der.c revision 309848
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 38FILE_RCSID("@(#)$File: der.c,v 1.10 2016/10/24 18:02:17 christos Exp $") 39#endif 40#endif 41 42#include <sys/types.h> 43 44#include <stdio.h> 45#include <fcntl.h> 46#include <stdlib.h> 47#include <string.h> 48#include <ctype.h> 49 50#ifndef TEST_DER 51#include "magic.h" 52#include "der.h" 53#else 54#include <sys/mman.h> 55#include <sys/stat.h> 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 66static const char der_class[] = "UACP"; 67#endif 68 69#define DER_TYPE_PRIMITIVE 0 70#define DER_TYPE_CONSTRUCTED 1 71#ifdef DEBUG_DER 72static 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 108static 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 125static uint8_t 126getclass(uint8_t c) 127{ 128 return c >> 6; 129} 130 131static uint8_t 132gettype(uint8_t c) 133{ 134 return (c >> 5) & 1; 135} 136#endif 137 138static uint32_t 139gettag(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 162static uint32_t 163getlength(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 if (*p + len >= l) 185 return DER_BAD; 186 return len; 187} 188 189static const char * 190der_tag(char *buf, size_t len, uint32_t tag) 191{ 192 if (tag < DER_TAG_LONG) 193 strlcpy(buf, der__tag[tag], len); 194 else 195 snprintf(buf, len, "%#x", tag); 196 return buf; 197} 198 199#ifndef TEST_DER 200static int 201der_data(char *buf, size_t blen, uint32_t tag, const void *q, uint32_t len) 202{ 203 const uint8_t *d = CAST(const uint8_t *, q); 204 switch (tag) { 205 case DER_TAG_PRINTABLE_STRING: 206 case DER_TAG_UTF8_STRING: 207 case DER_TAG_IA5_STRING: 208 case DER_TAG_UTCTIME: 209 return snprintf(buf, blen, "%.*s", len, (const char *)q); 210 default: 211 break; 212 } 213 214 for (uint32_t i = 0; i < len; i++) { 215 uint32_t z = i << 1; 216 if (z < blen - 2) 217 snprintf(buf + z, blen - z, "%.2x", d[i]); 218 } 219 return len * 2; 220} 221 222int32_t 223der_offs(struct magic_set *ms, struct magic *m, size_t nbytes) 224{ 225 const uint8_t *b = RCAST(const uint8_t *, ms->search.s); 226 size_t offs = 0, len = ms->search.s_len ? ms->search.s_len : nbytes; 227 228 if (gettag(b, &offs, len) == DER_BAD) 229 return -1; 230 DPRINTF(("%s1: %d %zu %u\n", __func__, ms->offset, offs, m->offset)); 231 232 uint32_t tlen = getlength(b, &offs, len); 233 if (tlen == DER_BAD) 234 return -1; 235 DPRINTF(("%s2: %d %zu %u\n", __func__, ms->offset, offs, tlen)); 236 237 offs += ms->offset + m->offset; 238 DPRINTF(("cont_level = %d\n", m->cont_level)); 239#ifdef DEBUG_DER 240 for (size_t i = 0; i < m->cont_level; i++) 241 printf("cont_level[%zu] = %u\n", i, ms->c.li[i].off); 242#endif 243 if (m->cont_level != 0) { 244 if (offs + tlen > nbytes) 245 return DER_BAD; 246 ms->c.li[m->cont_level - 1].off = offs + tlen; 247 DPRINTF(("cont_level[%u] = %u\n", m->cont_level - 1, 248 ms->c.li[m->cont_level - 1].off)); 249 } 250 return offs; 251} 252 253int 254der_cmp(struct magic_set *ms, struct magic *m) 255{ 256 const uint8_t *b = RCAST(const uint8_t *, ms->search.s); 257 const char *s = m->value.s; 258 size_t offs = 0, len = ms->search.s_len; 259 uint32_t tag, tlen; 260 char buf[128]; 261 262 tag = gettag(b, &offs, len); 263 if (tag == DER_BAD) 264 return -1; 265 266 tlen = getlength(b, &offs, len); 267 if (tlen == DER_BAD) 268 return -1; 269 270 der_tag(buf, sizeof(buf), tag); 271 if ((ms->flags & MAGIC_DEBUG) != 0) 272 fprintf(stderr, "%s: tag %p got=%s exp=%s\n", __func__, b, 273 buf, s); 274 size_t slen = strlen(buf); 275 276 if (strncmp(buf, s, slen) != 0) 277 return 0; 278 279 s += slen; 280 281again: 282 switch (*s) { 283 case '\0': 284 return 1; 285 case '=': 286 s++; 287 goto val; 288 default: 289 if (!isdigit((unsigned char)*s)) 290 return 0; 291 292 slen = 0; 293 do 294 slen = slen * 10 + *s - '0'; 295 while (isdigit((unsigned char)*++s)); 296 if ((ms->flags & MAGIC_DEBUG) != 0) 297 fprintf(stderr, "%s: len %zu %u\n", __func__, 298 slen, tlen); 299 if (tlen != slen) 300 return 0; 301 goto again; 302 } 303val: 304 DPRINTF(("%s: before data %zu %u\n", __func__, offs, tlen)); 305 der_data(buf, sizeof(buf), tag, b + offs, tlen); 306 if ((ms->flags & MAGIC_DEBUG) != 0) 307 fprintf(stderr, "%s: data %s %s\n", __func__, buf, s); 308 if (strcmp(buf, s) != 0 && strcmp("x", s) != 0) 309 return 0; 310 strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s)); 311 return 1; 312} 313#endif 314 315#ifdef TEST_DER 316static void 317printtag(uint32_t tag, const void *q, uint32_t len) 318{ 319 const uint8_t *d = q; 320 switch (tag) { 321 case DER_TAG_PRINTABLE_STRING: 322 case DER_TAG_UTF8_STRING: 323 printf("%.*s\n", len, (const char *)q); 324 return; 325 default: 326 break; 327 } 328 329 for (uint32_t i = 0; i < len; i++) 330 printf("%.2x", d[i]); 331 printf("\n"); 332} 333 334static void 335printdata(size_t level, const void *v, size_t x, size_t l) 336{ 337 const uint8_t *p = v, *ep = p + l; 338 size_t ox; 339 char buf[128]; 340 341 while (p + x < ep) { 342 const uint8_t *q; 343 uint8_t c = getclass(p[x]); 344 uint8_t t = gettype(p[x]); 345 ox = x; 346 if (x != 0) 347 printf("%.2x %.2x %.2x\n", p[x - 1], p[x], p[x + 1]); 348 uint32_t tag = gettag(p, &x, ep - p + x); 349 if (p + x >= ep) 350 break; 351 uint32_t len = getlength(p, &x, ep - p + x); 352 353 printf("%zu %zu-%zu %c,%c,%s,%u:", level, ox, x, 354 der_class[c], der_type[t], 355 der_tag(buf, sizeof(buf), tag), len); 356 q = p + x; 357 if (p + len > ep) 358 errx(EXIT_FAILURE, "corrupt der"); 359 printtag(tag, q, len); 360 if (t != DER_TYPE_PRIMITIVE) 361 printdata(level + 1, p, x, len + x); 362 x += len; 363 } 364} 365 366int 367main(int argc, char *argv[]) 368{ 369 int fd; 370 struct stat st; 371 size_t l; 372 void *p; 373 374 if ((fd = open(argv[1], O_RDONLY)) == -1) 375 err(EXIT_FAILURE, "open `%s'", argv[1]); 376 if (fstat(fd, &st) == -1) 377 err(EXIT_FAILURE, "stat `%s'", argv[1]); 378 l = (size_t)st.st_size; 379 if ((p = mmap(NULL, l, PROT_READ, MAP_FILE, fd, 0)) == MAP_FAILED) 380 err(EXIT_FAILURE, "mmap `%s'", argv[1]); 381 382 printdata(0, p, 0, l); 383 munmap(p, l); 384 return 0; 385} 386#endif 387