commit f7d6acd4754b732084aea5f0a94ecdc6b4156185
author Gilles Peskine <Gilles.Peskine@arm.com> Fri Mar 01 18:06:08 2019 +0100
committer Gilles Peskine <Gilles.Peskine@arm.com> Wed Sep 11 15:46:44 2019 +0200
tree 974a4b9b1d4dbb7f708234f813b1b553b66411d2
parent 27d806fab41a11441d97017158fcb1356ef7e74f

mbedtls_asn1_get_int: allow leading zeros properly

Allow any number of leading zeros, not just based on sizeof(int).

library/asn1parse.c

diff --git a/library/asn1parse.c b/library/asn1parse.c
index 171c340..20e8177 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -149,11 +149,18 @@
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
         return( ret );
 
-    if( len == 0 || len > sizeof( int ) || ( **p & 0x80 ) != 0 )
+    if( len == 0 || ( **p & 0x80 ) != 0 )
+        return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+
+    while( len > 0 && **p == 0 )
+    {
+        ++( *p );
+        --len;
+    }
+    if( len > sizeof( int ) )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
 
     *val = 0;
-
     while( len-- > 0 )
     {
         *val = ( *val << 8 ) | **p;