mardi 20 septembre 2016

Break On Call and Break On Ret under gdb

1/ Adding BOC and BOR for gdb

As a reverse engineer, I like really gdb. It has a lot of cool features and is scriptable through python.

While I was solving a crackme challenge I needed a break on call and a break on ret instructions. I search the web and did not find what I wanted.

So, I developped a boc (break on call) and a bor (break on ret) function and sharing it today.

2/ How it works?

You just have to source a python file and you end up with three commands:
  • boc : activate break on call with boc on or boc off. You can choose by breaking or printing on call by boc break or boc print
  • bor : same commands for break on ret
  • go : if you have selected boc on and/or bor on, typing go will executing the binary until next call or next ret
 $ gdb -nx -q  
 (gdb) source bocbor.py   
 (gdb) boc  
 Status of Break on Call is off/break  
   Change with boc on/off and boc break/print  
 (gdb) bor  
 Status of Break on Ret is off/break  
   Change with bor on/off and bor break/print  
 (gdb) boc on  
 (gdb) boc  
 Status of Break on Call is on/break  
   Change with boc on/off and boc break/print  
 (gdb)  

3/ Please, just show me the code! 

It's on github
https://github.com/0xmitsurugi/gdbscripts
The Readme shows a typical bocbor session.

4/ Enjoy

Feedback, bugs: mail or twitter

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