Use of a Key Past its Expiration Date

Description

While the expiration of keys does not necessarily ensure that they are compromised, it is a significant concern that keys which remain in use for prolonged periods of time have a decreasing probability of integrity. For this reason, it is important to replace keys within a period of time proportional to their strength.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code attempts to verify that a certificate is valid.

if (cert = SSL_get_peer_certificate(ssl)) {

  foo=SSL_get_verify_result(ssl);
  if ((X509_V_OK==foo) || (X509_V_ERRCERT_NOT_YET_VALID==foo))


    //do stuff




}

The code checks if the certificate is not yet valid, but it fails to check if a certificate is past its expiration date, thus treating expired certificates as valid.

See Also