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 <string.h>
  20 #include <sys/stat.h>
  21 #include <fcntl.h>
  22 #include <libgen.h>
  23 #include <glob.h>
  24 #include <elf.h>
  25 #include <linux/limits.h>
  26
  27 #include <libubox/utils.h>
  28
  29 #include "elf.h"
  30 #include "log.h"
  31
  32 struct avl_tree libraries;
  33 static LIST_HEAD(library_paths);
  34
  35 static void alloc_library_path(const char *path)
  36 {
  37         struct stat s;
  38         if (stat(path, &s))
  39                 return;
  40
  41         struct library_path *p;
  42         char *_path;
  43
  44         p = calloc_a(sizeof(*p),
  45                 &_path, strlen(path) + 1);
  46         if (!p)
  47                 return;
  48
  49         p->path = strcpy(_path, path);
  50
  51         list_add_tail(&p->list, &library_paths);
  52         DEBUG("adding ld.so path %s\n", path);
  53 }
  54
  55 static void alloc_library(const char *path, const char *name)
  56 {
  57         struct library *l;
  58         char *_name, *_path;
  59
  60         l = calloc_a(sizeof(*l),
  61                 &_path, strlen(path) + 1,
  62                 &_name, strlen(name) + 1);
  63         if (!l)
  64                 return;
  65
  66         l->avl.key = l->name = strcpy(_name, name);
  67         l->path = strcpy(_path, path);
  68
  69         avl_insert(&libraries, &l->avl);
  70         DEBUG("adding library %s/%s\n", path, name);
  71 }
  72
  73 static int elf_open(char **dir, const char *file)
  74 {
  75         struct library_path *p;
  76         char path[PATH_MAX];
  77         int fd = -1;
  78
  79         *dir = NULL;
  80
  81         list_for_each_entry(p, &library_paths, list) {
  82                 if (strlen(p->path))
  83                         snprintf(path, sizeof(path), "%s/%s", p->path, file);
  84                 else
  85                         strncpy(path, file, sizeof(path));
  86                 fd = open(path, O_RDONLY);
  87                 if (fd >= 0) {
  88                         *dir = p->path;
  89                         break;
  90                 }
  91         }
  92
  93         if (fd == -1)
  94                 fd = open(file, O_RDONLY);
  95
  96         return fd;
  97 }
  98
  99 const char* find_lib(const char *file)
 100 {
 101         struct library *l;
 102         static char path[PATH_MAX];
 103
 104         l = avl_find_element(&libraries, file, l, avl);
 105         if (!l)
 106                 return NULL;
 107
 108         snprintf(path, sizeof(path), "%s/%s", l->path, file);
 109
 110         return path;
 111 }
 112
 113 static int elf64_find_section(const char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 114 {
 115         Elf64_Ehdr *e;
 116         Elf64_Phdr *ph;
 117         int i;
 118
 119         e = (Elf64_Ehdr *) map;
 120         ph = (Elf64_Phdr *) (map + e->e_phoff);
 121
 122         for (i = 0; i < e->e_phnum; i++) {
 123                 if (ph[i].p_type == type) {
 124                         *offset = ph[i].p_offset;
 125                         if (size)
 126                                 *size = ph[i].p_filesz;
 127                         if (vaddr)
 128                                 *vaddr = ph[i].p_vaddr;
 129                         return 0;
 130                 }
 131         }
 132
 133         return -1;
 134 }
 135
 136 static int elf32_find_section(const char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 137 {
 138         Elf32_Ehdr *e;
 139         Elf32_Phdr *ph;
 140         int i;
 141
 142         e = (Elf32_Ehdr *) map;
 143         ph = (Elf32_Phdr *) (map + e->e_phoff);
 144
 145         for (i = 0; i < e->e_phnum; i++) {
 146                 if (ph[i].p_type == type) {
 147                         *offset = ph[i].p_offset;
 148                         if (size)
 149                                 *size = ph[i].p_filesz;
 150                         if (vaddr)
 151                                 *vaddr = ph[i].p_vaddr;
 152                         return 0;
 153                 }
 154         }
 155
 156         return -1;
 157 }
 158
 159 static int elf_find_section(const char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 160 {
 161         int clazz = map[EI_CLASS];
 162
 163         if (clazz == ELFCLASS32)
 164                 return elf32_find_section(map, type, offset, size, vaddr);
 165         else if (clazz == ELFCLASS64)
 166                 return elf64_find_section(map, type, offset, size, vaddr);
 167
 168         ERROR("unknown elf format %d\n", clazz);
 169
 170         return -1;
 171 }
 172
 173 static int elf32_scan_dynamic(const char *map, int dyn_offset, int dyn_size, int load_offset)
 174 {
 175         Elf32_Dyn *dynamic = (Elf32_Dyn *) (map + dyn_offset);
 176         const char *strtab = NULL;
 177
 178         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 179                 Elf32_Dyn *curr = dynamic;
 180
 181                 dynamic++;
 182                 if (curr->d_tag != DT_STRTAB)
 183                         continue;
 184
 185                 strtab = map + (curr->d_un.d_val - load_offset);
 186                 break;
 187         }
 188
 189         if (!strtab)
 190                 return -1;
 191
 192         dynamic = (Elf32_Dyn *) (map + dyn_offset);
 193         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 194                 Elf32_Dyn *curr = dynamic;
 195
 196                 dynamic++;
 197                 if (curr->d_tag != DT_NEEDED)
 198                         continue;
 199
 200                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 201                         return -1;
 202         }
 203
 204         return 0;
 205 }
 206
 207 static int elf64_scan_dynamic(const char *map, int dyn_offset, int dyn_size, int load_offset)
 208 {
 209         Elf64_Dyn *dynamic = (Elf64_Dyn *) (map + dyn_offset);
 210         const char *strtab = NULL;
 211
 212         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 213                 Elf64_Dyn *curr = dynamic;
 214
 215                 dynamic++;
 216                 if (curr->d_tag != DT_STRTAB)
 217                         continue;
 218
 219                 strtab = map + (curr->d_un.d_val - load_offset);
 220                 break;
 221         }
 222
 223         if (!strtab)
 224                 return -1;
 225
 226         dynamic = (Elf64_Dyn *) (map + dyn_offset);
 227         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 228                 Elf64_Dyn *curr = dynamic;
 229
 230                 dynamic++;
 231                 if (curr->d_tag != DT_NEEDED)
 232                         continue;
 233
 234                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 235                         return -1;
 236         }
 237
 238         return 0;
 239 }
 240
 241 int elf_load_deps(const char *library)
 242 {
 243         unsigned int dyn_offset, dyn_size;
 244         unsigned int load_offset, load_vaddr;
 245         struct stat s;
 246         char *map = NULL, *dir = NULL;
 247         int clazz, fd, ret = -1;
 248
 249         if (avl_find(&libraries, library))
 250                 return 0;
 251
 252         fd = elf_open(&dir, library);
 253
 254         if (fd < 0) {
 255                 ERROR("failed to open %s\n", library);
 256                 return -1;
 257         }
 258
 259         if (fstat(fd, &s) == -1) {
 260                 ERROR("failed to stat %s\n", library);
 261                 ret = -1;
 262                 goto err_out;
 263         }
 264
 265         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 266         if (map == MAP_FAILED) {
 267                 ERROR("failed to mmap %s\n", library);
 268                 ret = -1;
 269                 goto err_out;
 270         }
 271
 272         if (elf_find_section(map, PT_LOAD, &load_offset, NULL, &load_vaddr)) {
 273                 ERROR("failed to load the .load section from %s\n", library);
 274                 ret = -1;
 275                 goto err_out;
 276         }
 277
 278         if (elf_find_section(map, PT_DYNAMIC, &dyn_offset, &dyn_size, NULL)) {
 279                 ERROR("failed to load the .dynamic section from %s\n", library);
 280                 ret = -1;
 281                 goto err_out;
 282         }
 283
 284         if (dir) {
 285                 alloc_library(dir, library);
 286         } else {
 287                 char *elf1 = strdup(library);
 288                 char *elf2 = strdup(library);
 289
 290                 alloc_library(dirname(elf1), basename(elf2));
 291                 free(elf1);
 292                 free(elf2);
 293         }
 294         clazz = map[EI_CLASS];
 295
 296         if (clazz == ELFCLASS32)
 297                 ret = elf32_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 298         else if (clazz == ELFCLASS64)
 299                 ret = elf64_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 300
 301 err_out:
 302         if (map)
 303                 munmap(map, s.st_size);
 304         close(fd);
 305
 306         return ret;
 307 }
 308
 309 static void load_ldso_conf(const char *conf)
 310 {
 311         FILE* fp = fopen(conf, "r");
 312         char line[PATH_MAX];
 313
 314         if (!fp) {
 315                 DEBUG("failed to open %s\n", conf);
 316                 return;
 317         }
 318
 319         while (!feof(fp)) {
 320                 int len;
 321
 322                 if (!fgets(line, sizeof(line), fp))
 323                         break;
 324                 len = strlen(line);
 325                 if (len < 2)
 326                         continue;
 327                 if (*line == '#')
 328                         continue;
 329                 if (line[len - 1] == '\n')
 330                         line[len - 1] = '\0';
 331                 if (!strncmp(line, "include ", 8)) {
 332                         char *sep = strstr(line, " ");
 333                         glob_t gl;
 334                         int i;
 335
 336                         if (!sep)
 337                                 continue;;
 338                         while (*sep == ' ')
 339                                 sep++;
 340                         if (glob(sep, GLOB_NOESCAPE | GLOB_MARK, NULL, &gl)) {
 341                                 ERROR("glob failed on %s\n", sep);
 342                                 continue;
 343                         }
 344                         for (i = 0; i < gl.gl_pathc; i++)
 345                                 load_ldso_conf(gl.gl_pathv[i]);
 346                         globfree(&gl);
 347                 } else {
 348                         alloc_library_path(line);
 349                 }
 350         }
 351
 352         fclose(fp);
 353 }
 354
 355 void init_library_search(void)
 356 {
 357         avl_init(&libraries, avl_strcmp, false, NULL);
 358         alloc_library_path("/lib");
 359         alloc_library_path("/lib64");
 360         alloc_library_path("/usr/lib");
 361         load_ldso_conf("/etc/ld.so.conf");
 362 }