pam_ssh (8) Linux Manual Page
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, 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 (Fn 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_DEBUGlevel. 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_passoption, 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”
nullok- Allow empty passphrases.
SSH Session Management Module
The SSH session management component provides functions to initiate (Fn pam_sm_open_session ) and terminate (Fn pam_sm_close_session ) sessions. The Fn 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 Fn 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_DEBUGlevel.
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
/var/run/pam_ssh/<user>*- ssh-agent environment information. The files are owned by the superuser but readable by the users. The location is Fedora specific, in the original package these files are in $HOME/.ssh/agent-*
See Also
ssh-agent1, syslog(3), pam.conf5, pam(8)
Authors
An -nosplit An Andrew J. Korty Aq ajk [at] iu.edu wrote . An Dag-Erling Smorgrav wrote the original OpenPAM support code. An Mark R V Murray wrote the original version of this manual page.