pam_ssh man page

pam_ssh — authentication and session management with SSH private keys


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


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:


syslog(3) debugging information at LOG_DEBUG level.


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.


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.


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


Allow empty passphrases.

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:


syslog(3) debugging information at LOG_DEBUG level.



SSH1/OpenSSH RSA key


OpenSSH DSA key


SSH2 RSA keys


SSH2 DSA keys


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


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


November 26, 2001