1 /* $OpenBSD: sshbuf.c,v 1.12 2018/07/09 21:56:06 markus 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/types.h>
22 #include <signal.h>
23 #include <stdlib.h>
24 #include <stdio.h>
25 #include <string.h>
26
27 #include "ssherr.h"
28 #include "sshbuf.h"
29 #include "misc.h"
30
31 static inline int
sshbuf_check_sanity(const struct sshbuf * buf)32 sshbuf_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->max_size > SSHBUF_SIZE_MAX ||
40 buf->alloc > buf->max_size ||
41 buf->size > buf->alloc ||
42 buf->off > buf->size)) {
43 /* Do not try to recover from corrupted buffer internals */
44 SSHBUF_DBG(("SSH_ERR_INTERNAL_ERROR"));
45 signal(SIGSEGV, SIG_DFL);
46 raise(SIGSEGV);
47 return SSH_ERR_INTERNAL_ERROR;
48 }
49 return 0;
50 }
51
52 static void
sshbuf_maybe_pack(struct sshbuf * buf,int force)53 sshbuf_maybe_pack(struct sshbuf *buf, int force)
54 {
55 SSHBUF_DBG(("force %d", force));
56 SSHBUF_TELL("pre-pack");
57 if (buf->off == 0 || buf->readonly || buf->refcount > 1)
58 return;
59 if (force ||
60 (buf->off >= SSHBUF_PACK_MIN && buf->off >= buf->size / 2)) {
61 memmove(buf->d, buf->d + buf->off, buf->size - buf->off);
62 buf->size -= buf->off;
63 buf->off = 0;
64 SSHBUF_TELL("packed");
65 }
66 }
67
68 struct sshbuf *
sshbuf_new(void)69 sshbuf_new(void)
70 {
71 struct sshbuf *ret;
72
73 if ((ret = calloc(sizeof(*ret), 1)) == NULL)
74 return NULL;
75 ret->alloc = SSHBUF_SIZE_INIT;
76 ret->max_size = SSHBUF_SIZE_MAX;
77 ret->readonly = 0;
78 ret->refcount = 1;
79 ret->parent = NULL;
80 if ((ret->cd = ret->d = calloc(1, ret->alloc)) == NULL) {
81 free(ret);
82 return NULL;
83 }
84 return ret;
85 }
86
87 struct sshbuf *
sshbuf_from(const void * blob,size_t len)88 sshbuf_from(const void *blob, size_t len)
89 {
90 struct sshbuf *ret;
91
92 if (blob == NULL || len > SSHBUF_SIZE_MAX ||
93 (ret = calloc(sizeof(*ret), 1)) == NULL)
94 return NULL;
95 ret->alloc = ret->size = ret->max_size = len;
96 ret->readonly = 1;
97 ret->refcount = 1;
98 ret->parent = NULL;
99 ret->cd = blob;
100 ret->d = NULL;
101 return ret;
102 }
103
104 int
sshbuf_set_parent(struct sshbuf * child,struct sshbuf * parent)105 sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent)
106 {
107 int r;
108
109 if ((r = sshbuf_check_sanity(child)) != 0 ||
110 (r = sshbuf_check_sanity(parent)) != 0)
111 return r;
112 child->parent = parent;
113 child->parent->refcount++;
114 return 0;
115 }
116
117 struct sshbuf *
sshbuf_fromb(struct sshbuf * buf)118 sshbuf_fromb(struct sshbuf *buf)
119 {
120 struct sshbuf *ret;
121
122 if (sshbuf_check_sanity(buf) != 0)
123 return NULL;
124 if ((ret = sshbuf_from(sshbuf_ptr(buf), sshbuf_len(buf))) == NULL)
125 return NULL;
126 if (sshbuf_set_parent(ret, buf) != 0) {
127 sshbuf_free(ret);
128 return NULL;
129 }
130 return ret;
131 }
132
133 void
sshbuf_free(struct sshbuf * buf)134 sshbuf_free(struct sshbuf *buf)
135 {
136 if (buf == NULL)
137 return;
138 /*
139 * The following will leak on insane buffers, but this is the safest
140 * course of action - an invalid pointer or already-freed pointer may
141 * have been passed to us and continuing to scribble over memory would
142 * be bad.
143 */
144 if (sshbuf_check_sanity(buf) != 0)
145 return;
146 /*
147 * If we are a child, the free our parent to decrement its reference
148 * count and possibly free it.
149 */
150 sshbuf_free(buf->parent);
151 buf->parent = NULL;
152 /*
153 * If we are a parent with still-extant children, then don't free just
154 * yet. The last child's call to sshbuf_free should decrement our
155 * refcount to 0 and trigger the actual free.
156 */
157 buf->refcount--;
158 if (buf->refcount > 0)
159 return;
160 if (!buf->readonly) {
161 explicit_bzero(buf->d, buf->alloc);
162 free(buf->d);
163 }
164 explicit_bzero(buf, sizeof(*buf));
165 free(buf);
166 }
167
168 void
sshbuf_reset(struct sshbuf * buf)169 sshbuf_reset(struct sshbuf *buf)
170 {
171 u_char *d;
172
173 if (buf->readonly || buf->refcount > 1) {
174 /* Nonsensical. Just make buffer appear empty */
175 buf->off = buf->size;
176 return;
177 }
178 (void) sshbuf_check_sanity(buf);
179 buf->off = buf->size = 0;
180 if (buf->alloc != SSHBUF_SIZE_INIT) {
181 if ((d = recallocarray(buf->d, buf->alloc, SSHBUF_SIZE_INIT,
182 1)) != NULL) {
183 buf->cd = buf->d = d;
184 buf->alloc = SSHBUF_SIZE_INIT;
185 }
186 }
187 explicit_bzero(buf->d, SSHBUF_SIZE_INIT);
188 }
189
190 size_t
sshbuf_max_size(const struct sshbuf * buf)191 sshbuf_max_size(const struct sshbuf *buf)
192 {
193 return buf->max_size;
194 }
195
196 size_t
sshbuf_alloc(const struct sshbuf * buf)197 sshbuf_alloc(const struct sshbuf *buf)
198 {
199 return buf->alloc;
200 }
201
202 const struct sshbuf *
sshbuf_parent(const struct sshbuf * buf)203 sshbuf_parent(const struct sshbuf *buf)
204 {
205 return buf->parent;
206 }
207
208 u_int
sshbuf_refcount(const struct sshbuf * buf)209 sshbuf_refcount(const struct sshbuf *buf)
210 {
211 return buf->refcount;
212 }
213
214 int
sshbuf_set_max_size(struct sshbuf * buf,size_t max_size)215 sshbuf_set_max_size(struct sshbuf *buf, size_t max_size)
216 {
217 size_t rlen;
218 u_char *dp;
219 int r;
220
221 SSHBUF_DBG(("set max buf = %p len = %zu", buf, max_size));
222 if ((r = sshbuf_check_sanity(buf)) != 0)
223 return r;
224 if (max_size == buf->max_size)
225 return 0;
226 if (buf->readonly || buf->refcount > 1)
227 return SSH_ERR_BUFFER_READ_ONLY;
228 if (max_size > SSHBUF_SIZE_MAX)
229 return SSH_ERR_NO_BUFFER_SPACE;
230 /* pack and realloc if necessary */
231 sshbuf_maybe_pack(buf, max_size < buf->size);
232 if (max_size < buf->alloc && max_size > buf->size) {
233 if (buf->size < SSHBUF_SIZE_INIT)
234 rlen = SSHBUF_SIZE_INIT;
235 else
236 rlen = ROUNDUP(buf->size, SSHBUF_SIZE_INC);
237 if (rlen > max_size)
238 rlen = max_size;
239 SSHBUF_DBG(("new alloc = %zu", rlen));
240 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL)
241 return SSH_ERR_ALLOC_FAIL;
242 buf->cd = buf->d = dp;
243 buf->alloc = rlen;
244 }
245 SSHBUF_TELL("new-max");
246 if (max_size < buf->alloc)
247 return SSH_ERR_NO_BUFFER_SPACE;
248 buf->max_size = max_size;
249 return 0;
250 }
251
252 size_t
sshbuf_len(const struct sshbuf * buf)253 sshbuf_len(const struct sshbuf *buf)
254 {
255 if (sshbuf_check_sanity(buf) != 0)
256 return 0;
257 return buf->size - buf->off;
258 }
259
260 size_t
sshbuf_avail(const struct sshbuf * buf)261 sshbuf_avail(const struct sshbuf *buf)
262 {
263 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
264 return 0;
265 return buf->max_size - (buf->size - buf->off);
266 }
267
268 const u_char *
sshbuf_ptr(const struct sshbuf * buf)269 sshbuf_ptr(const struct sshbuf *buf)
270 {
271 if (sshbuf_check_sanity(buf) != 0)
272 return NULL;
273 return buf->cd + buf->off;
274 }
275
276 u_char *
sshbuf_mutable_ptr(const struct sshbuf * buf)277 sshbuf_mutable_ptr(const struct sshbuf *buf)
278 {
279 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
280 return NULL;
281 return buf->d + buf->off;
282 }
283
284 int
sshbuf_check_reserve(const struct sshbuf * buf,size_t len)285 sshbuf_check_reserve(const struct sshbuf *buf, size_t len)
286 {
287 int r;
288
289 if ((r = sshbuf_check_sanity(buf)) != 0)
290 return r;
291 if (buf->readonly || buf->refcount > 1)
292 return SSH_ERR_BUFFER_READ_ONLY;
293 SSHBUF_TELL("check");
294 /* Check that len is reasonable and that max_size + available < len */
295 if (len > buf->max_size || buf->max_size - len < buf->size - buf->off)
296 return SSH_ERR_NO_BUFFER_SPACE;
297 return 0;
298 }
299
300 int
sshbuf_allocate(struct sshbuf * buf,size_t len)301 sshbuf_allocate(struct sshbuf *buf, size_t len)
302 {
303 size_t rlen, need;
304 u_char *dp;
305 int r;
306
307 SSHBUF_DBG(("allocate buf = %p len = %zu", buf, len));
308 if ((r = sshbuf_check_reserve(buf, len)) != 0)
309 return r;
310 /*
311 * If the requested allocation appended would push us past max_size
312 * then pack the buffer, zeroing buf->off.
313 */
314 sshbuf_maybe_pack(buf, buf->size + len > buf->max_size);
315 SSHBUF_TELL("allocate");
316 if (len + buf->size <= buf->alloc)
317 return 0; /* already have it. */
318
319 /*
320 * Prefer to alloc in SSHBUF_SIZE_INC units, but
321 * allocate less if doing so would overflow max_size.
322 */
323 need = len + buf->size - buf->alloc;
324 rlen = ROUNDUP(buf->alloc + need, SSHBUF_SIZE_INC);
325 SSHBUF_DBG(("need %zu initial rlen %zu", need, rlen));
326 if (rlen > buf->max_size)
327 rlen = buf->alloc + need;
328 SSHBUF_DBG(("adjusted rlen %zu", rlen));
329 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) {
330 SSHBUF_DBG(("realloc fail"));
331 return SSH_ERR_ALLOC_FAIL;
332 }
333 buf->alloc = rlen;
334 buf->cd = buf->d = dp;
335 if ((r = sshbuf_check_reserve(buf, len)) < 0) {
336 /* shouldn't fail */
337 return r;
338 }
339 SSHBUF_TELL("done");
340 return 0;
341 }
342
343 int
sshbuf_reserve(struct sshbuf * buf,size_t len,u_char ** dpp)344 sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp)
345 {
346 u_char *dp;
347 int r;
348
349 if (dpp != NULL)
350 *dpp = NULL;
351
352 SSHBUF_DBG(("reserve buf = %p len = %zu", buf, len));
353 if ((r = sshbuf_allocate(buf, len)) != 0)
354 return r;
355
356 dp = buf->d + buf->size;
357 buf->size += len;
358 if (dpp != NULL)
359 *dpp = dp;
360 return 0;
361 }
362
363 int
sshbuf_consume(struct sshbuf * buf,size_t len)364 sshbuf_consume(struct sshbuf *buf, size_t len)
365 {
366 int r;
367
368 SSHBUF_DBG(("len = %zu", len));
369 if ((r = sshbuf_check_sanity(buf)) != 0)
370 return r;
371 if (len == 0)
372 return 0;
373 if (len > sshbuf_len(buf))
374 return SSH_ERR_MESSAGE_INCOMPLETE;
375 buf->off += len;
376 /* deal with empty buffer */
377 if (buf->off == buf->size)
378 buf->off = buf->size = 0;
379 SSHBUF_TELL("done");
380 return 0;
381 }
382
383 int
sshbuf_consume_end(struct sshbuf * buf,size_t len)384 sshbuf_consume_end(struct sshbuf *buf, size_t len)
385 {
386 int r;
387
388 SSHBUF_DBG(("len = %zu", len));
389 if ((r = sshbuf_check_sanity(buf)) != 0)
390 return r;
391 if (len == 0)
392 return 0;
393 if (len > sshbuf_len(buf))
394 return SSH_ERR_MESSAGE_INCOMPLETE;
395 buf->size -= len;
396 SSHBUF_TELL("done");
397 return 0;
398 }
399
400