pam_ssh(8) [freebsd man page]
PAM_SSH(8) BSD System Manager's Manual PAM_SSH(8) 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. 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: 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. nullok Normally, keys with no passphrase are ignored for authentication purposes. If this option is set, keys with no passphrase will be taken into consideration, allowing the user to log in with a blank password. 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: want_agent Start an agent even if no keys were decrypted during the authentication phase. FILES
$HOME/.ssh/identity SSH1 RSA key $HOME/.ssh/id_rsa SSH2 RSA key $HOME/.ssh/id_dsa SSH2 DSA key $HOME/.ssh/id_ecdsa SSH2 ECDSA key SEE ALSO
ssh-agent(1), pam.conf(5), pam(8) AUTHORS
The pam_ssh module was originally written by Andrew J. Korty <ajk@iu.edu>. The current implementation was developed for the FreeBSD Project by ThinkSec AS and NAI Labs, the Security Research Division of Network Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 (``CBOSS''), as part of the DARPA CHATS research program. This manual page was written by Mark R V Murray <markm@FreeBSD.org>. BSD
October 7, 2011 BSD
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PAM_SSH(8) BSD System Manager's Manual PAM_SSH(8) NAME
pam_ssh -- authentication and session management with SSH private keys DESCRIPTION
The SSH authentication service module for PAM, pam_ssh provides functionality for two PAM categories: authentication and session management. SSH Authentication Module The SSH authentication component verifies the identity of a user by prompting the user for a passphrase and verifying that it can decrypt at least one of the user's SSH login keys 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, then that password is used to decrypt the user's SSH login keys. If this fails, then the authentication module returns failure without prompting the user for a passphrase. try_first_pass Similar to the use_first_pass option, except that if the previously obtained password fails to decrypt any of the SSH login keys, then the user is prompted for an SSH passphrase. try_first_pass has no effect if pam_ssh is the first module on the stack, or if no previous modules obtained the user's password. allow_blank_passphrase Allow SSH keys with no passphrase. If neither use_first_pass nor try_first_pass is specified, pam_ssh will unconditionally ask for an SSH passphrase. In addition to the above authentication procedure, all standard SSH keys (identity, id_rsa, id_dsa) for which the obtained password matches will be decrypted. SSH Session Management Module The SSH session management component initiates sessions by starting an SSH agent, passing it any SSH login keys it decrypted during the authentication phase, and sets the environment variables accordingly. The SSH session management component terminates the session by killing 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. INFORMATION LEAKS
Be careful with the using the try_first_pass option when pam_ssh is the first authentication module because it will then leak information about existing users without login keys: such users will not be asked for a specific SSH passphrase, whereas non-existing users and existing users with login keys will be asked for a passphrase. FILES
$HOME/.ssh/identity $HOME/.ssh/id_rsa $HOME/.ssh/id_dsa OpenSSH DSA/RSA keys decrypted by pam_ssh. $HOME/.ssh/login-keys.d/ Location of (possibly symbolic links to) OpenSSH DSA/RSA keys used for authentication and decrypted by pam_ssh. /var/log/auth.log Usual log file for syslog(3) SEE ALSO
ssh-agent(1), syslog(3), pam.conf(5), pam(8). AUTHORS
Andrew J. Korty <ajk@iu.edu> wrote pam_ssh. Dag-Erling Smorgrav wrote the original OpenPAM support code. Mark R V Murray wrote the original version of this manual page. Jens Peter Secher introduced the login-key concept. BSD
November 26, 2001 BSD