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 "Utils.h"
31
32 namespace clearkeydrm {
33
34 using android::AString;
35 using android::String8;
36 using android::Vector;
37
38 namespace {
39 const size_t kKeyIdSize = 16;
40 const size_t kSystemIdSize = 16;
41 }
42
parse(const Vector<uint8_t> & initData,const String8 & initDataType,Vector<uint8_t> * licenseRequest)43 android::status_t InitDataParser::parse(const Vector<uint8_t>& initData,
44 const String8& initDataType,
45 Vector<uint8_t>* licenseRequest) {
46 // Build a list of the key IDs
47 Vector<const uint8_t*> keyIds;
48 if (initDataType == "cenc") {
49 android::status_t res = parsePssh(initData, &keyIds);
50 if (res != android::OK) {
51 return res;
52 }
53 } else if (initDataType == "webm") {
54 // WebM "init data" is just a single key ID
55 if (initData.size() != kKeyIdSize) {
56 return android::ERROR_DRM_CANNOT_HANDLE;
57 }
58 keyIds.push(initData.array());
59 } else {
60 return android::ERROR_DRM_CANNOT_HANDLE;
61 }
62
63 // Build the request
64 String8 requestJson = generateRequest(keyIds);
65 licenseRequest->clear();
66 licenseRequest->appendArray(
67 reinterpret_cast<const uint8_t*>(requestJson.string()),
68 requestJson.size());
69 return android::OK;
70 }
71
parsePssh(const Vector<uint8_t> & initData,Vector<const uint8_t * > * keyIds)72 android::status_t InitDataParser::parsePssh(const Vector<uint8_t>& initData,
73 Vector<const uint8_t*>* keyIds) {
74 size_t readPosition = 0;
75
76 // Validate size field
77 uint32_t expectedSize = initData.size();
78 expectedSize = htonl(expectedSize);
79 if (memcmp(&initData[readPosition], &expectedSize,
80 sizeof(expectedSize)) != 0) {
81 return android::ERROR_DRM_CANNOT_HANDLE;
82 }
83 readPosition += sizeof(expectedSize);
84
85 // Validate PSSH box identifier
86 const char psshIdentifier[4] = {'p', 's', 's', 'h'};
87 if (memcmp(&initData[readPosition], psshIdentifier,
88 sizeof(psshIdentifier)) != 0) {
89 return android::ERROR_DRM_CANNOT_HANDLE;
90 }
91 readPosition += sizeof(psshIdentifier);
92
93 // Validate EME version number
94 const uint8_t psshVersion1[4] = {1, 0, 0, 0};
95 if (memcmp(&initData[readPosition], psshVersion1,
96 sizeof(psshVersion1)) != 0) {
97 return android::ERROR_DRM_CANNOT_HANDLE;
98 }
99 readPosition += sizeof(psshVersion1);
100
101 // Validate system ID
102 if (!isClearKeyUUID(&initData[readPosition])) {
103 return android::ERROR_DRM_CANNOT_HANDLE;
104 }
105 readPosition += kSystemIdSize;
106
107 // Read key ID count
108 uint32_t keyIdCount;
109 memcpy(&keyIdCount, &initData[readPosition], sizeof(keyIdCount));
110 keyIdCount = ntohl(keyIdCount);
111 readPosition += sizeof(keyIdCount);
112 if (readPosition + (keyIdCount * kKeyIdSize) !=
113 initData.size() - sizeof(uint32_t)) {
114 return android::ERROR_DRM_CANNOT_HANDLE;
115 }
116
117 // Calculate the key ID offsets
118 for (uint32_t i = 0; i < keyIdCount; ++i) {
119 size_t keyIdPosition = readPosition + (i * kKeyIdSize);
120 keyIds->push(&initData[keyIdPosition]);
121 }
122 return android::OK;
123 }
124
generateRequest(const Vector<const uint8_t * > & keyIds)125 String8 InitDataParser::generateRequest(const Vector<const uint8_t*>& keyIds) {
126 const String8 kRequestPrefix("{\"kids\":[");
127 const String8 kRequestSuffix("],\"type\":\"temporary\"}");
128 const String8 kBase64Padding("=");
129
130 String8 request(kRequestPrefix);
131 AString encodedId;
132 for (size_t i = 0; i < keyIds.size(); ++i) {
133 encodedId.clear();
134 android::encodeBase64(keyIds[i], kKeyIdSize, &encodedId);
135 if (i != 0) {
136 request.append(",");
137 }
138 request.appendFormat("\"%s\"", encodedId.c_str());
139 }
140 request.append(kRequestSuffix);
141
142 // Android's Base64 encoder produces padding. EME forbids padding.
143 request.removeAll(kBase64Padding);
144 return request;
145 }
146
147 } // namespace clearkeydrm
148