ARC: better diagnostics for keyfile issues
[exim.git] / src / src / arc.c
CommitLineData
617d3932
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1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4/* Experimental ARC support for Exim
5 Copyright (c) Jeremy Harris 2018
6 License: GPL
7*/
8
9#include "exim.h"
10#ifdef EXPERIMENTAL_ARC
11# if !defined SUPPORT_SPF
12# error SPF must also be enabled for ARC
13# elif defined DISABLE_DKIM
14# error DKIM must also be enabled for ARC
15# else
16
17# include "functions.h"
18# include "pdkim/pdkim.h"
19# include "pdkim/signing.h"
20
21extern pdkim_ctx * dkim_verify_ctx;
22extern pdkim_ctx dkim_sign_ctx;
23
a93dbf44 24#define ARC_SIGN_OPT_TSTAMP BIT(0)
0e83c148
JH
25#define ARC_SIGN_OPT_EXPIRE BIT(1)
26
27#define ARC_SIGN_DEFAULT_EXPIRE_DELTA (60 * 60 * 24 * 30) /* one month */
a93dbf44 28
617d3932
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29/******************************************************************************/
30
31typedef struct hdr_rlist {
32 struct hdr_rlist * prev;
33 BOOL used;
34 header_line * h;
35} hdr_rlist;
36
37typedef struct arc_line {
38 header_line * complete; /* including the header name; nul-term */
39 uschar * relaxed;
40
41 /* identified tag contents */
42 /*XXX t= for AS? */
43 blob i;
44 blob cv;
45 blob a;
46 blob b;
47 blob bh;
48 blob d;
49 blob h;
50 blob s;
51 blob c;
52 blob l;
53
54 /* tag content sub-portions */
55 blob a_algo;
56 blob a_hash;
57
58 blob c_head;
59 blob c_body;
60
61 /* modified copy of b= field in line */
62 blob rawsig_no_b_val;
63} arc_line;
64
65typedef struct arc_set {
66 struct arc_set * next;
67 struct arc_set * prev;
68
69 unsigned instance;
70 arc_line * hdr_aar;
71 arc_line * hdr_ams;
72 arc_line * hdr_as;
73
93c931f8 74 const uschar * ams_verify_done;
617d3932
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75 BOOL ams_verify_passed;
76} arc_set;
77
78typedef struct arc_ctx {
79 arc_set * arcset_chain;
80 arc_set * arcset_chain_last;
81} arc_ctx;
82
83#define ARC_HDR_AAR US"ARC-Authentication-Results:"
84#define ARC_HDRLEN_AAR 27
85#define ARC_HDR_AMS US"ARC-Message-Signature:"
86#define ARC_HDRLEN_AMS 22
87#define ARC_HDR_AS US"ARC-Seal:"
88#define ARC_HDRLEN_AS 9
89#define HDR_AR US"Authentication-Results:"
90#define HDRLEN_AR 23
91
0e83c148
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92static time_t now;
93static time_t expire;
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94static hdr_rlist * headers_rlist;
95static arc_ctx arc_sign_ctx = { NULL };
9cffa436 96static arc_ctx arc_verify_ctx = { NULL };
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97
98
99/******************************************************************************/
100
101
102/* Get the instance number from the header.
103Return 0 on error */
104static unsigned
105arc_instance_from_hdr(const arc_line * al)
106{
978e78de 107const uschar * s = al->i.data;
617d3932 108if (!s || !al->i.len) return 0;
978e78de 109return (unsigned) atoi(CCS s);
617d3932
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110}
111
112
113static uschar *
114skip_fws(uschar * s)
115{
116uschar c = *s;
117while (c && (c == ' ' || c == '\t' || c == '\n' || c == '\r')) c = *++s;
118return s;
119}
120
121
122/* Locate instance struct on chain, inserting a new one if
123needed. The chain is in increasing-instance-number order
124by the "next" link, and we have a "prev" link also.
125*/
126
127static arc_set *
128arc_find_set(arc_ctx * ctx, unsigned i)
129{
130arc_set ** pas, * as, * next, * prev;
131
132for (pas = &ctx->arcset_chain, prev = NULL, next = ctx->arcset_chain;
133 as = *pas; pas = &as->next)
134 {
135 if (as->instance > i) break;
136 if (as->instance == i)
137 {
138 DEBUG(D_acl) debug_printf("ARC: existing instance %u\n", i);
139 return as;
140 }
141 next = as->next;
142 prev = as;
143 }
144
145DEBUG(D_acl) debug_printf("ARC: new instance %u\n", i);
146*pas = as = store_get(sizeof(arc_set));
147memset(as, 0, sizeof(arc_set));
148as->next = next;
149as->prev = prev;
150as->instance = i;
151if (next)
152 next->prev = as;
153else
154 ctx->arcset_chain_last = as;
155return as;
156}
157
158
159
160/* Insert a tag content into the line structure.
161Note this is a reference to existing data, not a copy.
162Check for already-seen tag.
163The string-pointer is on the '=' for entry. Update it past the
164content (to the ;) on return;
165*/
166
167static uschar *
168arc_insert_tagvalue(arc_line * al, unsigned loff, uschar ** ss)
169{
170uschar * s = *ss;
171uschar c = *++s;
172blob * b = (blob *)(US al + loff);
173size_t len = 0;
174
175/* [FWS] tag-value [FWS] */
176
177if (b->data) return US"fail";
178s = skip_fws(s); /* FWS */
179
180b->data = s;
181while ((c = *s) && c != ';') { len++; s++; }
182*ss = s;
183while (len && ((c = s[-1]) == ' ' || c == '\t' || c == '\n' || c == '\r'))
184 { s--; len--; } /* FWS */
185b->len = len;
186return NULL;
187}
188
189
190/* Inspect a header line, noting known tag fields.
191Check for duplicates. */
192
193static uschar *
194arc_parse_line(arc_line * al, header_line * h, unsigned off, BOOL instance_only)
195{
196uschar * s = h->text + off;
978e78de 197uschar * r = NULL; /* compiler-quietening */
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198uschar c;
199
200al->complete = h;
201
202if (!instance_only)
203 {
204 al->rawsig_no_b_val.data = store_get(h->slen + 1);
205 memcpy(al->rawsig_no_b_val.data, h->text, off); /* copy the header name blind */
206 r = al->rawsig_no_b_val.data + off;
207 al->rawsig_no_b_val.len = off;
208 }
209
210/* tag-list = tag-spec *( ";" tag-spec ) [ ";" ] */
211
212while ((c = *s))
213 {
214 char tagchar;
215 uschar * t;
216 unsigned i = 0;
217 uschar * fieldstart = s;
218 uschar * bstart = NULL, * bend;
219
220 /* tag-spec = [FWS] tag-name [FWS] "=" [FWS] tag-value [FWS] */
221
222 s = skip_fws(s); /* FWS */
223 if (!*s) break;
224/* debug_printf("%s: consider '%s'\n", __FUNCTION__, s); */
225 tagchar = *s++;
226 s = skip_fws(s); /* FWS */
227 if (!*s) break;
228
229 if (!instance_only || tagchar == 'i') switch (tagchar)
230 {
231 case 'a': /* a= AMS algorithm */
232 {
233 if (*s != '=') return US"no 'a' value";
234 if (arc_insert_tagvalue(al, offsetof(arc_line, a), &s)) return US"a tag dup";
235
236 /* substructure: algo-hash (eg. rsa-sha256) */
237
238 t = al->a_algo.data = al->a.data;
239 while (*t != '-')
240 if (!*t++ || ++i > al->a.len) return US"no '-' in 'a' value";
241 al->a_algo.len = i;
242 if (*t++ != '-') return US"no '-' in 'a' value";
243 al->a_hash.data = t;
244 al->a_hash.len = al->a.len - i - 1;
245 }
246 break;
247 case 'b':
248 {
249 gstring * g = NULL;
250
251 switch (*s)
252 {
253 case '=': /* b= AMS signature */
254 if (al->b.data) return US"already b data";
255 bstart = s+1;
256
257 /* The signature can have FWS inserted in the content;
258 make a stripped copy */
259
260 while ((c = *++s) && c != ';')
261 if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
262 g = string_catn(g, s, 1);
263 al->b.data = string_from_gstring(g);
264 al->b.len = g->ptr;
265 gstring_reset_unused(g);
266 bend = s;
267 break;
268 case 'h': /* bh= AMS body hash */
269 s = skip_fws(++s); /* FWS */
270 if (*s != '=') return US"no bh value";
271 if (al->bh.data) return US"already bh data";
272
273 /* The bodyhash can have FWS inserted in the content;
274 make a stripped copy */
275
276 while ((c = *++s) && c != ';')
277 if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
278 g = string_catn(g, s, 1);
279 al->bh.data = string_from_gstring(g);
280 al->bh.len = g->ptr;
281 gstring_reset_unused(g);
282 break;
283 default:
284 return US"b? tag";
285 }
286 }
287 break;
288 case 'c':
289 switch (*s)
290 {
291 case '=': /* c= AMS canonicalisation */
292 if (arc_insert_tagvalue(al, offsetof(arc_line, c), &s)) return US"c tag dup";
293
294 /* substructure: head/body (eg. relaxed/simple)) */
295
296 t = al->c_head.data = al->c.data;
297 while (isalpha(*t))
298 if (!*t++ || ++i > al->a.len) break;
299 al->c_head.len = i;
300 if (*t++ == '/') /* /body is optional */
301 {
302 al->c_body.data = t;
303 al->c_body.len = al->c.len - i - 1;
304 }
305 else
306 {
307 al->c_body.data = US"simple";
308 al->c_body.len = 6;
309 }
310 break;
311 case 'v': /* cv= AS validity */
312 if (*++s != '=') return US"cv tag val";
313 if (arc_insert_tagvalue(al, offsetof(arc_line, cv), &s)) return US"cv tag dup";
314 break;
315 default:
316 return US"c? tag";
317 }
318 break;
319 case 'd': /* d= AMS domain */
320 if (*s != '=') return US"d tag val";
321 if (arc_insert_tagvalue(al, offsetof(arc_line, d), &s)) return US"d tag dup";
322 break;
323 case 'h': /* h= AMS headers */
324 if (*s != '=') return US"h tag val";
325 if (arc_insert_tagvalue(al, offsetof(arc_line, h), &s)) return US"h tag dup";
326 break;
327 case 'i': /* i= ARC set instance */
328 if (*s != '=') return US"i tag val";
329 if (arc_insert_tagvalue(al, offsetof(arc_line, i), &s)) return US"i tag dup";
330 if (instance_only) goto done;
331 break;
332 case 'l': /* l= bodylength */
333 if (*s != '=') return US"l tag val";
334 if (arc_insert_tagvalue(al, offsetof(arc_line, l), &s)) return US"l tag dup";
335 break;
336 case 's': /* s= AMS selector */
337 if (*s != '=') return US"s tag val";
338 if (arc_insert_tagvalue(al, offsetof(arc_line, s), &s)) return US"s tag dup";
339 break;
340 }
341
342 while ((c = *s) && c != ';') s++;
343 if (c) s++; /* ; after tag-spec */
344
345 /* for all but the b= tag, copy the field including FWS. For the b=,
346 drop the tag content. */
347
348 if (!instance_only)
349 if (bstart)
350 {
351 size_t n = bstart - fieldstart;
352 memcpy(r, fieldstart, n); /* FWS "b=" */
353 r += n;
354 al->rawsig_no_b_val.len += n;
355 n = s - bend;
356 memcpy(r, bend, n); /* FWS ";" */
357 r += n;
358 al->rawsig_no_b_val.len += n;
359 }
360 else
361 {
362 size_t n = s - fieldstart;
363 memcpy(r, fieldstart, n);
364 r += n;
365 al->rawsig_no_b_val.len += n;
366 }
367 }
368
369if (!instance_only)
370 *r = '\0';
371
372done:
373/* debug_printf("%s: finshed\n", __FUNCTION__); */
374return NULL;
375}
376
377
378/* Insert one header line in the correct set of the chain,
379adding instances as needed and checking for duplicate lines.
380*/
381
382static uschar *
383arc_insert_hdr(arc_ctx * ctx, header_line * h, unsigned off, unsigned hoff,
384 BOOL instance_only)
385{
ef262e31 386unsigned i;
617d3932
JH
387arc_set * as;
388arc_line * al = store_get(sizeof(arc_line)), ** alp;
389uschar * e;
390
391memset(al, 0, sizeof(arc_line));
392
393if ((e = arc_parse_line(al, h, off, instance_only)))
394 {
395 DEBUG(D_acl) if (e) debug_printf("ARC: %s\n", e);
396 return US"line parse";
397 }
398if (!(i = arc_instance_from_hdr(al))) return US"instance find";
ef262e31 399if (i > 50) return US"overlarge instance number";
617d3932
JH
400if (!(as = arc_find_set(ctx, i))) return US"set find";
401if (*(alp = (arc_line **)(US as + hoff))) return US"dup hdr";
402
403*alp = al;
404return NULL;
405}
406
407
408
409
410static const uschar *
411arc_try_header(arc_ctx * ctx, header_line * h, BOOL instance_only)
412{
413const uschar * e;
414
415/*debug_printf("consider hdr '%s'\n", h->text);*/
416if (strncmpic(ARC_HDR_AAR, h->text, ARC_HDRLEN_AAR) == 0)
417 {
418 DEBUG(D_acl)
419 {
420 int len = h->slen;
421 uschar * s;
422 for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
423 s--, len--;
424 debug_printf("ARC: found AAR: %.*s\n", len, h->text);
425 }
426 if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AAR, offsetof(arc_set, hdr_aar),
427 TRUE)))
428 {
429 DEBUG(D_acl) debug_printf("inserting AAR: %s\n", e);
430 return US"inserting AAR";
431 }
432 }
433else if (strncmpic(ARC_HDR_AMS, h->text, ARC_HDRLEN_AMS) == 0)
434 {
435 arc_line * ams;
436
437 DEBUG(D_acl)
438 {
439 int len = h->slen;
440 uschar * s;
441 for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
442 s--, len--;
443 debug_printf("ARC: found AMS: %.*s\n", len, h->text);
444 }
445 if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AMS, offsetof(arc_set, hdr_ams),
446 instance_only)))
447 {
448 DEBUG(D_acl) debug_printf("inserting AMS: %s\n", e);
449 return US"inserting AMS";
450 }
451
452 /* defaults */
453 /*XXX dubious selection of ams here */
454 ams = ctx->arcset_chain->hdr_ams;
455 if (!ams->c.data)
456 {
457 ams->c_head.data = US"simple"; ams->c_head.len = 6;
458 ams->c_body = ams->c_head;
459 }
460 }
461else if (strncmpic(ARC_HDR_AS, h->text, ARC_HDRLEN_AS) == 0)
462 {
463 DEBUG(D_acl)
464 {
465 int len = h->slen;
466 uschar * s;
467 for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
468 s--, len--;
469 debug_printf("ARC: found AS: %.*s\n", len, h->text);
470 }
471 if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AS, offsetof(arc_set, hdr_as),
472 instance_only)))
473 {
474 DEBUG(D_acl) debug_printf("inserting AS: %s\n", e);
475 return US"inserting AS";
476 }
477 }
478return NULL;
479}
480
481
482
483/* Gather the chain of arc sets from the headers.
484Check for duplicates while that is done. Also build the
485reverse-order headers list;
486
487Return: ARC state if determined, eg. by lack of any ARC chain.
488*/
489
490static const uschar *
491arc_vfy_collect_hdrs(arc_ctx * ctx)
492{
493header_line * h;
978e78de 494hdr_rlist * r = NULL, * rprev = NULL;
617d3932
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495const uschar * e;
496
497DEBUG(D_acl) debug_printf("ARC: collecting arc sets\n");
498for (h = header_list; h; h = h->next)
499 {
500 r = store_get(sizeof(hdr_rlist));
501 r->prev = rprev;
502 r->used = FALSE;
503 r->h = h;
504 rprev = r;
505
506 if ((e = arc_try_header(ctx, h, FALSE)))
93c931f8
JH
507 {
508 arc_state_reason = string_sprintf("collecting headers: %s", e);
509 return US"fail";
510 }
617d3932
JH
511 }
512headers_rlist = r;
513
514if (!ctx->arcset_chain) return US"none";
515return NULL;
516}
517
518
519static BOOL
520arc_cv_match(arc_line * al, const uschar * s)
521{
522return Ustrncmp(s, al->cv.data, al->cv.len) == 0;
523}
524
525/******************************************************************************/
526
527/* Return the hash of headers from the message that the AMS claims it
528signed.
529*/
530
531static void
532arc_get_verify_hhash(arc_ctx * ctx, arc_line * ams, blob * hhash)
533{
534const uschar * headernames = string_copyn(ams->h.data, ams->h.len);
535const uschar * hn;
536int sep = ':';
537hdr_rlist * r;
538BOOL relaxed = Ustrncmp(US"relaxed", ams->c_head.data, ams->c_head.len) == 0;
539int hashtype = pdkim_hashname_to_hashtype(
540 ams->a_hash.data, ams->a_hash.len);
541hctx hhash_ctx;
542const uschar * s;
543int len;
544
545if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
546 {
547 DEBUG(D_acl)
548 debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
549 return;
550 }
551
552/* For each headername in the list from the AMS (walking in order)
553walk the message headers in reverse order, adding to the hash any
554found for the first time. For that last point, maintain used-marks
555on the list of message headers. */
556
557DEBUG(D_acl) debug_printf("ARC: AMS header data for verification:\n");
558
559for (r = headers_rlist; r; r = r->prev)
560 r->used = FALSE;
561while ((hn = string_nextinlist(&headernames, &sep, NULL, 0)))
562 for (r = headers_rlist; r; r = r->prev)
563 if ( !r->used
564 && strncasecmp(CCS (s = r->h->text), CCS hn, Ustrlen(hn)) == 0
565 )
566 {
567 if (relaxed) s = pdkim_relax_header_n(s, r->h->slen, TRUE);
568
569 len = Ustrlen(s);
570 DEBUG(D_acl) pdkim_quoteprint(s, len);
571 exim_sha_update(&hhash_ctx, s, Ustrlen(s));
572 r->used = TRUE;
573 break;
574 }
575
d9604f37 576/* Finally add in the signature header (with the b= tag stripped); no CRLF */
617d3932
JH
577
578s = ams->rawsig_no_b_val.data, len = ams->rawsig_no_b_val.len;
579if (relaxed)
d9604f37 580 len = Ustrlen(s = pdkim_relax_header_n(s, len, FALSE));
617d3932
JH
581DEBUG(D_acl) pdkim_quoteprint(s, len);
582exim_sha_update(&hhash_ctx, s, len);
583
584exim_sha_finish(&hhash_ctx, hhash);
585DEBUG(D_acl)
586 { debug_printf("ARC: header hash: "); pdkim_hexprint(hhash->data, hhash->len); }
587return;
588}
589
590
591
592
593static pdkim_pubkey *
594arc_line_to_pubkey(arc_line * al)
595{
596uschar * dns_txt;
597pdkim_pubkey * p;
598
599if (!(dns_txt = dkim_exim_query_dns_txt(string_sprintf("%.*s._domainkey.%.*s",
600 al->s.len, al->s.data, al->d.len, al->d.data))))
601 {
602 DEBUG(D_acl) debug_printf("pubkey dns lookup fail\n");
603 return NULL;
604 }
605
606if ( !(p = pdkim_parse_pubkey_record(dns_txt))
607 || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0)
608 )
609 {
610 DEBUG(D_acl) debug_printf("pubkey dns lookup format error\n");
611 return NULL;
612 }
613
614/* If the pubkey limits use to specified hashes, reject unusable
615signatures. XXX should we have looked for multiple dns records? */
616
617if (p->hashes)
618 {
619 const uschar * list = p->hashes, * ele;
620 int sep = ':';
621
622 while ((ele = string_nextinlist(&list, &sep, NULL, 0)))
623 if (Ustrncmp(ele, al->a_hash.data, al->a_hash.len) == 0) break;
624 if (!ele)
625 {
626 DEBUG(D_acl) debug_printf("pubkey h=%s vs sig a=%.*s\n",
978e78de 627 p->hashes, (int)al->a.len, al->a.data);
617d3932
JH
628 return NULL;
629 }
630 }
631return p;
632}
633
634
635
636
637static pdkim_bodyhash *
638arc_ams_setup_vfy_bodyhash(arc_line * ams)
639{
640int canon_head, canon_body;
641long bodylen;
642
b3d9ebf5 643if (!ams->c.data) ams->c.data = US"simple"; /* RFC 6376 (DKIM) default */
617d3932
JH
644pdkim_cstring_to_canons(ams->c.data, ams->c.len, &canon_head, &canon_body);
645bodylen = ams->l.data
646 ? strtol(CS string_copyn(ams->l.data, ams->l.len), NULL, 10) : -1;
647
648return pdkim_set_bodyhash(dkim_verify_ctx,
649 pdkim_hashname_to_hashtype(ams->a_hash.data, ams->a_hash.len),
650 canon_body,
651 bodylen);
652}
653
654
655
656/* Verify an AMS. This is a DKIM-sig header, but with an ARC i= tag
657and without a DKIM v= tag.
658*/
659
93c931f8 660static const uschar *
617d3932
JH
661arc_ams_verify(arc_ctx * ctx, arc_set * as)
662{
663arc_line * ams = as->hdr_ams;
664pdkim_bodyhash * b;
665pdkim_pubkey * p;
666blob sighash;
667blob hhash;
668ev_ctx vctx;
669int hashtype;
670const uschar * errstr;
671
93c931f8 672as->ams_verify_done = US"in-progress";
617d3932
JH
673
674/* Check the AMS has all the required tags:
675 "a=" algorithm
676 "b=" signature
677 "bh=" body hash
678 "d=" domain (for key lookup)
679 "h=" headers (included in signature)
680 "s=" key-selector (for key lookup)
681*/
682if ( !ams->a.data || !ams->b.data || !ams->bh.data || !ams->d.data
683 || !ams->h.data || !ams->s.data)
93c931f8
JH
684 {
685 as->ams_verify_done = arc_state_reason = US"required tag missing";
617d3932 686 return US"fail";
93c931f8 687 }
617d3932
JH
688
689
690/* The bodyhash should have been created earlier, and the dkim code should
691have managed calculating it during message input. Find the reference to it. */
692
693if (!(b = arc_ams_setup_vfy_bodyhash(ams)))
93c931f8
JH
694 {
695 as->ams_verify_done = arc_state_reason = US"internal hash setup error";
617d3932 696 return US"fail";
93c931f8 697 }
617d3932
JH
698
699DEBUG(D_acl)
700 {
701 debug_printf("ARC i=%d AMS Body bytes hashed: %lu\n"
702 " Body %.*s computed: ",
703 as->instance, b->signed_body_bytes,
978e78de 704 (int)ams->a_hash.len, ams->a_hash.data);
617d3932
JH
705 pdkim_hexprint(CUS b->bh.data, b->bh.len);
706 }
707
708/* We know the bh-tag blob is of a nul-term string, so safe as a string */
709
710if ( !ams->bh.data
711 || (pdkim_decode_base64(ams->bh.data, &sighash), sighash.len != b->bh.len)
712 || memcmp(sighash.data, b->bh.data, b->bh.len) != 0
713 )
714 {
715 DEBUG(D_acl)
716 {
717 debug_printf("ARC i=%d AMS Body hash from headers: ", as->instance);
718 pdkim_hexprint(sighash.data, sighash.len);
719 debug_printf("ARC i=%d AMS Body hash did NOT match\n", as->instance);
720 }
93c931f8 721 return as->ams_verify_done = arc_state_reason = US"AMS body hash miscompare";
617d3932
JH
722 }
723
724DEBUG(D_acl) debug_printf("ARC i=%d AMS Body hash compared OK\n", as->instance);
725
726/* Get the public key from DNS */
727
728if (!(p = arc_line_to_pubkey(ams)))
93c931f8 729 return as->ams_verify_done = arc_state_reason = US"pubkey problem";
617d3932
JH
730
731/* We know the b-tag blob is of a nul-term string, so safe as a string */
732pdkim_decode_base64(ams->b.data, &sighash);
733
734arc_get_verify_hhash(ctx, ams, &hhash);
735
736/* Setup the interface to the signing library */
737
738if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
739 {
740 DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
93c931f8 741 as->ams_verify_done = arc_state_reason = US"internal sigverify init error";
617d3932
JH
742 return US"fail";
743 }
744
745hashtype = pdkim_hashname_to_hashtype(ams->a_hash.data, ams->a_hash.len);
746
747if ((errstr = exim_dkim_verify(&vctx,
748 pdkim_hashes[hashtype].exim_hashmethod, &hhash, &sighash)))
749 {
750 DEBUG(D_acl) debug_printf("ARC i=%d AMS verify %s\n", as->instance, errstr);
93c931f8 751 return as->ams_verify_done = arc_state_reason = US"AMS sig nonverify";
617d3932
JH
752 }
753
754DEBUG(D_acl) debug_printf("ARC i=%d AMS verify pass\n", as->instance);
755as->ams_verify_passed = TRUE;
756return NULL;
757}
758
759
760
761/* Check the sets are instance-continuous and that all
762members are present. Check that no arc_seals are "fail".
763Set the highest instance number global.
764Verify the latest AMS.
765*/
766static uschar *
767arc_headers_check(arc_ctx * ctx)
768{
769arc_set * as;
770int inst;
771BOOL ams_fail_found = FALSE;
617d3932 772
ea7b1f16 773if (!(as = ctx->arcset_chain_last))
617d3932
JH
774 return US"none";
775
ea7b1f16 776for(inst = as->instance; as; as = as->prev, inst--)
617d3932 777 {
ea7b1f16
JH
778 if (as->instance != inst)
779 arc_state_reason = string_sprintf("i=%d (sequence; expected %d)",
780 as->instance, inst);
781 else if (!as->hdr_aar || !as->hdr_ams || !as->hdr_as)
782 arc_state_reason = string_sprintf("i=%d (missing header)", as->instance);
783 else if (arc_cv_match(as->hdr_as, US"fail"))
784 arc_state_reason = string_sprintf("i=%d (cv)", as->instance);
785 else
786 goto good;
787
788 DEBUG(D_acl) debug_printf("ARC chain fail at %s\n", arc_state_reason);
789 return US"fail";
617d3932 790
ea7b1f16 791 good:
617d3932
JH
792 /* Evaluate the oldest-pass AMS validation while we're here.
793 It does not affect the AS chain validation but is reported as
794 auxilary info. */
795
796 if (!ams_fail_found)
797 if (arc_ams_verify(ctx, as))
798 ams_fail_found = TRUE;
799 else
800 arc_oldest_pass = inst;
93c931f8 801 arc_state_reason = NULL;
617d3932 802 }
ea7b1f16
JH
803if (inst != 0)
804 {
805 arc_state_reason = string_sprintf("(sequence; expected i=%d)", inst);
806 DEBUG(D_acl) debug_printf("ARC chain fail %s\n", arc_state_reason);
807 return US"fail";
808 }
617d3932
JH
809
810arc_received = ctx->arcset_chain_last;
ea7b1f16 811arc_received_instance = arc_received->instance;
617d3932
JH
812
813/* We can skip the latest-AMS validation, if we already did it. */
814
815as = ctx->arcset_chain_last;
3c676fa8 816if (!as->ams_verify_passed)
93c931f8 817 {
3c676fa8
JH
818 if (as->ams_verify_done)
819 {
820 arc_state_reason = as->ams_verify_done;
821 return US"fail";
822 }
823 if (!!arc_ams_verify(ctx, as))
824 return US"fail";
93c931f8 825 }
617d3932
JH
826return NULL;
827}
828
829
830/******************************************************************************/
831static const uschar *
832arc_seal_verify(arc_ctx * ctx, arc_set * as)
833{
834arc_line * hdr_as = as->hdr_as;
835arc_set * as2;
836int hashtype;
837hctx hhash_ctx;
838blob hhash_computed;
839blob sighash;
840ev_ctx vctx;
841pdkim_pubkey * p;
842const uschar * errstr;
843
844DEBUG(D_acl) debug_printf("ARC: AS vfy i=%d\n", as->instance);
845/*
846 1. If the value of the "cv" tag on that seal is "fail", the
847 chain state is "fail" and the algorithm stops here. (This
848 step SHOULD be skipped if the earlier step (2.1) was
849 performed) [it was]
850
851 2. In Boolean nomenclature: if ((i == 1 && cv != "none") or (cv
852 == "none" && i != 1)) then the chain state is "fail" and the
853 algorithm stops here (note that the ordering of the logic is
854 structured for short-circuit evaluation).
855*/
856
857if ( as->instance == 1 && !arc_cv_match(hdr_as, US"none")
858 || arc_cv_match(hdr_as, US"none") && as->instance != 1
859 )
93c931f8
JH
860 {
861 arc_state_reason = US"seal cv state";
617d3932 862 return US"fail";
93c931f8 863 }
617d3932
JH
864
865/*
866 3. Initialize a hash function corresponding to the "a" tag of
867 the ARC-Seal.
868*/
869
870hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
871
872if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
873 {
874 DEBUG(D_acl)
875 debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
93c931f8 876 arc_state_reason = US"seal hash setup error";
617d3932
JH
877 return US"fail";
878 }
879
880/*
881 4. Compute the canonicalized form of the ARC header fields, in
882 the order described in Section 5.4.2, using the "relaxed"
883 header canonicalization defined in Section 3.4.2 of
884 [RFC6376]. Pass the canonicalized result to the hash
885 function.
d9604f37
JH
886
887Headers are CRLF-separated, but the last one is not crlf-terminated.
617d3932
JH
888*/
889
890DEBUG(D_acl) debug_printf("ARC: AS header data for verification:\n");
891for (as2 = ctx->arcset_chain;
892 as2 && as2->instance <= as->instance;
893 as2 = as2->next)
894 {
895 arc_line * al;
896 uschar * s;
897 int len;
898
899 al = as2->hdr_aar;
900 if (!(s = al->relaxed))
901 al->relaxed = s = pdkim_relax_header_n(al->complete->text,
902 al->complete->slen, TRUE);
903 len = Ustrlen(s);
904 DEBUG(D_acl) pdkim_quoteprint(s, len);
905 exim_sha_update(&hhash_ctx, s, len);
906
907 al = as2->hdr_ams;
908 if (!(s = al->relaxed))
909 al->relaxed = s = pdkim_relax_header_n(al->complete->text,
910 al->complete->slen, TRUE);
911 len = Ustrlen(s);
912 DEBUG(D_acl) pdkim_quoteprint(s, len);
913 exim_sha_update(&hhash_ctx, s, len);
914
915 al = as2->hdr_as;
916 if (as2->instance == as->instance)
917 s = pdkim_relax_header_n(al->rawsig_no_b_val.data,
d9604f37 918 al->rawsig_no_b_val.len, FALSE);
617d3932
JH
919 else if (!(s = al->relaxed))
920 al->relaxed = s = pdkim_relax_header_n(al->complete->text,
921 al->complete->slen, TRUE);
922 len = Ustrlen(s);
923 DEBUG(D_acl) pdkim_quoteprint(s, len);
924 exim_sha_update(&hhash_ctx, s, len);
925 }
926
927/*
928 5. Retrieve the final digest from the hash function.
929*/
930
931exim_sha_finish(&hhash_ctx, &hhash_computed);
932DEBUG(D_acl)
933 {
934 debug_printf("ARC i=%d AS Header %.*s computed: ",
978e78de 935 as->instance, (int)hdr_as->a_hash.len, hdr_as->a_hash.data);
617d3932
JH
936 pdkim_hexprint(hhash_computed.data, hhash_computed.len);
937 }
938
939
940/*
941 6. Retrieve the public key identified by the "s" and "d" tags in
942 the ARC-Seal, as described in Section 4.1.6.
943*/
944
945if (!(p = arc_line_to_pubkey(hdr_as)))
946 return US"pubkey problem";
947
948/*
949 7. Determine whether the signature portion ("b" tag) of the ARC-
950 Seal and the digest computed above are valid according to the
951 public key. (See also Section Section 8.4 for failure case
952 handling)
953
954 8. If the signature is not valid, the chain state is "fail" and
955 the algorithm stops here.
956*/
957
958/* We know the b-tag blob is of a nul-term string, so safe as a string */
959pdkim_decode_base64(hdr_as->b.data, &sighash);
960
961if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
962 {
963 DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
964 return US"fail";
965 }
966
967hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
968
969if ((errstr = exim_dkim_verify(&vctx,
970 pdkim_hashes[hashtype].exim_hashmethod,
971 &hhash_computed, &sighash)))
972 {
973 DEBUG(D_acl)
974 debug_printf("ARC i=%d AS headers verify: %s\n", as->instance, errstr);
d9604f37 975 arc_state_reason = US"seal sigverify error";
617d3932
JH
976 return US"fail";
977 }
978
979DEBUG(D_acl) debug_printf("ARC: AS vfy i=%d pass\n", as->instance);
980return NULL;
981}
982
983
984static const uschar *
985arc_verify_seals(arc_ctx * ctx)
986{
987arc_set * as = ctx->arcset_chain;
988
989if (!as)
990 return US"none";
991
992while (as)
993 {
994 if (arc_seal_verify(ctx, as)) return US"fail";
995 as = as->next;
996 }
997DEBUG(D_acl) debug_printf("ARC: AS vfy overall pass\n");
998return NULL;
999}
1000/******************************************************************************/
1001
1002/* Do ARC verification. Called from DATA ACL, on a verify = arc
1003condition. No arguments; we are checking globals.
1004
1005Return: The ARC state, or NULL on error.
1006*/
1007
1008const uschar *
1009acl_verify_arc(void)
1010{
617d3932
JH
1011const uschar * res;
1012
9cffa436
JH
1013memset(&arc_verify_ctx, 0, sizeof(arc_verify_ctx));
1014
311fbe57
JH
1015if (!dkim_verify_ctx)
1016 {
1017 DEBUG(D_acl) debug_printf("ARC: no DKIM verify context\n");
1018 return NULL;
1019 }
1020
617d3932
JH
1021/* AS evaluation, per
1022https://tools.ietf.org/html/draft-ietf-dmarc-arc-protocol-10#section-6
1023*/
1024/* 1. Collect all ARC sets currently on the message. If there were
1025 none, the ARC state is "none" and the algorithm stops here.
1026*/
1027
9cffa436 1028if ((res = arc_vfy_collect_hdrs(&arc_verify_ctx)))
617d3932
JH
1029 goto out;
1030
1031/* 2. If the form of any ARC set is invalid (e.g., does not contain
1032 exactly one of each of the three ARC-specific header fields),
1033 then the chain state is "fail" and the algorithm stops here.
1034
1035 1. To avoid the overhead of unnecessary computation and delay
1036 from crypto and DNS operations, the cv value for all ARC-
1037 Seal(s) MAY be checked at this point. If any of the values
1038 are "fail", then the overall state of the chain is "fail" and
1039 the algorithm stops here.
1040
1041 3. Conduct verification of the ARC-Message-Signature header field
1042 bearing the highest instance number. If this verification fails,
1043 then the chain state is "fail" and the algorithm stops here.
1044*/
1045
9cffa436 1046if ((res = arc_headers_check(&arc_verify_ctx)))
617d3932
JH
1047 goto out;
1048
1049/* 4. For each ARC-Seal from the "N"th instance to the first, apply the
1050 following logic:
1051
1052 1. If the value of the "cv" tag on that seal is "fail", the
1053 chain state is "fail" and the algorithm stops here. (This
1054 step SHOULD be skipped if the earlier step (2.1) was
1055 performed)
1056
1057 2. In Boolean nomenclature: if ((i == 1 && cv != "none") or (cv
1058 == "none" && i != 1)) then the chain state is "fail" and the
1059 algorithm stops here (note that the ordering of the logic is
1060 structured for short-circuit evaluation).
1061
1062 3. Initialize a hash function corresponding to the "a" tag of
1063 the ARC-Seal.
1064
1065 4. Compute the canonicalized form of the ARC header fields, in
1066 the order described in Section 5.4.2, using the "relaxed"
1067 header canonicalization defined in Section 3.4.2 of
1068 [RFC6376]. Pass the canonicalized result to the hash
1069 function.
1070
1071 5. Retrieve the final digest from the hash function.
1072
1073 6. Retrieve the public key identified by the "s" and "d" tags in
1074 the ARC-Seal, as described in Section 4.1.6.
1075
1076 7. Determine whether the signature portion ("b" tag) of the ARC-
1077 Seal and the digest computed above are valid according to the
1078 public key. (See also Section Section 8.4 for failure case
1079 handling)
1080
1081 8. If the signature is not valid, the chain state is "fail" and
1082 the algorithm stops here.
1083
1084 5. If all seals pass validation, then the chain state is "pass", and
1085 the algorithm is complete.
1086*/
1087
9cffa436 1088if ((res = arc_verify_seals(&arc_verify_ctx)))
617d3932
JH
1089 goto out;
1090
1091res = US"pass";
1092
1093out:
1094 return res;
1095}
1096
1097/******************************************************************************/
1098
1099/* Prepend the header to the rlist */
1100
1101static hdr_rlist *
1102arc_rlist_entry(hdr_rlist * list, const uschar * s, int len)
1103{
1104hdr_rlist * r = store_get(sizeof(hdr_rlist) + sizeof(header_line));
1105header_line * h = r->h = (header_line *)(r+1);
1106
1107r->prev = list;
1108r->used = FALSE;
1109h->next = NULL;
1110h->type = 0;
1111h->slen = len;
1112h->text = US s;
1113
1114/* This works for either NL or CRLF lines; also nul-termination */
1115while (*++s)
1116 if (*s == '\n' && s[1] != '\t' && s[1] != ' ') break;
1117s++; /* move past end of line */
1118
1119return r;
1120}
1121
1122
1123/* Walk the given headers strings identifying each header, and construct
b3d9ebf5 1124a reverse-order list.
617d3932
JH
1125*/
1126
1127static hdr_rlist *
1128arc_sign_scan_headers(arc_ctx * ctx, gstring * sigheaders)
1129{
1130const uschar * s;
1131hdr_rlist * rheaders = NULL;
1132
1133s = sigheaders ? sigheaders->s : NULL;
1134if (s) while (*s)
1135 {
978e78de 1136 const uschar * s2 = s;
617d3932
JH
1137
1138 /* This works for either NL or CRLF lines; also nul-termination */
1139 while (*++s2)
1140 if (*s2 == '\n' && s2[1] != '\t' && s2[1] != ' ') break;
1141 s2++; /* move past end of line */
1142
1143 rheaders = arc_rlist_entry(rheaders, s, s2 - s);
1144 s = s2;
1145 }
1146return rheaders;
1147}
1148
1149
1150
1151/* Return the A-R content, without identity, with line-ending and
1152NUL termination. */
1153
1154static BOOL
1155arc_sign_find_ar(header_line * headers, const uschar * identity, blob * ret)
1156{
1157header_line * h;
1158int ilen = Ustrlen(identity);
1159
1160ret->data = NULL;
1161for(h = headers; h; h = h->next)
1162 {
1163 uschar * s = h->text, c;
1164 int len = h->slen;
1165
1166 if (Ustrncmp(s, HDR_AR, HDRLEN_AR) != 0) continue;
1167 s += HDRLEN_AR, len -= HDRLEN_AR; /* header name */
1168 while ( len > 0
1169 && (c = *s) && (c == ' ' || c == '\t' || c == '\r' || c == '\n'))
1170 s++, len--; /* FWS */
1171 if (Ustrncmp(s, identity, ilen) != 0) continue;
1172 s += ilen; len -= ilen; /* identity */
1173 if (len <= 0) continue;
1174 if ((c = *s) && c == ';') s++, len--; /* identity terminator */
1175 while ( len > 0
1176 && (c = *s) && (c == ' ' || c == '\t' || c == '\r' || c == '\n'))
1177 s++, len--; /* FWS */
1178 if (len <= 0) continue;
1179 ret->data = s;
1180 ret->len = len;
1181 return TRUE;
1182 }
1183return FALSE;
1184}
1185
1186
1187
1188/* Append a constructed AAR including CRLF. Add it to the arc_ctx too. */
1189
1190static gstring *
1191arc_sign_append_aar(gstring * g, arc_ctx * ctx,
1192 const uschar * identity, int instance, blob * ar)
1193{
1194int aar_off = g ? g->ptr : 0;
1195arc_set * as = store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line));
1196arc_line * al = (arc_line *)(as+1);
1197header_line * h = (header_line *)(al+1);
1198
1199g = string_catn(g, ARC_HDR_AAR, ARC_HDRLEN_AAR);
1200g = string_cat(g, string_sprintf(" i=%d; %s;\r\n\t", instance, identity));
1201g = string_catn(g, US ar->data, ar->len);
1202
1203h->slen = g->ptr - aar_off;
1204h->text = g->s + aar_off;
1205al->complete = h;
1206as->next = NULL;
1207as->prev = ctx->arcset_chain_last;
1208as->instance = instance;
1209as->hdr_aar = al;
1210if (instance == 1)
1211 ctx->arcset_chain = as;
1212else
1213 ctx->arcset_chain_last->next = as;
1214ctx->arcset_chain_last = as;
1215
1216DEBUG(D_transport) debug_printf("ARC: AAR '%.*s'\n", h->slen - 2, h->text);
1217return g;
1218}
1219
1220
1221
1222static BOOL
1223arc_sig_from_pseudoheader(gstring * hdata, int hashtype, const uschar * privkey,
1224 blob * sig, const uschar * why)
1225{
1226hashmethod hm = /*sig->keytype == KEYTYPE_ED25519*/ FALSE
1227 ? HASH_SHA2_512 : pdkim_hashes[hashtype].exim_hashmethod;
1228blob hhash;
1229es_ctx sctx;
1230const uschar * errstr;
1231
1232DEBUG(D_transport)
1233 {
1234 hctx hhash_ctx;
1235 debug_printf("ARC: %s header data for signing:\n", why);
1236 pdkim_quoteprint(hdata->s, hdata->ptr);
1237
1238 (void) exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod);
1239 exim_sha_update(&hhash_ctx, hdata->s, hdata->ptr);
1240 exim_sha_finish(&hhash_ctx, &hhash);
1241 debug_printf("ARC: header hash: "); pdkim_hexprint(hhash.data, hhash.len);
1242 }
1243
1244if (FALSE /*need hash for Ed25519 or GCrypt signing*/ )
1245 {
1246 hctx hhash_ctx;
1247 (void) exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod);
1248 exim_sha_update(&hhash_ctx, hdata->s, hdata->ptr);
1249 exim_sha_finish(&hhash_ctx, &hhash);
1250 }
1251else
1252 {
1253 hhash.data = hdata->s;
1254 hhash.len = hdata->ptr;
1255 }
1256
1257if ( (errstr = exim_dkim_signing_init(privkey, &sctx))
1258 || (errstr = exim_dkim_sign(&sctx, hm, &hhash, sig)))
1259 {
c3d43245 1260 log_write(0, LOG_MAIN, "ARC: %s signing: %s\n", why, errstr);
c59b09dc
JH
1261 DEBUG(D_transport)
1262 debug_printf("private key, or private-key file content, was: '%s'\n",
1263 privkey);
617d3932
JH
1264 return FALSE;
1265 }
1266return TRUE;
1267}
1268
1269
1270
1271static gstring *
1272arc_sign_append_sig(gstring * g, blob * sig)
1273{
1274/*debug_printf("%s: raw sig ", __FUNCTION__); pdkim_hexprint(sig->data, sig->len);*/
1275sig->data = pdkim_encode_base64(sig);
1276sig->len = Ustrlen(sig->data);
1277for (;;)
1278 {
1279 int len = MIN(sig->len, 74);
1280 g = string_catn(g, sig->data, len);
1281 if ((sig->len -= len) == 0) break;
1282 sig->data += len;
1283 g = string_catn(g, US"\r\n\t ", 5);
1284 }
1285g = string_catn(g, US";\r\n", 3);
1286gstring_reset_unused(g);
1287string_from_gstring(g);
1288return g;
1289}
1290
1291
1292/* Append a constructed AMS including CRLF. Add it to the arc_ctx too. */
1293
1294static gstring *
1295arc_sign_append_ams(gstring * g, arc_ctx * ctx, int instance,
1296 const uschar * identity, const uschar * selector, blob * bodyhash,
a93dbf44 1297 hdr_rlist * rheaders, const uschar * privkey, unsigned options)
617d3932
JH
1298{
1299uschar * s;
1300gstring * hdata = NULL;
1301int col;
1302int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6); /*XXX hardwired */
1303blob sig;
1304int ams_off;
1305arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line));
1306header_line * h = (header_line *)(al+1);
1307
1308/* debug_printf("%s\n", __FUNCTION__); */
1309
1310/* Construct the to-be-signed AMS pseudo-header: everything but the sig. */
1311
1312ams_off = g->ptr;
a93dbf44 1313g = string_append(g, 7,
617d3932
JH
1314 ARC_HDR_AMS,
1315 US" i=", string_sprintf("%d", instance),
1316 US"; a=rsa-sha256; c=relaxed; d=", identity, /*XXX hardwired */
a93dbf44
JH
1317 US"; s=", selector);
1318if (options & ARC_SIGN_OPT_TSTAMP)
1319 g = string_append(g, 2,
0e83c148
JH
1320 US"; t=", string_sprintf("%lu", (u_long)now));
1321if (options & ARC_SIGN_OPT_EXPIRE)
1322 g = string_append(g, 2,
1323 US"; x=", string_sprintf("%lu", (u_long)expire));
a93dbf44 1324g = string_append(g, 3,
617d3932
JH
1325 US";\r\n\tbh=", pdkim_encode_base64(bodyhash),
1326 US";\r\n\th=");
1327
1328for(col = 3; rheaders; rheaders = rheaders->prev)
1329 {
1330 const uschar * hnames = US"DKIM-Signature:" PDKIM_DEFAULT_SIGN_HEADERS;
1331 uschar * name, * htext = rheaders->h->text;
1332 int sep = ':';
1333
1334 /* Spot headers of interest */
1335
1336 while ((name = string_nextinlist(&hnames, &sep, NULL, 0)))
1337 {
1338 int len = Ustrlen(name);
1339 if (strncasecmp(CCS htext, CCS name, len) == 0)
1340 {
1341 /* If too long, fold line in h= field */
1342
1343 if (col + len > 78) g = string_catn(g, US"\r\n\t ", 5), col = 3;
1344
1345 /* Add name to h= list */
1346
1347 g = string_catn(g, name, len);
1348 g = string_catn(g, US":", 1);
1349 col += len + 1;
1350
1351 /* Accumulate header for hashing/signing */
1352
1353 hdata = string_cat(hdata,
1354 pdkim_relax_header_n(htext, rheaders->h->slen, TRUE)); /*XXX hardwired */
1355 break;
1356 }
1357 }
1358 }
1359
1360/* Lose the last colon from the h= list */
1361
1362if (g->s[g->ptr - 1] == ':') g->ptr--;
1363
1364g = string_catn(g, US";\r\n\tb=;", 7);
1365
1366/* Include the pseudo-header in the accumulation */
617d3932 1367
d9604f37 1368s = pdkim_relax_header_n(g->s + ams_off, g->ptr - ams_off, FALSE);
617d3932
JH
1369hdata = string_cat(hdata, s);
1370
1371/* Calculate the signature from the accumulation */
1372/*XXX does that need further relaxation? there are spaces embedded in the b= strings! */
1373
1374if (!arc_sig_from_pseudoheader(hdata, hashtype, privkey, &sig, US"AMS"))
1375 return NULL;
1376
1377/* Lose the trailing semicolon from the psuedo-header, and append the signature
1378(folded over lines) and termination to complete it. */
1379
1380g->ptr--;
1381g = arc_sign_append_sig(g, &sig);
1382
1383h->slen = g->ptr - ams_off;
1384h->text = g->s + ams_off;
1385al->complete = h;
1386ctx->arcset_chain_last->hdr_ams = al;
1387
1388DEBUG(D_transport) debug_printf("ARC: AMS '%.*s'\n", h->slen - 2, h->text);
1389return g;
1390}
1391
1392
1393
1394/* Look for an arc= result in an A-R header blob. We know that its data
1395happens to be a NUL-term string. */
1396
1397static uschar *
1398arc_ar_cv_status(blob * ar)
1399{
1400const uschar * resinfo = ar->data;
1401int sep = ';';
1402uschar * methodspec, * s;
1403
1404while ((methodspec = string_nextinlist(&resinfo, &sep, NULL, 0)))
1405 if (Ustrncmp(methodspec, US"arc=", 4) == 0)
1406 {
1407 uschar c;
1408 for (s = methodspec += 4;
1409 (c = *s) && c != ';' && c != ' ' && c != '\r' && c != '\n'; ) s++;
1410 return string_copyn(methodspec, s - methodspec);
1411 }
3d0a6e0f 1412return US"none";
617d3932
JH
1413}
1414
1415
1416
1417/* Build the AS header and prepend it */
1418
1419static gstring *
1420arc_sign_prepend_as(gstring * arcset_interim, arc_ctx * ctx,
1421 int instance, const uschar * identity, const uschar * selector, blob * ar,
a93dbf44 1422 const uschar * privkey, unsigned options)
617d3932
JH
1423{
1424gstring * arcset;
1425arc_set * as;
1426uschar * status = arc_ar_cv_status(ar);
1427arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line));
1428header_line * h = (header_line *)(al+1);
617d3932
JH
1429
1430gstring * hdata = NULL;
1431int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6); /*XXX hardwired */
1432blob sig;
1433
1434/*
1435- Generate AS
1436 - no body coverage
1437 - no h= tag; implicit coverage
1438 - arc status from A-R
1439 - if fail:
1440 - coverage is just the new ARC set
1441 including self (but with an empty b= in self)
1442 - if non-fail:
1443 - all ARC set headers, set-number order, aar then ams then as,
1444 including self (but with an empty b= in self)
1445*/
1446
1447/* Construct the AS except for the signature */
1448
a93dbf44 1449arcset = string_append(NULL, 9,
617d3932
JH
1450 ARC_HDR_AS,
1451 US" i=", string_sprintf("%d", instance),
1452 US"; cv=", status,
d4772796 1453 US"; a=rsa-sha256; d=", identity, /*XXX hardwired */
a93dbf44
JH
1454 US"; s=", selector); /*XXX same as AMS */
1455if (options & ARC_SIGN_OPT_TSTAMP)
1456 arcset = string_append(arcset, 2,
0e83c148 1457 US"; t=", string_sprintf("%lu", (u_long)now));
a93dbf44 1458arcset = string_cat(arcset,
617d3932
JH
1459 US";\r\n\t b=;");
1460
1461h->slen = arcset->ptr;
1462h->text = arcset->s;
1463al->complete = h;
1464ctx->arcset_chain_last->hdr_as = al;
1465
1466/* For any but "fail" chain-verify status, walk the entire chain in order by
1467instance. For fail, only the new arc-set. Accumulate the elements walked. */
1468
1469for (as = Ustrcmp(status, US"fail") == 0
1470 ? ctx->arcset_chain_last : ctx->arcset_chain;
1471 as; as = as->next)
1472 {
1473 /* Accumulate AAR then AMS then AS. Relaxed canonicalisation
1474 is required per standard. */
1475
1476 h = as->hdr_aar->complete;
1477 hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
1478 h = as->hdr_ams->complete;
1479 hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
1480 h = as->hdr_as->complete;
d9604f37 1481 hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, !!as->next));
617d3932
JH
1482 }
1483
1484/* Calculate the signature from the accumulation */
1485
1486if (!arc_sig_from_pseudoheader(hdata, hashtype, privkey, &sig, US"AS"))
1487 return NULL;
1488
1489/* Lose the trailing semicolon */
1490arcset->ptr--;
1491arcset = arc_sign_append_sig(arcset, &sig);
1492DEBUG(D_transport) debug_printf("ARC: AS '%.*s'\n", arcset->ptr - 2, arcset->s);
1493
1494/* Finally, append the AMS and AAR to the new AS */
1495
1496return string_catn(arcset, arcset_interim->s, arcset_interim->ptr);
1497}
1498
1499
1500/**************************************/
1501
1502/* Return pointer to pdkim_bodyhash for given hash method, creating new
1503method if needed.
1504*/
1505
1506void *
1507arc_ams_setup_sign_bodyhash(void)
1508{
1509int canon_head, canon_body;
1510
1511DEBUG(D_transport) debug_printf("ARC: requesting bodyhash\n");
1512pdkim_cstring_to_canons(US"relaxed", 7, &canon_head, &canon_body); /*XXX hardwired */
1513return pdkim_set_bodyhash(&dkim_sign_ctx,
1514 pdkim_hashname_to_hashtype(US"sha256", 6), /*XXX hardwired */
1515 canon_body,
1516 -1);
1517}
1518
1519
1520
b3d9ebf5
JH
1521void
1522arc_sign_init(void)
1523{
1524memset(&arc_sign_ctx, 0, sizeof(arc_sign_ctx));
1525}
1526
1527
1528
617d3932
JH
1529/* A "normal" header line, identified by DKIM processing. These arrive before
1530the call to arc_sign(), which carries any newly-created DKIM headers - and
1531those go textually before the normal ones in the message.
1532
1533We have to take the feed from DKIM as, in the transport-filter case, the
1534headers are not in memory at the time of the call to arc_sign().
1535
1536Take a copy of the header and construct a reverse-order list.
1537Also parse ARC-chain headers and build the chain struct, retaining pointers
1538into the copies.
1539*/
1540
1541static const uschar *
1542arc_header_sign_feed(gstring * g)
1543{
1544uschar * s = string_copyn(g->s, g->ptr);
1545headers_rlist = arc_rlist_entry(headers_rlist, s, g->ptr);
1546return arc_try_header(&arc_sign_ctx, headers_rlist->h, TRUE);
1547}
1548
1549
1550
1551/* ARC signing. Called from the smtp transport, if the arc_sign option is set.
1552The dkim_exim_sign() function has already been called, so will have hashed the
1553message body for us so long as we requested a hash previously.
1554
1555Arguments:
a93dbf44
JH
1556 signspec Three-element colon-sep list: identity, selector, privkey.
1557 Optional fourth element: comma-sep list of options.
617d3932
JH
1558 Already expanded
1559 sigheaders Any signature headers already generated, eg. by DKIM, or NULL
1560 errstr Error string
1561
1562Return value
1563 Set of headers to prepend to the message, including the supplied sigheaders
1564 but not the plainheaders.
1565*/
1566
1567gstring *
1568arc_sign(const uschar * signspec, gstring * sigheaders, uschar ** errstr)
1569{
a93dbf44
JH
1570const uschar * identity, * selector, * privkey, * opts, * s;
1571unsigned options = 0;
617d3932
JH
1572int sep = 0;
1573header_line * headers;
1574hdr_rlist * rheaders;
1575blob ar;
1576int instance;
1577gstring * g = NULL;
1578pdkim_bodyhash * b;
1579
0e83c148
JH
1580expire = now = 0;
1581
617d3932
JH
1582/* Parse the signing specification */
1583
1584identity = string_nextinlist(&signspec, &sep, NULL, 0);
1585selector = string_nextinlist(&signspec, &sep, NULL, 0);
69a82da3 1586if ( !*identity || !*selector
617d3932
JH
1587 || !(privkey = string_nextinlist(&signspec, &sep, NULL, 0)) || !*privkey)
1588 {
c3d43245 1589 log_write(0, LOG_MAIN, "ARC: bad signing-specification (%s)",
9f7d9fa1 1590 !*identity ? "identity" : !*selector ? "selector" : "private-key");
c3d43245 1591 return sigheaders ? sigheaders : string_get(0);
617d3932
JH
1592 }
1593if (*privkey == '/' && !(privkey = expand_file_big_buffer(privkey)))
c3d43245 1594 return sigheaders ? sigheaders : string_get(0);
617d3932 1595
a93dbf44
JH
1596if ((opts = string_nextinlist(&signspec, &sep, NULL, 0)))
1597 {
1598 int osep = ',';
1599 while ((s = string_nextinlist(&opts, &osep, NULL, 0)))
1600 if (Ustrcmp(s, "timestamps") == 0)
0e83c148 1601 {
a93dbf44 1602 options |= ARC_SIGN_OPT_TSTAMP;
0e83c148
JH
1603 if (!now) now = time(NULL);
1604 }
1605 else if (Ustrncmp(s, "expire", 6) == 0)
1606 {
1607 options |= ARC_SIGN_OPT_EXPIRE;
1608 if (*(s += 6) == '=')
1609 if (*++s == '+')
1610 {
1611 if (!(expire = (time_t)atoi(++s)))
1612 expire = ARC_SIGN_DEFAULT_EXPIRE_DELTA;
1613 if (!now) now = time(NULL);
1614 expire += now;
1615 }
1616 else
1617 expire = (time_t)atol(s);
1618 else
1619 {
1620 if (!now) now = time(NULL);
1621 expire = now + ARC_SIGN_DEFAULT_EXPIRE_DELTA;
1622 }
1623 }
a93dbf44
JH
1624 }
1625
617d3932
JH
1626DEBUG(D_transport) debug_printf("ARC: sign for %s\n", identity);
1627
b3d9ebf5
JH
1628/* Make an rlist of any new DKIM headers, then add the "normals" rlist to it.
1629Then scan the list for an A-R header. */
617d3932
JH
1630
1631string_from_gstring(sigheaders);
1632if ((rheaders = arc_sign_scan_headers(&arc_sign_ctx, sigheaders)))
1633 {
1634 hdr_rlist ** rp;
0c2250d1
JH
1635 for (rp = &headers_rlist; *rp; ) rp = &(*rp)->prev;
1636 *rp = rheaders;
617d3932 1637 }
b3d9ebf5 1638
617d3932
JH
1639/* Finally, build a normal-order headers list */
1640/*XXX only needed for hunt-the-AR? */
0c2250d1 1641/*XXX also, we really should be accepting any number of ADMD-matching ARs */
b3d9ebf5
JH
1642 {
1643 header_line * hnext = NULL;
0c2250d1
JH
1644 for (rheaders = headers_rlist; rheaders;
1645 hnext = rheaders->h, rheaders = rheaders->prev)
b3d9ebf5
JH
1646 rheaders->h->next = hnext;
1647 headers = hnext;
1648 }
617d3932
JH
1649
1650if (!(arc_sign_find_ar(headers, identity, &ar)))
1651 {
c3d43245 1652 log_write(0, LOG_MAIN, "ARC: no Authentication-Results header for signing");
617d3932
JH
1653 return sigheaders ? sigheaders : string_get(0);
1654 }
1655
b3d9ebf5
JH
1656/* We previously built the data-struct for the existing ARC chain, if any, using a headers
1657feed from the DKIM module. Use that to give the instance number for the ARC set we are
1658about to build. */
1659
1660DEBUG(D_transport)
1661 if (arc_sign_ctx.arcset_chain_last)
1662 debug_printf("ARC: existing chain highest instance: %d\n",
1663 arc_sign_ctx.arcset_chain_last->instance);
1664 else
1665 debug_printf("ARC: no existing chain\n");
1666
1667instance = arc_sign_ctx.arcset_chain_last ? arc_sign_ctx.arcset_chain_last->instance + 1 : 1;
1668
617d3932
JH
1669/*
1670- Generate AAR
1671 - copy the A-R; prepend i= & identity
1672*/
1673
1674g = arc_sign_append_aar(g, &arc_sign_ctx, identity, instance, &ar);
1675
1676/*
1677- Generate AMS
1678 - Looks fairly like a DKIM sig
1679 - Cover all DKIM sig headers as well as the usuals
1680 - ? oversigning?
1681 - Covers the data
1682 - we must have requested a suitable bodyhash previously
1683*/
1684
1685b = arc_ams_setup_sign_bodyhash();
1686g = arc_sign_append_ams(g, &arc_sign_ctx, instance, identity, selector,
a93dbf44 1687 &b->bh, headers_rlist, privkey, options);
617d3932
JH
1688
1689/*
1690- Generate AS
1691 - no body coverage
1692 - no h= tag; implicit coverage
1693 - arc status from A-R
1694 - if fail:
1695 - coverage is just the new ARC set
1696 including self (but with an empty b= in self)
1697 - if non-fail:
1698 - all ARC set headers, set-number order, aar then ams then as,
1699 including self (but with an empty b= in self)
1700*/
1701
97e939df
JH
1702if (g)
1703 g = arc_sign_prepend_as(g, &arc_sign_ctx, instance, identity, selector, &ar,
a93dbf44 1704 privkey, options);
617d3932
JH
1705
1706/* Finally, append the dkim headers and return the lot. */
1707
1708g = string_catn(g, sigheaders->s, sigheaders->ptr);
1709(void) string_from_gstring(g);
1710gstring_reset_unused(g);
1711return g;
1712}
1713
1714
1715/******************************************************************************/
1716
1717/* Check to see if the line is an AMS and if so, set up to validate it.
1718Called from the DKIM input processing. This must be done now as the message
1719body data is hashed during input.
1720
1721We call the DKIM code to request a body-hash; it has the facility already
1722and the hash parameters might be common with other requests.
1723*/
1724
1725static const uschar *
1726arc_header_vfy_feed(gstring * g)
1727{
1728header_line h;
1729arc_line al;
1730pdkim_bodyhash * b;
1731uschar * errstr;
1732
1733if (!dkim_verify_ctx) return US"no dkim context";
1734
1735if (strncmpic(ARC_HDR_AMS, g->s, ARC_HDRLEN_AMS) != 0) return US"not AMS";
1736
1737DEBUG(D_receive) debug_printf("ARC: spotted AMS header\n");
1738/* Parse the AMS header */
1739
1740h.next = NULL;
1741h.slen = g->size;
1742h.text = g->s;
1743memset(&al, 0, sizeof(arc_line));
1744if ((errstr = arc_parse_line(&al, &h, ARC_HDRLEN_AMS, FALSE)))
1745 {
1746 DEBUG(D_acl) if (errstr) debug_printf("ARC: %s\n", errstr);
1747 return US"line parsing error";
1748 }
1749
1750/* defaults */
1751if (!al.c.data)
1752 {
1753 al.c_body.data = US"simple"; al.c_body.len = 6;
1754 al.c_head = al.c_body;
1755 }
1756
1757/* Ask the dkim code to calc a bodyhash with those specs */
1758
1759if (!(b = arc_ams_setup_vfy_bodyhash(&al)))
1760 return US"dkim hash setup fail";
1761
1762/* Discard the reference; search again at verify time, knowing that one
1763should have been created here. */
1764
1765return NULL;
1766}
1767
1768
1769
1770/* A header line has been identified by DKIM processing.
1771
1772Arguments:
1773 g Header line
1774 is_vfy TRUE for verify mode or FALSE for signing mode
1775
1776Return:
1777 NULL for success, or an error string (probably unused)
1778*/
1779
1780const uschar *
1781arc_header_feed(gstring * g, BOOL is_vfy)
1782{
1783return is_vfy ? arc_header_vfy_feed(g) : arc_header_sign_feed(g);
1784}
1785
1786
1787
1788/******************************************************************************/
1789
9cffa436
JH
1790/* Construct the list of domains from the ARC chain after validation */
1791
1792uschar *
1793fn_arc_domains(void)
1794{
1795arc_set * as;
08bd2689 1796unsigned inst;
9cffa436
JH
1797gstring * g = NULL;
1798
08bd2689 1799for (as = arc_verify_ctx.arcset_chain, inst = 1; as; as = as->next, inst++)
9cffa436 1800 {
08bd2689
JH
1801 arc_line * hdr_as = as->hdr_as;
1802 if (hdr_as)
1803 {
1804 blob * d = &hdr_as->d;
1805
1806 for (; inst < as->instance; inst++)
c8599aad 1807 g = string_catn(g, US":", 1);
08bd2689
JH
1808
1809 g = d->data && d->len
1810 ? string_append_listele_n(g, ':', d->data, d->len)
c8599aad 1811 : string_catn(g, US":", 1);
08bd2689
JH
1812 }
1813 else
c8599aad 1814 g = string_catn(g, US":", 1);
9cffa436
JH
1815 }
1816return g ? g->s : US"";
1817}
1818
1819
c8599aad 1820/* Construct an Authentication-Results header portion, for the ARC module */
617d3932
JH
1821
1822gstring *
1823authres_arc(gstring * g)
1824{
1825if (arc_state)
1826 {
1827 arc_line * highest_ams;
978e78de 1828 int start = 0; /* Compiler quietening */
617d3932
JH
1829 DEBUG(D_acl) start = g->ptr;
1830
1831 g = string_append(g, 2, US";\n\tarc=", arc_state);
1832 if (arc_received_instance > 0)
1833 {
1834 g = string_append(g, 3, US" (i=",
93c931f8
JH
1835 string_sprintf("%d", arc_received_instance), US")");
1836 if (arc_state_reason)
1837 g = string_append(g, 3, US"(", arc_state_reason, US")");
1838 g = string_catn(g, US" header.s=", 10);
617d3932
JH
1839 highest_ams = arc_received->hdr_ams;
1840 g = string_catn(g, highest_ams->s.data, highest_ams->s.len);
1841
1842 g = string_append(g, 2,
1843 US" arc.oldest-pass=", string_sprintf("%d", arc_oldest_pass));
1844
1845 if (sender_host_address)
1846 g = string_append(g, 2, US" smtp.client-ip=", sender_host_address);
1847 }
b3d9ebf5
JH
1848 else if (arc_state_reason)
1849 g = string_append(g, 3, US" (", arc_state_reason, US")");
617d3932
JH
1850 DEBUG(D_acl) debug_printf("ARC: authres '%.*s'\n",
1851 g->ptr - start - 3, g->s + start + 3);
1852 }
1853else
1854 DEBUG(D_acl) debug_printf("ARC: no authres\n");
1855return g;
1856}
1857
1858
1859# endif /* SUPPORT_SPF */
1860#endif /* EXPERIMENTAL_ARC */
1861/* vi: aw ai sw=2
1862 */