usr.bin/crunch/crunchide/exec_elf32.c

   1 /* $NetBSD: exec_elf32.c,v 1.13 2003/07/26 20:34:12 salo Exp $ */
   2
   3 /*
   4  * Copyright (c) 1997, 1998 Christopher G. Demetriou
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *          This product includes software developed for the
  18  *          NetBSD Project.  See http://www.NetBSD.org/ for
  19  *          information about NetBSD.
  20  * 4. The name of the author may not be used to endorse or promote products
  21  *    derived from this software without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  33  *
  34  * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
  35  */
  36
  37 #include <sys/cdefs.h>
  38 #ifndef lint
  39 __RCSID("$NetBSD: exec_elf32.c,v 1.13 2003/07/26 20:34:12 salo Exp $");
  40 #endif
  41
  42 #ifndef ELFSIZE
  43 #define ELFSIZE         32
  44 #endif
  45
  46 #include <sys/types.h>
  47 #include <sys/stat.h>
  48
  49 #include <errno.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <string.h>
  53 #include <unistd.h>
  54
  55 #include "extern.h"
  56
  57 #if (defined(NLIST_ELF32) && (ELFSIZE == 32)) || \
  58     (defined(NLIST_ELF64) && (ELFSIZE == 64))
  59
  60 #include <sys/exec_elf.h>
  61
  62 struct listelem {
  63         struct listelem *next;
  64         void *mem;
  65         off_t file;
  66         size_t size;
  67 };
  68
  69 static ssize_t
  70 xreadatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
  71 {
  72         ssize_t rv;
  73
  74         if (lseek(fd, off, SEEK_SET) != off) {
  75                 perror(fn);
  76                 return -1;
  77         }
  78         if ((size_t)(rv = read(fd, buf, size)) != size) {
  79                 fprintf(stderr, "%s: read error: %s\n", fn,
  80                     rv == -1 ? strerror(errno) : "short read");
  81                 return -1;
  82         }
  83         return size;
  84 }
  85
  86 static ssize_t
  87 xwriteatoff(int fd, void *buf, off_t off, size_t size, const char *fn)
  88 {
  89         ssize_t rv;
  90
  91         if (lseek(fd, off, SEEK_SET) != off) {
  92                 perror(fn);
  93                 return -1;
  94         }
  95         if ((size_t)(rv = write(fd, buf, size)) != size) {
  96                 fprintf(stderr, "%s: write error: %s\n", fn,
  97                     rv == -1 ? strerror(errno) : "short write");
  98                 return -1;
  99         }
 100         return size;
 101 }
 102
 103 static void *
 104 xmalloc(size_t size, const char *fn, const char *use)
 105 {
 106         void *rv;
 107
 108         rv = malloc(size);
 109         if (rv == NULL)
 110                 fprintf(stderr, "%s: out of memory (allocating for %s)\n",
 111                     fn, use);
 112         return (rv);
 113 }
 114
 115 static void *
 116 xrealloc(void *ptr, size_t size, const char *fn, const char *use)
 117 {
 118         void *rv;
 119
 120         rv = realloc(ptr, size);
 121         if (rv == NULL) {
 122                 free(ptr);
 123                 fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
 124                     fn, use);
 125         }
 126         return (rv);
 127 }
 128
 129 int
 130 ELFNAMEEND(check)(int fd, const char *fn)
 131 {
 132         Elf_Ehdr eh;
 133         struct stat sb;
 134
 135         /*
 136          * Check the header to maek sure it's an ELF file (of the
 137          * appropriate size).
 138          */
 139         if (fstat(fd, &sb) == -1)
 140                 return 0;
 141         if (sb.st_size < (off_t)(sizeof eh))
 142                 return 0;
 143         if (read(fd, &eh, sizeof eh) != sizeof eh)
 144                 return 0;
 145
 146         if (memcmp(eh.e_ident, ELFMAG, SELFMAG) != 0 ||
 147             eh.e_ident[EI_CLASS] != ELFCLASS)
 148                 return 0;
 149
 150         switch (eh.e_machine) {
 151         ELFDEFNNAME(MACHDEP_ID_CASES)
 152
 153         default:
 154                 return 0;
 155         }
 156
 157         return 1;
 158 }
 159
 160 /*
 161  * This function 'hides' (some of) ELF executable file's symbols.
 162  * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
 163  * Symbols in the global keep list, or which are marked as being undefined,
 164  * are left alone.
 165  *
 166  * An old version of this code shuffled various tables around, turning
 167  * global symbols to be hidden into local symbols.  That lost on the
 168  * mips, because CALL16 relocs must reference global symbols, and, if
 169  * those symbols were being hidden, they were no longer global.
 170  *
 171  * The new renaming behaviour doesn't take global symbols out of the
 172  * namespace.  However, it's ... unlikely that there will ever be
 173  * any collisions in practice because of the new method.
 174  */
 175 int
 176 ELFNAMEEND(hide)(int fd, const char *fn)
 177 {
 178         Elf_Ehdr ehdr;
 179         Elf_Shdr *shdrp = NULL;
 180         int symtabsnum, strtabsnum;
 181         Elf_Sym *symtabp = NULL;
 182         char *strtabp = NULL, *nstrtabp = NULL;
 183         Elf_Word j, nsyms;
 184         Elf_Off stroff, maxoff;
 185         const char *weirdreason;
 186         ssize_t shdrsize;
 187         size_t nstrtab_size, nstrtab_nextoff, fn_size;
 188         int rv, i, weird;
 189
 190         rv = 0;
 191         if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
 192                 goto bad;
 193
 194         shdrsize = ehdr.e_shnum * ehdr.e_shentsize;
 195         if ((shdrp = xmalloc(shdrsize, fn, "section header table")) == NULL)
 196                 goto bad;
 197         if (xreadatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
 198                 goto bad;
 199
 200         symtabsnum = strtabsnum = -1;
 201         maxoff = stroff = 0;
 202         weird = 0;
 203         weirdreason = "???";
 204         for (i = 0; i < ehdr.e_shnum; i++) {
 205                 if (shdrp[i].sh_offset > maxoff) {
 206                         maxoff = shdrp[i].sh_offset;
 207                 }
 208                 switch (shdrp[i].sh_type) {
 209                 case SHT_SYMTAB:
 210                         if (!weird && symtabsnum != -1) {
 211                                 weird = 1;
 212                                 weirdreason = "multiple symbol tables";
 213                         }
 214                         symtabsnum = i;
 215                         strtabsnum = shdrp[i].sh_link;
 216                         stroff = shdrp[strtabsnum].sh_offset;
 217                         if (!weird && strtabsnum != (ehdr.e_shnum - 1)) {
 218                                 weird = 1;
 219                                 weirdreason = "string table not last section";
 220                         }
 221                         break;
 222                 }
 223         }
 224         if (symtabsnum == -1)
 225                 goto out;
 226         if (!weird && strtabsnum == -1) {
 227                 weird = 1;
 228                 weirdreason = "no string table found";
 229         }
 230         if (!weird && stroff != maxoff) {
 231                 weird = 1;
 232                 weirdreason = "string table section not last in file";
 233         }
 234         if (weird) {
 235                 fprintf(stderr, "%s: weird executable (%s); unsupported\n", fn,
 236                     weirdreason);
 237                 goto bad;
 238         }
 239
 240         /*
 241          * load up everything we need
 242          */
 243
 244         /* symbol table */
 245         if ((symtabp = xmalloc(shdrp[symtabsnum].sh_size, fn, "symbol table"))
 246             == NULL)
 247                 goto bad;
 248         if ((size_t)xreadatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
 249             shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
 250                 goto bad;
 251
 252         /* string table */
 253         if ((strtabp = xmalloc(shdrp[strtabsnum].sh_size, fn, "string table"))
 254             == NULL)
 255                 goto bad;
 256         if ((size_t)xreadatoff(fd, strtabp, shdrp[strtabsnum].sh_offset,
 257             shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
 258                 goto bad;
 259
 260         nsyms = shdrp[symtabsnum].sh_size / shdrp[symtabsnum].sh_entsize;
 261
 262         nstrtab_size = 256;
 263         nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
 264         if (nstrtabp == NULL)
 265                 goto bad;
 266         nstrtab_nextoff = 0;
 267
 268         fn_size = strlen(fn);
 269
 270         for (j = 0; j < nsyms; j++) {
 271                 Elf_Sym *sp = &symtabp[j];
 272                 const char *symname = strtabp + sp->st_name;
 273                 size_t newent_len;
 274
 275                 /*
 276                  * make sure there's size for the next entry, even if it's
 277                  * as large as it can be.
 278                  *
 279                  * "_$$hide$$ <filename> <symname><NUL>" ->
 280                  *    9 + 3 + sizes of fn and sym name
 281                  */
 282                 while ((nstrtab_size - nstrtab_nextoff) <
 283                     strlen(symname) + fn_size + 12) {
 284                         nstrtab_size *= 2;
 285                         nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
 286                             "new string table");
 287                         if (nstrtabp == NULL)
 288                                 goto bad;
 289                 }
 290
 291                 sp->st_name = nstrtab_nextoff;
 292
 293                 /* if it's a keeper or is undefined, don't rename it. */
 294                 if (in_keep_list(symname) ||
 295                     sp->st_shndx == SHN_UNDEF) {
 296                         newent_len = sprintf(nstrtabp + nstrtab_nextoff,
 297                             "%s", symname) + 1;
 298                 } else {
 299                         newent_len = sprintf(nstrtabp + nstrtab_nextoff,
 300                             "_$$hide$$ %s %s", fn, symname) + 1;
 301                 }
 302                 nstrtab_nextoff += newent_len;
 303         }
 304         shdrp[strtabsnum].sh_size = nstrtab_nextoff;
 305
 306         /*
 307          * write new tables to the file
 308          */
 309         if (xwriteatoff(fd, shdrp, ehdr.e_shoff, shdrsize, fn) != shdrsize)
 310                 goto bad;
 311         if ((size_t)xwriteatoff(fd, symtabp, shdrp[symtabsnum].sh_offset,
 312             shdrp[symtabsnum].sh_size, fn) != shdrp[symtabsnum].sh_size)
 313                 goto bad;
 314         if ((size_t)xwriteatoff(fd, nstrtabp, shdrp[strtabsnum].sh_offset,
 315             shdrp[strtabsnum].sh_size, fn) != shdrp[strtabsnum].sh_size)
 316                 goto bad;
 317
 318 out:
 319         if (shdrp != NULL)
 320                 free(shdrp);
 321         if (symtabp != NULL)
 322                 free(symtabp);
 323         if (strtabp != NULL)
 324                 free(strtabp);
 325         if (nstrtabp != NULL)
 326                 free(nstrtabp);
 327         return (rv);
 328
 329 bad:
 330         rv = 1;
 331         goto out;
 332 }
 333
 334 #endif /* include this size of ELF */