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Update comments in strcpher.cpp

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Jeffrey Walton 2021-11-29 10:41:49 -05:00
parent e546fb74d7
commit c4e257e685
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1 changed files with 31 additions and 25 deletions
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52
strciphr.cpp
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@ -1,14 +1,15 @@
// strciphr.cpp - originally written and placed in the public domain by Wei Dai
// TODO: Figure out what is happening in ProcessData. The issue surfaced for
// CFB_CipherTemplate<BASE>::ProcessData when we cut-in Cryptogams
// TODO: Figure out what is happening in ProcessData. The issue surfaced
// for CFB_CipherTemplate<BASE>::ProcessData when we cut-in Cryptogams
// AES ARMv7 asm. Then again in AdditiveCipherTemplate<S>::ProcessData
// for CTR mode with HIGHT, which is a 64-bit block cipher. In both cases,
// inString == outString leads to incorrect results. We think it relates to
// aliasing violations because inString == outString.
// inString == outString leads to incorrect results. We think it relates
// to aliasing violations because inString == outString.
//
// Also see https://github.com/weidai11/cryptopp/issues/683 and
// https://github.com/weidai11/cryptopp/issues/1010.
// Also see https://github.com/weidai11/cryptopp/issues/683,
// https://github.com/weidai11/cryptopp/issues/1010 and
// https://github.com/weidai11/cryptopp/issues/1088.
#include "pch.h"
@ -75,6 +76,17 @@ void AdditiveCipherTemplate<S>::GenerateBlock(byte *outString, size_t length)
}
}
// TODO: Figure out what is happening in ProcessData. The issue surfaced
// for CFB_CipherTemplate<BASE>::ProcessData when we cut-in Cryptogams
// AES ARMv7 asm. Then again in AdditiveCipherTemplate<S>::ProcessData
// for CTR mode with HIGHT, which is a 64-bit block cipher. In both cases,
// inString == outString leads to incorrect results. We think it relates
// to aliasing violations because inString == outString.
//
// Also see https://github.com/weidai11/cryptopp/issues/683,
// https://github.com/weidai11/cryptopp/issues/1010 and
// https://github.com/weidai11/cryptopp/issues/1088.
template <class S>
void AdditiveCipherTemplate<S>::ProcessData(byte *outString, const byte *inString, size_t length)
{
@ -88,14 +100,6 @@ void AdditiveCipherTemplate<S>::ProcessData(byte *outString, const byte *inStrin
PolicyInterface &policy = this->AccessPolicy();
unsigned int bytesPerIteration = policy.GetBytesPerIteration();
// GCC and Clang do not like this for CTR mode and 64-bit ciphers like HIGHT.
// The incorrect result is a partial string of 0's instead of plaintext or
// ciphertext. Recovered plaintext is partially garbage.
//
// It almost feels as if the compiler does not see the string is transformed
// in-place so it short-circuits the transform. In this case, if we use a
// stand-alone reproducer with the same data then the issue is present.
byte* savedOutString = outString;
size_t savedLength = length;
bool copyOut = false;
@ -223,6 +227,17 @@ void CFB_CipherTemplate<BASE>::Resynchronize(const byte *iv, int length)
m_leftOver = policy.GetBytesPerIteration();
}
// TODO: Figure out what is happening in ProcessData. The issue surfaced
// for CFB_CipherTemplate<BASE>::ProcessData when we cut-in Cryptogams
// AES ARMv7 asm. Then again in AdditiveCipherTemplate<S>::ProcessData
// for CTR mode with HIGHT, which is a 64-bit block cipher. In both cases,
// inString == outString leads to incorrect results. We think it relates
// to aliasing violations because inString == outString.
//
// Also see https://github.com/weidai11/cryptopp/issues/683,
// https://github.com/weidai11/cryptopp/issues/1010 and
// https://github.com/weidai11/cryptopp/issues/1088.
template <class BASE>
void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString, size_t length)
{
@ -237,15 +252,6 @@ void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString
unsigned int bytesPerIteration = policy.GetBytesPerIteration();
byte *reg = policy.GetRegisterBegin();
// GCC and Clang do not like this on ARM when inString == outString. The incorrect
// result is a string of 0's instead of plaintext or ciphertext. The 0's trace back
// to the allocation for the std::string in datatest.cpp. Elements in the string
// are initialized to their default value, which is 0.
//
// It almost feels as if the compiler does not see the string is transformed
// in-place so it short-circuits the transform. However, if we use a stand-alone
// reproducer with the same data then the issue is _not_ present.
byte* savedOutString = outString;
size_t savedLength = length;
bool copyOut = false;