Add persistence module for linux and osx

[alexmaloteaux]

This patch will create a pesistence mixin shared between osx / linux ans win persistence post module.

For Osx , the persistence is done through launchd by adding a crafted plist file in /Users/username/Library/LaunchAgents for normal user or /Library/LaunchDaemons for root. Keepalive is a feature of launchd

For Linux there is 4 differents methods :

1. Crontab : this method is the recommended one and will add a @reboot entry in the user crontab config while keeping previous configuration.
2. Autostart : This method works only if Xorg is detected. For normal user, it will add a desktop file in ~/.config/autostart and for root /etc/xdg/autostart will be used.
3. INIT : This method will add en entry in /etc/rc.local (only root)
4. Profile : This method will add en entry in the user shell profile file (bashrc, zshrc , cshrc ....).

Keepalive is done through a bashscript.

[jlee-r7]

All of the payload creation and handler stuff can be taken care of by the framework if you make this an Exploit::Local

[jlee-r7]

this should just be sysinfo which is a method defined on Post that caches the result, so multiple uses in the same module don't have to make unnecessary requests.

[alexmaloteaux]

Hi jlee-r7

1. All of the payload creation and handler stuff can be taken care of by the framework if you make this an Exploit::Local
   => I did no changed anything, it is the same methoid as it was in windows/persistences for month , just moved it to a mixin as seen with hdm

2. this should just be sysinfo which is a method defined on Post that caches the result, so multiple uses in the same module don't have to make unnecessary requests. => again , this has just been moved from windows/persistence to the mixin and was implemented like this for month , it is used only by windows atm

3. already implemented in Post::File => ha nice will use those then an change it in a commit

4. This will not work as expected when Metasploit is running on Windows. => it is defined in lib/msf/port/unix so i don't think windows post will use this mixin

5)Copy-paste comment => you have tiger eyes :) , this comment will be removed

[alexmaloteaux]

Have removed the comment and used the file/directory_exist method from post::File

For other remarks, it was like this for month and just moved to persistence mixin so may be better to use it that way.

Best Regards

[jlee-r7]

What I meant with the Exploit::Local comment was that this should not be a Post module. It uses a payload, so therefore it should be an exploit. The windows version was created before Exploit::Local was useful, so it gets a pass until I have time to port it.

[todb-r7]

Looks like @alexmaloteaux has abandoned this pull request -- no movement on a month, and the PR now has merge conflicts due to drift. Closing this out -- please reopen when you're ready to work on this again.