Lightweight overflow checker.

Simply detect memory corruption as we say OVERFLOW. q You can get following information about overflow.

• Overflow bytes

• Memory address of the block

• Block size

• Backtrace(with filename : line-number)

ofchecker detect overflow writing to a region allocated by malloc() and suchlike.

Glibc malloc has similar mechanism MALLOC_CHECK_. It is easy to use and lightweight, and shows followings.

$ MALLOC_CHECK_=3 ./test/ofc_test
*** Error in `./test/ofc_test': free(): invalid pointer: 0x000000000153c010 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x741cf)[0x7f9c96c3e1cf]
/lib/x86_64-linux-gnu/libc.so.6(+0x82df6)[0x7f9c96c4cdf6]
./test/ofc_test(test_malloc+0x45)[0x400a92]
./test/ofc_test(main+0x13)[0x400d44]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7f9c96bebec5]
./test/ofc_test[0x400989]

ofchecker can show more infomation.

$ ./bin/ofchecker ./test/ofc_test
<ofchecker> : Corrupted memory after payload : 9 byte
<ofchecker> : Address : 0x1f32010
<ofchecker> : Size : 7
<ofchecker> : ***  Start backtrace ***
./src/libofcbt.so(ofc_bt+0x18)[0x7f82df3bd7c8]
./src/libofc.so(free+0xc8)[0x7f82df5bfc18]
/home/tatezono/github/ofchecker/test/test.c:18
/home/tatezono/github/ofchecker/test/test.c:114
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7f82df018ec5]
./test/ofc_test[0x400989]
<ofchecker> : ***   End backtrace  ***

ofcheker provides multiple byte overflow detection and showing backtrace when overflow is detected.

When you call malloc(), ofchecker simply add extra region(red-zone) after your payload filled by magic word, and when free(), check the red-zone wheter be overwritten or not.

ofchecker provides glibc like malloc(), calloc(), realloc(), posix_memalign() and free(). The functions creates or checks red-zone and then call glibc real malloc()(or calloc(), realloc(), free()). So you can use ofchecker by linking to your applications directly or by using LD_PRELOAD.

In addition, ofchecker script convert memory addresses in backtrace to filename:line-number.

1. Make sure you have installed the dependency:

   • CMake 2.8.1 or later

2. Checkout and build:

   $ git clone https://github.com/zonomasa/ofchecker.git $ cd ofchecker $ cmake . $ make

Now that you have libofc.so and libofcbt.so in your 'src' dir.

You can use ofchecker by directly linking with your application or just use LD_PRELOAD.

To use by LD_PRELOAD do:

$ LD_PRELOAD="./src/libofc.so ./src/libofcbt.so" $(your_application)
for example:
$ LD_PRELOAD="./src/libofc.so ./src/libofcbt.so" ./test/ofc_test

Furthermore you can use bin/ofchecker which be able to use LD_PRELOAD easily, and convert backtrace infomation to user friendly style.

$ ./bin/ofchecker ./test/ofc_test

• Now Prototype version.
  • Delete Debug message.

1. Fork it ( https://github.com/zonomasa/ofchecker/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

• Copyright (c) 2014 TATEZONO Masaki
• License Apache License, Version 2.0