commit 80164741e181a87ae18fa91a07f7201931b4d097
author Andres AG <andres.amayagarcia@arm.com> Thu Mar 09 16:16:11 2017 +0000
committer Simon Butcher <simon.butcher@arm.com> Thu Jul 27 21:44:34 2017 +0100
tree 4f327f23598154cfa9bca51f3aa620db0c6c6db0
parent 7d6ec7bacc9f03d671af9155f484296f675470f8

Fix potential integer overflow parsing DER CRT

This patch prevents a potential signed integer overflow during the
certificate version verification checks.

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index 58ee285..567e988 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -228,6 +228,9 @@
      digits. Found and fixed by Guido Vranken.
    * Fix unlisted DES configuration dependency in some pkparse test cases. Found
      by inestlerode. #555
+   * Fix a potential integer overflow in the version verification for DER
+     encoded X509 certificates. The overflow would enable maliciously
+     constructed certificates to bypass the certificate verification check.
 
 = mbed TLS 2.4.1 branch released 2016-12-13
 

library/x509_crt.c

diff --git a/library/x509_crt.c b/library/x509_crt.c
index 5ec8551..c6209fb 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -748,14 +748,14 @@
         return( ret );
     }
 
-    crt->version++;
-
-    if( crt->version > 3 )
+    if( crt->version < 0 || crt->version > 2 )
     {
         mbedtls_x509_crt_free( crt );
         return( MBEDTLS_ERR_X509_UNKNOWN_VERSION );
     }
 
+    crt->version++;
+
     if( ( ret = mbedtls_x509_get_sig_alg( &crt->sig_oid, &sig_params1,
                                   &crt->sig_md, &crt->sig_pk,
                                   &crt->sig_opts ) ) != 0 )