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/buf.h>
16#include <openssl/mem.h>
17#include <openssl/bytestring.h>
18
19#include <assert.h>
20#include <string.h>
21
22#include "internal.h"
23
24
25void CBS_init(CBS *cbs, const uint8_t *data, size_t len) {
26  cbs->data = data;
27  cbs->len = len;
28}
29
30static int cbs_get(CBS *cbs, const uint8_t **p, size_t n) {
31  if (cbs->len < n) {
32    return 0;
33  }
34
35  *p = cbs->data;
36  cbs->data += n;
37  cbs->len -= n;
38  return 1;
39}
40
41int CBS_skip(CBS *cbs, size_t len) {
42  const uint8_t *dummy;
43  return cbs_get(cbs, &dummy, len);
44}
45
46const uint8_t *CBS_data(const CBS *cbs) {
47  return cbs->data;
48}
49
50size_t CBS_len(const CBS *cbs) {
51  return cbs->len;
52}
53
54int CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len) {
55  OPENSSL_free(*out_ptr);
56  *out_ptr = NULL;
57  *out_len = 0;
58
59  if (cbs->len == 0) {
60    return 1;
61  }
62  *out_ptr = BUF_memdup(cbs->data, cbs->len);
63  if (*out_ptr == NULL) {
64    return 0;
65  }
66  *out_len = cbs->len;
67  return 1;
68}
69
70int CBS_strdup(const CBS *cbs, char **out_ptr) {
71  if (*out_ptr != NULL) {
72    OPENSSL_free(*out_ptr);
73  }
74  *out_ptr = BUF_strndup((const char*)cbs->data, cbs->len);
75  return (*out_ptr != NULL);
76}
77
78int CBS_contains_zero_byte(const CBS *cbs) {
79  return memchr(cbs->data, 0, cbs->len) != NULL;
80}
81
82int CBS_mem_equal(const CBS *cbs, const uint8_t *data, size_t len) {
83  if (len != cbs->len) {
84    return 0;
85  }
86  return CRYPTO_memcmp(cbs->data, data, len) == 0;
87}
88
89static int cbs_get_u(CBS *cbs, uint32_t *out, size_t len) {
90  uint32_t result = 0;
91  size_t i;
92  const uint8_t *data;
93
94  if (!cbs_get(cbs, &data, len)) {
95    return 0;
96  }
97  for (i = 0; i < len; i++) {
98    result <<= 8;
99    result |= data[i];
100  }
101  *out = result;
102  return 1;
103}
104
105int CBS_get_u8(CBS *cbs, uint8_t *out) {
106  const uint8_t *v;
107  if (!cbs_get(cbs, &v, 1)) {
108    return 0;
109  }
110  *out = *v;
111  return 1;
112}
113
114int CBS_get_u16(CBS *cbs, uint16_t *out) {
115  uint32_t v;
116  if (!cbs_get_u(cbs, &v, 2)) {
117    return 0;
118  }
119  *out = v;
120  return 1;
121}
122
123int CBS_get_u24(CBS *cbs, uint32_t *out) {
124  return cbs_get_u(cbs, out, 3);
125}
126
127int CBS_get_u32(CBS *cbs, uint32_t *out) {
128  return cbs_get_u(cbs, out, 4);
129}
130
131int CBS_get_bytes(CBS *cbs, CBS *out, size_t len) {
132  const uint8_t *v;
133  if (!cbs_get(cbs, &v, len)) {
134    return 0;
135  }
136  CBS_init(out, v, len);
137  return 1;
138}
139
140int CBS_copy_bytes(CBS *cbs, uint8_t *out, size_t len) {
141  const uint8_t *v;
142  if (!cbs_get(cbs, &v, len)) {
143    return 0;
144  }
145  memcpy(out, v, len);
146  return 1;
147}
148
149static int cbs_get_length_prefixed(CBS *cbs, CBS *out, size_t len_len) {
150  uint32_t len;
151  if (!cbs_get_u(cbs, &len, len_len)) {
152    return 0;
153  }
154  return CBS_get_bytes(cbs, out, len);
155}
156
157int CBS_get_u8_length_prefixed(CBS *cbs, CBS *out) {
158  return cbs_get_length_prefixed(cbs, out, 1);
159}
160
161int CBS_get_u16_length_prefixed(CBS *cbs, CBS *out) {
162  return cbs_get_length_prefixed(cbs, out, 2);
163}
164
165int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out) {
166  return cbs_get_length_prefixed(cbs, out, 3);
167}
168
169static int cbs_get_any_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
170                                    size_t *out_header_len, int ber_ok) {
171  uint8_t tag, length_byte;
172  CBS header = *cbs;
173  CBS throwaway;
174
175  if (out == NULL) {
176    out = &throwaway;
177  }
178
179  if (!CBS_get_u8(&header, &tag) ||
180      !CBS_get_u8(&header, &length_byte)) {
181    return 0;
182  }
183
184  if ((tag & 0x1f) == 0x1f) {
185    /* Long form tags are not supported. */
186    return 0;
187  }
188
189  if (out_tag != NULL) {
190    *out_tag = tag;
191  }
192
193  size_t len;
194  if ((length_byte & 0x80) == 0) {
195    /* Short form length. */
196    len = ((size_t) length_byte) + 2;
197    if (out_header_len != NULL) {
198      *out_header_len = 2;
199    }
200  } else {
201    /* Long form length. */
202    const size_t num_bytes = length_byte & 0x7f;
203    uint32_t len32;
204
205    if (ber_ok && (tag & CBS_ASN1_CONSTRUCTED) != 0 && num_bytes == 0) {
206      /* indefinite length */
207      if (out_header_len != NULL) {
208        *out_header_len = 2;
209      }
210      return CBS_get_bytes(cbs, out, 2);
211    }
212
213    if (num_bytes == 0 || num_bytes > 4) {
214      return 0;
215    }
216    if (!cbs_get_u(&header, &len32, num_bytes)) {
217      return 0;
218    }
219    if (len32 < 128) {
220      /* Length should have used short-form encoding. */
221      return 0;
222    }
223    if ((len32 >> ((num_bytes-1)*8)) == 0) {
224      /* Length should have been at least one byte shorter. */
225      return 0;
226    }
227    len = len32;
228    if (len + 2 + num_bytes < len) {
229      /* Overflow. */
230      return 0;
231    }
232    len += 2 + num_bytes;
233    if (out_header_len != NULL) {
234      *out_header_len = 2 + num_bytes;
235    }
236  }
237
238  return CBS_get_bytes(cbs, out, len);
239}
240
241int CBS_get_any_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
242                                    size_t *out_header_len) {
243  return cbs_get_any_asn1_element(cbs, out, out_tag, out_header_len,
244                                  0 /* DER only */);
245}
246
247int CBS_get_any_ber_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
248                                 size_t *out_header_len) {
249  return cbs_get_any_asn1_element(cbs, out, out_tag, out_header_len,
250                                  1 /* BER allowed */);
251}
252
253static int cbs_get_asn1(CBS *cbs, CBS *out, unsigned tag_value,
254                        int skip_header) {
255  size_t header_len;
256  unsigned tag;
257  CBS throwaway;
258
259  if (out == NULL) {
260    out = &throwaway;
261  }
262
263  if (!CBS_get_any_asn1_element(cbs, out, &tag, &header_len) ||
264      tag != tag_value) {
265    return 0;
266  }
267
268  if (skip_header && !CBS_skip(out, header_len)) {
269    assert(0);
270    return 0;
271  }
272
273  return 1;
274}
275
276int CBS_get_asn1(CBS *cbs, CBS *out, unsigned tag_value) {
277  return cbs_get_asn1(cbs, out, tag_value, 1 /* skip header */);
278}
279
280int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned tag_value) {
281  return cbs_get_asn1(cbs, out, tag_value, 0 /* include header */);
282}
283
284int CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value) {
285  if (CBS_len(cbs) < 1) {
286    return 0;
287  }
288  return CBS_data(cbs)[0] == tag_value;
289}
290
291int CBS_get_asn1_uint64(CBS *cbs, uint64_t *out) {
292  CBS bytes;
293  const uint8_t *data;
294  size_t i, len;
295
296  if (!CBS_get_asn1(cbs, &bytes, CBS_ASN1_INTEGER)) {
297    return 0;
298  }
299
300  *out = 0;
301  data = CBS_data(&bytes);
302  len = CBS_len(&bytes);
303
304  if (len == 0) {
305    /* An INTEGER is encoded with at least one octet. */
306    return 0;
307  }
308
309  if ((data[0] & 0x80) != 0) {
310    /* Negative number. */
311    return 0;
312  }
313
314  if (data[0] == 0 && len > 1 && (data[1] & 0x80) == 0) {
315    /* Extra leading zeros. */
316    return 0;
317  }
318
319  for (i = 0; i < len; i++) {
320    if ((*out >> 56) != 0) {
321      /* Too large to represent as a uint64_t. */
322      return 0;
323    }
324    *out <<= 8;
325    *out |= data[i];
326  }
327
328  return 1;
329}
330
331int CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present, unsigned tag) {
332  int present = 0;
333
334  if (CBS_peek_asn1_tag(cbs, tag)) {
335    if (!CBS_get_asn1(cbs, out, tag)) {
336      return 0;
337    }
338    present = 1;
339  }
340
341  if (out_present != NULL) {
342    *out_present = present;
343  }
344
345  return 1;
346}
347
348int CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out, int *out_present,
349                                       unsigned tag) {
350  CBS child;
351  int present;
352  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
353    return 0;
354  }
355  if (present) {
356    if (!CBS_get_asn1(&child, out, CBS_ASN1_OCTETSTRING) ||
357        CBS_len(&child) != 0) {
358      return 0;
359    }
360  } else {
361    CBS_init(out, NULL, 0);
362  }
363  if (out_present) {
364    *out_present = present;
365  }
366  return 1;
367}
368
369int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out, unsigned tag,
370                                 uint64_t default_value) {
371  CBS child;
372  int present;
373  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
374    return 0;
375  }
376  if (present) {
377    if (!CBS_get_asn1_uint64(&child, out) ||
378        CBS_len(&child) != 0) {
379      return 0;
380    }
381  } else {
382    *out = default_value;
383  }
384  return 1;
385}
386
387int CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned tag,
388                               int default_value) {
389  CBS child, child2;
390  int present;
391  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
392    return 0;
393  }
394  if (present) {
395    uint8_t boolean;
396
397    if (!CBS_get_asn1(&child, &child2, CBS_ASN1_BOOLEAN) ||
398        CBS_len(&child2) != 1 ||
399        CBS_len(&child) != 0) {
400      return 0;
401    }
402
403    boolean = CBS_data(&child2)[0];
404    if (boolean == 0) {
405      *out = 0;
406    } else if (boolean == 0xff) {
407      *out = 1;
408    } else {
409      return 0;
410    }
411  } else {
412    *out = default_value;
413  }
414  return 1;
415}
416