1 /* $OpenBSD: sshbuf.c,v 1.15 2020/02/26 13:40:09 jsg 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 static inline int 30 sshbuf_check_sanity(const struct sshbuf *buf) 31 { 32 SSHBUF_TELL("sanity"); 33 if (__predict_false(buf == NULL || 34 (!buf->readonly && buf->d != buf->cd) || 35 buf->refcount < 1 || buf->refcount > SSHBUF_REFS_MAX || 36 buf->cd == NULL || 37 buf->max_size > SSHBUF_SIZE_MAX || 38 buf->alloc > buf->max_size || 39 buf->size > buf->alloc || 40 buf->off > buf->size)) { 41 /* Do not try to recover from corrupted buffer internals */ 42 SSHBUF_DBG(("SSH_ERR_INTERNAL_ERROR")); 43 ssh_signal(SIGSEGV, SIG_DFL); 44 raise(SIGSEGV); 45 return SSH_ERR_INTERNAL_ERROR; 46 } 47 return 0; 48 } 49 50 static void 51 sshbuf_maybe_pack(struct sshbuf *buf, int force) 52 { 53 SSHBUF_DBG(("force %d", force)); 54 SSHBUF_TELL("pre-pack"); 55 if (buf->off == 0 || buf->readonly || buf->refcount > 1) 56 return; 57 if (force || 58 (buf->off >= SSHBUF_PACK_MIN && buf->off >= buf->size / 2)) { 59 memmove(buf->d, buf->d + buf->off, buf->size - buf->off); 60 buf->size -= buf->off; 61 buf->off = 0; 62 SSHBUF_TELL("packed"); 63 } 64 } 65 66 struct sshbuf * 67 sshbuf_new(void) 68 { 69 struct sshbuf *ret; 70 71 if ((ret = calloc(sizeof(*ret), 1)) == NULL) 72 return NULL; 73 ret->alloc = SSHBUF_SIZE_INIT; 74 ret->max_size = SSHBUF_SIZE_MAX; 75 ret->readonly = 0; 76 ret->refcount = 1; 77 ret->parent = NULL; 78 if ((ret->cd = ret->d = calloc(1, ret->alloc)) == NULL) { 79 free(ret); 80 return NULL; 81 } 82 return ret; 83 } 84 85 struct sshbuf * 86 sshbuf_from(const void *blob, size_t len) 87 { 88 struct sshbuf *ret; 89 90 if (blob == NULL || len > SSHBUF_SIZE_MAX || 91 (ret = calloc(sizeof(*ret), 1)) == NULL) 92 return NULL; 93 ret->alloc = ret->size = ret->max_size = len; 94 ret->readonly = 1; 95 ret->refcount = 1; 96 ret->parent = NULL; 97 ret->cd = blob; 98 ret->d = NULL; 99 return ret; 100 } 101 102 int 103 sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent) 104 { 105 int r; 106 107 if ((r = sshbuf_check_sanity(child)) != 0 || 108 (r = sshbuf_check_sanity(parent)) != 0) 109 return r; 110 child->parent = parent; 111 child->parent->refcount++; 112 return 0; 113 } 114 115 struct sshbuf * 116 sshbuf_fromb(struct sshbuf *buf) 117 { 118 struct sshbuf *ret; 119 120 if (sshbuf_check_sanity(buf) != 0) 121 return NULL; 122 if ((ret = sshbuf_from(sshbuf_ptr(buf), sshbuf_len(buf))) == NULL) 123 return NULL; 124 if (sshbuf_set_parent(ret, buf) != 0) { 125 sshbuf_free(ret); 126 return NULL; 127 } 128 return ret; 129 } 130 131 void 132 sshbuf_free(struct sshbuf *buf) 133 { 134 if (buf == NULL) 135 return; 136 /* 137 * The following will leak on insane buffers, but this is the safest 138 * course of action - an invalid pointer or already-freed pointer may 139 * have been passed to us and continuing to scribble over memory would 140 * be bad. 141 */ 142 if (sshbuf_check_sanity(buf) != 0) 143 return; 144 145 /* 146 * If we are a parent with still-extant children, then don't free just 147 * yet. The last child's call to sshbuf_free should decrement our 148 * refcount to 0 and trigger the actual free. 149 */ 150 buf->refcount--; 151 if (buf->refcount > 0) 152 return; 153 154 /* 155 * If we are a child, the free our parent to decrement its reference 156 * count and possibly free it. 157 */ 158 sshbuf_free(buf->parent); 159 buf->parent = NULL; 160 161 if (!buf->readonly) { 162 explicit_bzero(buf->d, buf->alloc); 163 free(buf->d); 164 } 165 freezero(buf, sizeof(*buf)); 166 } 167 168 void 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 191 sshbuf_max_size(const struct sshbuf *buf) 192 { 193 return buf->max_size; 194 } 195 196 size_t 197 sshbuf_alloc(const struct sshbuf *buf) 198 { 199 return buf->alloc; 200 } 201 202 const struct sshbuf * 203 sshbuf_parent(const struct sshbuf *buf) 204 { 205 return buf->parent; 206 } 207 208 u_int 209 sshbuf_refcount(const struct sshbuf *buf) 210 { 211 return buf->refcount; 212 } 213 214 int 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 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 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 * 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 * 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 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 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 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 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 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