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// chachapoly.cpp - written and placed in the public domain by Jeffrey Walton
// RFC 8439, Section 2.8, AEAD Construction, http://tools.ietf.org/html/rfc8439
#include "pch.h"
#include "chachapoly.h"
#include "algparam.h"
#include "misc.h"
#if CRYPTOPP_MSC_VERSION
# pragma warning(disable: 4244)
#endif
NAMESPACE_BEGIN(CryptoPP)
////////////////////////////// IETF ChaChaTLS //////////////////////////////
// RekeyCipherAndMac is heavier-weight than we like. The Authenc framework was
// predicated on BlockCiphers, where the key and key schedule could be
// calculated independent of the IV being used. However, the ChaCha and
// ChaCha20Poly1305 construction combines key setup and IV. That is, both are
// needed to key or rekey the cipher. Even a simple Resync() requires us to
// regenerate the initial state for both ChaCha20 and Poly1305.
void ChaCha20Poly1305_Base::RekeyCipherAndMac(const byte *userKey, size_t keylength, const NameValuePairs ¶ms)
{
// Derive MAC key
AlgorithmParameters block0 = MakeParameters("InitialBlock", (word64)0, true);
AccessSymmetricCipher().SetKey(userKey, keylength, CombinedNameValuePairs(params, block0));
// Only the first 256-bits are used to key the MAC
SecByteBlock derived(NULLPTR, 32);
AccessSymmetricCipher().ProcessString(derived, derived.size());
// Key the Poly1305 MAC
AccessMAC().SetKey(derived, derived.size(), params);
// Key the ChaCha20 cipher
AlgorithmParameters block1 = MakeParameters("InitialBlock", (word64)1, true);
AccessSymmetricCipher().SetKey(userKey, keylength, CombinedNameValuePairs(params, block1));
}
void ChaCha20Poly1305_Base::SetKeyWithoutResync(const byte *userKey, size_t userKeyLength, const NameValuePairs ¶ms)
{
CRYPTOPP_ASSERT(userKey && userKeyLength == 32);
m_userKey.Assign(userKey, userKeyLength);
// ChaCha/Poly1305 initial state depends on both the key and IV. The
// IV may or may not be present during the call to SetKeyWithoutResync.
// If the IV is present, the framework will call SetKeyWithoutResync
// followed by Resynchronize which calls Resync. In this case we defer
// calculating the initial state until the call to Resynchronize.
// If the IV is not present, it avoids calling ChaCha's SetKey without
// an IV, which results in an exception. In this case the user will need
// to call Resynchronize to key ChaCha and Poly1305.
// RekeyCipherAndMac(userKey, userKeyLength, params);
CRYPTOPP_UNUSED(params);
}
void ChaCha20Poly1305_Base::Resync(const byte *iv, size_t len)
{
CRYPTOPP_ASSERT(iv && len == 12);
RekeyCipherAndMac(m_userKey, m_userKey.SizeInBytes(),
MakeParameters(Name::IV(), ConstByteArrayParameter(iv,len)));
}
size_t ChaCha20Poly1305_Base::AuthenticateBlocks(const byte *data, size_t len)
{
AccessMAC().Update(data, len);
return 0;
}
void ChaCha20Poly1305_Base::AuthenticateLastHeaderBlock()
{
// Pad to a multiple of 16 or 0
const byte zero[16] = {0};
size_t pad = (16U - (m_totalHeaderLength % 16)) % 16;
AccessMAC().Update(zero, pad);
}
void ChaCha20Poly1305_Base::AuthenticateLastConfidentialBlock()
{
// Pad to a multiple of 16 or 0
const byte zero[16] = {0};
size_t pad = (16U - (m_totalMessageLength % 16)) % 16;
AccessMAC().Update(zero, pad);
}
void ChaCha20Poly1305_Base::AuthenticateLastFooterBlock(byte *mac, size_t macSize)
{
CRYPTOPP_ALIGN_DATA(8) byte length[2*sizeof(word64)];
PutWord(true, LITTLE_ENDIAN_ORDER, length+0, m_totalHeaderLength);
PutWord(true, LITTLE_ENDIAN_ORDER, length+8, m_totalMessageLength);
AccessMAC().Update(length, sizeof(length));
AccessMAC().TruncatedFinal(mac, macSize);
m_state = State_KeySet;
}
void ChaCha20Poly1305_Base::EncryptAndAuthenticate(byte *ciphertext, byte *mac, size_t macSize, const byte *iv, int ivLength, const byte *aad, size_t aadLength, const byte *message, size_t messageLength)
{
Resynchronize(iv, ivLength);
Update(aad, aadLength);
ProcessString(ciphertext, message, messageLength);
TruncatedFinal(mac, macSize);
}
bool ChaCha20Poly1305_Base::DecryptAndVerify(byte *message, const byte *mac, size_t macLength, const byte *iv, int ivLength, const byte *aad, size_t aadLength, const byte *ciphertext, size_t ciphertextLength)
{
Resynchronize(iv, ivLength);
Update(aad, aadLength);
ProcessString(message, ciphertext, ciphertextLength);
return TruncatedVerify(mac, macLength);
}
////////////////////////////// IETF XChaCha20 draft //////////////////////////////
// RekeyCipherAndMac is heavier-weight than we like. The Authenc framework was
// predicated on BlockCiphers, where the key and key schedule could be
// calculated independent of the IV being used. However, the ChaCha and
// ChaCha20Poly1305 construction combines key setup and IV. That is, both are
// needed to key or rekey the cipher. Even a simple Resync() requires us to
// regenerate the initial state for both ChaCha20 and Poly1305.
void XChaCha20Poly1305_Base::RekeyCipherAndMac(const byte *userKey, size_t keylength, const NameValuePairs ¶ms)
{
// Derive MAC key
AlgorithmParameters block0 = MakeParameters("InitialBlock", (word64)0, true);
AccessSymmetricCipher().SetKey(userKey, keylength, CombinedNameValuePairs(params, block0));
// Only the first 256-bits are used to key the MAC
SecByteBlock derived(NULLPTR, 32);
AccessSymmetricCipher().ProcessString(derived, derived.size());
// Key the Poly1305 MAC
AccessMAC().SetKey(derived, derived.size(), params);
// Key the ChaCha20 cipher
AlgorithmParameters block1 = MakeParameters("InitialBlock", (word64)1, true);
AccessSymmetricCipher().SetKey(userKey, keylength, CombinedNameValuePairs(params, block1));
}
void XChaCha20Poly1305_Base::SetKeyWithoutResync(const byte *userKey, size_t userKeyLength, const NameValuePairs ¶ms)
{
CRYPTOPP_ASSERT(userKey && userKeyLength == 32);
m_userKey.Assign(userKey, userKeyLength);
// XChaCha20/Poly1305 initial state depends on both the key and IV. The
// IV may or may not be present during the call to SetKeyWithoutResync.
// If the IV is present, the framework will call SetKeyWithoutResync
// followed by Resynchronize which calls Resync. In this case we defer
// calculating the initial state until the call to Resynchronize.
// If the IV is not present, it avoids calling ChaCha's SetKey without
// an IV, which results in an exception. In this case the user will need
// to call Resynchronize to key ChaCha and Poly1305.
// RekeyCipherAndMac(userKey, userKeyLength, params);
CRYPTOPP_UNUSED(params);
}
void XChaCha20Poly1305_Base::Resync(const byte *iv, size_t len)
{
CRYPTOPP_ASSERT(iv && len == 24);
RekeyCipherAndMac(m_userKey, m_userKey.SizeInBytes(),
MakeParameters(Name::IV(), ConstByteArrayParameter(iv,len)));
}
size_t XChaCha20Poly1305_Base::AuthenticateBlocks(const byte *data, size_t len)
{
AccessMAC().Update(data, len);
return 0;
}
void XChaCha20Poly1305_Base::AuthenticateLastHeaderBlock()
{
// Pad to a multiple of 16 or 0
const byte zero[16] = {0};
size_t pad = (16 - (m_totalHeaderLength % 16)) % 16;
AccessMAC().Update(zero, pad);
}
void XChaCha20Poly1305_Base::AuthenticateLastConfidentialBlock()
{
// Pad to a multiple of 16 or 0
const byte zero[16] = {0};
size_t pad = (16 - (m_totalMessageLength % 16)) % 16;
AccessMAC().Update(zero, pad);
}
void XChaCha20Poly1305_Base::AuthenticateLastFooterBlock(byte *mac, size_t macSize)
{
CRYPTOPP_ALIGN_DATA(8) byte length[2*sizeof(word64)];
PutWord(true, LITTLE_ENDIAN_ORDER, length+0, m_totalHeaderLength);
PutWord(true, LITTLE_ENDIAN_ORDER, length+8, m_totalMessageLength);
AccessMAC().Update(length, sizeof(length));
AccessMAC().TruncatedFinal(mac, macSize);
m_state = State_KeySet;
}
void XChaCha20Poly1305_Base::EncryptAndAuthenticate(byte *ciphertext, byte *mac, size_t macSize, const byte *iv, int ivLength, const byte *aad, size_t aadLength, const byte *message, size_t messageLength)
{
Resynchronize(iv, ivLength);
Update(aad, aadLength);
ProcessString(ciphertext, message, messageLength);
TruncatedFinal(mac, macSize);
}
bool XChaCha20Poly1305_Base::DecryptAndVerify(byte *message, const byte *mac, size_t macLength, const byte *iv, int ivLength, const byte *aad, size_t aadLength, const byte *ciphertext, size_t ciphertextLength)
{
Resynchronize(iv, ivLength);
Update(aad, aadLength);
ProcessString(message, ciphertext, ciphertextLength);
return TruncatedVerify(mac, macLength);
}
NAMESPACE_END
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