1 /*
2 * Copyright (C) 2017 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 "ecm_generator"
19 #include "ecm_generator.h"
20
21 #include <string.h>
22 #include <algorithm>
23 #include <endian.h>
24
25 #include "protos/license_protos.pb.h"
26
27 #include <media/stagefright/foundation/ADebug.h>
28 #include <media/stagefright/MediaErrors.h>
29 #include <openssl/aes.h>
30 #include <utils/Log.h>
31
32 namespace android {
33 namespace clearkeycas {
34
35 // These constants are internal to this module.
36 const uint16_t kEcmClearFieldsSize = 16;
37 const uint32_t kContentKeyByteSize = 16;
38 const uint16_t kTotalEcmSize =
39 kEcmClearFieldsSize + kContentKeyByteSize; // clear fields + clear key
40
41 const uint32_t kKeyLength = 16;
42
43 #define UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32_t *>(_p))
44
Load32(const void * p)45 static uint32_t Load32(const void *p) {
46 return ntohl(UNALIGNED_LOAD32(p));
47 }
48
LoadNext32(const uint8_t ** pptr)49 static uint32_t LoadNext32(const uint8_t** pptr) {
50 CHECK(pptr);
51 CHECK(*pptr);
52 const uint8_t* p = *pptr;
53 *pptr += sizeof(uint32_t);
54 return Load32(p);
55 }
56
57 namespace ecm_generator {
58
DecodeECM(const sp<ABuffer> & ecm,Asset * asset,sp<ABuffer> * content_key,DefaultEcmFields * default_fields)59 status_t DecodeECM(const sp<ABuffer>& ecm, Asset* asset,
60 sp<ABuffer> *content_key, DefaultEcmFields* default_fields) {
61 CHECK(asset);
62 CHECK(content_key);
63 CHECK(default_fields);
64
65 status_t status = DecodeECMClearFields(ecm, asset, default_fields);
66 if (status != OK) {
67 return status;
68 }
69
70 const uint8_t* ptr = ecm->data() + kEcmClearFieldsSize;
71 *content_key = new ABuffer(kContentKeyByteSize);
72 memcpy((*content_key)->data(), ptr, kContentKeyByteSize);
73
74 return OK;
75 }
76
DecodeECMClearFields(const sp<ABuffer> & ecm,Asset * asset,DefaultEcmFields * default_fields)77 status_t DecodeECMClearFields(const sp<ABuffer>& ecm, Asset* asset,
78 DefaultEcmFields* default_fields) {
79 CHECK(asset);
80 CHECK(default_fields);
81
82 if (ecm->size() < kTotalEcmSize) {
83 ALOGE("Short ECM: expected_length=%d, actual_length=%zu",
84 kTotalEcmSize, ecm->size());
85 return BAD_VALUE;
86 }
87 const uint8_t* ptr = ecm->data();
88 default_fields->old_version = LoadNext32(&ptr);
89 default_fields->clear_lead = LoadNext32(&ptr);
90 default_fields->system_id = LoadNext32(&ptr);
91 // The real ecm version is hidden in the system id.
92 default_fields->ecm_version = (default_fields->system_id >> 24) & 0xFF;
93 default_fields->system_id &= 0x00FFFFFF;
94 if (default_fields->system_id == 0) {
95 ALOGE("Ecm has invalid system_id 0");
96 return CLEARKEY_STATUS_INVALIDSYSTEMID;
97 }
98 asset->set_id(LoadNext32(&ptr));
99 if (asset->id() == 0) {
100 ALOGE("Ecm has invalid asset_id 0");
101 return CLEARKEY_STATUS_INVALIDASSETID;
102 }
103 return OK;
104 }
105
106 } // namespace ecm_generator
107 } // namespace clearkeycas
108 } // namespace android
109