Add support for Header Protection to QuicCrypter classes

gfe-relnote: no behavior change (adds unused methods to QuicCrypter classes)
PiperOrigin-RevId: 239293044
Change-Id: I0365ad92962102714787b44d346f5c698900ead9
diff --git a/quic/core/crypto/chacha_base_decrypter.cc b/quic/core/crypto/chacha_base_decrypter.cc
new file mode 100644
index 0000000..e58fb1e
--- /dev/null
+++ b/quic/core/crypto/chacha_base_decrypter.cc
@@ -0,0 +1,41 @@
+// Copyright (c) 2013 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 "net/third_party/quiche/src/quic/core/crypto/chacha_base_decrypter.h"
+
+#include <cstdint>
+
+#include "third_party/boringssl/src/include/openssl/chacha.h"
+#include "net/third_party/quiche/src/quic/core/quic_data_reader.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_bug_tracker.h"
+
+namespace quic {
+
+bool ChaChaBaseDecrypter::SetHeaderProtectionKey(QuicStringPiece key) {
+  if (key.size() != GetKeySize()) {
+    QUIC_BUG << "Invalid key size for header protection";
+    return false;
+  }
+  memcpy(pne_key_, key.data(), key.size());
+  return true;
+}
+
+std::string ChaChaBaseDecrypter::GenerateHeaderProtectionMask(
+    QuicDataReader* sample_reader) {
+  QuicStringPiece sample;
+  if (!sample_reader->ReadStringPiece(&sample, 16)) {
+    return std::string();
+  }
+  const uint8_t* nonce = reinterpret_cast<const uint8_t*>(sample.data()) + 4;
+  uint32_t counter;
+  QuicDataReader(sample.data(), 4, Endianness::HOST_BYTE_ORDER)
+      .ReadUInt32(&counter);
+  const uint8_t zeroes[] = {0, 0, 0, 0, 0};
+  std::string out(arraysize(zeroes), 0);
+  CRYPTO_chacha_20(reinterpret_cast<uint8_t*>(const_cast<char*>(out.data())),
+                   zeroes, arraysize(zeroes), pne_key_, nonce, counter);
+  return out;
+}
+
+}  // namespace quic