99 lines
3.1 KiB
C++
99 lines
3.1 KiB
C++
// Copyright 2021 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://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, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#define PW_LOG_MODULE_NAME "ECDSA-BSSL"
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#define PW_LOG_LEVEL PW_LOG_LEVEL_WARN
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#include "openssl/bn.h"
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#include "openssl/ec.h"
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#include "openssl/ecdsa.h"
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#include "openssl/nid.h"
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#include "pw_crypto/ecdsa.h"
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#include "pw_log/log.h"
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namespace pw::crypto::ecdsa {
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constexpr size_t kP256CurveOrderBytes = 32;
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Status VerifyP256Signature(ConstByteSpan public_key,
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ConstByteSpan digest,
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ConstByteSpan signature) {
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const uint8_t* public_key_bytes =
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reinterpret_cast<const uint8_t*>(public_key.data());
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const uint8_t* digest_bytes = reinterpret_cast<const uint8_t*>(digest.data());
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const uint8_t* signature_bytes =
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reinterpret_cast<const uint8_t*>(signature.data());
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// Allocate objects needed for ECDSA verification. BoringSSL relies on
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// dynamic allocation.
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bssl::UniquePtr<EC_GROUP> group(
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EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1));
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if (!group) {
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return Status::ResourceExhausted();
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}
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bssl::UniquePtr<EC_POINT> pub_key(EC_POINT_new(group.get()));
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bssl::UniquePtr<EC_KEY> key(EC_KEY_new());
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bssl::UniquePtr<ECDSA_SIG> sig(ECDSA_SIG_new());
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if (!(pub_key && key && sig)) {
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return Status::ResourceExhausted();
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}
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// Load the public key.
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if (!EC_POINT_oct2point(group.get(),
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pub_key.get(),
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public_key_bytes,
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public_key.size(),
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nullptr)) {
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PW_LOG_DEBUG("Bad public key format");
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return Status::InvalidArgument();
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}
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if (!EC_KEY_set_group(key.get(), group.get())) {
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return Status::InvalidArgument();
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}
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if (!EC_KEY_set_public_key(key.get(), pub_key.get())) {
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return Status::InvalidArgument();
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}
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// Load the signature.
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if (signature.size() != kP256CurveOrderBytes * 2) {
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PW_LOG_DEBUG("Bad signature format");
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return Status::InvalidArgument();
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}
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if (!(BN_bin2bn(signature_bytes, kP256CurveOrderBytes, sig->r) &&
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BN_bin2bn(signature_bytes + kP256CurveOrderBytes,
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kP256CurveOrderBytes,
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sig->s))) {
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return Status::Internal();
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}
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// Digest must be 32 bytes or longer (and will be truncated).
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if (digest.size() < kP256CurveOrderBytes) {
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PW_LOG_DEBUG("Digest is too short");
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return Status::InvalidArgument();
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}
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// Verify the signature.
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if (!ECDSA_do_verify(digest_bytes, digest.size(), sig.get(), key.get())) {
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PW_LOG_DEBUG("Signature verification failed");
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return Status::Unauthenticated();
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}
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return OkStatus();
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}
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} // namespace pw::crypto::ecdsa
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