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Convert GCM to use runtime blocksize checking (Issue 408)

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GCM is still only defined for 16-byte ciphers, but this is where we need to be when we add the larger polynomials
This commit is contained in:
Jeffrey Walton 2017-08-12 16:14:29 -04:00
parent f5aa6f1f06
commit 7d21cdd54e
No known key found for this signature in database
GPG Key ID: B36AB348921B1838
2 changed files with 22 additions and 9 deletions
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25
gcm.cpp
View File

@ -325,7 +325,13 @@ void GCM_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const
BlockCipher &blockCipher = AccessBlockCipher();
blockCipher.SetKey(userKey, keylength, params);
if (blockCipher.BlockSize() != REQUIRED_BLOCKSIZE)
// GCM is only defined for 16-byte block ciphers at the moment.
// However, variable blocksize support means we have to defer
// blocksize checks to runtime after the key is set. Also see
// https://github.com/weidai11/cryptopp/issues/408.
const unsigned int blockSize = blockCipher.BlockSize();
CRYPTOPP_ASSERT(blockSize == REQUIRED_BLOCKSIZE);
if (blockSize != REQUIRED_BLOCKSIZE)
throw InvalidArgument(AlgorithmName() + ": block size of underlying block cipher is not 16");
int tableSize, i, j, k;
@ -335,7 +341,7 @@ void GCM_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const
{
// Avoid "parameter not used" error and suppress Coverity finding
(void)params.GetIntValue(Name::TableSize(), tableSize);
tableSize = s_clmulTableSizeInBlocks * REQUIRED_BLOCKSIZE;
tableSize = s_clmulTableSizeInBlocks * blockSize;
}
else
#elif CRYPTOPP_BOOL_ARM_PMULL_AVAILABLE
@ -343,7 +349,7 @@ void GCM_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const
{
// Avoid "parameter not used" error and suppress Coverity finding
(void)params.GetIntValue(Name::TableSize(), tableSize);
tableSize = s_clmulTableSizeInBlocks * REQUIRED_BLOCKSIZE;
tableSize = s_clmulTableSizeInBlocks * blockSize;
}
else
#endif
@ -359,10 +365,10 @@ void GCM_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const
#endif
}
m_buffer.resize(3*REQUIRED_BLOCKSIZE + tableSize);
m_buffer.resize(3*blockSize + tableSize);
byte *table = MulTable();
byte *hashKey = HashKey();
memset(hashKey, 0, REQUIRED_BLOCKSIZE);
memset(hashKey, 0, blockSize);
blockCipher.ProcessBlock(hashKey);
#if CRYPTOPP_BOOL_AESNI_INTRINSICS_AVAILABLE
@ -537,6 +543,13 @@ void GCM_Base::Resync(const byte *iv, size_t len)
BlockCipher &cipher = AccessBlockCipher();
byte *hashBuffer = HashBuffer();
// GCM is only defined for 16-byte block ciphers at the moment.
// However, variable blocksize support means we have to defer
// blocksize checks to runtime after the key is set. Also see
// https://github.com/weidai11/cryptopp/issues/408.
const unsigned int blockSize = cipher.BlockSize();
CRYPTOPP_ASSERT(blockSize == REQUIRED_BLOCKSIZE);
if (len == 12)
{
memcpy(hashBuffer, iv, len);
@ -568,7 +581,7 @@ void GCM_Base::Resync(const byte *iv, size_t len)
}
if (m_state >= State_IVSet)
m_ctr.Resynchronize(hashBuffer, REQUIRED_BLOCKSIZE);
m_ctr.Resynchronize(hashBuffer, blockSize);
else
m_ctr.SetCipherWithIV(cipher, hashBuffer);

6
gcm.h
View File

@ -74,9 +74,9 @@ protected:
virtual GCM_TablesOption GetTablesOption() const =0;
const BlockCipher & GetBlockCipher() const {return const_cast<GCM_Base *>(this)->AccessBlockCipher();};
byte *HashBuffer() {return m_buffer+REQUIRED_BLOCKSIZE;}
byte *HashKey() {return m_buffer+2*REQUIRED_BLOCKSIZE;}
byte *MulTable() {return m_buffer+3*REQUIRED_BLOCKSIZE;}
byte *HashBuffer() {return m_buffer+GetBlockCipher().BlockSize();}
byte *HashKey() {return m_buffer+2*GetBlockCipher().BlockSize();}
byte *MulTable() {return m_buffer+3*GetBlockCipher().BlockSize();}
inline void ReverseHashBufferIfNeeded();
class CRYPTOPP_DLL GCTR : public CTR_Mode_ExternalCipher::Encryption