RUSTSEC-2023-0006

X.400 address type confusion in X.509 `GeneralName`

There is a type confusion vulnerability relating to X.400 address processing inside an X.509 `GeneralName`. X.400 addresses were parsed as an `ASN1_STRING` but the public structure definition for `GENERAL_NAME` incorrectly specified the type of the `x400Address` field as `ASN1_TYPE`. This field is subsequently interpreted by the OpenSSL function `GENERAL_NAME_cmp` as an `ASN1_TYPE` rather than an `ASN1_STRING`. When CRL checking is enabled (i.e. the application sets the `X509_V_FLAG_CRL_CHECK` flag), this vulnerability may allow an attacker to pass arbitrary pointers to a `memcmp` call, enabling them to read memory contents or enact a denial of service. In most cases, the attack requires the attacker to provide both the certificate chain and CRL, neither of which need to have a valid signature. If the attacker only controls one of these inputs, the other input must already contain an X.400 address as a CRL distribution point, which is uncommon. As such, this vulnerability is most likely to only affect applications which have implemented their own functionality for retrieving CRLs over a network.