1 /* 2 * Copyright (C) 2013 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 #include "asn1_decoder.h" 18 19 #include <stdint.h> 20 21 int asn1_context::peek_byte() const { 22 if (length_ == 0) { 23 return -1; 24 } 25 return *p_; 26 } 27 28 int asn1_context::get_byte() { 29 if (length_ == 0) { 30 return -1; 31 } 32 33 int byte = *p_; 34 p_++; 35 length_--; 36 return byte; 37 } 38 39 bool asn1_context::skip_bytes(size_t num_skip) { 40 if (length_ < num_skip) { 41 return false; 42 } 43 p_ += num_skip; 44 length_ -= num_skip; 45 return true; 46 } 47 48 bool asn1_context::decode_length(size_t* out_len) { 49 int num_octets = get_byte(); 50 if (num_octets == -1) { 51 return false; 52 } 53 if ((num_octets & 0x80) == 0x00) { 54 *out_len = num_octets; 55 return true; 56 } 57 num_octets &= kMaskTag; 58 if (static_cast<size_t>(num_octets) >= sizeof(size_t)) { 59 return false; 60 } 61 size_t length = 0; 62 for (int i = 0; i < num_octets; ++i) { 63 int byte = get_byte(); 64 if (byte == -1) { 65 return false; 66 } 67 length <<= 8; 68 length += byte; 69 } 70 *out_len = length; 71 return true; 72 } 73 74 /** 75 * Returns the constructed type and advances the pointer. E.g. A0 -> 0 76 */ 77 asn1_context* asn1_context::asn1_constructed_get() { 78 int type = get_byte(); 79 if (type == -1 || (type & kMaskConstructed) != kTagConstructed) { 80 return nullptr; 81 } 82 size_t length; 83 if (!decode_length(&length) || length > length_) { 84 return nullptr; 85 } 86 asn1_context* app_ctx = new asn1_context(p_, length); 87 app_ctx->app_type_ = type & kMaskAppType; 88 return app_ctx; 89 } 90 91 bool asn1_context::asn1_constructed_skip_all() { 92 int byte = peek_byte(); 93 while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) { 94 skip_bytes(1); 95 size_t length; 96 if (!decode_length(&length) || !skip_bytes(length)) { 97 return false; 98 } 99 byte = peek_byte(); 100 } 101 return byte != -1; 102 } 103 104 int asn1_context::asn1_constructed_type() const { 105 return app_type_; 106 } 107 108 asn1_context* asn1_context::asn1_sequence_get() { 109 if ((get_byte() & kMaskTag) != kTagSequence) { 110 return nullptr; 111 } 112 size_t length; 113 if (!decode_length(&length) || length > length_) { 114 return nullptr; 115 } 116 return new asn1_context(p_, length); 117 } 118 119 asn1_context* asn1_context::asn1_set_get() { 120 if ((get_byte() & kMaskTag) != kTagSet) { 121 return nullptr; 122 } 123 size_t length; 124 if (!decode_length(&length) || length > length_) { 125 return nullptr; 126 } 127 return new asn1_context(p_, length); 128 } 129 130 bool asn1_context::asn1_sequence_next() { 131 size_t length; 132 if (get_byte() == -1 || !decode_length(&length) || !skip_bytes(length)) { 133 return false; 134 } 135 return true; 136 } 137 138 bool asn1_context::asn1_oid_get(const uint8_t** oid, size_t* length) { 139 if (get_byte() != kTagOid) { 140 return false; 141 } 142 if (!decode_length(length) || *length == 0 || *length > length_) { 143 return false; 144 } 145 *oid = p_; 146 return true; 147 } 148 149 bool asn1_context::asn1_octet_string_get(const uint8_t** octet_string, size_t* length) { 150 if (get_byte() != kTagOctetString) { 151 return false; 152 } 153 if (!decode_length(length) || *length == 0 || *length > length_) { 154 return false; 155 } 156 *octet_string = p_; 157 return true; 158 } 159
