xref: /dragonfly/crypto/libressl/ssl/bs_cbb.c (revision 72c33676) 
1 /*	$OpenBSD: bs_cbb.c,v 1.20 2019/01/23 22:20:40 beck Exp $	*/
2 /*
3  * Copyright (c) 2014, Google Inc.
4  *
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.
8  *
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. */
16 
17 #include <stdlib.h>
18 #include <string.h>
19 
20 #include <openssl/opensslconf.h>
21 
22 #include "bytestring.h"
23 
24 #define CBB_INITIAL_SIZE 64
25 
26 static int
27 cbb_init(CBB *cbb, uint8_t *buf, size_t cap)
28 {
29 	struct cbb_buffer_st *base;
30 
31 	base = malloc(sizeof(struct cbb_buffer_st));
32 	if (base == NULL)
33 		return 0;
34 
35 	base->buf = buf;
36 	base->len = 0;
37 	base->cap = cap;
38 	base->can_resize = 1;
39 
40 	cbb->base = base;
41 	cbb->is_top_level = 1;
42 
43 	return 1;
44 }
45 
46 int
47 CBB_init(CBB *cbb, size_t initial_capacity)
48 {
49 	uint8_t *buf = NULL;
50 
51 	memset(cbb, 0, sizeof(*cbb));
52 
53 	if (initial_capacity == 0)
54 		initial_capacity = CBB_INITIAL_SIZE;
55 
56 	if ((buf = malloc(initial_capacity)) == NULL)
57 		return 0;
58 
59 	if (!cbb_init(cbb, buf, initial_capacity)) {
60 		free(buf);
61 		return 0;
62 	}
63 
64 	return 1;
65 }
66 
67 int
68 CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len)
69 {
70 	memset(cbb, 0, sizeof(*cbb));
71 
72 	if (!cbb_init(cbb, buf, len))
73 		return 0;
74 
75 	cbb->base->can_resize = 0;
76 
77 	return 1;
78 }
79 
80 void
81 CBB_cleanup(CBB *cbb)
82 {
83 	if (cbb->base) {
84 		if (cbb->base->can_resize)
85 			freezero(cbb->base->buf, cbb->base->cap);
86 		free(cbb->base);
87 	}
88 	cbb->base = NULL;
89 	cbb->child = NULL;
90 }
91 
92 static int
93 cbb_buffer_add(struct cbb_buffer_st *base, uint8_t **out, size_t len)
94 {
95 	size_t newlen;
96 
97 	if (base == NULL)
98 		return 0;
99 
100 	newlen = base->len + len;
101 	if (newlen < base->len)
102 		/* Overflow */
103 		return 0;
104 
105 	if (newlen > base->cap) {
106 		size_t newcap = base->cap * 2;
107 		uint8_t *newbuf;
108 
109 		if (!base->can_resize)
110 			return 0;
111 
112 		if (newcap < base->cap || newcap < newlen)
113 			newcap = newlen;
114 
115 		newbuf = recallocarray(base->buf, base->cap, newcap, 1);
116 		if (newbuf == NULL)
117 			return 0;
118 
119 		base->buf = newbuf;
120 		base->cap = newcap;
121 	}
122 
123 	if (out)
124 		*out = base->buf + base->len;
125 
126 	base->len = newlen;
127 	return 1;
128 }
129 
130 static int
131 cbb_add_u(CBB *cbb, uint32_t v, size_t len_len)
132 {
133 	uint8_t *buf;
134 	size_t i;
135 
136 	if (len_len == 0)
137 		return 1;
138 
139 	if (len_len > 4)
140 		return 0;
141 
142 	if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, &buf, len_len))
143 		return 0;
144 
145 	for (i = len_len - 1; i < len_len; i--) {
146 		buf[i] = v;
147 		v >>= 8;
148 	}
149 	return 1;
150 }
151 
152 int
153 CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len)
154 {
155 	if (!cbb->is_top_level)
156 		return 0;
157 
158 	if (!CBB_flush(cbb))
159 		return 0;
160 
161 	if (cbb->base->can_resize && (out_data == NULL || out_len == NULL))
162 		/*
163 		 * |out_data| and |out_len| can only be NULL if the CBB is
164 		 * fixed.
165 		 */
166 		return 0;
167 
168 	if (out_data != NULL)
169 		*out_data = cbb->base->buf;
170 
171 	if (out_len != NULL)
172 		*out_len = cbb->base->len;
173 
174 	cbb->base->buf = NULL;
175 	CBB_cleanup(cbb);
176 	return 1;
177 }
178 
179 /*
180  * CBB_flush recurses and then writes out any pending length prefix. The current
181  * length of the underlying base is taken to be the length of the
182  * length-prefixed data.
183  */
184 int
185 CBB_flush(CBB *cbb)
186 {
187 	size_t child_start, i, len;
188 
189 	if (cbb->base == NULL)
190 		return 0;
191 
192 	if (cbb->child == NULL || cbb->pending_len_len == 0)
193 		return 1;
194 
195 	child_start = cbb->offset + cbb->pending_len_len;
196 
197 	if (!CBB_flush(cbb->child) || child_start < cbb->offset ||
198 	    cbb->base->len < child_start)
199 		return 0;
200 
201 	len = cbb->base->len - child_start;
202 
203 	if (cbb->pending_is_asn1) {
204 		/*
205 		 * For ASN.1, we assumed that we were using short form which
206 		 * only requires a single byte for the length octet.
207 		 *
208 		 * If it turns out that we need long form, we have to move
209 		 * the contents along in order to make space for more length
210 		 * octets.
211 		 */
212 		size_t len_len = 1;  /* total number of length octets */
213 		uint8_t initial_length_byte;
214 
215 		/* We already wrote 1 byte for the length. */
216 		if (cbb->pending_len_len != 1)
217 			return 0;
218 
219 		/* Check for long form */
220 		if (len > 0xfffffffe)
221 			return 0;	/* 0xffffffff is reserved */
222 		else if (len > 0xffffff)
223 			len_len = 5;
224 		else if (len > 0xffff)
225 			len_len = 4;
226 		else if (len > 0xff)
227 			len_len = 3;
228 		else if (len > 0x7f)
229 			len_len = 2;
230 
231 		if (len_len == 1) {
232 			/* For short form, the initial byte is the length. */
233 			initial_length_byte = len;
234 			len = 0;
235 
236 		} else {
237 			/*
238 			 * For long form, the initial byte is the number of
239 			 * subsequent length octets (plus bit 8 set).
240 			 */
241 			initial_length_byte = 0x80 | (len_len - 1);
242 
243 			/*
244 			 * We need to move the contents along in order to make
245 			 * space for the long form length octets.
246 			 */
247 			size_t extra_bytes = len_len - 1;
248 			if (!cbb_buffer_add(cbb->base, NULL, extra_bytes))
249 				return 0;
250 
251 			memmove(cbb->base->buf + child_start + extra_bytes,
252 			    cbb->base->buf + child_start, len);
253 		}
254 		cbb->base->buf[cbb->offset++] = initial_length_byte;
255 		cbb->pending_len_len = len_len - 1;
256 	}
257 
258 	for (i = cbb->pending_len_len - 1; i < cbb->pending_len_len; i--) {
259 		cbb->base->buf[cbb->offset + i] = len;
260 		len >>= 8;
261 	}
262 	if (len != 0)
263 		return 0;
264 
265 	cbb->child->base = NULL;
266 	cbb->child = NULL;
267 	cbb->pending_len_len = 0;
268 	cbb->pending_is_asn1 = 0;
269 	cbb->offset = 0;
270 
271 	return 1;
272 }
273 
274 void
275 CBB_discard_child(CBB *cbb)
276 {
277 	if (cbb->child == NULL)
278 		return;
279 
280 	cbb->base->len = cbb->offset;
281 
282 	cbb->child->base = NULL;
283 	cbb->child = NULL;
284 	cbb->pending_len_len = 0;
285 	cbb->pending_is_asn1 = 0;
286 	cbb->offset = 0;
287 }
288 
289 static int
290 cbb_add_length_prefixed(CBB *cbb, CBB *out_contents, size_t len_len)
291 {
292 	uint8_t *prefix_bytes;
293 
294 	if (!CBB_flush(cbb))
295 		return 0;
296 
297 	cbb->offset = cbb->base->len;
298 	if (!cbb_buffer_add(cbb->base, &prefix_bytes, len_len))
299 		return 0;
300 
301 	memset(prefix_bytes, 0, len_len);
302 	memset(out_contents, 0, sizeof(CBB));
303 	out_contents->base = cbb->base;
304 	cbb->child = out_contents;
305 	cbb->pending_len_len = len_len;
306 	cbb->pending_is_asn1 = 0;
307 
308 	return 1;
309 }
310 
311 int
312 CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents)
313 {
314 	return cbb_add_length_prefixed(cbb, out_contents, 1);
315 }
316 
317 int
318 CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents)
319 {
320 	return cbb_add_length_prefixed(cbb, out_contents, 2);
321 }
322 
323 int
324 CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents)
325 {
326 	return cbb_add_length_prefixed(cbb, out_contents, 3);
327 }
328 
329 int
330 CBB_add_asn1(CBB *cbb, CBB *out_contents, unsigned int tag)
331 {
332 	if (tag > UINT8_MAX)
333 		return 0;
334 
335 	/* Long form identifier octets are not supported. */
336 	if ((tag & 0x1f) == 0x1f)
337 		return 0;
338 
339 	/* Short-form identifier octet only needs a single byte */
340 	if (!CBB_flush(cbb) || !CBB_add_u8(cbb, tag))
341 		return 0;
342 
343 	/*
344 	 * Add 1 byte to cover the short-form length octet case.  If it turns
345 	 * out we need long-form, it will be extended later.
346 	 */
347 	cbb->offset = cbb->base->len;
348 	if (!CBB_add_u8(cbb, 0))
349 		return 0;
350 
351 	memset(out_contents, 0, sizeof(CBB));
352 	out_contents->base = cbb->base;
353 	cbb->child = out_contents;
354 	cbb->pending_len_len = 1;
355 	cbb->pending_is_asn1 = 1;
356 
357 	return 1;
358 }
359 
360 int
361 CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len)
362 {
363 	uint8_t *dest;
364 
365 	if (!CBB_add_space(cbb, &dest, len))
366 		return 0;
367 
368 	memcpy(dest, data, len);
369 	return 1;
370 }
371 
372 int
373 CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len)
374 {
375 	if (!CBB_flush(cbb) || !cbb_buffer_add(cbb->base, out_data, len))
376 		return 0;
377 
378 	return 1;
379 }
380 
381 int
382 CBB_add_u8(CBB *cbb, size_t value)
383 {
384 	if (value > UINT8_MAX)
385 		return 0;
386 
387 	return cbb_add_u(cbb, (uint32_t)value, 1);
388 }
389 
390 int
391 CBB_add_u16(CBB *cbb, size_t value)
392 {
393 	if (value > UINT16_MAX)
394 		return 0;
395 
396 	return cbb_add_u(cbb, (uint32_t)value, 2);
397 }
398 
399 int
400 CBB_add_u24(CBB *cbb, size_t value)
401 {
402 	if (value > 0xffffffUL)
403 		return 0;
404 
405 	return cbb_add_u(cbb, (uint32_t)value, 3);
406 }
407 
408 int
409 CBB_add_u32(CBB *cbb, size_t value)
410 {
411 	if (value > 0xffffffffUL)
412 		return 0;
413 
414 	return cbb_add_u(cbb, (uint32_t)value, 4);
415 }
416 
417 int
418 CBB_add_asn1_uint64(CBB *cbb, uint64_t value)
419 {
420 	CBB child;
421 	size_t i;
422 	int started = 0;
423 
424 	if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER))
425 		return 0;
426 
427 	for (i = 0; i < 8; i++) {
428 		uint8_t byte = (value >> 8 * (7 - i)) & 0xff;
429 
430 		/*
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.
435 		 *
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).
441 		 *
442 		 * Additionally, for an unsigned value, add an all zero
443 		 * prefix if the high bit of the first octet would be one.
444 		 */
445 		if (!started) {
446 			if (byte == 0)
447 				/* Don't encode leading zeros. */
448 				continue;
449 
450 			/*
451 			 * If the high bit is set, add a padding byte to make it
452 			 * unsigned.
453 			 */
454 			if ((byte & 0x80) && !CBB_add_u8(&child, 0))
455 				return 0;
456 
457 			started = 1;
458 		}
459 		if (!CBB_add_u8(&child, byte))
460 			return 0;
461 	}
462 
463 	/* 0 is encoded as a single 0, not the empty string. */
464 	if (!started && !CBB_add_u8(&child, 0))
465 		return 0;
466 
467 	return CBB_flush(cbb);
468 }
469