This material was generated by ChatGPT-4 from a transcript of the Discord help channel for this module.
General Tips and Tricks:
- When working with file struct exploits, think of "reading from a file to memory" and "writing from memory to a file" to avoid confusion with read/write terminology.
- In a vtable exploit, the _wide_data struct and the exploited file struct can be separate or overlapping.
- If you encounter a segfault when dealing with the _lock attribute, make sure it is set properly.
- Using debugging information as a leak is not against the spirit of the challenges, as the goal is to capture the flag.
- Make use of GDB breakpoints to identify where the code may have issues or find potential exploits.
- Double-check your interaction with scanf and consider using time.sleep() to resolve issues with whitespace-delimited parsers.
- When using Pwn tool, be mindful of using p.clean().decode().
- If you find an issue in the code or exploit, such as incorrect function calls or logic, make sure to point it out and resolve it.
- For challenges involving file manipulation, you can potentially avoid using close_file by manipulating the fileno directly.
- When performing a vtable exploit, you have control over the first argument passed to a function, making it possible to get a strcmp check to pass.
Challenge-specific Tips and Tricks:
- Level 3: The solution is very simple: just replace the file descriptor.
- Level 4: Send the address of the 'win' function and fill up the rest of the buffer.
- Level 7: The solution does not require overlapping structs, but overlapping can be necessary in later challenges.
- Level 7: Calculate the offset from your leak to fp._lock's value, and make it point to a null byte, so the lock can be claimed.
- Level 7: The solution can be found by understanding the pointers correctly. Rob's last lecture on gdb can be very helpful for this level.
- Level 8: A vtable exploit can be used to solve this challenge.
- Level 9: Jump to a location in the win function where your FSOP attack won't get activated again.
- Level 12: When using close_file, be cautious of double free or invalid pointer issues.
- Level 13: To resolve issues with stdin breaking after using close_file, consider alternative methods to get an arbitrary read without using close_file.
- Level 13: One approach is to perform a leak using write_file and an overwrite using read_file.
- Level 14: Using close_file might be useful. However, be careful not to close file descriptor 1 when leaking information; otherwise, nothing will be printed to stdout.
- Level 16: There is a way to leak the required address, but it may require creative thinking.
- Level 16: To leak the stack address for the ROP chain, refer to lectures and office hours for inspiration, but be prepared for creative thinking.
- Level 16: An intended solution is to attack the stdio structures inside LIBC to leak the flag.
- Level 18-20: If encountering issues while working on these levels, consider adjusting your exploit to avoid additional restrictions or barriers.
- Level 18: Make sure to resolve any issues involving incorrect function calls or logic, such as the read_notes issue.