ARC: For signing, accept A-R header lacking ARC info as equivalent to "none"

[exim.git] / src / src / arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index 28438e65eba1786cf4867976ac6c97bd9345c7c1..f4ae096bc26731a6dbd15eb19dcb15392c59c75b 100644 (file)
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -66,7 +66,7 @@ typedef struct arc_set {
   arc_line *           hdr_ams;
   arc_line *           hdr_as;
 
-  BOOL                 ams_verify_done;
+  const uschar *       ams_verify_done;
   BOOL                 ams_verify_passed;
 } arc_set;
 
@@ -495,7 +495,10 @@ for (h = header_list; h; h = h->next)
   rprev = r;
 
   if ((e = arc_try_header(ctx, h, FALSE)))
-    return e;
+    {
+    arc_state_reason = string_sprintf("collecting headers: %s", e);
+    return US"fail";
+    }
   }
 headers_rlist = r;
 
@@ -561,11 +564,11 @@ while ((hn = string_nextinlist(&headernames, &sep, NULL, 0)))
       break;
       }
 
-/* Finally add in the signature header (with the b= tag stripped) */
+/* 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, TRUE));
+  len = Ustrlen(s = pdkim_relax_header_n(s, len, FALSE));
 DEBUG(D_acl) pdkim_quoteprint(s, len);
 exim_sha_update(&hhash_ctx, s, len);
 
@@ -644,7 +647,7 @@ return pdkim_set_bodyhash(dkim_verify_ctx,
 and without a DKIM v= tag.
 */
 
-static uschar *
+static const uschar *
 arc_ams_verify(arc_ctx * ctx, arc_set * as)
 {
 arc_line * ams = as->hdr_ams;
@@ -656,7 +659,7 @@ ev_ctx vctx;
 int hashtype;
 const uschar * errstr;
 
-as->ams_verify_done = TRUE;
+as->ams_verify_done = US"in-progress";
 
 /* Check the AMS has all the required tags:
    "a="  algorithm
@@ -668,14 +671,20 @@ as->ams_verify_done = TRUE;
 */
 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)
   {
@@ -699,7 +708,7 @@ if (  !ams->bh.data
     pdkim_hexprint(sighash.data, sighash.len);
     debug_printf("ARC i=%d AMS Body hash did NOT match\n", as->instance);
     }
-  return US"body hash compare mismatch";
+  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);
@@ -707,7 +716,7 @@ 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 US"pubkey problem";
+  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);
@@ -719,6 +728,7 @@ arc_get_verify_hhash(ctx, ams, &hhash);
 if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
   {
   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";
   }
 
@@ -728,7 +738,7 @@ 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 US"ams sig verify fail";
+  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);
@@ -761,8 +771,9 @@ for(inst = 0; as; as = as->next)
      || arc_cv_match(as->hdr_as, US"fail")
      )
     {
-    DEBUG(D_acl) debug_printf("ARC i=%d fail"
-      " (cv, sequence or missing header)\n", as->instance);
+    arc_state_reason = string_sprintf("i=%d fail"
+      " (cv, sequence or missing header)", as->instance);
+    DEBUG(D_acl) debug_printf("ARC %s\n", arc_state_reason);
     ret = US"fail";
     }
 
@@ -775,6 +786,7 @@ for(inst = 0; as; as = as->next)
       ams_fail_found = TRUE;
     else
       arc_oldest_pass = inst;
+  arc_state_reason = NULL;
   }
 
 arc_received = ctx->arcset_chain_last;
@@ -785,7 +797,12 @@ if (ret)
 /* We can skip the latest-AMS validation, if we already did it. */
 
 as = ctx->arcset_chain_last;
-if (as->ams_verify_done ? !as->ams_verify_passed : !!arc_ams_verify(ctx, as))
+if (as->ams_verify_done && !as->ams_verify_passed)
+  {
+  arc_state_reason = as->ams_verify_done;
+  return US"fail";
+  }
+if (!!arc_ams_verify(ctx, as))
   return US"fail";
 
 return NULL;
@@ -822,7 +839,10 @@ DEBUG(D_acl) debug_printf("ARC: AS vfy i=%d\n", as->instance);
 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
@@ -835,6 +855,7 @@ if (!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";
   }
 
@@ -844,6 +865,8 @@ if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
            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");
@@ -874,7 +897,7 @@ for (as2 = ctx->arcset_chain;
   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, TRUE);
+                                       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);
@@ -931,6 +954,7 @@ if ((errstr = exim_dkim_verify(&vctx,
   {
   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";
   }
 
@@ -1306,10 +1330,8 @@ if (g->s[g->ptr - 1] == ':') g->ptr--;
 g = string_catn(g, US";\r\n\tb=;", 7);
 
 /* Include the pseudo-header in the accumulation */
-/*XXX should that be prepended rather than appended? */
-/*XXX also need to include at the verify stage */
 
-s = pdkim_relax_header_n(g->s + ams_off, g->ptr - ams_off, TRUE);
+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 */
@@ -1353,7 +1375,7 @@ while ((methodspec = string_nextinlist(&resinfo, &sep, NULL, 0)))
          (c = *s) && c != ';' && c != ' ' && c != '\r' && c != '\n'; ) s++;
     return string_copyn(methodspec, s - methodspec);
     }
-return NULL;
+return US"none";
 }
 
 
@@ -1394,7 +1416,7 @@ arcset = string_append(NULL, 10,
          ARC_HDR_AS,
          US" i=", string_sprintf("%d", instance),
          US"; cv=", status,
-         US"; a=rsa-sha256; c=relaxed; d=", identity,          /*XXX hardwired */
+         US"; a=rsa-sha256; d=", identity,                     /*XXX hardwired */
          US"; s=", selector,                                   /*XXX same as AMS */
          US";\r\n\t b=;");
 
@@ -1418,7 +1440,7 @@ for (as = Ustrcmp(status, US"fail") == 0
   h = as->hdr_ams->complete;
   hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
   h = as->hdr_as->complete;
-  hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, TRUE));
+  hdata = string_cat(hdata, pdkim_relax_header_n(h->text, h->slen, !!as->next));
   }
 
 /* Calculate the signature from the accumulation */
@@ -1690,7 +1712,10 @@ if (arc_state)
   if (arc_received_instance > 0)
     {
     g = string_append(g, 3, US" (i=",
-      string_sprintf("%d", arc_received_instance), US") header.s=");
+      string_sprintf("%d", arc_received_instance), US")");
+    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);