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 #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 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 * If we are a child, the free our parent to decrement its reference 146 * count and possibly free it. 147 */ 148 sshbuf_free(buf->parent); 149 buf->parent = NULL; 150 /* 151 * If we are a parent with still-extant children, then don't free just 152 * yet. The last child's call to sshbuf_free should decrement our 153 * refcount to 0 and trigger the actual free. 154 */ 155 buf->refcount--; 156 if (buf->refcount > 0) 157 return; 158 if (!buf->readonly) { 159 explicit_bzero(buf->d, buf->alloc); 160 free(buf->d); 161 } 162 explicit_bzero(buf, sizeof(*buf)); 163 free(buf); 164 } 165 166 void 167 sshbuf_reset(struct sshbuf *buf) 168 { 169 u_char *d; 170 171 if (buf->readonly || buf->refcount > 1) { 172 /* Nonsensical. Just make buffer appear empty */ 173 buf->off = buf->size; 174 return; 175 } 176 (void) sshbuf_check_sanity(buf); 177 buf->off = buf->size = 0; 178 if (buf->alloc != SSHBUF_SIZE_INIT) { 179 if ((d = recallocarray(buf->d, buf->alloc, SSHBUF_SIZE_INIT, 180 1)) != NULL) { 181 buf->cd = buf->d = d; 182 buf->alloc = SSHBUF_SIZE_INIT; 183 } 184 } 185 explicit_bzero(buf->d, SSHBUF_SIZE_INIT); 186 } 187 188 size_t 189 sshbuf_max_size(const struct sshbuf *buf) 190 { 191 return buf->max_size; 192 } 193 194 size_t 195 sshbuf_alloc(const struct sshbuf *buf) 196 { 197 return buf->alloc; 198 } 199 200 const struct sshbuf * 201 sshbuf_parent(const struct sshbuf *buf) 202 { 203 return buf->parent; 204 } 205 206 u_int 207 sshbuf_refcount(const struct sshbuf *buf) 208 { 209 return buf->refcount; 210 } 211 212 int 213 sshbuf_set_max_size(struct sshbuf *buf, size_t max_size) 214 { 215 size_t rlen; 216 u_char *dp; 217 int r; 218 219 SSHBUF_DBG(("set max buf = %p len = %zu", buf, max_size)); 220 if ((r = sshbuf_check_sanity(buf)) != 0) 221 return r; 222 if (max_size == buf->max_size) 223 return 0; 224 if (buf->readonly || buf->refcount > 1) 225 return SSH_ERR_BUFFER_READ_ONLY; 226 if (max_size > SSHBUF_SIZE_MAX) 227 return SSH_ERR_NO_BUFFER_SPACE; 228 /* pack and realloc if necessary */ 229 sshbuf_maybe_pack(buf, max_size < buf->size); 230 if (max_size < buf->alloc && max_size > buf->size) { 231 if (buf->size < SSHBUF_SIZE_INIT) 232 rlen = SSHBUF_SIZE_INIT; 233 else 234 rlen = ROUNDUP(buf->size, SSHBUF_SIZE_INC); 235 if (rlen > max_size) 236 rlen = max_size; 237 SSHBUF_DBG(("new alloc = %zu", rlen)); 238 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) 239 return SSH_ERR_ALLOC_FAIL; 240 buf->cd = buf->d = dp; 241 buf->alloc = rlen; 242 } 243 SSHBUF_TELL("new-max"); 244 if (max_size < buf->alloc) 245 return SSH_ERR_NO_BUFFER_SPACE; 246 buf->max_size = max_size; 247 return 0; 248 } 249 250 size_t 251 sshbuf_len(const struct sshbuf *buf) 252 { 253 if (sshbuf_check_sanity(buf) != 0) 254 return 0; 255 return buf->size - buf->off; 256 } 257 258 size_t 259 sshbuf_avail(const struct sshbuf *buf) 260 { 261 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1) 262 return 0; 263 return buf->max_size - (buf->size - buf->off); 264 } 265 266 const u_char * 267 sshbuf_ptr(const struct sshbuf *buf) 268 { 269 if (sshbuf_check_sanity(buf) != 0) 270 return NULL; 271 return buf->cd + buf->off; 272 } 273 274 u_char * 275 sshbuf_mutable_ptr(const struct sshbuf *buf) 276 { 277 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1) 278 return NULL; 279 return buf->d + buf->off; 280 } 281 282 int 283 sshbuf_check_reserve(const struct sshbuf *buf, size_t len) 284 { 285 int r; 286 287 if ((r = sshbuf_check_sanity(buf)) != 0) 288 return r; 289 if (buf->readonly || buf->refcount > 1) 290 return SSH_ERR_BUFFER_READ_ONLY; 291 SSHBUF_TELL("check"); 292 /* Check that len is reasonable and that max_size + available < len */ 293 if (len > buf->max_size || buf->max_size - len < buf->size - buf->off) 294 return SSH_ERR_NO_BUFFER_SPACE; 295 return 0; 296 } 297 298 int 299 sshbuf_allocate(struct sshbuf *buf, size_t len) 300 { 301 size_t rlen, need; 302 u_char *dp; 303 int r; 304 305 SSHBUF_DBG(("allocate buf = %p len = %zu", buf, len)); 306 if ((r = sshbuf_check_reserve(buf, len)) != 0) 307 return r; 308 /* 309 * If the requested allocation appended would push us past max_size 310 * then pack the buffer, zeroing buf->off. 311 */ 312 sshbuf_maybe_pack(buf, buf->size + len > buf->max_size); 313 SSHBUF_TELL("allocate"); 314 if (len + buf->size <= buf->alloc) 315 return 0; /* already have it. */ 316 317 /* 318 * Prefer to alloc in SSHBUF_SIZE_INC units, but 319 * allocate less if doing so would overflow max_size. 320 */ 321 need = len + buf->size - buf->alloc; 322 rlen = ROUNDUP(buf->alloc + need, SSHBUF_SIZE_INC); 323 SSHBUF_DBG(("need %zu initial rlen %zu", need, rlen)); 324 if (rlen > buf->max_size) 325 rlen = buf->alloc + need; 326 SSHBUF_DBG(("adjusted rlen %zu", rlen)); 327 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) { 328 SSHBUF_DBG(("realloc fail")); 329 return SSH_ERR_ALLOC_FAIL; 330 } 331 buf->alloc = rlen; 332 buf->cd = buf->d = dp; 333 if ((r = sshbuf_check_reserve(buf, len)) < 0) { 334 /* shouldn't fail */ 335 return r; 336 } 337 SSHBUF_TELL("done"); 338 return 0; 339 } 340 341 int 342 sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp) 343 { 344 u_char *dp; 345 int r; 346 347 if (dpp != NULL) 348 *dpp = NULL; 349 350 SSHBUF_DBG(("reserve buf = %p len = %zu", buf, len)); 351 if ((r = sshbuf_allocate(buf, len)) != 0) 352 return r; 353 354 dp = buf->d + buf->size; 355 buf->size += len; 356 if (dpp != NULL) 357 *dpp = dp; 358 return 0; 359 } 360 361 int 362 sshbuf_consume(struct sshbuf *buf, size_t len) 363 { 364 int r; 365 366 SSHBUF_DBG(("len = %zu", len)); 367 if ((r = sshbuf_check_sanity(buf)) != 0) 368 return r; 369 if (len == 0) 370 return 0; 371 if (len > sshbuf_len(buf)) 372 return SSH_ERR_MESSAGE_INCOMPLETE; 373 buf->off += len; 374 /* deal with empty buffer */ 375 if (buf->off == buf->size) 376 buf->off = buf->size = 0; 377 SSHBUF_TELL("done"); 378 return 0; 379 } 380 381 int 382 sshbuf_consume_end(struct sshbuf *buf, size_t len) 383 { 384 int r; 385 386 SSHBUF_DBG(("len = %zu", len)); 387 if ((r = sshbuf_check_sanity(buf)) != 0) 388 return r; 389 if (len == 0) 390 return 0; 391 if (len > sshbuf_len(buf)) 392 return SSH_ERR_MESSAGE_INCOMPLETE; 393 buf->size -= len; 394 SSHBUF_TELL("done"); 395 return 0; 396 } 397 398