gh-100163: allow re-assuming root privileges on subprocess invocations #134400
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The
subprocess.Popen
class takes user/group/extra groups parameters which allow invocations to run as a different user. When dropping privileges (i.e. the main program is running as root but wants to run a subprocess as an unprivileged user) this works fine. However, it fails if a program wants to drop privileges and re-assume them to run a subprocess.To allow this there are a couple of changes required:
setresuid
/setresgid
instead ofsetreuid
/setregid
so the saved user/group identity can be re-assumed after it has been dropped.Naturally we need to continue to set the user identity last when going from root to an unprivileged user, so the order of calls needs to be determined dynamically based on whether we are switching to or from root.