME * name;
1178 uschar * where;
1179
1180 where = US"allocating pkey";
1181 if (!(pkey = EVP_PKEY_new()))
1182   goto err;
1183
1184 where = US"allocating cert";
1185 if (!(x509 = X509_new()))
1186   goto err;
1187
1188 where = US"generating pkey";
1189 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1190   goto err;
1191
1192 where = US"assigning pkey";
1193 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1194   goto err;
1195
1196 X509_set_version(x509, 2);                              /* N+1 - version 3 */
1197 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1198 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1199 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60);        /* 1 hour */
1200 X509_set_pubkey(x509, pkey);
1201
1202 name = X509_get_subject_name(x509);
1203 X509_NAME_add_entry_by_txt(name, "C",
1204                           MBSTRING_ASC, CUS "UK", -1, -1, 0);
1205 X509_NAME_add_entry_by_txt(name, "O",
1206                           MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1207 X509_NAME_add_entry_by_txt(name, "CN",
1208                           MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1209 X509_set_issuer_name(x509, name);
1210
1211 where = US"signing cert";
1212 if (!X509_sign(x509, pkey, EVP_md5()))
1213   goto err;
1214
1215 where = US"installing selfsign cert";
1216 if (!SSL_CTX_use_certificate(sctx, x509))
1217   goto err;
1218
1219 where = US"installing selfsign key";
1220 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1221   goto err;
1222
1223 return OK;
1224
1225 err:
1226   (void) tls_error(where, NULL, NULL, errstr);
1227   if (x509) X509_free(x509);
1228   if (pkey) EVP_PKEY_free(pkey);
1229   return DEFER;
1230 }
1231
1232
1233
1234
1235 static int
1236 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1237   uschar ** errstr)
1238 {
1239 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1240 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1241   return tls_error(string_sprintf(
1242     "SSL_CTX_use_certificate_chain_file file=%s", file),
1243       cbinfo->host, NULL, errstr);
1244 return 0;
1245 }
1246
1247 static int
1248 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1249   uschar ** errstr)
1250 {
1251 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1252 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1253   return tls_error(string_sprintf(
1254     "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1255 return 0;
1256 }
1257
1258
1259 /*************************************************
1260 *        Expand key and cert file specs          *
1261 *************************************************/
1262
1263 /* Called once during tls_init and possibly again during TLS setup, for a
1264 new context, if Server Name Indication was used and tls_sni was seen in
1265 the certificate string.
1266
1267 Arguments:
1268   sctx            the SSL_CTX* to update
1269   cbinfo          various parts of session state
1270   errstr          error string pointer
1271
1272 Returns:          OK/DEFER/FAIL
1273 */
1274
1275 static int
1276 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1277   uschar ** errstr)
1278 {
1279 uschar *expanded;
1280
1281 if (!cbinfo->certificate)
1282   {
1283   if (!cbinfo->is_server)               /* client */
1284     return OK;
1285                                         /* server */
1286   if (tls_install_selfsign(sctx, errstr) != OK)
1287     return DEFER;
1288   }
1289 else
1290   {
1291   int err;
1292
1293   if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1294       Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1295       Ustrstr(cbinfo->certificate, US"tls_out_sni")
1296      )
1297     reexpand_tls_files_for_sni = TRUE;
1298
1299   if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1300     return DEFER;
1301
1302   if (expanded)
1303     if (cbinfo->is_server)
1304       {
1305       const uschar * file_list = expanded;
1306       int sep = 0;
1307       uschar * file;
1308
1309       while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1310         if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1311           return err;
1312       }
1313     else        /* would there ever be a need for multiple client certs? */
1314       if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1315         return err;
1316
1317   if (  cbinfo->privatekey
1318      && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1319     return DEFER;
1320
1321   /* If expansion was forced to fail, key_expanded will be NULL. If the result
1322   of the expansion is an empty string, ignore it also, and assume the private
1323   key is in the same file as the certificate. */
1324
1325   if (expanded && *expanded)
1326     if (cbinfo->is_server)
1327       {
1328       const uschar * file_list = expanded;
1329       int sep = 0;
1330       uschar * file;
1331
1332       while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1333         if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1334           return err;
1335       }
1336     else        /* would there ever be a need for multiple client certs? */
1337       if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1338         return err;
1339   }
1340
1341 #ifndef DISABLE_OCSP
1342 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1343   {
1344   /*XXX stack*/
1345   if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1346     return DEFER;
1347
1348   if (expanded && *expanded)
1349     {
1350     DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1351     if (  cbinfo->u_ocsp.server.file_expanded
1352        && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1353       {
1354       DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1355       }
1356     else
1357       ocsp_load_response(sctx, cbinfo, expanded);
1358     }
1359   }
1360 #endif
1361
1362 return OK;
1363 }
1364
1365
1366
1367
1368 /*************************************************
1369 *            Callback to handle SNI              *
1370 *************************************************/
1371
1372 /* Called when acting as server during the TLS session setup if a Server Name
1373 Indication extension was sent by the client.
1374
1375 API documentation is OpenSSL s_server.c implementation.
1376
1377 Arguments:
1378   s               SSL* of the current session
1379   ad              unknown (part of OpenSSL API) (unused)
1380   arg             Callback of "our" registered data
1381
1382 Returns:          SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1383 */
1384
1385 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1386 static int
1387 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1388 {
1389 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1390 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1391 int rc;
1392 int old_pool = store_pool;
1393 uschar * dummy_errstr;
1394
1395 if (!servername)
1396   return SSL_TLSEXT_ERR_OK;
1397
1398 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1399     reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1400
1401 /* Make the extension value available for expansion */
1402 store_pool = POOL_PERM;
1403 tls_in.sni = string_copy(US servername);
1404 store_pool = old_pool;
1405
1406 if (!reexpand_tls_files_for_sni)
1407   return SSL_TLSEXT_ERR_OK;
1408
1409 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1410 not confident that memcpy wouldn't break some internal reference counting.
1411 Especially since there's a references struct member, which would be off. */
1412
1413 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1414 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1415 #else
1416 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1417 #endif
1418   {
1419   ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1420   DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1421   goto bad;
1422   }
1423
1424 /* Not sure how many of these are actually needed, since SSL object
1425 already exists.  Might even need this selfsame callback, for reneg? */
1426
1427 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1428 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1429 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1430 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1431 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1432 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1433
1434 if (  !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1435    || !init_ecdh(server_sni, NULL, &dummy_errstr)
1436    )
1437   goto bad;
1438
1439 if (  cbinfo->server_cipher_list
1440    && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1441   goto bad;
1442
1443 #ifndef DISABLE_OCSP
1444 if (cbinfo->u_ocsp.server.file)
1445   {
1446   SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1447   SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1448   }
1449 #endif
1450
1451 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1452                       verify_callback_server, &dummy_errstr)) != OK)
1453   goto bad;
1454
1455 /* do this after setup_certs, because this can require the certs for verifying
1456 OCSP information. */
1457 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1458   goto bad;
1459
1460 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1461 SSL_set_SSL_CTX(s, server_sni);
1462 return SSL_TLSEXT_ERR_OK;
1463
1464 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1465 }
1466 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1467
1468
1469
1470
1471 #ifndef DISABLE_OCSP
1472
1473 /*************************************************
1474 *        Callback to handle OCSP Stapling        *
1475 *************************************************/
1476
1477 /* Called when acting as server during the TLS session setup if the client
1478 requests OCSP information with a Certificate Status Request.
1479
1480 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1481 project.
1482
1483 */
1484
1485 static int
1486 tls_server_stapling_cb(SSL *s, void *arg)
1487 {
1488 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1489 uschar *response_der;   /*XXX blob */
1490 int response_der_len;
1491
1492 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1493 out which ocsp blob to send.  Unfortunately, SSL_get_certificate is known
1494 buggy in current OpenSSL; it returns the last cert loaded always rather than
1495 the one actually presented.  So we can't support a stack of OCSP proofs at
1496 this time. */
1497
1498 DEBUG(D_tls)
1499   debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1500     cbinfo->u_ocsp.server.response ? "have" : "lack");
1501
1502 tls_in.ocsp = OCSP_NOT_RESP;
1503 if (!cbinfo->u_ocsp.server.response)
1504   return SSL_TLSEXT_ERR_NOACK;
1505
1506 response_der = NULL;
1507 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,    /*XXX stack*/
1508                       &response_der);
1509 if (response_der_len <= 0)
1510   return SSL_TLSEXT_ERR_NOACK;
1511
1512 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1513 tls_in.ocsp = OCSP_VFIED;
1514 return SSL_TLSEXT_ERR_OK;
1515 }
1516
1517
1518 static void
1519 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1520 {
1521 BIO_printf(bp, "\t%s: ", str);
1522 ASN1_GENERALIZEDTIME_print(bp, time);
1523 BIO_puts(bp, "\n");
1524 }
1525
1526 static int
1527 tls_client_stapling_cb(SSL *s, void *arg)
1528 {
1529 tls_ext_ctx_cb * cbinfo = arg;
1530 const unsigned char * p;
1531 int len;
1532 OCSP_RESPONSE * rsp;
1533 OCSP_BASICRESP * bs;
1534 int i;
1535
1536 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1537 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1538 if(!p)
1539  {
1540   /* Expect this when we requested ocsp but got none */
1541   if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1542     log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1543   else
1544     DEBUG(D_tls) debug_printf(" null\n");
1545   return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1546  }
1547
1548 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1549  {
1550   tls_out.ocsp = OCSP_FAILED;
1551   if (LOGGING(tls_cipher))
1552     log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1553   else
1554     DEBUG(D_tls) debug_printf(" parse error\n");
1555   return 0;
1556  }
1557
1558 if(!(bs = OCSP_response_get1_basic(rsp)))
1559   {
1560   tls_out.ocsp = OCSP_FAILED;
1561   if (LOGGING(tls_cipher))
1562     log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1563   else
1564     DEBUG(D_tls) debug_printf(" error parsing response\n");
1565   OCSP_RESPONSE_free(rsp);
1566   return 0;
1567   }
1568
1569 /* We'd check the nonce here if we'd put one in the request. */
1570 /* However that would defeat cacheability on the server so we don't. */
1571
1572 /* This section of code reworked from OpenSSL apps source;
1573    The OpenSSL Project retains copyright:
1574    Copyright (c) 1999 The OpenSSL Project.  All rights reserved.
1575 */
1576   {
1577     BIO * bp = NULL;
1578     int status, reason;
1579     ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1580
1581     DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1582
1583     /*OCSP_RESPONSE_print(bp, rsp, 0);   extreme debug: stapling content */
1584
1585     /* Use the chain that verified the server cert to verify the stapled info */
1586     /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1587
1588     if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1589               cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1590       {
1591       tls_out.ocsp = OCSP_FAILED;
1592       if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1593               "Received TLS cert status response, itself unverifiable: %s",
1594               ERR_reason_error_string(ERR_peek_error()));
1595       BIO_printf(bp, "OCSP response verify failure\n");
1596       ERR_print_errors(bp);
1597       OCSP_RESPONSE_print(bp, rsp, 0);
1598       goto failed;
1599       }
1600
1601     BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1602
1603     /*XXX So we have a good stapled OCSP status.  How do we know
1604     it is for the cert of interest?  OpenSSL 1.1.0 has a routine
1605     OCSP_resp_find_status() which matches on a cert id, which presumably
1606     we should use. Making an id needs OCSP_cert_id_new(), which takes
1607     issuerName, issuerKey, serialNumber.  Are they all in the cert?
1608
1609     For now, carry on blindly accepting the resp. */
1610
1611       {
1612       OCSP_SINGLERESP * single;
1613
1614 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1615       if (OCSP_resp_count(bs) != 1)
1616 #else
1617       STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1618       if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1619 #endif
1620         {
1621         tls_out.ocsp = OCSP_FAILED;
1622         log_write(0, LOG_MAIN, "OCSP stapling "
1623             "with multiple responses not handled");
1624         goto failed;
1625         }
1626       single = OCSP_resp_get0(bs, 0);
1627       status = OCSP_single_get0_status(single, &reason, &rev,
1628                   &thisupd, &nextupd);
1629       }
1630
1631     DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1632     DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1633     if (!OCSP_check_validity(thisupd, nextupd,
1634           EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1635       {
1636       tls_out.ocsp = OCSP_FAILED;
1637       DEBUG(D_tls) ERR_print_errors(bp);
1638       log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1639       }
1640     else
1641       {
1642       DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1643                     OCSP_cert_status_str(status));
1644       switch(status)
1645         {
1646         case V_OCSP_CERTSTATUS_GOOD:
1647           tls_out.ocsp = OCSP_VFIED;
1648           i = 1;
1649           goto good;
1650         case V_OCSP_CERTSTATUS_REVOKED:
1651           tls_out.ocsp = OCSP_FAILED;
1652           log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1653               reason != -1 ? "; reason: " : "",
1654               reason != -1 ? OCSP_crl_reason_str(reason) : "");
1655           DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1656           break;
1657         default:
1658           tls_out.ocsp = OCSP_FAILED;
1659           log_write(0, LOG_MAIN,
1660               "Server certificate status unknown, in OCSP stapling");
1661           break;
1662         }
1663       }
1664   failed:
1665     i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1666   good:
1667     BIO_free(bp);
1668   }
1669
1670 OCSP_RESPONSE_free(rsp);
1671 return i;
1672 }
1673 #endif  /*!DISABLE_OCSP*/
1674
1675
1676 /*************************************************
1677 *            Initialize for TLS                  *
1678 *************************************************/
1679
1680 /* Called from both server and client code, to do preliminary initialization
1681 of the library.  We allocate and return a context structure.
1682
1683 Arguments:
1684   ctxp            returned SSL context
1685   host            connected host, if client; NULL if server
1686   dhparam         DH parameter file
1687   certificate     certificate file
1688   privatekey      private key
1689   ocsp_file       file of stapling info (server); flag for require ocsp (client)
1690   addr            address if client; NULL if server (for some randomness)
1691   cbp             place to put allocated callback context
1692   errstr          error string pointer
1693
1694 Returns:          OK/DEFER/FAIL
1695 */
1696
1697 static int
1698 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1699   uschar *privatekey,
1700 #ifndef DISABLE_OCSP
1701   uschar *ocsp_file,    /*XXX stack, in server*/
1702 #endif
1703   address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1704 {
1705 SSL_CTX * ctx;
1706 long init_options;
1707 int rc;
1708 tls_ext_ctx_cb * cbinfo;
1709
1710 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1711 cbinfo->certificate = certificate;
1712 cbinfo->privatekey = privatekey;
1713 cbinfo->is_server = host==NULL;
1714 #ifndef DISABLE_OCSP
1715 cbinfo->verify_stack = NULL;
1716 if (!host)
1717   {
1718   cbinfo->u_ocsp.server.file = ocsp_file;
1719   cbinfo->u_ocsp.server.file_expanded = NULL;
1720   cbinfo->u_ocsp.server.response = NULL;
1721   }
1722 else
1723   cbinfo->u_ocsp.client.verify_store = NULL;
1724 #endif
1725 cbinfo->dhparam = dhparam;
1726 cbinfo->server_cipher_list = NULL;
1727 cbinfo->host = host;
1728 #ifndef DISABLE_EVENT
1729 cbinfo->event_action = NULL;
1730 #endif
1731
1732 #ifdef EXIM_NEED_OPENSSL_INIT
1733 SSL_load_error_strings();          /* basic set up */
1734 OpenSSL_add_ssl_algorithms();
1735 #endif
1736
1737 #ifdef EXIM_HAVE_SHA256
1738 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1739 list of available digests. */
1740 EVP_add_digest(EVP_sha256());
1741 #endif
1742
1743 /* Create a context.
1744 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1745 negotiation in the different methods; as far as I can tell, the only
1746 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1747 when OpenSSL is built without SSLv2 support.
1748 By disabling with openssl_options, we can let admins re-enable with the
1749 existing knob. */
1750
1751 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1752 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1753 #else
1754 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1755 #endif
1756   return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1757
1758 /* It turns out that we need to seed the random number generator this early in
1759 order to get the full complement of ciphers to work. It took me roughly a day
1760 of work to discover this by experiment.
1761
1762 On systems that have /dev/urandom, SSL may automatically seed itself from
1763 there. Otherwise, we have to make something up as best we can. Double check
1764 afterwards. */
1765
1766 if (!RAND_status())
1767   {
1768   randstuff r;
1769   gettimeofday(&r.tv, NULL);
1770   r.p = getpid();
1771
1772   RAND_seed(US (&r), sizeof(r));
1773   RAND_seed(US big_buffer, big_buffer_size);
1774   if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1775
1776   if (!RAND_status())
1777     return tls_error(US"RAND_status", host,
1778       US"unable to seed random number generator", errstr);
1779   }
1780
1781 /* Set up the information callback, which outputs if debugging is at a suitable
1782 level. */
1783
1784 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1785 #ifdef OPENSSL_HAVE_KEYLOG_CB
1786 DEBUG(D_tls) SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1787 #endif
1788
1789 /* Automatically re-try reads/writes after renegotiation. */
1790 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1791
1792 /* Apply administrator-supplied work-arounds.
1793 Historically we applied just one requested option,
1794 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1795 moved to an administrator-controlled list of options to specify and
1796 grandfathered in the first one as the default value for "openssl_options".
1797
1798 No OpenSSL version number checks: the options we accept depend upon the
1799 availability of the option value macros from OpenSSL.  */
1800
1801 if (!tls_openssl_options_parse(openssl_options, &init_options))
1802   return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1803
1804 if (init_options)
1805   {
1806   DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1807   if (!(SSL_CTX_set_options(ctx, init_options)))
1808     return tls_error(string_sprintf(
1809           "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1810   }
1811 else
1812   DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1813
1814 #ifdef OPENSSL_HAVE_NUM_TICKETS
1815 SSL_CTX_set_num_tickets(ctx, 0);        /* send no TLS1.3 stateful-tickets */
1816 #endif
1817
1818 /* We'd like to disable session cache unconditionally, but foolish Outlook
1819 Express clients then give up the first TLS connection and make a second one
1820 (which works).  Only when there is an IMAP service on the same machine.
1821 Presumably OE is trying to use the cache for A on B.  Leave it enabled for
1822 now, until we work out a decent way of presenting control to the config.  It
1823 will never be used because we use a new context every time. */
1824 #ifdef notdef
1825 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1826 #endif
1827
1828 /* Initialize with DH parameters if supplied */
1829 /* Initialize ECDH temp key parameter selection */
1830
1831 if (  !init_dh(ctx, dhparam, host, errstr)
1832    || !init_ecdh(ctx, host, errstr)
1833    )
1834   return DEFER;
1835
1836 /* Set up certificate and key (and perhaps OCSP info) */
1837
1838 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1839   return rc;
1840
1841 /* If we need to handle SNI or OCSP, do so */
1842
1843 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1844 # ifndef DISABLE_OCSP
1845   if (!(cbinfo->verify_stack = sk_X509_new_null()))
1846     {
1847     DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1848     return FAIL;
1849     }
1850 # endif
1851
1852 if (!host)              /* server */
1853   {
1854 # ifndef DISABLE_OCSP
1855   /* We check u_ocsp.server.file, not server.response, because we care about if
1856   the option exists, not what the current expansion might be, as SNI might
1857   change the certificate and OCSP file in use between now and the time the
1858   callback is invoked. */
1859   if (cbinfo->u_ocsp.server.file)
1860     {
1861     SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1862     SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1863     }
1864 # endif
1865   /* We always do this, so that $tls_sni is available even if not used in
1866   tls_certificate */
1867   SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1868   SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1869   }
1870 # ifndef DISABLE_OCSP
1871 else                    /* client */
1872   if(ocsp_file)         /* wanting stapling */
1873     {
1874     if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1875       {
1876       DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1877       return FAIL;
1878       }
1879     SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1880     SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1881     }
1882 # endif
1883 #endif
1884
1885 cbinfo->verify_cert_hostnames = NULL;
1886
1887 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1888 /* Set up the RSA callback */
1889 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1890 #endif
1891
1892 /* Finally, set the timeout, and we are done */
1893
1894 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1895 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1896
1897 *cbp = cbinfo;
1898 *ctxp = ctx;
1899
1900 return OK;
1901 }
1902
1903
1904
1905
1906 /*************************************************
1907 *           Get name of cipher in use            *
1908 *************************************************/
1909
1910 /*
1911 Argument:   pointer to an SSL structure for the connection
1912             buffer to use for answer
1913             size of buffer
1914             pointer to number of bits for cipher
1915 Returns:    nothing
1916 */
1917
1918 static void
1919 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1920 {
1921 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
1922 yet reflect that.  It should be a safe change anyway, even 0.9.8 versions have
1923 the accessor functions use const in the prototype. */
1924
1925 const uschar * ver = CUS SSL_get_version(ssl);
1926 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1927
1928 SSL_CIPHER_get_bits(c, bits);
1929
1930 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1931   SSL_CIPHER_get_name(c), *bits);
1932
1933 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1934 }
1935
1936
1937 static void
1938 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
1939 {
1940 /*XXX we might consider a list-of-certs variable for the cert chain.
1941 SSL_get_peer_cert_chain(SSL*).  We'd need a new variable type and support
1942 in list-handling functions, also consider the difference between the entire
1943 chain and the elements sent by the peer. */
1944
1945 tlsp->peerdn = NULL;
1946
1947 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1948 if (!tlsp->peercert)
1949   tlsp->peercert = SSL_get_peer_certificate(ssl);
1950 /* Beware anonymous ciphers which lead to server_cert being NULL */
1951 if (tlsp->peercert)
1952   if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
1953     { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
1954   else
1955     {
1956     peerdn[siz-1] = '\0';
1957     tlsp->peerdn = peerdn;              /*XXX a static buffer... */
1958     }
1959 }
1960
1961
1962
1963
1964
1965 /*************************************************
1966 *        Set up for verifying certificates       *
1967 *************************************************/
1968
1969 #ifndef DISABLE_OCSP
1970 /* Load certs from file, return TRUE on success */
1971
1972 static BOOL
1973 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1974 {
1975 BIO * bp;
1976 X509 * x;
1977
1978 while (sk_X509_num(verify_stack) > 0)
1979   X509_free(sk_X509_pop(verify_stack));
1980
1981 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1982 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1983   sk_X509_push(verify_stack, x);
1984 BIO_free(bp);
1985 return TRUE;
1986 }
1987 #endif
1988
1989
1990
1991 /* Called by both client and server startup; on the server possibly
1992 repeated after a Server Name Indication.
1993
1994 Arguments:
1995   sctx          SSL_CTX* to initialise
1996   certs         certs file or NULL
1997   crl           CRL file or NULL
1998   host          NULL in a server; the remote host in a client
1999   optional      TRUE if called from a server for a host in tls_try_verify_hosts;
2000                 otherwise passed as FALSE
2001   cert_vfy_cb   Callback function for certificate verification
2002   errstr        error string pointer
2003
2004 Returns:        OK/DEFER/FAIL
2005 */
2006
2007 static int
2008 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2009     int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2010 {
2011 uschar *expcerts, *expcrl;
2012
2013 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2014   return DEFER;
2015 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2016
2017 if (expcerts && *expcerts)
2018   {
2019   /* Tell the library to use its compiled-in location for the system default
2020   CA bundle. Then add the ones specified in the config, if any. */
2021
2022   if (!SSL_CTX_set_default_verify_paths(sctx))
2023     return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2024
2025   if (Ustrcmp(expcerts, "system") != 0)
2026     {
2027     struct stat statbuf;
2028
2029     if (Ustat(expcerts, &statbuf) < 0)
2030       {
2031       log_write(0, LOG_MAIN|LOG_PANIC,
2032         "failed to stat %s for certificates", expcerts);
2033       return DEFER;
2034       }
2035     else
2036       {
2037       uschar *file, *dir;
2038       if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2039         { file = NULL; dir = expcerts; }
2040       else
2041         {
2042         file = expcerts; dir = NULL;
2043 #ifndef DISABLE_OCSP
2044         /* In the server if we will be offering an OCSP proof, load chain from
2045         file for verifying the OCSP proof at load time. */
2046
2047         if (  !host
2048            && statbuf.st_size > 0
2049            && server_static_cbinfo->u_ocsp.server.file
2050            && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2051            )
2052           {
2053           log_write(0, LOG_MAIN|LOG_PANIC,
2054             "failed to load cert chain from %s", file);
2055           return DEFER;
2056           }
2057 #endif
2058         }
2059
2060       /* If a certificate file is empty, the next function fails with an
2061       unhelpful error message. If we skip it, we get the correct behaviour (no
2062       certificates are recognized, but the error message is still misleading (it
2063       says no certificate was supplied).  But this is better. */
2064
2065       if (  (!file || statbuf.st_size > 0)
2066          && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2067         return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2068
2069       /* Load the list of CAs for which we will accept certs, for sending
2070       to the client.  This is only for the one-file tls_verify_certificates
2071       variant.
2072       If a list isn't loaded into the server, but some verify locations are set,
2073       the server end appears to make a wildcard request for client certs.
2074       Meanwhile, the client library as default behaviour *ignores* the list
2075       we send over the wire - see man SSL_CTX_set_client_cert_cb.
2076       Because of this, and that the dir variant is likely only used for
2077       the public-CA bundle (not for a private CA), not worth fixing.  */
2078
2079       if (file)
2080         {
2081         STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2082
2083         SSL_CTX_set_client_CA_list(sctx, names);
2084         DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2085                                     sk_X509_NAME_num(names));
2086         }
2087       }
2088     }
2089
2090   /* Handle a certificate revocation list. */
2091
2092 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2093
2094   /* This bit of code is now the version supplied by Lars Mainka. (I have
2095   merely reformatted it into the Exim code style.)
2096
2097   "From here I changed the code to add support for multiple crl's
2098   in pem format in one file or to support hashed directory entries in
2099   pem format instead of a file. This method now uses the library function
2100   X509_STORE_load_locations to add the CRL location to the SSL context.
2101   OpenSSL will then handle the verify against CA certs and CRLs by
2102   itself in the verify callback." */
2103
2104   if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2105   if (expcrl && *expcrl)
2106     {
2107     struct stat statbufcrl;
2108     if (Ustat(expcrl, &statbufcrl) < 0)
2109       {
2110       log_write(0, LOG_MAIN|LOG_PANIC,
2111         "failed to stat %s for certificates revocation lists", expcrl);
2112       return DEFER;
2113       }
2114     else
2115       {
2116       /* is it a file or directory? */
2117       uschar *file, *dir;
2118       X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2119       if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2120         {
2121         file = NULL;
2122         dir = expcrl;
2123         DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2124         }
2125       else
2126         {
2127         file = expcrl;
2128         dir = NULL;
2129         DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2130         }
2131       if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2132         return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2133
2134       /* setting the flags to check against the complete crl chain */
2135
2136       X509_STORE_set_flags(cvstore,
2137         X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2138       }
2139     }
2140
2141 #endif  /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2142
2143   /* If verification is optional, don't fail if no certificate */
2144
2145   SSL_CTX_set_verify(sctx,
2146     SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2147     cert_vfy_cb);
2148   }
2149
2150 return OK;
2151 }
2152
2153
2154
2155 /*************************************************
2156 *       Start a TLS session in a server          *
2157 *************************************************/
2158
2159 /* This is called when Exim is running as a server, after having received
2160 the STARTTLS command. It must respond to that command, and then negotiate
2161 a TLS session.
2162
2163 Arguments:
2164   require_ciphers   allowed ciphers
2165   errstr            pointer to error message
2166
2167 Returns:            OK on success
2168                     DEFER for errors before the start of the negotiation
2169                     FAIL for errors during the negotiation; the server can't
2170                       continue running.
2171 */
2172
2173 int
2174 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2175 {
2176 int rc;
2177 uschar * expciphers;
2178 tls_ext_ctx_cb * cbinfo;
2179 static uschar peerdn[256];
2180 static uschar cipherbuf[256];
2181
2182 /* Check for previous activation */
2183
2184 if (tls_in.active.sock >= 0)
2185   {
2186   tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2187   smtp_printf("554 Already in TLS\r\n", FALSE);
2188   return FAIL;
2189   }
2190
2191 /* Initialize the SSL library. If it fails, it will already have logged
2192 the error. */
2193
2194 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2195 #ifndef DISABLE_OCSP
2196     tls_ocsp_file,      /*XXX stack*/
2197 #endif
2198     NULL, &server_static_cbinfo, errstr);
2199 if (rc != OK) return rc;
2200 cbinfo = server_static_cbinfo;
2201
2202 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2203   return FAIL;
2204
2205 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2206 were historically separated by underscores. So that I can use either form in my
2207 tests, and also for general convenience, we turn underscores into hyphens here.
2208
2209 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2210 for TLS 1.3 .  Since we do not call it at present we get the default list:
2211 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2212 */
2213
2214 if (expciphers)
2215   {
2216   uschar * s = expciphers;
2217   while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2218   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2219   if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2220     return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2221   cbinfo->server_cipher_list = expciphers;
2222   }
2223
2224 /* If this is a host for which certificate verification is mandatory or
2225 optional, set up appropriately. */
2226
2227 tls_in.certificate_verified = FALSE;
2228 #ifdef SUPPORT_DANE
2229 tls_in.dane_verified = FALSE;
2230 #endif
2231 server_verify_callback_called = FALSE;
2232
2233 if (verify_check_host(&tls_verify_hosts) == OK)
2234   {
2235   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2236                         FALSE, verify_callback_server, errstr);
2237   if (rc != OK) return rc;
2238   server_verify_optional = FALSE;
2239   }
2240 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2241   {
2242   rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2243                         TRUE, verify_callback_server, errstr);
2244   if (rc != OK) return rc;
2245   server_verify_optional = TRUE;
2246   }
2247
2248 /* Prepare for new connection */
2249
2250 if (!(server_ssl = SSL_new(server_ctx)))
2251   return tls_error(US"SSL_new", NULL, NULL, errstr);
2252
2253 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2254  *
2255  * With the SSL_clear(), we get strange interoperability bugs with
2256  * OpenSSL 1.0.1b and TLS1.1/1.2.  It looks as though this may be a bug in
2257  * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2258  *
2259  * The SSL_clear() call is to let an existing SSL* be reused, typically after
2260  * session shutdown.  In this case, we have a brand new object and there's no
2261  * obvious reason to immediately clear it.  I'm guessing that this was
2262  * originally added because of incomplete initialisation which the clear fixed,
2263  * in some historic release.
2264  */
2265
2266 /* Set context and tell client to go ahead, except in the case of TLS startup
2267 on connection, where outputting anything now upsets the clients and tends to
2268 make them disconnect. We need to have an explicit fflush() here, to force out
2269 the response. Other smtp_printf() calls do not need it, because in non-TLS
2270 mode, the fflush() happens when smtp_getc() is called. */
2271
2272 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2273 if (!tls_in.on_connect)
2274   {
2275   smtp_printf("220 TLS go ahead\r\n", FALSE);
2276   fflush(smtp_out);
2277   }
2278
2279 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2280 that the OpenSSL library doesn't. */
2281
2282 SSL_set_wfd(server_ssl, fileno(smtp_out));
2283 SSL_set_rfd(server_ssl, fileno(smtp_in));
2284 SSL_set_accept_state(server_ssl);
2285
2286 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2287
2288 sigalrm_seen = FALSE;
2289 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2290 rc = SSL_accept(server_ssl);
2291 ALARM_CLR(0);
2292
2293 if (rc <= 0)
2294   {
2295   (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2296   return FAIL;
2297   }
2298
2299 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2300 ERR_clear_error();      /* Even success can leave errors in the stack. Seen with
2301                         anon-authentication ciphersuite negociated. */
2302
2303 /* TLS has been set up. Adjust the input functions to read via TLS,
2304 and initialize things. */
2305
2306 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2307
2308 DEBUG(D_tls)
2309   {
2310   uschar buf[2048];
2311   if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2312     debug_printf("Shared ciphers: %s\n", buf);
2313
2314 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2315   {
2316   BIO * bp = BIO_new(BIO_s_mem());
2317   uschar * s;
2318   int len;
2319   SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2320   len = (int) BIO_get_mem_data(bp, CSS &s);
2321   debug_printf("%.*s", len, s);
2322   BIO_free(bp);
2323   }
2324 #endif
2325   }
2326
2327 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2328 tls_in.cipher = cipherbuf;
2329
2330 /* Record the certificate we presented */
2331   {
2332   X509 * crt = SSL_get_certificate(server_ssl);
2333   tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2334   }
2335
2336 /* Only used by the server-side tls (tls_in), including tls_getc.
2337    Client-side (tls_out) reads (seem to?) go via
2338    smtp_read_response()/ip_recv().
2339    Hence no need to duplicate for _in and _out.
2340  */
2341 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2342 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2343 ssl_xfer_eof = ssl_xfer_error = FALSE;
2344
2345 receive_getc = tls_getc;
2346 receive_getbuf = tls_getbuf;
2347 receive_get_cache = tls_get_cache;
2348 receive_ungetc = tls_ungetc;
2349 receive_feof = tls_feof;
2350 receive_ferror = tls_ferror;
2351 receive_smtp_buffered = tls_smtp_buffered;
2352
2353 tls_in.active.sock = fileno(smtp_out);
2354 tls_in.active.tls_ctx = NULL;   /* not using explicit ctx for server-side */
2355 return OK;
2356 }
2357
2358
2359
2360
2361 static int
2362 tls_client_basic_ctx_init(SSL_CTX * ctx,
2363     host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2364     uschar ** errstr)
2365 {
2366 int rc;
2367 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2368    set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2369    the specified host patterns if one of them is defined */
2370
2371 if (  (  !ob->tls_verify_hosts
2372       && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2373       )
2374    || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2375    )
2376   client_verify_optional = FALSE;
2377 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2378   client_verify_optional = TRUE;
2379 else
2380   return OK;
2381
2382 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2383       ob->tls_crl, host, client_verify_optional, verify_callback_client,
2384       errstr)) != OK)
2385   return rc;
2386
2387 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2388   {
2389   cbinfo->verify_cert_hostnames =
2390 #ifdef SUPPORT_I18N
2391     string_domain_utf8_to_alabel(host->name, NULL);
2392 #else
2393     host->name;
2394 #endif
2395   DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2396                     cbinfo->verify_cert_hostnames);
2397   }
2398 return OK;
2399 }
2400
2401
2402 #ifdef SUPPORT_DANE
2403 static int
2404 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2405 {
2406 dns_scan dnss;
2407 const char * hostnames[2] = { CS host->name, NULL };
2408 int found = 0;
2409
2410 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2411   return tls_error(US"hostnames load", host, NULL, errstr);
2412
2413 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2414      rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2415     ) if (rr->type == T_TLSA && rr->size > 3)
2416   {
2417   const uschar * p = rr->data;
2418   uint8_t usage, selector, mtype;
2419   const char * mdname;
2420
2421   usage = *p++;
2422
2423   /* Only DANE-TA(2) and DANE-EE(3) are supported */
2424   if (usage != 2 && usage != 3) continue;
2425
2426   selector = *p++;
2427   mtype = *p++;
2428
2429   switch (mtype)
2430     {
2431     default: continue;  /* Only match-types 0, 1, 2 are supported */
2432     case 0:  mdname = NULL; break;
2433     case 1:  mdname = "sha256"; break;
2434     case 2:  mdname = "sha512"; break;
2435     }
2436
2437   found++;
2438   switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2439     {
2440     default:
2441       return tls_error(US"tlsa load", host, NULL, errstr);
2442     case 0:     /* action not taken */
2443     case 1:     break;
2444     }
2445
2446   tls_out.tlsa_usage |= 1<<usage;
2447   }
2448
2449 if (found)
2450   return OK;
2451
2452 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2453 return DEFER;
2454 }
2455 #endif  /*SUPPORT_DANE*/
2456
2457
2458
2459 /*************************************************
2460 *    Start a TLS session in a client             *
2461 *************************************************/
2462
2463 /* Called from the smtp transport after STARTTLS has been accepted.
2464
2465 Argument:
2466   fd               the fd of the connection
2467   host             connected host (for messages and option-tests)
2468   addr             the first address (for some randomness; can be NULL)
2469   tb               transport (always smtp)
2470   tlsa_dnsa        tlsa lookup, if DANE, else null
2471   tlsp             record details of channel configuration here; must be non-NULL
2472   errstr           error string pointer
2473
2474 Returns:           Pointer to TLS session context, or NULL on error
2475 */
2476
2477 void *
2478 tls_client_start(int fd, host_item *host, address_item *addr,
2479   transport_instance * tb,
2480 #ifdef SUPPORT_DANE
2481   dns_answer * tlsa_dnsa,
2482 #endif
2483   tls_support * tlsp, uschar ** errstr)
2484 {
2485 smtp_transport_options_block * ob = tb
2486   ? (smtp_transport_options_block *)tb->options_block
2487   : &smtp_transport_option_defaults;
2488 exim_openssl_client_tls_ctx * exim_client_ctx;
2489 static uschar peerdn[256];
2490 uschar * expciphers;
2491 int rc;
2492 static uschar cipherbuf[256];
2493
2494 #ifndef DISABLE_OCSP
2495 BOOL request_ocsp = FALSE;
2496 BOOL require_ocsp = FALSE;
2497 #endif
2498
2499 rc = store_pool;
2500 store_pool = POOL_PERM;
2501 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx));
2502 store_pool = rc;
2503
2504 #ifdef SUPPORT_DANE
2505 tlsp->tlsa_usage = 0;
2506 #endif
2507
2508 #ifndef DISABLE_OCSP
2509   {
2510 # ifdef SUPPORT_DANE
2511   if (  tlsa_dnsa
2512      && ob->hosts_request_ocsp[0] == '*'
2513      && ob->hosts_request_ocsp[1] == '\0'
2514      )
2515     {
2516     /* Unchanged from default.  Use a safer one under DANE */
2517     request_ocsp = TRUE;
2518     ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2519                                       "   {= {4}{$tls_out_tlsa_usage}} } "
2520                                  " {*}{}}";
2521     }
2522 # endif
2523
2524   if ((require_ocsp =
2525         verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2526     request_ocsp = TRUE;
2527   else
2528 # ifdef SUPPORT_DANE
2529     if (!request_ocsp)
2530 # endif
2531       request_ocsp =
2532         verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2533   }
2534 #endif
2535
2536 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2537     ob->tls_certificate, ob->tls_privatekey,
2538 #ifndef DISABLE_OCSP
2539     (void *)(long)request_ocsp,
2540 #endif
2541     addr, &client_static_cbinfo, errstr);
2542 if (rc != OK) return NULL;
2543
2544 tlsp->certificate_verified = FALSE;
2545 client_verify_callback_called = FALSE;
2546
2547 expciphers = NULL;
2548 #ifdef SUPPORT_DANE
2549 if (tlsa_dnsa)
2550   {
2551   /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2552   other failures should be treated as problems. */
2553   if (ob->dane_require_tls_ciphers &&
2554       !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2555         &expciphers, errstr))
2556     return NULL;
2557   if (expciphers && *expciphers == '\0')
2558     expciphers = NULL;
2559   }
2560 #endif
2561 if (!expciphers &&
2562     !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2563       &expciphers, errstr))
2564   return NULL;
2565
2566 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2567 are separated by underscores. So that I can use either form in my tests, and
2568 also for general convenience, we turn underscores into hyphens here. */
2569
2570 if (expciphers)
2571   {
2572   uschar *s = expciphers;
2573   while (*s) { if (*s == '_') *s = '-'; s++; }
2574   DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2575   if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2576     {
2577     tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2578     return NULL;
2579     }
2580   }
2581
2582 #ifdef SUPPORT_DANE
2583 if (tlsa_dnsa)
2584   {
2585   SSL_CTX_set_verify(exim_client_ctx->ctx,
2586     SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2587     verify_callback_client_dane);
2588
2589   if (!DANESSL_library_init())
2590     {
2591     tls_error(US"library init", host, NULL, errstr);
2592     return NULL;
2593     }
2594   if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
2595     {
2596     tls_error(US"context init", host, NULL, errstr);
2597     return NULL;
2598     }
2599   }
2600 else
2601
2602 #endif
2603
2604   if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
2605         client_static_cbinfo, errstr) != OK)
2606     return NULL;
2607
2608 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
2609   {
2610   tls_error(US"SSL_new", host, NULL, errstr);
2611   return NULL;
2612   }
2613 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
2614 SSL_set_fd(exim_client_ctx->ssl, fd);
2615 SSL_set_connect_state(exim_client_ctx->ssl);
2616
2617 if (ob->tls_sni)
2618   {
2619   if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
2620     return NULL;
2621   if (!tlsp->sni)
2622     {
2623     DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2624     }
2625   else if (!Ustrlen(tlsp->sni))
2626     tlsp->sni = NULL;
2627   else
2628     {
2629 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2630     DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
2631     SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
2632 #else
2633     log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2634           tlsp->sni);
2635 #endif
2636     }
2637   }
2638
2639 #ifdef SUPPORT_DANE
2640 if (tlsa_dnsa)
2641   if (dane_tlsa_load(exim_client_ctx->ssl, host, tlsa_dnsa, errstr) != OK)
2642     return NULL;
2643 #endif
2644
2645 #ifndef DISABLE_OCSP
2646 /* Request certificate status at connection-time.  If the server
2647 does OCSP stapling we will get the callback (set in tls_init()) */
2648 # ifdef SUPPORT_DANE
2649 if (request_ocsp)
2650   {
2651   const uschar * s;
2652   if (  ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2653      || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2654      )
2655     {   /* Re-eval now $tls_out_tlsa_usage is populated.  If
2656         this means we avoid the OCSP request, we wasted the setup
2657         cost in tls_init(). */
2658     require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2659     request_ocsp = require_ocsp
2660       || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2661     }
2662   }
2663 # endif
2664
2665 if (request_ocsp)
2666   {
2667   SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
2668   client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2669   tlsp->ocsp = OCSP_NOT_RESP;
2670   }
2671 #endif
2672
2673 #ifndef DISABLE_EVENT
2674 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
2675 #endif
2676
2677 /* There doesn't seem to be a built-in timeout on connection. */
2678
2679 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2680 sigalrm_seen = FALSE;
2681 ALARM(ob->command_timeout);
2682 rc = SSL_connect(exim_client_ctx->ssl);
2683 ALARM_CLR(0);
2684
2685 #ifdef SUPPORT_DANE
2686 if (tlsa_dnsa)
2687   DANESSL_cleanup(exim_client_ctx->ssl);
2688 #endif
2689
2690 if (rc <= 0)
2691   {
2692   tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
2693   return NULL;
2694   }
2695
2696 DEBUG(D_tls)
2697   {
2698   debug_printf("SSL_connect succeeded\n");
2699 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2700   {
2701   BIO * bp = BIO_new(BIO_s_mem());
2702   uschar * s;
2703   int len;
2704   SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2705   len = (int) BIO_get_mem_data(bp, CSS &s);
2706   debug_printf("%.*s", len, s);
2707   BIO_free(bp);
2708   }
2709 #endif
2710   }
2711
2712 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
2713
2714 construct_cipher_name(exim_client_ctx->ssl, cipherbuf, sizeof(cipherbuf), &tlsp->bits);
2715 tlsp->cipher = cipherbuf;
2716
2717 /* Record the certificate we presented */
2718   {
2719   X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
2720   tlsp->ourcert = crt ? X509_dup(crt) : NULL;
2721   }
2722
2723 tlsp->active.sock = fd;
2724 tlsp->active.tls_ctx = exim_client_ctx;
2725 return exim_client_ctx;
2726 }
2727
2728
2729
2730
2731
2732 static BOOL
2733 tls_refill(unsigned lim)
2734 {
2735 int error;
2736 int inbytes;
2737
2738 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2739   ssl_xfer_buffer, ssl_xfer_buffer_size);
2740
2741 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2742 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2743                   MIN(ssl_xfer_buffer_size, lim));
2744 error = SSL_get_error(server_ssl, inbytes);
2745 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2746
2747 if (had_command_timeout)                /* set by signal handler */
2748   smtp_command_timeout_exit();          /* does not return */
2749 if (had_command_sigterm)
2750   smtp_command_sigterm_exit();
2751 if (had_data_timeout)
2752   smtp_data_timeout_exit();
2753 if (had_data_sigint)
2754   smtp_data_sigint_exit();
2755
2756 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2757 closed down, not that the socket itself has been closed down. Revert to
2758 non-SSL handling. */
2759
2760 switch(error)
2761   {
2762   case SSL_ERROR_NONE:
2763     break;
2764
2765   case SSL_ERROR_ZERO_RETURN:
2766     DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2767
2768     receive_getc = smtp_getc;
2769     receive_getbuf = smtp_getbuf;
2770     receive_get_cache = smtp_get_cache;
2771     receive_ungetc = smtp_ungetc;
2772     receive_feof = smtp_feof;
2773     receive_ferror = smtp_ferror;
2774     receive_smtp_buffered = smtp_buffered;
2775
2776     if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2777           SSL_shutdown(server_ssl);
2778
2779 #ifndef DISABLE_OCSP
2780     sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
2781     server_static_cbinfo->verify_stack = NULL;
2782 #endif
2783     SSL_free(server_ssl);
2784     SSL_CTX_free(server_ctx);
2785     server_ctx = NULL;
2786     server_ssl = NULL;
2787     tls_in.active.sock = -1;
2788     tls_in.active.tls_ctx = NULL;
2789     tls_in.bits = 0;
2790     tls_in.cipher = NULL;
2791     tls_in.peerdn = NULL;
2792     tls_in.sni = NULL;
2793
2794     return FALSE;
2795
2796   /* Handle genuine errors */
2797   case SSL_ERROR_SSL:
2798     ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2799     log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2800     ssl_xfer_error = TRUE;
2801     return FALSE;
2802
2803   default:
2804     DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2805     DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
2806       debug_printf(" - syscall %s\n", strerror(errno));
2807     ssl_xfer_error = TRUE;
2808     return FALSE;
2809   }
2810
2811 #ifndef DISABLE_DKIM
2812 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2813 #endif
2814 ssl_xfer_buffer_hwm = inbytes;
2815 ssl_xfer_buffer_lwm = 0;
2816 return TRUE;
2817 }
2818
2819
2820 /*************************************************
2821 *            TLS version of getc                 *
2822 *************************************************/
2823
2824 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2825 it refills the buffer via the SSL reading function.
2826
2827 Arguments:  lim         Maximum amount to read/buffer
2828 Returns:    the next character or EOF
2829
2830 Only used by the server-side TLS.
2831 */
2832
2833 int
2834 tls_getc(unsigned lim)
2835 {
2836 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2837   if (!tls_refill(lim))
2838     return ssl_xfer_error ? EOF : smtp_getc(lim);
2839
2840 /* Something in the buffer; return next uschar */
2841
2842 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2843 }
2844
2845 uschar *
2846 tls_getbuf(unsigned * len)
2847 {
2848 unsigned size;
2849 uschar * buf;
2850
2851 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2852   if (!tls_refill(*len))
2853     {
2854     if (!ssl_xfer_error) return smtp_getbuf(len);
2855     *len = 0;
2856     return NULL;
2857     }
2858
2859 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2860   size = *len;
2861 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2862 ssl_xfer_buffer_lwm += size;
2863 *len = size;
2864 return buf;
2865 }
2866
2867
2868 void
2869 tls_get_cache()
2870 {
2871 #ifndef DISABLE_DKIM
2872 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2873 if (n > 0)
2874   dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2875 #endif
2876 }
2877
2878
2879 BOOL
2880 tls_could_read(void)
2881 {
2882 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2883 }
2884
2885
2886 /*************************************************
2887 *          Read bytes from TLS channel           *
2888 *************************************************/
2889
2890 /*
2891 Arguments:
2892   ct_ctx    client context pointer, or NULL for the one global server context
2893   buff      buffer of data
2894   len       size of buffer
2895
2896 Returns:    the number of bytes read
2897             -1 after a failed read, including EOF
2898
2899 Only used by the client-side TLS.
2900 */
2901
2902 int
2903 tls_read(void * ct_ctx, uschar *buff, size_t len)
2904 {
2905 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2906 int inbytes;
2907 int error;
2908
2909 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2910   buff, (unsigned int)len);
2911
2912 inbytes = SSL_read(ssl, CS buff, len);
2913 error = SSL_get_error(ssl, inbytes);
2914
2915 if (error == SSL_ERROR_ZERO_RETURN)
2916   {
2917   DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2918   return -1;
2919   }
2920 else if (error != SSL_ERROR_NONE)
2921   return -1;
2922
2923 return inbytes;
2924 }
2925
2926
2927
2928
2929
2930 /*************************************************
2931 *         Write bytes down TLS channel           *
2932 *************************************************/
2933
2934 /*
2935 Arguments:
2936   ct_ctx    client context pointer, or NULL for the one global server context
2937   buff      buffer of data
2938   len       number of bytes
2939   more      further data expected soon
2940
2941 Returns:    the number of bytes after a successful write,
2942             -1 after a failed write
2943
2944 Used by both server-side and client-side TLS.
2945 */
2946
2947 int
2948 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
2949 {
2950 size_t olen = len;
2951 int outbytes, error;
2952 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2953 static gstring * corked = NULL;
2954
2955 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2956   buff, (unsigned long)len, more ? ", more" : "");
2957
2958 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2959 "more" is notified.  This hack is only ok if small amounts are involved AND only
2960 one stream does it, in one context (i.e. no store reset).  Currently it is used
2961 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2962 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
2963 a store reset there, so use POOL_PERM. */
2964 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
2965
2966 if ((more || corked))
2967   {
2968 #ifdef EXPERIMENTAL_PIPE_CONNECT
2969   int save_pool = store_pool;
2970   store_pool = POOL_PERM;
2971 #endif
2972
2973   corked = string_catn(corked, buff, len);
2974
2975 #ifdef EXPERIMENTAL_PIPE_CONNECT
2976   store_pool = save_pool;
2977 #endif
2978
2979   if (more)
2980     return len;
2981   buff = CUS corked->s;
2982   len = corked->ptr;
2983   corked = NULL;
2984   }
2985
2986 for (int left = len; left > 0;)
2987   {
2988   DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
2989   outbytes = SSL_write(ssl, CS buff, left);
2990   error = SSL_get_error(ssl, outbytes);
2991   DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2992   switch (error)
2993     {
2994     case SSL_ERROR_SSL:
2995       ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2996       log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2997       return -1;
2998
2999     case SSL_ERROR_NONE:
3000       left -= outbytes;
3001       buff += outbytes;
3002       break;
3003
3004     case SSL_ERROR_ZERO_RETURN:
3005       log_write(0, LOG_MAIN, "SSL channel closed on write");
3006       return -1;
3007
3008     case SSL_ERROR_SYSCALL:
3009       log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3010         sender_fullhost ? sender_fullhost : US"<unknown>",
3011         strerror(errno));
3012       return -1;
3013
3014     default:
3015       log_write(0, LOG_MAIN, "SSL_write error %d", error);
3016       return -1;
3017     }
3018   }
3019 return olen;
3020 }
3021
3022
3023
3024 /*************************************************
3025 *         Close down a TLS session               *
3026 *************************************************/
3027
3028 /* This is also called from within a delivery subprocess forked from the
3029 daemon, to shut down the TLS library, without actually doing a shutdown (which
3030 would tamper with the SSL session in the parent process).
3031
3032 Arguments:
3033   ct_ctx        client TLS context pointer, or NULL for the one global server context
3034   shutdown      1 if TLS close-alert is to be sent,
3035                 2 if also response to be waited for
3036
3037 Returns:     nothing
3038
3039 Used by both server-side and client-side TLS.
3040 */
3041
3042 void
3043 tls_close(void * ct_ctx, int shutdown)
3044 {
3045 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3046 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3047 SSL **sslp =     o_ctx ? &o_ctx->ssl : &server_ssl;
3048 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3049
3050 if (*fdp < 0) return;  /* TLS was not active */
3051
3052 if (shutdown)
3053   {
3054   int rc;
3055   DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3056     shutdown > 1 ? " (with response-wait)" : "");
3057
3058   if (  (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3059      && shutdown > 1)
3060     {
3061     ALARM(2);
3062     rc = SSL_shutdown(*sslp);           /* wait for response */
3063     ALARM_CLR(0);
3064     }
3065
3066   if (rc < 0) DEBUG(D_tls)
3067     {
3068     ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3069     debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3070     }
3071   }
3072
3073 #ifndef DISABLE_OCSP
3074 if (!o_ctx)             /* server side */
3075   {
3076   sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3077   server_static_cbinfo->verify_stack = NULL;
3078   }
3079 #endif
3080
3081 SSL_CTX_free(*ctxp);
3082 SSL_free(*sslp);
3083 *ctxp = NULL;
3084 *sslp = NULL;
3085 *fdp = -1;
3086 }
3087
3088
3089
3090
3091 /*************************************************
3092 *  Let tls_require_ciphers be checked at startup *
3093 *************************************************/
3094
3095 /* The tls_require_ciphers option, if set, must be something which the
3096 library can parse.
3097
3098 Returns:     NULL on success, or error message
3099 */
3100
3101 uschar *
3102 tls_validate_require_cipher(void)
3103 {
3104 SSL_CTX *ctx;
3105 uschar *s, *expciphers, *err;
3106
3107 /* this duplicates from tls_init(), we need a better "init just global
3108 state, for no specific purpose" singleton function of our own */
3109
3110 #ifdef EXIM_NEED_OPENSSL_INIT
3111 SSL_load_error_strings();
3112 OpenSSL_add_ssl_algorithms();
3113 #endif
3114 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
3115 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
3116 list of available digests. */
3117 EVP_add_digest(EVP_sha256());
3118 #endif
3119
3120 if (!(tls_require_ciphers && *tls_require_ciphers))
3121   return NULL;
3122
3123 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3124                   &err))
3125   return US"failed to expand tls_require_ciphers";
3126
3127 if (!(expciphers && *expciphers))
3128   return NULL;
3129
3130 /* normalisation ripped from above */
3131 s = expciphers;
3132 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3133
3134 err = NULL;
3135
3136 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3137 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3138 #else
3139 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3140 #endif
3141   {
3142   ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3143   return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3144   }
3145
3146 DEBUG(D_tls)
3147   debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3148
3149 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3150   {
3151   ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3152   err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3153                       expciphers, ssl_errstring);
3154   }
3155
3156 SSL_CTX_free(ctx);
3157
3158 return err;
3159 }
3160
3161
3162
3163
3164 /*************************************************
3165 *         Report the library versions.           *
3166 *************************************************/
3167
3168 /* There have historically been some issues with binary compatibility in
3169 OpenSSL libraries; if Exim (like many other applications) is built against
3170 one version of OpenSSL but the run-time linker picks up another version,
3171 it can result in serious failures, including crashing with a SIGSEGV.  So
3172 report the version found by the compiler and the run-time version.
3173
3174 Note: some OS vendors backport security fixes without changing the version
3175 number/string, and the version date remains unchanged.  The _build_ date
3176 will change, so we can more usefully assist with version diagnosis by also
3177 reporting the build date.
3178
3179 Arguments:   a FILE* to print the results to
3180 Returns:     nothing
3181 */
3182
3183 void
3184 tls_version_report(FILE *f)
3185 {
3186 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3187            "                          Runtime: %s\n"
3188            "                                 : %s\n",
3189            OPENSSL_VERSION_TEXT,
3190            SSLeay_version(SSLEAY_VERSION),
3191            SSLeay_version(SSLEAY_BUILT_ON));
3192 /* third line is 38 characters for the %s and the line is 73 chars long;
3193 the OpenSSL output includes a "built on: " prefix already. */
3194 }
3195
3196
3197
3198
3199 /*************************************************
3200 *            Random number generation            *
3201 *************************************************/
3202
3203 /* Pseudo-random number generation.  The result is not expected to be
3204 cryptographically strong but not so weak that someone will shoot themselves
3205 in the foot using it as a nonce in input in some email header scheme or
3206 whatever weirdness they'll twist this into.  The result should handle fork()
3207 and avoid repeating sequences.  OpenSSL handles that for us.
3208
3209 Arguments:
3210   max       range maximum
3211 Returns     a random number in range [0, max-1]
3212 */
3213
3214 int
3215 vaguely_random_number(int max)
3216 {
3217 unsigned int r;
3218 int i, needed_len;
3219 static pid_t pidlast = 0;
3220 pid_t pidnow;
3221 uschar smallbuf[sizeof(r)];
3222
3223 if (max <= 1)
3224   return 0;
3225
3226 pidnow = getpid();
3227 if (pidnow != pidlast)
3228   {
3229   /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3230   is unique for each thread", this doesn't apparently apply across processes,
3231   so our own warning from vaguely_random_number_fallback() applies here too.
3232   Fix per PostgreSQL. */
3233   if (pidlast != 0)
3234     RAND_cleanup();
3235   pidlast = pidnow;
3236   }
3237
3238 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3239 if (!RAND_status())
3240   {
3241   randstuff r;
3242   gettimeofday(&r.tv, NULL);
3243   r.p = getpid();
3244
3245   RAND_seed(US (&r), sizeof(r));
3246   }
3247 /* We're after pseudo-random, not random; if we still don't have enough data
3248 in the internal PRNG then our options are limited.  We could sleep and hope
3249 for entropy to come along (prayer technique) but if the system is so depleted
3250 in the first place then something is likely to just keep taking it.  Instead,
3251 we'll just take whatever little bit of pseudo-random we can still manage to
3252 get. */
3253
3254 needed_len = sizeof(r);
3255 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3256 asked for a number less than 10. */
3257 for (r = max, i = 0; r; ++i)
3258   r >>= 1;
3259 i = (i + 7) / 8;
3260 if (i < needed_len)
3261   needed_len = i;
3262
3263 #ifdef EXIM_HAVE_RAND_PSEUDO
3264 /* We do not care if crypto-strong */
3265 i = RAND_pseudo_bytes(smallbuf, needed_len);
3266 #else
3267 i = RAND_bytes(smallbuf, needed_len);
3268 #endif
3269
3270 if (i < 0)
3271   {
3272   DEBUG(D_all)
3273     debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3274   return vaguely_random_number_fallback(max);
3275   }
3276
3277 r = 0;
3278 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3279   r = 256 * r + *p;
3280
3281 /* We don't particularly care about weighted results; if someone wants
3282 smooth distribution and cares enough then they should submit a patch then. */
3283 return r % max;
3284 }
3285
3286
3287
3288
3289 /*************************************************
3290 *        OpenSSL option parse                    *
3291 *************************************************/
3292
3293 /* Parse one option for tls_openssl_options_parse below
3294
3295 Arguments:
3296   name    one option name
3297   value   place to store a value for it
3298 Returns   success or failure in parsing
3299 */
3300
3301
3302
3303 static BOOL
3304 tls_openssl_one_option_parse(uschar *name, long *value)
3305 {
3306 int first = 0;
3307 int last = exim_openssl_options_size;
3308 while (last > first)
3309   {
3310   int middle = (first + last)/2;
3311   int c = Ustrcmp(name, exim_openssl_options[middle].name);
3312   if (c == 0)
3313     {
3314     *value = exim_openssl_options[middle].value;
3315     return TRUE;
3316     }
3317   else if (c > 0)
3318     first = middle + 1;
3319   else
3320     last = middle;
3321   }
3322 return FALSE;
3323 }
3324
3325
3326
3327
3328 /*************************************************
3329 *        OpenSSL option parsing logic            *
3330 *************************************************/
3331
3332 /* OpenSSL has a number of compatibility options which an administrator might
3333 reasonably wish to set.  Interpret a list similarly to decode_bits(), so that
3334 we look like log_selector.
3335
3336 Arguments:
3337   option_spec  the administrator-supplied string of options
3338   results      ptr to long storage for the options bitmap
3339 Returns        success or failure
3340 */
3341
3342 BOOL
3343 tls_openssl_options_parse(uschar *option_spec, long *results)
3344 {
3345 long result, item;
3346 uschar *end;
3347 uschar keep_c;
3348 BOOL adding, item_parsed;
3349
3350 result = SSL_OP_NO_TICKET;
3351 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3352  * from default because it increases BEAST susceptibility. */
3353 #ifdef SSL_OP_NO_SSLv2
3354 result |= SSL_OP_NO_SSLv2;
3355 #endif
3356 #ifdef SSL_OP_SINGLE_DH_USE
3357 result |= SSL_OP_SINGLE_DH_USE;
3358 #endif
3359
3360 if (!option_spec)
3361   {
3362   *results = result;
3363   return TRUE;
3364   }
3365
3366 for (uschar * s = option_spec; *s != '\0'; /**/)
3367   {
3368   while (isspace(*s)) ++s;
3369   if (*s == '\0')
3370     break;
3371   if (*s != '+' && *s != '-')
3372     {
3373     DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3374         "+ or - expected but found \"%s\"\n", s);
3375     return FALSE;
3376     }
3377   adding = *s++ == '+';
3378   for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3379   keep_c = *end;
3380   *end = '\0';
3381   item_parsed = tls_openssl_one_option_parse(s, &item);
3382   *end = keep_c;
3383   if (!item_parsed)
3384     {
3385     DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3386     return FALSE;
3387     }
3388   DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3389       adding ? "adding" : "removing", result, item, s);
3390   if (adding)
3391     result |= item;
3392   else
3393     result &= ~item;
3394   s = end;
3395   }
3396
3397 *results = result;
3398 return TRUE;
3399 }
3400
3401 #endif  /*!MACRO_PREDEF*/
3402 /* vi: aw ai sw=2
3403 */
3404 /* End of tls-openssl.c */