X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/7d4064fb2ca678359a6fa29a30a00c08fa75e70a..a85c067ba6c6940512cf57ec213277a370d87e70:/src/src/arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index 8a94015b3..e3a2b3dad 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -2,8 +2,10 @@
 *     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-only
 */
 
 #include "exim.h"
@@ -141,7 +143,7 @@ for (pas = &ctx->arcset_chain, prev = NULL, next = ctx->arcset_chain;
   }
 
 DEBUG(D_acl) debug_printf("ARC: new instance %u\n", i);
-*pas = as = store_get(sizeof(arc_set), FALSE);
+*pas = as = store_get(sizeof(arc_set), GET_UNTAINTED);
 memset(as, 0, sizeof(arc_set));
 as->next = next;
 as->prev = prev;
@@ -199,7 +201,7 @@ al->complete = h;
 
 if (!instance_only)
   {
-  al->rawsig_no_b_val.data = store_get(h->slen + 1, TRUE);	/* tainted */
+  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;
@@ -381,11 +383,11 @@ 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)
+  BOOL instance_only, arc_line ** alp_ret)
 {
 unsigned i;
 arc_set * as;
-arc_line * al = store_get(sizeof(arc_line), FALSE), ** alp;
+arc_line * al = store_get(sizeof(arc_line), GET_UNTAINTED), ** alp;
 uschar * e;
 
 memset(al, 0, sizeof(arc_line));
@@ -401,6 +403,7 @@ 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;
 }
 
@@ -424,7 +427,7 @@ if (strncmpic(ARC_HDR_AAR, h->text, ARC_HDRLEN_AAR) == 0)
     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";
@@ -443,15 +446,13 @@ else if (strncmpic(ARC_HDR_AMS, h->text, ARC_HDRLEN_AMS) == 0)
     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;
@@ -469,7 +470,7 @@ else if (strncmpic(ARC_HDR_AS, h->text, ARC_HDRLEN_AS) == 0)
     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";
@@ -497,7 +498,7 @@ 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), FALSE);
+  r = store_get(sizeof(hdr_rlist), GET_UNTAINTED);
   r->prev = rprev;
   r->used = FALSE;
   r->h = h;
@@ -569,7 +570,7 @@ while ((hn = string_nextinlist(&headernames, &sep, NULL, 0)))
 
       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;
       }
@@ -736,7 +737,7 @@ 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)))
+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";
@@ -965,7 +966,7 @@ if (!(p = arc_line_to_pubkey(hdr_as)))
 /* 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";
@@ -1103,7 +1104,7 @@ out:
 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), FALSE);
+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;
@@ -1113,11 +1114,6 @@ h->type = 0;
 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;
 }
 
@@ -1193,9 +1189,9 @@ static gstring *
 arc_sign_append_aar(gstring * g, arc_ctx * ctx,
   const uschar * identity, int instance, blob * ar)
 {
-int aar_off = g ? g->ptr : 0;
+int aar_off = gstring_length(g);
 arc_set * as =
-  store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line), FALSE);
+  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);
 
@@ -1305,7 +1301,7 @@ 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), FALSE);
+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__); */
@@ -1419,10 +1415,10 @@ arc_sign_prepend_as(gstring * arcset_interim, arc_ctx * ctx,
   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), FALSE);
+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 */
@@ -1440,6 +1436,7 @@ blob sig;
       - 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 */
 
@@ -1463,18 +1460,25 @@ 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 (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));
   }
 
@@ -1491,6 +1495,11 @@ 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;
 }
 
 
@@ -1519,6 +1528,7 @@ void
 arc_sign_init(void)
 {
 memset(&arc_sign_ctx, 0, sizeof(arc_sign_ctx));
+headers_rlist = NULL;
 }
 
 
@@ -1545,6 +1555,23 @@ 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.
@@ -1578,17 +1605,18 @@ expire = now = 0;
 
 /* 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)))
   {
@@ -1647,7 +1675,7 @@ if ((rheaders = arc_sign_scan_headers(&arc_sign_ctx, sigheaders)))
 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
@@ -1703,9 +1731,19 @@ if (g)
 /* Finally, append the dkim headers and return the lot. */
 
 if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
-(void) string_from_gstring(g);
-gstring_release_unused(g);
-return g;
+
+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;
 }