Provided by: libpam-mount_0.12.0-1ubuntu1_i386
pam_mount - A PAM module that can mount volumes for a user session
This module is aimed at environments with SMB (Samba or Windows NT) or
NCP (Netware or Mars-NWE) servers that Unix users wish to access
transparently. It facilitates access to private volumes of these types
well. The module also supports mounting home directories using
loopback encrypted filesystems. The module was originally written for
use on the GNU/Linux operating system but has since been modified to
work on several flavors of BSD.
o Every user can access his own volumes
o The user needs to type the password just once (at login)
o The mounting process is transparent to the users
o There is no need to keep the login passwords in any additional file
o The volumes are unmounted upon logout, so it saves system resources,
avoiding the need of listing every every possibly useful remote
volume in /etc/fstab or in an automount/supermount config file. This
is also necessary for securing encrypted filesystems.
Pam_mount "understands" SMB, NCP, and any type of filesystem that can
be mounted using the standard mount command. If someone has a
particular need for a different filesystem, feel free to ask me to
include it and send me patches.
If you intend to use pam_mount to protect volumes on your computer
using an encrypted filesystem system, please know that there are many
other issues you need to consider in order to protect your data. For
example, you probably want to disable or encrypt your swap partition
cryptoswap can help you do this). Don’t assume a system is secure
without carefully considering potential threats.
The primary configuration file for the pam_mount module is
pam_mount.conf. On most platforms this file is read from
/etc/security/pam_mount.conf. On OpenBSD pam_mount reads its
configuration file from /etc/pam_mount.conf. Pam_mount.conf contains
many comments documenting its use.
In addition, you must include two entries in the system’s applicable
/etc/pam.d/SERVICE config files, as the following example shows:
auth required pam_securetty.so
auth required pam_pwdb.so shadow nullok
auth required pam_nologin.so
+++ auth optional pam_mount.so use_first_pass
account required pam_pwdb.so
password required pam_cracklib.so
password required pam_pwdb.so shadow nullok use_authtok
session required pam_pwdb.so
session optional pam_console.so
+++ session optional pam_mount.so
If you use pam_ldap, pam_winbind, or any other authentication services
that make use of PAM’s sufficient keyword then model your configuration
on the following:
account sufficient pam_ldap.so
auth required pam_mount.so
auth sufficient pam_ldap.so use_first_pass
auth required pam_unix.so use_first_pass
session optional pam_mount.so
This allows the following:
1. Pam_mount will prompt for a password and export it to the PAM
2. Pam_ldap will use the password from the PAM system to try and
authenticate the user. If this succedes, the user will be
authenticated. If it fails, pam_unix will try to authenticate.
3. Pam_unix will try to authenticate the user if pam_ldap fails. If
pam_unix fails, then the authentication will be refused.
If your volume has a different password than your system account, then
encrypt the password to the volume you wish mounted using your system
password as the key and store it somewhere on your system’s local
filesystem. Pam_mount supports transparently decrypting this
filesystem key, as long as the cipher used is supported by openssl.
sk system key, the key or password used to log into the system
fsk filesystem key, the key that allows you to use the filesystem
you wish pam_mount to mount for you
E and D
an openssl supported synchronous encryption/decryption algorithm
efsk encrypted filesystem key, efsk = E_sk (fsk), stored somewhere on
the local filesystem (ie: /home/user.key)
Pam_mount will read efsk from the local filesystem, perform fsk = D_sk
(efsk) and use fsk to mount the filesystem. If you change your system
password, simply regenerate efsk using efsk = E_sk (fsk). If you want
to mount this volume by hand, use something like openssl enc -d
-aes-256-ecb -in /home/user.key | mount -p0 /home/user. More
information about this technique is included in pam_mount.conf.
A script named mkehd is provided with pam_mount to help create
encrypted home directories. If you have an entry for a user using
encrypted home directories in pam_mount.conf, mkehd will create
necessary filesystem images and possibly encrypted filesystem keys.
Individual users may define additional volumes to mount if allowed by
pam_mount.conf (usually ~/.pam_mount.conf). The volume keyword is the
only valid keyword in these per-user configuration files. If the
luserconf parameter is set in pam_mount.conf, allowing user-defined
volume, then users may mount and unmount any volume they own at any
mount point they own. On some filesystem configurations this may be a
security flaw so user-defined volumes are not allowed by the example
pam_mount.conf distributed with pam_mount.
In general, you will leave all the first (general) parameters as
provided by default. You only have to provide the user/volume list in
the end of the file, following the examples.
To ensure that your system and, possibly, the remote server are all
properly configured, you should try to mount all or some of the volumes
by hand, using the same commands and mount points provided in
pam_mount.conf. This will save you a lot of grief, since it is more
difficult to debug the mounting process via pam_mount.
If you can mount the volumes by hand but it is not happening via
pam_mount, you may want to enable the "debug" option in pam_mount.conf
to see what is happening.
Verify if the user owns the mount point and has sufficient permissions
over that. pam_mount will verify this and will refuse to mount the
remote volume if the user does not own that directory.
If pam_mount is having trouble unmounting volumes upon logging out,
enable the debug variable and check the lsof variable in
pam_mount.conf. This causes pam_mount to run lsof upon logging out and
write lsof’s output to the system’s logs.
W. Michael Petullo <email@example.com>