Filter environment variables

[topimiettinen]

Save all environment variables for later use in sandboxes, clear
environment and re-apply only whitelisted variables for the main
firejail process. All variables will be reapplied for the sandboxes by
env_apply().

[topimiettinen]

The commit eliminates the difference between start_application(0, fp) and start_application(1, fp) as now variables are applied unconditionally (because some of them don't exist anymore after clearenv()). To be honest, I'm not sure if there is now a change in behavior in some cases.

[topimiettinen]

Actually I'm pretty sure that all variables changed with setenv() in main Firejail process may be overwritten with the original values. So those setenv()s have to be changed to env_store()s.

[Vincent43]

Why TMP is whitelisted?

[smitsohu]

We used TMP to fix #2685

[smitsohu]

To be honest, I'm not sure if there is now a change in behavior in some cases.

A while back I had what I think is the same problem with sanitizing the umask. So if you like you can look out for umask(orig_umask) calls in order to find the exit points.

[topimiettinen]

In this version, the variables which Firejail uses internally are also moved to env storage for consistency. Thus the whitelist only applies to variables used by external libraries (libc/pthreads, libapparmor) and then it can be much shorter: only LANG, LANGUAGE, LC_MESSAGES.

Perhaps the sandboxed helper apps (fseccomp & friends) should also be run with a short list of variables: LANG etc. and internal variables starting with FIREJAIL_, otherwise they might need similar sanitizing (or perhaps they also need some sanitizing in any case to be sure). Only the final user app should get all variables restored.

[topimiettinen]

Latest build failure happens because tests expect that using --env=FIREJAIL_TEST_ARGUMENTS=yes (or exporting the environment variable FIREJAIL_TEST_ARGUMENTS from shell), the variable is passed also to the helper apps. Maybe this should be instead flagged with some other means, for example adding arguments to faudit like faudit --test-arguments. It would be simpler to just let the the variable pass.

[msva]

@topimiettinen ping?

Any progress here? ;)

We're all struggling (from env length checks) without your work ;)

[topimiettinen]

Sorry, I actually made a version which lets FIREJAIL_TEST_ARGUMENTS pass, but forgot to follow up. Thanks for the reminder. Let's see what the CIs think of the rebased version.

[topimiettinen]

Adding also PATH let the CI pass!

[msva]

@netblue30 ping? :D

[netblue30]

all merged!