Intro ===== This is just a simple PAM module and test code for it. There really isn't much to it, but it does make a good example of how to get started with a PAM module. To build, either use the build scripts or use these commands: **Build the PAM module** `gcc -fPIC -fno-stack-protector -c src/mypam.c` `sudo ld -x --shared -o /lib/security/mypam.so mypam.o` The first command builds the object file in the current directory and the second links it with PAM. Since it's a shared library, PAM can use it on the fly without having to restart. **Build Test** `g++ -o pam_test src/test.c -lpam -lpam_misc` OR `gcc -o pam_test src/test.c -lpam -lpam_misc` The test program is valid C, so it could be compiled using gcc or g++. I like g++ better because I'll probably want to extend it and I like C++ better. Simple Usage ------------ The build scripts will take care of putting your module where it needs to be, `/lib/security`, so the next thing to do is edit config files. The config files are located in `/etc/pam.d/` and the one I edited was `/etc/pam.d/common-auth`. The test application tests auth and account functionality (although account isn't very interesting). At the top of the pam file (or anywhere), put these lines: auth sufficient mypam.so account sufficient mypam.so I think the account part should technically go in `/etc/pam.d/common-account`, but I put mine in the same place so I'd remember to take them out later. To run the test program, just do: `pam_test backdoor` and you should get some messages saying that you're authenticated! Maybe this is how Sam Flynn 'hacked' his father's computer in TRON Legacy =D. Resources ========= I found these resources especially helpful: O'Reilly Guides: ---------------- These guides give brief overviews about PAM and how to write modules. This is useful if you already have a little knowledge. * [Writing PAM Modules, Part One](http://linuxdevcenter.com/pub/a/linux/2002/05/02/pam_modules.html) * [Writing PAM Modules, Part Two](http://linuxdevcenter.com/pub/a/linux/2002/05/23/pam_modules.html) * [Writing PAM Modules, Part Three](http://linuxdevcenter.com/pub/a/linux/2002/05/30/pam_modules.html) Others ------ Good example for simple authentication. I adapted this one in my simple PAM module. [2-factor authentication & writing PAM modules](http://ben.akrin.com/?p=1068) Gives an example program that uses PAM. I adapted this for testing my PAM module. [Example PAM application](http://www.kernel.org/pub/linux/libs/pam/Linux-PAM-html/adg-example.html)