Presented at
30C3 (2013),
Dec. 27, 2013, 6:30 p.m.
(60 minutes).
Violation of memory safety is still a major source of vulnerabilities in everyday systems. This talk presents the state of the art in compiler instrumentation to completely eliminate such vulnerabilities in C/C++ software.
<p>The hacker community has a lot of words for situations in which access to the wrong part of memory leads to an exploitable vulnerability: buffer overflow, integer overflows, stack smashing, heap overflow, use-after-free, double free and so on. Different words are used because the techniques to trigger the faulty memory access and to subsequently use that to gain code execution vary, but they all share a common root cause: violation of spatial and temporal memory safety.</p>
<p>If one looks at the C/C++ standard, the situations that tend to be exploitable are "unspecified". Usually, compiler writers take that as an excuse to cut corners, to gain that extra bit of performance in the benchmarks. Because, you know, who cares you're exploitable when you make a mistake, look how fast it is!</p>
<p>However, the standards also allow the compiler to introduce safety checks, to see whether access to a pointer actually touches the inside of an allocated object instead of the outside (spatial memory safety), and to make sure that the pointer being accessed actually points to an object that has been allocated, but not yet been freed again (temporal memory safety). Such compilers do exist, in the form of LLVM with specialized optimizer passes that introduce runtime safety checks.</p>
<p>This talk will look into the details of the implementation, the performance impact, practical handling, and of course, whether it really delivers the promised 100% protection against buffer overflows.</p>
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