Support encrypted RTP extensions (RFC 6904)

webrtc/media/base/fakertp.cc

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <algorithm>
+
+#include "webrtc/base/gunit.h"
+#include "webrtc/media/base/fakertp.h"
+
+void CompareHeaderExtensions(const char* packet1, size_t packet1_size,
+    const char* packet2, size_t packet2_size,
+    const std::vector<int> encrypted_headers, bool expect_equal) {
+  // Sanity check: packets must be large enough to contain the RTP header and
+  // extensions header.
+  RTC_CHECK_GE(packet1_size, 12 + 4);
+  RTC_CHECK_GE(packet2_size, 12 + 4);
+  // RTP extension headers are the same.
+  EXPECT_EQ(0, memcmp(packet1 + 12, packet2 + 12, 4));
+  // Check for one-byte header extensions.
+  EXPECT_EQ('\xBE', packet1[12]);
+  EXPECT_EQ('\xDE', packet1[13]);
+  // Determine position and size of extension headers.
+  size_t extension_words = packet1[14] << 8 | packet1[15];
+  const char* extension_data1 = packet1 + 12 + 4;
+  const char* extension_end1 = extension_data1 + extension_words * 4;
+  const char* extension_data2 = packet2 + 12 + 4;
+  // Sanity check: packets must be large enough to contain the RTP header
+  // extensions.
+  RTC_CHECK_GE(packet1_size, 12 + 4 + extension_words * 4);
+  RTC_CHECK_GE(packet2_size, 12 + 4 + extension_words * 4);
+  while (extension_data1 < extension_end1) {
+    uint8_t id = (*extension_data1 & 0xf0) >> 4;
+    uint8_t len = (*extension_data1 & 0x0f) +1;
+    extension_data1++;
+    extension_data2++;
+    EXPECT_LE(extension_data1, extension_end1);
+    if (id == 15) {
+      // Finished parsing.
+      break;
+    }
+
+    // The header extension doesn't get encrypted if the id is not in the
+    // list of header extensions to encrypt.
+    if (expect_equal ||
+        std::find(encrypted_headers.begin(), encrypted_headers.end(), id)
+            == encrypted_headers.end()) {
+      EXPECT_EQ(0, memcmp(extension_data1, extension_data2, len));
+    } else {
+      EXPECT_NE(0, memcmp(extension_data1, extension_data2, len));
+    }
+
+    extension_data1 += len;
+    extension_data2 += len;
+    // Skip padding.
+    while (extension_data1 < extension_end1 && *extension_data1 == 0) {
+      extension_data1++;
+      extension_data2++;
+    }
+  }
+}