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Bug 1400234 - AVC when hostname as ksh cmd subs in cluster env
Summary: AVC when hostname as ksh cmd subs in cluster env
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: selinux-policy
Version: 6.7
Hardware: All
OS: Linux
medium
medium
Target Milestone: rc
: ---
Assignee: Lukas Vrabec
QA Contact: Milos Malik
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-11-30 17:36 UTC by Filip Krska
Modified: 2020-04-15 14:55 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2017-03-21 09:49:52 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Knowledge Base (Solution) 2861661 0 None None None 2017-01-16 15:36:11 UTC
Red Hat Product Errata RHBA-2017:0627 0 normal SHIPPED_LIVE selinux-policy bug fix update 2017-03-21 12:29:23 UTC

Description Filip Krska 2016-11-30 17:36:28 UTC 
Description of problem:

When hostname is used in ksh scripts inside $() command substitution in cluster environment AVC denial prevents to writ output to tmpfile

Analogous to Bug 1040020

Adding

allow hostname_t cluster_tmp_t:file { read write };

rule helps to workaround the issue.


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

selinux-policy-3.7.19-231.el6_5.3.noarch

How reproducible:

Always

Steps to Reproduce:
1. Create script

# cat /tmp/hostname.ksh 
#!/bin/ksh

setenforce 1

MYHOST=$(/bin/hostname)

echo $MYHOST

setenforce 0

2.

# setenforce 0

3.

# runcon -t cluster_t -r system_r ksh /tmp/hostname.ksh

Actual results:

empty output

Expected results:

hostname echoed

Additional info:

type=AVC msg=audit(1480515061.350:279297): avc:  denied  { read write } for  pid=28277 comm="hostname" path=2F746D702F736631642E72646F202864656C6574656429 dev=dm-0 ino=438189 scontext=unconfined_u:system_r:hostname_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:cluster_tmp_t:s0 tclass=file

# echo 2F746D702F736631642E72646F202864656C6574656429|sed 's/\(..\)/\1 /g'|hex2bytes |strings
/tmp/sf1d.rdo (deleted)

ksh uses tmpfiles for temporary storing substituted command's output so there may be more types than just cluster_tmp_t affected.
Comment 1 Zdenek Pytela 2016-12-01 10:13:14 UTC 
Interesting, I can confirm the behaviour, but my ausearch results differ:

  # runcon -t cluster_t -r system_r ksh /tmp/hostname.ksh
----
type=PATH msg=audit(12/01/16 10:03:36.854:58) : item=0 name=/bin/ksh inode=525305 dev=fd:00 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:shell_exec_t:s0 nametype=NORMAL
type=CWD msg=audit(12/01/16 10:03:36.854:58) :  cwd=/root
type=SYSCALL msg=audit(12/01/16 10:03:36.854:58) : arch=x86_64 syscall=execve success=no exit=-13(Permission denied) a0=0x7ffd02228f35 a1=0x7ffd02229160 a2=0x7ffd02229178 a3=0x1f items=1 ppid=5969 pid=6071 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=pts0 ses=1 comm=runcon exe=/usr/bin/runcon subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(12/01/16 10:03:36.854:58) : avc:  denied  { transition } for  pid=6071 comm=runcon path=/bin/ksh93 dev=dm-0 ino=525305 scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:cluster_t:s0-s0:c0.c1023 tclass=process
----

  # runcon -t cluster_t -r system_r /bin/ksh93 /tmp/hostname.ksh
----
type=PATH msg=audit(12/01/16 10:11:43.767:92) : item=1 name=(null) inode=524597 dev=fd:00 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL
type=PATH msg=audit(12/01/16 10:11:43.767:92) : item=0 name=/bin/ksh93 inode=525305 dev=fd:00 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:shell_exec_t:s0 nametype=NORMAL
type=CWD msg=audit(12/01/16 10:11:43.767:92) :  cwd=/root
type=EXECVE msg=audit(12/01/16 10:11:43.767:92) : argc=2 a0=/bin/ksh93 a1=/tmp/hostname.ksh
type=SYSCALL msg=audit(12/01/16 10:11:43.767:92) : arch=x86_64 syscall=execve success=yes exit=0 a0=0x7ffeaf61d666 a1=0x7ffeaf61cdf0 a2=0x7ffeaf61ce08 a3=0x1f items=2 ppid=5969 pid=6177 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=pts0 ses=1 comm=ksh93 exe=/bin/ksh93 subj=unconfined_u:system_r:cluster_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(12/01/16 10:11:43.767:92) : avc:  denied  { transition } for  pid=6177 comm=runcon path=/bin/ksh93 dev=dm-0 ino=525305 scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:cluster_t:s0-s0:c0.c1023 tclass=process
----
type=PATH msg=audit(12/01/16 10:11:43.815:98) : item=1 name=(null) inode=524597 dev=fd:00 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL
type=PATH msg=audit(12/01/16 10:11:43.815:98) : item=0 name=/bin/hostname inode=525286 dev=fd:00 mode=file,755 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:hostname_exec_t:s0 nametype=NORMAL
type=CWD msg=audit(12/01/16 10:11:43.815:98) :  cwd=/root
type=EXECVE msg=audit(12/01/16 10:11:43.815:98) : argc=1 a0=/bin/hostname
type=SYSCALL msg=audit(12/01/16 10:11:43.815:98) : arch=x86_64 syscall=execve success=yes exit=0 a0=0x7f91dc7f2958 a1=0x7f91dc7f26f0 a2=0x7f91dc7f2818 a3=0x8 items=2 ppid=6177 pid=6181 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=pts0 ses=1 comm=hostname exe=/bin/hostname subj=unconfined_u:system_r:hostname_t:s0-s0:c0.c1023 key=(null)
type=AVC msg=audit(12/01/16 10:11:43.815:98) : avc:  denied  { write } for  pid=6181 comm=hostname path=/tmp/sf2d.1l8 (deleted) dev=dm-0 ino=522874 scontext=unconfined_u:system_r:hostname_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:cluster_tmp_t:s0 tclass=file
----

policy includes dontaudit rules

  $ rpm -q ksh selinux-policy
ksh-20120801-33.el6.x86_64
selinux-policy-3.7.19-292.el6_8.2.noarch

  $ ls -Z /bin/ksh /etc/alternatives/ksh /bin/ksh93 /tmp/hostname.ksh
lrwxrwxrwx. root root unconfined_u:object_r:bin_t:s0   /bin/ksh -> /etc/alternatives/ksh
-rwxr-xr-x. root root system_u:object_r:shell_exec_t:s0 /bin/ksh93
lrwxrwxrwx. root root unconfined_u:object_r:etc_t:s0   /etc/alternatives/ksh -> /bin/ksh93
-rw-r--r--. root root unconfined_u:object_r:user_tmp_t:s0 /tmp/hostname.ksh
Comment 7 errata-xmlrpc 2017-03-21 09:49:52 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2017-0627.html
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