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 #define UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32_t *>(_p))
42
Load32(const void * p)43 static uint32_t Load32(const void *p) {
44 return ntohl(UNALIGNED_LOAD32(p));
45 }
46
LoadNext32(const uint8_t ** pptr)47 static uint32_t LoadNext32(const uint8_t** pptr) {
48 CHECK(pptr);
49 CHECK(*pptr);
50 const uint8_t* p = *pptr;
51 *pptr += sizeof(uint32_t);
52 return Load32(p);
53 }
54
55 namespace ecm_generator {
56
DecodeECM(const sp<ABuffer> & ecm,Asset * asset,sp<ABuffer> * content_key,DefaultEcmFields * default_fields)57 status_t DecodeECM(const sp<ABuffer>& ecm, Asset* asset,
58 sp<ABuffer> *content_key, DefaultEcmFields* default_fields) {
59 CHECK(asset);
60 CHECK(content_key);
61 CHECK(default_fields);
62
63 status_t status = DecodeECMClearFields(ecm, asset, default_fields);
64 if (status != OK) {
65 return status;
66 }
67
68 const uint8_t* ptr = ecm->data() + kEcmClearFieldsSize;
69 *content_key = new ABuffer(kContentKeyByteSize);
70 memcpy((*content_key)->data(), ptr, kContentKeyByteSize);
71
72 return OK;
73 }
74
DecodeECMClearFields(const sp<ABuffer> & ecm,Asset * asset,DefaultEcmFields * default_fields)75 status_t DecodeECMClearFields(const sp<ABuffer>& ecm, Asset* asset,
76 DefaultEcmFields* default_fields) {
77 CHECK(asset);
78 CHECK(default_fields);
79
80 if (ecm->size() < kTotalEcmSize) {
81 ALOGE("Short ECM: expected_length=%d, actual_length=%zu",
82 kTotalEcmSize, ecm->size());
83 return BAD_VALUE;
84 }
85 const uint8_t* ptr = ecm->data();
86 default_fields->old_version = LoadNext32(&ptr);
87 default_fields->clear_lead = LoadNext32(&ptr);
88 default_fields->system_id = LoadNext32(&ptr);
89 // The real ecm version is hidden in the system id.
90 default_fields->ecm_version = (default_fields->system_id >> 24) & 0xFF;
91 default_fields->system_id &= 0x00FFFFFF;
92 if (default_fields->system_id == 0) {
93 ALOGE("Ecm has invalid system_id 0");
94 return CLEARKEY_STATUS_INVALIDSYSTEMID;
95 }
96 asset->set_id(LoadNext32(&ptr));
97 if (asset->id() == 0) {
98 ALOGE("Ecm has invalid asset_id 0");
99 return CLEARKEY_STATUS_INVALIDASSETID;
100 }
101 return OK;
102 }
103
104 } // namespace ecm_generator
105 } // namespace clearkeycas
106 } // namespace android
107