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1/* $OpenBSD: sshbuf.c,v 1.24 2025/12/29 23:52:09 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#include <sys/types.h>
19#include <signal.h>
20#include <stdlib.h>
21#include <stdio.h>
22#include <string.h>
23
24#include "ssherr.h"
25#define SSHBUF_INTERNAL
26#include "sshbuf.h"
27#include "misc.h"
28
29#ifdef SSHBUF_DEBUG
30# define SSHBUF_TELL(what) do { \
31 printf("%s:%d %s: %s size %zu alloc %zu off %zu max %zu\n", \
32 __FILE__, __LINE__, __func__, what, \
33 buf->size, buf->alloc, buf->off, buf->max_size); \
34 fflush(stdout); \
35 } while (0)
36#else
37# define SSHBUF_TELL(what)
38#endif
39
40struct sshbuf {
41 u_char *d; /* Data */
42 const u_char *cd; /* Const data */
43 size_t off; /* First available byte is buf->d + buf->off */
44 size_t size; /* Last byte is buf->d + buf->size - 1 */
45 size_t max_size; /* Maximum size of buffer */
46 size_t alloc; /* Total bytes allocated to buf->d */
47 int readonly; /* Refers to external, const data */
48 u_int refcount; /* Tracks self and number of child buffers */
49 struct sshbuf *parent; /* If child, pointer to parent */
50};
51
52static inline int
53sshbuf_check_sanity(const struct sshbuf *buf)
54{
55 SSHBUF_TELL("sanity");
56 if (__predict_false(buf == NULL ||
57 (!buf->readonly && buf->d != buf->cd) ||
58 buf->parent == buf ||
59 buf->refcount < 1 || buf->refcount > SSHBUF_REFS_MAX ||
60 buf->cd == NULL ||
61 buf->max_size > SSHBUF_SIZE_MAX ||
62 buf->alloc > buf->max_size ||
63 buf->size > buf->alloc ||
64 buf->off > buf->size)) {
65 /* Do not try to recover from corrupted buffer internals */
66 SSHBUF_DBG(("SSH_ERR_INTERNAL_ERROR"));
67 ssh_signal(SIGSEGV, SIG_DFL);
68 raise(SIGSEGV);
69 return SSH_ERR_INTERNAL_ERROR;
70 }
71 return 0;
72}
73
74static void
75sshbuf_maybe_pack(struct sshbuf *buf, int force)
76{
77 SSHBUF_DBG(("force %d", force));
78 SSHBUF_TELL("pre-pack");
79 if (buf->off == 0 || buf->readonly || buf->refcount > 1)
80 return;
81 if (force ||
82 (buf->off >= SSHBUF_PACK_MIN && buf->off >= buf->size / 2)) {
83 memmove(buf->d, buf->d + buf->off, buf->size - buf->off);
84 buf->size -= buf->off;
85 buf->off = 0;
86 SSHBUF_TELL("packed");
87 }
88}
89
90struct sshbuf *
91sshbuf_new(void)
92{
93 struct sshbuf *ret;
94
95 if ((ret = calloc(1, sizeof(*ret))) == NULL)
96 return NULL;
97 ret->alloc = SSHBUF_SIZE_INIT;
98 ret->max_size = SSHBUF_SIZE_MAX;
99 ret->readonly = 0;
100 ret->refcount = 1;
101 ret->parent = NULL;
102 if ((ret->cd = ret->d = calloc(1, ret->alloc)) == NULL) {
103 free(ret);
104 return NULL;
105 }
106 return ret;
107}
108
109struct sshbuf *
110sshbuf_from(const void *blob, size_t len)
111{
112 struct sshbuf *ret;
113
114 if (blob == NULL || len > SSHBUF_SIZE_MAX ||
115 (ret = calloc(1, sizeof(*ret))) == NULL)
116 return NULL;
117 ret->alloc = ret->size = ret->max_size = len;
118 ret->readonly = 1;
119 ret->refcount = 1;
120 ret->parent = NULL;
121 ret->cd = blob;
122 ret->d = NULL;
123 return ret;
124}
125
126int
127sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent)
128{
129 int r;
130
131 if ((r = sshbuf_check_sanity(child)) != 0 ||
132 (r = sshbuf_check_sanity(parent)) != 0)
133 return r;
134 if ((child->parent != NULL && child->parent != parent) ||
135 child == parent)
136 return SSH_ERR_INTERNAL_ERROR;
137 child->parent = parent;
138 child->parent->refcount++;
139 return 0;
140}
141
142struct sshbuf *
143sshbuf_fromb(struct sshbuf *buf)
144{
145 struct sshbuf *ret;
146
147 if (sshbuf_check_sanity(buf) != 0)
148 return NULL;
149 if ((ret = sshbuf_from(sshbuf_ptr(buf), sshbuf_len(buf))) == NULL)
150 return NULL;
151 if (sshbuf_set_parent(ret, buf) != 0) {
152 sshbuf_free(ret);
153 return NULL;
154 }
155 return ret;
156}
157
158void
159sshbuf_free(struct sshbuf *buf)
160{
161 if (buf == NULL)
162 return;
163 /*
164 * The following will leak on insane buffers, but this is the safest
165 * course of action - an invalid pointer or already-freed pointer may
166 * have been passed to us and continuing to scribble over memory would
167 * be bad.
168 */
169 if (sshbuf_check_sanity(buf) != 0)
170 return;
171
172 /*
173 * If we are a parent with still-extant children, then don't free just
174 * yet. The last child's call to sshbuf_free should decrement our
175 * refcount to 0 and trigger the actual free.
176 */
177 buf->refcount--;
178 if (buf->refcount > 0)
179 return;
180
181 /*
182 * If we are a child, then free our parent to decrement its reference
183 * count and possibly free it.
184 */
185 sshbuf_free(buf->parent);
186 buf->parent = NULL;
187
188 if (!buf->readonly)
189 freezero(buf->d, buf->alloc);
190 freezero(buf, sizeof(*buf));
191}
192
193void
194sshbuf_reset(struct sshbuf *buf)
195{
196 u_char *d;
197
198 if (buf->readonly || buf->refcount > 1) {
199 /* Nonsensical. Just make buffer appear empty */
200 buf->off = buf->size;
201 return;
202 }
203 if (sshbuf_check_sanity(buf) != 0)
204 return;
205 buf->off = buf->size = 0;
206 if (buf->alloc != SSHBUF_SIZE_INIT) {
207 if ((d = recallocarray(buf->d, buf->alloc, SSHBUF_SIZE_INIT,
208 1)) != NULL) {
209 buf->cd = buf->d = d;
210 buf->alloc = SSHBUF_SIZE_INIT;
211 }
212 }
213 explicit_bzero(buf->d, buf->alloc);
214}
215
216size_t
217sshbuf_max_size(const struct sshbuf *buf)
218{
219 return buf->max_size;
220}
221
222size_t
223sshbuf_alloc(const struct sshbuf *buf)
224{
225 return buf->alloc;
226}
227
228const struct sshbuf *
229sshbuf_parent(const struct sshbuf *buf)
230{
231 return buf->parent;
232}
233
234u_int
235sshbuf_refcount(const struct sshbuf *buf)
236{
237 return buf->refcount;
238}
239
240int
241sshbuf_set_max_size(struct sshbuf *buf, size_t max_size)
242{
243 size_t rlen;
244 u_char *dp;
245 int r;
246
247 SSHBUF_DBG(("set max buf = %p len = %zu", buf, max_size));
248 if ((r = sshbuf_check_sanity(buf)) != 0)
249 return r;
250 if (max_size == buf->max_size)
251 return 0;
252 if (buf->readonly || buf->refcount > 1)
253 return SSH_ERR_BUFFER_READ_ONLY;
254 if (max_size > SSHBUF_SIZE_MAX)
255 return SSH_ERR_NO_BUFFER_SPACE;
256 /* pack and realloc if necessary */
257 sshbuf_maybe_pack(buf, max_size < buf->size);
258 if (max_size < buf->alloc && max_size > buf->size) {
259 if (buf->size < SSHBUF_SIZE_INIT)
260 rlen = SSHBUF_SIZE_INIT;
261 else
262 rlen = ROUNDUP(buf->size, SSHBUF_SIZE_INC);
263 if (rlen > max_size)
264 rlen = max_size;
265 SSHBUF_DBG(("new alloc = %zu", rlen));
266 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL)
267 return SSH_ERR_ALLOC_FAIL;
268 buf->cd = buf->d = dp;
269 buf->alloc = rlen;
270 }
271 SSHBUF_TELL("new-max");
272 if (max_size < buf->alloc)
273 return SSH_ERR_NO_BUFFER_SPACE;
274 buf->max_size = max_size;
275 return 0;
276}
277
278size_t
279sshbuf_len(const struct sshbuf *buf)
280{
281 if (sshbuf_check_sanity(buf) != 0)
282 return 0;
283 return buf->size - buf->off;
284}
285
286size_t
287sshbuf_avail(const struct sshbuf *buf)
288{
289 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
290 return 0;
291 return buf->max_size - (buf->size - buf->off);
292}
293
294const u_char *
295sshbuf_ptr(const struct sshbuf *buf)
296{
297 if (sshbuf_check_sanity(buf) != 0)
298 return NULL;
299 return buf->cd + buf->off;
300}
301
302u_char *
303sshbuf_mutable_ptr(const struct sshbuf *buf)
304{
305 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1)
306 return NULL;
307 return buf->d + buf->off;
308}
309
310int
311sshbuf_check_reserve(const struct sshbuf *buf, size_t len)
312{
313 int r;
314
315 if ((r = sshbuf_check_sanity(buf)) != 0)
316 return r;
317 if (buf->readonly || buf->refcount > 1)
318 return SSH_ERR_BUFFER_READ_ONLY;
319 SSHBUF_TELL("check");
320 /* Check that len is reasonable and that max_size + available < len */
321 if (len > buf->max_size || buf->max_size - len < buf->size - buf->off)
322 return SSH_ERR_NO_BUFFER_SPACE;
323 return 0;
324}
325
326int
327sshbuf_allocate(struct sshbuf *buf, size_t len)
328{
329 size_t rlen, need;
330 u_char *dp;
331 int r;
332
333 SSHBUF_DBG(("allocate buf = %p len = %zu", buf, len));
334 if ((r = sshbuf_check_reserve(buf, len)) != 0)
335 return r;
336 /*
337 * If the requested allocation appended would push us past max_size
338 * then pack the buffer, zeroing buf->off.
339 */
340 sshbuf_maybe_pack(buf, buf->size + len > buf->max_size);
341 SSHBUF_TELL("allocate");
342 if (len + buf->size <= buf->alloc)
343 return 0; /* already have it. */
344
345 /*
346 * Prefer to alloc in SSHBUF_SIZE_INC units, but
347 * allocate less if doing so would overflow max_size.
348 */
349 need = len + buf->size - buf->alloc;
350 rlen = ROUNDUP(buf->alloc + need, SSHBUF_SIZE_INC);
351 SSHBUF_DBG(("need %zu initial rlen %zu", need, rlen));
352 if (rlen > buf->max_size)
353 rlen = buf->alloc + need;
354 SSHBUF_DBG(("adjusted rlen %zu", rlen));
355 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) {
356 SSHBUF_DBG(("realloc fail"));
357 return SSH_ERR_ALLOC_FAIL;
358 }
359 buf->alloc = rlen;
360 buf->cd = buf->d = dp;
361 if ((r = sshbuf_check_reserve(buf, len)) < 0) {
362 /* shouldn't fail */
363 return r;
364 }
365 SSHBUF_TELL("done");
366 return 0;
367}
368
369int
370sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp)
371{
372 u_char *dp;
373 int r;
374
375 if (dpp != NULL)
376 *dpp = NULL;
377
378 SSHBUF_DBG(("reserve buf = %p len = %zu", buf, len));
379 if ((r = sshbuf_allocate(buf, len)) != 0)
380 return r;
381
382 dp = buf->d + buf->size;
383 buf->size += len;
384 if (dpp != NULL)
385 *dpp = dp;
386 return 0;
387}
388
389int
390sshbuf_consume(struct sshbuf *buf, size_t len)
391{
392 int r;
393
394 SSHBUF_DBG(("len = %zu", len));
395 if ((r = sshbuf_check_sanity(buf)) != 0)
396 return r;
397 if (len == 0)
398 return 0;
399 if (len > sshbuf_len(buf))
400 return SSH_ERR_MESSAGE_INCOMPLETE;
401 buf->off += len;
402 /* deal with empty buffer */
403 if (buf->off == buf->size)
404 buf->off = buf->size = 0;
405 SSHBUF_TELL("done");
406 return 0;
407}
408
409int
410sshbuf_consume_end(struct sshbuf *buf, size_t len)
411{
412 int r;
413
414 SSHBUF_DBG(("len = %zu", len));
415 if ((r = sshbuf_check_sanity(buf)) != 0)
416 return r;
417 if (len == 0)
418 return 0;
419 if (len > sshbuf_len(buf))
420 return SSH_ERR_MESSAGE_INCOMPLETE;
421 buf->size -= len;
422 SSHBUF_TELL("done");
423 return 0;
424}
425
426int
427sshbuf_consume_upto_child(struct sshbuf *buf, const struct sshbuf *child)
428{
429 int r;
430
431 if ((r = sshbuf_check_sanity(buf)) != 0 ||
432 (r = sshbuf_check_sanity(child)) != 0)
433 return r;
434 /* This function is only used for parent/child buffers */
435 if (child->parent != buf)
436 return SSH_ERR_INVALID_ARGUMENT;
437 /* Nonsensical if the parent has advanced past the child */
438 if (sshbuf_len(child) > sshbuf_len(buf))
439 return SSH_ERR_INVALID_ARGUMENT;
440 /* More paranoia, shouldn't happen */
441 if (child->cd < buf->cd)
442 return SSH_ERR_INTERNAL_ERROR;
443 /* Advance */
444 return sshbuf_consume(buf, sshbuf_len(buf) - sshbuf_len(child));
445}