1 /*
2 *
3 * Copyright 2017, The Android Open Source Project
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 #include <teeui/cbor.h>
19
20 namespace teeui {
21 namespace cbor {
22
23 namespace {
24
getByte(const uint64_t & v,const uint8_t index)25 inline uint8_t getByte(const uint64_t& v, const uint8_t index) {
26 return (v >> (index * 8)) & 0xff;
27 }
28
writeBytes(WriteState state,uint64_t value,uint8_t size)29 WriteState writeBytes(WriteState state, uint64_t value, uint8_t size) {
30 auto pos = state.data_;
31 if (!(state += size)) return state;
32 switch (size) {
33 case 8:
34 *pos++ = getByte(value, 7);
35 *pos++ = getByte(value, 6);
36 *pos++ = getByte(value, 5);
37 *pos++ = getByte(value, 4);
38 [[fallthrough]];
39 case 4:
40 *pos++ = getByte(value, 3);
41 *pos++ = getByte(value, 2);
42 [[fallthrough]];
43 case 2:
44 *pos++ = getByte(value, 1);
45 [[fallthrough]];
46 case 1:
47 *pos++ = getByte(value, 0);
48 break;
49 default:
50 state.error_ = Error::MALFORMED;
51 }
52 return state;
53 }
54
55 } // anonymous namespace
56
writeHeader(WriteState wState,Type type,const uint64_t value)57 WriteState writeHeader(WriteState wState, Type type, const uint64_t value) {
58 if (!wState) return wState;
59 uint8_t& header = *wState.data_;
60 if (!++wState) return wState;
61 header = static_cast<uint8_t>(type) << 5;
62 if (value < 24) {
63 header |= static_cast<uint8_t>(value);
64 } else if (value < 0x100) {
65 header |= 24;
66 wState = writeBytes(wState, value, 1);
67 } else if (value < 0x10000) {
68 header |= 25;
69 wState = writeBytes(wState, value, 2);
70 } else if (value < 0x100000000) {
71 header |= 26;
72 wState = writeBytes(wState, value, 4);
73 } else {
74 header |= 27;
75 wState = writeBytes(wState, value, 8);
76 }
77 return wState;
78 }
79
byteCount(char c)80 static size_t byteCount(char c) {
81 if ((0xc0 & c) == 0x80) {
82 return 0; // this is a multibyte payload byte
83 } else if (0x80 & c) {
84 /*
85 * CLZ - count leading zeroes.
86 * __builtin_clz promotes the argument to unsigned int.
87 * We invert c to turn leading ones into leading zeroes.
88 * We subtract additional leading zeroes due to the type promotion from the result.
89 */
90 return __builtin_clz((unsigned char)(~c)) - (sizeof(unsigned int) * 8 - 8);
91 } else {
92 return 1;
93 }
94 }
95
checkUTF8Copy(const char * begin,const char * const end,uint8_t * out)96 bool checkUTF8Copy(const char* begin, const char* const end, uint8_t* out) {
97 while (begin != end) {
98 auto bc = byteCount(*begin);
99 // if the string ends in the middle of a multi byte char it is invalid
100 if (begin + bc > end) return false;
101 switch (bc) {
102 case 4:
103 if (out) *out++ = *reinterpret_cast<const uint8_t*>(begin++);
104 [[fallthrough]];
105 case 3:
106 if (out) *out++ = *reinterpret_cast<const uint8_t*>(begin++);
107 [[fallthrough]];
108 case 2:
109 if (out) *out++ = *reinterpret_cast<const uint8_t*>(begin++);
110 [[fallthrough]];
111 case 1:
112 if (out) *out++ = *reinterpret_cast<const uint8_t*>(begin++);
113 break;
114 default:
115 // case 0 means we encounted a payload byte when we expected a header.
116 // case > 4 is malformed.
117 return false;
118 }
119 }
120 return true;
121 }
122
123 } // namespace cbor
124 } // namespace teeui
125