1 /* $OpenBSD: bs_cbb.c,v 1.23 2020/09/16 05:52:04 jsing Exp $ */
3 * Copyright (c) 2014, Google Inc.
5 * Permission to use, copy, modify, and/or distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
12 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
14 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
15 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
20 #include <openssl/opensslconf.h>
22 #include "bytestring.h"
24 #define CBB_INITIAL_SIZE 64
27 cbb_init(CBB *cbb, uint8_t *buf, size_t cap)
29 struct cbb_buffer_st *base;
31 if ((base = calloc(1, sizeof(struct cbb_buffer_st))) == NULL)
40 cbb->is_top_level = 1;
46 CBB_init(CBB *cbb, size_t initial_capacity)
50 memset(cbb, 0, sizeof(*cbb));
52 if (initial_capacity == 0)
53 initial_capacity = CBB_INITIAL_SIZE;
55 if ((buf = calloc(1, initial_capacity)) == NULL)
58 if (!cbb_init(cbb, buf, initial_capacity)) {
67 CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len)
69 memset(cbb, 0, sizeof(*cbb));
71 if (!cbb_init(cbb, buf, len))
74 cbb->base->can_resize = 0;
83 if (cbb->base->can_resize)
84 freezero(cbb->base->buf, cbb->base->cap);
92 cbb_buffer_add(struct cbb_buffer_st *base, uint8_t **out, size_t len)
99 newlen = base->len + len;
100 if (newlen < base->len)
104 if (newlen > base->cap) {
105 size_t newcap = base->cap * 2;
108 if (!base->can_resize)
111 if (newcap < base->cap || newcap < newlen)
114 newbuf = recallocarray(base->buf, base->cap, newcap, 1);
123 *out = base->buf + base->len;
130 cbb_add_u(CBB *cbb, uint32_t v, size_t len_len)
141 if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &buf, len_len))
144 for (i = len_len - 1; i < len_len; i--) {
152 CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len)
154 if (!cbb->is_top_level)
160 if (cbb->base->can_resize && (out_data == NULL || out_len == NULL))
162 * |out_data| and |out_len| can only be NULL if the CBB is
167 if (out_data != NULL)
168 *out_data = cbb->base->buf;
171 *out_len = cbb->base->len;
173 cbb->base->buf = NULL;
179 * CBB_flush recurses and then writes out any pending length prefix. The current
180 * length of the underlying base is taken to be the length of the
181 * length-prefixed data.
186 size_t child_start, i, len;
188 if (cbb->base == NULL)
191 if (cbb->child == NULL || cbb->pending_len_len == 0)
194 child_start = cbb->offset + cbb->pending_len_len;
196 if (!CBB_flush(cbb->child) || child_start < cbb->offset ||
197 cbb->base->len < child_start)
200 len = cbb->base->len - child_start;
202 if (cbb->pending_is_asn1) {
204 * For ASN.1, we assumed that we were using short form which
205 * only requires a single byte for the length octet.
207 * If it turns out that we need long form, we have to move
208 * the contents along in order to make space for more length
211 size_t len_len = 1; /* total number of length octets */
212 uint8_t initial_length_byte;
214 /* We already wrote 1 byte for the length. */
215 if (cbb->pending_len_len != 1)
218 /* Check for long form */
219 if (len > 0xfffffffe)
220 return 0; /* 0xffffffff is reserved */
221 else if (len > 0xffffff)
223 else if (len > 0xffff)
231 /* For short form, the initial byte is the length. */
232 initial_length_byte = len;
237 * For long form, the initial byte is the number of
238 * subsequent length octets (plus bit 8 set).
240 initial_length_byte = 0x80 | (len_len - 1);
243 * We need to move the contents along in order to make
244 * space for the long form length octets.
246 size_t extra_bytes = len_len - 1;
247 if (!cbb_buffer_add(cbb->base, NULL, extra_bytes))
250 memmove(cbb->base->buf + child_start + extra_bytes,
251 cbb->base->buf + child_start, len);
253 cbb->base->buf[cbb->offset++] = initial_length_byte;
254 cbb->pending_len_len = len_len - 1;
257 for (i = cbb->pending_len_len - 1; i < cbb->pending_len_len; i--) {
258 cbb->base->buf[cbb->offset + i] = len;
264 cbb->child->base = NULL;
266 cbb->pending_len_len = 0;
267 cbb->pending_is_asn1 = 0;
274 CBB_discard_child(CBB *cbb)
276 if (cbb->child == NULL)
279 cbb->base->len = cbb->offset;
281 cbb->child->base = NULL;
283 cbb->pending_len_len = 0;
284 cbb->pending_is_asn1 = 0;
289 cbb_add_length_prefixed(CBB *cbb, CBB *out_contents, size_t len_len)
291 uint8_t *prefix_bytes;
296 cbb->offset = cbb->base->len;
297 if (!cbb_buffer_add(cbb->base, &prefix_bytes, len_len))
300 memset(prefix_bytes, 0, len_len);
301 memset(out_contents, 0, sizeof(CBB));
302 out_contents->base = cbb->base;
303 cbb->child = out_contents;
304 cbb->pending_len_len = len_len;
305 cbb->pending_is_asn1 = 0;
311 CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents)
313 return cbb_add_length_prefixed(cbb, out_contents, 1);
317 CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents)
319 return cbb_add_length_prefixed(cbb, out_contents, 2);
323 CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents)
325 return cbb_add_length_prefixed(cbb, out_contents, 3);
329 CBB_add_asn1(CBB *cbb, CBB *out_contents, unsigned int tag)
334 /* Long form identifier octets are not supported. */
335 if ((tag & 0x1f) == 0x1f)
338 /* Short-form identifier octet only needs a single byte */
339 if (!CBB_flush(cbb) || !CBB_add_u8(cbb, tag))
343 * Add 1 byte to cover the short-form length octet case. If it turns
344 * out we need long-form, it will be extended later.
346 cbb->offset = cbb->base->len;
347 if (!CBB_add_u8(cbb, 0))
350 memset(out_contents, 0, sizeof(CBB));
351 out_contents->base = cbb->base;
352 cbb->child = out_contents;
353 cbb->pending_len_len = 1;
354 cbb->pending_is_asn1 = 1;
360 CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len)
364 if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &dest, len))
367 memcpy(dest, data, len);
372 CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len)
374 if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, out_data, len))
377 memset(*out_data, 0, len);
382 CBB_add_u8(CBB *cbb, size_t value)
384 if (value > UINT8_MAX)
387 return cbb_add_u(cbb, (uint32_t)value, 1);
391 CBB_add_u16(CBB *cbb, size_t value)
393 if (value > UINT16_MAX)
396 return cbb_add_u(cbb, (uint32_t)value, 2);
400 CBB_add_u24(CBB *cbb, size_t value)
402 if (value > 0xffffffUL)
405 return cbb_add_u(cbb, (uint32_t)value, 3);
409 CBB_add_u32(CBB *cbb, size_t value)
411 if (value > 0xffffffffUL)
414 return cbb_add_u(cbb, (uint32_t)value, 4);
418 CBB_add_asn1_uint64(CBB *cbb, uint64_t value)
424 if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER))
427 for (i = 0; i < 8; i++) {
428 uint8_t byte = (value >> 8 * (7 - i)) & 0xff;
431 * ASN.1 restriction: first 9 bits cannot be all zeroes or
432 * all ones. Since this function only encodes unsigned
433 * integers, the only concerns are not encoding leading
434 * zeros and adding a padding byte if necessary.
436 * In practice, this means:
437 * 1) Skip leading octets of all zero bits in the value
438 * 2) After skipping the leading zero octets, if the next 9
439 * bits are all ones, add an all zero prefix octet (and
440 * set the high bit of the prefix octet if negative).
442 * Additionally, for an unsigned value, add an all zero
443 * prefix if the high bit of the first octet would be one.
447 /* Don't encode leading zeros. */
451 * If the high bit is set, add a padding byte to make it
454 if ((byte & 0x80) && !CBB_add_u8(&child, 0))
459 if (!CBB_add_u8(&child, byte))
463 /* 0 is encoded as a single 0, not the empty string. */
464 if (!started && !CBB_add_u8(&child, 0))
467 return CBB_flush(cbb);