-/*************************************************
-* Exim - an Internet mail transport agent *
-*************************************************/
-/* Experimental ARC support for Exim
- Copyright (c) Jeremy Harris 2018 - 2020
- Copyright (c) The Exim Maintainers 2021 - 2022
- License: GPL
-*/
-
-#include "exim.h"
-#if defined EXPERIMENTAL_ARC
-# if defined DISABLE_DKIM
-# error DKIM must also be enabled for ARC
-# else
-
-# include "functions.h"
-# include "pdkim/pdkim.h"
-# include "pdkim/signing.h"
-
-extern pdkim_ctx * dkim_verify_ctx;
-extern pdkim_ctx dkim_sign_ctx;
-
-#define ARC_SIGN_OPT_TSTAMP BIT(0)
-#define ARC_SIGN_OPT_EXPIRE BIT(1)
-
-#define ARC_SIGN_DEFAULT_EXPIRE_DELTA (60 * 60 * 24 * 30) /* one month */
-
-/******************************************************************************/
-
-typedef struct hdr_rlist {
- struct hdr_rlist * prev;
- BOOL used;
- header_line * h;
-} hdr_rlist;
-
-typedef struct arc_line {
- header_line * complete; /* including the header name; nul-term */
- uschar * relaxed;
-
- /* identified tag contents */
- /*XXX t= for AS? */
- blob i;
- blob cv;
- blob a;
- blob b;
- blob bh;
- blob d;
- blob h;
- blob s;
- blob c;
- blob l;
-
- /* tag content sub-portions */
- blob a_algo;
- blob a_hash;
-
- blob c_head;
- blob c_body;
-
- /* modified copy of b= field in line */
- blob rawsig_no_b_val;
-} arc_line;
-
-typedef struct arc_set {
- struct arc_set * next;
- struct arc_set * prev;
-
- unsigned instance;
- arc_line * hdr_aar;
- arc_line * hdr_ams;
- arc_line * hdr_as;
-
- const uschar * ams_verify_done;
- BOOL ams_verify_passed;
-} arc_set;
-
-typedef struct arc_ctx {
- arc_set * arcset_chain;
- arc_set * arcset_chain_last;
-} arc_ctx;
-
-#define ARC_HDR_AAR US"ARC-Authentication-Results:"
-#define ARC_HDRLEN_AAR 27
-#define ARC_HDR_AMS US"ARC-Message-Signature:"
-#define ARC_HDRLEN_AMS 22
-#define ARC_HDR_AS US"ARC-Seal:"
-#define ARC_HDRLEN_AS 9
-#define HDR_AR US"Authentication-Results:"
-#define HDRLEN_AR 23
-
-static time_t now;
-static time_t expire;
-static hdr_rlist * headers_rlist;
-static arc_ctx arc_sign_ctx = { NULL };
-static arc_ctx arc_verify_ctx = { NULL };
-
-
-/******************************************************************************/
-
-
-/* Get the instance number from the header.
-Return 0 on error */
-static unsigned
-arc_instance_from_hdr(const arc_line * al)
-{
-const uschar * s = al->i.data;
-if (!s || !al->i.len) return 0;
-return (unsigned) atoi(CCS s);
-}
-
-
-static uschar *
-skip_fws(uschar * s)
-{
-uschar c = *s;
-while (c && (c == ' ' || c == '\t' || c == '\n' || c == '\r')) c = *++s;
-return s;
-}
-
-
-/* Locate instance struct on chain, inserting a new one if
-needed. The chain is in increasing-instance-number order
-by the "next" link, and we have a "prev" link also.
-*/
-
-static arc_set *
-arc_find_set(arc_ctx * ctx, unsigned i)
-{
-arc_set ** pas, * as, * next, * prev;
-
-for (pas = &ctx->arcset_chain, prev = NULL, next = ctx->arcset_chain;
- as = *pas; pas = &as->next)
- {
- if (as->instance > i) break;
- if (as->instance == i)
- {
- DEBUG(D_acl) debug_printf("ARC: existing instance %u\n", i);
- return as;
- }
- next = as->next;
- prev = as;
- }
-
-DEBUG(D_acl) debug_printf("ARC: new instance %u\n", i);
-*pas = as = store_get(sizeof(arc_set), GET_UNTAINTED);
-memset(as, 0, sizeof(arc_set));
-as->next = next;
-as->prev = prev;
-as->instance = i;
-if (next)
- next->prev = as;
-else
- ctx->arcset_chain_last = as;
-return as;
-}
-
-
-
-/* Insert a tag content into the line structure.
-Note this is a reference to existing data, not a copy.
-Check for already-seen tag.
-The string-pointer is on the '=' for entry. Update it past the
-content (to the ;) on return;
-*/
-
-static uschar *
-arc_insert_tagvalue(arc_line * al, unsigned loff, uschar ** ss)
-{
-uschar * s = *ss;
-uschar c = *++s;
-blob * b = (blob *)(US al + loff);
-size_t len = 0;
-
-/* [FWS] tag-value [FWS] */
-
-if (b->data) return US"fail";
-s = skip_fws(s); /* FWS */
-
-b->data = s;
-while ((c = *s) && c != ';') { len++; s++; }
-*ss = s;
-while (len && ((c = s[-1]) == ' ' || c == '\t' || c == '\n' || c == '\r'))
- { s--; len--; } /* FWS */
-b->len = len;
-return NULL;
-}
-
-
-/* Inspect a header line, noting known tag fields.
-Check for duplicates. */
-
-static uschar *
-arc_parse_line(arc_line * al, header_line * h, unsigned off, BOOL instance_only)
-{
-uschar * s = h->text + off;
-uschar * r = NULL; /* compiler-quietening */
-uschar c;
-
-al->complete = h;
-
-if (!instance_only)
- {
- al->rawsig_no_b_val.data = store_get(h->slen + 1, GET_TAINTED);
- memcpy(al->rawsig_no_b_val.data, h->text, off); /* copy the header name blind */
- r = al->rawsig_no_b_val.data + off;
- al->rawsig_no_b_val.len = off;
- }
-
-/* tag-list = tag-spec *( ";" tag-spec ) [ ";" ] */
-
-while ((c = *s))
- {
- char tagchar;
- uschar * t;
- unsigned i = 0;
- uschar * fieldstart = s;
- uschar * bstart = NULL, * bend;
-
- /* tag-spec = [FWS] tag-name [FWS] "=" [FWS] tag-value [FWS] */
-
- s = skip_fws(s); /* FWS */
- if (!*s) break;
-/* debug_printf("%s: consider '%s'\n", __FUNCTION__, s); */
- tagchar = *s++;
- s = skip_fws(s); /* FWS */
- if (!*s) break;
-
- if (!instance_only || tagchar == 'i') switch (tagchar)
- {
- case 'a': /* a= AMS algorithm */
- {
- if (*s != '=') return US"no 'a' value";
- if (arc_insert_tagvalue(al, offsetof(arc_line, a), &s)) return US"a tag dup";
-
- /* substructure: algo-hash (eg. rsa-sha256) */
-
- t = al->a_algo.data = al->a.data;
- while (*t != '-')
- if (!*t++ || ++i > al->a.len) return US"no '-' in 'a' value";
- al->a_algo.len = i;
- if (*t++ != '-') return US"no '-' in 'a' value";
- al->a_hash.data = t;
- al->a_hash.len = al->a.len - i - 1;
- }
- break;
- case 'b':
- {
- gstring * g = NULL;
-
- switch (*s)
- {
- case '=': /* b= AMS signature */
- if (al->b.data) return US"already b data";
- bstart = s+1;
-
- /* The signature can have FWS inserted in the content;
- make a stripped copy */
-
- while ((c = *++s) && c != ';')
- if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
- g = string_catn(g, s, 1);
- if (!g) return US"no b= value";
- al->b.data = string_from_gstring(g);
- al->b.len = g->ptr;
- gstring_release_unused(g);
- bend = s;
- break;
- case 'h': /* bh= AMS body hash */
- s = skip_fws(++s); /* FWS */
- if (*s != '=') return US"no bh value";
- if (al->bh.data) return US"already bh data";
-
- /* The bodyhash can have FWS inserted in the content;
- make a stripped copy */
-
- while ((c = *++s) && c != ';')
- if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
- g = string_catn(g, s, 1);
- if (!g) return US"no bh= value";
- al->bh.data = string_from_gstring(g);
- al->bh.len = g->ptr;
- gstring_release_unused(g);
- break;
- default:
- return US"b? tag";
- }
- }
- break;
- case 'c':
- switch (*s)
- {
- case '=': /* c= AMS canonicalisation */
- if (arc_insert_tagvalue(al, offsetof(arc_line, c), &s)) return US"c tag dup";
-
- /* substructure: head/body (eg. relaxed/simple)) */
-
- t = al->c_head.data = al->c.data;
- while (isalpha(*t))
- if (!*t++ || ++i > al->a.len) break;
- al->c_head.len = i;
- if (*t++ == '/') /* /body is optional */
- {
- al->c_body.data = t;
- al->c_body.len = al->c.len - i - 1;
- }
- else
- {
- al->c_body.data = US"simple";
- al->c_body.len = 6;
- }
- break;
- case 'v': /* cv= AS validity */
- if (*++s != '=') return US"cv tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, cv), &s)) return US"cv tag dup";
- break;
- default:
- return US"c? tag";
- }
- break;
- case 'd': /* d= AMS domain */
- if (*s != '=') return US"d tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, d), &s)) return US"d tag dup";
- break;
- case 'h': /* h= AMS headers */
- if (*s != '=') return US"h tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, h), &s)) return US"h tag dup";
- break;
- case 'i': /* i= ARC set instance */
- if (*s != '=') return US"i tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, i), &s)) return US"i tag dup";
- if (instance_only) goto done;
- break;
- case 'l': /* l= bodylength */
- if (*s != '=') return US"l tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, l), &s)) return US"l tag dup";
- break;
- case 's': /* s= AMS selector */
- if (*s != '=') return US"s tag val";
- if (arc_insert_tagvalue(al, offsetof(arc_line, s), &s)) return US"s tag dup";
- break;
- }
-
- while ((c = *s) && c != ';') s++;
- if (c) s++; /* ; after tag-spec */
-
- /* for all but the b= tag, copy the field including FWS. For the b=,
- drop the tag content. */
-
- if (!instance_only)
- if (bstart)
- {
- size_t n = bstart - fieldstart;
- memcpy(r, fieldstart, n); /* FWS "b=" */
- r += n;
- al->rawsig_no_b_val.len += n;
- n = s - bend;
- memcpy(r, bend, n); /* FWS ";" */
- r += n;
- al->rawsig_no_b_val.len += n;
- }
- else
- {
- size_t n = s - fieldstart;
- memcpy(r, fieldstart, n);
- r += n;
- al->rawsig_no_b_val.len += n;
- }
- }
-
-if (!instance_only)
- *r = '\0';
-
-done:
-/* debug_printf("%s: finshed\n", __FUNCTION__); */
-return NULL;
-}
-
-
-/* Insert one header line in the correct set of the chain,
-adding instances as needed and checking for duplicate lines.
-*/
-
-static uschar *
-arc_insert_hdr(arc_ctx * ctx, header_line * h, unsigned off, unsigned hoff,
- BOOL instance_only, arc_line ** alp_ret)
-{
-unsigned i;
-arc_set * as;
-arc_line * al = store_get(sizeof(arc_line), GET_UNTAINTED), ** alp;
-uschar * e;
-
-memset(al, 0, sizeof(arc_line));
-
-if ((e = arc_parse_line(al, h, off, instance_only)))
- {
- DEBUG(D_acl) if (e) debug_printf("ARC: %s\n", e);
- return US"line parse";
- }
-if (!(i = arc_instance_from_hdr(al))) return US"instance find";
-if (i > 50) return US"overlarge instance number";
-if (!(as = arc_find_set(ctx, i))) return US"set find";
-if (*(alp = (arc_line **)(US as + hoff))) return US"dup hdr";
-
-*alp = al;
-if (alp_ret) *alp_ret = al;
-return NULL;
-}
-
-
-
-
-static const uschar *
-arc_try_header(arc_ctx * ctx, header_line * h, BOOL instance_only)
-{
-const uschar * e;
-
-/*debug_printf("consider hdr '%s'\n", h->text);*/
-if (strncmpic(ARC_HDR_AAR, h->text, ARC_HDRLEN_AAR) == 0)
- {
- DEBUG(D_acl)
- {
- int len = h->slen;
- uschar * s;
- for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
- s--, len--;
- debug_printf("ARC: found AAR: %.*s\n", len, h->text);
- }
- if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AAR, offsetof(arc_set, hdr_aar),
- TRUE, NULL)))
- {
- DEBUG(D_acl) debug_printf("inserting AAR: %s\n", e);
- return US"inserting AAR";
- }
- }
-else if (strncmpic(ARC_HDR_AMS, h->text, ARC_HDRLEN_AMS) == 0)
- {
- arc_line * ams;
-
- DEBUG(D_acl)
- {
- int len = h->slen;
- uschar * s;
- for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
- s--, len--;
- debug_printf("ARC: found AMS: %.*s\n", len, h->text);
- }
- if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AMS, offsetof(arc_set, hdr_ams),
- instance_only, &ams)))
- {
- DEBUG(D_acl) debug_printf("inserting AMS: %s\n", e);
- return US"inserting AMS";
- }
-
- /* defaults */
- if (!ams->c.data)
- {
- ams->c_head.data = US"simple"; ams->c_head.len = 6;
- ams->c_body = ams->c_head;
- }
- }
-else if (strncmpic(ARC_HDR_AS, h->text, ARC_HDRLEN_AS) == 0)
- {
- DEBUG(D_acl)
- {
- int len = h->slen;
- uschar * s;
- for (s = h->text + h->slen; s[-1] == '\r' || s[-1] == '\n'; )
- s--, len--;
- debug_printf("ARC: found AS: %.*s\n", len, h->text);
- }
- if ((e = arc_insert_hdr(ctx, h, ARC_HDRLEN_AS, offsetof(arc_set, hdr_as),
- instance_only, NULL)))
- {
- DEBUG(D_acl) debug_printf("inserting AS: %s\n", e);
- return US"inserting AS";
- }
- }
-return NULL;
-}
-
-
-
-/* Gather the chain of arc sets from the headers.
-Check for duplicates while that is done. Also build the
-reverse-order headers list;
-
-Return: ARC state if determined, eg. by lack of any ARC chain.
-*/
-
-static const uschar *
-arc_vfy_collect_hdrs(arc_ctx * ctx)
-{
-header_line * h;
-hdr_rlist * r = NULL, * rprev = NULL;
-const uschar * e;
-
-DEBUG(D_acl) debug_printf("ARC: collecting arc sets\n");
-for (h = header_list; h; h = h->next)
- {
- r = store_get(sizeof(hdr_rlist), GET_UNTAINTED);
- r->prev = rprev;
- r->used = FALSE;
- r->h = h;
- rprev = r;
-
- if ((e = arc_try_header(ctx, h, FALSE)))
- {
- arc_state_reason = string_sprintf("collecting headers: %s", e);
- return US"fail";
- }
- }
-headers_rlist = r;
-
-if (!ctx->arcset_chain) return US"none";
-return NULL;
-}
-
-
-static BOOL
-arc_cv_match(arc_line * al, const uschar * s)
-{
-return Ustrncmp(s, al->cv.data, al->cv.len) == 0;
-}
-
-/******************************************************************************/
-
-/* Return the hash of headers from the message that the AMS claims it
-signed.
-*/
-
-static void
-arc_get_verify_hhash(arc_ctx * ctx, arc_line * ams, blob * hhash)
-{
-const uschar * headernames = string_copyn(ams->h.data, ams->h.len);
-const uschar * hn;
-int sep = ':';
-hdr_rlist * r;
-BOOL relaxed = Ustrncmp(US"relaxed", ams->c_head.data, ams->c_head.len) == 0;
-int hashtype = pdkim_hashname_to_hashtype(
- ams->a_hash.data, ams->a_hash.len);
-hctx hhash_ctx;
-const uschar * s;
-int len;
-
-if ( hashtype == -1
- || !exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
- {
- DEBUG(D_acl)
- debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
- return;
- }
-
-/* For each headername in the list from the AMS (walking in order)
-walk the message headers in reverse order, adding to the hash any
-found for the first time. For that last point, maintain used-marks
-on the list of message headers. */
-
-DEBUG(D_acl) debug_printf("ARC: AMS header data for verification:\n");
-
-for (r = headers_rlist; r; r = r->prev)
- r->used = FALSE;
-while ((hn = string_nextinlist(&headernames, &sep, NULL, 0)))
- for (r = headers_rlist; r; r = r->prev)
- if ( !r->used
- && strncasecmp(CCS (s = r->h->text), CCS hn, Ustrlen(hn)) == 0
- )
- {
- if (relaxed) s = pdkim_relax_header_n(s, r->h->slen, TRUE);
-
- len = Ustrlen(s);
- DEBUG(D_acl) pdkim_quoteprint(s, len);
- exim_sha_update_string(&hhash_ctx, s);
- r->used = TRUE;
- break;
- }
-
-/* Finally add in the signature header (with the b= tag stripped); no CRLF */
-
-s = ams->rawsig_no_b_val.data, len = ams->rawsig_no_b_val.len;
-if (relaxed)
- len = Ustrlen(s = pdkim_relax_header_n(s, len, FALSE));
-DEBUG(D_acl) pdkim_quoteprint(s, len);
-exim_sha_update(&hhash_ctx, s, len);
-
-exim_sha_finish(&hhash_ctx, hhash);
-DEBUG(D_acl)
- { debug_printf("ARC: header hash: "); pdkim_hexprint(hhash->data, hhash->len); }
-return;
-}
-
-
-
-
-static pdkim_pubkey *
-arc_line_to_pubkey(arc_line * al)
-{
-uschar * dns_txt;
-pdkim_pubkey * p;
-
-if (!(dns_txt = dkim_exim_query_dns_txt(string_sprintf("%.*s._domainkey.%.*s",
- (int)al->s.len, al->s.data, (int)al->d.len, al->d.data))))
- {
- DEBUG(D_acl) debug_printf("pubkey dns lookup fail\n");
- return NULL;
- }
-
-if ( !(p = pdkim_parse_pubkey_record(dns_txt))
- || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0)
- )
- {
- DEBUG(D_acl) debug_printf("pubkey dns lookup format error\n");
- return NULL;
- }
-
-/* If the pubkey limits use to specified hashes, reject unusable
-signatures. XXX should we have looked for multiple dns records? */
-
-if (p->hashes)
- {
- const uschar * list = p->hashes, * ele;
- int sep = ':';
-
- while ((ele = string_nextinlist(&list, &sep, NULL, 0)))
- if (Ustrncmp(ele, al->a_hash.data, al->a_hash.len) == 0) break;
- if (!ele)
- {
- DEBUG(D_acl) debug_printf("pubkey h=%s vs sig a=%.*s\n",
- p->hashes, (int)al->a.len, al->a.data);
- return NULL;
- }
- }
-return p;
-}
-
-
-
-
-static pdkim_bodyhash *
-arc_ams_setup_vfy_bodyhash(arc_line * ams)
-{
-int canon_head = -1, canon_body = -1;
-long bodylen;
-
-if (!ams->c.data) ams->c.data = US"simple"; /* RFC 6376 (DKIM) default */
-pdkim_cstring_to_canons(ams->c.data, ams->c.len, &canon_head, &canon_body);
-bodylen = ams->l.data
- ? strtol(CS string_copyn(ams->l.data, ams->l.len), NULL, 10) : -1;
-
-return pdkim_set_bodyhash(dkim_verify_ctx,
- pdkim_hashname_to_hashtype(ams->a_hash.data, ams->a_hash.len),
- canon_body,
- bodylen);
-}
-
-
-
-/* Verify an AMS. This is a DKIM-sig header, but with an ARC i= tag
-and without a DKIM v= tag.
-*/
-
-static const uschar *
-arc_ams_verify(arc_ctx * ctx, arc_set * as)
-{
-arc_line * ams = as->hdr_ams;
-pdkim_bodyhash * b;
-pdkim_pubkey * p;
-blob sighash;
-blob hhash;
-ev_ctx vctx;
-int hashtype;
-const uschar * errstr;
-
-as->ams_verify_done = US"in-progress";
-
-/* Check the AMS has all the required tags:
- "a=" algorithm
- "b=" signature
- "bh=" body hash
- "d=" domain (for key lookup)
- "h=" headers (included in signature)
- "s=" key-selector (for key lookup)
-*/
-if ( !ams->a.data || !ams->b.data || !ams->bh.data || !ams->d.data
- || !ams->h.data || !ams->s.data)
- {
- as->ams_verify_done = arc_state_reason = US"required tag missing";
- return US"fail";
- }
-
-
-/* The bodyhash should have been created earlier, and the dkim code should
-have managed calculating it during message input. Find the reference to it. */
-
-if (!(b = arc_ams_setup_vfy_bodyhash(ams)))
- {
- as->ams_verify_done = arc_state_reason = US"internal hash setup error";
- return US"fail";
- }
-
-DEBUG(D_acl)
- {
- debug_printf("ARC i=%d AMS Body bytes hashed: %lu\n"
- " Body %.*s computed: ",
- as->instance, b->signed_body_bytes,
- (int)ams->a_hash.len, ams->a_hash.data);
- pdkim_hexprint(CUS b->bh.data, b->bh.len);
- }
-
-/* We know the bh-tag blob is of a nul-term string, so safe as a string */
-
-if ( !ams->bh.data
- || (pdkim_decode_base64(ams->bh.data, &sighash), sighash.len != b->bh.len)
- || memcmp(sighash.data, b->bh.data, b->bh.len) != 0
- )
- {
- DEBUG(D_acl)
- {
- debug_printf("ARC i=%d AMS Body hash from headers: ", as->instance);
- pdkim_hexprint(sighash.data, sighash.len);
- debug_printf("ARC i=%d AMS Body hash did NOT match\n", as->instance);
- }
- return as->ams_verify_done = arc_state_reason = US"AMS body hash miscompare";
- }
-
-DEBUG(D_acl) debug_printf("ARC i=%d AMS Body hash compared OK\n", as->instance);
-
-/* Get the public key from DNS */
-
-if (!(p = arc_line_to_pubkey(ams)))
- return as->ams_verify_done = arc_state_reason = US"pubkey problem";
-
-/* We know the b-tag blob is of a nul-term string, so safe as a string */
-pdkim_decode_base64(ams->b.data, &sighash);
-
-arc_get_verify_hhash(ctx, ams, &hhash);
-
-/* Setup the interface to the signing library */
-
-if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx, NULL)))
- {
- DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
- as->ams_verify_done = arc_state_reason = US"internal sigverify init error";
- return US"fail";
- }
-
-hashtype = pdkim_hashname_to_hashtype(ams->a_hash.data, ams->a_hash.len);
-if (hashtype == -1)
- {
- DEBUG(D_acl) debug_printf("ARC i=%d AMS verify bad a_hash\n", as->instance);
- return as->ams_verify_done = arc_state_reason = US"AMS sig nonverify";
- }
-
-if ((errstr = exim_dkim_verify(&vctx,
- pdkim_hashes[hashtype].exim_hashmethod, &hhash, &sighash)))
- {
- DEBUG(D_acl) debug_printf("ARC i=%d AMS verify %s\n", as->instance, errstr);
- return as->ams_verify_done = arc_state_reason = US"AMS sig nonverify";
- }
-
-DEBUG(D_acl) debug_printf("ARC i=%d AMS verify pass\n", as->instance);
-as->ams_verify_passed = TRUE;
-return NULL;
-}
-
-
-
-/* Check the sets are instance-continuous and that all
-members are present. Check that no arc_seals are "fail".
-Set the highest instance number global.
-Verify the latest AMS.
-*/
-static uschar *
-arc_headers_check(arc_ctx * ctx)
-{
-arc_set * as;
-int inst;
-BOOL ams_fail_found = FALSE;
-
-if (!(as = ctx->arcset_chain_last))
- return US"none";
-
-for(inst = as->instance; as; as = as->prev, inst--)
- {
- if (as->instance != inst)
- arc_state_reason = string_sprintf("i=%d (sequence; expected %d)",
- as->instance, inst);
- else if (!as->hdr_aar || !as->hdr_ams || !as->hdr_as)
- arc_state_reason = string_sprintf("i=%d (missing header)", as->instance);
- else if (arc_cv_match(as->hdr_as, US"fail"))
- arc_state_reason = string_sprintf("i=%d (cv)", as->instance);
- else
- goto good;
-
- DEBUG(D_acl) debug_printf("ARC chain fail at %s\n", arc_state_reason);
- return US"fail";
-
- good:
- /* Evaluate the oldest-pass AMS validation while we're here.
- It does not affect the AS chain validation but is reported as
- auxilary info. */
-
- if (!ams_fail_found)
- if (arc_ams_verify(ctx, as))
- ams_fail_found = TRUE;
- else
- arc_oldest_pass = inst;
- arc_state_reason = NULL;
- }
-if (inst != 0)
- {
- arc_state_reason = string_sprintf("(sequence; expected i=%d)", inst);
- DEBUG(D_acl) debug_printf("ARC chain fail %s\n", arc_state_reason);
- return US"fail";
- }
-
-arc_received = ctx->arcset_chain_last;
-arc_received_instance = arc_received->instance;
-
-/* We can skip the latest-AMS validation, if we already did it. */
-
-as = ctx->arcset_chain_last;
-if (!as->ams_verify_passed)
- {
- if (as->ams_verify_done)
- {
- arc_state_reason = as->ams_verify_done;
- return US"fail";
- }
- if (!!arc_ams_verify(ctx, as))
- return US"fail";
- }
-return NULL;
-}
-
-
-/******************************************************************************/
-static const uschar *
-arc_seal_verify(arc_ctx * ctx, arc_set * as)
-{
-arc_line * hdr_as = as->hdr_as;
-arc_set * as2;
-int hashtype;
-hctx hhash_ctx;
-blob hhash_computed;
-blob sighash;
-ev_ctx vctx;
-pdkim_pubkey * p;
-const uschar * errstr;
-
-DEBUG(D_acl) debug_printf("ARC: AS vfy i=%d\n", as->instance);
-/*
- 1. If the value of the "cv" tag on that seal is "fail", the
- chain state is "fail" and the algorithm stops here. (This
- step SHOULD be skipped if the earlier step (2.1) was
- performed) [it was]
-
- 2. In Boolean nomenclature: if ((i == 1 && cv != "none") or (cv
- == "none" && i != 1)) then the chain state is "fail" and the
- algorithm stops here (note that the ordering of the logic is
- structured for short-circuit evaluation).
-*/
-
-if ( as->instance == 1 && !arc_cv_match(hdr_as, US"none")
- || arc_cv_match(hdr_as, US"none") && as->instance != 1
- )
- {
- arc_state_reason = US"seal cv state";
- return US"fail";
- }
-
-/*
- 3. Initialize a hash function corresponding to the "a" tag of
- the ARC-Seal.
-*/
-
-hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
-
-if ( hashtype == -1
- || !exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
- {
- DEBUG(D_acl)
- debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
- arc_state_reason = US"seal hash setup error";
- return US"fail";
- }
-
-/*
- 4. Compute the canonicalized form of the ARC header fields, in
- the order described in Section 5.4.2, using the "relaxed"
- header canonicalization defined in Section 3.4.2 of
- [RFC6376]. Pass the canonicalized result to the hash
- function.
-
-Headers are CRLF-separated, but the last one is not crlf-terminated.
-*/
-
-DEBUG(D_acl) debug_printf("ARC: AS header data for verification:\n");
-for (as2 = ctx->arcset_chain;
- as2 && as2->instance <= as->instance;
- as2 = as2->next)
- {
- arc_line * al;
- uschar * s;
- int len;
-
- al = as2->hdr_aar;
- if (!(s = al->relaxed))
- al->relaxed = s = pdkim_relax_header_n(al->complete->text,
- al->complete->slen, TRUE);
- len = Ustrlen(s);
- DEBUG(D_acl) pdkim_quoteprint(s, len);
- exim_sha_update(&hhash_ctx, s, len);
-
- al = as2->hdr_ams;
- if (!(s = al->relaxed))
- al->relaxed = s = pdkim_relax_header_n(al->complete->text,
- al->complete->slen, TRUE);
- len = Ustrlen(s);
- DEBUG(D_acl) pdkim_quoteprint(s, len);
- exim_sha_update(&hhash_ctx, s, len);
-
- al = as2->hdr_as;
- if (as2->instance == as->instance)
- s = pdkim_relax_header_n(al->rawsig_no_b_val.data,
- al->rawsig_no_b_val.len, FALSE);
- else if (!(s = al->relaxed))
- al->relaxed = s = pdkim_relax_header_n(al->complete->text,
- al->complete->slen, TRUE);
- len = Ustrlen(s);
- DEBUG(D_acl) pdkim_quoteprint(s, len);
- exim_sha_update(&hhash_ctx, s, len);
- }
-
-/*
- 5. Retrieve the final digest from the hash function.
-*/
-
-exim_sha_finish(&hhash_ctx, &hhash_computed);
-DEBUG(D_acl)
- {
- debug_printf("ARC i=%d AS Header %.*s computed: ",
- as->instance, (int)hdr_as->a_hash.len, hdr_as->a_hash.data);
- pdkim_hexprint(hhash_computed.data, hhash_computed.len);
- }
-
-
-/*
- 6. Retrieve the public key identified by the "s" and "d" tags in
- the ARC-Seal, as described in Section 4.1.6.
-*/
-
-if (!(p = arc_line_to_pubkey(hdr_as)))
- return US"pubkey problem";
-
-/*
- 7. Determine whether the signature portion ("b" tag) of the ARC-
- Seal and the digest computed above are valid according to the
- public key. (See also Section Section 8.4 for failure case
- handling)
-
- 8. If the signature is not valid, the chain state is "fail" and
- the algorithm stops here.
-*/
-
-/* We know the b-tag blob is of a nul-term string, so safe as a string */
-pdkim_decode_base64(hdr_as->b.data, &sighash);
-
-if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx, NULL)))
- {
- DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
- return US"fail";
- }
-
-if ((errstr = exim_dkim_verify(&vctx,
- pdkim_hashes[hashtype].exim_hashmethod,
- &hhash_computed, &sighash)))
- {
- DEBUG(D_acl)
- debug_printf("ARC i=%d AS headers verify: %s\n", as->instance, errstr);
- arc_state_reason = US"seal sigverify error";
- return US"fail";
- }
-
-DEBUG(D_acl) debug_printf("ARC: AS vfy i=%d pass\n", as->instance);
-return NULL;
-}
-
-
-static const uschar *
-arc_verify_seals(arc_ctx * ctx)
-{
-arc_set * as = ctx->arcset_chain_last;
-
-if (!as)
- return US"none";
-
-for ( ; as; as = as->prev) if (arc_seal_verify(ctx, as)) return US"fail";
-
-DEBUG(D_acl) debug_printf("ARC: AS vfy overall pass\n");
-return NULL;
-}
-/******************************************************************************/
-
-/* Do ARC verification. Called from DATA ACL, on a verify = arc
-condition. No arguments; we are checking globals.
-
-Return: The ARC state, or NULL on error.
-*/
-
-const uschar *
-acl_verify_arc(void)
-{
-const uschar * res;
-
-memset(&arc_verify_ctx, 0, sizeof(arc_verify_ctx));
-
-if (!dkim_verify_ctx)
- {
- DEBUG(D_acl) debug_printf("ARC: no DKIM verify context\n");
- return NULL;
- }
-
-/* AS evaluation, per
-https://tools.ietf.org/html/draft-ietf-dmarc-arc-protocol-10#section-6
-*/
-/* 1. Collect all ARC sets currently on the message. If there were
- none, the ARC state is "none" and the algorithm stops here.
-*/
-
-if ((res = arc_vfy_collect_hdrs(&arc_verify_ctx)))
- goto out;
-
-/* 2. If the form of any ARC set is invalid (e.g., does not contain
- exactly one of each of the three ARC-specific header fields),
- then the chain state is "fail" and the algorithm stops here.
-
- 1. To avoid the overhead of unnecessary computation and delay
- from crypto and DNS operations, the cv value for all ARC-
- Seal(s) MAY be checked at this point. If any of the values
- are "fail", then the overall state of the chain is "fail" and
- the algorithm stops here.
-
- 3. Conduct verification of the ARC-Message-Signature header field
- bearing the highest instance number. If this verification fails,
- then the chain state is "fail" and the algorithm stops here.
-*/
-
-if ((res = arc_headers_check(&arc_verify_ctx)))
- goto out;
-
-/* 4. For each ARC-Seal from the "N"th instance to the first, apply the
- following logic:
-
- 1. If the value of the "cv" tag on that seal is "fail", the
- chain state is "fail" and the algorithm stops here. (This
- step SHOULD be skipped if the earlier step (2.1) was
- performed)
-
- 2. In Boolean nomenclature: if ((i == 1 && cv != "none") or (cv
- == "none" && i != 1)) then the chain state is "fail" and the
- algorithm stops here (note that the ordering of the logic is
- structured for short-circuit evaluation).
-
- 3. Initialize a hash function corresponding to the "a" tag of
- the ARC-Seal.
-
- 4. Compute the canonicalized form of the ARC header fields, in
- the order described in Section 5.4.2, using the "relaxed"
- header canonicalization defined in Section 3.4.2 of
- [RFC6376]. Pass the canonicalized result to the hash
- function.
-
- 5. Retrieve the final digest from the hash function.
-
- 6. Retrieve the public key identified by the "s" and "d" tags in
- the ARC-Seal, as described in Section 4.1.6.
-
- 7. Determine whether the signature portion ("b" tag) of the ARC-
- Seal and the digest computed above are valid according to the
- public key. (See also Section Section 8.4 for failure case
- handling)
-
- 8. If the signature is not valid, the chain state is "fail" and
- the algorithm stops here.
-
- 5. If all seals pass validation, then the chain state is "pass", and
- the algorithm is complete.
-*/
-
-if ((res = arc_verify_seals(&arc_verify_ctx)))
- goto out;
-
-res = US"pass";
-
-out:
- return res;
-}
-
-/******************************************************************************/
-
-/* Prepend the header to the rlist */
-
-static hdr_rlist *
-arc_rlist_entry(hdr_rlist * list, const uschar * s, int len)
-{
-hdr_rlist * r = store_get(sizeof(hdr_rlist) + sizeof(header_line), GET_UNTAINTED);
-header_line * h = r->h = (header_line *)(r+1);
-
-r->prev = list;
-r->used = FALSE;
-h->next = NULL;
-h->type = 0;
-h->slen = len;
-h->text = US s;
-
-return r;
-}
-
-
-/* Walk the given headers strings identifying each header, and construct
-a reverse-order list.
-*/
-
-static hdr_rlist *
-arc_sign_scan_headers(arc_ctx * ctx, gstring * sigheaders)
-{
-const uschar * s;
-hdr_rlist * rheaders = NULL;
-
-s = sigheaders ? sigheaders->s : NULL;
-if (s) while (*s)
- {
- const uschar * s2 = s;
-
- /* This works for either NL or CRLF lines; also nul-termination */
- while (*++s2)
- if (*s2 == '\n' && s2[1] != '\t' && s2[1] != ' ') break;
- s2++; /* move past end of line */
-
- rheaders = arc_rlist_entry(rheaders, s, s2 - s);
- s = s2;
- }
-return rheaders;
-}
-
-
-
-/* Return the A-R content, without identity, with line-ending and
-NUL termination. */
-
-static BOOL
-arc_sign_find_ar(header_line * headers, const uschar * identity, blob * ret)
-{
-header_line * h;
-int ilen = Ustrlen(identity);
-
-ret->data = NULL;
-for(h = headers; h; h = h->next)
- {
- uschar * s = h->text, c;
- int len = h->slen;
-
- if (Ustrncmp(s, HDR_AR, HDRLEN_AR) != 0) continue;
- s += HDRLEN_AR, len -= HDRLEN_AR; /* header name */
- while ( len > 0
- && (c = *s) && (c == ' ' || c == '\t' || c == '\r' || c == '\n'))
- s++, len--; /* FWS */
- if (Ustrncmp(s, identity, ilen) != 0) continue;
- s += ilen; len -= ilen; /* identity */
- if (len <= 0) continue;
- if ((c = *s) && c == ';') s++, len--; /* identity terminator */
- while ( len > 0
- && (c = *s) && (c == ' ' || c == '\t' || c == '\r' || c == '\n'))
- s++, len--; /* FWS */
- if (len <= 0) continue;
- ret->data = s;
- ret->len = len;
- return TRUE;
- }
-return FALSE;
-}
-
-
-
-/* Append a constructed AAR including CRLF. Add it to the arc_ctx too. */
-
-static gstring *
-arc_sign_append_aar(gstring * g, arc_ctx * ctx,
- const uschar * identity, int instance, blob * ar)
-{
-int aar_off = gstring_length(g);
-arc_set * as =
- store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line), GET_UNTAINTED);
-arc_line * al = (arc_line *)(as+1);
-header_line * h = (header_line *)(al+1);
-
-g = string_catn(g, ARC_HDR_AAR, ARC_HDRLEN_AAR);
-g = string_fmt_append(g, " i=%d; %s;\r\n\t", instance, identity);
-g = string_catn(g, US ar->data, ar->len);
-
-h->slen = g->ptr - aar_off;
-h->text = g->s + aar_off;
-al->complete = h;
-as->next = NULL;
-as->prev = ctx->arcset_chain_last;
-as->instance = instance;
-as->hdr_aar = al;
-if (instance == 1)
- ctx->arcset_chain = as;
-else
- ctx->arcset_chain_last->next = as;
-ctx->arcset_chain_last = as;
-
-DEBUG(D_transport) debug_printf("ARC: AAR '%.*s'\n", h->slen - 2, h->text);
-return g;
-}
-
-
-
-static BOOL
-arc_sig_from_pseudoheader(gstring * hdata, int hashtype, const uschar * privkey,
- blob * sig, const uschar * why)
-{
-hashmethod hm = /*sig->keytype == KEYTYPE_ED25519*/ FALSE
- ? HASH_SHA2_512 : pdkim_hashes[hashtype].exim_hashmethod;
-blob hhash;
-es_ctx sctx;
-const uschar * errstr;
-
-DEBUG(D_transport)
- {
- hctx hhash_ctx;
- debug_printf("ARC: %s header data for signing:\n", why);
- pdkim_quoteprint(hdata->s, hdata->ptr);
-
- (void) exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod);
- exim_sha_update(&hhash_ctx, hdata->s, hdata->ptr);
- exim_sha_finish(&hhash_ctx, &hhash);
- debug_printf("ARC: header hash: "); pdkim_hexprint(hhash.data, hhash.len);
- }
-
-if (FALSE /*need hash for Ed25519 or GCrypt signing*/ )
- {
- hctx hhash_ctx;
- (void) exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod);
- exim_sha_update(&hhash_ctx, hdata->s, hdata->ptr);
- exim_sha_finish(&hhash_ctx, &hhash);
- }
-else
- {
- hhash.data = hdata->s;
- hhash.len = hdata->ptr;
- }
-
-if ( (errstr = exim_dkim_signing_init(privkey, &sctx))
- || (errstr = exim_dkim_sign(&sctx, hm, &hhash, sig)))
- {
- log_write(0, LOG_MAIN, "ARC: %s signing: %s\n", why, errstr);
- DEBUG(D_transport)
- debug_printf("private key, or private-key file content, was: '%s'\n",
- privkey);
- return FALSE;
- }
-return TRUE;
-}
-
-
-
-static gstring *
-arc_sign_append_sig(gstring * g, blob * sig)
-{
-/*debug_printf("%s: raw sig ", __FUNCTION__); pdkim_hexprint(sig->data, sig->len);*/
-sig->data = pdkim_encode_base64(sig);
-sig->len = Ustrlen(sig->data);
-for (;;)
- {
- int len = MIN(sig->len, 74);
- g = string_catn(g, sig->data, len);
- if ((sig->len -= len) == 0) break;
- sig->data += len;
- g = string_catn(g, US"\r\n\t ", 5);
- }
-g = string_catn(g, US";\r\n", 3);
-gstring_release_unused(g);
-string_from_gstring(g);
-return g;
-}
-
-
-/* Append a constructed AMS including CRLF. Add it to the arc_ctx too. */
-
-static gstring *
-arc_sign_append_ams(gstring * g, arc_ctx * ctx, int instance,
- const uschar * identity, const uschar * selector, blob * bodyhash,
- hdr_rlist * rheaders, const uschar * privkey, unsigned options)
-{
-uschar * s;
-gstring * hdata = NULL;
-int col;
-int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6); /*XXX hardwired */
-blob sig;
-int ams_off;
-arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line), GET_UNTAINTED);
-header_line * h = (header_line *)(al+1);
-
-/* debug_printf("%s\n", __FUNCTION__); */
-
-/* Construct the to-be-signed AMS pseudo-header: everything but the sig. */
-
-ams_off = g->ptr;
-g = string_fmt_append(g, "%s i=%d; a=rsa-sha256; c=relaxed; d=%s; s=%s",
- ARC_HDR_AMS, instance, identity, selector); /*XXX hardwired a= */
-if (options & ARC_SIGN_OPT_TSTAMP)
- g = string_fmt_append(g, "; t=%lu", (u_long)now);
-if (options & ARC_SIGN_OPT_EXPIRE)
- g = string_fmt_append(g, "; x=%lu", (u_long)expire);
-g = string_fmt_append(g, ";\r\n\tbh=%s;\r\n\th=",
- pdkim_encode_base64(bodyhash));
-
-for(col = 3; rheaders; rheaders = rheaders->prev)
- {
- const uschar * hnames = US"DKIM-Signature:" PDKIM_DEFAULT_SIGN_HEADERS;
- uschar * name, * htext = rheaders->h->text;
- int sep = ':';
-
- /* Spot headers of interest */
-
- while ((name = string_nextinlist(&hnames, &sep, NULL, 0)))
- {
- int len = Ustrlen(name);
- if (strncasecmp(CCS htext, CCS name, len) == 0)
- {
- /* If too long, fold line in h= field */
-
- if (col + len > 78) g = string_catn(g, US"\r\n\t ", 5), col = 3;
-
- /* Add name to h= list */
-
- g = string_catn(g, name, len);
- g = string_catn(g, US":", 1);
- col += len + 1;
-
- /* Accumulate header for hashing/signing */
-
- hdata = string_cat(hdata,
- pdkim_relax_header_n(htext, rheaders->h->slen, TRUE)); /*XXX hardwired */
- break;
- }
- }
- }
-
-/* Lose the last colon from the h= list */
-
-if (g->s[g->ptr - 1] == ':') g->ptr--;
-
-g = string_catn(g, US";\r\n\tb=;", 7);
-
-/* Include the pseudo-header in the accumulation */
-
-s = pdkim_relax_header_n(g->s + ams_off, g->ptr - ams_off, FALSE);
-hdata = string_cat(hdata, s);
-
-/* Calculate the signature from the accumulation */
-/*XXX does that need further relaxation? there are spaces embedded in the b= strings! */
-
-if (!arc_sig_from_pseudoheader(hdata, hashtype, privkey, &sig, US"AMS"))
- return NULL;
-
-/* Lose the trailing semicolon from the psuedo-header, and append the signature
-(folded over lines) and termination to complete it. */
-
-g->ptr--;
-g = arc_sign_append_sig(g, &sig);
-
-h->slen = g->ptr - ams_off;
-h->text = g->s + ams_off;
-al->complete = h;
-ctx->arcset_chain_last->hdr_ams = al;
-
-DEBUG(D_transport) debug_printf("ARC: AMS '%.*s'\n", h->slen - 2, h->text);
-return g;
-}
-
-
-
-/* Look for an arc= result in an A-R header blob. We know that its data
-happens to be a NUL-term string. */
-
-static uschar *
-arc_ar_cv_status(blob * ar)
-{
-const uschar * resinfo = ar->data;
-int sep = ';';
-uschar * methodspec, * s;
-
-while ((methodspec = string_nextinlist(&resinfo, &sep, NULL, 0)))
- if (Ustrncmp(methodspec, US"arc=", 4) == 0)
- {
- uschar c;
- for (s = methodspec += 4;
- (c = *s) && c != ';' && c != ' ' && c != '\r' && c != '\n'; ) s++;
- return string_copyn(methodspec, s - methodspec);
- }
-return US"none";
-}
-
-
-
-/* Build the AS header and prepend it */
-
-static gstring *
-arc_sign_prepend_as(gstring * arcset_interim, arc_ctx * ctx,
- int instance, const uschar * identity, const uschar * selector, blob * ar,
- const uschar * privkey, unsigned options)
-{
-gstring * arcset;
-uschar * status = arc_ar_cv_status(ar);
-arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line), GET_UNTAINTED);
-header_line * h = (header_line *)(al+1);
-uschar * badline_str;
-
-gstring * hdata = NULL;
-int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6); /*XXX hardwired */
-blob sig;
-
-/*
-- Generate AS
- - no body coverage
- - no h= tag; implicit coverage
- - arc status from A-R
- - if fail:
- - coverage is just the new ARC set
- including self (but with an empty b= in self)
- - if non-fail:
- - all ARC set headers, set-number order, aar then ams then as,
- including self (but with an empty b= in self)
-*/
-DEBUG(D_transport) debug_printf("ARC: building AS for status '%s'\n", status);
-
-/* Construct the AS except for the signature */
-
-arcset = string_append(NULL, 9,
- ARC_HDR_AS,
- US" i=", string_sprintf("%d", instance),
- US"; cv=", status,
- US"; a=rsa-sha256; d=", identity, /*XXX hardwired */
- US"; s=", selector); /*XXX same as AMS */
-if (options & ARC_SIGN_OPT_TSTAMP)
- arcset = string_append(arcset, 2,
- US"; t=", string_sprintf("%lu", (u_long)now));
-arcset = string_cat(arcset,
- US";\r\n\t b=;");
-
-h->slen = arcset->ptr;
-h->text = arcset->s;
-al->complete = h;
-ctx->arcset_chain_last->hdr_as = al;
-
-/* For any but "fail" chain-verify status, walk the entire chain in order by
-instance. For fail, only the new arc-set. Accumulate the elements walked. */
-
-for (arc_set * as = Ustrcmp(status, US"fail") == 0
- ? ctx->arcset_chain_last : ctx->arcset_chain;
- as; as = as->next)
- {
- arc_line * l;
- /* Accumulate AAR then AMS then AS. Relaxed canonicalisation
- is required per standard. */
-
- badline_str = US"aar";
- if (!(l = as->hdr_aar)) goto badline;
- h = l->complete;
- hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
- badline_str = US"ams";
- if (!(l = as->hdr_ams)) goto badline;
- h = l->complete;
- hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
- badline_str = US"as";
- if (!(l = as->hdr_as)) goto badline;
- h = l->complete;
- hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, !!as->next));
- }
-
-/* Calculate the signature from the accumulation */
-
-if (!arc_sig_from_pseudoheader(hdata, hashtype, privkey, &sig, US"AS"))
- return NULL;
-
-/* Lose the trailing semicolon */
-arcset->ptr--;
-arcset = arc_sign_append_sig(arcset, &sig);
-DEBUG(D_transport) debug_printf("ARC: AS '%.*s'\n", arcset->ptr - 2, arcset->s);
-
-/* Finally, append the AMS and AAR to the new AS */
-
-return string_catn(arcset, arcset_interim->s, arcset_interim->ptr);
-
-badline:
- DEBUG(D_transport)
- debug_printf("ARC: while building AS, missing %s in chain\n", badline_str);
- return NULL;
-}
-
-
-/**************************************/
-
-/* Return pointer to pdkim_bodyhash for given hash method, creating new
-method if needed.
-*/
-
-void *
-arc_ams_setup_sign_bodyhash(void)
-{
-int canon_head, canon_body;
-
-DEBUG(D_transport) debug_printf("ARC: requesting bodyhash\n");
-pdkim_cstring_to_canons(US"relaxed", 7, &canon_head, &canon_body); /*XXX hardwired */
-return pdkim_set_bodyhash(&dkim_sign_ctx,
- pdkim_hashname_to_hashtype(US"sha256", 6), /*XXX hardwired */
- canon_body,
- -1);
-}
-
-
-
-void
-arc_sign_init(void)
-{
-memset(&arc_sign_ctx, 0, sizeof(arc_sign_ctx));
-}
-
-
-
-/* A "normal" header line, identified by DKIM processing. These arrive before
-the call to arc_sign(), which carries any newly-created DKIM headers - and
-those go textually before the normal ones in the message.
-
-We have to take the feed from DKIM as, in the transport-filter case, the
-headers are not in memory at the time of the call to arc_sign().
-
-Take a copy of the header and construct a reverse-order list.
-Also parse ARC-chain headers and build the chain struct, retaining pointers
-into the copies.
-*/
-
-static const uschar *
-arc_header_sign_feed(gstring * g)
-{
-uschar * s = string_copyn(g->s, g->ptr);
-headers_rlist = arc_rlist_entry(headers_rlist, s, g->ptr);
-return arc_try_header(&arc_sign_ctx, headers_rlist->h, TRUE);
-}
-
-
-
-/* Per RFCs 6376, 7489 the only allowed chars in either an ADMD id
-or a selector are ALPHA/DIGGIT/'-'/'.'
-
-Check, to help catch misconfigurations such as a missing selector
-element in the arc_sign list.
-*/
-
-static BOOL
-arc_valid_id(const uschar * s)
-{
-for (uschar c; c = *s++; )
- if (!isalnum(c) && c != '-' && c != '.') return FALSE;
-return TRUE;
-}
-
-
-
-/* ARC signing. Called from the smtp transport, if the arc_sign option is set.
-The dkim_exim_sign() function has already been called, so will have hashed the
-message body for us so long as we requested a hash previously.
-
-Arguments:
- signspec Three-element colon-sep list: identity, selector, privkey.
- Optional fourth element: comma-sep list of options.
- Already expanded
- sigheaders Any signature headers already generated, eg. by DKIM, or NULL
- errstr Error string
-
-Return value
- Set of headers to prepend to the message, including the supplied sigheaders
- but not the plainheaders.
-*/
-
-gstring *
-arc_sign(const uschar * signspec, gstring * sigheaders, uschar ** errstr)
-{
-const uschar * identity, * selector, * privkey, * opts, * s;
-unsigned options = 0;
-int sep = 0;
-header_line * headers;
-hdr_rlist * rheaders;
-blob ar;
-int instance;
-gstring * g = NULL;
-pdkim_bodyhash * b;
-
-expire = now = 0;
-
-/* Parse the signing specification */
-
-if (!(identity = string_nextinlist(&signspec, &sep, NULL, 0)) || !*identity)
- { s = US"identity"; goto bad_arg_ret; }
-if (!(selector = string_nextinlist(&signspec, &sep, NULL, 0)) || !*selector)
- { s = US"selector"; goto bad_arg_ret; }
-if (!(privkey = string_nextinlist(&signspec, &sep, NULL, 0)) || !*privkey)
- { s = US"privkey"; goto bad_arg_ret; }
-if (!arc_valid_id(identity))
- { s = US"identity"; goto bad_arg_ret; }
-if (!arc_valid_id(selector))
- { s = US"selector"; goto bad_arg_ret; }
-if (*privkey == '/' && !(privkey = expand_file_big_buffer(privkey)))
- goto ret_sigheaders;
-
-if ((opts = string_nextinlist(&signspec, &sep, NULL, 0)))
- {
- int osep = ',';
- while ((s = string_nextinlist(&opts, &osep, NULL, 0)))
- if (Ustrcmp(s, "timestamps") == 0)
- {
- options |= ARC_SIGN_OPT_TSTAMP;
- if (!now) now = time(NULL);
- }
- else if (Ustrncmp(s, "expire", 6) == 0)
- {
- options |= ARC_SIGN_OPT_EXPIRE;
- if (*(s += 6) == '=')
- if (*++s == '+')
- {
- if (!(expire = (time_t)atoi(CS ++s)))
- expire = ARC_SIGN_DEFAULT_EXPIRE_DELTA;
- if (!now) now = time(NULL);
- expire += now;
- }
- else
- expire = (time_t)atol(CS s);
- else
- {
- if (!now) now = time(NULL);
- expire = now + ARC_SIGN_DEFAULT_EXPIRE_DELTA;
- }
- }
- }
-
-DEBUG(D_transport) debug_printf("ARC: sign for %s\n", identity);
-
-/* Make an rlist of any new DKIM headers, then add the "normals" rlist to it.
-Then scan the list for an A-R header. */
-
-string_from_gstring(sigheaders);
-if ((rheaders = arc_sign_scan_headers(&arc_sign_ctx, sigheaders)))
- {
- hdr_rlist ** rp;
- for (rp = &headers_rlist; *rp; ) rp = &(*rp)->prev;
- *rp = rheaders;
- }
-
-/* Finally, build a normal-order headers list */
-/*XXX only needed for hunt-the-AR? */
-/*XXX also, we really should be accepting any number of ADMD-matching ARs */
- {
- header_line * hnext = NULL;
- for (rheaders = headers_rlist; rheaders;
- hnext = rheaders->h, rheaders = rheaders->prev)
- rheaders->h->next = hnext;
- headers = hnext;
- }
-
-if (!(arc_sign_find_ar(headers, identity, &ar)))
- {
- log_write(0, LOG_MAIN, "ARC: no Authentication-Results header for signing");
- goto ret_sigheaders;
- }
-
-/* We previously built the data-struct for the existing ARC chain, if any, using a headers
-feed from the DKIM module. Use that to give the instance number for the ARC set we are
-about to build. */
-
-DEBUG(D_transport)
- if (arc_sign_ctx.arcset_chain_last)
- debug_printf("ARC: existing chain highest instance: %d\n",
- arc_sign_ctx.arcset_chain_last->instance);
- else
- debug_printf("ARC: no existing chain\n");
-
-instance = arc_sign_ctx.arcset_chain_last ? arc_sign_ctx.arcset_chain_last->instance + 1 : 1;
-
-/*
-- Generate AAR
- - copy the A-R; prepend i= & identity
-*/
-
-g = arc_sign_append_aar(g, &arc_sign_ctx, identity, instance, &ar);
-
-/*
-- Generate AMS
- - Looks fairly like a DKIM sig
- - Cover all DKIM sig headers as well as the usuals
- - ? oversigning?
- - Covers the data
- - we must have requested a suitable bodyhash previously
-*/
-
-b = arc_ams_setup_sign_bodyhash();
-g = arc_sign_append_ams(g, &arc_sign_ctx, instance, identity, selector,
- &b->bh, headers_rlist, privkey, options);
-
-/*
-- Generate AS
- - no body coverage
- - no h= tag; implicit coverage
- - arc status from A-R
- - if fail:
- - coverage is just the new ARC set
- including self (but with an empty b= in self)
- - if non-fail:
- - all ARC set headers, set-number order, aar then ams then as,
- including self (but with an empty b= in self)
-*/
-
-if (g)
- g = arc_sign_prepend_as(g, &arc_sign_ctx, instance, identity, selector, &ar,
- privkey, options);
-
-/* Finally, append the dkim headers and return the lot. */
-
-if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
-
-out:
- if (!g) return string_get(1);
- (void) string_from_gstring(g);
- gstring_release_unused(g);
- return g;
-
-
-bad_arg_ret:
- log_write(0, LOG_MAIN, "ARC: bad signing-specification (%s)", s);
-ret_sigheaders:
- g = sigheaders;
- goto out;
-}
-
-
-/******************************************************************************/
-
-/* Check to see if the line is an AMS and if so, set up to validate it.
-Called from the DKIM input processing. This must be done now as the message
-body data is hashed during input.
-
-We call the DKIM code to request a body-hash; it has the facility already
-and the hash parameters might be common with other requests.
-*/
-
-static const uschar *
-arc_header_vfy_feed(gstring * g)
-{
-header_line h;
-arc_line al;
-pdkim_bodyhash * b;
-uschar * errstr;
-
-if (!dkim_verify_ctx) return US"no dkim context";
-
-if (strncmpic(ARC_HDR_AMS, g->s, ARC_HDRLEN_AMS) != 0) return US"not AMS";
-
-DEBUG(D_receive) debug_printf("ARC: spotted AMS header\n");
-/* Parse the AMS header */
-
-h.next = NULL;
-h.slen = g->size;
-h.text = g->s;
-memset(&al, 0, sizeof(arc_line));
-if ((errstr = arc_parse_line(&al, &h, ARC_HDRLEN_AMS, FALSE)))
- {
- DEBUG(D_acl) if (errstr) debug_printf("ARC: %s\n", errstr);
- goto badline;
- }
-
-if (!al.a_hash.data)
- {
- DEBUG(D_acl) debug_printf("ARC: no a_hash from '%.*s'\n", h.slen, h.text);
- goto badline;
- }
-
-/* defaults */
-if (!al.c.data)
- {
- al.c_body.data = US"simple"; al.c_body.len = 6;
- al.c_head = al.c_body;
- }
-
-/* Ask the dkim code to calc a bodyhash with those specs */
-
-if (!(b = arc_ams_setup_vfy_bodyhash(&al)))
- return US"dkim hash setup fail";
-
-/* Discard the reference; search again at verify time, knowing that one
-should have been created here. */
-
-return NULL;
-
-badline:
- return US"line parsing error";
-}
-
-
-
-/* A header line has been identified by DKIM processing.
-
-Arguments:
- g Header line
- is_vfy TRUE for verify mode or FALSE for signing mode
-
-Return:
- NULL for success, or an error string (probably unused)
-*/
-
-const uschar *
-arc_header_feed(gstring * g, BOOL is_vfy)
-{
-return is_vfy ? arc_header_vfy_feed(g) : arc_header_sign_feed(g);
-}
-
-
-
-/******************************************************************************/
-
-/* Construct the list of domains from the ARC chain after validation */
-
-uschar *
-fn_arc_domains(void)
-{
-arc_set * as;
-unsigned inst;
-gstring * g = NULL;
-
-for (as = arc_verify_ctx.arcset_chain, inst = 1; as; as = as->next, inst++)
- {
- arc_line * hdr_as = as->hdr_as;
- if (hdr_as)
- {
- blob * d = &hdr_as->d;
-
- for (; inst < as->instance; inst++)
- g = string_catn(g, US":", 1);
-
- g = d->data && d->len
- ? string_append_listele_n(g, ':', d->data, d->len)
- : string_catn(g, US":", 1);
- }
- else
- g = string_catn(g, US":", 1);
- }
-return g ? g->s : US"";
-}
-
-
-/* Construct an Authentication-Results header portion, for the ARC module */
-
-gstring *
-authres_arc(gstring * g)
-{
-if (arc_state)
- {
- arc_line * highest_ams;
- int start = 0; /* Compiler quietening */
- DEBUG(D_acl) start = g->ptr;
-
- g = string_append(g, 2, US";\n\tarc=", arc_state);
- if (arc_received_instance > 0)
- {
- g = string_fmt_append(g, " (i=%d)", arc_received_instance);
- if (arc_state_reason)
- g = string_append(g, 3, US"(", arc_state_reason, US")");
- g = string_catn(g, US" header.s=", 10);
- highest_ams = arc_received->hdr_ams;
- g = string_catn(g, highest_ams->s.data, highest_ams->s.len);
-
- g = string_fmt_append(g, " arc.oldest-pass=%d", arc_oldest_pass);
-
- if (sender_host_address)
- g = string_append(g, 2, US" smtp.remote-ip=", sender_host_address);
- }
- else if (arc_state_reason)
- g = string_append(g, 3, US" (", arc_state_reason, US")");
- DEBUG(D_acl) debug_printf("ARC: authres '%.*s'\n",
- g->ptr - start - 3, g->s + start + 3);
- }
-else
- DEBUG(D_acl) debug_printf("ARC: no authres\n");
-return g;
-}
-
-
-# endif /* DISABLE_DKIM */
-#endif /* EXPERIMENTAL_ARC */
-/* vi: aw ai sw=2
- */
git://git.exim.org / exim.git / blobdiff