2 * Copyright (c) 2016 Christos Zoulas
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
27 * DER (Distinguished Encoding Rules) Parser
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/
38 FILE_RCSID("@(#)$File: der.c,v 1.12 2017/02/10 18:14:01 christos Exp $")
42 #include <sys/types.h>
59 #define DER_BAD ((uint32_t)-1)
61 #define DER_CLASS_UNIVERSAL 0
62 #define DER_CLASS_APPLICATION 1
63 #define DER_CLASS_CONTEXT 2
64 #define DER_CLASS_PRIVATE 3
66 static const char der_class[] = "UACP";
69 #define DER_TYPE_PRIMITIVE 0
70 #define DER_TYPE_CONSTRUCTED 1
72 static const char der_type[] = "PC";
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
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"
119 #define DPRINTF(a) printf a
139 gettag(const uint8_t *c, size_t *p, size_t l)
146 tag = c[(*p)++] & 0x1f;
154 while (c[*p] >= 0x80) {
155 tag = tag * 128 + c[(*p)++] - 0x80;
163 * Read the length of a DER tag from the input.
165 * `c` is the input, `p` is an output parameter that specifies how much of the
166 * input we consumed, and `l` is the maximum input length.
168 * Returns the length, or DER_BAD if the end of the input is reached or the
169 * length exceeds the remaining input.
172 getlength(const uint8_t *c, size_t *p, size_t l)
176 int is_onebyte_result;
182 * Digits can either be 0b0 followed by the result, or 0b1
183 * followed by the number of digits of the result. In either case,
184 * we verify that we can read so many bytes from the input.
186 is_onebyte_result = (c[*p] & 0x80) == 0;
187 digits = c[(*p)++] & 0x7f;
188 if (*p + digits >= l)
191 if (is_onebyte_result)
195 * Decode len. We've already verified that we're allowed to read
199 for (i = 0; i < digits; i++)
200 len = (len << 8) | c[(*p)++];
204 return CAST(uint32_t, len);
208 der_tag(char *buf, size_t len, uint32_t tag)
210 if (tag < DER_TAG_LONG)
211 strlcpy(buf, der__tag[tag], len);
213 snprintf(buf, len, "%#x", tag);
219 der_data(char *buf, size_t blen, uint32_t tag, const void *q, uint32_t len)
221 const uint8_t *d = CAST(const uint8_t *, q);
223 case DER_TAG_PRINTABLE_STRING:
224 case DER_TAG_UTF8_STRING:
225 case DER_TAG_IA5_STRING:
226 case DER_TAG_UTCTIME:
227 return snprintf(buf, blen, "%.*s", len, (const char *)q);
232 for (uint32_t i = 0; i < len; i++) {
235 snprintf(buf + z, blen - z, "%.2x", d[i]);
241 der_offs(struct magic_set *ms, struct magic *m, size_t nbytes)
243 const uint8_t *b = RCAST(const uint8_t *, ms->search.s);
244 size_t offs = 0, len = ms->search.s_len ? ms->search.s_len : nbytes;
246 if (gettag(b, &offs, len) == DER_BAD)
248 DPRINTF(("%s1: %d %zu %u\n", __func__, ms->offset, offs, m->offset));
250 uint32_t tlen = getlength(b, &offs, len);
253 DPRINTF(("%s2: %d %zu %u\n", __func__, ms->offset, offs, tlen));
255 offs += ms->offset + m->offset;
256 DPRINTF(("cont_level = %d\n", m->cont_level));
258 for (size_t i = 0; i < m->cont_level; i++)
259 printf("cont_level[%zu] = %u\n", i, ms->c.li[i].off);
261 if (m->cont_level != 0) {
262 if (offs + tlen > nbytes)
264 ms->c.li[m->cont_level - 1].off = CAST(int, offs + tlen);
265 DPRINTF(("cont_level[%u] = %u\n", m->cont_level - 1,
266 ms->c.li[m->cont_level - 1].off));
268 return CAST(int32_t, offs);
272 der_cmp(struct magic_set *ms, struct magic *m)
274 const uint8_t *b = RCAST(const uint8_t *, ms->search.s);
275 const char *s = m->value.s;
276 size_t offs = 0, len = ms->search.s_len;
280 tag = gettag(b, &offs, len);
284 tlen = getlength(b, &offs, len);
288 der_tag(buf, sizeof(buf), tag);
289 if ((ms->flags & MAGIC_DEBUG) != 0)
290 fprintf(stderr, "%s: tag %p got=%s exp=%s\n", __func__, b,
292 size_t slen = strlen(buf);
294 if (strncmp(buf, s, slen) != 0)
307 if (!isdigit((unsigned char)*s))
312 slen = slen * 10 + *s - '0';
313 while (isdigit((unsigned char)*++s));
314 if ((ms->flags & MAGIC_DEBUG) != 0)
315 fprintf(stderr, "%s: len %zu %u\n", __func__,
322 DPRINTF(("%s: before data %zu %u\n", __func__, offs, tlen));
323 der_data(buf, sizeof(buf), tag, b + offs, tlen);
324 if ((ms->flags & MAGIC_DEBUG) != 0)
325 fprintf(stderr, "%s: data %s %s\n", __func__, buf, s);
326 if (strcmp(buf, s) != 0 && strcmp("x", s) != 0)
328 strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s));
335 printtag(uint32_t tag, const void *q, uint32_t len)
337 const uint8_t *d = q;
339 case DER_TAG_PRINTABLE_STRING:
340 case DER_TAG_UTF8_STRING:
341 printf("%.*s\n", len, (const char *)q);
347 for (uint32_t i = 0; i < len; i++)
348 printf("%.2x", d[i]);
353 printdata(size_t level, const void *v, size_t x, size_t l)
355 const uint8_t *p = v, *ep = p + l;
361 uint8_t c = getclass(p[x]);
362 uint8_t t = gettype(p[x]);
365 printf("%.2x %.2x %.2x\n", p[x - 1], p[x], p[x + 1]);
366 uint32_t tag = gettag(p, &x, ep - p + x);
369 uint32_t len = getlength(p, &x, ep - p + x);
371 printf("%zu %zu-%zu %c,%c,%s,%u:", level, ox, x,
372 der_class[c], der_type[t],
373 der_tag(buf, sizeof(buf), tag), len);
376 errx(EXIT_FAILURE, "corrupt der");
377 printtag(tag, q, len);
378 if (t != DER_TYPE_PRIMITIVE)
379 printdata(level + 1, p, x, len + x);
385 main(int argc, char *argv[])
392 if ((fd = open(argv[1], O_RDONLY)) == -1)
393 err(EXIT_FAILURE, "open `%s'", argv[1]);
394 if (fstat(fd, &st) == -1)
395 err(EXIT_FAILURE, "stat `%s'", argv[1]);
396 l = (size_t)st.st_size;
397 if ((p = mmap(NULL, l, PROT_READ, MAP_FILE, fd, 0)) == MAP_FAILED)
398 err(EXIT_FAILURE, "mmap `%s'", argv[1]);
400 printdata(0, p, 0, l);