Improper Validation of Certificate Expiration

Description

When the expiration of a certificate is not taken into account, no trust has necessarily been conveyed through it. Therefore, the validity of the certificate cannot be verified and all benefit of the certificate is lost.

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 OpenSSL code ensures that there is a certificate and allows the use of expired certificates.

if (cert = SSL_get_peer(certificate(ssl)) {

  foo=SSL_get_verify_result(ssl);
  if ((X509_V_OK==foo) || (X509_V_ERR_CERT_HAS_EXPIRED==foo))


    //do stuff

If the call to SSL_get_verify_result() returns X509_V_ERR_CERT_HAS_EXPIRED, this means that the certificate has expired. As time goes on, there is an increasing chance for attackers to compromise the certificate.

See Also