[exim-cvs] ARC: fix crash in signing

Gitweb: https://git.exim.org/exim.git/commitdiff/7af11cd0ba4fab5f0a38a0505b85f8cd8a08c36b

Commit:     7af11cd0ba4fab5f0a38a0505b85f8cd8a08c36b
Parent:     6eea004b2f4a29db5ea9ea495574dd4fbb15a525
Author:     Jeremy Harris <jgh146exb@???>
AuthorDate: Wed Dec 4 14:01:18 2019 +0000
Committer:  Jeremy Harris <jgh146exb@???>
CommitDate: Wed Dec 4 14:01:18 2019 +0000

    ARC: fix crash in signing
---
 doc/doc-txt/ChangeLog |  4 ++++
 src/src/arc.c         | 23 ++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 8a0b75e..1e8a2d2 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -217,6 +217,10 @@ JH/46 FreeBSD: fix use of the sendfile() syscall.  The shim was not updating
       the file-offset (which the Linux syscall does, and exim expects); this
       resulted in an indefinite loop.

+JH/47 ARC: fix crash in signing, triggered when a configuration error failed
+      to do ARC verification.  The Authentication-Results: header line added
+      by the configuration then had no ARC item.
+

Exim version 4.92
-----------------
diff --git a/src/src/arc.c b/src/src/arc.c
index 8a94015..857e0c0 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -1419,10 +1419,10 @@ 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 */
@@ -1440,6 +1440,7 @@ 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 +1464,25 @@ 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 +1499,11 @@ 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;
 }