AuthOptions

Tune authentication parameters

V8.10 and later

AuthOptions provides a list of general tuning parameters that affect authentication. It is declared like this:

O AuthOptions=string               configuration file (V8.10 and later) 
-OAuthOptions=string               configuration file (V8.10 and later) 
define(`confAUTH_OPTIONS', `string')   mc configuration (V8.10 and later)

The argument, of type string, is a list of characters selected from those shown in Table 24-13, where each character sets a particular tuning parameter. If more than one character is listed, each character must be separated from the next by either a comma or a space.

Table 24-13. AuthOptions character settings
Character	Meaning
`A`	Use the AUTH= parameter from the MAIL FROM: command only when authentication succeeds. This character can be specified as a workaround for broken MTAs that do not correctly implement RFC2554. (Client only)
`a`	Provide protection from active (nondictionary) attacks during the authentication exchange. (Server only)
`c`	Allow only selected mechanisms (those that can pass client credentials) to be used with client credentials. (Server only)
`d`	Don't permit use of mechanisms that are susceptible to passive dictionary attacks. (Server only)
`f`	Require forward-secrecy between sessions (where breaking one won't help break the next). (Server only)
`p`	Don't permit mechanisms to be used if they are susceptible to simple passive attack (that is, disallow use of PLAIN and LOGIN), unless a security layer is already active (as, for example, provided by STARTTLS). (Server only)
`T`	The opposite of A (pre-V8.12 only, client only)
`y`	Don't permit the use of any mechanism that allows anonymous login. (Server only)

If string is missing, sendmail will issue the following error and skip this option declaration:

Warning: Option: AuthOptions requires parameter(s)

If any letter is specified other than those listed in the table—for example, H—sendmail issues the following warning and skips this option declaration:

Warning: Option: AuthOptions unknown parameter 'H'

Note that macros cannot be used to define the list of characters.

The AuthOptions option is available only if sendmail is compiled with SASL (SASL) defined as true.

The AuthOptions option is not safe. If specified from the command line, it can cause sendmail to relinquish its special privileges.

Table 24-13. AuthOptions character settings