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/*
* SM2 Signatures
* (C) 2017,2018 Ribose Inc
* (C) 2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/sm2.h>
#include <botan/internal/pk_ops_impl.h>
#include <botan/internal/point_mul.h>
#include <botan/loadstor.h>
#include <botan/numthry.h>
#include <botan/keypair.h>
#include <botan/hash.h>
#include <botan/parsing.h>
namespace Botan {
std::string SM2_PublicKey::algo_name() const
{
return "SM2";
}
bool SM2_PrivateKey::check_key(RandomNumberGenerator& rng,
bool strong) const
{
if(!public_point().on_the_curve())
return false;
if(!strong)
return true;
return KeyPair::signature_consistency_check(rng, *this, "user@example.com,SM3");
}
SM2_PrivateKey::SM2_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<uint8_t>& key_bits) :
EC_PrivateKey(alg_id, key_bits)
{
m_da_inv = domain().inverse_mod_order(m_private_key + 1);
}
SM2_PrivateKey::SM2_PrivateKey(RandomNumberGenerator& rng,
const EC_Group& domain,
const BigInt& x) :
EC_PrivateKey(rng, domain, x)
{
m_da_inv = domain.inverse_mod_order(m_private_key + 1);
}
std::vector<uint8_t> sm2_compute_za(HashFunction& hash,
const std::string& user_id,
const EC_Group& domain,
const PointGFp& pubkey)
{
if(user_id.size() >= 8192)
throw Invalid_Argument("SM2 user id too long to represent");
const uint16_t uid_len = static_cast<uint16_t>(8 * user_id.size());
hash.update(get_byte(0, uid_len));
hash.update(get_byte(1, uid_len));
hash.update(user_id);
const size_t p_bytes = domain.get_p_bytes();
hash.update(BigInt::encode_1363(domain.get_a(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_b(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_g_x(), p_bytes));
hash.update(BigInt::encode_1363(domain.get_g_y(), p_bytes));
hash.update(BigInt::encode_1363(pubkey.get_affine_x(), p_bytes));
hash.update(BigInt::encode_1363(pubkey.get_affine_y(), p_bytes));
std::vector<uint8_t> za(hash.output_length());
hash.final(za.data());
return za;
}
namespace {
/**
* SM2 signature operation
*/
class SM2_Signature_Operation final : public PK_Ops::Signature
{
public:
SM2_Signature_Operation(const SM2_PrivateKey& sm2,
const std::string& ident,
const std::string& hash) :
m_group(sm2.domain()),
m_x(sm2.private_value()),
m_da_inv(sm2.get_da_inv())
{
if(hash == "Raw")
{
// m_hash is null, m_za is empty
}
else
{
m_hash = HashFunction::create_or_throw(hash);
// ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)
m_za = sm2_compute_za(*m_hash, ident, m_group, sm2.public_point());
m_hash->update(m_za);
}
}
size_t signature_length() const override { return 2*m_group.get_order_bytes(); }
void update(const uint8_t msg[], size_t msg_len) override
{
if(m_hash)
{
m_hash->update(msg, msg_len);
}
else
{
m_digest.insert(m_digest.end(), msg, msg + msg_len);
}
}
secure_vector<uint8_t> sign(RandomNumberGenerator& rng) override;
private:
const EC_Group m_group;
const BigInt& m_x;
const BigInt& m_da_inv;
std::vector<uint8_t> m_za;
secure_vector<uint8_t> m_digest;
std::unique_ptr<HashFunction> m_hash;
std::vector<BigInt> m_ws;
};
secure_vector<uint8_t>
SM2_Signature_Operation::sign(RandomNumberGenerator& rng)
{
BigInt e;
if(m_hash)
{
e = BigInt::decode(m_hash->final());
// prepend ZA for next signature if any
m_hash->update(m_za);
}
else
{
e = BigInt::decode(m_digest);
m_digest.clear();
}
const BigInt k = m_group.random_scalar(rng);
const BigInt r = m_group.mod_order(
m_group.blinded_base_point_multiply_x(k, rng, m_ws) + e);
const BigInt s = m_group.multiply_mod_order(m_da_inv, m_group.mod_order(k - r*m_x));
return BigInt::encode_fixed_length_int_pair(r, s, m_group.get_order().bytes());
}
/**
* SM2 verification operation
*/
class SM2_Verification_Operation final : public PK_Ops::Verification
{
public:
SM2_Verification_Operation(const SM2_PublicKey& sm2,
const std::string& ident,
const std::string& hash) :
m_group(sm2.domain()),
m_gy_mul(m_group.get_base_point(), sm2.public_point())
{
if(hash == "Raw")
{
// m_hash is null, m_za is empty
}
else
{
m_hash = HashFunction::create_or_throw(hash);
// ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)
m_za = sm2_compute_za(*m_hash, ident, m_group, sm2.public_point());
m_hash->update(m_za);
}
}
void update(const uint8_t msg[], size_t msg_len) override
{
if(m_hash)
{
m_hash->update(msg, msg_len);
}
else
{
m_digest.insert(m_digest.end(), msg, msg + msg_len);
}
}
bool is_valid_signature(const uint8_t sig[], size_t sig_len) override;
private:
const EC_Group m_group;
const PointGFp_Multi_Point_Precompute m_gy_mul;
secure_vector<uint8_t> m_digest;
std::vector<uint8_t> m_za;
std::unique_ptr<HashFunction> m_hash;
};
bool SM2_Verification_Operation::is_valid_signature(const uint8_t sig[], size_t sig_len)
{
BigInt e;
if(m_hash)
{
e = BigInt::decode(m_hash->final());
// prepend ZA for next signature if any
m_hash->update(m_za);
}
else
{
e = BigInt::decode(m_digest);
m_digest.clear();
}
if(sig_len != m_group.get_order().bytes()*2)
return false;
const BigInt r(sig, sig_len / 2);
const BigInt s(sig + sig_len / 2, sig_len / 2);
if(r <= 0 || r >= m_group.get_order() || s <= 0 || s >= m_group.get_order())
return false;
const BigInt t = m_group.mod_order(r + s);
if(t == 0)
return false;
const PointGFp R = m_gy_mul.multi_exp(s, t);
// ???
if(R.is_zero())
return false;
return (m_group.mod_order(R.get_affine_x() + e) == r);
}
void parse_sm2_param_string(const std::string& params,
std::string& userid,
std::string& hash)
{
// GM/T 0009-2012 specifies this as the default userid
const std::string default_userid = "1234567812345678";
// defaults:
userid = default_userid;
hash = "SM3";
/*
* SM2 parameters have the following possible formats:
* Ident [since 2.2.0]
* Ident,Hash [since 2.3.0]
*/
auto comma = params.find(',');
if(comma == std::string::npos)
{
userid = params;
}
else
{
userid = params.substr(0, comma);
hash = params.substr(comma+1, std::string::npos);
}
}
}
std::unique_ptr<PK_Ops::Verification>
SM2_PublicKey::create_verification_op(const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
{
std::string userid, hash;
parse_sm2_param_string(params, userid, hash);
return std::unique_ptr<PK_Ops::Verification>(new SM2_Verification_Operation(*this, userid, hash));
}
throw Provider_Not_Found(algo_name(), provider);
}
std::unique_ptr<PK_Ops::Signature>
SM2_PrivateKey::create_signature_op(RandomNumberGenerator& /*rng*/,
const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
{
std::string userid, hash;
parse_sm2_param_string(params, userid, hash);
return std::unique_ptr<PK_Ops::Signature>(new SM2_Signature_Operation(*this, userid, hash));
}
throw Provider_Not_Found(algo_name(), provider);
}
}