1 /*- 2 * Copyright (c) 2016 Christos Zoulas 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 15 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 16 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 17 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 18 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 19 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 20 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 21 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 22 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 23 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 24 * POSSIBILITY OF SUCH DAMAGE. 25 */ 26 /* 27 * DER (Distinguished Encoding Rules) Parser 28 * 29 * Sources: 30 * https://en.wikipedia.org/wiki/X.690 31 * http://fm4dd.com/openssl/certexamples.htm 32 * http://blog.engelke.com/2014/10/17/parsing-ber-and-der-encoded-asn-1-objects/ 33 */ 34 #ifndef TEST_DER 35 #include "file.h" 36 37 #ifndef lint 38 FILE_RCSID("@(#)$File: der.c,v 1.6 2016/04/21 14:26:03 christos Exp $") 39 #endif 40 #endif 41 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <sys/mman.h> 45 46 #include <stdio.h> 47 #include <fcntl.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <ctype.h> 51 52 #ifndef TEST_DER 53 #include "magic.h" 54 #include "der.h" 55 #else 56 #include <err.h> 57 #endif 58 59 #define DER_BAD ((uint32_t)-1) 60 61 #define DER_CLASS_UNIVERSAL 0 62 #define DER_CLASS_APPLICATION 1 63 #define DER_CLASS_CONTEXT 2 64 #define DER_CLASS_PRIVATE 3 65 #ifdef DEBUG_DER 66 static const char der_class[] = "UACP"; 67 #endif 68 69 #define DER_TYPE_PRIMITIVE 0 70 #define DER_TYPE_CONSTRUCTED 1 71 #ifdef DEBUG_DER 72 static const char der_type[] = "PC"; 73 #endif 74 75 #define DER_TAG_EOC 0x00 76 #define DER_TAG_BOOLEAN 0x01 77 #define DER_TAG_INTEGER 0x02 78 #define DER_TAG_BIT STRING 0x03 79 #define DER_TAG_OCTET_STRING 0x04 80 #define DER_TAG_NULL 0x05 81 #define DER_TAG_OBJECT_IDENTIFIER 0x06 82 #define DER_TAG_OBJECT_DESCRIPTOR 0x07 83 #define DER_TAG_EXTERNAL 0x08 84 #define DER_TAG_REAL 0x09 85 #define DER_TAG_ENUMERATED 0x0a 86 #define DER_TAG_EMBEDDED_PDV 0x0b 87 #define DER_TAG_UTF8_STRING 0x0c 88 #define DER_TAG_RELATIVE_OID 0x0d 89 #define DER_TAG_RESERVED_1 0x0e 90 #define DER_TAG_RESERVED_2 0x0f 91 #define DER_TAG_SEQUENCE 0x10 92 #define DER_TAG_SET 0x11 93 #define DER_TAG_NUMERIC_STRING 0x12 94 #define DER_TAG_PRINTABLE_STRING 0x13 95 #define DER_TAG_T61_STRING 0x14 96 #define DER_TAG_VIDEOTEX_STRING 0x15 97 #define DER_TAG_IA5_STRING 0x16 98 #define DER_TAG_UTCTIME 0x17 99 #define DER_TAG_GENERALIZED_TIME 0x18 100 #define DER_TAG_GRAPHIC_STRING 0x19 101 #define DER_TAG_VISIBLE_STRING 0x1a 102 #define DER_TAG_GENERAL_STRING 0x1b 103 #define DER_TAG_UNIVERSAL_STRING 0x1c 104 #define DER_TAG_CHARACTER_STRING 0x1d 105 #define DER_TAG_BMP_STRING 0x1e 106 #define DER_TAG_LONG 0x1f 107 108 static const char *der__tag[] = { 109 "eoc", "bool", "int", "bit_str", "octet_str", 110 "null", "obj_id", "obj_desc", "ext", "real", 111 "enum", "embed", "utf8_str", "oid", "res1", 112 "res2", "seq", "set", "num_str", "prt_str", 113 "t61_str", "vid_str", "ia5_str", "utc_time", 114 "gen_time", "gr_str", "vis_str", "gen_str", 115 "char_str", "bmp_str", "long" 116 }; 117 118 #ifdef DEBUG_DER 119 #define DPRINTF(a) printf a 120 #else 121 #define DPRINTF(a) 122 #endif 123 124 #ifdef TEST_DER 125 static uint8_t 126 getclass(uint8_t c) 127 { 128 return c >> 6; 129 } 130 131 static uint8_t 132 gettype(uint8_t c) 133 { 134 return (c >> 5) & 1; 135 } 136 #endif 137 138 static uint32_t 139 gettag(const uint8_t *c, size_t *p, size_t l) 140 { 141 uint32_t tag; 142 143 if (*p >= l) 144 return DER_BAD; 145 146 tag = c[(*p)++] & 0x1f; 147 148 if (tag != 0x1f) 149 return tag; 150 151 if (*p >= l) 152 return DER_BAD; 153 154 while (c[*p] >= 0x80) { 155 tag = tag * 128 + c[(*p)++] - 0x80; 156 if (*p >= l) 157 return DER_BAD; 158 } 159 return tag; 160 } 161 162 static uint32_t 163 getlength(const uint8_t *c, size_t *p, size_t l) 164 { 165 uint8_t digits, i; 166 size_t len; 167 168 if (*p >= l) 169 return DER_BAD; 170 171 digits = c[(*p)++]; 172 173 if ((digits & 0x80) == 0) 174 return digits; 175 176 digits &= 0x7f; 177 len = 0; 178 179 if (*p + digits >= l) 180 return DER_BAD; 181 182 for (i = 0; i < digits; i++) 183 len = (len << 8) | c[(*p)++]; 184 return len; 185 } 186 187 static const char * 188 der_tag(char *buf, size_t len, uint32_t tag) 189 { 190 if (tag < DER_TAG_LONG) 191 strlcpy(buf, der__tag[tag], len); 192 else 193 snprintf(buf, len, "%#x", tag); 194 return buf; 195 } 196 197 #ifndef TEST_DER 198 static int 199 der_data(char *buf, size_t blen, uint32_t tag, const void *q, uint32_t len) 200 { 201 const uint8_t *d = q; 202 switch (tag) { 203 case DER_TAG_PRINTABLE_STRING: 204 case DER_TAG_UTF8_STRING: 205 case DER_TAG_IA5_STRING: 206 case DER_TAG_UTCTIME: 207 return snprintf(buf, blen, "%.*s", len, (const char *)q); 208 default: 209 break; 210 } 211 212 for (uint32_t i = 0; i < len; i++) { 213 uint32_t z = i << 1; 214 if (z < blen - 2) 215 snprintf(buf + z, blen - z, "%.2x", d[i]); 216 } 217 return len * 2; 218 } 219 220 int32_t 221 der_offs(struct magic_set *ms, struct magic *m, size_t nbytes) 222 { 223 const uint8_t *b = CAST(const void *, ms->search.s); 224 size_t offs = 0, len = ms->search.rm_len ? ms->search.rm_len : nbytes; 225 226 if (gettag(b, &offs, len) == DER_BAD) 227 return -1; 228 DPRINTF(("%s1: %d %zu %u\n", __func__, ms->offset, offs, m->offset)); 229 230 uint32_t tlen = getlength(b, &offs, len); 231 if (tlen == DER_BAD) 232 return -1; 233 DPRINTF(("%s2: %d %zu %u\n", __func__, ms->offset, offs, tlen)); 234 235 offs += ms->offset + m->offset; 236 DPRINTF(("cont_level = %d\n", m->cont_level)); 237 #ifdef DEBUG_DER 238 for (size_t i = 0; i < m->cont_level; i++) 239 printf("cont_level[%zu] = %u\n", i, ms->c.li[i].off); 240 #endif 241 if (m->cont_level != 0) { 242 if (offs + tlen > nbytes) 243 return DER_BAD; 244 ms->c.li[m->cont_level - 1].off = offs + tlen; 245 DPRINTF(("cont_level[%u] = %u\n", m->cont_level - 1, 246 ms->c.li[m->cont_level - 1].off)); 247 } 248 return offs; 249 } 250 251 int 252 der_cmp(struct magic_set *ms, struct magic *m) 253 { 254 const uint8_t *b = CAST(const void *, ms->search.s); 255 const char *s = m->value.s; 256 size_t offs = 0, len = ms->search.s_len; 257 uint32_t tag, tlen; 258 char buf[128]; 259 260 tag = gettag(b, &offs, len); 261 if (tag == DER_BAD) 262 return -1; 263 264 tlen = getlength(b, &offs, len); 265 if (tlen == DER_BAD) 266 return -1; 267 268 der_tag(buf, sizeof(buf), tag); 269 if ((ms->flags & MAGIC_DEBUG) != 0) 270 fprintf(stderr, "%s: tag %p got=%s exp=%s\n", __func__, b, 271 buf, s); 272 size_t slen = strlen(buf); 273 274 if (strncmp(buf, s, slen) != 0) 275 return 0; 276 277 s += slen; 278 279 again: 280 switch (*s) { 281 case '\0': 282 return 1; 283 case '=': 284 s++; 285 goto val; 286 default: 287 if (!isdigit((unsigned char)*s)) 288 return 0; 289 290 slen = 0; 291 do 292 slen = slen * 10 + *s - '0'; 293 while (isdigit((unsigned char)*++s)); 294 if ((ms->flags & MAGIC_DEBUG) != 0) 295 fprintf(stderr, "%s: len %zu %u\n", __func__, 296 slen, tlen); 297 if (tlen != slen) 298 return 0; 299 goto again; 300 } 301 val: 302 DPRINTF(("%s: before data %zu %u\n", __func__, offs, tlen)); 303 der_data(buf, sizeof(buf), tag, b + offs, tlen); 304 if ((ms->flags & MAGIC_DEBUG) != 0) 305 fprintf(stderr, "%s: data %s %s\n", __func__, buf, s); 306 if (strcmp(buf, s) != 0 && strcmp("x", s) != 0) 307 return 0; 308 strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s)); 309 return 1; 310 } 311 #endif 312 313 #ifdef TEST_DER 314 static void 315 printtag(uint32_t tag, const void *q, uint32_t len) 316 { 317 const uint8_t *d = q; 318 switch (tag) { 319 case DER_TAG_PRINTABLE_STRING: 320 case DER_TAG_UTF8_STRING: 321 printf("%.*s\n", len, (const char *)q); 322 return; 323 default: 324 break; 325 } 326 327 for (uint32_t i = 0; i < len; i++) 328 printf("%.2x", d[i]); 329 printf("\n"); 330 } 331 332 static void 333 printdata(size_t level, const void *v, size_t x, size_t l) 334 { 335 const uint8_t *p = v, *ep = p + l; 336 size_t ox; 337 char buf[128]; 338 339 while (p + x < ep) { 340 const uint8_t *q; 341 uint8_t c = getclass(p[x]); 342 uint8_t t = gettype(p[x]); 343 ox = x; 344 if (x != 0) 345 printf("%.2x %.2x %.2x\n", p[x - 1], p[x], p[x + 1]); 346 uint32_t tag = gettag(p, &x, ep - p + x); 347 if (p + x >= ep) 348 break; 349 uint32_t len = getlength(p, &x, ep - p + x); 350 351 printf("%zu %zu-%zu %c,%c,%s,%u:", level, ox, x, 352 der_class[c], der_type[t], 353 der_tag(buf, sizeof(buf), tag), len); 354 q = p + x; 355 if (p + len > ep) 356 errx(EXIT_FAILURE, "corrupt der"); 357 printtag(tag, q, len); 358 if (t != DER_TYPE_PRIMITIVE) 359 printdata(level + 1, p, x, len + x); 360 x += len; 361 } 362 } 363 364 int 365 main(int argc, char *argv[]) 366 { 367 int fd; 368 struct stat st; 369 size_t l; 370 void *p; 371 372 if ((fd = open(argv[1], O_RDONLY)) == -1) 373 err(EXIT_FAILURE, "open `%s'", argv[1]); 374 if (fstat(fd, &st) == -1) 375 err(EXIT_FAILURE, "stat `%s'", argv[1]); 376 l = (size_t)st.st_size; 377 if ((p = mmap(NULL, l, PROT_READ, MAP_FILE, fd, 0)) == MAP_FAILED) 378 err(EXIT_FAILURE, "mmap `%s'", argv[1]); 379 380 printdata(0, p, 0, l); 381 munmap(p, l); 382 return 0; 383 } 384 #endif 385