PAM_SSH(8) | System Manager's Manual | PAM_SSH(8) |
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 provides
functionality for two PAM categories: authentication and session management.
In terms of the module-type parameter, they are the
“auth
” and
“session
” features.
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
try_first_pass
use_first_pass
option, except that if the previously obtained password fails, the user is
prompted for another password.nullok
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
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>.
The pam_ssh
module implements what is
fundamentally a password authentication scheme. Care should be taken to only
use this module over a secure session (secure TTY, encrypted session, etc.),
otherwise the user's SSH passphrase could be compromised.
Additional consideration should be given to the use of
pam_ssh
. Users often assume that file permissions
are sufficient to protect their SSH keys, and thus use weak or no
passphrases. Since the system administrator has no effective means of
enforcing SSH passphrase quality, this has the potential to expose the
system to security risks.
December 16, 2011 | NetBSD 10.99 |