Fix potential integer overflow parsing DER CRL
This patch prevents a potential signed integer overflow during the
CRL version verification checks.
diff --git a/ChangeLog b/ChangeLog
index 081bcf1..e50604d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,10 @@
Found by redplait #590
* Add MPI_CHK to check for error value of mpi_fill_random.
Backported from a report and fix suggestion by guidovranken in #740
+ * Fix a potential integer overflow in the version verification for DER
+ encoded X509 CRLs. The overflow would enable maliciously constructed CRLs
+ to bypass the version verification check. Found by Peng Li/Yueh-Hsun Lin,
+ KNOX Security, Samsung Research America
= mbed TLS 1.3.20 branch released 2017-06-21
diff --git a/library/x509_crl.c b/library/x509_crl.c
index b2b0bed..96120a9 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -353,14 +353,14 @@
return( ret );
}
- crl->version++;
-
- if( crl->version > 2 )
+ if( crl->version < 0 || crl->version > 1 )
{
x509_crl_free( crl );
return( POLARSSL_ERR_X509_UNKNOWN_VERSION );
}
+ crl->version++;
+
if( ( ret = x509_get_sig_alg( &crl->sig_oid1, &sig_params1,
&crl->sig_md, &crl->sig_pk,
&crl->sig_opts ) ) != 0 )