- Generic procedure (Windows or Linux)
- Buffer Overflow Tips
- pattern_create.rb
- pattern_offset.rb
- nasm_shell.rb
- Bad characters Python code
- Windows Buffer Overflows
- Identify vulnerable input field and payload length that causes overflow (Fuzzing)
- Identify offsets
- Detect bad characters
- Identify jump instruction opcode and usable return address
- Generate shellcode
- Exploit!
- 0x00 is usually a bad character, because it often serves as a string terminator in programming languages vulnerable to buffer overflows (C/C++).
- Return Addresses CANNOT contain bad characters (which is why the Return Address is identified after detecting bad characters).
- Confusing debugger errors encountered during bad character detection likely indicate a bad character.
- Shellcode will almost always be generated with the
EXITFUNC=thread
option. - Some vulnerable programs/services will always crash from buffer overflow conditions, regardless of how much preparation/compensation is done during exploit development.
Provided by the Metasploit Framework. Create unique pattern payloads to detect register offsets.
/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l [PAYLOAD_LENGTH]
Provided by the Metasploit Framework. Identify exact offsets where unique patterns reside.
/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q [VALUE] -l [PAYLOAD_LENGTH]
Provided by the Metasploit Framework. Convert x86 Assembly Language instructions into corresponding hexadecimal opcodes.
/usr/share/metasploit-framework/tools/exploit/nasm_shell.rb
badchars = ("\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10"
"\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x20"
"\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f\x30"
"\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f\x40"
"\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f\x50"
"\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f\x60"
"\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f\x70"
"\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f\x80"
"\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90"
"\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0"
"\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0"
"\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0"
"\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0"
"\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0"
"\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0"
"\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff")
- Goto memory address using button
- Click displayed memory address
- Press F2
- If warning message is displayed, click Yes
- Breakpoint is set when memory address is highlighted in Blue.
!mona modules
!mona find -s "[OPCODE]" -m [MODULE]
"[STRING]"[::-1].encode('hex').upper()
Can be useful for printing string-to-hexadecimal values in Windows buffer overflow exploits.