1 files changed, 185 insertions, 0 deletions
diff --git a/media/psshparser/PsshParser.cpp b/media/psshparser/PsshParser.cpp
new file mode 100644
index 0000000000..9a47979164
--- /dev/null
+++ b/media/psshparser/PsshParser.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright 2015, Mozilla Foundation and contributors
+ *
+ * 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.
+ */
+
+#include "PsshParser.h"
+
+#include <assert.h>
+#include <memory.h>
+
+#include <algorithm>
+#include <limits>
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/EndianUtils.h"
+
+// Stripped down version of mp4_demuxer::ByteReader, stripped down to make it
+// easier to link into ClearKey DLL and gtest.
+class ByteReader {
+ public:
+  ByteReader(const uint8_t* aData, size_t aSize)
+      : mPtr(aData), mRemaining(aSize), mLength(aSize) {}
+
+  size_t Offset() const { return mLength - mRemaining; }
+
+  size_t Remaining() const { return mRemaining; }
+
+  size_t Length() const { return mLength; }
+
+  bool CanRead8() const { return mRemaining >= 1; }
+
+  uint8_t ReadU8() {
+    auto ptr = Read(1);
+    if (!ptr) {
+      MOZ_ASSERT(false);
+      return 0;
+    }
+    return *ptr;
+  }
+
+  bool CanRead32() const { return mRemaining >= 4; }
+
+  uint32_t ReadU32() {
+    auto ptr = Read(4);
+    if (!ptr) {
+      MOZ_ASSERT(false);
+      return 0;
+    }
+    return mozilla::BigEndian::readUint32(ptr);
+  }
+
+  const uint8_t* Read(size_t aCount) {
+    if (aCount > mRemaining) {
+      mRemaining = 0;
+      return nullptr;
+    }
+    mRemaining -= aCount;
+
+    const uint8_t* result = mPtr;
+    mPtr += aCount;
+
+    return result;
+  }
+
+  const uint8_t* Seek(size_t aOffset) {
+    if (aOffset > mLength) {
+      MOZ_ASSERT(false);
+      return nullptr;
+    }
+
+    mPtr = mPtr - Offset() + aOffset;
+    mRemaining = mLength - aOffset;
+    return mPtr;
+  }
+
+ private:
+  const uint8_t* mPtr;
+  size_t mRemaining;
+  const size_t mLength;
+};
+
+#define FOURCC(a, b, c, d) ((a << 24) + (b << 16) + (c << 8) + d)
+
+// System ID identifying the cenc v2 pssh box format; specified at:
+// https://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-media/cenc-format.html
+const uint8_t kSystemID[] = {0x10, 0x77, 0xef, 0xec, 0xc0, 0xb2, 0x4d, 0x02,
+                             0xac, 0xe3, 0x3c, 0x1e, 0x52, 0xe2, 0xfb, 0x4b};
+
+bool ParseCENCInitData(const uint8_t* aInitData, uint32_t aInitDataSize,
+                       std::vector<std::vector<uint8_t>>& aOutKeyIds) {
+  aOutKeyIds.clear();
+  std::vector<std::vector<uint8_t>> keyIds;
+  ByteReader reader(aInitData, aInitDataSize);
+  while (reader.CanRead32()) {
+    // Box size. For the common system Id, ignore this, as some useragents
+    // handle invalid box sizes.
+    const size_t start = reader.Offset();
+    const size_t size = reader.ReadU32();
+    if (size > std::numeric_limits<size_t>::max() - start) {
+      // Ensure 'start + size' calculation below can't overflow.
+      return false;
+    }
+    const size_t end = start + size;
+    if (end > reader.Length()) {
+      // Ridiculous sized box.
+      return false;
+    }
+
+    // PSSH box type.
+    if (!reader.CanRead32()) {
+      return false;
+    }
+    uint32_t box = reader.ReadU32();
+    if (box != FOURCC('p', 's', 's', 'h')) {
+      return false;
+    }
+
+    // 1 byte version, 3 bytes flags.
+    if (!reader.CanRead32()) {
+      return false;
+    }
+    uint8_t version = reader.ReadU8();
+    if (version != 1) {
+      // Ignore pssh boxes with wrong version.
+      reader.Seek(std::max<size_t>(reader.Offset(), end));
+      continue;
+    }
+    reader.Read(3);  // skip flags.
+
+    // SystemID
+    const uint8_t* sid = reader.Read(sizeof(kSystemID));
+    if (!sid) {
+      // Insufficient bytes to read SystemID.
+      return false;
+    }
+
+    if (memcmp(kSystemID, sid, sizeof(kSystemID))) {
+      // Ignore pssh boxes with wrong system ID.
+      reader.Seek(std::max<size_t>(reader.Offset(), end));
+      continue;
+    }
+
+    if (!reader.CanRead32()) {
+      return false;
+    }
+    uint32_t kidCount = reader.ReadU32();
+
+    if (kidCount * CENC_KEY_LEN > reader.Remaining()) {
+      // Not enough bytes remaining to read all keys.
+      return false;
+    }
+
+    for (uint32_t i = 0; i < kidCount; i++) {
+      const uint8_t* kid = reader.Read(CENC_KEY_LEN);
+      keyIds.push_back(std::vector<uint8_t>(kid, kid + CENC_KEY_LEN));
+    }
+
+    // Size of extra data. EME CENC format spec says datasize should
+    // always be 0. We explicitly read the datasize, in case the box
+    // size was 0, so that we get to the end of the box.
+    if (!reader.CanRead32()) {
+      return false;
+    }
+    reader.ReadU32();
+
+    // Jump forwards to the end of the box, skipping any padding.
+    if (size) {
+      reader.Seek(end);
+    }
+  }
+  aOutKeyIds = std::move(keyIds);
+  return true;
+}