#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
{
void RatchetTagSet::DHInitialize (const uint8_t * rootKey, const uint8_t * k)
{
// DH_INITIALIZE(rootKey, k)
uint8_t keydata[64];
i2p::crypto::HKDF (rootKey, k, 32, "KDFDHRatchetStep", keydata); // keydata = HKDF(rootKey, k, "KDFDHRatchetStep", 64)
// nextRootKey = keydata[0:31]
i2p::crypto::HKDF (keydata + 32, nullptr, 0, "TagAndKeyGenKeys", m_CK);
// ck = [sessTag_ck, symmKey_ck] = HKDF(keydata[32:63], ZEROLEN, "TagAndKeyGenKeys", 64)
}
void RatchetTagSet::NextSessionTagRatchet ()
{
i2p::crypto::HKDF (m_CK, nullptr, 0, "STInitialization", m_CK); // [ck, sesstag_constant] = HKDF(sessTag_ck, ZEROLEN, "STInitialization", 64)
memcpy (m_SessTagConstant, m_CK + 32, 32);
}
const uint8_t * RatchetTagSet::GetNextSessionTag ()
{
i2p::crypto::HKDF (m_CK, m_SessTagConstant, 32, "SessionTagKeyGen", m_CK); // [ck, tag] = HKDF(sessTag_chainkey, SESSTAG_CONSTANT, "SessionTagKeyGen", 64)
return m_CK + 32;
}
ECIESX25519AEADRatchetSession::ECIESX25519AEADRatchetSession (GarlicDestination * owner):
GarlicRoutingSession (owner, true)
{
// 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::GenerateEphemeralKeysAndEncode (uint8_t * buf)
{
for (int i = 0; i < 5; i++)
{
m_EphemeralKeys.GenerateKeys ();
if (i2p::crypto::GetElligator ()->Encode (m_EphemeralKeys.GetPublicKey (), buf))
return true; // success
}
return false;
}
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)
m_State = eSessionStateNewSessionReceived;
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 (!GenerateEphemeralKeysAndEncode (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, 16); // h = SHA256(h || ciphertext)
return true;
}
bool ECIESX25519AEADRatchetSession::NewSessionReplyMessage (const uint8_t * payload, size_t len, uint8_t * out, size_t outLen)
{
// we are Bob
uint8_t tagsetKey[32];
i2p::crypto::HKDF (m_CK, nullptr, 0, "SessionReplyTags", tagsetKey, 32); // tagsetKey = HKDF(chainKey, ZEROLEN, "SessionReplyTags", 32)
// Session Tag Ratchet
RatchetTagSet tagsetNsr;
tagsetNsr.DHInitialize (m_CK, tagsetKey); // tagset_nsr = DH_INITIALIZE(chainKey, tagsetKey)
tagsetNsr.NextSessionTagRatchet ();
auto tag = tagsetNsr.GetNextSessionTag ();
size_t offset = 0;
memcpy (out + offset, tag, 8);
offset += 8;
if (!GenerateEphemeralKeysAndEncode (out + offset)) // bepk
{
LogPrint (eLogError, "Garlic: Can't encode elligator");
return false;
}
offset += 32;
// KDF for Reply Key Section
MixHash (tag, 8); // h = SHA256(h || tag)
MixHash (m_EphemeralKeys.GetPublicKey (), 32); // h = SHA256(h || bepk)
uint8_t sharedSecret[32];
m_EphemeralKeys.Agree (m_RemoteStaticKey, sharedSecret); // sharedSecret = x25519(besk, aepk)
i2p::crypto::HKDF (m_CK, sharedSecret, 32, "", m_CK); // [chainKey, key] = HKDF(chainKey, sharedSecret, "", 64)
uint8_t nonce[12];
memset (nonce, 0, 12); // n = 0
// calulate hash for zero length
if (!i2p::crypto::AEADChaCha20Poly1305 (sharedSecret /* can be anything */, 0, m_H, 32, m_CK + 32, nonce, out + offset, 16, true)) // encrypt, ciphertext = ENCRYPT(k, n, ZEROLEN, ad)
{
LogPrint (eLogWarning, "Garlic: Reply key section AEAD encryption failed");
return false;
}
MixHash (out + offset, 16); // h = SHA256(h || ciphertext)
out += 16;
// KDF for payload
uint8_t keydata[64];
i2p::crypto::HKDF (m_CK, nullptr, 0, "", keydata); // keydata = HKDF(chainKey, ZEROLEN, "", 64)
// k_ab = keydata[0:31], k_ba = keydata[32:63]
m_TagsetAB.DHInitialize (m_CK, keydata); // tagset_ab = DH_INITIALIZE(chainKey, k_ab)
m_TagsetBA.DHInitialize (m_CK, keydata + 32); // tagset_ba = DH_INITIALIZE(chainKey, k_ba)
i2p::crypto::HKDF (keydata + 32, nullptr, 0, "AttachPayloadKDF", keydata, 32); // k = HKDF(k_ba, ZEROLEN, "AttachPayloadKDF", 32)
// encrypt payload
if (!i2p::crypto::AEADChaCha20Poly1305 (payload, len, m_H, 32, keydata, nonce, out + offset, len + 16, true)) // encrypt
{
LogPrint (eLogWarning, "Garlic: Payload section AEAD encryption failed");
return false;
}
return true;
}
std::shared_ptr<I2NPMessage> ECIESX25519AEADRatchetSession::WrapSingleMessage (std::shared_ptr<const I2NPMessage> msg)
{
auto m = NewI2NPMessage ();
m->Align (12); // in order to get buf aligned to 16 (12 + 4)
uint8_t * buf = m->GetPayload () + 4; // 4 bytes for length
auto payload = CreatePayload (msg);
size_t len = payload.size ();
switch (m_State)
{
case eSessionStateNew:
if (!NewOutgoingSessionMessage (payload.data (), payload.size (), buf, m->maxLen))
return nullptr;
len += 96;
break;
case eSessionStateNewSessionReceived:
if (!NewSessionReplyMessage (payload.data (), payload.size (), buf, m->maxLen))
return nullptr;
len += 72;
break;
default:
return nullptr;
}
htobe32buf (m->GetPayload (), len);
m->len += len + 4;
m->FillI2NPMessageHeader (eI2NPGarlic);
return m;
}
std::vector<uint8_t> ECIESX25519AEADRatchetSession::CreatePayload (std::shared_ptr<const I2NPMessage> msg)
{
uint16_t cloveSize = msg->GetPayloadLength () + 9 + 1;
std::vector<uint8_t> v(cloveSize + 3);
uint8_t * payload = v.data ();
payload[0] = eECIESx25519BlkGalicClove; // clove type
htobe16buf (payload + 1, cloveSize); // size
payload[3] = 0; // flag and delivery instructions
payload[4] = msg->GetTypeID (); // I2NP msg type
htobe32buf (payload + 5, msg->GetMsgID ()); // msgID
htobe32buf (payload + 9, msg->GetExpiration ()/1000); // expiration in seconds
memcpy (payload + 13, msg->GetPayload (), msg->GetPayloadLength ());
return v;
}
}
}