sshbuf.c revision 295367 
1/*	$OpenBSD: sshbuf.c,v 1.4 2015/10/05 17:11:21 djm Exp $	*/
2/*
3 * Copyright (c) 2011 Damien Miller
4 *
5 * Permission to use, copy, modify, and 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
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#define SSHBUF_INTERNAL
19#include "includes.h"
20
21#include <sys/param.h>	/* roundup */
22#include <sys/types.h>
23#include <signal.h>
24#include <stdlib.h>
25#include <stdio.h>
26#include <string.h>
27
28#include "ssherr.h"
29#include "sshbuf.h"
30
31static inline int
32sshbuf_check_sanity(const struct sshbuf *buf)
33{
34	SSHBUF_TELL("sanity");
35	if (__predict_false(buf == NULL ||
36	    (!buf->readonly && buf->d != buf->cd) ||
37	    buf->refcount < 1 || buf->refcount > SSHBUF_REFS_MAX ||
38	    buf->cd == NULL ||
39	    (buf->dont_free && (buf->readonly || buf->parent != NULL)) ||
40	    buf->max_size > SSHBUF_SIZE_MAX ||
41	    buf->alloc > buf->max_size ||
42	    buf->size > buf->alloc ||
43	    buf->off > buf->size)) {
44		/* Do not try to recover from corrupted buffer internals */
45		SSHBUF_DBG(("SSH_ERR_INTERNAL_ERROR"));
46		signal(SIGSEGV, SIG_DFL);
47		raise(SIGSEGV);
48		return SSH_ERR_INTERNAL_ERROR;
49	}
50	return 0;
51}
52
53static void
54sshbuf_maybe_pack(struct sshbuf *buf, int force)
55{
56	SSHBUF_DBG(("force %d", force));
57	SSHBUF_TELL("pre-pack");
58	if (buf->off == 0 || buf->readonly || buf->refcount > 1)
59		return;
60	if (force ||
61	    (buf->off >= SSHBUF_PACK_MIN && buf->off >= buf->size / 2)) {
62		memmove(buf->d, buf->d + buf->off, buf->size - buf->off);
63		buf->size -= buf->off;
64		buf->off = 0;
65		SSHBUF_TELL("packed");
66	}
67}
68
69struct sshbuf *
70sshbuf_new(void)
71{
72	struct sshbuf *ret;
73
74	if ((ret = calloc(sizeof(*ret), 1)) == NULL)
75		return NULL;
76	ret->alloc = SSHBUF_SIZE_INIT;
77	ret->max_size = SSHBUF_SIZE_MAX;
78	ret->readonly = 0;
79	ret->refcount = 1;
80	ret->parent = NULL;
81	if ((ret->cd = ret->d = calloc(1, ret->alloc)) == NULL) {
82		free(ret);
83		return NULL;
84	}
85	return ret;
86}
87
88struct sshbuf *
89sshbuf_from(const void *blob, size_t len)
90{
91	struct sshbuf *ret;
92
93	if (blob == NULL || len > SSHBUF_SIZE_MAX ||
94	    (ret = calloc(sizeof(*ret), 1)) == NULL)
95		return NULL;
96	ret->alloc = ret->size = ret->max_size = len;
97	ret->readonly = 1;
98	ret->refcount = 1;
99	ret->parent = NULL;
100	ret->cd = blob;
101	ret->d = NULL;
102	return ret;
103}
104
105int
106sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent)
107{
108	int r;
109
110	if ((r = sshbuf_check_sanity(child)) != 0 ||
111	    (r = sshbuf_check_sanity(parent)) != 0)
112		return r;
113	child->parent = parent;
114	child->parent->refcount++;
115	return 0;
116}
117
118struct sshbuf *
119sshbuf_fromb(struct sshbuf *buf)
120{
121	struct sshbuf *ret;
122
123	if (sshbuf_check_sanity(buf) != 0)
124		return NULL;
125	if ((ret = sshbuf_from(sshbuf_ptr(buf), sshbuf_len(buf))) == NULL)
126		return NULL;
127	if (sshbuf_set_parent(ret, buf) != 0) {
128		sshbuf_free(ret);
129		return NULL;
130	}
131	return ret;
132}
133
134void
135sshbuf_init(struct sshbuf *ret)
136{
137	explicit_bzero(ret, sizeof(*ret));
138	ret->alloc = SSHBUF_SIZE_INIT;
139	ret->max_size = SSHBUF_SIZE_MAX;
140	ret->readonly = 0;
141	ret->dont_free = 1;
142	ret->refcount = 1;
143	if ((ret->cd = ret->d = calloc(1, ret->alloc)) == NULL)
144		ret->alloc = 0;
145}
146
147void
148sshbuf_free(struct sshbuf *buf)
149{
150	int dont_free = 0;
151
152	if (buf == NULL)
153		return;
154	/*
155	 * The following will leak on insane buffers, but this is the safest
156	 * course of action - an invalid pointer or already-freed pointer may
157	 * have been passed to us and continuing to scribble over memory would
158	 * be bad.
159	 */
160	if (sshbuf_check_sanity(buf) != 0)
161		return;
162	/*
163	 * If we are a child, the free our parent to decrement its reference
164	 * count and possibly free it.
165	 */
166	if (buf->parent != NULL) {
167		sshbuf_free(buf->parent);
168		buf->parent = NULL;
169	}
170	/*
171	 * If we are a parent with still-extant children, then don't free just
172	 * yet. The last child's call to sshbuf_free should decrement our
173	 * refcount to 0 and trigger the actual free.
174	 */
175	buf->refcount--;
176	if (buf->refcount > 0)
177		return;
178	dont_free = buf->dont_free;
179	if (!buf->readonly) {
180		explicit_bzero(buf->d, buf->alloc);
181		free(buf->d);
182	}
183	explicit_bzero(buf, sizeof(*buf));
184	if (!dont_free)
185		free(buf);
186}
187
188void
189sshbuf_reset(struct sshbuf *buf)
190{
191	u_char *d;
192
193	if (buf->readonly || buf->refcount > 1) {
194		/* Nonsensical. Just make buffer appear empty */
195		buf->off = buf->size;
196		return;
197	}
198	if (sshbuf_check_sanity(buf) == 0)
199		explicit_bzero(buf->d, buf->alloc);
200	buf->off = buf->size = 0;
201	if (buf->alloc != SSHBUF_SIZE_INIT) {
202		if ((d = realloc(buf->d, SSHBUF_SIZE_INIT)) != NULL) {
203			buf->cd = buf->d = d;
204			buf->alloc = SSHBUF_SIZE_INIT;
205		}
206	}
207}
208
209size_t
210sshbuf_max_size(const struct sshbuf *buf)
211{
212	return buf->max_size;
213}
214
215size_t
216sshbuf_alloc(const struct sshbuf *buf)
217{
218	return buf->alloc;
219}
220
221const struct sshbuf *
222sshbuf_parent(const struct sshbuf *buf)
223{
224	return buf->parent;
225}
226
227u_int
228sshbuf_refcount(const struct sshbuf *buf)
229{
230	return buf->refcount;
231}
232
233int
234sshbuf_set_max_size(struct sshbuf *buf, size_t max_size)
235{
236	size_t rlen;
237	u_char *dp;
238	int r;
239
240	SSHBUF_DBG(("set max buf = %p len = %zu", buf, max_size));
241	if ((r = sshbuf_check_sanity(buf)) != 0)
242		return r;
243	if (max_size == buf->max_size)
244		return 0;
245	if (buf->readonly || buf->refcount > 1)
246		return SSH_ERR_BUFFER_READ_ONLY;
247	if (max_size > SSHBUF_SIZE_MAX)
248		return SSH_ERR_NO_BUFFER_SPACE;
249	/* pack and realloc if necessary */
250	sshbuf_maybe_pack(buf, max_size < buf->size);
251	if (max_size < buf->alloc && max_size > buf->size) {
252		if (buf->size < SSHBUF_SIZE_INIT)
253			rlen = SSHBUF_SIZE_INIT;
254		else
255			rlen = roundup(buf->size, SSHBUF_SIZE_INC);
256		if (rlen > max_size)
257			rlen = max_size;
258		explicit_bzero(buf->d + buf->size, buf->alloc - buf->size);
259		SSHBUF_DBG(("new alloc = %zu", rlen));
260		if ((dp = realloc(buf->d, rlen)) == NULL)
261			return SSH_ERR_ALLOC_FAIL;
262		buf->cd = buf->d = dp;
263		buf->alloc = rlen;
264	}
265	SSHBUF_TELL("new-max");
266	if (max_size < buf->alloc)
267		return SSH_ERR_NO_BUFFER_SPACE;
268	buf->max_size = max_size;
269	return 0;
270}
271
272size_t
273sshbuf_len(const struct sshbuf *buf)
274{
275	if (sshbuf_check_sanity(buf) != 0)
276		return 0;
277	return buf->size - buf->off;
278}
279
280size_t
281sshbuf_avail(const struct sshbuf *buf)
282{
283	if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
284		return 0;
285	return buf->max_size - (buf->size - buf->off);
286}
287
288const u_char *
289sshbuf_ptr(const struct sshbuf *buf)
290{
291	if (sshbuf_check_sanity(buf) != 0)
292		return NULL;
293	return buf->cd + buf->off;
294}
295
296u_char *
297sshbuf_mutable_ptr(const struct sshbuf *buf)
298{
299	if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
300		return NULL;
301	return buf->d + buf->off;
302}
303
304int
305sshbuf_check_reserve(const struct sshbuf *buf, size_t len)
306{
307	int r;
308
309	if ((r = sshbuf_check_sanity(buf)) != 0)
310		return r;
311	if (buf->readonly || buf->refcount > 1)
312		return SSH_ERR_BUFFER_READ_ONLY;
313	SSHBUF_TELL("check");
314	/* Check that len is reasonable and that max_size + available < len */
315	if (len > buf->max_size || buf->max_size - len < buf->size - buf->off)
316		return SSH_ERR_NO_BUFFER_SPACE;
317	return 0;
318}
319
320int
321sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp)
322{
323	size_t rlen, need;
324	u_char *dp;
325	int r;
326
327	if (dpp != NULL)
328		*dpp = NULL;
329
330	SSHBUF_DBG(("reserve buf = %p len = %zu", buf, len));
331	if ((r = sshbuf_check_reserve(buf, len)) != 0)
332		return r;
333	/*
334	 * If the requested allocation appended would push us past max_size
335	 * then pack the buffer, zeroing buf->off.
336	 */
337	sshbuf_maybe_pack(buf, buf->size + len > buf->max_size);
338	SSHBUF_TELL("reserve");
339	if (len + buf->size > buf->alloc) {
340		/*
341		 * Prefer to alloc in SSHBUF_SIZE_INC units, but
342		 * allocate less if doing so would overflow max_size.
343		 */
344		need = len + buf->size - buf->alloc;
345		rlen = roundup(buf->alloc + need, SSHBUF_SIZE_INC);
346		SSHBUF_DBG(("need %zu initial rlen %zu", need, rlen));
347		if (rlen > buf->max_size)
348			rlen = buf->alloc + need;
349		SSHBUF_DBG(("adjusted rlen %zu", rlen));
350		if ((dp = realloc(buf->d, rlen)) == NULL) {
351			SSHBUF_DBG(("realloc fail"));
352			if (dpp != NULL)
353				*dpp = NULL;
354			return SSH_ERR_ALLOC_FAIL;
355		}
356		buf->alloc = rlen;
357		buf->cd = buf->d = dp;
358		if ((r = sshbuf_check_reserve(buf, len)) < 0) {
359			/* shouldn't fail */
360			if (dpp != NULL)
361				*dpp = NULL;
362			return r;
363		}
364	}
365	dp = buf->d + buf->size;
366	buf->size += len;
367	SSHBUF_TELL("done");
368	if (dpp != NULL)
369		*dpp = dp;
370	return 0;
371}
372
373int
374sshbuf_consume(struct sshbuf *buf, size_t len)
375{
376	int r;
377
378	SSHBUF_DBG(("len = %zu", len));
379	if ((r = sshbuf_check_sanity(buf)) != 0)
380		return r;
381	if (len == 0)
382		return 0;
383	if (len > sshbuf_len(buf))
384		return SSH_ERR_MESSAGE_INCOMPLETE;
385	buf->off += len;
386	SSHBUF_TELL("done");
387	return 0;
388}
389
390int
391sshbuf_consume_end(struct sshbuf *buf, size_t len)
392{
393	int r;
394
395	SSHBUF_DBG(("len = %zu", len));
396	if ((r = sshbuf_check_sanity(buf)) != 0)
397		return r;
398	if (len == 0)
399		return 0;
400	if (len > sshbuf_len(buf))
401		return SSH_ERR_MESSAGE_INCOMPLETE;
402	buf->size -= len;
403	SSHBUF_TELL("done");
404	return 0;
405}
406
407