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Qualifying Event Style Sample Challenge - TNETS_00002


Original Versions

Known Vulnerabilities

  • CWE-122 - Heap-based Buffer Overflow

Author Information

"Jason L. Wright" jason@thought.net

DARPA performer group

Thought Networks (TNETS)

Description

Virtual pet ownership.

Feature List

This services allows the user to create virtual pets and have them perform a few rudimentary tricks. When a pet becomes too annoying, it can be deleted.

Vulnerability

Normally a pet is given a name right after it is created and never renamed. However, there's a bug in this program: when you rename a pet it appends to the current name. An annoyance to be sure, but worse, it allows for spilling into an adjacent C++ vtable.

To make life easier for the programmer (not the user), a "debug" trick can be performed which displays the address of each of the pet's "this" pointer.

Generic class of vulnerability

Heap-based Buffer Overflow

CWE classification

CWE-122: Heap based Buffer Overflow

Challenges

This CB is primarily provided to demonstrate the use of C++ as a challenge binary language. Several language features are used (static constructors/ destructors, virtual functions, overloading, etc.). Several features are explicitly not used: runtime type information (RTTI) and exceptions.

Future versions of this CB may use RTTI (it's not that hard to implement), but exceptions look painful (though libcgc.a now has setjmp/longjmp...).

The overflow is easy enough to create: it requires reasoning about the protocol and realizing that additional names for a pet are blindly concatenated with the existing name. To get an exploit working, a valid vtable must be constructed. The "debug" trick leaks the value of the "this" pointer for each pet (this cuts out reasoning about the "new operator"'s implementation.


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