1 /* Copyright (c) 2014, Google Inc. 2 * 3 * Permission to use, copy, modify, and/or distribute this software for any 4 * purpose with or without fee is hereby granted, provided that the above 5 * copyright notice and this permission notice appear in all copies. 6 * 7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION 12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ 14 15 #include <openssl/bytestring.h> 16 17 #include <assert.h> 18 #include <string.h> 19 20 #include "internal.h" 21 #include "../internal.h" 22 23 24 /* kMaxDepth is a just a sanity limit. The code should be such that the length 25 * of the input being processes always decreases. None the less, a very large 26 * input could otherwise cause the stack to overflow. */ 27 static const unsigned kMaxDepth = 2048; 28 29 /* is_string_type returns one if |tag| is a string type and zero otherwise. It 30 * ignores the constructed bit. */ 31 static int is_string_type(unsigned tag) { 32 if ((tag & 0xc0) != 0) { 33 return 0; 34 } 35 switch (tag & 0x1f) { 36 case CBS_ASN1_BITSTRING: 37 case CBS_ASN1_OCTETSTRING: 38 case CBS_ASN1_UTF8STRING: 39 case CBS_ASN1_NUMERICSTRING: 40 case CBS_ASN1_PRINTABLESTRING: 41 case CBS_ASN1_T61STRING: 42 case CBS_ASN1_VIDEOTEXSTRING: 43 case CBS_ASN1_IA5STRING: 44 case CBS_ASN1_GRAPHICSTRING: 45 case CBS_ASN1_VISIBLESTRING: 46 case CBS_ASN1_GENERALSTRING: 47 case CBS_ASN1_UNIVERSALSTRING: 48 case CBS_ASN1_BMPSTRING: 49 return 1; 50 default: 51 return 0; 52 } 53 } 54 55 /* cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found| 56 * depending on whether an indefinite length element or constructed string was 57 * found. The value of |orig_in| is not changed. It returns one on success (i.e. 58 * |*ber_found| was set) and zero on error. */ 59 static int cbs_find_ber(const CBS *orig_in, char *ber_found, unsigned depth) { 60 CBS in; 61 62 if (depth > kMaxDepth) { 63 return 0; 64 } 65 66 CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in)); 67 *ber_found = 0; 68 69 while (CBS_len(&in) > 0) { 70 CBS contents; 71 unsigned tag; 72 size_t header_len; 73 74 if (!CBS_get_any_ber_asn1_element(&in, &contents, &tag, &header_len)) { 75 return 0; 76 } 77 if (CBS_len(&contents) == header_len && 78 header_len > 0 && 79 CBS_data(&contents)[header_len-1] == 0x80) { 80 /* Found an indefinite-length element. */ 81 *ber_found = 1; 82 return 1; 83 } 84 if (tag & CBS_ASN1_CONSTRUCTED) { 85 if (is_string_type(tag)) { 86 /* Constructed strings are only legal in BER and require conversion. */ 87 *ber_found = 1; 88 return 1; 89 } 90 if (!CBS_skip(&contents, header_len) || 91 !cbs_find_ber(&contents, ber_found, depth + 1)) { 92 return 0; 93 } 94 } 95 } 96 97 return 1; 98 } 99 100 /* is_eoc returns true if |header_len| and |contents|, as returned by 101 * |CBS_get_any_ber_asn1_element|, indicate an "end of contents" (EOC) value. */ 102 static char is_eoc(size_t header_len, CBS *contents) { 103 return header_len == 2 && CBS_len(contents) == 2 && 104 OPENSSL_memcmp(CBS_data(contents), "\x00\x00", 2) == 0; 105 } 106 107 /* cbs_convert_ber reads BER data from |in| and writes DER data to |out|. If 108 * |string_tag| is non-zero, then all elements must match |string_tag| up to the 109 * constructed bit and primitive element bodies are written to |out| without 110 * element headers. This is used when concatenating the fragments of a 111 * constructed string. If |looking_for_eoc| is set then any EOC elements found 112 * will cause the function to return after consuming it. It returns one on 113 * success and zero on error. */ 114 static int cbs_convert_ber(CBS *in, CBB *out, unsigned string_tag, 115 char looking_for_eoc, unsigned depth) { 116 assert(!(string_tag & CBS_ASN1_CONSTRUCTED)); 117 118 if (depth > kMaxDepth) { 119 return 0; 120 } 121 122 while (CBS_len(in) > 0) { 123 CBS contents; 124 unsigned tag, child_string_tag = string_tag; 125 size_t header_len; 126 CBB *out_contents, out_contents_storage; 127 128 if (!CBS_get_any_ber_asn1_element(in, &contents, &tag, &header_len)) { 129 return 0; 130 } 131 132 if (is_eoc(header_len, &contents)) { 133 return looking_for_eoc; 134 } 135 136 if (string_tag != 0) { 137 /* This is part of a constructed string. All elements must match 138 * |string_tag| up to the constructed bit and get appended to |out| 139 * without a child element. */ 140 if ((tag & ~CBS_ASN1_CONSTRUCTED) != string_tag) { 141 return 0; 142 } 143 out_contents = out; 144 } else { 145 unsigned out_tag = tag; 146 if ((tag & CBS_ASN1_CONSTRUCTED) && is_string_type(tag)) { 147 /* If a constructed string, clear the constructed bit and inform 148 * children to concatenate bodies. */ 149 out_tag &= ~CBS_ASN1_CONSTRUCTED; 150 child_string_tag = out_tag; 151 } 152 if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) { 153 return 0; 154 } 155 out_contents = &out_contents_storage; 156 } 157 158 if (CBS_len(&contents) == header_len && header_len > 0 && 159 CBS_data(&contents)[header_len - 1] == 0x80) { 160 /* This is an indefinite length element. */ 161 if (!cbs_convert_ber(in, out_contents, child_string_tag, 162 1 /* looking for eoc */, depth + 1) || 163 !CBB_flush(out)) { 164 return 0; 165 } 166 continue; 167 } 168 169 if (!CBS_skip(&contents, header_len)) { 170 return 0; 171 } 172 173 if (tag & CBS_ASN1_CONSTRUCTED) { 174 /* Recurse into children. */ 175 if (!cbs_convert_ber(&contents, out_contents, child_string_tag, 176 0 /* not looking for eoc */, depth + 1)) { 177 return 0; 178 } 179 } else { 180 /* Copy primitive contents as-is. */ 181 if (!CBB_add_bytes(out_contents, CBS_data(&contents), 182 CBS_len(&contents))) { 183 return 0; 184 } 185 } 186 187 if (!CBB_flush(out)) { 188 return 0; 189 } 190 } 191 192 return looking_for_eoc == 0; 193 } 194 195 int CBS_asn1_ber_to_der(CBS *in, uint8_t **out, size_t *out_len) { 196 CBB cbb; 197 198 /* First, do a quick walk to find any indefinite-length elements. Most of the 199 * time we hope that there aren't any and thus we can quickly return. */ 200 char conversion_needed; 201 if (!cbs_find_ber(in, &conversion_needed, 0)) { 202 return 0; 203 } 204 205 if (!conversion_needed) { 206 *out = NULL; 207 *out_len = 0; 208 return 1; 209 } 210 211 if (!CBB_init(&cbb, CBS_len(in)) || 212 !cbs_convert_ber(in, &cbb, 0, 0, 0) || 213 !CBB_finish(&cbb, out, out_len)) { 214 CBB_cleanup(&cbb); 215 return 0; 216 } 217 218 return 1; 219 } 220 221 int CBS_get_asn1_implicit_string(CBS *in, CBS *out, uint8_t **out_storage, 222 unsigned outer_tag, unsigned inner_tag) { 223 assert(!(outer_tag & CBS_ASN1_CONSTRUCTED)); 224 assert(!(inner_tag & CBS_ASN1_CONSTRUCTED)); 225 assert(is_string_type(inner_tag)); 226 227 if (CBS_peek_asn1_tag(in, outer_tag)) { 228 /* Normal implicitly-tagged string. */ 229 *out_storage = NULL; 230 return CBS_get_asn1(in, out, outer_tag); 231 } 232 233 /* Otherwise, try to parse an implicitly-tagged constructed string. 234 * |CBS_asn1_ber_to_der| is assumed to have run, so only allow one level deep 235 * of nesting. */ 236 CBB result; 237 CBS child; 238 if (!CBB_init(&result, CBS_len(in)) || 239 !CBS_get_asn1(in, &child, outer_tag | CBS_ASN1_CONSTRUCTED)) { 240 goto err; 241 } 242 243 while (CBS_len(&child) > 0) { 244 CBS chunk; 245 if (!CBS_get_asn1(&child, &chunk, inner_tag) || 246 !CBB_add_bytes(&result, CBS_data(&chunk), CBS_len(&chunk))) { 247 goto err; 248 } 249 } 250 251 uint8_t *data; 252 size_t len; 253 if (!CBB_finish(&result, &data, &len)) { 254 goto err; 255 } 256 257 CBS_init(out, data, len); 258 *out_storage = data; 259 return 1; 260 261 err: 262 CBB_cleanup(&result); 263 return 0; 264 } 265
