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
33namespace clearkeydrm {
34
35using android::AString;
36using android::String8;
37using android::Vector;
38
39namespace {
40    const size_t kKeyIdSize = 16;
41    const size_t kSystemIdSize = 16;
42}
43
44android::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
77android::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
130String8 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