I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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/*
* Copyright (c) 2013-2021, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/
#include <zlib.h> // for crc32
#include <openssl/sha.h>
#include <openssl/hmac.h>
#include <openssl/ec.h>
#include <openssl/bn.h>
#include "Base.h"
#include "Crypto.h"
#include "Log.h"
#include "Timestamp.h"
#include "I2PEndian.h"
#include "Ed25519.h"
#include "Signature.h"
#include "Blinding.h"
namespace i2p
{
namespace data
{
static EC_POINT * BlindPublicKeyECDSA (const EC_GROUP * group, const EC_POINT * pub, const uint8_t * seed)
{
BN_CTX * ctx = BN_CTX_new ();
BN_CTX_start (ctx);
BIGNUM * q = BN_CTX_get (ctx);
EC_GROUP_get_order (group, q, ctx);
// calculate alpha = seed mod q
BIGNUM * alpha = BN_CTX_get (ctx);
BN_bin2bn (seed, 64, alpha); // seed is in BigEndian
BN_mod (alpha, alpha, q, ctx); // % q
// A' = BLIND_PUBKEY(A, alpha) = A + DERIVE_PUBLIC(alpha)
auto p = EC_POINT_new (group);
EC_POINT_mul (group, p, alpha, nullptr, nullptr, ctx); // B*alpha
EC_POINT_add (group, p, pub, p, ctx); // pub + B*alpha
BN_CTX_end (ctx);
BN_CTX_free (ctx);
return p;
}
static void BlindPrivateKeyECDSA (const EC_GROUP * group, const BIGNUM * priv, const uint8_t * seed, BIGNUM * blindedPriv)
{
BN_CTX * ctx = BN_CTX_new ();
BN_CTX_start (ctx);
BIGNUM * q = BN_CTX_get (ctx);
EC_GROUP_get_order (group, q, ctx);
// calculate alpha = seed mod q
BIGNUM * alpha = BN_CTX_get (ctx);
BN_bin2bn (seed, 64, alpha); // seed is in BigEndian
BN_mod (alpha, alpha, q, ctx); // % q
BN_add (alpha, alpha, priv); // alpha = alpha + priv
// a' = BLIND_PRIVKEY(a, alpha) = (a + alpha) mod q
BN_mod (blindedPriv, alpha, q, ctx); // % q
BN_CTX_end (ctx);
BN_CTX_free (ctx);
}
static void BlindEncodedPublicKeyECDSA (size_t publicKeyLen, const EC_GROUP * group, const uint8_t * pub, const uint8_t * seed, uint8_t * blindedPub)
{
BIGNUM * x = BN_bin2bn (pub, publicKeyLen/2, NULL);
BIGNUM * y = BN_bin2bn (pub + publicKeyLen/2, publicKeyLen/2, NULL);
EC_POINT * p = EC_POINT_new (group);
EC_POINT_set_affine_coordinates_GFp (group, p, x, y, NULL);
EC_POINT * p1 = BlindPublicKeyECDSA (group, p, seed);
EC_POINT_free (p);
EC_POINT_get_affine_coordinates_GFp (group, p1, x, y, NULL);
EC_POINT_free (p1);
i2p::crypto::bn2buf (x, blindedPub, publicKeyLen/2);
i2p::crypto::bn2buf (y, blindedPub + publicKeyLen/2, publicKeyLen/2);
BN_free (x); BN_free (y);
}
static void BlindEncodedPrivateKeyECDSA (size_t publicKeyLen, const EC_GROUP * group, const uint8_t * priv, const uint8_t * seed, uint8_t * blindedPriv, uint8_t * blindedPub)
{
BIGNUM * a = BN_bin2bn (priv, publicKeyLen/2, NULL);
BIGNUM * a1 = BN_new ();
BlindPrivateKeyECDSA (group, a, seed, a1);
BN_free (a);
i2p::crypto::bn2buf (a1, blindedPriv, publicKeyLen/2);
auto p = EC_POINT_new (group);
BN_CTX * ctx = BN_CTX_new ();
EC_POINT_mul (group, p, a1, nullptr, nullptr, ctx); // B*a1
BN_CTX_free (ctx);
BN_free (a1);
BIGNUM * x = BN_new(), * y = BN_new();
EC_POINT_get_affine_coordinates_GFp (group, p, x, y, NULL);
EC_POINT_free (p);
i2p::crypto::bn2buf (x, blindedPub, publicKeyLen/2);
i2p::crypto::bn2buf (y, blindedPub + publicKeyLen/2, publicKeyLen/2);
BN_free (x); BN_free (y);
}
template<typename Fn, typename...Args>
static size_t BlindECDSA (i2p::data::SigningKeyType sigType, const uint8_t * key, const uint8_t * seed, Fn blind, Args&&...args)
// blind is BlindEncodedPublicKeyECDSA or BlindEncodedPrivateKeyECDSA
{
size_t publicKeyLength = 0;
EC_GROUP * group = nullptr;
switch (sigType)
{
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA256_P256:
{
publicKeyLength = i2p::crypto::ECDSAP256_KEY_LENGTH;
group = EC_GROUP_new_by_curve_name (NID_X9_62_prime256v1);
break;
}
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA384_P384:
{
publicKeyLength = i2p::crypto::ECDSAP384_KEY_LENGTH;
group = EC_GROUP_new_by_curve_name (NID_secp384r1);
break;
}
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA512_P521:
{
publicKeyLength = i2p::crypto::ECDSAP521_KEY_LENGTH;
group = EC_GROUP_new_by_curve_name (NID_secp521r1);
break;
}
default:
LogPrint (eLogError, "Blinding: signature type ", (int)sigType, " is not ECDSA");
}
if (group)
{
blind (publicKeyLength, group, key, seed, std::forward<Args>(args)...);
EC_GROUP_free (group);
}
return publicKeyLength;
}
//----------------------------------------------------------
const uint8_t B33_TWO_BYTES_SIGTYPE_FLAG = 0x01;
const uint8_t B33_PER_SECRET_FLAG = 0x02; // not used for now
const uint8_t B33_PER_CLIENT_AUTH_FLAG = 0x04;
BlindedPublicKey::BlindedPublicKey (std::shared_ptr<const IdentityEx> identity, bool clientAuth):
m_IsClientAuth (clientAuth)
{
if (!identity) return;
auto len = identity->GetSigningPublicKeyLen ();
m_PublicKey.resize (len);
memcpy (m_PublicKey.data (), identity->GetSigningPublicKeyBuffer (), len);
m_SigType = identity->GetSigningKeyType ();
m_BlindedSigType = m_SigType;
}
BlindedPublicKey::BlindedPublicKey (const std::string& b33):
m_SigType (0) // 0 means invalid, we can't blind DSA, set it later
{
uint8_t addr[40]; // TODO: define length from b33
size_t l = i2p::data::Base32ToByteStream (b33.c_str (), b33.length (), addr, 40);
if (l < 32)
{
LogPrint (eLogError, "Blinding: malformed b33 ", b33);
return;
}
uint32_t checksum = crc32 (0, addr + 3, l - 3);
// checksum is Little Endian
addr[0] ^= checksum; addr[1] ^= (checksum >> 8); addr[2] ^= (checksum >> 16);
uint8_t flags = addr[0];
size_t offset = 1;
if (flags & B33_TWO_BYTES_SIGTYPE_FLAG) // two bytes signatures
{
m_SigType = bufbe16toh (addr + offset); offset += 2;
m_BlindedSigType = bufbe16toh (addr + offset); offset += 2;
}
else // one byte sig
{
m_SigType = addr[offset]; offset++;
m_BlindedSigType = addr[offset]; offset++;
}
m_IsClientAuth = flags & B33_PER_CLIENT_AUTH_FLAG;
std::unique_ptr<i2p::crypto::Verifier> blindedVerifier (i2p::data::IdentityEx::CreateVerifier (m_SigType));
if (blindedVerifier)
{
auto len = blindedVerifier->GetPublicKeyLen ();
if (offset + len <= l)
{
m_PublicKey.resize (len);
memcpy (m_PublicKey.data (), addr + offset, len);
}
else
LogPrint (eLogError, "Blinding: public key in b33 address is too short for signature type ", (int)m_SigType);
}
else
LogPrint (eLogError, "Blinding: unknown signature type ", (int)m_SigType, " in b33");
}
std::string BlindedPublicKey::ToB33 () const
{
if (m_PublicKey.size () > 32) return ""; // assume 25519
uint8_t addr[35]; char str[60]; // TODO: define actual length
uint8_t flags = 0;
if (m_IsClientAuth) flags |= B33_PER_CLIENT_AUTH_FLAG;
addr[0] = flags; // flags
addr[1] = m_SigType; // sig type
addr[2] = m_BlindedSigType; // blinded sig type
memcpy (addr + 3, m_PublicKey.data (), m_PublicKey.size ());
uint32_t checksum = crc32 (0, addr + 3, m_PublicKey.size ());
// checksum is Little Endian
addr[0] ^= checksum; addr[1] ^= (checksum >> 8); addr[2] ^= (checksum >> 16);
auto l = ByteStreamToBase32 (addr, m_PublicKey.size () + 3, str, 60);
return std::string (str, str + l);
}
void BlindedPublicKey::GetCredential (uint8_t * credential) const
{
// A = destination's signing public key
// stA = signature type of A, 2 bytes big endian
uint16_t stA = htobe16 (GetSigType ());
// stA1 = signature type of blinded A, 2 bytes big endian
uint16_t stA1 = htobe16 (GetBlindedSigType ());
// credential = H("credential", A || stA || stA1)
H ("credential", { {GetPublicKey (), GetPublicKeyLen ()}, {(const uint8_t *)&stA, 2}, {(const uint8_t *)&stA1, 2} }, credential);
}
void BlindedPublicKey::GetSubcredential (const uint8_t * blinded, size_t len, uint8_t * subcredential) const
{
uint8_t credential[32];
GetCredential (credential);
// subcredential = H("subcredential", credential || blindedPublicKey)
H ("subcredential", { {credential, 32}, {blinded, len} }, subcredential);
}
void BlindedPublicKey::GenerateAlpha (const char * date, uint8_t * seed) const
{
uint16_t stA = htobe16 (GetSigType ()), stA1 = htobe16 (GetBlindedSigType ());
uint8_t salt[32];
//seed = HKDF(H("I2PGenerateAlpha", keydata), datestring || secret, "i2pblinding1", 64)
H ("I2PGenerateAlpha", { {GetPublicKey (), GetPublicKeyLen ()}, {(const uint8_t *)&stA, 2}, {(const uint8_t *)&stA1, 2} }, salt);
i2p::crypto::HKDF (salt, (const uint8_t *)date, 8, "i2pblinding1", seed);
}
size_t BlindedPublicKey::GetBlindedKey (const char * date, uint8_t * blindedKey) const
{
uint8_t seed[64];
GenerateAlpha (date, seed);
size_t publicKeyLength = 0;
switch (m_SigType)
{
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA256_P256:
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA384_P384:
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA512_P521:
publicKeyLength = BlindECDSA (m_SigType, GetPublicKey (), seed, BlindEncodedPublicKeyECDSA, blindedKey);
break;
case i2p::data::SIGNING_KEY_TYPE_REDDSA_SHA512_ED25519:
case i2p::data::SIGNING_KEY_TYPE_EDDSA_SHA512_ED25519:
i2p::crypto::GetEd25519 ()->BlindPublicKey (GetPublicKey (), seed, blindedKey);
publicKeyLength = i2p::crypto::EDDSA25519_PUBLIC_KEY_LENGTH;
break;
default:
LogPrint (eLogError, "Blinding: can't blind signature type ", (int)m_SigType);
}
return publicKeyLength;
}
size_t BlindedPublicKey::BlindPrivateKey (const uint8_t * priv, const char * date, uint8_t * blindedPriv, uint8_t * blindedPub) const
{
uint8_t seed[64];
GenerateAlpha (date, seed);
size_t publicKeyLength = 0;
switch (m_SigType)
{
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA256_P256:
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA384_P384:
case i2p::data::SIGNING_KEY_TYPE_ECDSA_SHA512_P521:
publicKeyLength = BlindECDSA (m_SigType, priv, seed, BlindEncodedPrivateKeyECDSA, blindedPriv, blindedPub);
break;
case i2p::data::SIGNING_KEY_TYPE_REDDSA_SHA512_ED25519:
i2p::crypto::GetEd25519 ()->BlindPrivateKey (priv, seed, blindedPriv, blindedPub);
publicKeyLength = i2p::crypto::EDDSA25519_PUBLIC_KEY_LENGTH;
break;
case i2p::data::SIGNING_KEY_TYPE_EDDSA_SHA512_ED25519:
{
uint8_t exp[64];
i2p::crypto::Ed25519::ExpandPrivateKey (priv, exp);
i2p::crypto::GetEd25519 ()->BlindPrivateKey (exp, seed, blindedPriv, blindedPub);
publicKeyLength = i2p::crypto::EDDSA25519_PUBLIC_KEY_LENGTH;
break;
}
default:
LogPrint (eLogError, "Blinding: can't blind signature type ", (int)m_SigType);
}
return publicKeyLength;
}
void BlindedPublicKey::H (const std::string& p, const std::vector<std::pair<const uint8_t *, size_t> >& bufs, uint8_t * hash) const
{
SHA256_CTX ctx;
SHA256_Init (&ctx);
SHA256_Update (&ctx, p.c_str (), p.length ());
for (const auto& it: bufs)
SHA256_Update (&ctx, it.first, it.second);
SHA256_Final (hash, &ctx);
}
i2p::data::IdentHash BlindedPublicKey::GetStoreHash (const char * date) const
{
i2p::data::IdentHash hash;
uint8_t blinded[128];
size_t publicKeyLength = 0;
if (date)
publicKeyLength = GetBlindedKey (date, blinded);
else
{
char currentDate[9];
i2p::util::GetCurrentDate (currentDate);
publicKeyLength = GetBlindedKey (currentDate, blinded);
}
if (publicKeyLength)
{
auto stA1 = htobe16 (m_BlindedSigType);
SHA256_CTX ctx;
SHA256_Init (&ctx);
SHA256_Update (&ctx, (const uint8_t *)&stA1, 2);
SHA256_Update (&ctx, blinded, publicKeyLength);
SHA256_Final ((uint8_t *)hash, &ctx);
}
else
LogPrint (eLogError, "Blinding: blinded key type ", (int)m_BlindedSigType, " is not supported");
return hash;
}
}
}