[exim-cvs] ARC: harden versus badly-formatted AMS line

Gitweb: https://git.exim.org/exim.git/commitdiff/6f47da8d2d526953e8e6403f448d1598c9140df1

Commit:     6f47da8d2d526953e8e6403f448d1598c9140df1
Parent:     cc05007f1dd71890b2b34b7aec5ed12dc5942c73
Author:     Jeremy Harris <jgh146exb@???>
AuthorDate: Thu Oct 17 14:09:18 2019 +0100
Committer:  Jeremy Harris <jgh146exb@???>
CommitDate: Thu Oct 17 14:17:59 2019 +0100

    ARC: harden versus badly-formatted AMS line
---
 src/src/arc.c         | 26 ++++++++++++++++++++------
 src/src/pdkim/pdkim.c |  2 ++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/src/arc.c b/src/src/arc.c
index 773b34c..b7fcb11 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -544,7 +544,8 @@ 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");
@@ -639,7 +640,7 @@ 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 */
@@ -745,6 +746,11 @@ 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 +877,8 @@ 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");
@@ -966,8 +973,6 @@ if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
   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)))
@@ -1738,7 +1743,13 @@ 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 */
@@ -1757,6 +1768,9 @@ if (!(b = arc_ams_setup_vfy_bodyhash(&al)))
should have been created here. */

return NULL;
+
+badline:
+ return US"line parsing error";
}


diff --git a/src/src/pdkim/pdkim.c b/src/src/pdkim/pdkim.c
index 9fa38b3..7fcfbc7 100644
--- a/src/src/pdkim/pdkim.c
+++ b/src/src/pdkim/pdkim.c
@@ -2029,6 +2029,8 @@ pdkim_set_bodyhash(pdkim_ctx * ctx, int hashtype, int canon_method,
{
pdkim_bodyhash * b;

+if (hashtype == -1 || canon_method == -1) return NULL;
+
 for (b = ctx->bodyhash; b; b = b->next)
   if (  hashtype == b->hashtype
      && canon_method == b->canon_method