src/src/dkim.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge, 1995 - 2017 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* Code for DKIM support. Other DKIM relevant code is in
   9    receive.c, transport.c and transports/smtp.c */
  10
  11 #include "exim.h"
  12
  13 #ifndef DISABLE_DKIM
  14
  15 #include "pdkim/pdkim.h"
  16
  17 int dkim_verify_oldpool;
  18 pdkim_ctx *dkim_verify_ctx = NULL;
  19 pdkim_signature *dkim_signatures = NULL;
  20 pdkim_signature *dkim_cur_sig = NULL;
  21 static const uschar * dkim_collect_error = NULL;
  22
  23
  24
  25 /*XXX the caller only uses the first record if we return multiple.
  26 Could we hand back an allocated string?
  27 */
  28
  29 static int
  30 dkim_exim_query_dns_txt(char *name, char *answer)
  31 {
  32 dns_answer dnsa;
  33 dns_scan dnss;
  34 dns_record *rr;
  35
  36 lookup_dnssec_authenticated = NULL;
  37 if (dns_lookup(&dnsa, US name, T_TXT, NULL) != DNS_SUCCEED)
  38   return PDKIM_FAIL;    /*XXX better error detail?  logging? */
  39
  40 /* Search for TXT record */
  41
  42 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
  43      rr;
  44      rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
  45   if (rr->type == T_TXT)
  46     {
  47     int rr_offset = 0;
  48     int answer_offset = 0;
  49
  50     /* Copy record content to the answer buffer */
  51
  52     while (rr_offset < rr->size)
  53       {
  54       uschar len = rr->data[rr_offset++];
  55       snprintf(answer + answer_offset,
  56                 PDKIM_DNS_TXT_MAX_RECLEN - answer_offset,
  57                 "%.*s", (int)len, CS  (rr->data + rr_offset));
  58       rr_offset += len;
  59       answer_offset += len;
  60       if (answer_offset >= PDKIM_DNS_TXT_MAX_RECLEN)
  61         return PDKIM_FAIL;      /*XXX better error detail?  logging? */
  62       }
  63     return PDKIM_OK;
  64     }
  65
  66 return PDKIM_FAIL;      /*XXX better error detail?  logging? */
  67 }
  68
  69
  70 void
  71 dkim_exim_init(void)
  72 {
  73 pdkim_init();
  74 }
  75
  76
  77
  78 void
  79 dkim_exim_verify_init(BOOL dot_stuffing)
  80 {
  81 /* There is a store-reset between header & body reception
  82 so cannot use the main pool. Any allocs done by Exim
  83 memory-handling must use the perm pool. */
  84
  85 dkim_verify_oldpool = store_pool;
  86 store_pool = POOL_PERM;
  87
  88 /* Free previous context if there is one */
  89
  90 if (dkim_verify_ctx)
  91   pdkim_free_ctx(dkim_verify_ctx);
  92
  93 /* Create new context */
  94
  95 dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing);
  96 dkim_collect_input = !!dkim_verify_ctx;
  97 dkim_collect_error = NULL;
  98
  99 /* Start feed up with any cached data */
 100 receive_get_cache();
 101
 102 store_pool = dkim_verify_oldpool;
 103 }
 104
 105
 106 void
 107 dkim_exim_verify_feed(uschar * data, int len)
 108 {
 109 int rc;
 110
 111 store_pool = POOL_PERM;
 112 if (  dkim_collect_input
 113    && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK)
 114   {
 115   dkim_collect_error = pdkim_errstr(rc);
 116   log_write(0, LOG_MAIN,
 117              "DKIM: validation error: %.100s", dkim_collect_error);
 118   dkim_collect_input = FALSE;
 119   }
 120 store_pool = dkim_verify_oldpool;
 121 }
 122
 123
 124 void
 125 dkim_exim_verify_finish(void)
 126 {
 127 pdkim_signature * sig = NULL;
 128 int rc;
 129 gstring * g = NULL;
 130 const uschar * errstr;
 131
 132 store_pool = POOL_PERM;
 133
 134 /* Delete eventual previous signature chain */
 135
 136 dkim_signers = NULL;
 137 dkim_signatures = NULL;
 138
 139 if (dkim_collect_error)
 140   {
 141   log_write(0, LOG_MAIN,
 142       "DKIM: Error during validation, disabling signature verification: %.100s",
 143       dkim_collect_error);
 144   dkim_disable_verify = TRUE;
 145   goto out;
 146   }
 147
 148 dkim_collect_input = FALSE;
 149
 150 /* Finish DKIM operation and fetch link to signatures chain */
 151
 152 rc = pdkim_feed_finish(dkim_verify_ctx, &dkim_signatures, &errstr);
 153 if (rc != PDKIM_OK)
 154   {
 155   log_write(0, LOG_MAIN, "DKIM: validation error: %.100s%s%s", pdkim_errstr(rc),
 156             errstr ? ": " : "", errstr ? errstr : US"");
 157   goto out;
 158   }
 159
 160 for (sig = dkim_signatures; sig; sig = sig->next)
 161   {
 162   uschar * s;
 163   gstring * logmsg;
 164
 165   /* Log a line for each signature */
 166
 167   if (!(s = sig->domain)) s = US"<UNSET>";
 168   logmsg = string_append(NULL, 2, "d=", s);
 169   if (!(s = sig->selector)) s = US"<UNSET>";
 170   logmsg = string_append(logmsg, 2, " s=", s);
 171   logmsg = string_append(logmsg, 7,
 172         " c=", sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
 173         "/",   sig->canon_body    == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
 174         " a=", dkim_sig_to_a_tag(sig),
 175         string_sprintf(" b=" SIZE_T_FMT,
 176                         (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : 0));
 177   if ((s= sig->identity)) logmsg = string_append(logmsg, 2, " i=", s);
 178   if (sig->created > 0) logmsg = string_cat(logmsg,
 179                                       string_sprintf(" t=%lu", sig->created));
 180   if (sig->expires > 0) logmsg = string_cat(logmsg,
 181                                       string_sprintf(" x=%lu", sig->expires));
 182   if (sig->bodylength > -1) logmsg = string_cat(logmsg,
 183                                       string_sprintf(" l=%lu", sig->bodylength));
 184
 185   switch (sig->verify_status)
 186     {
 187     case PDKIM_VERIFY_NONE:
 188       logmsg = string_cat(logmsg, " [not verified]");
 189       break;
 190
 191     case PDKIM_VERIFY_INVALID:
 192       logmsg = string_cat(logmsg, " [invalid - ");
 193       switch (sig->verify_ext_status)
 194         {
 195         case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
 196           logmsg = string_cat(logmsg,
 197                         "public key record (currently?) unavailable]");
 198           break;
 199
 200         case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
 201           logmsg = string_cat(logmsg, "overlong public key record]");
 202           break;
 203
 204         case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:
 205         case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:
 206           logmsg = string_cat(logmsg, "syntax error in public key record]");
 207           break;
 208
 209         case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR:
 210           logmsg = string_cat(logmsg, "signature tag missing or invalid]");
 211           break;
 212
 213         case PDKIM_VERIFY_INVALID_DKIM_VERSION:
 214           logmsg = string_cat(logmsg, "unsupported DKIM version]");
 215           break;
 216
 217         default:
 218           logmsg = string_cat(logmsg, "unspecified problem]");
 219         }
 220       break;
 221
 222     case PDKIM_VERIFY_FAIL:
 223       logmsg =
 224         string_cat(logmsg, " [verification failed - ");
 225       switch (sig->verify_ext_status)
 226         {
 227         case PDKIM_VERIFY_FAIL_BODY:
 228           logmsg = string_cat(logmsg,
 229                        "body hash mismatch (body probably modified in transit)]");
 230           break;
 231
 232         case PDKIM_VERIFY_FAIL_MESSAGE:
 233           logmsg = string_cat(logmsg,
 234                        "signature did not verify (headers probably modified in transit)]");
 235         break;
 236
 237         default:
 238           logmsg = string_cat(logmsg, "unspecified reason]");
 239         }
 240       break;
 241
 242     case PDKIM_VERIFY_PASS:
 243       logmsg = string_cat(logmsg, " [verification succeeded]");
 244       break;
 245     }
 246
 247   log_write(0, LOG_MAIN, "DKIM: %s", string_from_gstring(logmsg));
 248
 249   /* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */
 250
 251   if (sig->domain)
 252     g = string_append_listele(g, ':', sig->domain);
 253
 254   if (sig->identity)
 255     g = string_append_listele(g, ':', sig->identity);
 256
 257   /* Process next signature */
 258   }
 259
 260 if (g) dkim_signers = g->s;
 261
 262 out:
 263 store_pool = dkim_verify_oldpool;
 264 }
 265
 266
 267 void
 268 dkim_exim_acl_setup(uschar * id)
 269 {
 270 pdkim_signature * sig;
 271 uschar * cmp_val;
 272
 273 dkim_cur_sig = NULL;
 274 dkim_cur_signer = id;
 275
 276 if (dkim_disable_verify || !id || !dkim_verify_ctx)
 277   return;
 278
 279 /* Find signature to run ACL on */
 280
 281 for (sig = dkim_signatures; sig; sig = sig->next)
 282   if (  (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain)
 283      && strcmpic(cmp_val, id) == 0
 284      )
 285     {
 286     dkim_cur_sig = sig;
 287
 288     /* The "dkim_domain" and "dkim_selector" expansion variables have
 289        related globals, since they are used in the signing code too.
 290        Instead of inventing separate names for verification, we set
 291        them here. This is easy since a domain and selector is guaranteed
 292        to be in a signature. The other dkim_* expansion items are
 293        dynamically fetched from dkim_cur_sig at expansion time (see
 294        function below). */
 295
 296     dkim_signing_domain = US sig->domain;
 297     dkim_signing_selector = US sig->selector;
 298     dkim_key_length = sig->sighash.len * 8;
 299     return;
 300     }
 301 }
 302
 303
 304 static uschar *
 305 dkim_exim_expand_defaults(int what)
 306 {
 307 switch (what)
 308   {
 309   case DKIM_ALGO:               return US"";
 310   case DKIM_BODYLENGTH:         return US"9999999999999";
 311   case DKIM_CANON_BODY:         return US"";
 312   case DKIM_CANON_HEADERS:      return US"";
 313   case DKIM_COPIEDHEADERS:      return US"";
 314   case DKIM_CREATED:            return US"0";
 315   case DKIM_EXPIRES:            return US"9999999999999";
 316   case DKIM_HEADERNAMES:        return US"";
 317   case DKIM_IDENTITY:           return US"";
 318   case DKIM_KEY_GRANULARITY:    return US"*";
 319   case DKIM_KEY_SRVTYPE:        return US"*";
 320   case DKIM_KEY_NOTES:          return US"";
 321   case DKIM_KEY_TESTING:        return US"0";
 322   case DKIM_NOSUBDOMAINS:       return US"0";
 323   case DKIM_VERIFY_STATUS:      return US"none";
 324   case DKIM_VERIFY_REASON:      return US"";
 325   default:                      return US"";
 326   }
 327 }
 328
 329
 330 uschar *
 331 dkim_exim_expand_query(int what)
 332 {
 333 if (!dkim_verify_ctx || dkim_disable_verify || !dkim_cur_sig)
 334   return dkim_exim_expand_defaults(what);
 335
 336 switch (what)
 337   {
 338   case DKIM_ALGO:
 339     return dkim_sig_to_a_tag(dkim_cur_sig);
 340
 341   case DKIM_BODYLENGTH:
 342     return dkim_cur_sig->bodylength >= 0
 343       ? string_sprintf("%ld", dkim_cur_sig->bodylength)
 344       : dkim_exim_expand_defaults(what);
 345
 346   case DKIM_CANON_BODY:
 347     switch (dkim_cur_sig->canon_body)
 348       {
 349       case PDKIM_CANON_RELAXED: return US"relaxed";
 350       case PDKIM_CANON_SIMPLE:
 351       default:                  return US"simple";
 352       }
 353
 354   case DKIM_CANON_HEADERS:
 355   switch (dkim_cur_sig->canon_headers)
 356     {
 357     case PDKIM_CANON_RELAXED:   return US"relaxed";
 358     case PDKIM_CANON_SIMPLE:
 359     default:                    return US"simple";
 360     }
 361
 362   case DKIM_COPIEDHEADERS:
 363     return dkim_cur_sig->copiedheaders
 364       ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what);
 365
 366   case DKIM_CREATED:
 367     return dkim_cur_sig->created > 0
 368       ? string_sprintf("%lu", dkim_cur_sig->created)
 369       : dkim_exim_expand_defaults(what);
 370
 371   case DKIM_EXPIRES:
 372     return dkim_cur_sig->expires > 0
 373       ? string_sprintf("%lu", dkim_cur_sig->expires)
 374       : dkim_exim_expand_defaults(what);
 375
 376   case DKIM_HEADERNAMES:
 377     return dkim_cur_sig->headernames
 378       ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what);
 379
 380   case DKIM_IDENTITY:
 381     return dkim_cur_sig->identity
 382       ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what);
 383
 384   case DKIM_KEY_GRANULARITY:
 385     return dkim_cur_sig->pubkey
 386       ? dkim_cur_sig->pubkey->granularity
 387       ? US dkim_cur_sig->pubkey->granularity
 388       : dkim_exim_expand_defaults(what)
 389       : dkim_exim_expand_defaults(what);
 390
 391   case DKIM_KEY_SRVTYPE:
 392     return dkim_cur_sig->pubkey
 393       ? dkim_cur_sig->pubkey->srvtype
 394       ? US dkim_cur_sig->pubkey->srvtype
 395       : dkim_exim_expand_defaults(what)
 396       : dkim_exim_expand_defaults(what);
 397
 398   case DKIM_KEY_NOTES:
 399     return dkim_cur_sig->pubkey
 400       ? dkim_cur_sig->pubkey->notes
 401       ? US dkim_cur_sig->pubkey->notes
 402       : dkim_exim_expand_defaults(what)
 403       : dkim_exim_expand_defaults(what);
 404
 405   case DKIM_KEY_TESTING:
 406     return dkim_cur_sig->pubkey
 407       ? dkim_cur_sig->pubkey->testing
 408       ? US"1"
 409       : dkim_exim_expand_defaults(what)
 410       : dkim_exim_expand_defaults(what);
 411
 412   case DKIM_NOSUBDOMAINS:
 413     return dkim_cur_sig->pubkey
 414       ? dkim_cur_sig->pubkey->no_subdomaining
 415       ? US"1"
 416       : dkim_exim_expand_defaults(what)
 417       : dkim_exim_expand_defaults(what);
 418
 419   case DKIM_VERIFY_STATUS:
 420     switch (dkim_cur_sig->verify_status)
 421       {
 422       case PDKIM_VERIFY_INVALID:        return US"invalid";
 423       case PDKIM_VERIFY_FAIL:           return US"fail";
 424       case PDKIM_VERIFY_PASS:           return US"pass";
 425       case PDKIM_VERIFY_NONE:
 426       default:                          return US"none";
 427       }
 428
 429   case DKIM_VERIFY_REASON:
 430     switch (dkim_cur_sig->verify_ext_status)
 431       {
 432       case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
 433                                                 return US"pubkey_unavailable";
 434       case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax";
 435       case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:  return US"pubkey_der_syntax";
 436       case PDKIM_VERIFY_FAIL_BODY:              return US"bodyhash_mismatch";
 437       case PDKIM_VERIFY_FAIL_MESSAGE:           return US"signature_incorrect";
 438       }
 439
 440   default:
 441     return US"";
 442   }
 443 }
 444
 445
 446 /* Generate signatures for the given file, returning a string.
 447 If a prefix is given, prepend it to the file for the calculations.
 448 */
 449
 450 gstring *
 451 dkim_exim_sign(int fd, off_t off, uschar * prefix,
 452   struct ob_dkim * dkim, const uschar ** errstr)
 453 {
 454 const uschar * dkim_domain;
 455 int sep = 0;
 456 gstring * seen_doms = NULL;
 457 pdkim_ctx ctx;
 458 pdkim_signature * sig;
 459 gstring * sigbuf;
 460 int pdkim_rc;
 461 int sread;
 462 uschar buf[4096];
 463 int save_errno = 0;
 464 int old_pool = store_pool;
 465 uschar * errwhen;
 466
 467 store_pool = POOL_MAIN;
 468
 469 pdkim_init_context(&ctx, dkim->dot_stuffed, &dkim_exim_query_dns_txt);
 470
 471 if (!(dkim_domain = expand_cstring(dkim->dkim_domain)))
 472   /* expansion error, do not send message. */
 473   { errwhen = US"dkim_domain"; goto expand_bad; }
 474
 475 /* Set $dkim_domain expansion variable to each unique domain in list. */
 476
 477 while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0)))
 478   {
 479   const uschar * dkim_sel;
 480   int sel_sep = 0;
 481
 482   if (dkim_signing_domain[0] == '\0')
 483     continue;
 484
 485   /* Only sign once for each domain, no matter how often it
 486   appears in the expanded list. */
 487
 488   if (match_isinlist(dkim_signing_domain, CUSS &seen_doms,
 489       0, NULL, NULL, MCL_STRING, TRUE, NULL) == OK)
 490     continue;
 491
 492   seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain);
 493
 494   /* Set $dkim_selector expansion variable to each selector in list,
 495   for this domain. */
 496
 497   if (!(dkim_sel = expand_string(dkim->dkim_selector)))
 498   if (!(dkim_signing_selector = expand_string(dkim->dkim_selector)))
 499     { errwhen = US"dkim_selector"; goto expand_bad; }
 500
 501   while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep,
 502           NULL, 0)))
 503     {
 504     uschar * dkim_canon_expanded;
 505     int pdkim_canon;
 506     uschar * dkim_sign_headers_expanded = NULL;
 507     uschar * dkim_private_key_expanded;
 508     uschar * dkim_hash_expanded;
 509     uschar * dkim_identity_expanded = NULL;
 510
 511     /* Get canonicalization to use */
 512
 513     dkim_canon_expanded = dkim->dkim_canon
 514       ? expand_string(dkim->dkim_canon) : US"relaxed";
 515     if (!dkim_canon_expanded)   /* expansion error, do not send message. */
 516       { errwhen = US"dkim_canon"; goto expand_bad; }
 517
 518     if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0)
 519       pdkim_canon = PDKIM_CANON_RELAXED;
 520     else if (Ustrcmp(dkim_canon_expanded, "simple") == 0)
 521       pdkim_canon = PDKIM_CANON_SIMPLE;
 522     else
 523       {
 524       log_write(0, LOG_MAIN,
 525                  "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",
 526                  dkim_canon_expanded);
 527       pdkim_canon = PDKIM_CANON_RELAXED;
 528       }
 529
 530     if (  dkim->dkim_sign_headers
 531        && !(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers)))
 532       { errwhen = US"dkim_sign_header"; goto expand_bad; }
 533     /* else pass NULL, which means default header list */
 534
 535     /* Get private key to use. */
 536
 537     if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key)))
 538       { errwhen = US"dkim_private_key"; goto expand_bad; }
 539
 540     if (  Ustrlen(dkim_private_key_expanded) == 0
 541        || Ustrcmp(dkim_private_key_expanded, "0") == 0
 542        || Ustrcmp(dkim_private_key_expanded, "false") == 0
 543        )
 544       continue;         /* don't sign, but no error */
 545
 546     if (dkim_private_key_expanded[0] == '/')
 547       {
 548       int privkey_fd, off = 0, len;
 549
 550       /* Looks like a filename, load the private key. */
 551
 552       memset(big_buffer, 0, big_buffer_size);
 553
 554       if ((privkey_fd = open(CS dkim_private_key_expanded, O_RDONLY)) < 0)
 555         {
 556         log_write(0, LOG_MAIN | LOG_PANIC, "unable to open "
 557                    "private key file for reading: %s",
 558                    dkim_private_key_expanded);
 559         goto bad;
 560         }
 561
 562       do
 563         {
 564         if ((len = read(privkey_fd, big_buffer + off, big_buffer_size - 2 - off)) < 0)
 565           {
 566           (void) close(privkey_fd);
 567           log_write(0, LOG_MAIN|LOG_PANIC, "unable to read private key file: %s",
 568                      dkim_private_key_expanded);
 569           goto bad;
 570           }
 571         off += len;
 572         }
 573       while (len > 0);
 574
 575       (void) close(privkey_fd);
 576       big_buffer[off] = '\0';
 577       dkim_private_key_expanded = big_buffer;
 578       }
 579
 580     if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash)))
 581       { errwhen = US"dkim_hash"; goto expand_bad; }
 582
 583     if (dkim->dkim_identity)
 584       if (!(dkim_identity_expanded = expand_string(dkim->dkim_identity)))
 585         { errwhen = US"dkim_identity"; goto expand_bad; }
 586       else if (!*dkim_identity_expanded)
 587         dkim_identity_expanded = NULL;
 588
 589   /*XXX so we currently nail signing to RSA + this hash.
 590   Need to extract algo from privkey and check for disallowed combos. */
 591
 592     if (!(sig = pdkim_init_sign(&ctx, dkim_signing_domain,
 593                           dkim_signing_selector,
 594                           dkim_private_key_expanded,
 595                           dkim_hash_expanded,
 596                           errstr
 597                           )))
 598       goto bad;
 599     dkim_private_key_expanded[0] = '\0';
 600
 601     pdkim_set_optional(sig,
 602                         CS dkim_sign_headers_expanded,
 603                         dkim_identity_expanded,
 604                         pdkim_canon,
 605                         pdkim_canon, -1, 0, 0);
 606
 607     if (!ctx.sig)               /* link sig to context chain */
 608       ctx.sig = sig;
 609     else
 610       {
 611       pdkim_signature * n = ctx.sig;
 612       while (n->next) n = n->next;
 613       n->next = sig;
 614       }
 615     }
 616   }
 617
 618 if (prefix)
 619   pdkim_feed(&ctx, prefix, Ustrlen(prefix));
 620
 621 if (lseek(fd, off, SEEK_SET) < 0)
 622   sread = -1;
 623 else
 624   while ((sread = read(fd, &buf, sizeof(buf))) > 0)
 625     if ((pdkim_rc = pdkim_feed(&ctx, buf, sread)) != PDKIM_OK)
 626       goto pk_bad;
 627
 628 /* Handle failed read above. */
 629 if (sread == -1)
 630   {
 631   debug_printf("DKIM: Error reading -K file.\n");
 632   save_errno = errno;
 633   goto bad;
 634   }
 635
 636 /* Build string of headers, one per signature */
 637
 638 if ((pdkim_rc = pdkim_feed_finish(&ctx, &sig, errstr)) != PDKIM_OK)
 639   goto pk_bad;
 640
 641 for (sigbuf = NULL; sig; sig = sig->next)
 642   sigbuf = string_append(sigbuf, 2, US sig->signature_header, US"\r\n");
 643
 644 (void) string_from_gstring(sigbuf);
 645
 646 CLEANUP:
 647   store_pool = old_pool;
 648   errno = save_errno;
 649   return sigbuf;
 650
 651 pk_bad:
 652   log_write(0, LOG_MAIN|LOG_PANIC,
 653                 "DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc));
 654 bad:
 655   sigbuf = NULL;
 656   goto CLEANUP;
 657
 658 expand_bad:
 659   log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand %s: %s",
 660               errwhen, expand_string_message);
 661   goto bad;
 662 }
 663
 664 #endif