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Bug 1852364 - xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled fails when a symlink or regular file is labeled with "device_t" [rhel-7.9.z]
Summary: xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled fails when ...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: scap-security-guide
Version: 7.8
Hardware: All
OS: Linux
high
high
Target Milestone: rc
: ---
Assignee: Vojtech Polasek
QA Contact: Matus Marhefka
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-06-30 09:22 UTC by Renaud Métrich
Modified: 2023-12-15 18:21 UTC (History)
8 users (show)

Fixed In Version: scap-security-guide-0.1.54-3.el7_9
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-04-27 11:30:11 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Renaud Métrich 2020-06-30 09:22:45 UTC 
Description of problem:

When a symlink or a regular file in /dev is labeled with "device_t" exists, the rule xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled fails.

The rule should only deal with special devices and skip the rest, but currently it deals with everything which is not a directory:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
  <linux:selinuxsecuritycontext_object comment="device_t in /dev" id="object_selinux_all_devicefiles_labeled" version="1">
    <linux:behaviors recurse_direction="down" />
    <linux:path>/dev</linux:path>
    <linux:filename operation="pattern match">^.*$</linux:filename>
    <filter action="include">state_selinux_all_devicefiles_labeled</filter>
  </linux:selinuxsecuritycontext_object>
  <linux:selinuxsecuritycontext_state comment="do it" id="state_selinux_all_devicefiles_labeled" version="1">
    <linux:type datatype="string" operation="equals">device_t</linux:type>
  </linux:selinuxsecuritycontext_state>
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

From the description and remediation, the rule should only deal with special devices:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
    To check for unlabeled device files, run the following command:
    <pre>$ sudo find /dev -context *:device_t:* \( -type c -o -type b \) -printf "%p %Z\n"</pre>
    It should produce no output in a well-configured system.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

This is an issue with Veritas software which creates symlink /dev/vx/rdmp to directory /dev/vx/dmp.


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

All


How reproducible:

ALWAYS

Steps to Reproduce:
1. Create a symlink to a directory in /dev

  # ln -s /dev/virtio-ports /dev/foo
  # restorecon -F /dev/foo

  # ls -Z /dev/foo
  lrwxrwxrwx. root root system_u:object_r:device_t:s0    /dev/foo -> /dev/virtio-ports
  
2. Execute the rule

  # oscap xccdf eval --profile xccdf_org.ssgproject.content_profile_stig --rule xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled /usr/share/xml/scap/ssg/content/ssg-rhel7-ds.xml

Actual results:

fail

Expected results:

pass

Additional info:

The real use case is symlink /dev/vx/rdmp to directory /dev/vx/dmp.
Comment 2 Christophe Besson 2020-06-30 13:56:27 UTC 
Additionally, there are some related warnings while using oscap, likely for the same reasons.

~~~
# oscap xccdf eval --fetch-remote-resources --profile xccdf_org.ssgproject.content_profile_stig --results arf.xml --report /var/tmp/stig-report.html --rule xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled /usr/share/xml/scap/ssg/content/ssg-rhel7-ds.xml
Downloading: https://www.redhat.com/security/data/oval/com.redhat.rhsa-RHEL7.xml ... ok
Title   Ensure No Device Files are Unlabeled by SELinux
Rule    xccdf_org.ssgproject.content_rule_selinux_all_devicefiles_labeled
Ident   CCE-27326-8
E: probe_selinuxsecuritycontext: Can't get context for /dev/fd/3: No such file or directory
E: probe_selinuxsecuritycontext: Can't get context for /dev/fd/3: No such file or directory
Result  pass
~~~

/dev/fd being a symlink to /proc/self/fd:
~~~
# ll -Zd /dev/fd
lrwxrwxrwx. root root system_u:object_r:device_t:s0    /dev/fd -> /proc/self/fd
~~~

According to the strace, the fd 3 is closed by the PID 6455, which is a thread of 6451, which corresponds to the following binary:
`/usr/libexec/openscap/probe_selinuxsecuritycontext`.
~~~
6455  12:18:14.603506 lstat("/dev/fd/3", {st_dev=makedev(0, 3), st_ino=59893, st_mode=S_IFLNK|0500, st_nlink=1, st_uid=0, st_gid=0, st_blksize=1024, st_blocks=0,
 st_size=64, st_atime=1592993894 /* 2020-06-24T12:18:14.525163635+0200 */, st_atime_nsec=525163635, st_mtime=1592993894 /* 2020-06-24T12:18:14.524163614+0200 */,
 st_mtime_nsec=524163614, st_ctime=1592993894 /* 2020-06-24T12:18:14.524163614+0200 */, st_ctime_nsec=524163614}) = 0 <0.000011>
[cut]
6455  12:18:14.604087 getdents(3</proc/6451/fd>, [], 32768) = 0 <0.000009>
6455  12:18:14.604120 close(3</proc/6451/fd>) = 0 <0.000009>
[cut]
6455  12:18:14.604651 getxattr("/dev/fd/2", "security.selinux", "unconfined_u:object_r:user_devpts_t:s0", 255) = 39 <0.000013>
6455  12:18:14.604713 getxattr("/dev/fd/3", "security.selinux", 0x7f0da400ecf0, 255) = -1 ENOENT (No such file or directory) <0.000015>
6455  12:18:14.604769 flock(2</dev/pts/0<char 136:0>>, LOCK_EX) = 0 <0.000022>
6455  12:18:14.604833 write(2</dev/pts/0<char 136:0>>, "E: probe_selinuxsecuritycontext: ", 33) = 33 <0.000023>
6455  12:18:14.604887 write(2</dev/pts/0<char 136:0>>, "Can't get context for /dev/fd/3: No such file or directory", 58) = 58 <0.000011>
~~~

/dev/fd/3 was a symlink to /proc/self/fd, which is usually the case. And this file descriptor has been closed by oscap a few calls before.
This fd has likely been created by something like readdir("/dev/fd"), and then all the results are iterated, including this closed fd. 

I won't open another BZ for that, since not following the symlinks would fix it.
Comment 3 Vojtech Polasek 2020-07-09 07:32:46 UTC 
Fixed upstream:
https://github.com/ComplianceAsCode/content/pull/5911
Comment 20 errata-xmlrpc 2021-04-27 11:30:11 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 (scap-security-guide bug fix and enhancement update), 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://access.redhat.com/errata/RHBA-2021:1383
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