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DKIM: Under debug, when signing do an extra check on the dns record that will be
[exim.git] / src / src / pdkim / pdkim.c
1 /*
2 * PDKIM - a RFC4871 (DKIM) implementation
3 *
4 * Copyright (C) 2009 - 2016 Tom Kistner <tom@duncanthrax.net>
5 * Copyright (C) 2016 Jeremy Harris <jgh@exim.org>
6 *
7 * http://duncanthrax.net/pdkim/
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License along
20 * with this program; if not, write to the Free Software Foundation, Inc.,
21 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22 */
23
24 #include "../exim.h"
25
26
27 #ifndef DISABLE_DKIM /* entire file */
28
29 #ifndef SUPPORT_TLS
30 # error Need SUPPORT_TLS for DKIM
31 #endif
32
33 #include "crypt_ver.h"
34
35 #ifdef RSA_OPENSSL
36 # include <openssl/rsa.h>
37 # include <openssl/ssl.h>
38 # include <openssl/err.h>
39 #elif defined(RSA_GNUTLS)
40 # include <gnutls/gnutls.h>
41 # include <gnutls/x509.h>
42 #endif
43
44 #include "pdkim.h"
45 #include "rsa.h"
46
47 #define PDKIM_SIGNATURE_VERSION "1"
48 #define PDKIM_PUB_RECORD_VERSION US "DKIM1"
49
50 #define PDKIM_MAX_HEADER_LEN 65536
51 #define PDKIM_MAX_HEADERS 512
52 #define PDKIM_MAX_BODY_LINE_LEN 16384
53 #define PDKIM_DNS_TXT_MAX_NAMELEN 1024
54 #define PDKIM_DEFAULT_SIGN_HEADERS "From:Sender:Reply-To:Subject:Date:"\
55 "Message-ID:To:Cc:MIME-Version:Content-Type:"\
56 "Content-Transfer-Encoding:Content-ID:"\
57 "Content-Description:Resent-Date:Resent-From:"\
58 "Resent-Sender:Resent-To:Resent-Cc:"\
59 "Resent-Message-ID:In-Reply-To:References:"\
60 "List-Id:List-Help:List-Unsubscribe:"\
61 "List-Subscribe:List-Post:List-Owner:List-Archive"
62
63 /* -------------------------------------------------------------------------- */
64 struct pdkim_stringlist {
65 uschar * value;
66 int tag;
67 void * next;
68 };
69
70 /* -------------------------------------------------------------------------- */
71 /* A bunch of list constants */
72 const uschar * pdkim_querymethods[] = {
73 US"dns/txt",
74 NULL
75 };
76 const uschar * pdkim_algos[] = {
77 US"rsa-sha256",
78 US"rsa-sha1",
79 NULL
80 };
81 const uschar * pdkim_canons[] = {
82 US"simple",
83 US"relaxed",
84 NULL
85 };
86 const uschar * pdkim_hashes[] = {
87 US"sha256",
88 US"sha1",
89 NULL
90 };
91 const uschar * pdkim_keytypes[] = {
92 US"rsa",
93 NULL
94 };
95
96 typedef struct pdkim_combined_canon_entry {
97 const uschar * str;
98 int canon_headers;
99 int canon_body;
100 } pdkim_combined_canon_entry;
101
102 pdkim_combined_canon_entry pdkim_combined_canons[] = {
103 { US"simple/simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE },
104 { US"simple/relaxed", PDKIM_CANON_SIMPLE, PDKIM_CANON_RELAXED },
105 { US"relaxed/simple", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE },
106 { US"relaxed/relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_RELAXED },
107 { US"simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE },
108 { US"relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE },
109 { NULL, 0, 0 }
110 };
111
112
113 /* -------------------------------------------------------------------------- */
114
115 const char *
116 pdkim_verify_status_str(int status)
117 {
118 switch(status)
119 {
120 case PDKIM_VERIFY_NONE: return "PDKIM_VERIFY_NONE";
121 case PDKIM_VERIFY_INVALID: return "PDKIM_VERIFY_INVALID";
122 case PDKIM_VERIFY_FAIL: return "PDKIM_VERIFY_FAIL";
123 case PDKIM_VERIFY_PASS: return "PDKIM_VERIFY_PASS";
124 default: return "PDKIM_VERIFY_UNKNOWN";
125 }
126 }
127
128 const char *
129 pdkim_verify_ext_status_str(int ext_status)
130 {
131 switch(ext_status)
132 {
133 case PDKIM_VERIFY_FAIL_BODY: return "PDKIM_VERIFY_FAIL_BODY";
134 case PDKIM_VERIFY_FAIL_MESSAGE: return "PDKIM_VERIFY_FAIL_MESSAGE";
135 case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: return "PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE";
136 case PDKIM_VERIFY_INVALID_BUFFER_SIZE: return "PDKIM_VERIFY_INVALID_BUFFER_SIZE";
137 case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: return "PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD";
138 case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return "PDKIM_VERIFY_INVALID_PUBKEY_IMPORT";
139 case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: return "PDKIM_VERIFY_INVALID_SIGNATURE_ERROR";
140 case PDKIM_VERIFY_INVALID_DKIM_VERSION: return "PDKIM_VERIFY_INVALID_DKIM_VERSION";
141 default: return "PDKIM_VERIFY_UNKNOWN";
142 }
143 }
144
145 const char *
146 pdkim_errstr(int status)
147 {
148 switch(status)
149 {
150 case PDKIM_OK: return "OK";
151 case PDKIM_FAIL: return "FAIL";
152 case PDKIM_ERR_RSA_PRIVKEY: return "RSA_PRIVKEY";
153 case PDKIM_ERR_RSA_SIGNING: return "RSA SIGNING";
154 case PDKIM_ERR_LONG_LINE: return "RSA_LONG_LINE";
155 case PDKIM_ERR_BUFFER_TOO_SMALL: return "BUFFER_TOO_SMALL";
156 case PDKIM_SIGN_PRIVKEY_WRAP: return "PRIVKEY_WRAP";
157 case PDKIM_SIGN_PRIVKEY_B64D: return "PRIVKEY_B64D";
158 default: return "(unknown)";
159 }
160 }
161
162
163 /* -------------------------------------------------------------------------- */
164 /* Print debugging functions */
165 static void
166 pdkim_quoteprint(const uschar *data, int len)
167 {
168 int i;
169 for (i = 0; i < len; i++)
170 {
171 const int c = data[i];
172 switch (c)
173 {
174 case ' ' : debug_printf("{SP}"); break;
175 case '\t': debug_printf("{TB}"); break;
176 case '\r': debug_printf("{CR}"); break;
177 case '\n': debug_printf("{LF}"); break;
178 case '{' : debug_printf("{BO}"); break;
179 case '}' : debug_printf("{BC}"); break;
180 default:
181 if ( (c < 32) || (c > 127) )
182 debug_printf("{%02x}", c);
183 else
184 debug_printf("%c", c);
185 break;
186 }
187 }
188 debug_printf("\n");
189 }
190
191 static void
192 pdkim_hexprint(const uschar *data, int len)
193 {
194 int i;
195 for (i = 0 ; i < len; i++) debug_printf("%02x", data[i]);
196 debug_printf("\n");
197 }
198
199
200
201 static pdkim_stringlist *
202 pdkim_prepend_stringlist(pdkim_stringlist * base, const uschar * str)
203 {
204 pdkim_stringlist * new_entry = store_get(sizeof(pdkim_stringlist));
205
206 memset(new_entry, 0, sizeof(pdkim_stringlist));
207 new_entry->value = string_copy(str);
208 if (base) new_entry->next = base;
209 return new_entry;
210 }
211
212
213
214 /* Trim whitespace fore & aft */
215
216 static void
217 pdkim_strtrim(uschar * str)
218 {
219 uschar * p = str;
220 uschar * q = str;
221 while (*p == '\t' || *p == ' ') p++; /* skip whitespace */
222 while (*p) {*q = *p; q++; p++;} /* dump the leading whitespace */
223 *q = '\0';
224 while (q != str && ( (*q == '\0') || (*q == '\t') || (*q == ' ') ) )
225 { /* dump trailing whitespace */
226 *q = '\0';
227 q--;
228 }
229 }
230
231
232
233 /* -------------------------------------------------------------------------- */
234
235 DLLEXPORT void
236 pdkim_free_ctx(pdkim_ctx *ctx)
237 {
238 }
239
240
241 /* -------------------------------------------------------------------------- */
242 /* Matches the name of the passed raw "header" against
243 the passed colon-separated "tick", and invalidates
244 the entry in tick. Returns OK or fail-code */
245 /*XXX might be safer done using a pdkim_stringlist for "tick" */
246
247 static int
248 header_name_match(const uschar * header, uschar * tick)
249 {
250 uschar * hname;
251 uschar * lcopy;
252 uschar * p;
253 uschar * q;
254 uschar * hcolon = Ustrchr(header, ':'); /* Get header name */
255
256 if (!hcolon)
257 return PDKIM_FAIL; /* This isn't a header */
258
259 /* if we had strncmpic() we wouldn't need this copy */
260 hname = string_copyn(header, hcolon-header);
261
262 /* Copy tick-off list locally, so we can punch zeroes into it */
263 p = lcopy = string_copy(tick);
264
265 for (q = Ustrchr(p, ':'); q; q = Ustrchr(p, ':'))
266 {
267 *q = '\0';
268 if (strcmpic(p, hname) == 0)
269 goto found;
270
271 p = q+1;
272 }
273
274 if (strcmpic(p, hname) == 0)
275 goto found;
276
277 return PDKIM_FAIL;
278
279 found:
280 /* Invalidate header name instance in tick-off list */
281 tick[p-lcopy] = '_';
282 return PDKIM_OK;
283 }
284
285
286 /* -------------------------------------------------------------------------- */
287 /* Performs "relaxed" canonicalization of a header. */
288
289 static uschar *
290 pdkim_relax_header(const uschar * header, int crlf)
291 {
292 BOOL past_field_name = FALSE;
293 BOOL seen_wsp = FALSE;
294 const uschar * p;
295 uschar * relaxed = store_get(Ustrlen(header)+3);
296 uschar * q = relaxed;
297
298 for (p = header; *p; p++)
299 {
300 uschar c = *p;
301 /* Ignore CR & LF */
302 if (c == '\r' || c == '\n')
303 continue;
304 if (c == '\t' || c == ' ')
305 {
306 if (seen_wsp)
307 continue;
308 c = ' '; /* Turns WSP into SP */
309 seen_wsp = TRUE;
310 }
311 else
312 if (!past_field_name && c == ':')
313 {
314 if (seen_wsp) q--; /* This removes WSP before the colon */
315 seen_wsp = TRUE; /* This removes WSP after the colon */
316 past_field_name = TRUE;
317 }
318 else
319 seen_wsp = FALSE;
320
321 /* Lowercase header name */
322 if (!past_field_name) c = tolower(c);
323 *q++ = c;
324 }
325
326 if (q > relaxed && q[-1] == ' ') q--; /* Squash eventual trailing SP */
327
328 if (crlf) { *q++ = '\r'; *q++ = '\n'; }
329 *q = '\0';
330 return relaxed;
331 }
332
333
334 /* -------------------------------------------------------------------------- */
335 #define PDKIM_QP_ERROR_DECODE -1
336
337 static uschar *
338 pdkim_decode_qp_char(uschar *qp_p, int *c)
339 {
340 uschar *initial_pos = qp_p;
341
342 /* Advance one char */
343 qp_p++;
344
345 /* Check for two hex digits and decode them */
346 if (isxdigit(*qp_p) && isxdigit(qp_p[1]))
347 {
348 /* Do hex conversion */
349 *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) << 4;
350 *c |= isdigit(qp_p[1]) ? qp_p[1] - '0' : toupper(qp_p[1]) - 'A' + 10;
351 return qp_p + 2;
352 }
353
354 /* Illegal char here */
355 *c = PDKIM_QP_ERROR_DECODE;
356 return initial_pos;
357 }
358
359
360 /* -------------------------------------------------------------------------- */
361
362 static uschar *
363 pdkim_decode_qp(uschar * str)
364 {
365 int nchar = 0;
366 uschar * q;
367 uschar * p = str;
368 uschar * n = store_get(Ustrlen(str)+1);
369
370 *n = '\0';
371 q = n;
372 while (*p)
373 {
374 if (*p == '=')
375 {
376 p = pdkim_decode_qp_char(p, &nchar);
377 if (nchar >= 0)
378 {
379 *q++ = nchar;
380 continue;
381 }
382 }
383 else
384 *q++ = *p;
385 p++;
386 }
387 *q = '\0';
388 return n;
389 }
390
391
392 /* -------------------------------------------------------------------------- */
393
394 static void
395 pdkim_decode_base64(uschar *str, blob * b)
396 {
397 int dlen;
398 dlen = b64decode(str, &b->data);
399 if (dlen < 0) b->data = NULL;
400 b->len = dlen;
401 }
402
403 static uschar *
404 pdkim_encode_base64(blob * b)
405 {
406 return b64encode(b->data, b->len);
407 }
408
409
410 /* -------------------------------------------------------------------------- */
411 #define PDKIM_HDR_LIMBO 0
412 #define PDKIM_HDR_TAG 1
413 #define PDKIM_HDR_VALUE 2
414
415 static pdkim_signature *
416 pdkim_parse_sig_header(pdkim_ctx *ctx, uschar * raw_hdr)
417 {
418 pdkim_signature *sig ;
419 uschar *p, *q;
420 uschar * cur_tag = NULL; int ts = 0, tl = 0;
421 uschar * cur_val = NULL; int vs = 0, vl = 0;
422 BOOL past_hname = FALSE;
423 BOOL in_b_val = FALSE;
424 int where = PDKIM_HDR_LIMBO;
425 int i;
426
427 sig = store_get(sizeof(pdkim_signature));
428 memset(sig, 0, sizeof(pdkim_signature));
429 sig->bodylength = -1;
430
431 /* Set so invalid/missing data error display is accurate */
432 sig->algo = -1;
433 sig->version = 0;
434
435 q = sig->rawsig_no_b_val = store_get(Ustrlen(raw_hdr)+1);
436
437 for (p = raw_hdr; ; p++)
438 {
439 char c = *p;
440
441 /* Ignore FWS */
442 if (c == '\r' || c == '\n')
443 goto NEXT_CHAR;
444
445 /* Fast-forward through header name */
446 if (!past_hname)
447 {
448 if (c == ':') past_hname = TRUE;
449 goto NEXT_CHAR;
450 }
451
452 if (where == PDKIM_HDR_LIMBO)
453 {
454 /* In limbo, just wait for a tag-char to appear */
455 if (!(c >= 'a' && c <= 'z'))
456 goto NEXT_CHAR;
457
458 where = PDKIM_HDR_TAG;
459 }
460
461 if (where == PDKIM_HDR_TAG)
462 {
463 if (c >= 'a' && c <= 'z')
464 cur_tag = string_catn(cur_tag, &ts, &tl, p, 1);
465
466 if (c == '=')
467 {
468 cur_tag[tl] = '\0';
469 if (Ustrcmp(cur_tag, "b") == 0)
470 {
471 *q++ = '=';
472 in_b_val = TRUE;
473 }
474 where = PDKIM_HDR_VALUE;
475 goto NEXT_CHAR;
476 }
477 }
478
479 if (where == PDKIM_HDR_VALUE)
480 {
481 if (c == '\r' || c == '\n' || c == ' ' || c == '\t')
482 goto NEXT_CHAR;
483
484 if (c == ';' || c == '\0')
485 {
486 if (tl && vl)
487 {
488 cur_val[vl] = '\0';
489 pdkim_strtrim(cur_val);
490
491 DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag, cur_val);
492
493 switch (*cur_tag)
494 {
495 case 'b':
496 if (cur_tag[1] == 'h')
497 pdkim_decode_base64(cur_val, &sig->bodyhash);
498 else
499 pdkim_decode_base64(cur_val, &sig->sigdata);
500 break;
501 case 'v':
502 /* We only support version 1, and that is currently the
503 only version there is. */
504 sig->version =
505 Ustrcmp(cur_val, PDKIM_SIGNATURE_VERSION) == 0 ? 1 : -1;
506 break;
507 case 'a':
508 for (i = 0; pdkim_algos[i]; i++)
509 if (Ustrcmp(cur_val, pdkim_algos[i]) == 0)
510 {
511 sig->algo = i;
512 break;
513 }
514 break;
515 case 'c':
516 for (i = 0; pdkim_combined_canons[i].str; i++)
517 if (Ustrcmp(cur_val, pdkim_combined_canons[i].str) == 0)
518 {
519 sig->canon_headers = pdkim_combined_canons[i].canon_headers;
520 sig->canon_body = pdkim_combined_canons[i].canon_body;
521 break;
522 }
523 break;
524 case 'q':
525 for (i = 0; pdkim_querymethods[i]; i++)
526 if (Ustrcmp(cur_val, pdkim_querymethods[i]) == 0)
527 {
528 sig->querymethod = i;
529 break;
530 }
531 break;
532 case 's':
533 sig->selector = string_copy(cur_val); break;
534 case 'd':
535 sig->domain = string_copy(cur_val); break;
536 case 'i':
537 sig->identity = pdkim_decode_qp(cur_val); break;
538 case 't':
539 sig->created = strtoul(CS cur_val, NULL, 10); break;
540 case 'x':
541 sig->expires = strtoul(CS cur_val, NULL, 10); break;
542 case 'l':
543 sig->bodylength = strtol(CS cur_val, NULL, 10); break;
544 case 'h':
545 sig->headernames = string_copy(cur_val); break;
546 case 'z':
547 sig->copiedheaders = pdkim_decode_qp(cur_val); break;
548 default:
549 DEBUG(D_acl) debug_printf(" Unknown tag encountered\n");
550 break;
551 }
552 }
553 tl = 0;
554 vl = 0;
555 in_b_val = FALSE;
556 where = PDKIM_HDR_LIMBO;
557 }
558 else
559 cur_val = string_catn(cur_val, &vs, &vl, p, 1);
560 }
561
562 NEXT_CHAR:
563 if (c == '\0')
564 break;
565
566 if (!in_b_val)
567 *q++ = c;
568 }
569
570 *q = '\0';
571 /* Chomp raw header. The final newline must not be added to the signature. */
572 while (--q > sig->rawsig_no_b_val && (*q == '\r' || *q == '\n'))
573 *q = '\0';
574
575 DEBUG(D_acl)
576 {
577 debug_printf(
578 "PDKIM >> Raw signature w/o b= tag value >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
579 pdkim_quoteprint(US sig->rawsig_no_b_val, Ustrlen(sig->rawsig_no_b_val));
580 debug_printf(
581 "PDKIM >> Sig size: %4u bits\n", (unsigned) sig->sigdata.len*8);
582 debug_printf(
583 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
584 }
585
586 exim_sha_init(&sig->body_hash, sig->algo == PDKIM_ALGO_RSA_SHA1 ? HASH_SHA1 : HASH_SHA256);
587 return sig;
588 }
589
590
591 /* -------------------------------------------------------------------------- */
592
593 static pdkim_pubkey *
594 pdkim_parse_pubkey_record(pdkim_ctx *ctx, const uschar *raw_record)
595 {
596 pdkim_pubkey *pub;
597 const uschar *p;
598 uschar * cur_tag = NULL; int ts = 0, tl = 0;
599 uschar * cur_val = NULL; int vs = 0, vl = 0;
600 int where = PDKIM_HDR_LIMBO;
601
602 pub = store_get(sizeof(pdkim_pubkey));
603 memset(pub, 0, sizeof(pdkim_pubkey));
604
605 for (p = raw_record; ; p++)
606 {
607 uschar c = *p;
608
609 /* Ignore FWS */
610 if (c != '\r' && c != '\n') switch (where)
611 {
612 case PDKIM_HDR_LIMBO: /* In limbo, just wait for a tag-char to appear */
613 if (!(c >= 'a' && c <= 'z'))
614 break;
615 where = PDKIM_HDR_TAG;
616 /*FALLTHROUGH*/
617
618 case PDKIM_HDR_TAG:
619 if (c >= 'a' && c <= 'z')
620 cur_tag = string_catn(cur_tag, &ts, &tl, p, 1);
621
622 if (c == '=')
623 {
624 cur_tag[tl] = '\0';
625 where = PDKIM_HDR_VALUE;
626 }
627 break;
628
629 case PDKIM_HDR_VALUE:
630 if (c == ';' || c == '\0')
631 {
632 if (tl && vl)
633 {
634 cur_val[vl] = '\0';
635 pdkim_strtrim(cur_val);
636 DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag, cur_val);
637
638 switch (cur_tag[0])
639 {
640 case 'v':
641 pub->version = string_copy(cur_val); break;
642 case 'h':
643 case 'k':
644 /* This field appears to never be used. Also, unclear why
645 a 'k' (key-type_ would go in this field name. There is a field
646 "keytype", also never used.
647 pub->hashes = string_copy(cur_val);
648 */
649 break;
650 case 'g':
651 pub->granularity = string_copy(cur_val); break;
652 case 'n':
653 pub->notes = pdkim_decode_qp(cur_val); break;
654 case 'p':
655 pdkim_decode_base64(US cur_val, &pub->key); break;
656 case 's':
657 pub->srvtype = string_copy(cur_val); break;
658 case 't':
659 if (Ustrchr(cur_val, 'y') != NULL) pub->testing = 1;
660 if (Ustrchr(cur_val, 's') != NULL) pub->no_subdomaining = 1;
661 break;
662 default:
663 DEBUG(D_acl) debug_printf(" Unknown tag encountered\n");
664 break;
665 }
666 }
667 tl = 0;
668 vl = 0;
669 where = PDKIM_HDR_LIMBO;
670 }
671 else
672 cur_val = string_catn(cur_val, &vs, &vl, p, 1);
673 break;
674 }
675
676 if (c == '\0') break;
677 }
678
679 /* Set fallback defaults */
680 if (!pub->version ) pub->version = string_copy(PDKIM_PUB_RECORD_VERSION);
681 else if (Ustrcmp(pub->version, PDKIM_PUB_RECORD_VERSION) != 0) return NULL;
682
683 if (!pub->granularity) pub->granularity = string_copy(US"*");
684 /*
685 if (!pub->keytype ) pub->keytype = string_copy(US"rsa");
686 */
687 if (!pub->srvtype ) pub->srvtype = string_copy(US"*");
688
689 /* p= is required */
690 if (pub->key.data)
691 return pub;
692
693 return NULL;
694 }
695
696
697 /* -------------------------------------------------------------------------- */
698
699 static int
700 pdkim_update_bodyhash(pdkim_ctx *ctx, const char *data, int len)
701 {
702 pdkim_signature *sig = ctx->sig;
703 /* Cache relaxed version of data */
704 uschar *relaxed_data = NULL;
705 int relaxed_len = 0;
706
707 /* Traverse all signatures, updating their hashes. */
708 while (sig)
709 {
710 /* Defaults to simple canon (no further treatment necessary) */
711 const uschar *canon_data = CUS data;
712 int canon_len = len;
713
714 if (sig->canon_body == PDKIM_CANON_RELAXED)
715 {
716 /* Relax the line if not done already */
717 if (!relaxed_data)
718 {
719 BOOL seen_wsp = FALSE;
720 const char *p;
721 int q = 0;
722
723 /* We want to be able to free this else we allocate
724 for the entire message which could be many MB. Since
725 we don't know what allocations the SHA routines might
726 do, not safe to use store_get()/store_reset(). */
727
728 relaxed_data = store_malloc(len+1);
729
730 for (p = data; *p; p++)
731 {
732 char c = *p;
733 if (c == '\r')
734 {
735 if (q > 0 && relaxed_data[q-1] == ' ')
736 q--;
737 }
738 else if (c == '\t' || c == ' ')
739 {
740 c = ' '; /* Turns WSP into SP */
741 if (seen_wsp)
742 continue;
743 seen_wsp = TRUE;
744 }
745 else
746 seen_wsp = FALSE;
747 relaxed_data[q++] = c;
748 }
749 relaxed_data[q] = '\0';
750 relaxed_len = q;
751 }
752 canon_data = relaxed_data;
753 canon_len = relaxed_len;
754 }
755
756 /* Make sure we don't exceed the to-be-signed body length */
757 if ( sig->bodylength >= 0
758 && sig->signed_body_bytes + (unsigned long)canon_len > sig->bodylength
759 )
760 canon_len = sig->bodylength - sig->signed_body_bytes;
761
762 if (canon_len > 0)
763 {
764 exim_sha_update(&sig->body_hash, CUS canon_data, canon_len);
765 sig->signed_body_bytes += canon_len;
766 DEBUG(D_acl) pdkim_quoteprint(canon_data, canon_len);
767 }
768
769 sig = sig->next;
770 }
771
772 if (relaxed_data) store_free(relaxed_data);
773 return PDKIM_OK;
774 }
775
776
777 /* -------------------------------------------------------------------------- */
778
779 static void
780 pdkim_finish_bodyhash(pdkim_ctx *ctx)
781 {
782 pdkim_signature *sig;
783
784 /* Traverse all signatures */
785 for (sig = ctx->sig; sig; sig = sig->next)
786 { /* Finish hashes */
787 blob bh;
788
789 exim_sha_finish(&sig->body_hash, &bh);
790
791 DEBUG(D_acl)
792 {
793 debug_printf("PDKIM [%s] Body bytes hashed: %lu\n"
794 "PDKIM [%s] Body hash computed: ",
795 sig->domain, sig->signed_body_bytes, sig->domain);
796 pdkim_hexprint(CUS bh.data, bh.len);
797 }
798
799 /* SIGNING -------------------------------------------------------------- */
800 if (ctx->flags & PDKIM_MODE_SIGN)
801 {
802 sig->bodyhash = bh;
803
804 /* If bodylength limit is set, and we have received less bytes
805 than the requested amount, effectively remove the limit tag. */
806 if (sig->signed_body_bytes < sig->bodylength)
807 sig->bodylength = -1;
808 }
809
810 /* VERIFICATION --------------------------------------------------------- */
811 else
812 {
813 /* Compare bodyhash */
814 if (memcmp(bh.data, sig->bodyhash.data, bh.len) == 0)
815 {
816 DEBUG(D_acl) debug_printf("PDKIM [%s] Body hash verified OK\n", sig->domain);
817 }
818 else
819 {
820 DEBUG(D_acl)
821 {
822 debug_printf("PDKIM [%s] Body hash signature from headers: ", sig->domain);
823 pdkim_hexprint(sig->bodyhash.data,
824 exim_sha_hashlen(&sig->body_hash));
825 debug_printf("PDKIM [%s] Body hash did NOT verify\n", sig->domain);
826 }
827 sig->verify_status = PDKIM_VERIFY_FAIL;
828 sig->verify_ext_status = PDKIM_VERIFY_FAIL_BODY;
829 }
830 }
831 }
832 }
833
834
835
836 static int
837 pdkim_body_complete(pdkim_ctx * ctx)
838 {
839 pdkim_signature * sig = ctx->sig; /*XXX assumes only one sig */
840
841 /* In simple body mode, if any empty lines were buffered,
842 replace with one. rfc 4871 3.4.3 */
843 /*XXX checking the signed-body-bytes is a gross hack; I think
844 it indicates that all linebreaks should be buffered, including
845 the one terminating a text line */
846
847 if ( sig && sig->canon_body == PDKIM_CANON_SIMPLE
848 && sig->signed_body_bytes == 0
849 && ctx->num_buffered_crlf > 0
850 )
851 pdkim_update_bodyhash(ctx, "\r\n", 2);
852
853 ctx->flags |= PDKIM_SEEN_EOD;
854 ctx->linebuf_offset = 0;
855 return PDKIM_OK;
856 }
857
858
859
860 /* -------------------------------------------------------------------------- */
861 /* Call from pdkim_feed below for processing complete body lines */
862
863 static int
864 pdkim_bodyline_complete(pdkim_ctx *ctx)
865 {
866 char *p = ctx->linebuf;
867 int n = ctx->linebuf_offset;
868 pdkim_signature *sig = ctx->sig; /*XXX assumes only one sig */
869
870 /* Ignore extra data if we've seen the end-of-data marker */
871 if (ctx->flags & PDKIM_SEEN_EOD) goto BAIL;
872
873 /* We've always got one extra byte to stuff a zero ... */
874 ctx->linebuf[ctx->linebuf_offset] = '\0';
875
876 /* Terminate on EOD marker */
877 if (ctx->flags & PDKIM_DOT_TERM)
878 {
879 if ( memcmp(p, ".\r\n", 3) == 0)
880 return pdkim_body_complete(ctx);
881
882 /* Unstuff dots */
883 if (memcmp(p, "..", 2) == 0)
884 {
885 p++;
886 n--;
887 }
888 }
889
890 /* Empty lines need to be buffered until we find a non-empty line */
891 if (memcmp(p, "\r\n", 2) == 0)
892 {
893 ctx->num_buffered_crlf++;
894 goto BAIL;
895 }
896
897 if (sig && sig->canon_body == PDKIM_CANON_RELAXED)
898 {
899 /* Lines with just spaces need to be buffered too */
900 char *check = p;
901 while (memcmp(check, "\r\n", 2) != 0)
902 {
903 char c = *check;
904
905 if (c != '\t' && c != ' ')
906 goto PROCESS;
907 check++;
908 }
909
910 ctx->num_buffered_crlf++;
911 goto BAIL;
912 }
913
914 PROCESS:
915 /* At this point, we have a non-empty line, so release the buffered ones. */
916 while (ctx->num_buffered_crlf)
917 {
918 pdkim_update_bodyhash(ctx, "\r\n", 2);
919 ctx->num_buffered_crlf--;
920 }
921
922 pdkim_update_bodyhash(ctx, p, n);
923
924 BAIL:
925 ctx->linebuf_offset = 0;
926 return PDKIM_OK;
927 }
928
929
930 /* -------------------------------------------------------------------------- */
931 /* Callback from pdkim_feed below for processing complete headers */
932 #define DKIM_SIGNATURE_HEADERNAME "DKIM-Signature:"
933
934 static int
935 pdkim_header_complete(pdkim_ctx *ctx)
936 {
937 /* Special case: The last header can have an extra \r appended */
938 if ( (ctx->cur_header_len > 1) &&
939 (ctx->cur_header[(ctx->cur_header_len)-1] == '\r') )
940 --ctx->cur_header_len;
941 ctx->cur_header[ctx->cur_header_len] = '\0';
942
943 ctx->num_headers++;
944 if (ctx->num_headers > PDKIM_MAX_HEADERS) goto BAIL;
945
946 /* SIGNING -------------------------------------------------------------- */
947 if (ctx->flags & PDKIM_MODE_SIGN)
948 {
949 pdkim_signature *sig;
950
951 for (sig = ctx->sig; sig; sig = sig->next) /* Traverse all signatures */
952
953 /* Add header to the signed headers list (in reverse order) */
954 sig->headers = pdkim_prepend_stringlist(sig->headers,
955 ctx->cur_header);
956 }
957
958 /* VERIFICATION ----------------------------------------------------------- */
959 /* DKIM-Signature: headers are added to the verification list */
960 else
961 {
962 if (strncasecmp(CCS ctx->cur_header,
963 DKIM_SIGNATURE_HEADERNAME,
964 Ustrlen(DKIM_SIGNATURE_HEADERNAME)) == 0)
965 {
966 pdkim_signature *new_sig;
967
968 /* Create and chain new signature block */
969 DEBUG(D_acl) debug_printf(
970 "PDKIM >> Found sig, trying to parse >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
971
972 if ((new_sig = pdkim_parse_sig_header(ctx, ctx->cur_header)))
973 {
974 pdkim_signature *last_sig = ctx->sig;
975 if (!last_sig)
976 ctx->sig = new_sig;
977 else
978 {
979 while (last_sig->next) last_sig = last_sig->next;
980 last_sig->next = new_sig;
981 }
982 }
983 else
984 DEBUG(D_acl) debug_printf(
985 "Error while parsing signature header\n"
986 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
987 }
988
989 /* every other header is stored for signature verification */
990 else
991 ctx->headers = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header);
992 }
993
994 BAIL:
995 *ctx->cur_header = '\0';
996 ctx->cur_header_len = 0; /* leave buffer for reuse */
997 return PDKIM_OK;
998 }
999
1000
1001
1002 /* -------------------------------------------------------------------------- */
1003 #define HEADER_BUFFER_FRAG_SIZE 256
1004
1005 DLLEXPORT int
1006 pdkim_feed(pdkim_ctx *ctx, char *data, int len)
1007 {
1008 int p;
1009
1010 /* Alternate EOD signal, used in non-dotstuffing mode */
1011 if (!data)
1012 pdkim_body_complete(ctx);
1013
1014 else for (p = 0; p<len; p++)
1015 {
1016 uschar c = data[p];
1017
1018 if (ctx->flags & PDKIM_PAST_HDRS)
1019 {
1020 /* Processing body byte */
1021 ctx->linebuf[ctx->linebuf_offset++] = c;
1022 if (c == '\n')
1023 {
1024 int rc = pdkim_bodyline_complete(ctx); /* End of line */
1025 if (rc != PDKIM_OK) return rc;
1026 }
1027 if (ctx->linebuf_offset == (PDKIM_MAX_BODY_LINE_LEN-1))
1028 return PDKIM_ERR_LONG_LINE;
1029 }
1030 else
1031 {
1032 /* Processing header byte */
1033 if (c != '\r')
1034 {
1035 if (c == '\n')
1036 {
1037 if (ctx->flags & PDKIM_SEEN_LF)
1038 {
1039 int rc = pdkim_header_complete(ctx); /* Seen last header line */
1040 if (rc != PDKIM_OK) return rc;
1041
1042 ctx->flags = ctx->flags & ~PDKIM_SEEN_LF | PDKIM_PAST_HDRS;
1043 DEBUG(D_acl) debug_printf(
1044 "PDKIM >> Body data for hash, canonicalized >>>>>>>>>>>>>>>>>>>>>>\n");
1045 continue;
1046 }
1047 else
1048 ctx->flags |= PDKIM_SEEN_LF;
1049 }
1050 else if (ctx->flags & PDKIM_SEEN_LF)
1051 {
1052 if (!(c == '\t' || c == ' '))
1053 {
1054 int rc = pdkim_header_complete(ctx); /* End of header */
1055 if (rc != PDKIM_OK) return rc;
1056 }
1057 ctx->flags &= ~PDKIM_SEEN_LF;
1058 }
1059 }
1060
1061 if (ctx->cur_header_len < PDKIM_MAX_HEADER_LEN)
1062 ctx->cur_header = string_catn(ctx->cur_header, &ctx->cur_header_size,
1063 &ctx->cur_header_len, CUS &data[p], 1);
1064 }
1065 }
1066 return PDKIM_OK;
1067 }
1068
1069
1070
1071 /* Extend a grwong header with a continuation-linebreak */
1072 static uschar *
1073 pdkim_hdr_cont(uschar * str, int * size, int * ptr, int * col)
1074 {
1075 *col = 1;
1076 return string_catn(str, size, ptr, US"\r\n\t", 3);
1077 }
1078
1079
1080
1081 /*
1082 * RFC 5322 specifies that header line length SHOULD be no more than 78
1083 * lets make it so!
1084 * pdkim_headcat
1085 *
1086 * returns uschar * (not nul-terminated)
1087 *
1088 * col: this int holds and receives column number (octets since last '\n')
1089 * str: partial string to append to
1090 * size: current buffer size for str
1091 * ptr: current tail-pointer for str
1092 * pad: padding, split line or space after before or after eg: ";"
1093 * intro: - must join to payload eg "h=", usually the tag name
1094 * payload: eg base64 data - long data can be split arbitrarily.
1095 *
1096 * this code doesn't fold the header in some of the places that RFC4871
1097 * allows: As per RFC5322(2.2.3) it only folds before or after tag-value
1098 * pairs and inside long values. it also always spaces or breaks after the
1099 * "pad"
1100 *
1101 * no guarantees are made for output given out-of range input. like tag
1102 * names longer than 78, or bogus col. Input is assumed to be free of line breaks.
1103 */
1104
1105 static uschar *
1106 pdkim_headcat(int * col, uschar * str, int * size, int * ptr,
1107 const uschar * pad, const uschar * intro, const uschar * payload)
1108 {
1109 size_t l;
1110
1111 if (pad)
1112 {
1113 l = Ustrlen(pad);
1114 if (*col + l > 78)
1115 str = pdkim_hdr_cont(str, size, ptr, col);
1116 str = string_catn(str, size, ptr, pad, l);
1117 *col += l;
1118 }
1119
1120 l = (pad?1:0) + (intro?Ustrlen(intro):0);
1121
1122 if (*col + l > 78)
1123 { /*can't fit intro - start a new line to make room.*/
1124 str = pdkim_hdr_cont(str, size, ptr, col);
1125 l = intro?Ustrlen(intro):0;
1126 }
1127
1128 l += payload ? Ustrlen(payload):0 ;
1129
1130 while (l>77)
1131 { /* this fragment will not fit on a single line */
1132 if (pad)
1133 {
1134 str = string_catn(str, size, ptr, US" ", 1);
1135 *col += 1;
1136 pad = NULL; /* only want this once */
1137 l--;
1138 }
1139
1140 if (intro)
1141 {
1142 size_t sl = Ustrlen(intro);
1143
1144 str = string_catn(str, size, ptr, intro, sl);
1145 *col += sl;
1146 l -= sl;
1147 intro = NULL; /* only want this once */
1148 }
1149
1150 if (payload)
1151 {
1152 size_t sl = Ustrlen(payload);
1153 size_t chomp = *col+sl < 77 ? sl : 78-*col;
1154
1155 str = string_catn(str, size, ptr, payload, chomp);
1156 *col += chomp;
1157 payload += chomp;
1158 l -= chomp-1;
1159 }
1160
1161 /* the while precondition tells us it didn't fit. */
1162 str = pdkim_hdr_cont(str, size, ptr, col);
1163 }
1164
1165 if (*col + l > 78)
1166 {
1167 str = pdkim_hdr_cont(str, size, ptr, col);
1168 pad = NULL;
1169 }
1170
1171 if (pad)
1172 {
1173 str = string_catn(str, size, ptr, US" ", 1);
1174 *col += 1;
1175 pad = NULL;
1176 }
1177
1178 if (intro)
1179 {
1180 size_t sl = Ustrlen(intro);
1181
1182 str = string_catn(str, size, ptr, intro, sl);
1183 *col += sl;
1184 l -= sl;
1185 intro = NULL;
1186 }
1187
1188 if (payload)
1189 {
1190 size_t sl = Ustrlen(payload);
1191
1192 str = string_catn(str, size, ptr, payload, sl);
1193 *col += sl;
1194 }
1195
1196 return str;
1197 }
1198
1199
1200 /* -------------------------------------------------------------------------- */
1201
1202 static uschar *
1203 pdkim_create_header(pdkim_signature *sig, BOOL final)
1204 {
1205 uschar * base64_bh;
1206 uschar * base64_b;
1207 int col = 0;
1208 uschar * hdr; int hdr_size = 0, hdr_len = 0;
1209 uschar * canon_all; int can_size = 0, can_len = 0;
1210
1211 canon_all = string_cat (NULL, &can_size, &can_len,
1212 pdkim_canons[sig->canon_headers]);
1213 canon_all = string_catn(canon_all, &can_size, &can_len, US"/", 1);
1214 canon_all = string_cat (canon_all, &can_size, &can_len,
1215 pdkim_canons[sig->canon_body]);
1216 canon_all[can_len] = '\0';
1217
1218 hdr = string_cat(NULL, &hdr_size, &hdr_len,
1219 US"DKIM-Signature: v="PDKIM_SIGNATURE_VERSION);
1220 col = hdr_len;
1221
1222 /* Required and static bits */
1223 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"a=",
1224 pdkim_algos[sig->algo]);
1225 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"q=",
1226 pdkim_querymethods[sig->querymethod]);
1227 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"c=",
1228 canon_all);
1229 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"d=",
1230 sig->domain);
1231 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"s=",
1232 sig->selector);
1233
1234 /* list of header names can be split between items. */
1235 {
1236 uschar * n = string_copy(sig->headernames);
1237 uschar * i = US"h=";
1238 uschar * s = US";";
1239
1240 while (*n)
1241 {
1242 uschar * c = Ustrchr(n, ':');
1243
1244 if (c) *c ='\0';
1245
1246 if (!i)
1247 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, NULL, NULL, US":");
1248
1249 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, s, i, n);
1250
1251 if (!c)
1252 break;
1253
1254 n = c+1;
1255 s = NULL;
1256 i = NULL;
1257 }
1258 }
1259
1260 base64_bh = pdkim_encode_base64(&sig->bodyhash);
1261 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"bh=", base64_bh);
1262
1263 /* Optional bits */
1264 if (sig->identity)
1265 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"i=", sig->identity);
1266
1267 if (sig->created > 0)
1268 {
1269 uschar minibuf[20];
1270
1271 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->created);
1272 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"t=", minibuf);
1273 }
1274
1275 if (sig->expires > 0)
1276 {
1277 uschar minibuf[20];
1278
1279 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->expires);
1280 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"x=", minibuf);
1281 }
1282
1283 if (sig->bodylength >= 0)
1284 {
1285 uschar minibuf[20];
1286
1287 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->bodylength);
1288 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"l=", minibuf);
1289 }
1290
1291 /* Preliminary or final version? */
1292 base64_b = final ? pdkim_encode_base64(&sig->sigdata) : US"";
1293 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"b=", base64_b);
1294
1295 /* add trailing semicolon: I'm not sure if this is actually needed */
1296 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, NULL, US";", US"");
1297
1298 hdr[hdr_len] = '\0';
1299 return hdr;
1300 }
1301
1302
1303 /* -------------------------------------------------------------------------- */
1304
1305 static pdkim_pubkey *
1306 pdkim_key_from_dns(pdkim_ctx * ctx, pdkim_signature * sig, ev_ctx * vctx)
1307 {
1308 uschar * dns_txt_name, * dns_txt_reply;
1309 pdkim_pubkey * p;
1310 const uschar * errstr;
1311
1312 /* Fetch public key for signing domain, from DNS */
1313
1314 dns_txt_name = string_sprintf("%s._domainkey.%s.", sig->selector, sig->domain);
1315
1316 dns_txt_reply = store_get(PDKIM_DNS_TXT_MAX_RECLEN);
1317 memset(dns_txt_reply, 0, PDKIM_DNS_TXT_MAX_RECLEN);
1318
1319 if ( ctx->dns_txt_callback(CS dns_txt_name, CS dns_txt_reply) != PDKIM_OK
1320 || dns_txt_reply[0] == '\0'
1321 )
1322 {
1323 sig->verify_status = PDKIM_VERIFY_INVALID;
1324 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE;
1325 return NULL;
1326 }
1327
1328 DEBUG(D_acl)
1329 {
1330 debug_printf(
1331 "PDKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"
1332 " Raw record: ");
1333 pdkim_quoteprint(CUS dns_txt_reply, Ustrlen(dns_txt_reply));
1334 }
1335
1336 if ( !(p = pdkim_parse_pubkey_record(ctx, CUS dns_txt_reply))
1337 || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0)
1338 )
1339 {
1340 sig->verify_status = PDKIM_VERIFY_INVALID;
1341 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD;
1342
1343 DEBUG(D_acl)
1344 {
1345 if (p)
1346 debug_printf(" Invalid public key service type '%s'\n", p->srvtype);
1347 else
1348 debug_printf(" Error while parsing public key record\n");
1349 debug_printf(
1350 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1351 }
1352 return NULL;
1353 }
1354
1355 DEBUG(D_acl) debug_printf(
1356 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1357
1358 /* Import public key */
1359 if ((errstr = exim_rsa_verify_init(&p->key, vctx)))
1360 {
1361 DEBUG(D_acl) debug_printf("verify_init: %s\n", errstr);
1362 sig->verify_status = PDKIM_VERIFY_INVALID;
1363 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT;
1364 return NULL;
1365 }
1366
1367 return p;
1368 }
1369
1370
1371 /* -------------------------------------------------------------------------- */
1372
1373 DLLEXPORT int
1374 pdkim_feed_finish(pdkim_ctx *ctx, pdkim_signature **return_signatures)
1375 {
1376 pdkim_signature *sig = ctx->sig;
1377
1378 /* Check if we must still flush a (partial) header. If that is the
1379 case, the message has no body, and we must compute a body hash
1380 out of '<CR><LF>' */
1381 if (ctx->cur_header && ctx->cur_header_len)
1382 {
1383 int rc = pdkim_header_complete(ctx);
1384 if (rc != PDKIM_OK) return rc;
1385 pdkim_update_bodyhash(ctx, "\r\n", 2);
1386 }
1387 else
1388 DEBUG(D_acl) debug_printf(
1389 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1390
1391 /* Build (and/or evaluate) body hash */
1392 pdkim_finish_bodyhash(ctx);
1393
1394 while (sig)
1395 {
1396 BOOL is_sha1 = sig->algo == PDKIM_ALGO_RSA_SHA1;
1397 hctx hhash_ctx;
1398 uschar * sig_hdr = US"";
1399 blob hhash;
1400 blob hdata;
1401 int hdata_alloc = 0;
1402
1403 hdata.data = NULL;
1404 hdata.len = 0;
1405
1406 exim_sha_init(&hhash_ctx, is_sha1 ? HASH_SHA1 : HASH_SHA256);
1407
1408 DEBUG(D_acl) debug_printf(
1409 "PDKIM >> Header data for hash, canonicalized, in sequence >>>>>>>>>>>>>>\n");
1410
1411 /* SIGNING ---------------------------------------------------------------- */
1412 /* When signing, walk through our header list and add them to the hash. As we
1413 go, construct a list of the header's names to use for the h= parameter.
1414 Then append to that list any remaining header names for which there was no
1415 header to sign. */
1416
1417 if (ctx->flags & PDKIM_MODE_SIGN)
1418 {
1419 uschar * headernames = NULL; /* Collected signed header names */
1420 int hs = 0, hl = 0;
1421 pdkim_stringlist *p;
1422 const uschar * l;
1423 uschar * s;
1424 int sep = 0;
1425
1426 for (p = sig->headers; p; p = p->next)
1427 if (header_name_match(p->value, sig->sign_headers) == PDKIM_OK)
1428 {
1429 uschar * rh;
1430 /* Collect header names (Note: colon presence is guaranteed here) */
1431 uschar * q = Ustrchr(p->value, ':');
1432
1433 headernames = string_catn(headernames, &hs, &hl,
1434 p->value, (q - US p->value) + (p->next ? 1 : 0));
1435
1436 rh = sig->canon_headers == PDKIM_CANON_RELAXED
1437 ? pdkim_relax_header(p->value, 1) /* cook header for relaxed canon */
1438 : string_copy(CUS p->value); /* just copy it for simple canon */
1439
1440 /* Feed header to the hash algorithm */
1441 exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh));
1442
1443 /* Remember headers block for signing (when the library cannot do incremental) */
1444 (void) exim_rsa_data_append(&hdata, &hdata_alloc, rh);
1445
1446 DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh));
1447 }
1448
1449 l = sig->sign_headers;
1450 while((s = string_nextinlist(&l, &sep, NULL, 0)))
1451 if (*s != '_')
1452 { /*SSS string_append_listele() */
1453 if (hl > 0 && headernames[hl-1] != ':')
1454 headernames = string_catn(headernames, &hs, &hl, US":", 1);
1455
1456 headernames = string_cat(headernames, &hs, &hl, s);
1457 }
1458 headernames[hl] = '\0';
1459
1460 /* Copy headernames to signature struct */
1461 sig->headernames = headernames;
1462
1463 /* Create signature header with b= omitted */
1464 sig_hdr = pdkim_create_header(sig, FALSE);
1465 }
1466
1467 /* VERIFICATION ----------------------------------------------------------- */
1468 /* When verifying, walk through the header name list in the h= parameter and
1469 add the headers to the hash in that order. */
1470 else
1471 {
1472 uschar * p = sig->headernames;
1473 uschar * q;
1474 pdkim_stringlist * hdrs;
1475
1476 if (p)
1477 {
1478 /* clear tags */
1479 for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
1480 hdrs->tag = 0;
1481
1482 p = string_copy(p);
1483 while(1)
1484 {
1485 if ((q = Ustrchr(p, ':')))
1486 *q = '\0';
1487
1488 /*XXX walk the list of headers in same order as received. */
1489 for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
1490 if ( hdrs->tag == 0
1491 && strncasecmp(CCS hdrs->value, CCS p, Ustrlen(p)) == 0
1492 && (hdrs->value)[Ustrlen(p)] == ':'
1493 )
1494 {
1495 /* cook header for relaxed canon, or just copy it for simple */
1496
1497 uschar * rh = sig->canon_headers == PDKIM_CANON_RELAXED
1498 ? pdkim_relax_header(hdrs->value, 1)
1499 : string_copy(CUS hdrs->value);
1500
1501 /* Feed header to the hash algorithm */
1502 exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh));
1503
1504 DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh));
1505 hdrs->tag = 1;
1506 break;
1507 }
1508
1509 if (!q) break;
1510 p = q+1;
1511 }
1512
1513 sig_hdr = string_copy(sig->rawsig_no_b_val);
1514 }
1515 }
1516
1517 DEBUG(D_acl) debug_printf(
1518 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1519
1520 /* Relax header if necessary */
1521 if (sig->canon_headers == PDKIM_CANON_RELAXED)
1522 sig_hdr = pdkim_relax_header(sig_hdr, 0);
1523
1524 DEBUG(D_acl)
1525 {
1526 debug_printf(
1527 "PDKIM >> Signed DKIM-Signature header, canonicalized >>>>>>>>>>>>>>>>>\n");
1528 pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr));
1529 debug_printf(
1530 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1531 }
1532
1533 /* Finalize header hash */
1534 exim_sha_update(&hhash_ctx, CUS sig_hdr, Ustrlen(sig_hdr));
1535 exim_sha_finish(&hhash_ctx, &hhash);
1536
1537 DEBUG(D_acl)
1538 {
1539 debug_printf("PDKIM [%s] Header hash computed: ", sig->domain);
1540 pdkim_hexprint(hhash.data, hhash.len);
1541 }
1542
1543 /* Remember headers block for signing (when the library cannot do incremental) */
1544 if (ctx->flags & PDKIM_MODE_SIGN)
1545 (void) exim_rsa_data_append(&hdata, &hdata_alloc, US sig_hdr);
1546
1547 /* SIGNING ---------------------------------------------------------------- */
1548 if (ctx->flags & PDKIM_MODE_SIGN)
1549 {
1550 es_ctx sctx;
1551 const uschar * errstr;
1552
1553 /* Import private key */
1554 if ((errstr = exim_rsa_signing_init(US sig->rsa_privkey, &sctx)))
1555 {
1556 DEBUG(D_acl) debug_printf("signing_init: %s\n", errstr);
1557 return PDKIM_ERR_RSA_PRIVKEY;
1558 }
1559
1560 /* Do signing. With OpenSSL we are signing the hash of headers just
1561 calculated, with GnuTLS we have to sign an entire block of headers
1562 (due to available interfaces) and it recalculates the hash internally. */
1563
1564 #if defined(RSA_OPENSSL) || defined(RSA_GCRYPT)
1565 hdata = hhash;
1566 #endif
1567
1568 if ((errstr = exim_rsa_sign(&sctx, is_sha1, &hdata, &sig->sigdata)))
1569 {
1570 DEBUG(D_acl) debug_printf("signing: %s\n", errstr);
1571 return PDKIM_ERR_RSA_SIGNING;
1572 }
1573
1574 DEBUG(D_acl)
1575 {
1576 debug_printf( "PDKIM [%s] b computed: ", sig->domain);
1577 pdkim_hexprint(sig->sigdata.data, sig->sigdata.len);
1578 }
1579
1580 sig->signature_header = pdkim_create_header(sig, TRUE);
1581 }
1582
1583 /* VERIFICATION ----------------------------------------------------------- */
1584 else
1585 {
1586 ev_ctx vctx;
1587 const uschar * errstr;
1588 pdkim_pubkey * p;
1589
1590 /* Make sure we have all required signature tags */
1591 if (!( sig->domain && *sig->domain
1592 && sig->selector && *sig->selector
1593 && sig->headernames && *sig->headernames
1594 && sig->bodyhash.data
1595 && sig->sigdata.data
1596 && sig->algo > -1
1597 && sig->version
1598 ) )
1599 {
1600 sig->verify_status = PDKIM_VERIFY_INVALID;
1601 sig->verify_ext_status = PDKIM_VERIFY_INVALID_SIGNATURE_ERROR;
1602
1603 DEBUG(D_acl) debug_printf(
1604 " Error in DKIM-Signature header: tags missing or invalid\n"
1605 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1606 goto NEXT_VERIFY;
1607 }
1608
1609 /* Make sure sig uses supported DKIM version (only v1) */
1610 if (sig->version != 1)
1611 {
1612 sig->verify_status = PDKIM_VERIFY_INVALID;
1613 sig->verify_ext_status = PDKIM_VERIFY_INVALID_DKIM_VERSION;
1614
1615 DEBUG(D_acl) debug_printf(
1616 " Error in DKIM-Signature header: unsupported DKIM version\n"
1617 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1618 goto NEXT_VERIFY;
1619 }
1620
1621 if (!(sig->pubkey = pdkim_key_from_dns(ctx, sig, &vctx)))
1622 goto NEXT_VERIFY;
1623
1624 /* Check the signature */
1625 if ((errstr = exim_rsa_verify(&vctx, is_sha1, &hhash, &sig->sigdata)))
1626 {
1627 DEBUG(D_acl) debug_printf("headers verify: %s\n", errstr);
1628 sig->verify_status = PDKIM_VERIFY_FAIL;
1629 sig->verify_ext_status = PDKIM_VERIFY_FAIL_MESSAGE;
1630 goto NEXT_VERIFY;
1631 }
1632
1633
1634 /* We have a winner! (if bodydhash was correct earlier) */
1635 if (sig->verify_status == PDKIM_VERIFY_NONE)
1636 sig->verify_status = PDKIM_VERIFY_PASS;
1637
1638 NEXT_VERIFY:
1639
1640 DEBUG(D_acl)
1641 {
1642 debug_printf("PDKIM [%s] signature status: %s",
1643 sig->domain, pdkim_verify_status_str(sig->verify_status));
1644 if (sig->verify_ext_status > 0)
1645 debug_printf(" (%s)\n",
1646 pdkim_verify_ext_status_str(sig->verify_ext_status));
1647 else
1648 debug_printf("\n");
1649 }
1650 }
1651
1652 sig = sig->next;
1653 }
1654
1655 /* If requested, set return pointer to signature(s) */
1656 if (return_signatures)
1657 *return_signatures = ctx->sig;
1658
1659 return PDKIM_OK;
1660 }
1661
1662
1663 /* -------------------------------------------------------------------------- */
1664
1665 DLLEXPORT pdkim_ctx *
1666 pdkim_init_verify(int(*dns_txt_callback)(char *, char *), BOOL dot_stuffing)
1667 {
1668 pdkim_ctx * ctx;
1669
1670 ctx = store_get(sizeof(pdkim_ctx));
1671 memset(ctx, 0, sizeof(pdkim_ctx));
1672
1673 if (dot_stuffing) ctx->flags = PDKIM_DOT_TERM;
1674 ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN);
1675 ctx->dns_txt_callback = dns_txt_callback;
1676
1677 return ctx;
1678 }
1679
1680
1681 /* -------------------------------------------------------------------------- */
1682
1683 DLLEXPORT pdkim_ctx *
1684 pdkim_init_sign(char * domain, char * selector, char * rsa_privkey, int algo,
1685 BOOL dot_stuffed, int(*dns_txt_callback)(char *, char *))
1686 {
1687 pdkim_ctx * ctx;
1688 pdkim_signature * sig;
1689
1690 if (!domain || !selector || !rsa_privkey)
1691 return NULL;
1692
1693 ctx = store_get(sizeof(pdkim_ctx) + PDKIM_MAX_BODY_LINE_LEN + sizeof(pdkim_signature));
1694 memset(ctx, 0, sizeof(pdkim_ctx));
1695
1696 ctx->flags = dot_stuffed ? PDKIM_MODE_SIGN | PDKIM_DOT_TERM : PDKIM_MODE_SIGN;
1697 ctx->linebuf = CS (ctx+1);
1698
1699 DEBUG(D_acl) ctx->dns_txt_callback = dns_txt_callback;
1700
1701 sig = (pdkim_signature *)(ctx->linebuf + PDKIM_MAX_BODY_LINE_LEN);
1702 memset(sig, 0, sizeof(pdkim_signature));
1703
1704 sig->bodylength = -1;
1705 ctx->sig = sig;
1706
1707 sig->domain = string_copy(US domain);
1708 sig->selector = string_copy(US selector);
1709 sig->rsa_privkey = string_copy(US rsa_privkey);
1710 sig->algo = algo;
1711
1712 exim_sha_init(&sig->body_hash, algo == PDKIM_ALGO_RSA_SHA1 ? HASH_SHA1 : HASH_SHA256);
1713
1714 DEBUG(D_acl)
1715 {
1716 pdkim_signature s = *sig;
1717 ev_ctx vctx;
1718
1719 debug_printf("PDKIM (checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1720 if (!pdkim_key_from_dns(ctx, &s, &vctx))
1721 debug_printf("WARNING: bad dkim key in dns\n");
1722 debug_printf("PDKIM (finished checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1723 }
1724
1725 return ctx;
1726 }
1727
1728
1729 /* -------------------------------------------------------------------------- */
1730
1731 DLLEXPORT int
1732 pdkim_set_optional(pdkim_ctx *ctx,
1733 char *sign_headers,
1734 char *identity,
1735 int canon_headers,
1736 int canon_body,
1737 long bodylength,
1738 unsigned long created,
1739 unsigned long expires)
1740 {
1741 pdkim_signature * sig = ctx->sig;
1742
1743 if (identity)
1744 sig->identity = string_copy(US identity);
1745
1746 sig->sign_headers = string_copy(sign_headers
1747 ? US sign_headers : US PDKIM_DEFAULT_SIGN_HEADERS);
1748
1749 sig->canon_headers = canon_headers;
1750 sig->canon_body = canon_body;
1751 sig->bodylength = bodylength;
1752 sig->created = created;
1753 sig->expires = expires;
1754
1755 return PDKIM_OK;
1756 }
1757
1758
1759 void
1760 pdkim_init(void)
1761 {
1762 exim_rsa_init();
1763 }
1764
1765
1766
1767 #endif /*DISABLE_DKIM*/
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