Fix embarrassing X.509 bug introduced in 9533765b

ChangeLog

@@ -8,6 +8,10 @@ Changes
 Security
    * Avoid potential timing leak in ecdsa_sign() by blinding modular division.
      (Found by Watson Ladd.)
+   * The notAfter date of some certificates was no longer checked since 1.3.5.
+     This affects certificates in the user-supplied chain except the top
+     certificate. If the user-supplied chain contains only one certificates,
+     it is not affected (ie, its notAfter date is properly checked).
 
 Bugfix
    * The length of various ClientKeyExchange messages was not properly checked.

library/x509_crt.c

@@ -1647,6 +1647,9 @@ static int x509_crt_verify_child(
     x509_crt *grandparent;
     const md_info_t *md_info;
 
+    if( x509_time_expired( &child->valid_to ) )
+        *flags |= BADCERT_EXPIRED;
+
     if( x509_time_future( &child->valid_from ) )
         *flags |= BADCERT_FUTURE;