X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/b4dd15a736795e6d06a79febbae76a926964bbb0..38089ca5c8f4c06092324099fc38494f8491b53c:/src/src/arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index e7ebb9719..a68ab6eb4 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -2,15 +2,13 @@
 *     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"
-#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
 
@@ -143,7 +141,7 @@ 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));
+*pas = as = store_get(sizeof(arc_set), FALSE);
 memset(as, 0, sizeof(arc_set));
 as->next = next;
 as->prev = prev;
@@ -201,7 +199,7 @@ al->complete = h;
 
 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, TRUE);	/* 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;
@@ -263,7 +261,7 @@ while ((c = *s))
 	  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 */
@@ -280,7 +278,7 @@ while ((c = *s))
 	  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";
@@ -383,11 +381,11 @@ 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)), ** alp;
+arc_line * al = store_get(sizeof(arc_line), FALSE), ** alp;
 uschar * e;
 
 memset(al, 0, sizeof(arc_line));
@@ -403,6 +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;
 }
 
@@ -426,7 +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";
@@ -445,15 +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;
@@ -471,7 +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";
@@ -499,7 +496,7 @@ 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));
+  r = store_get(sizeof(hdr_rlist), FALSE);
   r->prev = rprev;
   r->used = FALSE;
   r->h = h;
@@ -544,7 +541,8 @@ hctx hhash_ctx;
 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");
@@ -599,7 +597,7 @@ uschar * dns_txt;
 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;
@@ -639,7 +637,7 @@ return p;
 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 */
@@ -737,7 +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";
@@ -745,6 +743,11 @@ if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
   }
 
 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)))
@@ -871,7 +874,8 @@ if (  as->instance == 1 && !arc_cv_match(hdr_as, US"none")
 
 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");
@@ -960,14 +964,12 @@ 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";
   }
 
-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)))
@@ -1100,7 +1102,7 @@ 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));
+hdr_rlist * r = store_get(sizeof(hdr_rlist) + sizeof(header_line), FALSE);
 header_line * h = r->h = (header_line *)(r+1);
 
 r->prev = list;
@@ -1190,8 +1192,9 @@ 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;
-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), FALSE);
 arc_line * al = (arc_line *)(as+1);
 header_line * h = (header_line *)(al+1);
 
@@ -1282,7 +1285,7 @@ for (;;)
   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;
 }
@@ -1301,7 +1304,7 @@ 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));
+arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line), FALSE);
 header_line * h = (header_line *)(al+1);
 
 /* debug_printf("%s\n", __FUNCTION__); */
@@ -1415,10 +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));
+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 */
@@ -1436,6 +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 */
 
@@ -1459,18 +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));
   }
 
@@ -1487,6 +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;
 }
 
 
@@ -1541,6 +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.
@@ -1574,15 +1607,16 @@ 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);
 
@@ -1700,8 +1734,13 @@ if (g)
 
 if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
 (void) string_from_gstring(g);
-gstring_reset_unused(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);
 }
 
 
@@ -1737,7 +1776,13 @@ 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);
-  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 */
@@ -1756,6 +1801,9 @@ if (!(b = arc_ams_setup_vfy_bodyhash(&al)))
 should have been created here. */
 
 return NULL;
+
+badline:
+  return US"line parsing error";
 }
 
 
@@ -1847,7 +1895,7 @@ return g;
 }
 
 
-# endif /* SUPPORT_SPF */
+# endif /* DISABLE_DKIM */
 #endif /* EXPERIMENTAL_ARC */
 /* vi: aw ai sw=2
  */