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- // Copyright 2015 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "components/gcm_driver/crypto/p256_key_util.h"
- #include <stddef.h>
- #include <stdint.h>
- #include <memory>
- #include <vector>
- #include "base/logging.h"
- #include "base/strings/string_util.h"
- #include "crypto/ec_private_key.h"
- #include "third_party/boringssl/src/include/openssl/ec.h"
- #include "third_party/boringssl/src/include/openssl/ecdh.h"
- #include "third_party/boringssl/src/include/openssl/evp.h"
- namespace gcm {
- namespace {
- // A P-256 field element consists of 32 bytes.
- const size_t kFieldBytes = 32;
- // A P-256 point in uncompressed form consists of 0x04 (to denote that the point
- // is uncompressed per SEC1 2.3.3) followed by two, 32-byte field elements.
- const size_t kUncompressedPointBytes = 1 + 2 * kFieldBytes;
- } // namespace
- bool GetRawPublicKey(const crypto::ECPrivateKey& key, std::string* public_key) {
- DCHECK(public_key);
- std::string candidate_public_key;
- // ECPrivateKey::ExportRawPublicKey() returns the EC point in the uncompressed
- // point format.
- if (!key.ExportRawPublicKey(&candidate_public_key) ||
- candidate_public_key.size() != kUncompressedPointBytes) {
- DLOG(ERROR) << "Unable to export the public key.";
- return false;
- }
- public_key->erase();
- public_key->reserve(kUncompressedPointBytes);
- public_key->append(candidate_public_key);
- return true;
- }
- // TODO(peter): Get rid of this once all key management code has been updated
- // to use ECPrivateKey instead of std::string.
- bool GetRawPrivateKey(const crypto::ECPrivateKey& key,
- std::string* private_key) {
- DCHECK(private_key);
- std::vector<uint8_t> private_key_vector;
- if (!key.ExportPrivateKey(&private_key_vector))
- return false;
- private_key->assign(private_key_vector.begin(), private_key_vector.end());
- return true;
- }
- bool ComputeSharedP256Secret(crypto::ECPrivateKey& key,
- const base::StringPiece& peer_public_key,
- std::string* out_shared_secret) {
- DCHECK(out_shared_secret);
- EC_KEY* ec_private_key = EVP_PKEY_get0_EC_KEY(key.key());
- if (!ec_private_key || !EC_KEY_check_key(ec_private_key)) {
- DLOG(ERROR) << "The private key is invalid.";
- return false;
- }
- bssl::UniquePtr<EC_POINT> point(
- EC_POINT_new(EC_KEY_get0_group(ec_private_key)));
- if (!point || !EC_POINT_oct2point(
- EC_KEY_get0_group(ec_private_key), point.get(),
- reinterpret_cast<const uint8_t*>(peer_public_key.data()),
- peer_public_key.size(), nullptr)) {
- DLOG(ERROR) << "Can't convert peer public value to curve point.";
- return false;
- }
- uint8_t result[kFieldBytes];
- if (ECDH_compute_key(result, sizeof(result), point.get(), ec_private_key,
- nullptr) != sizeof(result)) {
- DLOG(ERROR) << "Unable to compute the ECDH shared secret.";
- return false;
- }
- out_shared_secret->assign(reinterpret_cast<char*>(result), sizeof(result));
- return true;
- }
- } // namespace gcm
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