* Exim - an Internet mail transport agent *
*************************************************/
/* Experimental ARC support for Exim
- Copyright (c) Jeremy Harris 2018
+ Copyright (c) Jeremy Harris 2018 - 2020
+ Copyright (c) The Exim Maintainers 2021 - 2022
License: GPL
+ SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "exim.h"
-#ifdef EXPERIMENTAL_ARC
-# if !defined SUPPORT_SPF
-# error SPF must also be enabled for ARC
-# elif defined DISABLE_DKIM
+#if defined EXPERIMENTAL_ARC
+# if defined DISABLE_DKIM
# error DKIM must also be enabled for ARC
# else
static time_t expire;
static hdr_rlist * headers_rlist;
static arc_ctx arc_sign_ctx = { NULL };
+static arc_ctx arc_verify_ctx = { NULL };
/******************************************************************************/
}
DEBUG(D_acl) debug_printf("ARC: new instance %u\n", i);
-*pas = as = store_get(sizeof(arc_set));
+*pas = as = store_get(sizeof(arc_set), GET_UNTAINTED);
memset(as, 0, sizeof(arc_set));
as->next = next;
as->prev = prev;
if (!instance_only)
{
- al->rawsig_no_b_val.data = store_get(h->slen + 1);
+ 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;
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_reset_unused(g);
+ gstring_release_unused(g);
bend = s;
break;
case 'h': /* bh= AMS body hash */
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_reset_unused(g);
+ gstring_release_unused(g);
break;
default:
return US"b? tag";
static uschar *
arc_insert_hdr(arc_ctx * ctx, header_line * h, unsigned off, unsigned hoff,
- BOOL instance_only)
+ BOOL instance_only, arc_line ** alp_ret)
{
-int i;
+unsigned i;
arc_set * as;
-arc_line * al = store_get(sizeof(arc_line)), ** alp;
+arc_line * al = store_get(sizeof(arc_line), GET_UNTAINTED), ** alp;
uschar * e;
memset(al, 0, sizeof(arc_line));
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;
}
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)))
+ TRUE, NULL)))
{
DEBUG(D_acl) debug_printf("inserting AAR: %s\n", e);
return US"inserting AAR";
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)))
+ instance_only, &ams)))
{
DEBUG(D_acl) debug_printf("inserting AMS: %s\n", e);
return US"inserting AMS";
}
/* defaults */
- /*XXX dubious selection of ams here */
- ams = ctx->arcset_chain->hdr_ams;
if (!ams->c.data)
{
ams->c_head.data = US"simple"; ams->c_head.len = 6;
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)))
+ instance_only, NULL)))
{
DEBUG(D_acl) debug_printf("inserting AS: %s\n", e);
return US"inserting AS";
DEBUG(D_acl) debug_printf("ARC: collecting arc sets\n");
for (h = header_list; h; h = h->next)
{
- r = store_get(sizeof(hdr_rlist));
+ r = store_get(sizeof(hdr_rlist), GET_UNTAINTED);
r->prev = rprev;
r->used = FALSE;
r->h = h;
const uschar * s;
int len;
-if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
+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");
len = Ustrlen(s);
DEBUG(D_acl) pdkim_quoteprint(s, len);
- exim_sha_update(&hhash_ctx, s, Ustrlen(s));
+ exim_sha_update_string(&hhash_ctx, s);
r->used = TRUE;
break;
}
pdkim_pubkey * p;
if (!(dns_txt = dkim_exim_query_dns_txt(string_sprintf("%.*s._domainkey.%.*s",
- al->s.len, al->s.data, al->d.len, al->d.data))))
+ (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;
static pdkim_bodyhash *
arc_ams_setup_vfy_bodyhash(arc_line * ams)
{
-int canon_head, canon_body;
+int canon_head = -1, canon_body = -1;
long bodylen;
if (!ams->c.data) ams->c.data = US"simple"; /* RFC 6376 (DKIM) default */
/* Setup the interface to the signing library */
-if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
+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";
}
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)))
int inst;
BOOL ams_fail_found = FALSE;
-if (!(as = ctx->arcset_chain))
+if (!(as = ctx->arcset_chain_last))
return US"none";
-for(inst = 0; as; as = as->next)
+for(inst = as->instance; as; as = as->prev, inst--)
{
- if ( as->instance != ++inst
- || !as->hdr_aar || !as->hdr_ams || !as->hdr_as
- || arc_cv_match(as->hdr_as, US"fail")
- )
- {
- arc_state_reason = string_sprintf("i=%d"
- " (cv, sequence or missing header)", as->instance);
- DEBUG(D_acl) debug_printf("ARC chain fail at %s\n", arc_state_reason);
- return US"fail";
- }
+ 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. */
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 = inst;
+arc_received_instance = arc_received->instance;
/* We can skip the latest-AMS validation, if we already did it. */
hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
-if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
+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");
/* 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)))
+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";
}
-hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
-
if ((errstr = exim_dkim_verify(&vctx,
pdkim_hashes[hashtype].exim_hashmethod,
&hhash_computed, &sighash)))
static const uschar *
arc_verify_seals(arc_ctx * ctx)
{
-arc_set * as = ctx->arcset_chain;
+arc_set * as = ctx->arcset_chain_last;
if (!as)
return US"none";
-while (as)
- {
- if (arc_seal_verify(ctx, as)) return US"fail";
- as = as->next;
- }
+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;
}
const uschar *
acl_verify_arc(void)
{
-arc_ctx ctx = { NULL };
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");
none, the ARC state is "none" and the algorithm stops here.
*/
-if ((res = arc_vfy_collect_hdrs(&ctx)))
+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
then the chain state is "fail" and the algorithm stops here.
*/
-if ((res = arc_headers_check(&ctx)))
+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
the algorithm is complete.
*/
-if ((res = arc_verify_seals(&ctx)))
+if ((res = arc_verify_seals(&arc_verify_ctx)))
goto out;
res = US"pass";
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));
+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;
h->slen = len;
h->text = US s;
-/* This works for either NL or CRLF lines; also nul-termination */
-while (*++s)
- if (*s == '\n' && s[1] != '\t' && s[1] != ' ') break;
-s++; /* move past end of line */
-
return r;
}
arc_sign_append_aar(gstring * g, arc_ctx * ctx,
const uschar * identity, int instance, blob * ar)
{
-int aar_off = g ? g->ptr : 0;
-arc_set * as = store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line));
+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_cat(g, string_sprintf(" i=%d; %s;\r\n\t", instance, identity));
+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;
|| (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;
g = string_catn(g, US"\r\n\t ", 5);
}
g = string_catn(g, US";\r\n", 3);
-gstring_reset_unused(g);
+gstring_release_unused(g);
string_from_gstring(g);
return g;
}
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));
+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_append(g, 7,
- ARC_HDR_AMS,
- US" i=", string_sprintf("%d", instance),
- US"; a=rsa-sha256; c=relaxed; d=", identity, /*XXX hardwired */
- US"; s=", selector);
+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_append(g, 2,
- US"; t=", string_sprintf("%lu", (u_long)now));
+ g = string_fmt_append(g, "; t=%lu", (u_long)now);
if (options & ARC_SIGN_OPT_EXPIRE)
- g = string_append(g, 2,
- US"; x=", string_sprintf("%lu", (u_long)expire));
-g = string_append(g, 3,
- US";\r\n\tbh=", pdkim_encode_base64(bodyhash),
- US";\r\n\th=");
+ 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 * privkey, unsigned options)
{
gstring * arcset;
-arc_set * as;
uschar * status = arc_ar_cv_status(ar);
-arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line));
+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 */
- 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 */
/* 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 (as = Ustrcmp(status, US"fail") == 0
+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. */
- h = as->hdr_aar->complete;
+ 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));
- h = as->hdr_ams->complete;
+ 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));
- h = as->hdr_as->complete;
+ 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));
}
/* 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;
}
arc_sign_init(void)
{
memset(&arc_sign_ctx, 0, sizeof(arc_sign_ctx));
+headers_rlist = NULL;
}
+/* 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.
/* Parse the signing specification */
-identity = string_nextinlist(&signspec, &sep, NULL, 0);
-selector = string_nextinlist(&signspec, &sep, NULL, 0);
-if ( !*identity | !*selector
- || !(privkey = string_nextinlist(&signspec, &sep, NULL, 0)) || !*privkey)
- {
- log_write(0, LOG_MAIN, "ARC: bad signing-specification (%s)",
- !*identity ? "identity" : !*selector ? "selector" : "private-key");
- return sigheaders ? sigheaders : string_get(0);
- }
+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)))
- return sigheaders ? sigheaders : string_get(0);
+ goto ret_sigheaders;
if ((opts = string_nextinlist(&signspec, &sep, NULL, 0)))
{
if (*(s += 6) == '=')
if (*++s == '+')
{
- if (!(expire = (time_t)atoi(++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(s);
+ expire = (time_t)atol(CS s);
else
{
if (!now) now = time(NULL);
if (!(arc_sign_find_ar(headers, identity, &ar)))
{
log_write(0, LOG_MAIN, "ARC: no Authentication-Results header for signing");
- return sigheaders ? sigheaders : string_get(0);
+ goto ret_sigheaders;
}
/* We previously built the data-struct for the existing ARC chain, if any, using a headers
including self (but with an empty b= in self)
*/
-g = arc_sign_prepend_as(g, &arc_sign_ctx, instance, identity, selector, &ar,
+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. */
-g = string_catn(g, sigheaders->s, sigheaders->ptr);
-(void) string_from_gstring(g);
-gstring_reset_unused(g);
-return g;
+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;
}
if ((errstr = arc_parse_line(&al, &h, ARC_HDRLEN_AMS, FALSE)))
{
DEBUG(D_acl) if (errstr) debug_printf("ARC: %s\n", errstr);
- return US"line parsing error";
+ 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 */
should have been created here. */
return NULL;
+
+badline:
+ return US"line parsing error";
}
/******************************************************************************/
-/* Construct an Authenticate-Results header portion, for the ARC module */
+/* 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)
g = string_append(g, 2, US";\n\tarc=", arc_state);
if (arc_received_instance > 0)
{
- g = string_append(g, 3, US" (i=",
- string_sprintf("%d", arc_received_instance), US")");
+ 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_append(g, 2,
- US" arc.oldest-pass=", string_sprintf("%d", arc_oldest_pass));
+ g = string_fmt_append(g, " arc.oldest-pass=%d", arc_oldest_pass);
if (sender_host_address)
- g = string_append(g, 2, US" smtp.client-ip=", 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")");
}
-# endif /* SUPPORT_SPF */
+# endif /* DISABLE_DKIM */
#endif /* EXPERIMENTAL_ARC */
/* vi: aw ai sw=2
*/
git://git.exim.org / exim.git / blobdiff