Software Engineering Institute

Client systems using Kerberos login passwords and integration with an LDAP server may inadvertently send the account password over the network to the LDAP server in clear text format. If the "authentication authority" attribute is not set on the LDAP server, the loginwindow application will try to authenticate the account to the configured LDAP server. After trying to authenticate the user with an encrypted password, the loginwindow application falls back to trying a Bind using an AuthenticationChoice of simple on the server. This fallback action causes the account password to be transmitted over the network in clear text.

This vulnerability is exposed strictly in an environment where clients are configured to use Kerberos for authentication and LDAP for lookup of other user records. This configuration is not the default for MacOS X, but is commonly recommended and used for environments with a large userbase.

An attacker who has the ability to sniff packets as they cross the network or has access to logs on the LDAP servers can acquire the plaintext passwords of users authenticating to the Kerberos system. The attacker could subsequently use these passwords to impersonate the corresponding users and gain the privileges of that principle in the Kerberos realm.

Patches and workarounds are available for this vulnerability. Please see the vendors section of this document for more details.

Sites may also wish to enable Secure Sockets Layer (SSL) connectivity to LDAP servers in order to prevent other sensitive information that may be exchanged during the LDAP session from being passed over the network in cleartext.