Sync with upstream repo.

Changes include:
* CPU check has been broken up into a number of small libraries
* BoringSSL option has been removed
* Better abseil integration

crypto.h

@@ -0,0 +1,54 @@
+// Copyright 2020 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
+//
+//      http://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.
+
+#ifndef THIRD_PARTY_CPU_CHECK_CRYPTO_H_
+#define THIRD_PARTY_CPU_CHECK_CRYPTO_H_
+
+#include "malign_buffer.h"
+#include "absl/status/status.h"
+#include "absl/strings/string_view.h"
+#include <openssl/crypto.h>
+#include <openssl/evp.h>
+
+namespace cpu_check {
+
+class Crypto {
+ public:
+  // Encryption produces these values, which are consumed by decryption.
+  struct CryptoPurse {
+    unsigned char i_vec[12];
+    unsigned char gmac_tag[16];
+  };
+
+  // Encrypts 'plain_text' to 'cipher_text' and stores i_vec and gmac
+  // in 'purse'.
+  static absl::Status Encrypt(const MalignBuffer &plain_text,
+                              MalignBuffer *cipher_text, CryptoPurse *purse);
+
+  // Decrypts 'cipher_text' into 'plain_text' using i_vec and gmac from 'purse'.
+  static absl::Status Decrypt(const MalignBuffer &cipher_text,
+                              const CryptoPurse &purse,
+                              MalignBuffer *plain_text);
+
+  // Runs crypto self test, if available.
+  static absl::Status SelfTest();
+
+ private:
+  // Returns kInternal error and frees context 'cipher_ctx'.
+  static absl::Status ReturnError(absl::string_view message,
+                                  EVP_CIPHER_CTX *cipher_ctx);
+};
+
+};      // namespace cpu_check
+#endif  // THIRD_PARTY_CPU_CHECK_CRYPTO_H_