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Diffstat (limited to 'src/lib/pubkey/ecies/ecies.cpp')
| -rw-r--r-- | src/lib/pubkey/ecies/ecies.cpp | 398 |
1 files changed, 398 insertions, 0 deletions
diff --git a/src/lib/pubkey/ecies/ecies.cpp b/src/lib/pubkey/ecies/ecies.cpp new file mode 100644 index 000000000..d44d14803 --- /dev/null +++ b/src/lib/pubkey/ecies/ecies.cpp @@ -0,0 +1,398 @@ +/* +* ECIES +* (C) 2016 Philipp Weber +* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity +* +* Botan is released under the Simplified BSD License (see license.txt) +*/ + +#include <botan/ecies.h> +#include <botan/cipher_mode.h> + +#include <botan/internal/ct_utils.h> +#include <botan/internal/pk_utils.h> + +namespace Botan { + +namespace { + +/** +* Private key type for ECIES_ECDH_KA_Operation +*/ +class ECIES_PrivateKey : public EC_PrivateKey, public PK_Key_Agreement_Key + { + public: + explicit ECIES_PrivateKey(const ECDH_PrivateKey& private_key) : + EC_PublicKey(private_key), + EC_PrivateKey(private_key), + PK_Key_Agreement_Key(), + m_key(private_key) + { + } + + std::vector<byte> public_value() const override + { + return m_key.public_value(); + } + + std::string algo_name() const override + { + return "ECIES"; + } + + size_t max_input_bits() const override + { + return m_key.max_input_bits(); + } + + private: + ECDH_PrivateKey m_key; + }; + +/** +* Implements ECDH key agreement without using the cofactor mode +*/ +class ECIES_ECDH_KA_Operation : public PK_Ops::Key_Agreement_with_KDF + { + public: + typedef ECIES_PrivateKey Key_Type; + + ECIES_ECDH_KA_Operation(const ECIES_PrivateKey& private_key, const std::string&) : + PK_Ops::Key_Agreement_with_KDF("Raw"), + m_key(private_key) + { + } + + secure_vector<byte> raw_agree(const byte w[], size_t w_len) override + { + const CurveGFp& curve = m_key.domain().get_curve(); + PointGFp point = OS2ECP(w, w_len, curve); + PointGFp S = point * m_key.private_value(); + BOTAN_ASSERT(S.on_the_curve(), "ECDH agreed value was on the curve"); + return BigInt::encode_1363(S.get_affine_x(), curve.get_p().bytes()); + } + + private: + ECIES_PrivateKey m_key; + }; + +/** +* Creates a PK_Key_Agreement instance for the given key and ecies_params +* Returns either ECIES_ECDH_KA_Operation or the default implementation for the given key, +* depending on the key and ecies_params +* @param private_key the private key used for the key agreement +* @param ecies_params settings for ecies +* @param for_encryption disable cofactor mode if the secret will be used for encryption +* (according to ISO 18033 cofactor mode is only used during decryption) +*/ +PK_Key_Agreement create_key_agreement(const PK_Key_Agreement_Key& private_key, const ECIES_KA_Params& ecies_params, + bool for_encryption) + { + const ECDH_PrivateKey* ecdh_key = dynamic_cast<const ECDH_PrivateKey*>(&private_key); + + if(ecdh_key == nullptr && (ecies_params.cofactor_mode() || ecies_params.old_cofactor_mode() + || ecies_params.check_mode())) + { + // assume we have a private key from an external provider (e.g. pkcs#11): + // there is no way to determine or control whether the provider uses cofactor mode or not. + // ISO 18033 does not allow cofactor mode in combination with old cofactor mode or check mode + // => disable cofactor mode, old cofactor mode and check mode for unknown keys/providers (as a precaution). + throw Invalid_Argument("ECIES: cofactor, old cofactor and check mode are only supported for ECDH_PrivateKey"); + } + + if(ecdh_key && (for_encryption || !ecies_params.cofactor_mode())) + { + // ECDH_KA_Operation uses cofactor mode: use own key agreement method if cofactor should not be used. + return PK_Key_Agreement(ECIES_PrivateKey(*ecdh_key), "Raw"); + } + + return PK_Key_Agreement(private_key, "Raw"); // use default implementation + } +} + +BOTAN_REGISTER_PK_KEY_AGREE_OP("ECIES", ECIES_ECDH_KA_Operation); + +ECIES_KA_Operation::ECIES_KA_Operation(const PK_Key_Agreement_Key& private_key, const ECIES_KA_Params& ecies_params, + bool for_encryption) : + m_ka(create_key_agreement(private_key, ecies_params, for_encryption)), + m_params(ecies_params) + { + } + +/** +* ECIES secret derivation according to ISO 18033-2 +*/ +SymmetricKey ECIES_KA_Operation::derive_secret(const std::vector<byte>& eph_public_key_bin, + const PointGFp& other_public_key_point) const + { + if(other_public_key_point.is_zero()) + { + throw Invalid_Argument("ECIES: other public key point is zero"); + } + + std::unique_ptr<KDF> kdf = m_params.create_kdf(); + BOTAN_ASSERT(kdf != nullptr, "KDF is found"); + + PointGFp other_point = other_public_key_point; + + // ISO 18033: step b + if(m_params.old_cofactor_mode()) + { + other_point *= m_params.domain().get_cofactor(); + } + + secure_vector<byte> derivation_input; + + // ISO 18033: encryption step e / decryption step g + if(!m_params.single_hash_mode()) + { + derivation_input += eph_public_key_bin; + } + + // ISO 18033: encryption step f / decryption step h + secure_vector<byte> other_public_key_bin = EC2OSP(other_point, static_cast<byte>(m_params.compression_type())); + // Note: the argument `m_params.secret_length()` passed for `key_len` will only be used by providers because + // "Raw" is passed to the `PK_Key_Agreement` if the implementation of botan is used. + const SymmetricKey peh = m_ka.derive_key(m_params.domain().get_order().bytes(), other_public_key_bin.data(), other_public_key_bin.size()); + derivation_input.insert(derivation_input.end(), peh.begin(), peh.end()); + + // ISO 18033: encryption step g / decryption step i + return kdf->derive_key(m_params.secret_length(), derivation_input); + } + + +ECIES_KA_Params::ECIES_KA_Params(const EC_Group& domain, const std::string& kdf_spec, size_t length, + PointGFp::Compression_Type compression_type, ECIES_Flags flags) : + m_domain(domain), + m_kdf_spec(kdf_spec), + m_length(length), + m_compression_mode(compression_type), + m_flags(flags) + { + } + +std::unique_ptr<KDF> ECIES_KA_Params::create_kdf() const + { + std::unique_ptr<KDF> kdf = Botan::KDF::create(m_kdf_spec); + if(kdf == nullptr) + { + throw Algorithm_Not_Found(m_kdf_spec); + } + return kdf; + } + + +ECIES_System_Params::ECIES_System_Params(const EC_Group& domain, const std::string& kdf_spec, + const std::string& dem_algo_spec, size_t dem_key_len, + const std::string& mac_spec, size_t mac_key_len, + PointGFp::Compression_Type compression_type, ECIES_Flags flags) : + ECIES_KA_Params(domain, kdf_spec, dem_key_len + mac_key_len, compression_type, flags), + m_dem_spec(dem_algo_spec), + m_dem_keylen(dem_key_len), + m_mac_spec(mac_spec), + m_mac_keylen(mac_key_len) + { + // ISO 18033: "At most one of CofactorMode, OldCofactorMode, and CheckMode may be 1." + if(cofactor_mode() + old_cofactor_mode() + check_mode() > 1) + { + throw Invalid_Argument("ECIES: only one of cofactor_mode, old_cofactor_mode and check_mode can be set"); + } + } + +ECIES_System_Params::ECIES_System_Params(const EC_Group& domain, const std::string& kdf_spec, + const std::string& dem_algo_spec, size_t dem_key_len, + const std::string& mac_spec, size_t mac_key_len) : + ECIES_System_Params(domain, kdf_spec, dem_algo_spec, dem_key_len, mac_spec, mac_key_len, PointGFp::UNCOMPRESSED, + ECIES_Flags::NONE) + { + } + +std::unique_ptr<MessageAuthenticationCode> ECIES_System_Params::create_mac() const + { + std::unique_ptr<MessageAuthenticationCode> mac = Botan::MessageAuthenticationCode::create(m_mac_spec); + if(mac == nullptr) + { + throw Algorithm_Not_Found(m_mac_spec); + } + return mac; + } + +std::unique_ptr<Cipher_Mode> ECIES_System_Params::create_cipher(Botan::Cipher_Dir direction) const + { + Cipher_Mode* cipher = get_cipher_mode(m_dem_spec, direction); + if(cipher == nullptr) + { + throw Algorithm_Not_Found(m_dem_spec); + } + return std::unique_ptr<Cipher_Mode>(cipher); + } + + +/* +* ECIES_Encryptor Constructor +*/ +ECIES_Encryptor::ECIES_Encryptor(const PK_Key_Agreement_Key& private_key, const ECIES_System_Params& ecies_params) : + m_ka(private_key, ecies_params, true), + m_params(ecies_params), + m_eph_public_key_bin(private_key.public_value()), // returns the uncompressed public key, see conversion below + m_iv(), + m_other_point(), + m_label() + { + if(ecies_params.compression_type() != PointGFp::UNCOMPRESSED) + { + // ISO 18033: step d + // convert only if necessary; m_eph_public_key_bin has been initialized with the uncompressed format + m_eph_public_key_bin = unlock(EC2OSP(OS2ECP(m_eph_public_key_bin, m_params.domain().get_curve()), + static_cast<byte>(ecies_params.compression_type()))); + } + } + +/* +* ECIES_Encryptor Constructor +*/ +ECIES_Encryptor::ECIES_Encryptor(RandomNumberGenerator& rng, const ECIES_System_Params& ecies_params) : + ECIES_Encryptor(ECDH_PrivateKey(rng, ecies_params.domain()), ecies_params) + { + } + + +/* +* ECIES Encryption according to ISO 18033-2 +*/ +std::vector<byte> ECIES_Encryptor::enc(const byte data[], size_t length, RandomNumberGenerator&) const + { + if(m_other_point.is_zero()) + { + throw Invalid_State("ECIES: the other key is zero"); + } + + const SymmetricKey secret_key = m_ka.derive_secret(m_eph_public_key_bin, m_other_point); + + // encryption + std::unique_ptr<Cipher_Mode> cipher = m_params.create_cipher(ENCRYPTION); + BOTAN_ASSERT(cipher != nullptr, "Cipher is found"); + + cipher->set_key(SymmetricKey(secret_key.begin(), m_params.dem_keylen())); + if(m_iv.size() != 0) + { + cipher->start(m_iv.bits_of()); + } + secure_vector<byte> encrypted_data(data, data + length); + cipher->finish(encrypted_data); + + // concat elements + std::unique_ptr<MessageAuthenticationCode> mac = m_params.create_mac(); + BOTAN_ASSERT(mac != nullptr, "MAC is found"); + + secure_vector<byte> out(m_eph_public_key_bin.size() + encrypted_data.size() + mac->output_length()); + buffer_insert(out, 0, m_eph_public_key_bin); + buffer_insert(out, m_eph_public_key_bin.size(), encrypted_data); + + // mac + mac->set_key(secret_key.begin() + m_params.dem_keylen(), m_params.mac_keylen()); + mac->update(encrypted_data); + if(!m_label.empty()) + { + mac->update(m_label); + } + mac->final(out.data() + m_eph_public_key_bin.size() + encrypted_data.size()); + + return unlock(out); + } + + +ECIES_Decryptor::ECIES_Decryptor(const PK_Key_Agreement_Key& key, const ECIES_System_Params& ecies_params) : + m_ka(key, ecies_params, false), + m_params(ecies_params), + m_iv(), + m_label() + { + // ISO 18033: "If v > 1 and CheckMode = 0, then we must have gcd(u, v) = 1." (v = index, u= order) + if(!ecies_params.check_mode()) + { + Botan::BigInt cofactor = m_params.domain().get_cofactor(); + if(cofactor > 1 && Botan::gcd(cofactor, m_params.domain().get_order()) != 1) + { + throw Invalid_Argument("ECIES: gcd of cofactor and order must be 1 if check_mode is 0"); + } + } + } + +/** +* ECIES Decryption according to ISO 18033-2 +*/ +secure_vector<byte> ECIES_Decryptor::do_decrypt(byte& valid_mask, const byte in[], size_t in_len) const + { + size_t point_size = m_params.domain().get_curve().get_p().bytes(); + if(m_params.compression_type() != PointGFp::COMPRESSED) + { + point_size *= 2; // uncompressed and hybrid contains x AND y + } + point_size += 1; // format byte + + std::unique_ptr<MessageAuthenticationCode> mac = m_params.create_mac(); + BOTAN_ASSERT(mac != nullptr, "MAC is found"); + + if(in_len < point_size + mac->output_length()) + { + throw Decoding_Error("ECIES decryption: ciphertext is too short"); + } + + // extract data + const std::vector<byte> other_public_key_bin(in, in + point_size); // the received (ephemeral) public key + const std::vector<byte> encrypted_data(in + point_size, in + in_len - mac->output_length()); + const std::vector<byte> mac_data(in + in_len - mac->output_length(), in + in_len); + + // ISO 18033: step a + PointGFp other_public_key = OS2ECP(other_public_key_bin, m_params.domain().get_curve()); + + // ISO 18033: step b + if(m_params.check_mode() && !other_public_key.on_the_curve()) + { + throw Decoding_Error("ECIES decryption: received public key is not on the curve"); + } + + // ISO 18033: step e (and step f because get_affine_x (called by ECDH_KA_Operation::raw_agree) + // throws Illegal_Transformation if the point is zero) + const SymmetricKey secret_key = m_ka.derive_secret(other_public_key_bin, other_public_key); + + // validate mac + mac->set_key(secret_key.begin() + m_params.dem_keylen(), m_params.mac_keylen()); + mac->update(encrypted_data); + if(!m_label.empty()) + { + mac->update(m_label); + } + const secure_vector<byte> calculated_mac = mac->final(); + valid_mask = CT::expand_mask<byte>(same_mem(mac_data.data(), calculated_mac.data(), mac_data.size())); + + if(valid_mask) + { + // decrypt data + std::unique_ptr<Cipher_Mode> cipher = m_params.create_cipher(DECRYPTION); + BOTAN_ASSERT(cipher != nullptr, "Cipher is found"); + + cipher->set_key(SymmetricKey(secret_key.begin(), m_params.dem_keylen())); + if(m_iv.size() != 0) + { + cipher->start(m_iv.bits_of()); + } + + try + { + // the decryption can fail: + // e.g. Integrity_Failure is thrown if GCM is used and the message does not have a valid tag + secure_vector<byte> decrypted_data(encrypted_data.begin(), encrypted_data.end()); + cipher->finish(decrypted_data); + return decrypted_data; + } + catch(...) + { + valid_mask = 0; + } + } + return secure_vector<byte>(); + } + +} |