1 /*
2 * Copyright (C) 2024 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16 #include "asn1_decoder.h"
17
18 #include <cctype>
19 #include <cstdio>
20 #include <securec.h>
21 #include "asn1_constants.h"
22 #include "asn1_utils.h"
23
24 namespace OHOS {
25 namespace Telephony {
Asn1Decoder(const std::vector<uint8_t> &src, uint32_t offset, uint32_t decodeLen)26 Asn1Decoder::Asn1Decoder(const std::vector<uint8_t> &src, uint32_t offset, uint32_t decodeLen)
27 {
28 TELEPHONY_LOGD("enter Asn1Decoder");
29 if ((offset > (std::numeric_limits<uint32_t>::max() - decodeLen)) || ((offset + decodeLen) > src.size())) {
30 TELEPHONY_LOGE("Out of the bounds: byteLen=%{public}zu, offset=%{public}u, decodeLen=%{public}u.",
31 src.size(), offset, decodeLen);
32 return;
33 }
34
35 srcData_ = src;
36 position_ = offset;
37 end_ = offset + decodeLen;
38
39 TELEPHONY_LOGD("byteLen:%{public}zu, offset:%{public}u, decodeLen:%{public}u", src.size(), offset, decodeLen);
40 }
41
Asn1HasNextNode()42 bool Asn1Decoder::Asn1HasNextNode()
43 {
44 return position_ < end_;
45 }
46
Asn1NextNode()47 std::shared_ptr<Asn1Node> Asn1Decoder::Asn1NextNode()
48 {
49 TELEPHONY_LOGD("enter Asn1NextNode");
50 if (end_ <= position_ || srcData_.empty()) {
51 TELEPHONY_LOGE("No bytes to parse.");
52 return nullptr;
53 }
54
55 uint32_t offset = position_;
56 uint32_t tagStart = offset;
57 if (offset >= srcData_.size()) {
58 return nullptr;
59 }
60 uint8_t byteTag = srcData_[offset];
61 offset++;
62 uint8_t lowFiveBit = 0x1F;
63 // the lower 5 bits of variable bitTag is tag number, 0x1F represent invalid val.
64 if ((byteTag & lowFiveBit) == lowFiveBit) {
65 while (offset < end_ && (static_cast<uint8_t>(srcData_[offset]) & BIT8_MASK) != 0) {
66 offset++;
67 }
68 offset++;
69 }
70 if (offset >= end_) {
71 TELEPHONY_LOGE("No bytes to parse.");
72 return nullptr;
73 }
74 int32_t tag = Asn1Utils::BytesToInt(srcData_, tagStart, offset - tagStart);
75 if (tag < 0) {
76 TELEPHONY_LOGE("Cannot parse tag at position: %{public}u", tagStart);
77 return nullptr;
78 }
79 return BuildAsn1Node(static_cast<uint32_t>(tag), offset, tagStart);
80 }
81
BuildAsn1Node(const uint32_t tag, uint32_t offset, uint32_t tagStart)82 std::shared_ptr<Asn1Node> Asn1Decoder::BuildAsn1Node(const uint32_t tag, uint32_t offset, uint32_t tagStart)
83 {
84 if (srcData_.empty() || offset >= srcData_.size()) {
85 TELEPHONY_LOGE("srcData_ is empty");
86 return nullptr;
87 }
88 uint32_t dataLen;
89 uint8_t byteLen = srcData_[offset];
90 offset++;
91 // The highest bit being 1 indicates that the following 7 bits represent the length of the length field.
92 if ((byteLen & BIT8_MASK) == 0) {
93 dataLen = static_cast<uint32_t>(byteLen);
94 } else {
95 uint32_t lenLen = static_cast<uint32_t>(byteLen & MAX_INT8);
96 if (offset + lenLen > end_) {
97 TELEPHONY_LOGE("Cannot parse tag at position: %{public}u", tagStart);
98 return nullptr;
99 }
100 dataLen = static_cast<uint32_t>(Asn1Utils::BytesToInt(srcData_, offset, lenLen));
101 offset += lenLen;
102 }
103 if (offset + dataLen > end_) {
104 TELEPHONY_LOGE("Incomplete data at position: offset=%{public}u, dataLen=%{public}u, leftLength=%{public}u.",
105 offset, dataLen, (end_ - offset));
106 return nullptr;
107 }
108 std::vector<uint8_t> byteStream(srcData_.begin() + offset, srcData_.begin() + offset + dataLen);
109 std::shared_ptr<Asn1Node> asn1Node = std::make_shared<Asn1Node>(tag, byteStream, 0, dataLen);
110 position_ = offset + dataLen;
111 return asn1Node;
112 }
113 } // namespace Telephony
114 }
115