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Flag: Tornado! Hurricane!

Created: Sunday, May 27 2007 16:20.14 CDT

Modified: Monday, May 28 2007 17:32.18 CDT

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Canaries and format strings

Author: dennis

# Views: 2993

This code is found in a commercial, yet discontinued kernel-mode debugger! ;)

https://www.openrce.org/repositories/users/dennis/sice.gif

The implementation of debugger extensions must have been done in a rush:

1. sprintf is used instead of snprintf
2. a static buffer with a static size is used
3. a constant canary value is used instead of a (pseudo)random one
4. the return address is stored AFTER the static and overflowable buffer
5. the developer of a debugger extension can pass his own format string specifier to that function

Sample PoC can be found here.

Although this is a 0day, it has not been published since debugger extensions run in r0 environment anyway.

Fear the BADB0B0 !

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