linux-kernel - Re: udp bind() fails with EACCESS when selinux enforcing, but no audit messages

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Date:	Thu, 11 Sep 2008 13:44:01 -0400
From:	"David P. Quigley" <dpquigl@...ho.nsa.gov>
To:	Enrique Perez-Terron <enrio@...ine.no>
Cc:	linux-kernel@...r.kernel.org, fedora-selinux-list@...hat.com
Subject: Re: udp bind() fails with EACCESS when selinux enforcing, but no
	audit messages

I'm pretty sure this doesn't have anything to do with the kernel end but
is probably some sort of policy issue instead. I've CCed the
fedora-selinux list for an answer. The CC to linux-kernel should
probably be dropped from the reply there.

Dave

On Thu, 2008-09-11 at 17:34 +0200, Enrique Perez-Terron wrote:
> Fedora core 9 stock kernel 2.6.25.108 i586
> 
> Udp bind() fails with EACCESS when selinux enforcing, but no audit
> messages.
> 
> How to reproduce:
> 
> In startup scripts, configure rpc.statd to use the fixed port 34.
> This port does not occur in /etc/services
> (In /etc/sysconfig/nfs, STATD_PORT=34)
> 
> Write the following script, run it with bash -x.
> 
> #!/bin/bash
> 
> TESTDIR=/var/tmp/se-bind-test-$$
> mkdir $TESTDIR  # to hold about 50 files
> cd $TESTDIR
> 
> # Stop NFS:
> service nfs stop
> service nfslock stop
> 
> # Gather some baseline data for easy comparison
> echo 1 /selinux/enforce  # just in case
> dmesg                       > dmesg-enforc-before
> wc /var/log/audit/audit.log > audit-enforc-before
> 
> # This fails
> strace -o enforc -ff service nfslock start
> 
> # But no new messages in logs
> dmesg                       > dmesg-enforc-after
> wc /var/log/audit/audit.log > audit-enforc-after
> 
> # Try again in permissive mode
> echo 0 /selinux/enforce
> dmesg                       > dmesg-nonenf-before
> wc /var/log/audit/audit.log > audit-nonenf-before
> 
> # Since this works, daemon starts, and strace hangs on
> # Need sigkill; sigint does not work. Why?
> (sleep 5; killall -9 strace) &
> strace -o nonenf -ff service nfslock start
> 
> # Just for symmetry
> dmesg                       > dmesg-nonenf-after
> wc /var/log/audit/audit.log > audit-nonenf-after
> 
> # Check that there are no audits.
> diff dmesg-enforc-before dmesg-enforc-after
> diff audit-enforc-before audit-enforc-after
> 
> # There are several other calls to bind() that are not prevented
> grep -E '^bind|^socket' enforc.*
> grep -E '^bind|^socket' nonenf.*
> 
> Regards
> 
> --
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