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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/interest_group/interest_group_pmt_test_utils.h"
#include <optional>
#include <string>
#include <string_view>
#include "base/base64.h"
#include "base/check.h"
#include "base/containers/contains.h"
#include "base/containers/span.h"
#include "base/strings/to_string.h"
#include "components/cbor/reader.h"
#include "components/cbor/writer.h"
#include "content/browser/interest_group/bidding_and_auction_server_key_fetcher.h"
#include "content/browser/interest_group/interest_group_pmt_report_util.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "third_party/boringssl/src/include/openssl/base.h"
#include "third_party/boringssl/src/include/openssl/hpke.h"
namespace content::PrivateModelTrainingTestUtils {
namespace {
// Helper function needed in order to test encryption.
// Returns empty vector in the case of an error.
std::optional<std::vector<uint8_t>> DecryptPayloadWithHpke(
base::span<const uint8_t> payload,
const EVP_HPKE_KEY& key,
base::span<const uint8_t> expected_serialized_shared_info) {
base::span<const uint8_t> enc = payload.first<X25519_PUBLIC_VALUE_LEN>();
bssl::ScopedEVP_HPKE_CTX recipient_context;
if (!EVP_HPKE_CTX_setup_recipient(
/*ctx=*/recipient_context.get(), /*key=*/&key,
/*kdf=*/EVP_hpke_hkdf_sha256(),
/*aead=*/EVP_hpke_chacha20_poly1305(),
/*enc=*/enc.data(), /*enc_len=*/enc.size(),
/*info=*/expected_serialized_shared_info.data(),
/*info_len=*/expected_serialized_shared_info.size())) {
return std::nullopt;
}
auto ciphertext = payload.subspan<X25519_PUBLIC_VALUE_LEN>();
std::vector<uint8_t> plaintext(ciphertext.size());
size_t plaintext_len;
if (!EVP_HPKE_CTX_open(
/*ctx=*/recipient_context.get(), /*out=*/plaintext.data(),
/*out_len*/ &plaintext_len, /*max_out_len=*/plaintext.size(),
/*in=*/ciphertext.data(), /*in_len=*/ciphertext.size(),
/*ad=*/nullptr,
/*ad_len=*/0)) {
return std::nullopt;
}
plaintext.resize(plaintext_len);
return plaintext;
}
// Helper function to create the shared info CBOR with the domain separation
// prefix, meant for encryption.
std::optional<std::vector<uint8_t>> CreateSharedInfoForEncryption(
const std::vector<uint8_t>& cbor_data) {
// Read the CBOR data
const auto maybe_map = cbor::Reader::Read(cbor_data);
if (!maybe_map || !maybe_map->is_map()) {
return std::nullopt; // Return on CBOR read error
}
const auto& map = maybe_map->GetMap();
// Extract shared_info's cbor map
const auto shared_info_it = map.find(cbor::Value("shared_info"));
if (shared_info_it == map.end() || !shared_info_it->second.is_map()) {
return std::nullopt; // Return if shared_info map is not found
}
const auto& shared_info_map = shared_info_it->second.GetMap();
// Write the shared info map to CBOR
std::optional<std::vector<uint8_t>> cbor_data_to_prefix =
cbor::Writer::Write(cbor::Value(shared_info_map));
if (!cbor_data_to_prefix.has_value()) {
return std::nullopt; // Return on CBOR write error
}
// Prefix the shared_info with the domain separation prefix
std::vector<uint8_t> prefixed_cbor;
prefixed_cbor.reserve(
PrivateModelTrainingRequest::kDomainSeparationPrefix.size() +
cbor_data_to_prefix.value().size());
prefixed_cbor.insert(
prefixed_cbor.end(),
PrivateModelTrainingRequest::kDomainSeparationPrefix.begin(),
PrivateModelTrainingRequest::kDomainSeparationPrefix.end());
prefixed_cbor.insert(prefixed_cbor.end(), cbor_data_to_prefix.value().begin(),
cbor_data_to_prefix.value().end());
return prefixed_cbor;
}
// Helper function to extract encrypted payload from CBOR data.
std::optional<std::vector<uint8_t>> ExtractPayloadFromCbor(
const std::vector<uint8_t>& cbor_data) {
const auto maybe_map = cbor::Reader::Read(cbor_data);
if (!maybe_map || !maybe_map->is_map()) {
return std::nullopt;
}
const auto& map = maybe_map->GetMap();
const auto aggregation_service_payload_it =
map.find(cbor::Value("aggregation_service_payload"));
if (aggregation_service_payload_it == map.end() ||
!aggregation_service_payload_it->second.is_map()) {
return std::nullopt;
}
const auto& aggregation_service_payload_map =
aggregation_service_payload_it->second.GetMap();
const auto payload_it =
aggregation_service_payload_map.find(cbor::Value("payload"));
if (payload_it == aggregation_service_payload_map.end() ||
!payload_it->second.is_bytestring()) {
return std::nullopt;
}
return payload_it->second.GetBytestring();
}
} // namespace
TestHpkeKey::TestHpkeKey(std::string key_id) : key_id_(std::move(key_id)) {
EVP_HPKE_KEY_generate(full_hpke_key_.get(), EVP_hpke_x25519_hkdf_sha256());
}
TestHpkeKey::~TestHpkeKey() = default;
TestHpkeKey::TestHpkeKey(TestHpkeKey&&) = default;
TestHpkeKey& TestHpkeKey::operator=(TestHpkeKey&&) = default;
BiddingAndAuctionServerKey TestHpkeKey::GetPublicKey() const {
std::vector<uint8_t> public_key(X25519_PUBLIC_VALUE_LEN);
size_t public_key_len;
EXPECT_TRUE(EVP_HPKE_KEY_public_key(
/*key=*/full_hpke_key_.get(), /*out=*/public_key.data(),
/*out_len=*/&public_key_len, /*max_out=*/public_key.size()));
EXPECT_EQ(public_key.size(), public_key_len);
return BiddingAndAuctionServerKey(
std::string(public_key.begin(), public_key.end()), key_id_);
}
std::optional<std::vector<uint8_t>> ExtractAndDecryptFramedPayloadFromCbor(
const std::vector<uint8_t>& cbor_data,
const EVP_HPKE_KEY& hpke_private_key) {
std::optional<std::vector<uint8_t>> payload =
ExtractPayloadFromCbor(cbor_data);
std::optional<std::vector<uint8_t>> shared_info =
CreateSharedInfoForEncryption(cbor_data);
if (payload.has_value() && shared_info.has_value()) {
return DecryptPayloadWithHpke(std::move(payload.value()), hpke_private_key,
std::move(shared_info.value()));
}
return std::nullopt;
}
} // namespace content::PrivateModelTrainingTestUtils
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