| 1 | Intro |
| 2 | ===== |
| 3 | |
| 4 | 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. |
| 5 | |
| 6 | To build, either use the build scripts or use these commands: |
| 7 | |
| 8 | **Build the PAM module** |
| 9 | |
| 10 | `gcc -fPIC -fno-stack-protector -c src/mypam.c` |
| 11 | |
| 12 | `sudo ld -x --shared -o /lib/security/mypam.so mypam.o` |
| 13 | |
| 14 | 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. |
| 15 | |
| 16 | **Build Test** |
| 17 | |
| 18 | `g++ -o pam_test src/test.c -lpam -lpam_misc` |
| 19 | |
| 20 | OR |
| 21 | |
| 22 | `gcc -o pam_test src/test.c -lpam -lpam_misc` |
| 23 | |
| 24 | 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. |
| 25 | |
| 26 | Simple Usage |
| 27 | ------------ |
| 28 | |
| 29 | 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. |
| 30 | |
| 31 | The config files are located in `/etc/pam.d/` and the one I edited was `/etc/pam.d/common-auth`. |
| 32 | |
| 33 | 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: |
| 34 | |
| 35 | auth sufficient mypam.so |
| 36 | account sufficient mypam.so |
| 37 | |
| 38 | 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. |
| 39 | |
| 40 | 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. |
| 41 | |
| 42 | Resources |
| 43 | ========= |
| 44 | |
| 45 | I found these resources especially helpful: |
| 46 | |
| 47 | O'Reilly Guides: |
| 48 | ---------------- |
| 49 | |
| 50 | These guides give brief overviews about PAM and how to write modules. This is useful if you already have a little knowledge. |
| 51 | |
| 52 | * [Writing PAM Modules, Part One](http://linuxdevcenter.com/pub/a/linux/2002/05/02/pam_modules.html) |
| 53 | * [Writing PAM Modules, Part Two](http://linuxdevcenter.com/pub/a/linux/2002/05/23/pam_modules.html) |
| 54 | * [Writing PAM Modules, Part Three](http://linuxdevcenter.com/pub/a/linux/2002/05/30/pam_modules.html) |
| 55 | |
| 56 | Others |
| 57 | ------ |
| 58 | |
| 59 | Good example for simple authentication. I adapted this one in my simple PAM module. |
| 60 | |
| 61 | [2-factor authentication & writing PAM modules](http://ben.akrin.com/?p=1068) |
| 62 | |
| 63 | Gives an example program that uses PAM. I adapted this for testing my PAM module. |
| 64 | |
| 65 | [Example PAM application](http://www.kernel.org/pub/linux/libs/pam/Linux-PAM-html/adg-example.html) |