Reference

libpam-ssh(8)

authentication and session management with SSH private keys

NAME

pam_ssh – authentication and session management with SSH private keys

SYNOPSIS

[service-name] module-type control-flag pam_ssh [options]

DESCRIPTION

The SSH authentication service module for PAM, pam_ssh provides functionality for two PAM categories: authentication and session management. In terms of the module-type parameter, they are the “auth” and “session” features. It also provides null functions for the remaining categories.

SSH Authentication Module

The SSH authentication component provides a function to verify the identity of a user (pam_sm_authenticate()), by prompting the user for a passphrase and verifying that it can decrypt the target user's SSH key using that passphrase.

The following options may be passed to the authentication module:

debug

syslog(3) debugging information at LOG_DEBUG level.

use_first_pass

If the authentication module is not the first in the stack, and a previous module obtained the user's password, that password is used to authenticate the user. If this fails, the authentication module returns failure without prompting the user for a password. This option has no effect if the authentication module is the first in the stack, or if no previous modules obtained the user's password.

try_first_pass

This option is similar to the use_first_pass option, except that if the previously obtained password fails, the user is prompted for another password.

keyfiles

Specify the comma-separated list of files in $HOME/.ssh to check for SSH keys. The default is “id_dsa,id_rsa,identity”.

SSH Session Management Module

The SSH session management component provides functions to initiate (pam_sm_open_session()) and terminate (pam_sm_close_session()) sessions. The pam_sm_open_session() function starts an SSH agent, passing it any private keys it decrypted during the authentication phase, and sets the environment variables the agent specifies. The pam_sm_close_session() function kills the previously started SSH agent by sending it a SIGTERM.

The following options may be passed to the session management module:

debug

syslog(3) debugging information at LOG_DEBUG level.

FILES

$HOME/.ssh/identity

SSH1/OpenSSH RSA key

$HOME/.ssh/id_dsa

OpenSSH DSA key

$HOME/.ssh2/id_rsa_*

SSH2 RSA keys

$HOME/.ssh2/id_dsa_*

SSH2 DSA keys

SEE ALSO

ssh-agent(1), syslog(3), pam.conf(5), pam(8)

AUTHORS

Andrew J. Korty ⟨[email protected]⟩ wrote pam_ssh. Dag-Erling Smorgrav wrote the original OpenPAM support code. Mark R V Murray wrote the original version of this manual page.