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# ThinkFinger

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Related articles

- Fingerprint-gui
- Fprint

ThinkFinger is a driver for the SGS Thomson Microelectronics fingerprint reader found in older IBM/Lenovo ThinkPads.

ThinkWiki has a list of various fingerprint readers found in ThinkPads. Newer models using different readers might not work with ThinkFinger.

## Installation

Install the thinkfingerAUR package.

## Configuration

The `uinput` module needs to be loaded.

### TF-Tool

Use `tf-tool` to test ThinkFinger. You will have to run this as root because a direct access to the USB devices is needed. Run `tf-tool --acquire` to generate a file at `/etc/pam_thinkfinger/test.bir` and `tf-tool --verify` to see if it identifies you correctly. `tf-tool --add-user <username>` acquires and stores your fingerprint in `/etc/pam_thinkfinger/<username>.bir`, which is needed for an authentication with PAM.

## PAM

See PAM.

### /etc/pam.d/login

Change the file `/etc/pam.d/login` to look like this if you want to use your fingerprint to authenticate yourself on logon:

    /etc/pam.d/login

    #%PAM-1.0
    auth		sufficient	pam_thinkfinger.so
    auth		required	pam_unix.so use_first_pass nullok_secure
    account		required	pam_unix.so
    password	required	pam_unix.so
    session		required	pam_unix.so

### /etc/pam.d/su

Change this file to confirm the `su` command with a finger-swipe:

    /etc/pam.d/su

    #%PAM-1.0
    auth            sufficient      pam_rootok.so
    auth		sufficient 	pam_thinkfinger.so
    auth		required	pam_unix.so nullok_secure try_first_pass
    account		required	pam_unix.so
    session		required	pam_unix.so

Tip: Do not forget to do a `tf-tool --add-user root` to use this feature.

### /etc/pam.d/sudo

Change this file to confirm the `sudo` command with a finger-swipe:

    /etc/pam.d/su

    #%PAM-1.0
    auth		sufficient 	pam_thinkfinger.so
    auth		required	pam_unix.so nullok_secure try_first_pass
    auth		required	pam_nologin.so

### /etc/pam.d/xscreensaver

The factual accuracy of this article or section is disputed.

Reason: Tampering with files in `/usr/bin/` is a bad idea since these changes will get overwritten on an update (Discuss in Talk:ThinkFinger)

XScreensaver is a bit tricky. First, configure PAM with a file `/etc/pam.d/xscreensaver` containing:

    /etc/pam.d/xscreensaver

     auth            sufficient      pam_thinkfinger.so
     auth            required        pam_unix_auth.so try_first_pass

This still will not work because Xscreensaver cannot read/write from `/dev/misc/uinput` and `/dev/bus/usb*`. A udev rule must be written to authorize a new group read/write access.

First, create a new group, let us say fingerprint:

    # groupadd fingerprint

Add the user you want to be able to unlock Xscreensaver with the fingerprint reader to the group:

    # gpasswd -a <user> fingerprint

Logout and login again for the changes to take effect.

Next, search for uinput and bus/usb in your udev rules directory:

    $ grep -in uinput /etc/udev/rules.d/*

    /etc/udev/rules.d/udev.rules:222:KERNEL=="uinput",  NAME="misc/%k", SYMLINK+="%k"
    /etc/udev/rules.d/udev.rules:263:KERNEL=="uinput", NAME="input/%k"

    $ grep -in "bus/usb" /etc/udev/rules.d/*

    /etc/udev/rules.d/udev.rules:318:SUBSYSTEM=="usb_device", ACTION=="add", PROGRAM="/bin/sh -c 'K=%k; K=$${K#usbdev};printf bus/usb/%%03i/%%03i $${K%%%%.*} $${K#*.}'", NAME="%c", MODE="0664"
    /etc/udev/rules.d/udev.rules:320:SUBSYSTEM=="usb", ACTION=="add", ENV{DEVTYPE}=="usb_device", NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}", MODE="0664"

Copy the lines you found with grep in the previous step to a new udev rules file:

    /etc/udev/rules.d/99fingerprint.rules

    KERNEL=="uinput",  NAME="misc/%k", SYMLINK+="%k", MODE="0660", GROUP="fingerprint"
    SUBSYSTEM=="usb_device", ACTION=="add", PROGRAM="/bin/sh -c 'K=%k; K=$${K#usbdev};printf bus/usb/%%03i/%%03i $${K%%%%.*} $${K#*.}'", NAME="%c", MODE="0664", GROUP="fingerprint"
    SUBSYSTEM=="usb", ACTION=="add", ENV{DEVTYPE}=="usb_device", NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}", MODE="0664", GROUP="fingerprint"

The difference between the rules in `/etc/udev/rules.d/99fingreprint.rules` and those in `/etc/udev/rules.d/udev.rules` should only be the addition of `MODE="0664", GROUP="fingerprint"` or `MODE="0660", GROUP="fingerprint"` at the end of the lines.

After adding the custom udev rules, you should give your user permissions to access their own fingerprint file:

    $ chown $USERNAME:root /etc/pam_thinkfinger/$USERNAME.bir
    $ chmod 400 /etc/pam_thinkfinger/$USERNAME.bir
    $ chmod o+x /etc/pam_thinkfinger

Note: The last command is opening up a directory for execution to everyone, beware of the security implications this might have.

As a last step, you need to remove the root setuid from `/usr/bin/xscreensaver`, otherwise Xscreensaver will not be able to unlock with the fingerprint reader:

    # chmod -s /usr/bin/xscreensaver

### /etc/pam.d/gdm

Edit `/etc/pam.d/gdm` and add the following line to the top:

    /etc/pam.d/gdm

    auth		sufficient 	pam_thinkfinger.so

Then modify `auth required pam_unix.so` to look like this:

    /etc/pam.d/gdm

    auth		required	pam_unix.so use_first_pass nullok_secure

### /etc/pam.d/xdm

Edit `/etc/pam.d/xdm` to look like this:

    /etc/pam.d/xdm

    #%PAM-1.0
    auth            sufficient      pam_thinkfinger.so
    auth            required        pam_unix.so use_first_pass nullok_secure
    auth            required        pam_nologin.so
    auth            required        pam_env.so
    account         required        pam_unix.so
    password        required        pam_unix.so
    session         required        pam_unix.so
    session         required        pam_limits.so

### /etc/pam.d/slim

Append the following to `/etc/pam.d/slim`:

    /etc/pam.d/slim

    #%PAM-1.0
    ...
    auth            sufficient      pam_thinkfinger.so
    auth            requisite       pam_nologin.so
    auth            required        pam_env.so
    auth            required        pam_unix.so
    account         required        pam_unix.so
    session         required        pam_limits.so
    session         required        pam_unix.so
    password        required        pam_unix.so

Now restart SLiM and you may use the fingerprinter to login.

## Alternative fingerprint reader software

Fprint is an alternative fingerprint reader software that works with some of the newer ThinkPad fingerprint readers.

## See also

- https://www.thinkwiki.org/wiki/Talk:How_to_enable_the_fingerprint_reader
- https://thinkfinger.sourceforge.net/
- https://bbs.archlinux.org/viewtopic.php?id=36134
- https://www.thinkwiki.org/wiki/How_to_enable_the_fingerprint_reader_with_ThinkFinger
- https://www.thinkwiki.org/index.php?title=Installing_Ubuntu_6.06_on_a_ThinkPad_T43#Fingerprint_Reader

Categories:

- Input devices
- Lenovo

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