64 lines
2.3 KiB
C++
64 lines
2.3 KiB
C++
/*
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* Copyright 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "compos_key.h"
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#include <openssl/digest.h>
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#include <openssl/hkdf.h>
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#include <openssl/mem.h>
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using android::base::ErrnoError;
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using android::base::Error;
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using android::base::Result;
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using compos_key::Ed25519KeyPair;
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using compos_key::Signature;
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// Used to ensure the key we derive is distinct from any other.
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constexpr const char* kSigningKeyInfo = "CompOS signing key";
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namespace compos_key {
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Result<Ed25519KeyPair> deriveKeyFromSecret(const uint8_t* secret, size_t secret_size) {
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// Ed25519 private keys are derived from a 32 byte seed:
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// https://datatracker.ietf.org/doc/html/rfc8032#section-5.1.5
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std::array<uint8_t, 32> seed;
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// We derive the seed from the secret using HKDF - see
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// https://datatracker.ietf.org/doc/html/rfc5869#section-2.
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if (!HKDF(seed.data(), seed.size(), EVP_sha256(), secret, secret_size, /*salt=*/nullptr,
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/*salt_len=*/0, reinterpret_cast<const uint8_t*>(kSigningKeyInfo),
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strlen(kSigningKeyInfo))) {
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return Error() << "HKDF failed";
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}
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Ed25519KeyPair result;
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ED25519_keypair_from_seed(result.public_key.data(), result.private_key.data(), seed.data());
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return result;
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}
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Result<Signature> sign(const PrivateKey& private_key, const uint8_t* data, size_t data_size) {
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Signature result;
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if (!ED25519_sign(result.data(), data, data_size, private_key.data())) {
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return Error() << "Failed to sign";
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}
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return result;
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}
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bool verify(const PublicKey& public_key, const Signature& signature, const uint8_t* data,
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size_t data_size) {
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return ED25519_verify(data, data_size, signature.data(), public_key.data()) == 1;
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}
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} // namespace compos_key
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