Tor  0.4.6.0-alpha-dev
ctime Directory Reference

lib/ctime: Constant-time code to avoid side-channels.

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Files

file  di_ops.c [code]
 Functions for data-independent operations.
 
file  di_ops.h [code]
 Headers for di_ops.c.
 

Detailed Description

lib/ctime: Constant-time code to avoid side-channels.

This module contains constant-time implementations of various data comparison and table lookup functions. We use these in preference to memcmp() and so forth, since memcmp() can leak information about its inputs based on how fast it returns. In general, your code should call tor_memeq() and tor_memneq(), not memcmp().

We also define some non-constant-time wrappers for memcmp() here: Since we consider calls to memcmp() to be in error, we require that code that actually doesn't need to be constant-time to use the fast_memeq() / fast_memneq() / fast_memcmp() aliases instead.