Reject long-form tags in CBS_peek_asn1_tag.

Currently, CBS only handles short-form tags.

ok miod@ jsing@

2 files changed, 16 insertions, 2 deletions

diff --git a/src/lib/libssl/bs_cbs.c b/src/lib/libssl/bs_cbs.c
index 4c1bfa3288..c37f81dd60 100644
--- a/src/lib/libssl/bs_cbs.c
+++ b/src/lib/libssl/bs_cbs.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bs_cbs.c,v 1.7 2015/04/29 02:11:09 doug Exp $ */
+/*      $OpenBSD: bs_cbs.c,v 1.8 2015/06/13 08:46:00 doug Exp $ */
 /*
  * Copyright (c) 2014, Google Inc.
  *
@@ -314,6 +314,13 @@ CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value)
         if (CBS_len(cbs) < 1)
                 return 0;
 
+        /*
+         * Tag number 31 indicates the start of a long form number.
+         * This is valid in ASN.1, but CBS only supports short form.
+         */
+        if ((tag_value & 0x1f) == 0x1f)
+                return 0;
+
         return CBS_data(cbs)[0] == tag_value;
 }
 
diff --git a/src/lib/libssl/src/ssl/bs_cbs.c b/src/lib/libssl/src/ssl/bs_cbs.c
index 4c1bfa3288..c37f81dd60 100644
--- a/src/lib/libssl/src/ssl/bs_cbs.c
+++ b/src/lib/libssl/src/ssl/bs_cbs.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bs_cbs.c,v 1.7 2015/04/29 02:11:09 doug Exp $ */
+/*      $OpenBSD: bs_cbs.c,v 1.8 2015/06/13 08:46:00 doug Exp $ */
 /*
  * Copyright (c) 2014, Google Inc.
  *
@@ -314,6 +314,13 @@ CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value)
         if (CBS_len(cbs) < 1)
                 return 0;
 
+        /*
+         * Tag number 31 indicates the start of a long form number.
+         * This is valid in ASN.1, but CBS only supports short form.
+         */
+        if ((tag_value & 0x1f) == 0x1f)
+                return 0;
+
         return CBS_data(cbs)[0] == tag_value;
 }