1 /* $OpenBSD: sshbuf.c,v 1.13 2018/11/16 06:10:29 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/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 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 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 * 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 * 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 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 * 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 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 /* 148 * If we are a parent with still-extant children, then don't free just 149 * yet. The last child's call to sshbuf_free should decrement our 150 * refcount to 0 and trigger the actual free. 151 */ 152 buf->refcount--; 153 if (buf->refcount > 0) 154 return; 155 156 /* 157 * If we are a child, the free our parent to decrement its reference 158 * count and possibly free it. 159 */ 160 sshbuf_free(buf->parent); 161 buf->parent = NULL; 162 163 if (!buf->readonly) { 164 explicit_bzero(buf->d, buf->alloc); 165 free(buf->d); 166 } 167 explicit_bzero(buf, sizeof(*buf)); 168 free(buf); 169 } 170 171 void 172 sshbuf_reset(struct sshbuf *buf) 173 { 174 u_char *d; 175 176 if (buf->readonly || buf->refcount > 1) { 177 /* Nonsensical. Just make buffer appear empty */ 178 buf->off = buf->size; 179 return; 180 } 181 (void) sshbuf_check_sanity(buf); 182 buf->off = buf->size = 0; 183 if (buf->alloc != SSHBUF_SIZE_INIT) { 184 if ((d = recallocarray(buf->d, buf->alloc, SSHBUF_SIZE_INIT, 185 1)) != NULL) { 186 buf->cd = buf->d = d; 187 buf->alloc = SSHBUF_SIZE_INIT; 188 } 189 } 190 explicit_bzero(buf->d, SSHBUF_SIZE_INIT); 191 } 192 193 size_t 194 sshbuf_max_size(const struct sshbuf *buf) 195 { 196 return buf->max_size; 197 } 198 199 size_t 200 sshbuf_alloc(const struct sshbuf *buf) 201 { 202 return buf->alloc; 203 } 204 205 const struct sshbuf * 206 sshbuf_parent(const struct sshbuf *buf) 207 { 208 return buf->parent; 209 } 210 211 u_int 212 sshbuf_refcount(const struct sshbuf *buf) 213 { 214 return buf->refcount; 215 } 216 217 int 218 sshbuf_set_max_size(struct sshbuf *buf, size_t max_size) 219 { 220 size_t rlen; 221 u_char *dp; 222 int r; 223 224 SSHBUF_DBG(("set max buf = %p len = %zu", buf, max_size)); 225 if ((r = sshbuf_check_sanity(buf)) != 0) 226 return r; 227 if (max_size == buf->max_size) 228 return 0; 229 if (buf->readonly || buf->refcount > 1) 230 return SSH_ERR_BUFFER_READ_ONLY; 231 if (max_size > SSHBUF_SIZE_MAX) 232 return SSH_ERR_NO_BUFFER_SPACE; 233 /* pack and realloc if necessary */ 234 sshbuf_maybe_pack(buf, max_size < buf->size); 235 if (max_size < buf->alloc && max_size > buf->size) { 236 if (buf->size < SSHBUF_SIZE_INIT) 237 rlen = SSHBUF_SIZE_INIT; 238 else 239 rlen = ROUNDUP(buf->size, SSHBUF_SIZE_INC); 240 if (rlen > max_size) 241 rlen = max_size; 242 SSHBUF_DBG(("new alloc = %zu", rlen)); 243 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) 244 return SSH_ERR_ALLOC_FAIL; 245 buf->cd = buf->d = dp; 246 buf->alloc = rlen; 247 } 248 SSHBUF_TELL("new-max"); 249 if (max_size < buf->alloc) 250 return SSH_ERR_NO_BUFFER_SPACE; 251 buf->max_size = max_size; 252 return 0; 253 } 254 255 size_t 256 sshbuf_len(const struct sshbuf *buf) 257 { 258 if (sshbuf_check_sanity(buf) != 0) 259 return 0; 260 return buf->size - buf->off; 261 } 262 263 size_t 264 sshbuf_avail(const struct sshbuf *buf) 265 { 266 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1) 267 return 0; 268 return buf->max_size - (buf->size - buf->off); 269 } 270 271 const u_char * 272 sshbuf_ptr(const struct sshbuf *buf) 273 { 274 if (sshbuf_check_sanity(buf) != 0) 275 return NULL; 276 return buf->cd + buf->off; 277 } 278 279 u_char * 280 sshbuf_mutable_ptr(const struct sshbuf *buf) 281 { 282 if (sshbuf_check_sanity(buf) != 0 || buf->readonly || buf->refcount > 1) 283 return NULL; 284 return buf->d + buf->off; 285 } 286 287 int 288 sshbuf_check_reserve(const struct sshbuf *buf, size_t len) 289 { 290 int r; 291 292 if ((r = sshbuf_check_sanity(buf)) != 0) 293 return r; 294 if (buf->readonly || buf->refcount > 1) 295 return SSH_ERR_BUFFER_READ_ONLY; 296 SSHBUF_TELL("check"); 297 /* Check that len is reasonable and that max_size + available < len */ 298 if (len > buf->max_size || buf->max_size - len < buf->size - buf->off) 299 return SSH_ERR_NO_BUFFER_SPACE; 300 return 0; 301 } 302 303 int 304 sshbuf_allocate(struct sshbuf *buf, size_t len) 305 { 306 size_t rlen, need; 307 u_char *dp; 308 int r; 309 310 SSHBUF_DBG(("allocate buf = %p len = %zu", buf, len)); 311 if ((r = sshbuf_check_reserve(buf, len)) != 0) 312 return r; 313 /* 314 * If the requested allocation appended would push us past max_size 315 * then pack the buffer, zeroing buf->off. 316 */ 317 sshbuf_maybe_pack(buf, buf->size + len > buf->max_size); 318 SSHBUF_TELL("allocate"); 319 if (len + buf->size <= buf->alloc) 320 return 0; /* already have it. */ 321 322 /* 323 * Prefer to alloc in SSHBUF_SIZE_INC units, but 324 * allocate less if doing so would overflow max_size. 325 */ 326 need = len + buf->size - buf->alloc; 327 rlen = ROUNDUP(buf->alloc + need, SSHBUF_SIZE_INC); 328 SSHBUF_DBG(("need %zu initial rlen %zu", need, rlen)); 329 if (rlen > buf->max_size) 330 rlen = buf->alloc + need; 331 SSHBUF_DBG(("adjusted rlen %zu", rlen)); 332 if ((dp = recallocarray(buf->d, buf->alloc, rlen, 1)) == NULL) { 333 SSHBUF_DBG(("realloc fail")); 334 return SSH_ERR_ALLOC_FAIL; 335 } 336 buf->alloc = rlen; 337 buf->cd = buf->d = dp; 338 if ((r = sshbuf_check_reserve(buf, len)) < 0) { 339 /* shouldn't fail */ 340 return r; 341 } 342 SSHBUF_TELL("done"); 343 return 0; 344 } 345 346 int 347 sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp) 348 { 349 u_char *dp; 350 int r; 351 352 if (dpp != NULL) 353 *dpp = NULL; 354 355 SSHBUF_DBG(("reserve buf = %p len = %zu", buf, len)); 356 if ((r = sshbuf_allocate(buf, len)) != 0) 357 return r; 358 359 dp = buf->d + buf->size; 360 buf->size += len; 361 if (dpp != NULL) 362 *dpp = dp; 363 return 0; 364 } 365 366 int 367 sshbuf_consume(struct sshbuf *buf, size_t len) 368 { 369 int r; 370 371 SSHBUF_DBG(("len = %zu", len)); 372 if ((r = sshbuf_check_sanity(buf)) != 0) 373 return r; 374 if (len == 0) 375 return 0; 376 if (len > sshbuf_len(buf)) 377 return SSH_ERR_MESSAGE_INCOMPLETE; 378 buf->off += len; 379 /* deal with empty buffer */ 380 if (buf->off == buf->size) 381 buf->off = buf->size = 0; 382 SSHBUF_TELL("done"); 383 return 0; 384 } 385 386 int 387 sshbuf_consume_end(struct sshbuf *buf, size_t len) 388 { 389 int r; 390 391 SSHBUF_DBG(("len = %zu", len)); 392 if ((r = sshbuf_check_sanity(buf)) != 0) 393 return r; 394 if (len == 0) 395 return 0; 396 if (len > sshbuf_len(buf)) 397 return SSH_ERR_MESSAGE_INCOMPLETE; 398 buf->size -= len; 399 SSHBUF_TELL("done"); 400 return 0; 401 } 402 403