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Fix DKIM verify operation in -bh test mode. Bug 2017
[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 if (c == '\n' && !(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */
1021 {
1022 ctx->linebuf[ctx->linebuf_offset++] = '\r';
1023 if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1)
1024 return PDKIM_ERR_LONG_LINE;
1025 }
1026
1027 /* Processing body byte */
1028 ctx->linebuf[ctx->linebuf_offset++] = c;
1029 if (c == '\r')
1030 ctx->flags |= PDKIM_SEEN_CR;
1031 else if (c == '\n')
1032 {
1033 int rc;
1034 ctx->flags &= ~PDKIM_SEEN_CR;
1035 if ((rc = pdkim_bodyline_complete(ctx)) != PDKIM_OK)
1036 return rc;
1037 }
1038
1039 if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1)
1040 return PDKIM_ERR_LONG_LINE;
1041 }
1042 else
1043 {
1044 /* Processing header byte */
1045 if (c == '\r')
1046 ctx->flags |= PDKIM_SEEN_CR;
1047 else if (c == '\n')
1048 {
1049 if (!(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */
1050 ctx->cur_header = string_catn(ctx->cur_header, &ctx->cur_header_size,
1051 &ctx->cur_header_len, CUS "\r", 1);
1052
1053 if (ctx->flags & PDKIM_SEEN_LF)
1054 {
1055 int rc = pdkim_header_complete(ctx); /* Seen last header line */
1056 if (rc != PDKIM_OK) return rc;
1057
1058 ctx->flags = ctx->flags & ~(PDKIM_SEEN_LF|PDKIM_SEEN_CR) | PDKIM_PAST_HDRS;
1059 DEBUG(D_acl) debug_printf(
1060 "PDKIM >> Body data for hash, canonicalized >>>>>>>>>>>>>>>>>>>>>>\n");
1061 continue;
1062 }
1063 else
1064 ctx->flags = ctx->flags & ~PDKIM_SEEN_CR | PDKIM_SEEN_LF;
1065 }
1066 else if (ctx->flags & PDKIM_SEEN_LF)
1067 {
1068 if (!(c == '\t' || c == ' '))
1069 {
1070 int rc = pdkim_header_complete(ctx); /* End of header */
1071 if (rc != PDKIM_OK) return rc;
1072 }
1073 ctx->flags &= ~PDKIM_SEEN_LF;
1074 }
1075
1076 if (ctx->cur_header_len < PDKIM_MAX_HEADER_LEN)
1077 ctx->cur_header = string_catn(ctx->cur_header, &ctx->cur_header_size,
1078 &ctx->cur_header_len, CUS &data[p], 1);
1079 }
1080 }
1081 return PDKIM_OK;
1082 }
1083
1084
1085
1086 /* Extend a grwong header with a continuation-linebreak */
1087 static uschar *
1088 pdkim_hdr_cont(uschar * str, int * size, int * ptr, int * col)
1089 {
1090 *col = 1;
1091 return string_catn(str, size, ptr, US"\r\n\t", 3);
1092 }
1093
1094
1095
1096 /*
1097 * RFC 5322 specifies that header line length SHOULD be no more than 78
1098 * lets make it so!
1099 * pdkim_headcat
1100 *
1101 * returns uschar * (not nul-terminated)
1102 *
1103 * col: this int holds and receives column number (octets since last '\n')
1104 * str: partial string to append to
1105 * size: current buffer size for str
1106 * ptr: current tail-pointer for str
1107 * pad: padding, split line or space after before or after eg: ";"
1108 * intro: - must join to payload eg "h=", usually the tag name
1109 * payload: eg base64 data - long data can be split arbitrarily.
1110 *
1111 * this code doesn't fold the header in some of the places that RFC4871
1112 * allows: As per RFC5322(2.2.3) it only folds before or after tag-value
1113 * pairs and inside long values. it also always spaces or breaks after the
1114 * "pad"
1115 *
1116 * no guarantees are made for output given out-of range input. like tag
1117 * names longer than 78, or bogus col. Input is assumed to be free of line breaks.
1118 */
1119
1120 static uschar *
1121 pdkim_headcat(int * col, uschar * str, int * size, int * ptr,
1122 const uschar * pad, const uschar * intro, const uschar * payload)
1123 {
1124 size_t l;
1125
1126 if (pad)
1127 {
1128 l = Ustrlen(pad);
1129 if (*col + l > 78)
1130 str = pdkim_hdr_cont(str, size, ptr, col);
1131 str = string_catn(str, size, ptr, pad, l);
1132 *col += l;
1133 }
1134
1135 l = (pad?1:0) + (intro?Ustrlen(intro):0);
1136
1137 if (*col + l > 78)
1138 { /*can't fit intro - start a new line to make room.*/
1139 str = pdkim_hdr_cont(str, size, ptr, col);
1140 l = intro?Ustrlen(intro):0;
1141 }
1142
1143 l += payload ? Ustrlen(payload):0 ;
1144
1145 while (l>77)
1146 { /* this fragment will not fit on a single line */
1147 if (pad)
1148 {
1149 str = string_catn(str, size, ptr, US" ", 1);
1150 *col += 1;
1151 pad = NULL; /* only want this once */
1152 l--;
1153 }
1154
1155 if (intro)
1156 {
1157 size_t sl = Ustrlen(intro);
1158
1159 str = string_catn(str, size, ptr, intro, sl);
1160 *col += sl;
1161 l -= sl;
1162 intro = NULL; /* only want this once */
1163 }
1164
1165 if (payload)
1166 {
1167 size_t sl = Ustrlen(payload);
1168 size_t chomp = *col+sl < 77 ? sl : 78-*col;
1169
1170 str = string_catn(str, size, ptr, payload, chomp);
1171 *col += chomp;
1172 payload += chomp;
1173 l -= chomp-1;
1174 }
1175
1176 /* the while precondition tells us it didn't fit. */
1177 str = pdkim_hdr_cont(str, size, ptr, col);
1178 }
1179
1180 if (*col + l > 78)
1181 {
1182 str = pdkim_hdr_cont(str, size, ptr, col);
1183 pad = NULL;
1184 }
1185
1186 if (pad)
1187 {
1188 str = string_catn(str, size, ptr, US" ", 1);
1189 *col += 1;
1190 pad = NULL;
1191 }
1192
1193 if (intro)
1194 {
1195 size_t sl = Ustrlen(intro);
1196
1197 str = string_catn(str, size, ptr, intro, sl);
1198 *col += sl;
1199 l -= sl;
1200 intro = NULL;
1201 }
1202
1203 if (payload)
1204 {
1205 size_t sl = Ustrlen(payload);
1206
1207 str = string_catn(str, size, ptr, payload, sl);
1208 *col += sl;
1209 }
1210
1211 return str;
1212 }
1213
1214
1215 /* -------------------------------------------------------------------------- */
1216
1217 static uschar *
1218 pdkim_create_header(pdkim_signature *sig, BOOL final)
1219 {
1220 uschar * base64_bh;
1221 uschar * base64_b;
1222 int col = 0;
1223 uschar * hdr; int hdr_size = 0, hdr_len = 0;
1224 uschar * canon_all; int can_size = 0, can_len = 0;
1225
1226 canon_all = string_cat (NULL, &can_size, &can_len,
1227 pdkim_canons[sig->canon_headers]);
1228 canon_all = string_catn(canon_all, &can_size, &can_len, US"/", 1);
1229 canon_all = string_cat (canon_all, &can_size, &can_len,
1230 pdkim_canons[sig->canon_body]);
1231 canon_all[can_len] = '\0';
1232
1233 hdr = string_cat(NULL, &hdr_size, &hdr_len,
1234 US"DKIM-Signature: v="PDKIM_SIGNATURE_VERSION);
1235 col = hdr_len;
1236
1237 /* Required and static bits */
1238 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"a=",
1239 pdkim_algos[sig->algo]);
1240 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"q=",
1241 pdkim_querymethods[sig->querymethod]);
1242 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"c=",
1243 canon_all);
1244 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"d=",
1245 sig->domain);
1246 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"s=",
1247 sig->selector);
1248
1249 /* list of header names can be split between items. */
1250 {
1251 uschar * n = string_copy(sig->headernames);
1252 uschar * i = US"h=";
1253 uschar * s = US";";
1254
1255 while (*n)
1256 {
1257 uschar * c = Ustrchr(n, ':');
1258
1259 if (c) *c ='\0';
1260
1261 if (!i)
1262 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, NULL, NULL, US":");
1263
1264 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, s, i, n);
1265
1266 if (!c)
1267 break;
1268
1269 n = c+1;
1270 s = NULL;
1271 i = NULL;
1272 }
1273 }
1274
1275 base64_bh = pdkim_encode_base64(&sig->bodyhash);
1276 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"bh=", base64_bh);
1277
1278 /* Optional bits */
1279 if (sig->identity)
1280 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"i=", sig->identity);
1281
1282 if (sig->created > 0)
1283 {
1284 uschar minibuf[20];
1285
1286 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->created);
1287 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"t=", minibuf);
1288 }
1289
1290 if (sig->expires > 0)
1291 {
1292 uschar minibuf[20];
1293
1294 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->expires);
1295 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"x=", minibuf);
1296 }
1297
1298 if (sig->bodylength >= 0)
1299 {
1300 uschar minibuf[20];
1301
1302 snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->bodylength);
1303 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"l=", minibuf);
1304 }
1305
1306 /* Preliminary or final version? */
1307 base64_b = final ? pdkim_encode_base64(&sig->sigdata) : US"";
1308 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, US";", US"b=", base64_b);
1309
1310 /* add trailing semicolon: I'm not sure if this is actually needed */
1311 hdr = pdkim_headcat(&col, hdr, &hdr_size, &hdr_len, NULL, US";", US"");
1312
1313 hdr[hdr_len] = '\0';
1314 return hdr;
1315 }
1316
1317
1318 /* -------------------------------------------------------------------------- */
1319
1320 static pdkim_pubkey *
1321 pdkim_key_from_dns(pdkim_ctx * ctx, pdkim_signature * sig, ev_ctx * vctx)
1322 {
1323 uschar * dns_txt_name, * dns_txt_reply;
1324 pdkim_pubkey * p;
1325 const uschar * errstr;
1326
1327 /* Fetch public key for signing domain, from DNS */
1328
1329 dns_txt_name = string_sprintf("%s._domainkey.%s.", sig->selector, sig->domain);
1330
1331 dns_txt_reply = store_get(PDKIM_DNS_TXT_MAX_RECLEN);
1332 memset(dns_txt_reply, 0, PDKIM_DNS_TXT_MAX_RECLEN);
1333
1334 if ( ctx->dns_txt_callback(CS dns_txt_name, CS dns_txt_reply) != PDKIM_OK
1335 || dns_txt_reply[0] == '\0'
1336 )
1337 {
1338 sig->verify_status = PDKIM_VERIFY_INVALID;
1339 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE;
1340 return NULL;
1341 }
1342
1343 DEBUG(D_acl)
1344 {
1345 debug_printf(
1346 "PDKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"
1347 " Raw record: ");
1348 pdkim_quoteprint(CUS dns_txt_reply, Ustrlen(dns_txt_reply));
1349 }
1350
1351 if ( !(p = pdkim_parse_pubkey_record(ctx, CUS dns_txt_reply))
1352 || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0)
1353 )
1354 {
1355 sig->verify_status = PDKIM_VERIFY_INVALID;
1356 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD;
1357
1358 DEBUG(D_acl)
1359 {
1360 if (p)
1361 debug_printf(" Invalid public key service type '%s'\n", p->srvtype);
1362 else
1363 debug_printf(" Error while parsing public key record\n");
1364 debug_printf(
1365 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1366 }
1367 return NULL;
1368 }
1369
1370 DEBUG(D_acl) debug_printf(
1371 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1372
1373 /* Import public key */
1374 if ((errstr = exim_rsa_verify_init(&p->key, vctx)))
1375 {
1376 DEBUG(D_acl) debug_printf("verify_init: %s\n", errstr);
1377 sig->verify_status = PDKIM_VERIFY_INVALID;
1378 sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT;
1379 return NULL;
1380 }
1381
1382 return p;
1383 }
1384
1385
1386 /* -------------------------------------------------------------------------- */
1387
1388 DLLEXPORT int
1389 pdkim_feed_finish(pdkim_ctx *ctx, pdkim_signature **return_signatures)
1390 {
1391 pdkim_signature *sig = ctx->sig;
1392
1393 /* Check if we must still flush a (partial) header. If that is the
1394 case, the message has no body, and we must compute a body hash
1395 out of '<CR><LF>' */
1396 if (ctx->cur_header && ctx->cur_header_len)
1397 {
1398 int rc = pdkim_header_complete(ctx);
1399 if (rc != PDKIM_OK) return rc;
1400 pdkim_update_bodyhash(ctx, "\r\n", 2);
1401 }
1402 else
1403 DEBUG(D_acl) debug_printf(
1404 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1405
1406 /* Build (and/or evaluate) body hash */
1407 pdkim_finish_bodyhash(ctx);
1408
1409 while (sig)
1410 {
1411 BOOL is_sha1 = sig->algo == PDKIM_ALGO_RSA_SHA1;
1412 hctx hhash_ctx;
1413 uschar * sig_hdr = US"";
1414 blob hhash;
1415 blob hdata;
1416 int hdata_alloc = 0;
1417
1418 hdata.data = NULL;
1419 hdata.len = 0;
1420
1421 exim_sha_init(&hhash_ctx, is_sha1 ? HASH_SHA1 : HASH_SHA256);
1422
1423 DEBUG(D_acl) debug_printf(
1424 "PDKIM >> Header data for hash, canonicalized, in sequence >>>>>>>>>>>>>>\n");
1425
1426 /* SIGNING ---------------------------------------------------------------- */
1427 /* When signing, walk through our header list and add them to the hash. As we
1428 go, construct a list of the header's names to use for the h= parameter.
1429 Then append to that list any remaining header names for which there was no
1430 header to sign. */
1431
1432 if (ctx->flags & PDKIM_MODE_SIGN)
1433 {
1434 uschar * headernames = NULL; /* Collected signed header names */
1435 int hs = 0, hl = 0;
1436 pdkim_stringlist *p;
1437 const uschar * l;
1438 uschar * s;
1439 int sep = 0;
1440
1441 for (p = sig->headers; p; p = p->next)
1442 if (header_name_match(p->value, sig->sign_headers) == PDKIM_OK)
1443 {
1444 uschar * rh;
1445 /* Collect header names (Note: colon presence is guaranteed here) */
1446 uschar * q = Ustrchr(p->value, ':');
1447
1448 headernames = string_catn(headernames, &hs, &hl,
1449 p->value, (q - US p->value) + (p->next ? 1 : 0));
1450
1451 rh = sig->canon_headers == PDKIM_CANON_RELAXED
1452 ? pdkim_relax_header(p->value, 1) /* cook header for relaxed canon */
1453 : string_copy(CUS p->value); /* just copy it for simple canon */
1454
1455 /* Feed header to the hash algorithm */
1456 exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh));
1457
1458 /* Remember headers block for signing (when the library cannot do incremental) */
1459 (void) exim_rsa_data_append(&hdata, &hdata_alloc, rh);
1460
1461 DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh));
1462 }
1463
1464 l = sig->sign_headers;
1465 while((s = string_nextinlist(&l, &sep, NULL, 0)))
1466 if (*s != '_')
1467 { /*SSS string_append_listele() */
1468 if (hl > 0 && headernames[hl-1] != ':')
1469 headernames = string_catn(headernames, &hs, &hl, US":", 1);
1470
1471 headernames = string_cat(headernames, &hs, &hl, s);
1472 }
1473 headernames[hl] = '\0';
1474
1475 /* Copy headernames to signature struct */
1476 sig->headernames = headernames;
1477
1478 /* Create signature header with b= omitted */
1479 sig_hdr = pdkim_create_header(sig, FALSE);
1480 }
1481
1482 /* VERIFICATION ----------------------------------------------------------- */
1483 /* When verifying, walk through the header name list in the h= parameter and
1484 add the headers to the hash in that order. */
1485 else
1486 {
1487 uschar * p = sig->headernames;
1488 uschar * q;
1489 pdkim_stringlist * hdrs;
1490
1491 if (p)
1492 {
1493 /* clear tags */
1494 for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
1495 hdrs->tag = 0;
1496
1497 p = string_copy(p);
1498 while(1)
1499 {
1500 if ((q = Ustrchr(p, ':')))
1501 *q = '\0';
1502
1503 /*XXX walk the list of headers in same order as received. */
1504 for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
1505 if ( hdrs->tag == 0
1506 && strncasecmp(CCS hdrs->value, CCS p, Ustrlen(p)) == 0
1507 && (hdrs->value)[Ustrlen(p)] == ':'
1508 )
1509 {
1510 /* cook header for relaxed canon, or just copy it for simple */
1511
1512 uschar * rh = sig->canon_headers == PDKIM_CANON_RELAXED
1513 ? pdkim_relax_header(hdrs->value, 1)
1514 : string_copy(CUS hdrs->value);
1515
1516 /* Feed header to the hash algorithm */
1517 exim_sha_update(&hhash_ctx, CUS rh, Ustrlen(rh));
1518
1519 DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh));
1520 hdrs->tag = 1;
1521 break;
1522 }
1523
1524 if (!q) break;
1525 p = q+1;
1526 }
1527
1528 sig_hdr = string_copy(sig->rawsig_no_b_val);
1529 }
1530 }
1531
1532 DEBUG(D_acl) debug_printf(
1533 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1534
1535 /* Relax header if necessary */
1536 if (sig->canon_headers == PDKIM_CANON_RELAXED)
1537 sig_hdr = pdkim_relax_header(sig_hdr, 0);
1538
1539 DEBUG(D_acl)
1540 {
1541 debug_printf(
1542 "PDKIM >> Signed DKIM-Signature header, canonicalized >>>>>>>>>>>>>>>>>\n");
1543 pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr));
1544 debug_printf(
1545 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1546 }
1547
1548 /* Finalize header hash */
1549 exim_sha_update(&hhash_ctx, CUS sig_hdr, Ustrlen(sig_hdr));
1550 exim_sha_finish(&hhash_ctx, &hhash);
1551
1552 DEBUG(D_acl)
1553 {
1554 debug_printf("PDKIM [%s] Header hash computed: ", sig->domain);
1555 pdkim_hexprint(hhash.data, hhash.len);
1556 }
1557
1558 /* Remember headers block for signing (when the library cannot do incremental) */
1559 if (ctx->flags & PDKIM_MODE_SIGN)
1560 (void) exim_rsa_data_append(&hdata, &hdata_alloc, US sig_hdr);
1561
1562 /* SIGNING ---------------------------------------------------------------- */
1563 if (ctx->flags & PDKIM_MODE_SIGN)
1564 {
1565 es_ctx sctx;
1566 const uschar * errstr;
1567
1568 /* Import private key */
1569 if ((errstr = exim_rsa_signing_init(US sig->rsa_privkey, &sctx)))
1570 {
1571 DEBUG(D_acl) debug_printf("signing_init: %s\n", errstr);
1572 return PDKIM_ERR_RSA_PRIVKEY;
1573 }
1574
1575 /* Do signing. With OpenSSL we are signing the hash of headers just
1576 calculated, with GnuTLS we have to sign an entire block of headers
1577 (due to available interfaces) and it recalculates the hash internally. */
1578
1579 #if defined(RSA_OPENSSL) || defined(RSA_GCRYPT)
1580 hdata = hhash;
1581 #endif
1582
1583 if ((errstr = exim_rsa_sign(&sctx, is_sha1, &hdata, &sig->sigdata)))
1584 {
1585 DEBUG(D_acl) debug_printf("signing: %s\n", errstr);
1586 return PDKIM_ERR_RSA_SIGNING;
1587 }
1588
1589 DEBUG(D_acl)
1590 {
1591 debug_printf( "PDKIM [%s] b computed: ", sig->domain);
1592 pdkim_hexprint(sig->sigdata.data, sig->sigdata.len);
1593 }
1594
1595 sig->signature_header = pdkim_create_header(sig, TRUE);
1596 }
1597
1598 /* VERIFICATION ----------------------------------------------------------- */
1599 else
1600 {
1601 ev_ctx vctx;
1602 const uschar * errstr;
1603 pdkim_pubkey * p;
1604
1605 /* Make sure we have all required signature tags */
1606 if (!( sig->domain && *sig->domain
1607 && sig->selector && *sig->selector
1608 && sig->headernames && *sig->headernames
1609 && sig->bodyhash.data
1610 && sig->sigdata.data
1611 && sig->algo > -1
1612 && sig->version
1613 ) )
1614 {
1615 sig->verify_status = PDKIM_VERIFY_INVALID;
1616 sig->verify_ext_status = PDKIM_VERIFY_INVALID_SIGNATURE_ERROR;
1617
1618 DEBUG(D_acl) debug_printf(
1619 " Error in DKIM-Signature header: tags missing or invalid\n"
1620 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1621 goto NEXT_VERIFY;
1622 }
1623
1624 /* Make sure sig uses supported DKIM version (only v1) */
1625 if (sig->version != 1)
1626 {
1627 sig->verify_status = PDKIM_VERIFY_INVALID;
1628 sig->verify_ext_status = PDKIM_VERIFY_INVALID_DKIM_VERSION;
1629
1630 DEBUG(D_acl) debug_printf(
1631 " Error in DKIM-Signature header: unsupported DKIM version\n"
1632 "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1633 goto NEXT_VERIFY;
1634 }
1635
1636 if (!(sig->pubkey = pdkim_key_from_dns(ctx, sig, &vctx)))
1637 goto NEXT_VERIFY;
1638
1639 /* Check the signature */
1640 if ((errstr = exim_rsa_verify(&vctx, is_sha1, &hhash, &sig->sigdata)))
1641 {
1642 DEBUG(D_acl) debug_printf("headers verify: %s\n", errstr);
1643 sig->verify_status = PDKIM_VERIFY_FAIL;
1644 sig->verify_ext_status = PDKIM_VERIFY_FAIL_MESSAGE;
1645 goto NEXT_VERIFY;
1646 }
1647
1648
1649 /* We have a winner! (if bodyhash was correct earlier) */
1650 if (sig->verify_status == PDKIM_VERIFY_NONE)
1651 sig->verify_status = PDKIM_VERIFY_PASS;
1652
1653 NEXT_VERIFY:
1654
1655 DEBUG(D_acl)
1656 {
1657 debug_printf("PDKIM [%s] signature status: %s",
1658 sig->domain, pdkim_verify_status_str(sig->verify_status));
1659 if (sig->verify_ext_status > 0)
1660 debug_printf(" (%s)\n",
1661 pdkim_verify_ext_status_str(sig->verify_ext_status));
1662 else
1663 debug_printf("\n");
1664 }
1665 }
1666
1667 sig = sig->next;
1668 }
1669
1670 /* If requested, set return pointer to signature(s) */
1671 if (return_signatures)
1672 *return_signatures = ctx->sig;
1673
1674 return PDKIM_OK;
1675 }
1676
1677
1678 /* -------------------------------------------------------------------------- */
1679
1680 DLLEXPORT pdkim_ctx *
1681 pdkim_init_verify(int(*dns_txt_callback)(char *, char *), BOOL dot_stuffing)
1682 {
1683 pdkim_ctx * ctx;
1684
1685 ctx = store_get(sizeof(pdkim_ctx));
1686 memset(ctx, 0, sizeof(pdkim_ctx));
1687
1688 if (dot_stuffing) ctx->flags = PDKIM_DOT_TERM;
1689 ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN);
1690 ctx->dns_txt_callback = dns_txt_callback;
1691
1692 return ctx;
1693 }
1694
1695
1696 /* -------------------------------------------------------------------------- */
1697
1698 DLLEXPORT pdkim_ctx *
1699 pdkim_init_sign(char * domain, char * selector, char * rsa_privkey, int algo,
1700 BOOL dot_stuffed, int(*dns_txt_callback)(char *, char *))
1701 {
1702 pdkim_ctx * ctx;
1703 pdkim_signature * sig;
1704
1705 if (!domain || !selector || !rsa_privkey)
1706 return NULL;
1707
1708 ctx = store_get(sizeof(pdkim_ctx) + PDKIM_MAX_BODY_LINE_LEN + sizeof(pdkim_signature));
1709 memset(ctx, 0, sizeof(pdkim_ctx));
1710
1711 ctx->flags = dot_stuffed ? PDKIM_MODE_SIGN | PDKIM_DOT_TERM : PDKIM_MODE_SIGN;
1712 ctx->linebuf = CS (ctx+1);
1713
1714 DEBUG(D_acl) ctx->dns_txt_callback = dns_txt_callback;
1715
1716 sig = (pdkim_signature *)(ctx->linebuf + PDKIM_MAX_BODY_LINE_LEN);
1717 memset(sig, 0, sizeof(pdkim_signature));
1718
1719 sig->bodylength = -1;
1720 ctx->sig = sig;
1721
1722 sig->domain = string_copy(US domain);
1723 sig->selector = string_copy(US selector);
1724 sig->rsa_privkey = string_copy(US rsa_privkey);
1725 sig->algo = algo;
1726
1727 exim_sha_init(&sig->body_hash, algo == PDKIM_ALGO_RSA_SHA1 ? HASH_SHA1 : HASH_SHA256);
1728
1729 DEBUG(D_acl)
1730 {
1731 pdkim_signature s = *sig;
1732 ev_ctx vctx;
1733
1734 debug_printf("PDKIM (checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1735 if (!pdkim_key_from_dns(ctx, &s, &vctx))
1736 debug_printf("WARNING: bad dkim key in dns\n");
1737 debug_printf("PDKIM (finished checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
1738 }
1739
1740 return ctx;
1741 }
1742
1743
1744 /* -------------------------------------------------------------------------- */
1745
1746 DLLEXPORT int
1747 pdkim_set_optional(pdkim_ctx *ctx,
1748 char *sign_headers,
1749 char *identity,
1750 int canon_headers,
1751 int canon_body,
1752 long bodylength,
1753 unsigned long created,
1754 unsigned long expires)
1755 {
1756 pdkim_signature * sig = ctx->sig;
1757
1758 if (identity)
1759 sig->identity = string_copy(US identity);
1760
1761 sig->sign_headers = string_copy(sign_headers
1762 ? US sign_headers : US PDKIM_DEFAULT_SIGN_HEADERS);
1763
1764 sig->canon_headers = canon_headers;
1765 sig->canon_body = canon_body;
1766 sig->bodylength = bodylength;
1767 sig->created = created;
1768 sig->expires = expires;
1769
1770 return PDKIM_OK;
1771 }
1772
1773
1774 void
1775 pdkim_init(void)
1776 {
1777 exim_rsa_init();
1778 }
1779
1780
1781
1782 #endif /*DISABLE_DKIM*/
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