commit 758f490c90eedcea91a8859eef035640c9a30f5b
author Manuel Pégourié-Gonnard <mpg2@elzevir.fr> Wed Oct 21 12:07:47 2015 +0200
committer Manuel Pégourié-Gonnard <mpg2@elzevir.fr> Tue Oct 27 11:47:37 2015 +0100
tree 6f7afa8a983faa415a3b3fd4094c0b0c2d13306d
parent 215a14bf29c5eac125ab986adefa37bb4fbc5284

Fix potential buffer overflow in asn1write

Ref: IOTSSL-519

backport of 22c3b7b

library/asn1write.c

diff --git a/library/asn1write.c b/library/asn1write.c
index df9442e..87e130e 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -88,7 +88,7 @@
 {
     size_t len = 0;
 
-    if( *p - start < (int) size )
+    if( *p < start || (size_t)( *p - start ) < size )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
 
     len = size;
@@ -108,7 +108,7 @@
     //
     len = mpi_size( X );
 
-    if( *p - start < (int) len )
+    if( *p < start || (size_t)( *p - start ) < len )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
 
     (*p) -= len;
@@ -271,7 +271,7 @@
 
     // Calculate byte length
     //
-    if( *p - start < (int) size + 1 )
+    if( *p < start || (size_t)( *p - start ) < size + 1 )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
 
     len = size + 1;