sbin/cryptdisks/safe_mem.c

   1 /*
   2  * Copyright (c) 2011 Alex Hornung <alex@alexhornung.com>.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in
  13  *    the documentation and/or other materials provided with the
  14  *    distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  19  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  20  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  22  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  24  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  25  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  26  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29 #include <sys/types.h>
  30 #include <sys/mman.h>
  31 #include <stdlib.h>
  32 #include <stdio.h>
  33 #include <string.h>
  34
  35 #include "safe_mem.h"
  36
  37 struct safe_mem_hdr {
  38         struct safe_mem_hdr     *prev;
  39         struct safe_mem_hdr     *next;
  40         struct safe_mem_tail    *tail;
  41         const char      *file;
  42         int             line;
  43         size_t          alloc_sz;
  44         char            sig[8]; /* SAFEMEM */
  45 };
  46
  47 struct safe_mem_tail {
  48         char sig[8]; /* SAFEMEM */
  49 };
  50
  51 static struct safe_mem_hdr *safe_mem_hdr_first = NULL;
  52
  53 #pragma weak _alloc_safe_mem
  54 void *
  55 _alloc_safe_mem(size_t req_sz, const char *file, int line)
  56 {
  57         struct safe_mem_hdr *hdr, *hdrp;
  58         struct safe_mem_tail *tail;
  59         size_t alloc_sz;
  60         char *mem, *user_mem;
  61
  62         alloc_sz = req_sz + sizeof(*hdr) + sizeof(*tail);
  63         if ((mem = malloc(alloc_sz)) == NULL)
  64                 return NULL;
  65
  66         if (mlock(mem, alloc_sz) < 0) {
  67                 free(mem);
  68                 return NULL;
  69         }
  70
  71         memset(mem, 0, alloc_sz);
  72
  73         hdr = (struct safe_mem_hdr *)mem;
  74         tail = (struct safe_mem_tail *)(mem + alloc_sz - sizeof(*tail));
  75         user_mem = mem + sizeof(*hdr);
  76
  77         strcpy(hdr->sig, "SAFEMEM");
  78         strcpy(tail->sig, "SAFEMEM");
  79         hdr->tail = tail;
  80         hdr->alloc_sz = alloc_sz;
  81         hdr->file = file;
  82         hdr->line = line;
  83         hdr->next = NULL;
  84
  85         if (safe_mem_hdr_first == NULL) {
  86                 safe_mem_hdr_first = hdr;
  87         } else {
  88                 hdrp = safe_mem_hdr_first;
  89                 while (hdrp->next != NULL)
  90                         hdrp = hdrp->next;
  91                 hdr->prev = hdrp;
  92                 hdrp->next = hdr;
  93         }
  94
  95         return user_mem;
  96 }
  97
  98 #pragma weak _free_safe_mem
  99 void
 100 _free_safe_mem(void *mem_ptr, const char *file, int line)
 101 {
 102         struct safe_mem_hdr *hdr;
 103         struct safe_mem_tail *tail;
 104         size_t alloc_sz;
 105         char *mem = mem_ptr;
 106
 107         mem -= sizeof(*hdr);
 108         hdr = (struct safe_mem_hdr *)mem;
 109         tail = (struct safe_mem_tail *)(mem + hdr->alloc_sz - sizeof(*tail));
 110
 111 #ifdef DEBUG
 112         fprintf(stderr, "freeing safe_mem (hdr): %#lx (%s:%d)\n",
 113                     (unsigned long)(void *)hdr, hdr->file, hdr->line);
 114 #endif
 115
 116         if (hdr->alloc_sz == 0) {
 117                 fprintf(stderr, "BUG: double-free at %s:%d !!!\n", file, line);
 118                 return;
 119         }
 120
 121         /* Integrity checks */
 122         if ((memcmp(hdr->sig, "SAFEMEM\0", 8) != 0) ||
 123             (memcmp(tail->sig, "SAFEMEM\0", 8) != 0)) {
 124                 fprintf(stderr, "BUG: safe_mem buffer under- or overflow at "
 125                     "%s:%d !!!\n", file, line);
 126                 return;
 127         }
 128
 129         if (safe_mem_hdr_first == NULL) {
 130                 fprintf(stderr, "BUG: safe_mem list should not be empty at "
 131                     "%s:%d !!!\n", file, line);
 132                 return;
 133         }
 134
 135         if (hdr->prev != NULL)
 136                 hdr->prev->next = hdr->next;
 137         if (hdr->next != NULL)
 138                 hdr->next->prev = hdr->prev;
 139         if (safe_mem_hdr_first == hdr)
 140                 safe_mem_hdr_first = hdr->next;
 141
 142         alloc_sz = hdr->alloc_sz;
 143         memset(mem, 0xFF, alloc_sz);
 144         memset(mem, 0, alloc_sz);
 145
 146         free(mem);
 147 }
 148
 149 #pragma weak check_and_purge_safe_mem
 150 void
 151 check_and_purge_safe_mem(void)
 152 {
 153         struct safe_mem_hdr *hdr;
 154         char *mem;
 155 #ifdef DEBUG
 156         int ok;
 157 #endif
 158
 159         if (safe_mem_hdr_first == NULL)
 160                 return;
 161
 162         hdr = safe_mem_hdr_first;
 163         while ((hdr = safe_mem_hdr_first) != NULL) {
 164 #ifdef DEBUG
 165                 if ((hdr->alloc_sz > 0) &&
 166                     (memcmp(hdr->sig, "SAFEMEM\0", 8) == 0) &&
 167                     (memcmp(hdr->tail->sig, "SAFEMEM\0", 8) == 0))
 168                         ok = 1;
 169                 else
 170                         ok = 0;
 171
 172                 fprintf(stderr, "un-freed safe_mem: %#lx (%s:%d) [integrity=%s]\n",
 173                     (unsigned long)(void *)hdr, hdr->file, hdr->line,
 174                     ok? "ok" : "failed");
 175 #endif
 176                 mem = (void *)hdr;
 177                 mem += sizeof(*hdr);
 178                 _free_safe_mem(mem, "check_and_purge_safe_mem", 0);
 179         }
 180 }