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# pam_mount

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- dm-crypt/Mounting at login
- PAM

pam_mount can be used to automatically mount an encrypted home partition (encrypted with, for example, LUKS or ECryptfs) on user log in. It will mount your `/home` (or whatever mount point you like) when you log in using your login manager or when logging in on console. The encrypted drive's passphrase should be the same as your linux user's password, so you do not have to type in two different passphrases to login.

Note: pam_mount can also unmount your partitions when you close your last session but this does not work out of the box due to the use of `pam_systemd.so` in the pam stack. See systemd issue 8598 and Talk:Pam mount#automatic unmounting and systemd.

## Configuration

Install the pam_mount package.

### Global (system) configuration

The module is configured in `/etc/security/pam_mount.conf.xml`, see pam_mount.conf(5) for details. Edit the file as follows:

    /etc/security/pam_mount.conf.xml

      <!-- Generic encrypted partition example -->
      <volume user="USERNAME" fstype="auto" path="/dev/sdaX" mountpoint="/home" options="fsck,noatime" />

      <!-- Example using CIFS -->
      <volume
          fstype="cifs"
          server="server.example.com"
          path="share_name"
          mountpoint="~/mnt/share_name"
          uid="10000-19999"
          options="sec=krb5i,vers=3.0,cruid=%(USERUID)"
      />
      <mkmountpoint enable="1" remove="true" />

    </pam_mount>

Notes:

- Insert 2 new lines at the end of the file, but before the last closing tag, `</pam_mount>`.
- `USERNAME` should be replaced with your user name.
- `/dev/sdaX` should be replaced with the corresponding device or container file.
- `fstype="auto"` can be changed to any `type` that is present in `/usr/bin/mount.type`. `"auto"` should work fine in most cases. Use `fstype="crypt"` so that the loop device gets closed at logout for volumes needing it.
- Add mount options, if needed. Note that `mount.cifs` does not read `smb.conf` and so all options must be specified. In the example, `uid` matches the local `smb.conf` parameter idmap config ... : range = so that pam_mount is not called for a Unix only user. Kerberos is indicated by krb5, SMB3.0 is specified because the other end may not support SMB1 which is the default. Signing is enabled with the i on the end of krb5i. See mount.cifs(8) for more details.

### Local (per-user) configuration

pam_mount also supports allowing users to define their own mounts on login in files inside their home directories. Please consider the potential security implications of this change. To enable it, make sure the following line is present and active in `/etc/security/pam_mount.conf.xml`:

    /etc/security/pam_mount.conf.xml

    <luserconf name=".pam_mount.conf.xml" />

It will have the effect of allowing each user to set their mounts in `~/.pam_mount.conf.xml`. The per-user config files only support `<volume>` keywords, e.g.:

    ~/.pam_mount.conf.xml

    <?xml version="1.0" encoding="utf-8" ?>
    <!DOCTYPE pam_mount SYSTEM "pam_mount.conf.xml.dtd">

    <pam_mount>
        <volume user="alex" fstype="tmpfs" path="tmpfs" mountpoint="~/test" options="nodev,nosuid" />
    </pam_mount>

There are also some restrictions with regards to the mount options that you can and cannot select and some of them are mandatory (`nosuid`, `nodev`, `size`, `uid`, these can be lifted by editing `/etc/security/pam_mount.conf.xml`). Bind mounts appear to be unsupported. Ownership checks are also performed on the mountpoints.

### LUKS volumes

LUKS encrypted volumes can be configured simply as follows:

    /etc/security/pam_mount.conf.xml

    <volume user="username" fstype="crypt" path="/dev/disk/by-partuuid/partition_uuid" mountpoint="~" options="crypto_name=volume_name,allow_discard,fstype=btrfs,compress=zstd" />

The volume is unlocked and mounted with mount.crypt, see mount.crypt(8) § Mount options for details about the options.

### Veracrypt volumes

pam_mount does not support Veracrypt volumes natively, but there is a workaround:

    /etc/security/pam_mount.conf.xml

    <volume user="username" fstype="crypt" path="/dev/disk/by-partuuid/partition_uuid" mountpoint="vcrypt"/>
    <volume user="username" fstype="auto" path="/dev/mapper/vcrypt" mountpoint="/media/mountpoint"/>

    <cryptmount>cryptsetup --veracrypt open --type tcrypt %(VOLUME) %(MNTPT)</cryptmount>
    <cryptumount>cryptsetup close %(MNTPT)</cryptumount>

If you also have LUKS volumes, you can use a different fstype for Veracrypt volume instead of `crypt` with `cryptmount/cryptumount`, for example `ncpfs` with `ncpmount/ncpumount`. Just make sure you do not use NCP filesystem.

### F2FS encryption

There is a trick to make pam_mount add a F2FS decryption key to your session keyring. The salt you chose when encrypting directory(es) with f2fscrypt needs to match the one in `/etc/security/pam_mount.conf.xml` (0x1111 in below example) and passphrase needs to match the user's login password. This example assumes you are not mounting FUSE filesystems with pam_mount. If you do, choose a different `<*mount>` tag pairs instead of `<fusemount>` and `<fuseumount>`, like `<ncpmount>/<ncpumount>`.

    /etc/security/pam_mount.conf.xml

    <fusemount>f2fscrypt add_key -S 0x1111</fusemount>
    <fuseumount>f2fscrypt new_session</fuseumount>
    <volume noroot="1" ssh="0" fstype="fuse" path="/tmp/not-a-real-path-0" mountpoint="/tmp/not-a-real-path-1"/>

`<volume>` does not do anything except trigger the commands in `<fusemount>` and `<fuseumount>`. After login you can verify that your session keyring has a F2FS decryption key:

    $ keyctl show

    Session Keyring
     910133222 --alswrv   1000   100  keyring: _ses
     301049775 --alswrv   1000 65534   \_ keyring: _uid.1000
     013481035 --alsw-v   1000   100   \_ logon: f2fs:2e64cf4a5bafcd7

## Login manager configuration

In general, you have to edit configuration files in `/etc/pam.d` so that pam_mount will be called on login. The correct order of entries in each file is important. It is necessary to edit `/etc/pam.d/system-login` as shown below. If you use a display manager make sure its file includes `system-login`. Example configuration files follow, with the added lines in bold.

The `pam_succeed_if` line before `pam_mount` in session skips `pam_mount` (`success=n` means skip the next `n` lines) if the `systemd-user` service is running through the PAM stack (i.e. `/etc/pam.d/systemd-user`). This avoids double mount attempts and errors relating to dropped privileges when the `systemd --user` instance is starting up. See [1] and [2] for details.

    /etc/pam.d/system-login

    #%PAM-1.0

    auth       required   pam_shells.so
    auth       requisite  pam_nologin.so
    auth       optional   pam_mount.so
    auth       include    system-auth

    account    required   pam_access.so
    account    required   pam_nologin.so
    account    include    system-auth

    password   optional   pam_mount.so
    password   include    system-auth

    session    optional   pam_loginuid.so
    session    optional   pam_keyinit.so       force revoke
    session [success=1 default=ignore]  pam_succeed_if.so  service = systemd-user quiet
    session    optional   pam_mount.so
    session    include    system-auth
    session    optional   pam_motd.so          motd=/etc/motd
    session    optional   pam_mail.so          dir=/var/spool/mail standard quiet
    -session   optional   pam_systemd.so
    session    required   pam_env.so

Category:

- Authentication