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 1.27 2022/09/24 20:30:13 christos Exp $")
39 #endif
40 #else
41 #define SIZE_T_FORMAT "z"
42 #define CAST(a, b) ((a)(b))
43 #endif
44
45 #include <sys/types.h>
46
47 #include <stdio.h>
48 #include <fcntl.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <ctype.h>
52
53 #ifndef TEST_DER
54 #include "magic.h"
55 #include "der.h"
56 #else
57 #include <sys/mman.h>
58 #include <sys/stat.h>
59 #include <err.h>
60 #endif
61
62 #define DER_BAD CAST(uint32_t, -1)
63
64 #define DER_CLASS_UNIVERSAL 0
65 #define DER_CLASS_APPLICATION 1
66 #define DER_CLASS_CONTEXT 2
67 #define DER_CLASS_PRIVATE 3
68 #if defined(DEBUG_DER) || defined(TEST_DER)
69 static const char der_class[] = "UACP";
70 #endif
71
72 #define DER_TYPE_PRIMITIVE 0
73 #define DER_TYPE_CONSTRUCTED 1
74 #if defined(DEBUG_DER) || defined(TEST_DER)
75 static const char der_type[] = "PC";
76 #endif
77
78 #define DER_TAG_EOC 0x00
79 #define DER_TAG_BOOLEAN 0x01
80 #define DER_TAG_INTEGER 0x02
81 #define DER_TAG_BIT STRING 0x03
82 #define DER_TAG_OCTET_STRING 0x04
83 #define DER_TAG_NULL 0x05
84 #define DER_TAG_OBJECT_IDENTIFIER 0x06
85 #define DER_TAG_OBJECT_DESCRIPTOR 0x07
86 #define DER_TAG_EXTERNAL 0x08
87 #define DER_TAG_REAL 0x09
88 #define DER_TAG_ENUMERATED 0x0a
89 #define DER_TAG_EMBEDDED_PDV 0x0b
90 #define DER_TAG_UTF8_STRING 0x0c
91 #define DER_TAG_RELATIVE_OID 0x0d
92 #define DER_TAG_TIME 0x0e
93 #define DER_TAG_RESERVED_2 0x0f
94 #define DER_TAG_SEQUENCE 0x10
95 #define DER_TAG_SET 0x11
96 #define DER_TAG_NUMERIC_STRING 0x12
97 #define DER_TAG_PRINTABLE_STRING 0x13
98 #define DER_TAG_T61_STRING 0x14
99 #define DER_TAG_VIDEOTEX_STRING 0x15
100 #define DER_TAG_IA5_STRING 0x16
101 #define DER_TAG_UTCTIME 0x17
102 #define DER_TAG_GENERALIZED_TIME 0x18
103 #define DER_TAG_GRAPHIC_STRING 0x19
104 #define DER_TAG_VISIBLE_STRING 0x1a
105 #define DER_TAG_GENERAL_STRING 0x1b
106 #define DER_TAG_UNIVERSAL_STRING 0x1c
107 #define DER_TAG_CHARACTER_STRING 0x1d
108 #define DER_TAG_BMP_STRING 0x1e
109 #define DER_TAG_DATE 0x1f
110 #define DER_TAG_TIME_OF_DAY 0x20
111 #define DER_TAG_DATE_TIME 0x21
112 #define DER_TAG_DURATION 0x22
113 #define DER_TAG_OID_IRI 0x23
114 #define DER_TAG_RELATIVE_OID_IRI 0x24
115 #define DER_TAG_LAST 0x25
116
117 static const char *der__tag[] = {
118 "eoc", "bool", "int", "bit_str", "octet_str",
119 "null", "obj_id", "obj_desc", "ext", "real",
120 "enum", "embed", "utf8_str", "rel_oid", "time",
121 "res2", "seq", "set", "num_str", "prt_str",
122 "t61_str", "vid_str", "ia5_str", "utc_time", "gen_time",
123 "gr_str", "vis_str", "gen_str", "univ_str", "char_str",
124 "bmp_str", "date", "tod", "datetime", "duration",
125 "oid-iri", "rel-oid-iri",
126 };
127
128 #ifdef DEBUG_DER
129 #define DPRINTF(a) printf a
130 #else
131 #define DPRINTF(a)
132 #endif
133
134 #ifdef TEST_DER
135 static uint8_t
getclass(uint8_t c)136 getclass(uint8_t c)
137 {
138 return c >> 6;
139 }
140
141 static uint8_t
gettype(uint8_t c)142 gettype(uint8_t c)
143 {
144 return (c >> 5) & 1;
145 }
146 #endif
147
148 static uint32_t
gettag(const uint8_t * c,size_t * p,size_t l)149 gettag(const uint8_t *c, size_t *p, size_t l)
150 {
151 uint32_t tag;
152
153 if (*p >= l)
154 return DER_BAD;
155
156 tag = c[(*p)++] & 0x1f;
157
158 if (tag != 0x1f)
159 return tag;
160
161 if (*p >= l)
162 return DER_BAD;
163
164 while (c[*p] >= 0x80) {
165 tag = tag * 128 + c[(*p)++] - 0x80;
166 if (*p >= l)
167 return DER_BAD;
168 }
169 return tag;
170 }
171
172 /*
173 * Read the length of a DER tag from the input.
174 *
175 * `c` is the input, `p` is an output parameter that specifies how much of the
176 * input we consumed, and `l` is the maximum input length.
177 *
178 * Returns the length, or DER_BAD if the end of the input is reached or the
179 * length exceeds the remaining input.
180 */
181 static uint32_t
getlength(const uint8_t * c,size_t * p,size_t l)182 getlength(const uint8_t *c, size_t *p, size_t l)
183 {
184 uint8_t digits, i;
185 size_t len;
186 int is_onebyte_result;
187
188 if (*p >= l) {
189 DPRINTF(("%s:[1] %zu >= %zu\n", __func__, *p, l));
190 return DER_BAD;
191 }
192
193 /*
194 * Digits can either be 0b0 followed by the result, or 0b1
195 * followed by the number of digits of the result. In either case,
196 * we verify that we can read so many bytes from the input.
197 */
198 is_onebyte_result = (c[*p] & 0x80) == 0;
199 digits = c[(*p)++] & 0x7f;
200 if (*p + digits >= l) {
201 DPRINTF(("%s:[2] %zu + %u >= %zu\n", __func__, *p, digits, l));
202 return DER_BAD;
203 }
204
205 if (is_onebyte_result)
206 return digits;
207
208 /*
209 * Decode len. We've already verified that we're allowed to read
210 * `digits` bytes.
211 */
212 len = 0;
213 for (i = 0; i < digits; i++)
214 len = (len << 8) | c[(*p)++];
215
216 if (len > UINT32_MAX - *p || *p + len > l) {
217 DPRINTF(("%s:[3] bad len %zu + %zu >= %zu\n",
218 __func__, *p, len, l));
219 return DER_BAD;
220 }
221 return CAST(uint32_t, len);
222 }
223
224 static const char *
der_tag(char * buf,size_t len,uint32_t tag)225 der_tag(char *buf, size_t len, uint32_t tag)
226 {
227 if (tag < DER_TAG_LAST)
228 strlcpy(buf, der__tag[tag], len);
229 else
230 snprintf(buf, len, "%#x", tag);
231 return buf;
232 }
233
234 #ifndef TEST_DER
235 static int
der_data(char * buf,size_t blen,uint32_t tag,const void * q,uint32_t len)236 der_data(char *buf, size_t blen, uint32_t tag, const void *q, uint32_t len)
237 {
238 uint32_t i;
239 const uint8_t *d = CAST(const uint8_t *, q);
240 switch (tag) {
241 case DER_TAG_PRINTABLE_STRING:
242 case DER_TAG_UTF8_STRING:
243 case DER_TAG_IA5_STRING:
244 return snprintf(buf, blen, "%.*s", len, RCAST(const char *, q));
245 case DER_TAG_UTCTIME:
246 if (len < 12)
247 break;
248 return snprintf(buf, blen,
249 "20%c%c-%c%c-%c%c %c%c:%c%c:%c%c GMT", d[0], d[1], d[2],
250 d[3], d[4], d[5], d[6], d[7], d[8], d[9], d[10], d[11]);
251 default:
252 break;
253 }
254
255 for (i = 0; i < len; i++) {
256 uint32_t z = i << 1;
257 if (z < blen - 2)
258 snprintf(buf + z, blen - z, "%.2x", d[i]);
259 }
260 return len * 2;
261 }
262
263 int32_t
der_offs(struct magic_set * ms,struct magic * m,size_t nbytes)264 der_offs(struct magic_set *ms, struct magic *m, size_t nbytes)
265 {
266 const uint8_t *b = RCAST(const uint8_t *, ms->search.s);
267 size_t offs = 0, len = ms->search.s_len ? ms->search.s_len : nbytes;
268
269 if (gettag(b, &offs, len) == DER_BAD) {
270 DPRINTF(("%s: bad tag 1\n", __func__));
271 return -1;
272 }
273 DPRINTF(("%s1: %u %" SIZE_T_FORMAT "u %d\n", __func__, ms->offset,
274 offs, m->offset));
275
276 uint32_t tlen = getlength(b, &offs, len);
277 if (tlen == DER_BAD) {
278 DPRINTF(("%s: bad tag 2\n", __func__));
279 return -1;
280 }
281 DPRINTF(("%s2: %u %" SIZE_T_FORMAT "u %u\n", __func__, ms->offset,
282 offs, tlen));
283
284 offs += ms->offset + m->offset;
285 DPRINTF(("cont_level = %d\n", m->cont_level));
286 #ifdef DEBUG_DER
287 size_t i;
288 for (i = 0; i < m->cont_level; i++)
289 printf("cont_level[%" SIZE_T_FORMAT "u] = %d\n", i,
290 ms->c.li[i].off);
291 #endif
292 if (m->cont_level != 0) {
293 if (offs + tlen > nbytes)
294 return -1;
295 ms->c.li[m->cont_level - 1].off = CAST(int, offs + tlen);
296 DPRINTF(("cont_level[%u] = %d\n", m->cont_level - 1,
297 ms->c.li[m->cont_level - 1].off));
298 }
299 return CAST(int32_t, offs);
300 }
301
302 int
der_cmp(struct magic_set * ms,struct magic * m)303 der_cmp(struct magic_set *ms, struct magic *m)
304 {
305 const uint8_t *b = RCAST(const uint8_t *, ms->search.s);
306 const char *s = m->value.s;
307 size_t offs = 0, len = ms->search.s_len;
308 uint32_t tag, tlen;
309 char buf[128];
310
311 DPRINTF(("%s: compare %zu bytes\n", __func__, len));
312
313 tag = gettag(b, &offs, len);
314 if (tag == DER_BAD) {
315 DPRINTF(("%s: bad tag 1\n", __func__));
316 return -1;
317 }
318
319 DPRINTF(("%s1: %d %" SIZE_T_FORMAT "u %d\n", __func__, ms->offset,
320 offs, m->offset));
321
322 tlen = getlength(b, &offs, len);
323 if (tlen == DER_BAD) {
324 DPRINTF(("%s: bad tag 2\n", __func__));
325 return -1;
326 }
327
328 der_tag(buf, sizeof(buf), tag);
329 if ((ms->flags & MAGIC_DEBUG) != 0)
330 fprintf(stderr, "%s: tag %p got=%s exp=%s\n", __func__, b,
331 buf, s);
332 size_t slen = strlen(buf);
333
334 if (strncmp(buf, s, slen) != 0) {
335 DPRINTF(("%s: no string match %s != %s\n", __func__, buf, s));
336 return 0;
337 }
338
339 s += slen;
340
341 again:
342 switch (*s) {
343 case '\0':
344 DPRINTF(("%s: EOF match\n", __func__));
345 return 1;
346 case '=':
347 s++;
348 goto val;
349 default:
350 if (!isdigit(CAST(unsigned char, *s))) {
351 DPRINTF(("%s: no digit %c\n", __func__, *s));
352 return 0;
353 }
354
355 slen = 0;
356 do
357 slen = slen * 10 + *s - '0';
358 while (isdigit(CAST(unsigned char, *++s)));
359 if ((ms->flags & MAGIC_DEBUG) != 0)
360 fprintf(stderr, "%s: len %" SIZE_T_FORMAT "u %u\n",
361 __func__, slen, tlen);
362 if (tlen != slen) {
363 DPRINTF(("%s: len %u != %zu\n", __func__, tlen, slen));
364 return 0;
365 }
366 goto again;
367 }
368 val:
369 DPRINTF(("%s: before data %" SIZE_T_FORMAT "u %u\n", __func__, offs,
370 tlen));
371 der_data(buf, sizeof(buf), tag, b + offs, tlen);
372 if ((ms->flags & MAGIC_DEBUG) != 0)
373 fprintf(stderr, "%s: data %s %s\n", __func__, buf, s);
374 if (strcmp(buf, s) != 0 && strcmp("x", s) != 0) {
375 DPRINTF(("%s: no string match %s != %s\n", __func__, buf, s));
376 return 0;
377 }
378 strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s));
379 DPRINTF(("%s: complete match\n", __func__));
380 return 1;
381 }
382 #endif
383
384 #ifdef TEST_DER
385 static void
printtag(uint32_t tag,const void * q,uint32_t len)386 printtag(uint32_t tag, const void *q, uint32_t len)
387 {
388 const uint8_t *d = q;
389 switch (tag) {
390 case DER_TAG_PRINTABLE_STRING:
391 case DER_TAG_UTF8_STRING:
392 case DER_TAG_IA5_STRING:
393 case DER_TAG_UTCTIME:
394 printf("%.*s\n", len, (const char *)q);
395 return;
396 default:
397 break;
398 }
399
400 for (uint32_t i = 0; i < len; i++)
401 printf("%.2x", d[i]);
402 printf("\n");
403 }
404
405 static void
printdata(size_t level,const void * v,size_t x,size_t l)406 printdata(size_t level, const void *v, size_t x, size_t l)
407 {
408 const uint8_t *p = v, *ep = p + l;
409 size_t ox;
410 char buf[128];
411
412 while (p + x < ep) {
413 const uint8_t *q;
414 uint8_t c = getclass(p[x]);
415 uint8_t t = gettype(p[x]);
416 ox = x;
417 // if (x != 0)
418 // printf("%.2x %.2x %.2x\n", p[x - 1], p[x], p[x + 1]);
419 uint32_t tag = gettag(p, &x, ep - p + x);
420 if (p + x >= ep)
421 break;
422 uint32_t len = getlength(p, &x, ep - p + x);
423
424 printf("%" SIZE_T_FORMAT "u %" SIZE_T_FORMAT "u-%"
425 SIZE_T_FORMAT "u %c,%c,%s,%u:", level, ox, x,
426 der_class[c], der_type[t],
427 der_tag(buf, sizeof(buf), tag), len);
428 q = p + x;
429 if (p + len > ep)
430 errx(EXIT_FAILURE, "corrupt der");
431 printtag(tag, q, len);
432 if (t != DER_TYPE_PRIMITIVE)
433 printdata(level + 1, p, x, len + x);
434 x += len;
435 }
436 }
437
438 int
main(int argc,char * argv[])439 main(int argc, char *argv[])
440 {
441 int fd;
442 struct stat st;
443 size_t l;
444 void *p;
445
446 if ((fd = open(argv[1], O_RDONLY)) == -1)
447 err(EXIT_FAILURE, "open `%s'", argv[1]);
448 if (fstat(fd, &st) == -1)
449 err(EXIT_FAILURE, "stat `%s'", argv[1]);
450 l = (size_t)st.st_size;
451 if ((p = mmap(NULL, l, PROT_READ, MAP_FILE, fd, 0)) == MAP_FAILED)
452 err(EXIT_FAILURE, "mmap `%s'", argv[1]);
453
454 printdata(0, p, 0, l);
455 munmap(p, l);
456 return 0;
457 }
458 #endif
459