jail/elf.c

   1 /*
   2  * Copyright (C) 2015 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <sys/mman.h>
  16
  17 #include <stdlib.h>
  18 #include <unistd.h>
  19 #include <stdio.h>
  20 #include <string.h>
  21 #include <sys/stat.h>
  22 #include <fcntl.h>
  23 #include <libgen.h>
  24 #include <glob.h>
  25 #include <elf.h>
  26
  27 #include <libubox/utils.h>
  28
  29 #include "elf.h"
  30
  31 struct avl_tree libraries;
  32 static LIST_HEAD(library_paths);
  33
  34 void alloc_library_path(const char *path)
  35 {
  36         struct stat s;
  37         if (stat(path, &s))
  38                 return;
  39
  40         struct library_path *p;
  41         char *_path;
  42
  43         p = calloc_a(sizeof(*p),
  44                 &_path, strlen(path) + 1);
  45         if (!p)
  46                 return;
  47
  48         p->path = strcpy(_path, path);
  49
  50         list_add_tail(&p->list, &library_paths);
  51         DEBUG("adding ld.so path %s\n", path);
  52 }
  53
  54 static void alloc_library(const char *path, const char *name)
  55 {
  56         struct library *l;
  57         char *_name, *_path;
  58
  59         l = calloc_a(sizeof(*l),
  60                 &_path, strlen(path) + 1,
  61                 &_name, strlen(name) + 1);
  62         if (!l)
  63                 return;
  64
  65         l->avl.key = l->name = strcpy(_name, name);
  66         l->path = strcpy(_path, path);
  67
  68         avl_insert(&libraries, &l->avl);
  69         DEBUG("adding library %s/%s\n", path, name);
  70 }
  71
  72 static int elf_open(char **dir, char *file)
  73 {
  74         struct library_path *p;
  75         char path[256];
  76         int fd = -1;
  77
  78         *dir = NULL;
  79
  80         list_for_each_entry(p, &library_paths, list) {
  81                 if (strlen(p->path))
  82                         snprintf(path, sizeof(path), "%s/%s", p->path, file);
  83                 else
  84                         strncpy(path, file, sizeof(path));
  85                 fd = open(path, O_RDONLY);
  86                 if (fd >= 0) {
  87                         *dir = p->path;
  88                         break;
  89                 }
  90         }
  91
  92         if (fd == -1)
  93                 fd = open(file, O_RDONLY);
  94
  95         return fd;
  96 }
  97
  98 char* find_lib(char *file)
  99 {
 100         struct library *l;
 101         static char path[256];
 102         const char *p;
 103
 104         l = avl_find_element(&libraries, file, l, avl);
 105         if (!l)
 106                 return NULL;
 107
 108         p = l->path;
 109         if (strstr(p, "local"))
 110                 p = "/lib";
 111
 112         snprintf(path, sizeof(path), "%s/%s", p, file);
 113
 114         return path;
 115 }
 116
 117 static int elf64_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 118 {
 119         Elf64_Ehdr *e;
 120         Elf64_Phdr *ph;
 121         int i;
 122
 123         e = (Elf64_Ehdr *) map;
 124         ph = (Elf64_Phdr *) (map + e->e_phoff);
 125
 126         for (i = 0; i < e->e_phnum; i++) {
 127                 if (ph[i].p_type == type) {
 128                         *offset = ph[i].p_offset;
 129                         if (size)
 130                                 *size = ph[i].p_filesz;
 131                         if (vaddr)
 132                                 *vaddr = ph[i].p_vaddr;
 133                         return 0;
 134                 }
 135         }
 136
 137         return -1;
 138 }
 139
 140 static int elf32_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 141 {
 142         Elf32_Ehdr *e;
 143         Elf32_Phdr *ph;
 144         int i;
 145
 146         e = (Elf32_Ehdr *) map;
 147         ph = (Elf32_Phdr *) (map + e->e_phoff);
 148
 149         for (i = 0; i < e->e_phnum; i++) {
 150                 if (ph[i].p_type == type) {
 151                         *offset = ph[i].p_offset;
 152                         if (size)
 153                                 *size = ph[i].p_filesz;
 154                         if (vaddr)
 155                                 *vaddr = ph[i].p_vaddr;
 156                         return 0;
 157                 }
 158         }
 159
 160         return -1;
 161 }
 162
 163 static int elf_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 164 {
 165         int clazz = map[EI_CLASS];
 166
 167         if (clazz == ELFCLASS32)
 168                 return elf32_find_section(map, type, offset, size, vaddr);
 169         else if (clazz == ELFCLASS64)
 170                 return elf64_find_section(map, type, offset, size, vaddr);
 171
 172         ERROR("unknown elf format %d\n", clazz);
 173
 174         return -1;
 175 }
 176
 177 static int elf32_scan_dynamic(char *map, int dyn_offset, int dyn_size, int load_offset)
 178 {
 179         Elf32_Dyn *dynamic = (Elf32_Dyn *) (map + dyn_offset);
 180         char *strtab = NULL;
 181
 182         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 183                 Elf32_Dyn *curr = dynamic;
 184
 185                 dynamic++;
 186                 if (curr->d_tag != DT_STRTAB)
 187                         continue;
 188
 189                 strtab = map + (curr->d_un.d_val - load_offset);
 190                 break;
 191         }
 192
 193         if (!strtab)
 194                 return -1;
 195
 196         dynamic = (Elf32_Dyn *) (map + dyn_offset);
 197         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 198                 Elf32_Dyn *curr = dynamic;
 199
 200                 dynamic++;
 201                 if (curr->d_tag != DT_NEEDED)
 202                         continue;
 203
 204                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 205                         return -1;
 206         }
 207
 208         return 0;
 209 }
 210
 211 static int elf64_scan_dynamic(char *map, int dyn_offset, int dyn_size, int load_offset)
 212 {
 213         Elf64_Dyn *dynamic = (Elf64_Dyn *) (map + dyn_offset);
 214         char *strtab = NULL;
 215
 216         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 217                 Elf64_Dyn *curr = dynamic;
 218
 219                 dynamic++;
 220                 if (curr->d_tag != DT_STRTAB)
 221                         continue;
 222
 223                 strtab = map + (curr->d_un.d_val - load_offset);
 224                 break;
 225         }
 226
 227         if (!strtab)
 228                 return -1;
 229
 230         dynamic = (Elf64_Dyn *) (map + dyn_offset);
 231         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 232                 Elf64_Dyn *curr = dynamic;
 233
 234                 dynamic++;
 235                 if (curr->d_tag != DT_NEEDED)
 236                         continue;
 237
 238                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 239                         return -1;
 240         }
 241
 242         return 0;
 243 }
 244
 245 int elf_load_deps(char *library)
 246 {
 247         unsigned int dyn_offset, dyn_size;
 248         unsigned int load_offset, load_vaddr;
 249         struct stat s;
 250         char *map = NULL, *dir = NULL;
 251         int clazz, fd, ret = -1;
 252
 253         if (avl_find(&libraries, library))
 254                 return 0;
 255
 256         fd = elf_open(&dir, library);
 257
 258         if (fd < 0) {
 259                 ERROR("failed to open %s\n", library);
 260                 return -1;
 261         }
 262
 263         if (fstat(fd, &s) == -1) {
 264                 ERROR("failed to stat %s\n", library);
 265                 ret = -1;
 266                 goto err_out;
 267         }
 268
 269         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 270         if (map == MAP_FAILED) {
 271                 ERROR("failed to mmap %s\n", library);
 272                 ret = -1;
 273                 goto err_out;
 274         }
 275
 276         if (elf_find_section(map, PT_LOAD, &load_offset, NULL, &load_vaddr)) {
 277                 ERROR("failed to load the .load section from %s\n", library);
 278                 ret = -1;
 279                 goto err_out;
 280         }
 281
 282         if (elf_find_section(map, PT_DYNAMIC, &dyn_offset, &dyn_size, NULL)) {
 283                 ERROR("failed to load the .dynamic section from %s\n", library);
 284                 ret = -1;
 285                 goto err_out;
 286         }
 287
 288         if (dir) {
 289                 alloc_library(dir, library);
 290         } else {
 291                 char *elf = strdup(library);
 292
 293                 alloc_library(dirname(elf), basename(library));
 294                 free(elf);
 295         }
 296         clazz = map[EI_CLASS];
 297
 298         if (clazz == ELFCLASS32)
 299                 ret = elf32_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 300         else if (clazz == ELFCLASS64)
 301                 ret = elf64_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 302
 303 err_out:
 304         if (map)
 305                 munmap(map, s.st_size);
 306         close(fd);
 307
 308         return ret;
 309 }
 310
 311 void load_ldso_conf(const char *conf)
 312 {
 313         FILE* fp = fopen(conf, "r");
 314         char line[256];
 315
 316         if (!fp) {
 317                 DEBUG("failed to open %s\n", conf);
 318                 return;
 319         }
 320
 321         while (!feof(fp)) {
 322                 int len;
 323
 324                 if (!fgets(line, 256, fp))
 325                         break;
 326                 len = strlen(line);
 327                 if (len < 2)
 328                         continue;
 329                 if (*line == '#')
 330                         continue;
 331                 if (line[len - 1] == '\n')
 332                         line[len - 1] = '\0';
 333                 if (!strncmp(line, "include ", 8)) {
 334                         char *sep = strstr(line, " ");
 335                         glob_t gl;
 336                         int i;
 337
 338                         if (!sep)
 339                                 continue;;
 340                         while (*sep == ' ')
 341                                 sep++;
 342                         if (glob(sep, GLOB_NOESCAPE | GLOB_MARK, NULL, &gl)) {
 343                                 ERROR("glob failed on %s\n", sep);
 344                                 continue;
 345                         }
 346                         for (i = 0; i < gl.gl_pathc; i++)
 347                                 load_ldso_conf(gl.gl_pathv[i]);
 348                         globfree(&gl);
 349                 } else {
 350                         alloc_library_path(line);
 351                 }
 352         }
 353
 354         fclose(fp);
 355 }