Bug 1298514

+++ This bug was initially created as a clone of Bug #1184260 +++

Description of problem:

If tcpdump is called with the -Z and -w options, unless the argument to the -Z option is "root", tcpdump will attempt to chown the capture file specified by the -w option to the user specified with the -Z option. (It takes this action even if the file is already owned by the user specified with -Z.)

However, even if the capture file has the netutils_tmp_t file context, SELinux denies tcpdump (that is, the netutils_t type) the ability to chown the capture file. This causes tcpdump to immediately fail and exit.

Similarly, tcpdump will call setattr() on a pre-existing capture file if the mode of the capture file isn't already what tcpdump expects. The call to setattr() also is denied by SELinux.

(Most people won't see these issues, because most people run tcpdump from interactive sessions that are in unconfined_t. But we are attempting to run tcpdump in an automated fashion via systemd, which is how we encountered the problem.)

Version-Release number of selected component (if applicable):
selinux-policy-3.7.19-287.el6.noarch
selinux-policy-doc-3.7.19-287.el6.noarch
selinux-policy-minimum-3.7.19-287.el6.noarch
selinux-policy-mls-3.7.19-287.el6.noarch
selinux-policy-targeted-3.7.19-287.el6.noarch
tcpdump-4.0.0-9.20090921gitdf3cb4.2.el6.x86_64

How reproducible:
Call tcpdump with "-Z tcpdump -w capturefile". (If your login is in the unconfined context, you will need to use runcon to ensure tcpdump runs in netutils_t.)

Steps to Reproduce:
# cd /tmp
# rm -f ./capturefile
# runcon system_u:system_r:initrc_t:s0 /bin/bash -c "/usr/sbin/tcpdump -i lo -Z tcpdump -w ./capturefile"
tcpdump: Couldn't change ownership of savefile
# 

Actual results (enforcing mode):
----
type=PATH msg=audit(01/14/2016 10:57:05.059:287) : item=0 name=./capturefile inode=187869 dev=fc:03 mode=file,644 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:netutils_tmp_t:s0 nametype=NORMAL 
type=CWD msg=audit(01/14/2016 10:57:05.059:287) :  cwd=/tmp 
type=SYSCALL msg=audit(01/14/2016 10:57:05.059:287) : arch=x86_64 syscall=chown success=no exit=-1(Operation not permitted) a0=0x1cf5a40 a1=tcpdump a2=tcpdump a3=0x7ffc6a439120 items=1 ppid=19664 pid=19668 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=pts0 ses=1 comm=tcpdump exe=/usr/sbin/tcpdump subj=system_u:system_r:netutils_t:s0 key=(null) 
type=AVC msg=audit(01/14/2016 10:57:05.059:287) : avc:  denied  { chown } for  pid=19668 comm=tcpdump capability=chown  scontext=system_u:system_r:netutils_t:s0 tcontext=system_u:system_r:netutils_t:s0 tclass=capability 
----

Expected results:
 * no SELinux denials