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#include <string.h>
#include <openssl/sha.h>
#include "Log.h"
#include "Crypto.h"
#include "Elligator.h"
#include "Tag.h"
#include "I2PEndian.h"
#include "ECIESX25519AEADRatchetSession.h"
namespace i2p
{
namespace garlic
{
ECIESX25519AEADRatchetSession::ECIESX25519AEADRatchetSession (GarlicDestination * owner):
GarlicRoutingSession (owner, true)
{
m_EphemeralKeys.GenerateKeys ();
// TODO : use precalculated hashes
static const char protocolName[41] = "Noise_IKelg2+hs2_25519_ChaChaPoly_SHA256"; // 40 bytes
SHA256 ((const uint8_t *)protocolName, 40, m_H);
memcpy (m_CK, m_H, 32);
SHA256 (m_H, 32, m_H);
}
ECIESX25519AEADRatchetSession::~ECIESX25519AEADRatchetSession ()
{
}
void ECIESX25519AEADRatchetSession::MixHash (const uint8_t * buf, size_t len)
{
SHA256_CTX ctx;
SHA256_Init (&ctx);
SHA256_Update (&ctx, m_H, 32);
SHA256_Update (&ctx, buf, len);
SHA256_Final (m_H, &ctx);
}
bool ECIESX25519AEADRatchetSession::NewIncomingSession (const uint8_t * buf, size_t len, CloveHandler handleClove)
{
if (!GetOwner ()) return false;
// we are Bob
// KDF1
MixHash (GetOwner ()->GetEncryptionPublicKey (), 32); // h = SHA256(h || bpk)
uint8_t aepk[32]; // Alice's ephemeral key
if (!i2p::crypto::GetElligator ()->Decode (buf, aepk))
{
LogPrint (eLogError, "Garlic: Can't decode elligator");
return false;
}
buf += 32; len -= 32;
MixHash (aepk, 32); // h = SHA256(h || aepk)
uint8_t sharedSecret[32];
GetOwner ()->Decrypt (aepk, sharedSecret, nullptr); // x25519(bsk, aepk)
i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64)
// decrypt flags/static
uint8_t nonce[12], fs[32];
memset (nonce, 0, 12); // n = 0
if (!i2p::crypto::AEADChaCha20Poly1305 (buf, 32, m_H, 32, m_CK + 32, nonce, fs, 32, false)) // decrypt
{
LogPrint (eLogWarning, "Garlic: Flags/static section AEAD verification failed ");
return false;
}
MixHash (buf, 48); // h = SHA256(h || ciphertext)
buf += 48; len -= 48; // 32 data + 16 poly
// decrypt payload
std::vector<uint8_t> payload (len - 16);
// KDF2 for payload
bool isStatic = !i2p::data::Tag<32> (fs).IsZero ();
if (isStatic)
{
// static key, fs is apk
memcpy (m_RemoteStaticKey, fs, 32);
GetOwner ()->Decrypt (fs, sharedSecret, nullptr); // x25519(bsk, apk)
i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64)
}
else // all zeros flags
htole64buf (nonce + 4, 1); // n = 1
if (!i2p::crypto::AEADChaCha20Poly1305 (buf, len - 16, m_H, 32, m_CK + 32, nonce, payload.data (), len - 16, false)) // decrypt
{
LogPrint (eLogWarning, "Garlic: Payload section AEAD verification failed");
return false;
}
if (isStatic) MixHash (buf, len); // h = SHA256(h || ciphertext)
HandlePayload (payload.data (), len - 16, handleClove);
return true;
}
void ECIESX25519AEADRatchetSession::HandlePayload (const uint8_t * buf, size_t len, CloveHandler& handleClove)
{
size_t offset = 0;
while (offset < len)
{
uint8_t blk = buf[offset];
offset++;
auto size = bufbe16toh (buf + offset);
offset += 2;
LogPrint (eLogDebug, "Garlic: Block type ", (int)blk, " of size ", size);
if (size > len)
{
LogPrint (eLogError, "Garlic: Unexpected block length ", size);
break;
}
switch (blk)
{
case eECIESx25519BlkGalicClove:
handleClove (buf + offset, size);
break;
case eECIESx25519BlkDateTime:
LogPrint (eLogDebug, "Garlic: datetime");
break;
case eECIESx25519BlkOptions:
LogPrint (eLogDebug, "Garlic: options");
break;
case eECIESx25519BlkPadding:
LogPrint (eLogDebug, "Garlic: padding");
break;
default:
LogPrint (eLogWarning, "Garlic: Unknown block type ", (int)blk);
}
offset += size;
}
}
bool ECIESX25519AEADRatchetSession::NewOutgoingSessionMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen)
{
// we are Alice, bpk is m_RemoteStaticKey
size_t offset = 0;
if (!i2p::crypto::GetElligator ()->Encode (m_EphemeralKeys.GetPublicKey (), out + offset))
{
LogPrint (eLogError, "Garlic: Can't encode elligator");
return false;
}
offset += 32;
// KDF1
MixHash (m_RemoteStaticKey, 32); // h = SHA256(h || bpk)
MixHash (m_EphemeralKeys.GetPublicKey (), 32); // h = SHA256(h || aepk)
uint8_t sharedSecret[32];
m_EphemeralKeys.Agree (m_RemoteStaticKey, nullptr); // x25519(aesk, bpk)
i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64)
// encrypt static key section
uint8_t nonce[12];
memset (nonce, 0, 12); // n = 0
if (!i2p::crypto::AEADChaCha20Poly1305 (GetOwner ()->GetEncryptionPublicKey (), 32, m_H, 32, m_CK + 32, nonce, out + offset, 48, true)) // encrypt
{
LogPrint (eLogWarning, "Garlic: Static section AEAD encryption failed ");
return false;
}
MixHash (out + offset, 48); // h = SHA256(h || ciphertext)
offset += 48;
// KDF2
GetOwner ()->Decrypt (m_RemoteStaticKey, sharedSecret, nullptr); // x25519 (ask, bpk)
i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64)
// encrypt payload
if (!i2p::crypto::AEADChaCha20Poly1305 (payload, len, m_H, 32, m_CK + 32, nonce, out + offset, len + 16, true)) // encrypt
{
LogPrint (eLogWarning, "Garlic: Payload section AEAD encryption failed");
return false;
}
MixHash (out + offset, len + 16); // h = SHA256(h || ciphertext)
return true;
}
std::shared_ptr<I2NPMessage> ECIESX25519AEADRatchetSession::WrapSingleMessage (std::shared_ptr<const I2NPMessage> msg)
{
// TODO:
return nullptr;
}
}
}