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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 //#define LOG_NDEBUG 0
     18 #define LOG_TAG "ClearKeyCryptoPlugin"
     19 #include <utils/Log.h>
     20 
     21 #include <endian.h>
     22 #include <media/stagefright/foundation/AString.h>
     23 #include <media/stagefright/foundation/base64.h>
     24 #include <media/stagefright/MediaErrors.h>
     25 #include <string.h>
     26 
     27 #include "InitDataParser.h"
     28 
     29 #include "ClearKeyUUID.h"
     30 #include "MimeType.h"
     31 #include "Utils.h"
     32 
     33 namespace clearkeydrm {
     34 
     35 using android::AString;
     36 using android::String8;
     37 using android::Vector;
     38 
     39 namespace {
     40     const size_t kKeyIdSize = 16;
     41     const size_t kSystemIdSize = 16;
     42 }
     43 
     44 android::status_t InitDataParser::parse(const Vector<uint8_t>& initData,
     45         const String8& type,
     46         Vector<uint8_t>* licenseRequest) {
     47     // Build a list of the key IDs
     48     Vector<const uint8_t*> keyIds;
     49     if (type == kIsoBmffVideoMimeType ||
     50         type == kIsoBmffAudioMimeType ||
     51         type == kCencInitDataFormat) {
     52         android::status_t res = parsePssh(initData, &keyIds);
     53         if (res != android::OK) {
     54             return res;
     55         }
     56     } else if (type == kWebmVideoMimeType ||
     57         type == kWebmAudioMimeType ||
     58         type == kWebmInitDataFormat) {
     59         // WebM "init data" is just a single key ID
     60         if (initData.size() != kKeyIdSize) {
     61             return android::ERROR_DRM_CANNOT_HANDLE;
     62         }
     63         keyIds.push(initData.array());
     64     } else {
     65         return android::ERROR_DRM_CANNOT_HANDLE;
     66     }
     67 
     68     // Build the request
     69     String8 requestJson = generateRequest(keyIds);
     70     licenseRequest->clear();
     71     licenseRequest->appendArray(
     72             reinterpret_cast<const uint8_t*>(requestJson.string()),
     73             requestJson.size());
     74     return android::OK;
     75 }
     76 
     77 android::status_t InitDataParser::parsePssh(const Vector<uint8_t>& initData,
     78         Vector<const uint8_t*>* keyIds) {
     79     size_t readPosition = 0;
     80 
     81     // Validate size field
     82     uint32_t expectedSize = initData.size();
     83     expectedSize = htonl(expectedSize);
     84     if (memcmp(&initData[readPosition], &expectedSize,
     85                sizeof(expectedSize)) != 0) {
     86         return android::ERROR_DRM_CANNOT_HANDLE;
     87     }
     88     readPosition += sizeof(expectedSize);
     89 
     90     // Validate PSSH box identifier
     91     const char psshIdentifier[4] = {'p', 's', 's', 'h'};
     92     if (memcmp(&initData[readPosition], psshIdentifier,
     93                sizeof(psshIdentifier)) != 0) {
     94         return android::ERROR_DRM_CANNOT_HANDLE;
     95     }
     96     readPosition += sizeof(psshIdentifier);
     97 
     98     // Validate EME version number
     99     const uint8_t psshVersion1[4] = {1, 0, 0, 0};
    100     if (memcmp(&initData[readPosition], psshVersion1,
    101                sizeof(psshVersion1)) != 0) {
    102         return android::ERROR_DRM_CANNOT_HANDLE;
    103     }
    104     readPosition += sizeof(psshVersion1);
    105 
    106     // Validate system ID
    107     if (!isClearKeyUUID(&initData[readPosition])) {
    108         return android::ERROR_DRM_CANNOT_HANDLE;
    109     }
    110     readPosition += kSystemIdSize;
    111 
    112     // Read key ID count
    113     uint32_t keyIdCount;
    114     memcpy(&keyIdCount, &initData[readPosition], sizeof(keyIdCount));
    115     keyIdCount = ntohl(keyIdCount);
    116     readPosition += sizeof(keyIdCount);
    117     if (readPosition + ((uint64_t)keyIdCount * kKeyIdSize) !=
    118             initData.size() - sizeof(uint32_t)) {
    119         return android::ERROR_DRM_CANNOT_HANDLE;
    120     }
    121 
    122     // Calculate the key ID offsets
    123     for (uint32_t i = 0; i < keyIdCount; ++i) {
    124         size_t keyIdPosition = readPosition + (i * kKeyIdSize);
    125         keyIds->push(&initData[keyIdPosition]);
    126     }
    127     return android::OK;
    128 }
    129 
    130 String8 InitDataParser::generateRequest(const Vector<const uint8_t*>& keyIds) {
    131     const String8 kRequestPrefix("{\"kids\":[");
    132     const String8 kRequestSuffix("],\"type\":\"temporary\"}");
    133     const String8 kBase64Padding("=");
    134 
    135     String8 request(kRequestPrefix);
    136     AString encodedId;
    137     for (size_t i = 0; i < keyIds.size(); ++i) {
    138         encodedId.clear();
    139         android::encodeBase64Url(keyIds[i], kKeyIdSize, &encodedId);
    140         if (i != 0) {
    141             request.append(",");
    142         }
    143         request.appendFormat("\"%s\"", encodedId.c_str());
    144     }
    145     request.append(kRequestSuffix);
    146 
    147     // Android's Base64 encoder produces padding. EME forbids padding.
    148     request.removeAll(kBase64Padding);
    149     return request;
    150 }
    151 
    152 } // namespace clearkeydrm
    153