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   1 /* -*-c-*-
   2  *
   3  * $Id: lmem.c,v 1.2 2000/06/17 11:29:20 mdw Exp $
   4  *
   5  * Locked memory allocation (Unix-specific)
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: lmem.c,v $
  33  * Revision 1.2  2000/06/17 11:29:20  mdw
  34  * Add arena support.
  35  *
  36  * Revision 1.1  1999/12/22 16:02:52  mdw
  37  * Interface to allocating `locked' memory (which isn't paged out).
  38  *
  39  */
  40
  41 /*----- Header files ------------------------------------------------------*/
  42
  43 #include "config.h"
  44
  45 #include <assert.h>
  46 #include <errno.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50
  51 #include <sys/types.h>
  52 #include <unistd.h>
  53
  54 #ifdef HAVE_MLOCK
  55 #  include <sys/mman.h>
  56 #endif
  57
  58 #include <mLib/arena.h>
  59 #include <mLib/dstr.h>
  60 #include <mLib/sub.h>
  61
  62 #include "lmem.h"
  63
  64 /*----- Arena operations --------------------------------------------------*/
  65
  66 static void *aalloc(arena *a, size_t sz) { return l_alloc((lmem *)a, sz); }
  67 static void afree(arena *a, void *p) { l_free((lmem *)a, p); }
  68 static void apurge(arena *a) { l_purge((lmem *)a); }
  69
  70 static arena_ops l_ops = { aalloc, arena_fakerealloc, afree, apurge };
  71
  72 /*----- Main code ---------------------------------------------------------*/
  73
  74 /* --- @l_init@ --- *
  75  *
  76  * Arguments:   @lmem *lm@ = pointer to locked memory descriptor
  77  *              @size_t sz@ = size of locked memory area requested
  78  *
  79  * Returns:     Zero if everything is fine, @+1@ if some insecure memory was
  80  *              allocated, and @-1@ if everything went horribly wrong.
  81  *
  82  * Use:         Initializes the locked memory manager.  This function is safe
  83  *              to call in a privileged program; privileges should usually be
  84  *              dropped after allocating the locked memory block.
  85  *
  86  *              You must call @sub_init@ before allocating locked memory
  87  *              buffers.
  88  */
  89
  90 int l_init(lmem *lm, size_t sz)
  91 {
  92   char *p;
  93   int rc = 0;
  94   l_node *l;
  95
  96   /* --- Preliminaries --- */
  97
  98   lm->a.ops = &l_ops;
  99   lm->err = 0;
 100
 101   /* --- Try making a secure locked passphrase buffer --- *
 102    *
 103    * Drop privileges before emitting diagnostic messages.
 104    */
 105
 106 #ifdef HAVE_MLOCK
 107
 108   /* --- Memory-map a page from somewhere --- */
 109
 110 #  ifdef MAP_ANON
 111   p = mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
 112 #  else
 113   {
 114     int fd;
 115     if ((fd = open("/dev/zero", O_RDWR)) >= 0) {
 116       p = mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 117       close(fd);
 118     }
 119   }
 120 #  endif
 121
 122   /* --- Lock the page in memory --- *
 123    *
 124    * Why does @mmap@ return such a stupid result if it fails?
 125    */
 126
 127   if (p == 0 || p == MAP_FAILED) {
 128     lm->emsg = "couldn't map locked memory area: %s";
 129     lm->err = errno;
 130     p = 0;
 131   } else if (mlock(p, sz)) {
 132     lm->emsg = "error locking memory area: %s";
 133     lm->err = errno;
 134     munmap(p, sz);
 135     p = 0;
 136   }
 137
 138 #endif
 139
 140   /* --- Make a standard passphrase buffer --- */
 141
 142 #ifdef HAVE_MLOCK
 143   if (!p)
 144 #else
 145   ll->err = 0;
 146   ll->emsg = "locked memory not available on this system";
 147 #endif
 148   {
 149     if ((p = malloc(sz)) == 0) {
 150       lm->emsg = "not enough standard memory!";
 151       lm->err = ENOMEM;
 152       return (-1);
 153     }
 154     rc = +1;
 155   }
 156
 157   /* --- Initialize the buffer --- */
 158
 159   lm->sz = lm->free = sz;
 160   lm->p = p;
 161
 162   /* --- Initialize the free list --- */
 163
 164   l = CREATE(l_node);
 165   l->next = 0;
 166   l->p = p;
 167   l->sz = sz;
 168   l->f = 0;
 169   lm->l = l;
 170
 171   /* --- Done --- */
 172
 173   return (rc);
 174 }
 175
 176 /* --- @l_alloc@ --- *
 177  *
 178  * Arguments:   @lmem *lm@ = pointer to locked memory descriptor
 179  *              @size_t sz@ = size requested
 180  *
 181  * Returns:     Pointer to allocated memory.
 182  *
 183  * Use:         Allocates @sz@ bytes of locked memory.
 184  */
 185
 186 void *l_alloc(lmem *lm, size_t sz)
 187 {
 188   l_node *l;
 189
 190   sz = (sz + 3u) & ~3u;
 191   for (l = lm->l; l; l = l->next) {
 192     if (l->f & LF_ALLOC)
 193       continue;
 194     if (l->sz < sz)
 195       continue;
 196     l->f |= LF_ALLOC;
 197     if (l->sz > sz) {
 198       l_node *n = CREATE(l_node);
 199       n->next = l->next;
 200       n->p = l->p + sz;
 201       n->sz = l->sz - sz;
 202       l->sz = sz;
 203       n->f = 0;
 204       l->next = n;
 205     }
 206     assert(((void)"Locked buffer space has vanished", lm->free >= sz));
 207     lm->free -= sz;
 208     return (l->p);
 209   }
 210   return (0);
 211 }
 212
 213 /* --- @l_free@ --- *
 214  *
 215  * Arguments:   @lmem *lm@ = pointer to locked memory descriptor
 216  *              @void *p@ = pointer to block
 217  *
 218  * Returns:     ---
 219  *
 220  * Use:         Releases a block of locked memory.
 221  */
 222
 223 void l_free(lmem *lm, void *p)
 224 {
 225   l_node *l;
 226   l_node *ll = 0;
 227
 228   for (l = lm->l; l; l = l->next) {
 229     size_t sz;
 230
 231     /* --- If this isn't the block, skip it --- */
 232
 233     if (l->p != p) {
 234       ll = l;
 235       continue;
 236     }
 237     assert(((void)"Block is already free", l->f & LF_ALLOC));
 238
 239     /* --- Coalesce with adjacent free blocks --- */
 240
 241     l->f &= ~LF_ALLOC;
 242     sz = l->sz;
 243     memset(p, 0, sz);
 244
 245     if (ll && !(ll->f & LF_ALLOC)) {
 246       assert(((void)"Previous block doesn't fit", ll->p + ll->sz == p));
 247       ll->sz += sz;
 248       ll->next = l->next;
 249       DESTROY(l);
 250       l = ll;
 251     }
 252
 253     ll = l->next;
 254     if (ll && !(ll->f & LF_ALLOC)) {
 255       assert(((void)"Next block doesn't fit", ll->p == l->p + l->sz));
 256       l->sz += ll->sz;
 257       l->next = ll->next;
 258       DESTROY(ll);
 259     }
 260
 261     lm->free += sz;
 262     assert(((void)"Free lunch", lm->free <= lm->sz));
 263     return;
 264   }
 265   assert(((void)"Not a locked block", 0));
 266 }
 267
 268 /* --- @l_purge@ --- *
 269  *
 270  * Arguments:   @lmem *lm@ = pointer to locked memory descriptor
 271  *
 272  * Returns:     ---
 273  *
 274  * Use:         Purges all the free blocks in the buffer, and clears all of
 275  *              the locked memory.  Memory is not freed back to the system.
 276  */
 277
 278 void l_purge(lmem *lm)
 279 {
 280   l_node *l;
 281
 282   l = lm->l;
 283   while (l) {
 284     l_node *ll = l->next;
 285     DESTROY(l);
 286     l = ll;
 287   }
 288   memset(lm->p, 0, lm->sz);
 289   l = CREATE(l_node);
 290   l->next = 0;
 291   l->p = lm->p;
 292   l->sz = lm->sz;
 293   l->f = 0;
 294   lm->l = l;
 295   lm->free = l->sz;
 296 }
 297
 298 /* --- @l_report@ --- *
 299  *
 300  * Arguments:   @lmem *lm@ = pointer to locked memory descriptor
 301  *              @dstr *d@ = string to write the error message on
 302  *
 303  * Returns:     Zero if the buffer is fine, @+1@ if there was a problem
 304  *              getting locked memory but insecure stuff could be allocated,
 305  *              and @-1@ if not even insecure memory could be found.
 306  *
 307  * Use:         Returns a user-digestable explanation for the state of a
 308  *              locked memory buffer.  If the return code is zero, no message
 309  *              is emitted to the string @d@.
 310  */
 311
 312 int l_report(lmem *lm, dstr *d)
 313 {
 314   int rc;
 315   if (lm->err)
 316     dstr_putf(d, lm->emsg, strerror(lm->err));
 317   if (!lm->p)
 318     rc = -1;
 319   else if (lm->err)
 320     rc = +1;
 321   else
 322     rc = 0;
 323   return (rc);
 324 }
 325
 326 /*----- That's all, folks -------------------------------------------------*/