IDENT protocol support

sendmail supports the IDENT protocol as defined in RFC 1413. Note that the RFC states a client should wait at least 30 seconds for a response. The default Timeout.ident is 5 seconds as many sites have adopted the practice of dropping IDENT queries. This has lead to delays processing mail. Although this enhances identification of the author of an email message by doing a ``call back'' to the originating system to include the owner of a particular TCP/IP connection in the audit trail it is in no sense perfect; a determined forger can easily spoof the IDENT protocol. The following description is excerpted from RFC 1413:

6. Security Considerations
The information returned by this protocol is at most as trustworthy as the host providing it OR the organization operating the host. For example, a PC in an open lab has few if any controls on it to prevent a user from having this protocol return any identifier the user wants. Likewise, if the host has been compromised the information returned may be completely erroneous and misleading.

The Identification Protocol is not intended as an authorization or access control protocol. At best, it provides some additional auditing information with respect to TCP connections. At worst, it can provide misleading, incorrect, or maliciously incorrect information.

The use of the information returned by this protocol for other than auditing is strongly discouraged. Specifically, using Identification Protocol information to make access control decisions - either as the primary method (no other checks) or as an adjunct to other methods may result in a weakening of normal host security.

An Identification server may reveal information about users, entities, objects or processes which might normally be considered private. An Identification server provides service which is a rough analog of the CallerID services provided by some phone companies and many of the same privacy considerations and arguments that apply to the CallerID service apply to Identification. If you wouldn't run a "finger" server due to privacy considerations you may not want to run this protocol.