After having found the source of the GDB anti-debug trick, I started modifying GDB to work around the problem and fix the number of sections on the fly (it’s simple to calculate the real number of sections). I was coding on a long train trip and everything was going great… My hack worked and GDB fixed and loaded the file without a problem. Next step was to run the program but when I tried I had this surprise:...
Today I bring you something from the old projects trunk. Like many other millions of people I enjoy playing online Texas Hold’em Poker. I started with Pokerstars three years ago, and after a while, diabolical ideas came to my head about reversing the client to have a peek into their communication protocol (what else were you expecting? I love to break things!). The project was on hold for a long time (started when Windows was my daily OS)....
Well, it seems this is the GDB post season! The past days have been dedicated to mess around with GDB source code and today I have what I think it’s a nice story to tell. After hacking off my old wish of having the disassembly raw bytes to be printed (like Ollydbg, Softice, IDA, otx, etc…) I was interested in trying to fix one anti-debug trick. This presentation by nemo shows an anti-debug trick that works against GDB and others....
It’s not a breakthrough post but I finally found where the bug that messed up gdbinit is located. I got obsessed into this problem and started browsing GDB source code. I knew that the problem ocurred when the file or add-symbol commands were used. The difference from file to exec-file is that symbols are loaded so that was my starting point. This was more or less my flow: file -> file_command -> symbol_file_command -> symbol_file_add_main_1 -> symbol_file_add_name_with_addrs_or_offsets -> symbol_file_add_with_addrs_or_offsets -> symbol_file_add_with_addrs_or_offsets_using_objfile -> new_symfile_objfile -> clear_symtab_users -> clear_internalvars...
I had unconsciously found the workaround a few months ago while hacking around Little Snitch with kernel debugging. To make things easier I had a small GDB script to call the debug kit macros and set all the variables that are the source of the problem with gdbinit. This was something I never thought about, just accepted it. Today, while answering to a comment, the connection was made inside my brain (I love how the brain works!...