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pull/795/head
Jeffrey Walton 2019-01-25 19:04:34 -05:00
parent c1f9b484b7
commit 779e28a9b0
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1 changed files with 5 additions and 4 deletions
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chacha.cpp
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@ -79,10 +79,11 @@ typedef word32 WordType;
enum {BYTES_PER_ITERATION=64};
// MultiBlockSafe detects a condition that can arise in the SIMD
// implementations where we overflow one of the 32-bit state words
// during addition in an intermediate result. Conditions to trigger
// issue include a user seeks to around 2^32 blocks (256 GB of data).
// https://github.com/weidai11/cryptopp/issues/732
// implementations where we overflow one of the 32-bit state words during
// addition in an intermediate result. Preconditions for the issue include
// a user seeks to around 2^32 blocks (256 GB of data) for ChaCha; or a
// user specifies an arbitrarily large initial counter block for ChaChaTLS.
// Also see https://github.com/weidai11/cryptopp/issues/732.
inline bool MultiBlockSafe(unsigned int ctrLow, unsigned int blocks)
{
return 0xffffffff - ctrLow > blocks;