Hide internal code in implementation/

Refactoring change.

action_factory* -> implementation/action_factory*
broadcast_request* -> implementation/base_broadcast_request*
encryption* -> implementation/encryption*

Clean up build targets.

PiperOrigin-RevId: 466992367

presence/implementation/encryption.cc

@@ -0,0 +1,110 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "presence/implementation/encryption.h"
+
+#include <algorithm>
+#include <cstring>
+#include <string>
+
+#include "absl/status/status.h"
+#include "absl/status/statusor.h"
+#include "absl/strings/str_format.h"
+#include "internal/platform/logging.h"
+#include <openssl/cipher.h>  // NOLINT
+#include <openssl/crypto.h>
+#include <openssl/evp.h>  // NOLINT
+#include "third_party/tink/cc/subtle/hkdf.h"
+#include "third_party/tink/cc/subtle/random.h"
+
+namespace nearby {
+namespace presence {
+
+using ::crypto::tink::subtle::HashType;
+using ::crypto::tink::subtle::Hkdf;
+using ::crypto::tink::subtle::Random;
+constexpr int kAuthenticityKeyByteSize = 16;
+constexpr int kMetadataKeyMaxSize = 16;
+constexpr int kAesCtrIvSize = 16;
+constexpr int kSaltSize = 2;
+
+std::string Encryption::CustomizeBytesSize(absl::string_view bytes,
+                                           size_t len) {
+  auto result =
+      Hkdf::ComputeHkdf(HashType::SHA256, /*ikm=*/bytes,
+                        /*salt=*/std::string(kAuthenticityKeyByteSize, 0),
+                        /*info=*/"", /*out_len=*/len);
+  return result.value();
+}
+
+std::string Encryption::GenerateRandomByteArray(size_t len) {
+  return Random::GetRandomBytes(len);
+}
+
+absl::StatusOr<std::string> Encryption::RunMetadataEncryption(
+    absl::string_view metadata, absl::string_view key, absl::string_view salt,
+    bool encrypt) {
+  if (metadata.size() > kMetadataKeyMaxSize) {
+    return absl::InvalidArgumentError(
+        absl::StrFormat("Metadata key length %d greater than %d",
+                        metadata.size(), kMetadataKeyMaxSize));
+  }
+  if (key.size() != kAuthenticityKeyByteSize) {
+    return absl::InvalidArgumentError(
+        absl::StrFormat("Invalid authenticity key length %d. Expected %d",
+                        key.size(), kAuthenticityKeyByteSize));
+  }
+  if (salt.size() != kSaltSize) {
+    return absl::InvalidArgumentError(absl::StrFormat(
+        "Invalid salt length %d, Expected %d.", salt.size(), kSaltSize));
+  }
+  auto output = std::string(metadata.size(), 0);
+  int output_size;
+  std::string iv = CustomizeBytesSize(salt, kAesCtrIvSize);
+
+  // AES-CTR is used without authentication because it's used as a PRF.
+  auto ctx =
+      std::unique_ptr<EVP_CIPHER_CTX, std::function<void(EVP_CIPHER_CTX*)>>(
+          EVP_CIPHER_CTX_new(), EVP_CIPHER_CTX_free);
+  if (1 != EVP_CipherInit_ex(ctx.get(), EVP_aes_128_ctr(), nullptr,
+                             reinterpret_cast<const uint8_t*>(key.data()),
+                             reinterpret_cast<const uint8_t*>(iv.data()),
+                             encrypt ? 1 : 0)) {
+    return absl::InvalidArgumentError("Failed to initialize AES encryption.");
+  }
+
+  int input_size = metadata.size();
+  if (1 != EVP_CipherUpdate(
+               ctx.get(), reinterpret_cast<uint8_t*>(output.data()),
+               &output_size, reinterpret_cast<const uint8_t*>(metadata.data()),
+               input_size)) {
+    return absl::InvalidArgumentError("AES error in EVP_CipherUpdate");
+  }
+  int tmp_size = 0;
+  if (1 != EVP_EncryptFinal_ex(
+               ctx.get(),
+               reinterpret_cast<uint8_t*>(output.data() + output_size),
+               &tmp_size)) {
+    return absl::InvalidArgumentError("AES errorin EVP_EncryptFinal_ex");
+  }
+  output_size += tmp_size;
+  if (output_size != input_size) {
+    return absl::InvalidArgumentError(absl::StrFormat(
+        "Invalid output size %d. Expected %d", output_size, input_size));
+  }
+  return output;
+}
+
+}  // namespace presence
+}  // namespace nearby