pam_duo provides secondary authentication (typically after successful password-based authentication) through the Duo authentication service.
PAM module configuration options supported:
Specify an alternate configuration file to load. Default is
Debug mode; send log messages to stderr instead of syslog.
The INI-format configuration file must have a “
duo” section with the following options:
Duo API host (required).
Duo integration key (required).
Duo secret key (required).
If specified, Duo authentication is required only for users whose primary group or supplementary group list matches one of the space-separated pattern-lists (see Patterns below).
On service or configuration errors that prevent Duo authentication, fail “
safe” (allow access) or “
secure” (deny access). Default is “
Send command to be approved via Duo Push authentication. Default is “
Use the specified HTTP proxy, same format as the HTTP_PROXY environment variable.
Automatically send a login request to the first factor (usually push), instead of prompting the user. Default is "no".
Set the maxiumum number of prompts pam_duo will show before denying access. Default is 3.
If unable to detect the authorizing user's IP address, fallback on the server's IP. Default is "no".
Instead of using the unix username, send Duo the contents of the GECOS field from /etc/passwd. Default is "no".
An example configuration file:
[duo] host = api-deadbeef.duosecurity.com ikey = SI9F...53RI skey = 4MjR...Q2NmRiM2Q1Y pushinfo = yes autopush = yes
Other authentication restrictions may be implemented using pam_listfile(8), pam_access(8), etc.
A pattern consists of zero or more non-whitespace characters, ‘*’ (a wildcard that matches zero or more characters), or ‘?’ (a wildcard that matches exactly one character).
A pattern-list is a comma-separated list of patterns. Patterns within pattern-lists may be negated by preceding them with an exclamation mark (‘!’). For example, to specify Duo authentication for all users (except those that are also admins), and for guests:
groups = users,!wheel,!*admin guests
Default configuration file path
pam_duo was written by Duo Security ⟨firstname.lastname@example.org⟩
When used with OpenSSH's sshd(8), only PAM-based authentication can be protected with this module; pubkey authentication bypasses PAM entirely. OpenSSH's PAM integration also does not honor an interactive pam_conv(3) conversation, prohibiting real-time Duo status messages (such as during voice callback).