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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.
#include "media/cdm/cenc_utils.h"
#include <memory>
#include "base/macros.h"
#include "media/formats/mp4/box_definitions.h"
#include "media/formats/mp4/box_reader.h"
namespace media {
// 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
// CENC SystemID for the Common System.
// https://w3c.github.io/encrypted-media/cenc-format.html#common-system
const uint8_t kCencCommonSystemId[] = {0x10, 0x77, 0xef, 0xec, 0xc0, 0xb2,
0x4d, 0x02, 0xac, 0xe3, 0x3c, 0x1e,
0x52, 0xe2, 0xfb, 0x4b};
// Returns true if |input| contains only 1 or more valid 'pssh' boxes, false
// otherwise. |pssh_boxes| is updated as the set of parsed 'pssh' boxes.
// Note: All boxes in |input| must be 'pssh' boxes. However, if they can't be
// properly parsed (e.g. unsupported version), then they will be skipped.
static bool ReadAllPsshBoxes(
const std::vector<uint8_t>& input,
std::vector<mp4::FullProtectionSystemSpecificHeader>* pssh_boxes) {
DCHECK(!input.empty());
// Verify that |input| contains only 'pssh' boxes.
// ReadAllChildrenAndCheckFourCC() is templated, so it checks that each
// box in |input| matches the box type of the parameter (in this case
// mp4::ProtectionSystemSpecificHeader is a 'pssh' box).
// mp4::ProtectionSystemSpecificHeader doesn't validate the 'pssh' contents,
// so this simply verifies that |input| only contains 'pssh' boxes and
// nothing else.
std::unique_ptr<mp4::BoxReader> input_reader(
mp4::BoxReader::ReadConcatentatedBoxes(input.data(), input.size()));
std::vector<mp4::ProtectionSystemSpecificHeader> raw_pssh_boxes;
if (!input_reader->ReadAllChildrenAndCheckFourCC(&raw_pssh_boxes))
return false;
// Now that we have |input| parsed into |raw_pssh_boxes|, reparse each one
// into a mp4::FullProtectionSystemSpecificHeader, which extracts all the
// relevant fields from the box. Since there may be unparseable 'pssh' boxes
// (due to unsupported version, for example), this is done one by one,
// ignoring any boxes that can't be parsed.
for (const auto& raw_pssh_box : raw_pssh_boxes) {
std::unique_ptr<mp4::BoxReader> raw_pssh_reader(
mp4::BoxReader::ReadConcatentatedBoxes(raw_pssh_box.raw_box.data(),
raw_pssh_box.raw_box.size()));
// ReadAllChildren() appends any successfully parsed box onto it's
// parameter, so |pssh_boxes| will contain the collection of successfully
// parsed 'pssh' boxes. If an error occurs, try the next box.
if (!raw_pssh_reader->ReadAllChildrenAndCheckFourCC(pssh_boxes))
continue;
}
// Must have successfully parsed at least one 'pssh' box.
return pssh_boxes->size() > 0;
}
bool ValidatePsshInput(const std::vector<uint8_t>& input) {
// No 'pssh' boxes is considered valid.
if (input.empty())
return true;
std::vector<mp4::FullProtectionSystemSpecificHeader> children;
return ReadAllPsshBoxes(input, &children);
}
bool GetKeyIdsForCommonSystemId(const std::vector<uint8_t>& pssh_boxes,
KeyIdList* key_ids) {
// If there are no 'pssh' boxes then no key IDs found.
if (pssh_boxes.empty())
return false;
std::vector<mp4::FullProtectionSystemSpecificHeader> children;
if (!ReadAllPsshBoxes(pssh_boxes, &children))
return false;
// Check all children for an appropriate 'pssh' box, returning the
// key IDs found.
KeyIdList result;
std::vector<uint8_t> common_system_id(
kCencCommonSystemId,
kCencCommonSystemId + arraysize(kCencCommonSystemId));
for (const auto& child : children) {
if (child.system_id == common_system_id) {
key_ids->assign(child.key_ids.begin(), child.key_ids.end());
return key_ids->size() > 0;
}
}
// No matching 'pssh' box found.
return false;
}
bool GetPsshData(const std::vector<uint8_t>& input,
const std::vector<uint8_t>& system_id,
std::vector<uint8_t>* pssh_data) {
if (input.empty())
return false;
std::vector<mp4::FullProtectionSystemSpecificHeader> children;
if (!ReadAllPsshBoxes(input, &children))
return false;
// Check all children for an appropriate 'pssh' box, returning |data| from
// the first one found.
for (const auto& child : children) {
if (child.system_id == system_id) {
pssh_data->assign(child.data.begin(), child.data.end());
return true;
}
}
// No matching 'pssh' box found.
return false;
}
} // namespace media
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