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Merge 317490 "Handle 'cenc' Initialization Data Type in Clear Key."
> Handle 'cenc' Initialization Data Type in Clear Key. > > Initialization data is provided as concatentated PSSH boxes. Parse the > PSSH boxes and extract the keys, if present. Only process the PSSH > boxes that contain the Clear Key SystemID, all other PSSH boxes are > skipped. > > This handles both version 0 and version 1 PSSH boxes. > > BUG=459850 > TEST=new tests pass > > Review URL: https://codereview.chromium.org/936953005 Cr-Commit-Position: refs/heads/master@{#317490} (cherry picked from commit 0961c42) [email protected] Review URL: https://codereview.chromium.org/958183003 Cr-Commit-Position: refs/branch-heads/2311@{#45} Cr-Branched-From: 09b7de5-refs/heads/master@{#317474}
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| Original file line number | Diff line number | Diff line change |
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| // Copyright 2015 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. | ||
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| #include "media/cdm/cenc_utils.h" | ||
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| #include "media/base/bit_reader.h" | ||
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| namespace media { | ||
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| // The initialization data for encrypted media files using the ISO Common | ||
| // Encryption ('cenc') protection scheme may contain one or more protection | ||
| // system specific header ('pssh') boxes. | ||
| // ref: https://w3c.github.io/encrypted-media/cenc-format.html | ||
| // | ||
| // The format of a 'pssh' box is as follows: | ||
| // unsigned int(32) size; | ||
| // unsigned int(32) type = "pssh"; | ||
| // if (size==1) { | ||
| // unsigned int(64) largesize; | ||
| // } else if (size==0) { | ||
| // -- box extends to end of file | ||
| // } | ||
| // unsigned int(8) version; | ||
| // bit(24) flags; | ||
| // unsigned int(8)[16] SystemID; | ||
| // if (version > 0) | ||
| // { | ||
| // unsigned int(32) KID_count; | ||
| // { | ||
| // unsigned int(8)[16] KID; | ||
| // } [KID_count] | ||
| // } | ||
| // unsigned int(32) DataSize; | ||
| // unsigned int(8)[DataSize] Data; | ||
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| // Minimum size of a 'pssh' box includes all the required fields (size, type, | ||
| // version, flags, SystemID, DataSize). | ||
| const int kMinimumBoxSizeInBytes = 32; | ||
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| // SystemID for the Common System. | ||
| // https://w3c.github.io/encrypted-media/cenc-format.html#common-system | ||
| const uint8 kCommonSystemId[] = { 0x10, 0x77, 0xef, 0xec, | ||
| 0xc0, 0xb2, 0x4d, 0x02, | ||
| 0xac, 0xe3, 0x3c, 0x1e, | ||
| 0x52, 0xe2, 0xfb, 0x4b }; | ||
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| #define RCHECK(x) \ | ||
| do { \ | ||
| if (!(x)) \ | ||
| return false; \ | ||
| } while (0) | ||
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| // Helper function to read up to 32 bits from a bit stream. | ||
| static uint32 ReadBits(BitReader* reader, int num_bits) { | ||
| DCHECK_GE(reader->bits_available(), num_bits); | ||
| DCHECK((num_bits > 0) && (num_bits <= 32)); | ||
| uint32 value; | ||
| reader->ReadBits(num_bits, &value); | ||
| return value; | ||
| } | ||
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| // Checks whether the next 16 bytes matches the Common SystemID. | ||
| // Assumes |reader| has enough data. | ||
| static bool IsCommonSystemID(BitReader* reader) { | ||
| for (uint32 i = 0; i < arraysize(kCommonSystemId); ++i) { | ||
| if (ReadBits(reader, 8) != kCommonSystemId[i]) | ||
| return false; | ||
| } | ||
| return true; | ||
| } | ||
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| bool GetKeyIdsForCommonSystemId(const uint8* input, | ||
| int input_length, | ||
| std::vector<std::vector<uint8>>* key_ids) { | ||
| int offset = 0; | ||
| std::vector<std::vector<uint8>> result; | ||
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| while (offset < input_length) { | ||
| BitReader reader(input + offset, input_length - offset); | ||
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| // Enough data for a miniumum size 'pssh' box? | ||
| RCHECK(reader.bits_available() >= kMinimumBoxSizeInBytes * 8); | ||
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| uint32 size = ReadBits(&reader, 32); | ||
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| // Must be a 'pssh' box or else fail. | ||
| RCHECK(ReadBits(&reader, 8) == 'p'); | ||
| RCHECK(ReadBits(&reader, 8) == 's'); | ||
| RCHECK(ReadBits(&reader, 8) == 's'); | ||
| RCHECK(ReadBits(&reader, 8) == 'h'); | ||
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| if (size == 1) { | ||
| // If largesize > 2**32 it is too big. | ||
| RCHECK(ReadBits(&reader, 32) == 0); | ||
| size = ReadBits(&reader, 32); | ||
| } else if (size == 0) { | ||
| size = input_length - offset; | ||
| } | ||
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| // Check that the buffer contains at least size bytes. | ||
| RCHECK(static_cast<uint32>(input_length - offset) >= size); | ||
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| // Update offset to point at the next 'pssh' box (may not be one). | ||
| offset += size; | ||
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| // Check the version, as KIDs only available if version > 0. | ||
| uint8 version = ReadBits(&reader, 8); | ||
| if (version == 0) | ||
| continue; | ||
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| // flags must be 0. If not, assume incorrect 'pssh' box and move to the | ||
| // next one. | ||
| if (ReadBits(&reader, 24) != 0) | ||
| continue; | ||
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| // Validate SystemID | ||
| RCHECK(static_cast<uint32>(reader.bits_available()) >= | ||
| arraysize(kCommonSystemId) * 8); | ||
| if (!IsCommonSystemID(&reader)) | ||
| continue; // Not Common System, so try the next pssh box. | ||
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| // Since version > 0, next field is the KID_count. | ||
| RCHECK(static_cast<uint32>(reader.bits_available()) >= sizeof(uint32) * 8); | ||
| uint32 count = ReadBits(&reader, 32); | ||
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| if (count == 0) | ||
| continue; | ||
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| // Make sure there is enough data for all the KIDs specified, and then | ||
| // extract them. | ||
| RCHECK(static_cast<uint32>(reader.bits_available()) > count * 16 * 8); | ||
| while (count > 0) { | ||
| std::vector<uint8> key; | ||
| key.reserve(16); | ||
| for (int i = 0; i < 16; ++i) { | ||
| key.push_back(ReadBits(&reader, 8)); | ||
| } | ||
| result.push_back(key); | ||
| --count; | ||
| } | ||
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| // Don't bother checking DataSize and Data. | ||
| } | ||
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| key_ids->swap(result); | ||
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| // TODO(jrummell): This should return true only if there was at least one | ||
| // key ID present. However, numerous test files don't contain the 'pssh' box | ||
| // for Common Format, so no keys are found. http://crbug.com/460308 | ||
| return true; | ||
| } | ||
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| } // namespace media |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| // Copyright 2015 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. | ||
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| #ifndef MEDIA_CDM_CENC_UTILS_H_ | ||
| #define MEDIA_CDM_CENC_UTILS_H_ | ||
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| #include <vector> | ||
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| #include "base/basictypes.h" | ||
| #include "media/base/media_export.h" | ||
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| namespace media { | ||
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| // Gets the Key Ids from a 'pssh' box for the Common SystemID among one or | ||
| // more concatenated 'pssh' boxes. If |input| looks valid, then true is | ||
| // returned and |key_ids| is updated to contain the values found. Otherwise | ||
| // return false. | ||
| // TODO(jrummell): This returns true if no Common SystemID 'pssh' boxes are | ||
| // found, or are included but don't contain any key IDs. This should be | ||
| // fixed once the test files are updated to include correct 'pssh' boxes. | ||
| // http://crbug.com/460308 | ||
| MEDIA_EXPORT bool GetKeyIdsForCommonSystemId( | ||
| const uint8* input, | ||
| int input_length, | ||
| std::vector<std::vector<uint8>>* key_ids); | ||
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| } // namespace media | ||
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| #endif // MEDIA_CDM_CENC_UTILS_H_ |
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