chkpw

chkpw is a program that checks the validity of a users password on a UNIX/PAM-based system.

Currently chkpw is only tested on Linux, but it should work on a AIX, DragonFly BSD, FreeBSD, HP-UX, Linux, macOS, NetBSD and Solaris operating system too.

The idea

I needed a program to verify passwords of users on Linux/UNIX systems using PAM that just returns 0 on success and 1 on error.

Requirements

You need the PAM development package installed. On Alpine it is named linux-pam-dev, on Debian based systems it is libpam0g-dev.

Building chkpw

git clone https://git.xw3.org/hanez/chkpw.git
cd chkpw
make

The code only supports verifying passwords for user id 1000 by default. Look at the file chkpw.h for some compile time options!

Custom build example

Set MAX_UID and MIN_UID at compile time:

gcc -Wall -DMAX_UID=1000 -DMIN_UID=1000 -o chkpw chkpw.c -lpam -lpam_misc

Installation

WARNING: Install this software with care. chkpw could easily be used for bruteforcing passwords from local users!

sudo make install

chkpw is installed to /usr/bin/.

chkpw.h is installed to /usr/include/ for use in other applications.

Uninstall

sudo make uninstall

Usage

chkpw -h
Usage: chkpw [-u <username>] [-p <password>] [-v] [-V] [-h]

Options:
  -u <username>  Set username.
  -p <password>  Set password.
  -v             Enable verbose mode.
  -V             Print program version.
  -h             Show this help.

You can also use chkpw even without installing by just running the following command:

./chkpw

Return codes

chkpw returns 0 on success, 1 otherwise.

Examples

Interactive mode asking for a username and a password

chkpw

Interactive mode only asking for a password

chkpw -u hanez

None interactive mode with username and password provided as arguments to chkpw

chkpw -u hanez -p password

Request the result from the above commands

echo $?

License

chkpw is licensed under the Apache License, Version 2.0.

See LICENSE for details.

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