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pull/795/head
Jeffrey Walton 2019-01-25 19:49:17 -05:00
parent 779e28a9b0
commit 82f80124e6
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1 changed files with 9 additions and 5 deletions
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chacha.cpp
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@ -425,7 +425,10 @@ void ChaChaTLS_Policy::CipherResynchronize(byte *keystreamBuffer, const byte *IV
void ChaChaTLS_Policy::SeekToIteration(lword iterationCount) void ChaChaTLS_Policy::SeekToIteration(lword iterationCount)
{ {
// Should we throw here??? // Should we throw here??? If the initial block counter is
// large then we can wrap and process more data as long as
// data processed in the security context does not exceed
// 2^32 blocks or approximately 256 GB of data.
CRYPTOPP_ASSERT(iterationCount <= std::numeric_limits<word32>::max()); CRYPTOPP_ASSERT(iterationCount <= std::numeric_limits<word32>::max());
m_state[12] = (word32)iterationCount; // low word m_state[12] = (word32)iterationCount; // low word
} }
@ -447,11 +450,12 @@ void ChaChaTLS_Policy::OperateKeystream(KeystreamOperation operation,
ChaCha_OperateKeystream(operation, m_state, m_state[12], discard, ChaCha_OperateKeystream(operation, m_state, m_state[12], discard,
m_rounds, output, input, iterationCount); m_rounds, output, input, iterationCount);
// If this fires it means ChaCha_OperateKeystream generated a carry // If this fires it means ChaCha_OperateKeystream generated a counter
// that was discarded. The problem is, the RFC does not specify what // block carry that was discarded. The problem is, the RFC does not
// should happen when the counter block wraps. All we can do is // specify what should happen when the counter block wraps. All we can
// inform the user that something bad may happen because we don't // do is inform the user that something bad may happen because we don't
// know what we should do. // know what we should do.
// Also see https://github.com/weidai11/cryptopp/issues/790.
CRYPTOPP_ASSERT(discard==0); CRYPTOPP_ASSERT(discard==0);
} }