crypto/mem_sec.c

   1 /*
   2  * Copyright 2015-2022 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright 2004-2014, Akamai Technologies. All Rights Reserved.
   4  *
   5  * Licensed under the Apache License 2.0 (the "License").  You may not use
   6  * this file except in compliance with the License.  You can obtain a copy
   7  * in the file LICENSE in the source distribution or at
   8  * https://www.openssl.org/source/license.html
   9  */
  10
  11 /*
  12  * This file is in two halves. The first half implements the public API
  13  * to be used by external consumers, and to be used by OpenSSL to store
  14  * data in a "secure arena." The second half implements the secure arena.
  15  * For details on that implementation, see below (look for uppercase
  16  * "SECURE HEAP IMPLEMENTATION").
  17  */
  18 #include "internal/e_os.h"
  19 #include <openssl/crypto.h>
  20
  21 #include <string.h>
  22
  23 #ifndef OPENSSL_NO_SECURE_MEMORY
  24 # if defined(_WIN32)
  25 #  include <windows.h>
  26 #  if defined(WINAPI_FAMILY_PARTITION) \
  27      && !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP | WINAPI_PARTITION_SYSTEM)
  28 /*
  29  * While VirtualLock is available under the app partition (e.g. UWP),
  30  * the headers do not define the API. Define it ourselves instead.
  31  */
  32 WINBASEAPI
  33 BOOL
  34 WINAPI
  35 VirtualLock(
  36     _In_ LPVOID lpAddress,
  37     _In_ SIZE_T dwSize
  38     );
  39 #  endif
  40 # endif
  41 # include <stdlib.h>
  42 # include <assert.h>
  43 # if defined(OPENSSL_SYS_UNIX)
  44 #  include <unistd.h>
  45 # endif
  46 # include <sys/types.h>
  47 # if defined(OPENSSL_SYS_UNIX)
  48 #  include <sys/mman.h>
  49 #  if defined(__FreeBSD__)
  50 #    define MADV_DONTDUMP MADV_NOCORE
  51 #  endif
  52 #  if !defined(MAP_CONCEAL)
  53 #    define MAP_CONCEAL 0
  54 #  endif
  55 # endif
  56 # if defined(OPENSSL_SYS_LINUX)
  57 #  include <sys/syscall.h>
  58 #  if defined(SYS_mlock2)
  59 #   include <linux/mman.h>
  60 #   include <errno.h>
  61 #  endif
  62 #  include <sys/param.h>
  63 # endif
  64 # include <sys/stat.h>
  65 # include <fcntl.h>
  66 #endif
  67
  68 #define CLEAR(p, s) OPENSSL_cleanse(p, s)
  69 #ifndef PAGE_SIZE
  70 # define PAGE_SIZE    4096
  71 #endif
  72 #if !defined(MAP_ANON) && defined(MAP_ANONYMOUS)
  73 # define MAP_ANON MAP_ANONYMOUS
  74 #endif
  75
  76 #ifndef OPENSSL_NO_SECURE_MEMORY
  77 static size_t secure_mem_used;
  78
  79 static int secure_mem_initialized;
  80
  81 static CRYPTO_RWLOCK *sec_malloc_lock = NULL;
  82
  83 /*
  84  * These are the functions that must be implemented by a secure heap (sh).
  85  */
  86 static int sh_init(size_t size, size_t minsize);
  87 static void *sh_malloc(size_t size);
  88 static void sh_free(void *ptr);
  89 static void sh_done(void);
  90 static size_t sh_actual_size(char *ptr);
  91 static int sh_allocated(const char *ptr);
  92 #endif
  93
  94 int CRYPTO_secure_malloc_init(size_t size, size_t minsize)
  95 {
  96 #ifndef OPENSSL_NO_SECURE_MEMORY
  97     int ret = 0;
  98
  99     if (!secure_mem_initialized) {
 100         sec_malloc_lock = CRYPTO_THREAD_lock_new();
 101         if (sec_malloc_lock == NULL)
 102             return 0;
 103         if ((ret = sh_init(size, minsize)) != 0) {
 104             secure_mem_initialized = 1;
 105         } else {
 106             CRYPTO_THREAD_lock_free(sec_malloc_lock);
 107             sec_malloc_lock = NULL;
 108         }
 109     }
 110
 111     return ret;
 112 #else
 113     return 0;
 114 #endif /* OPENSSL_NO_SECURE_MEMORY */
 115 }
 116
 117 int CRYPTO_secure_malloc_done(void)
 118 {
 119 #ifndef OPENSSL_NO_SECURE_MEMORY
 120     if (secure_mem_used == 0) {
 121         sh_done();
 122         secure_mem_initialized = 0;
 123         CRYPTO_THREAD_lock_free(sec_malloc_lock);
 124         sec_malloc_lock = NULL;
 125         return 1;
 126     }
 127 #endif /* OPENSSL_NO_SECURE_MEMORY */
 128     return 0;
 129 }
 130
 131 int CRYPTO_secure_malloc_initialized(void)
 132 {
 133 #ifndef OPENSSL_NO_SECURE_MEMORY
 134     return secure_mem_initialized;
 135 #else
 136     return 0;
 137 #endif /* OPENSSL_NO_SECURE_MEMORY */
 138 }
 139
 140 void *CRYPTO_secure_malloc(size_t num, const char *file, int line)
 141 {
 142 #ifndef OPENSSL_NO_SECURE_MEMORY
 143     void *ret;
 144     size_t actual_size;
 145
 146     if (!secure_mem_initialized) {
 147         return CRYPTO_malloc(num, file, line);
 148     }
 149     if (!CRYPTO_THREAD_write_lock(sec_malloc_lock))
 150         return NULL;
 151     ret = sh_malloc(num);
 152     actual_size = ret ? sh_actual_size(ret) : 0;
 153     secure_mem_used += actual_size;
 154     CRYPTO_THREAD_unlock(sec_malloc_lock);
 155     return ret;
 156 #else
 157     return CRYPTO_malloc(num, file, line);
 158 #endif /* OPENSSL_NO_SECURE_MEMORY */
 159 }
 160
 161 void *CRYPTO_secure_zalloc(size_t num, const char *file, int line)
 162 {
 163 #ifndef OPENSSL_NO_SECURE_MEMORY
 164     if (secure_mem_initialized)
 165         /* CRYPTO_secure_malloc() zeroes allocations when it is implemented */
 166         return CRYPTO_secure_malloc(num, file, line);
 167 #endif
 168     return CRYPTO_zalloc(num, file, line);
 169 }
 170
 171 void CRYPTO_secure_free(void *ptr, const char *file, int line)
 172 {
 173 #ifndef OPENSSL_NO_SECURE_MEMORY
 174     size_t actual_size;
 175
 176     if (ptr == NULL)
 177         return;
 178     if (!CRYPTO_secure_allocated(ptr)) {
 179         CRYPTO_free(ptr, file, line);
 180         return;
 181     }
 182     if (!CRYPTO_THREAD_write_lock(sec_malloc_lock))
 183         return;
 184     actual_size = sh_actual_size(ptr);
 185     CLEAR(ptr, actual_size);
 186     secure_mem_used -= actual_size;
 187     sh_free(ptr);
 188     CRYPTO_THREAD_unlock(sec_malloc_lock);
 189 #else
 190     CRYPTO_free(ptr, file, line);
 191 #endif /* OPENSSL_NO_SECURE_MEMORY */
 192 }
 193
 194 void CRYPTO_secure_clear_free(void *ptr, size_t num,
 195                               const char *file, int line)
 196 {
 197 #ifndef OPENSSL_NO_SECURE_MEMORY
 198     size_t actual_size;
 199
 200     if (ptr == NULL)
 201         return;
 202     if (!CRYPTO_secure_allocated(ptr)) {
 203         OPENSSL_cleanse(ptr, num);
 204         CRYPTO_free(ptr, file, line);
 205         return;
 206     }
 207     if (!CRYPTO_THREAD_write_lock(sec_malloc_lock))
 208         return;
 209     actual_size = sh_actual_size(ptr);
 210     CLEAR(ptr, actual_size);
 211     secure_mem_used -= actual_size;
 212     sh_free(ptr);
 213     CRYPTO_THREAD_unlock(sec_malloc_lock);
 214 #else
 215     if (ptr == NULL)
 216         return;
 217     OPENSSL_cleanse(ptr, num);
 218     CRYPTO_free(ptr, file, line);
 219 #endif /* OPENSSL_NO_SECURE_MEMORY */
 220 }
 221
 222 int CRYPTO_secure_allocated(const void *ptr)
 223 {
 224 #ifndef OPENSSL_NO_SECURE_MEMORY
 225     if (!secure_mem_initialized)
 226         return 0;
 227     /*
 228      * Only read accesses to the arena take place in sh_allocated() and this
 229      * is only changed by the sh_init() and sh_done() calls which are not
 230      * locked.  Hence, it is safe to make this check without a lock too.
 231      */
 232     return sh_allocated(ptr);
 233 #else
 234     return 0;
 235 #endif /* OPENSSL_NO_SECURE_MEMORY */
 236 }
 237
 238 size_t CRYPTO_secure_used(void)
 239 {
 240 #ifndef OPENSSL_NO_SECURE_MEMORY
 241     return secure_mem_used;
 242 #else
 243     return 0;
 244 #endif /* OPENSSL_NO_SECURE_MEMORY */
 245 }
 246
 247 size_t CRYPTO_secure_actual_size(void *ptr)
 248 {
 249 #ifndef OPENSSL_NO_SECURE_MEMORY
 250     size_t actual_size;
 251
 252     if (!CRYPTO_THREAD_write_lock(sec_malloc_lock))
 253         return 0;
 254     actual_size = sh_actual_size(ptr);
 255     CRYPTO_THREAD_unlock(sec_malloc_lock);
 256     return actual_size;
 257 #else
 258     return 0;
 259 #endif
 260 }
 261
 262 /*
 263  * SECURE HEAP IMPLEMENTATION
 264  */
 265 #ifndef OPENSSL_NO_SECURE_MEMORY
 266
 267
 268 /*
 269  * The implementation provided here uses a fixed-sized mmap() heap,
 270  * which is locked into memory, not written to core files, and protected
 271  * on either side by an unmapped page, which will catch pointer overruns
 272  * (or underruns) and an attempt to read data out of the secure heap.
 273  * Free'd memory is zero'd or otherwise cleansed.
 274  *
 275  * This is a pretty standard buddy allocator.  We keep areas in a multiple
 276  * of "sh.minsize" units.  The freelist and bitmaps are kept separately,
 277  * so all (and only) data is kept in the mmap'd heap.
 278  *
 279  * This code assumes eight-bit bytes.  The numbers 3 and 7 are all over the
 280  * place.
 281  */
 282
 283 #define ONE ((size_t)1)
 284
 285 # define TESTBIT(t, b)  (t[(b) >> 3] &  (ONE << ((b) & 7)))
 286 # define SETBIT(t, b)   (t[(b) >> 3] |= (ONE << ((b) & 7)))
 287 # define CLEARBIT(t, b) (t[(b) >> 3] &= (0xFF & ~(ONE << ((b) & 7))))
 288
 289 #define WITHIN_ARENA(p) \
 290     ((char*)(p) >= sh.arena && (char*)(p) < &sh.arena[sh.arena_size])
 291 #define WITHIN_FREELIST(p) \
 292     ((char*)(p) >= (char*)sh.freelist && (char*)(p) < (char*)&sh.freelist[sh.freelist_size])
 293
 294
 295 typedef struct sh_list_st
 296 {
 297     struct sh_list_st *next;
 298     struct sh_list_st **p_next;
 299 } SH_LIST;
 300
 301 typedef struct sh_st
 302 {
 303     char* map_result;
 304     size_t map_size;
 305     char *arena;
 306     size_t arena_size;
 307     char **freelist;
 308     ossl_ssize_t freelist_size;
 309     size_t minsize;
 310     unsigned char *bittable;
 311     unsigned char *bitmalloc;
 312     size_t bittable_size; /* size in bits */
 313 } SH;
 314
 315 static SH sh;
 316
 317 static size_t sh_getlist(char *ptr)
 318 {
 319     ossl_ssize_t list = sh.freelist_size - 1;
 320     size_t bit = (sh.arena_size + ptr - sh.arena) / sh.minsize;
 321
 322     for (; bit; bit >>= 1, list--) {
 323         if (TESTBIT(sh.bittable, bit))
 324             break;
 325         OPENSSL_assert((bit & 1) == 0);
 326     }
 327
 328     return list;
 329 }
 330
 331
 332 static int sh_testbit(char *ptr, int list, unsigned char *table)
 333 {
 334     size_t bit;
 335
 336     OPENSSL_assert(list >= 0 && list < sh.freelist_size);
 337     OPENSSL_assert(((ptr - sh.arena) & ((sh.arena_size >> list) - 1)) == 0);
 338     bit = (ONE << list) + ((ptr - sh.arena) / (sh.arena_size >> list));
 339     OPENSSL_assert(bit > 0 && bit < sh.bittable_size);
 340     return TESTBIT(table, bit);
 341 }
 342
 343 static void sh_clearbit(char *ptr, int list, unsigned char *table)
 344 {
 345     size_t bit;
 346
 347     OPENSSL_assert(list >= 0 && list < sh.freelist_size);
 348     OPENSSL_assert(((ptr - sh.arena) & ((sh.arena_size >> list) - 1)) == 0);
 349     bit = (ONE << list) + ((ptr - sh.arena) / (sh.arena_size >> list));
 350     OPENSSL_assert(bit > 0 && bit < sh.bittable_size);
 351     OPENSSL_assert(TESTBIT(table, bit));
 352     CLEARBIT(table, bit);
 353 }
 354
 355 static void sh_setbit(char *ptr, int list, unsigned char *table)
 356 {
 357     size_t bit;
 358
 359     OPENSSL_assert(list >= 0 && list < sh.freelist_size);
 360     OPENSSL_assert(((ptr - sh.arena) & ((sh.arena_size >> list) - 1)) == 0);
 361     bit = (ONE << list) + ((ptr - sh.arena) / (sh.arena_size >> list));
 362     OPENSSL_assert(bit > 0 && bit < sh.bittable_size);
 363     OPENSSL_assert(!TESTBIT(table, bit));
 364     SETBIT(table, bit);
 365 }
 366
 367 static void sh_add_to_list(char **list, char *ptr)
 368 {
 369     SH_LIST *temp;
 370
 371     OPENSSL_assert(WITHIN_FREELIST(list));
 372     OPENSSL_assert(WITHIN_ARENA(ptr));
 373
 374     temp = (SH_LIST *)ptr;
 375     temp->next = *(SH_LIST **)list;
 376     OPENSSL_assert(temp->next == NULL || WITHIN_ARENA(temp->next));
 377     temp->p_next = (SH_LIST **)list;
 378
 379     if (temp->next != NULL) {
 380         OPENSSL_assert((char **)temp->next->p_next == list);
 381         temp->next->p_next = &(temp->next);
 382     }
 383
 384     *list = ptr;
 385 }
 386
 387 static void sh_remove_from_list(char *ptr)
 388 {
 389     SH_LIST *temp, *temp2;
 390
 391     temp = (SH_LIST *)ptr;
 392     if (temp->next != NULL)
 393         temp->next->p_next = temp->p_next;
 394     *temp->p_next = temp->next;
 395     if (temp->next == NULL)
 396         return;
 397
 398     temp2 = temp->next;
 399     OPENSSL_assert(WITHIN_FREELIST(temp2->p_next) || WITHIN_ARENA(temp2->p_next));
 400 }
 401
 402
 403 static int sh_init(size_t size, size_t minsize)
 404 {
 405     int ret;
 406     size_t i;
 407     size_t pgsize;
 408     size_t aligned;
 409 #if defined(_WIN32)
 410     DWORD flOldProtect;
 411     SYSTEM_INFO systemInfo;
 412 #endif
 413
 414     memset(&sh, 0, sizeof(sh));
 415
 416     /* make sure size is a powers of 2 */
 417     OPENSSL_assert(size > 0);
 418     OPENSSL_assert((size & (size - 1)) == 0);
 419     if (size == 0 || (size & (size - 1)) != 0)
 420         goto err;
 421
 422     if (minsize <= sizeof(SH_LIST)) {
 423         OPENSSL_assert(sizeof(SH_LIST) <= 65536);
 424         /*
 425          * Compute the minimum possible allocation size.
 426          * This must be a power of 2 and at least as large as the SH_LIST
 427          * structure.
 428          */
 429         minsize = sizeof(SH_LIST) - 1;
 430         minsize |= minsize >> 1;
 431         minsize |= minsize >> 2;
 432         if (sizeof(SH_LIST) > 16)
 433             minsize |= minsize >> 4;
 434         if (sizeof(SH_LIST) > 256)
 435             minsize |= minsize >> 8;
 436         minsize++;
 437     } else {
 438         /* make sure minsize is a powers of 2 */
 439           OPENSSL_assert((minsize & (minsize - 1)) == 0);
 440           if ((minsize & (minsize - 1)) != 0)
 441               goto err;
 442     }
 443
 444     sh.arena_size = size;
 445     sh.minsize = minsize;
 446     sh.bittable_size = (sh.arena_size / sh.minsize) * 2;
 447
 448     /* Prevent allocations of size 0 later on */
 449     if (sh.bittable_size >> 3 == 0)
 450         goto err;
 451
 452     sh.freelist_size = -1;
 453     for (i = sh.bittable_size; i; i >>= 1)
 454         sh.freelist_size++;
 455
 456     sh.freelist = OPENSSL_zalloc(sh.freelist_size * sizeof(char *));
 457     OPENSSL_assert(sh.freelist != NULL);
 458     if (sh.freelist == NULL)
 459         goto err;
 460
 461     sh.bittable = OPENSSL_zalloc(sh.bittable_size >> 3);
 462     OPENSSL_assert(sh.bittable != NULL);
 463     if (sh.bittable == NULL)
 464         goto err;
 465
 466     sh.bitmalloc = OPENSSL_zalloc(sh.bittable_size >> 3);
 467     OPENSSL_assert(sh.bitmalloc != NULL);
 468     if (sh.bitmalloc == NULL)
 469         goto err;
 470
 471     /* Allocate space for heap, and two extra pages as guards */
 472 #if defined(_SC_PAGE_SIZE) || defined (_SC_PAGESIZE)
 473     {
 474 # if defined(_SC_PAGE_SIZE)
 475         long tmppgsize = sysconf(_SC_PAGE_SIZE);
 476 # else
 477         long tmppgsize = sysconf(_SC_PAGESIZE);
 478 # endif
 479         if (tmppgsize < 1)
 480             pgsize = PAGE_SIZE;
 481         else
 482             pgsize = (size_t)tmppgsize;
 483     }
 484 #elif defined(_WIN32)
 485     GetSystemInfo(&systemInfo);
 486     pgsize = (size_t)systemInfo.dwPageSize;
 487 #else
 488     pgsize = PAGE_SIZE;
 489 #endif
 490     sh.map_size = pgsize + sh.arena_size + pgsize;
 491
 492 #if !defined(_WIN32)
 493 # ifdef MAP_ANON
 494     sh.map_result = mmap(NULL, sh.map_size,
 495                          PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE|MAP_CONCEAL, -1, 0);
 496 # else
 497     {
 498         int fd;
 499
 500         sh.map_result = MAP_FAILED;
 501         if ((fd = open("/dev/zero", O_RDWR)) >= 0) {
 502             sh.map_result = mmap(NULL, sh.map_size,
 503                                  PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
 504             close(fd);
 505         }
 506     }
 507 # endif
 508     if (sh.map_result == MAP_FAILED)
 509         goto err;
 510 #else
 511     sh.map_result = VirtualAlloc(NULL, sh.map_size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
 512
 513     if (sh.map_result == NULL)
 514             goto err;
 515 #endif
 516
 517     sh.arena = (char *)(sh.map_result + pgsize);
 518     sh_setbit(sh.arena, 0, sh.bittable);
 519     sh_add_to_list(&sh.freelist[0], sh.arena);
 520
 521     /* Now try to add guard pages and lock into memory. */
 522     ret = 1;
 523
 524 #if !defined(_WIN32)
 525     /* Starting guard is already aligned from mmap. */
 526     if (mprotect(sh.map_result, pgsize, PROT_NONE) < 0)
 527         ret = 2;
 528 #else
 529     if (VirtualProtect(sh.map_result, pgsize, PAGE_NOACCESS, &flOldProtect) == FALSE)
 530         ret = 2;
 531 #endif
 532
 533     /* Ending guard page - need to round up to page boundary */
 534     aligned = (pgsize + sh.arena_size + (pgsize - 1)) & ~(pgsize - 1);
 535 #if !defined(_WIN32)
 536     if (mprotect(sh.map_result + aligned, pgsize, PROT_NONE) < 0)
 537         ret = 2;
 538 #else
 539     if (VirtualProtect(sh.map_result + aligned, pgsize, PAGE_NOACCESS, &flOldProtect) == FALSE)
 540         ret = 2;
 541 #endif
 542
 543 #if defined(OPENSSL_SYS_LINUX) && defined(MLOCK_ONFAULT) && defined(SYS_mlock2)
 544     if (syscall(SYS_mlock2, sh.arena, sh.arena_size, MLOCK_ONFAULT) < 0) {
 545         if (errno == ENOSYS) {
 546             if (mlock(sh.arena, sh.arena_size) < 0)
 547                 ret = 2;
 548         } else {
 549             ret = 2;
 550         }
 551     }
 552 #elif defined(_WIN32)
 553     if (VirtualLock(sh.arena, sh.arena_size) == FALSE)
 554         ret = 2;
 555 #else
 556     if (mlock(sh.arena, sh.arena_size) < 0)
 557         ret = 2;
 558 #endif
 559 #ifdef MADV_DONTDUMP
 560     if (madvise(sh.arena, sh.arena_size, MADV_DONTDUMP) < 0)
 561         ret = 2;
 562 #endif
 563
 564     return ret;
 565
 566  err:
 567     sh_done();
 568     return 0;
 569 }
 570
 571 static void sh_done(void)
 572 {
 573     OPENSSL_free(sh.freelist);
 574     OPENSSL_free(sh.bittable);
 575     OPENSSL_free(sh.bitmalloc);
 576 #if !defined(_WIN32)
 577     if (sh.map_result != MAP_FAILED && sh.map_size)
 578         munmap(sh.map_result, sh.map_size);
 579 #else
 580     if (sh.map_result != NULL && sh.map_size)
 581         VirtualFree(sh.map_result, 0, MEM_RELEASE);
 582 #endif
 583     memset(&sh, 0, sizeof(sh));
 584 }
 585
 586 static int sh_allocated(const char *ptr)
 587 {
 588     return WITHIN_ARENA(ptr) ? 1 : 0;
 589 }
 590
 591 static char *sh_find_my_buddy(char *ptr, int list)
 592 {
 593     size_t bit;
 594     char *chunk = NULL;
 595
 596     bit = (ONE << list) + (ptr - sh.arena) / (sh.arena_size >> list);
 597     bit ^= 1;
 598
 599     if (TESTBIT(sh.bittable, bit) && !TESTBIT(sh.bitmalloc, bit))
 600         chunk = sh.arena + ((bit & ((ONE << list) - 1)) * (sh.arena_size >> list));
 601
 602     return chunk;
 603 }
 604
 605 static void *sh_malloc(size_t size)
 606 {
 607     ossl_ssize_t list, slist;
 608     size_t i;
 609     char *chunk;
 610
 611     if (size > sh.arena_size)
 612         return NULL;
 613
 614     list = sh.freelist_size - 1;
 615     for (i = sh.minsize; i < size; i <<= 1)
 616         list--;
 617     if (list < 0)
 618         return NULL;
 619
 620     /* try to find a larger entry to split */
 621     for (slist = list; slist >= 0; slist--)
 622         if (sh.freelist[slist] != NULL)
 623             break;
 624     if (slist < 0)
 625         return NULL;
 626
 627     /* split larger entry */
 628     while (slist != list) {
 629         char *temp = sh.freelist[slist];
 630
 631         /* remove from bigger list */
 632         OPENSSL_assert(!sh_testbit(temp, slist, sh.bitmalloc));
 633         sh_clearbit(temp, slist, sh.bittable);
 634         sh_remove_from_list(temp);
 635         OPENSSL_assert(temp != sh.freelist[slist]);
 636
 637         /* done with bigger list */
 638         slist++;
 639
 640         /* add to smaller list */
 641         OPENSSL_assert(!sh_testbit(temp, slist, sh.bitmalloc));
 642         sh_setbit(temp, slist, sh.bittable);
 643         sh_add_to_list(&sh.freelist[slist], temp);
 644         OPENSSL_assert(sh.freelist[slist] == temp);
 645
 646         /* split in 2 */
 647         temp += sh.arena_size >> slist;
 648         OPENSSL_assert(!sh_testbit(temp, slist, sh.bitmalloc));
 649         sh_setbit(temp, slist, sh.bittable);
 650         sh_add_to_list(&sh.freelist[slist], temp);
 651         OPENSSL_assert(sh.freelist[slist] == temp);
 652
 653         OPENSSL_assert(temp-(sh.arena_size >> slist) == sh_find_my_buddy(temp, slist));
 654     }
 655
 656     /* peel off memory to hand back */
 657     chunk = sh.freelist[list];
 658     OPENSSL_assert(sh_testbit(chunk, list, sh.bittable));
 659     sh_setbit(chunk, list, sh.bitmalloc);
 660     sh_remove_from_list(chunk);
 661
 662     OPENSSL_assert(WITHIN_ARENA(chunk));
 663
 664     /* zero the free list header as a precaution against information leakage */
 665     memset(chunk, 0, sizeof(SH_LIST));
 666
 667     return chunk;
 668 }
 669
 670 static void sh_free(void *ptr)
 671 {
 672     size_t list;
 673     void *buddy;
 674
 675     if (ptr == NULL)
 676         return;
 677     OPENSSL_assert(WITHIN_ARENA(ptr));
 678     if (!WITHIN_ARENA(ptr))
 679         return;
 680
 681     list = sh_getlist(ptr);
 682     OPENSSL_assert(sh_testbit(ptr, list, sh.bittable));
 683     sh_clearbit(ptr, list, sh.bitmalloc);
 684     sh_add_to_list(&sh.freelist[list], ptr);
 685
 686     /* Try to coalesce two adjacent free areas. */
 687     while ((buddy = sh_find_my_buddy(ptr, list)) != NULL) {
 688         OPENSSL_assert(ptr == sh_find_my_buddy(buddy, list));
 689         OPENSSL_assert(ptr != NULL);
 690         OPENSSL_assert(!sh_testbit(ptr, list, sh.bitmalloc));
 691         sh_clearbit(ptr, list, sh.bittable);
 692         sh_remove_from_list(ptr);
 693         OPENSSL_assert(!sh_testbit(ptr, list, sh.bitmalloc));
 694         sh_clearbit(buddy, list, sh.bittable);
 695         sh_remove_from_list(buddy);
 696
 697         list--;
 698
 699         /* Zero the higher addressed block's free list pointers */
 700         memset(ptr > buddy ? ptr : buddy, 0, sizeof(SH_LIST));
 701         if (ptr > buddy)
 702             ptr = buddy;
 703
 704         OPENSSL_assert(!sh_testbit(ptr, list, sh.bitmalloc));
 705         sh_setbit(ptr, list, sh.bittable);
 706         sh_add_to_list(&sh.freelist[list], ptr);
 707         OPENSSL_assert(sh.freelist[list] == ptr);
 708     }
 709 }
 710
 711 static size_t sh_actual_size(char *ptr)
 712 {
 713     int list;
 714
 715     OPENSSL_assert(WITHIN_ARENA(ptr));
 716     if (!WITHIN_ARENA(ptr))
 717         return 0;
 718     list = sh_getlist(ptr);
 719     OPENSSL_assert(sh_testbit(ptr, list, sh.bittable));
 720     return sh.arena_size / (ONE << list);
 721 }
 722 #endif /* OPENSSL_NO_SECURE_MEMORY */