X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/2b2cfa838f206b5d97a120722861f42780bc6a6a..29041f6cd4b0d8a0ee109ed0a0efaaf929d6a804:/src/src/arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index 52c1c7625..c1407af60 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -2,11 +2,12 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 /* Experimental ARC support for Exim
-   Copyright (c) Jeremy Harris 2018
+   Copyright (c) Jeremy Harris 2018 - 2020
    License: GPL
 */
 
 #include "exim.h"
+#if defined EXPERIMENTAL_ARC
 # if defined DISABLE_DKIM
 #  error DKIM must also be enabled for ARC
 # else
@@ -380,7 +381,7 @@ 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;
@@ -400,6 +401,7 @@ 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;
 }
 
@@ -423,7 +425,7 @@ 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";
@@ -442,15 +444,13 @@ 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;
@@ -468,7 +468,7 @@ 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";
@@ -735,7 +735,7 @@ 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";
@@ -964,7 +964,7 @@ 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";
@@ -1192,7 +1192,7 @@ 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);
 arc_line * al = (arc_line *)(as+1);
@@ -1418,10 +1418,10 @@ 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);
 header_line * h = (header_line *)(al+1);
+uschar * badline_str;
 
 gstring * hdata = NULL;
 int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6);	/*XXX hardwired */
@@ -1439,6 +1439,7 @@ 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 */
 
@@ -1462,18 +1463,25 @@ 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));
   }
 
@@ -1490,6 +1498,11 @@ 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;
 }
 
 
@@ -1544,6 +1557,23 @@ 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.
@@ -1577,15 +1607,18 @@ 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)
+if (  !(identity = string_nextinlist(&signspec, &sep, NULL, 0)) || !*identity
+   || !(selector = string_nextinlist(&signspec, &sep, NULL, 0)) || !*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);
+  s = !*identity ? US"identity" : !*selector ? US"selector" : US"private-key";
+  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);
 
@@ -1705,6 +1738,11 @@ if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
 (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);
+  return sigheaders ? sigheaders : string_get(0);
 }