Bug 185973

Description of problem:

When SELinux is set to enforcing, the Email which would normally arise from
anacron's invocation of /etc/cron.daily has a blank body and subject

Version-Release number of selected component (if applicable):

anacron-2.3-34 ( FC4 Core )

How reproducible:

setenforce 1

Set logrotate to debug mode with "-v" in /etc/cron.daily/logrotate. This merely
ensures that at least one Job generates some output.

Leave machine depowered overnight,

Repower machine after 4am.
  
Actual results:

Empty Email from the cron.daily Job launched by anacron.
No obvious errors from SELinux.

Expected results:

logrotate output from the cron.daily Job.


Additional info:

After some investigation with SELinux enableaudit, it transpired that this
extra line in SELinux policy would re-enable the Email:

allow system_mail_t { system_crond_tmp_t }:file { append };

Even more investigation showed that anacron was not being careful enough in how
it passed the file-descriptor containing the Job output to sendmail.

anacron-2.3-34 opens a file-descriptor read/write on a temporary file to
accumulate stdout/stderr for passing to sendmail. Once the FD is open, the
tempfile is unlinked. Once the Job is finished, the descriptor is "turned
around" and used as stdin to a child sendmail process.

The problem appears to be that SELinux then forbids sendmail to have an open
inherited file-descriptor with write-permission on stdin.

As a patch for this problem, I've recoded runjob.c in anacron such that the
temporary file is opened twice ( once WRITE_ONLY , and once READ_ONLY ), with
the appropriate FD's passed to different places, and various FD's closed or
re-opened to /dev/null where appropriate.

This tested again against the normal SELinux strict policy
( selinux-policy-strict-1.27.1-2.22 )
without the file:append policy modification shown above.