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/syscall.h>
  16 #include <sys/mman.h>
  17 #include <sys/utsname.h>
  18 #include <sys/types.h>
  19 #include <sys/wait.h>
  20
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <sys/syscall.h>
  24 #include <sys/types.h>
  25 #include <sys/mount.h>
  26 #include <values.h>
  27 #include <errno.h>
  28 #include <stdio.h>
  29 #include <string.h>
  30 #include <sys/stat.h>
  31 #include <fcntl.h>
  32 #include <syslog.h>
  33 #include <libgen.h>
  34 #include <glob.h>
  35 #include <elf.h>
  36
  37 #include <libubox/avl.h>
  38 #include <libubox/avl-cmp.h>
  39 #include <libubox/utils.h>
  40 #include <libubox/list.h>
  41 #include <libubox/uloop.h>
  42
  43 #include "elf.h"
  44
  45 struct avl_tree libraries;
  46 static LIST_HEAD(library_paths);
  47
  48 void alloc_library_path(const char *path)
  49 {
  50         struct library_path *p;
  51         char *_path;
  52
  53         p = calloc_a(sizeof(*p),
  54                 &_path, strlen(path) + 1);
  55         if (!p)
  56                 return;
  57
  58         p->path = strcpy(_path, path);
  59
  60         list_add_tail(&p->list, &library_paths);
  61         DEBUG("adding ld.so path %s\n", path);
  62 }
  63
  64 static void alloc_library(const char *path, const char *name)
  65 {
  66         struct library *l;
  67         char *_name, *_path;
  68
  69         l = calloc_a(sizeof(*l),
  70                 &_path, strlen(path) + 1,
  71                 &_name, strlen(name) + 1);
  72         if (!l)
  73                 return;
  74
  75         l->avl.key = l->name = strcpy(_name, name);
  76         l->path = strcpy(_path, path);
  77
  78         avl_insert(&libraries, &l->avl);
  79         DEBUG("adding library %s/%s\n", path, name);
  80 }
  81
  82 static int elf_open(char **dir, char *file)
  83 {
  84         struct library_path *p;
  85         char path[256];
  86         int fd = -1;
  87
  88         *dir = NULL;
  89
  90         list_for_each_entry(p, &library_paths, list) {
  91                 if (strlen(p->path))
  92                         snprintf(path, sizeof(path), "%s/%s", p->path, file);
  93                 else
  94                         strncpy(path, file, sizeof(path));
  95                 fd = open(path, O_RDONLY);
  96                 if (fd >= 0) {
  97                         *dir = p->path;
  98                         break;
  99                 }
 100         }
 101
 102         if (fd == -1)
 103                 fd = open(file, O_RDONLY);
 104
 105         return fd;
 106 }
 107
 108 char* find_lib(char *file)
 109 {
 110         struct library *l;
 111         static char path[256];
 112         const char *p;
 113
 114         l = avl_find_element(&libraries, file, l, avl);
 115         if (!l)
 116                 return NULL;
 117
 118         p = l->path;
 119         if (strstr(p, "local"))
 120                 p = "/lib";
 121
 122         snprintf(path, sizeof(path), "%s/%s", p, file);
 123
 124         return path;
 125 }
 126
 127 static int elf64_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 128 {
 129         Elf64_Ehdr *e;
 130         Elf64_Phdr *ph;
 131         int i;
 132
 133         e = (Elf64_Ehdr *) map;
 134         ph = (Elf64_Phdr *) (map + e->e_phoff);
 135
 136         for (i = 0; i < e->e_phnum; i++) {
 137                 if (ph[i].p_type == type) {
 138                         *offset = ph[i].p_offset;
 139                         if (size)
 140                                 *size = ph[i].p_filesz;
 141                         if (vaddr)
 142                                 *vaddr = ph[i].p_vaddr;
 143                         return 0;
 144                 }
 145         }
 146
 147         return -1;
 148 }
 149
 150 static int elf32_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 151 {
 152         Elf32_Ehdr *e;
 153         Elf32_Phdr *ph;
 154         int i;
 155
 156         e = (Elf32_Ehdr *) map;
 157         ph = (Elf32_Phdr *) (map + e->e_phoff);
 158
 159         for (i = 0; i < e->e_phnum; i++) {
 160                 if (ph[i].p_type == type) {
 161                         *offset = ph[i].p_offset;
 162                         if (size)
 163                                 *size = ph[i].p_filesz;
 164                         if (vaddr)
 165                                 *vaddr = ph[i].p_vaddr;
 166                         return 0;
 167                 }
 168         }
 169
 170         return -1;
 171 }
 172
 173 static int elf_find_section(char *map, unsigned int type, unsigned int *offset, unsigned int *size, unsigned int *vaddr)
 174 {
 175         int clazz = map[EI_CLASS];
 176
 177         if (clazz == ELFCLASS32)
 178                 return elf32_find_section(map, type, offset, size, vaddr);
 179         else if (clazz == ELFCLASS64)
 180                 return elf64_find_section(map, type, offset, size, vaddr);
 181
 182         ERROR("unknown elf format %d\n", clazz);
 183
 184         return -1;
 185 }
 186
 187 static int elf32_scan_dynamic(char *map, int dyn_offset, int dyn_size, int load_offset)
 188 {
 189         Elf32_Dyn *dynamic = (Elf32_Dyn *) (map + dyn_offset);
 190         char *strtab = NULL;
 191
 192         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 193                 Elf32_Dyn *curr = dynamic;
 194
 195                 dynamic++;
 196                 if (curr->d_tag != DT_STRTAB)
 197                         continue;
 198
 199                 strtab = map + (curr->d_un.d_val - load_offset);
 200                 break;
 201         }
 202
 203         if (!strtab)
 204                 return -1;
 205
 206         dynamic = (Elf32_Dyn *) (map + dyn_offset);
 207         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 208                 Elf32_Dyn *curr = dynamic;
 209
 210                 dynamic++;
 211                 if (curr->d_tag != DT_NEEDED)
 212                         continue;
 213
 214                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 215                         return -1;
 216         }
 217
 218         return 0;
 219 }
 220
 221 static int elf64_scan_dynamic(char *map, int dyn_offset, int dyn_size, int load_offset)
 222 {
 223         Elf64_Dyn *dynamic = (Elf64_Dyn *) (map + dyn_offset);
 224         char *strtab = NULL;
 225
 226         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 227                 Elf64_Dyn *curr = dynamic;
 228
 229                 dynamic++;
 230                 if (curr->d_tag != DT_STRTAB)
 231                         continue;
 232
 233                 strtab = map + (curr->d_un.d_val - load_offset);
 234                 break;
 235         }
 236
 237         if (!strtab)
 238                 return -1;
 239
 240         dynamic = (Elf64_Dyn *) (map + dyn_offset);
 241         while ((void *) dynamic < (void *) (map + dyn_offset + dyn_size)) {
 242                 Elf64_Dyn *curr = dynamic;
 243
 244                 dynamic++;
 245                 if (curr->d_tag != DT_NEEDED)
 246                         continue;
 247
 248                 if (elf_load_deps(&strtab[curr->d_un.d_val]))
 249                         return -1;
 250         }
 251
 252         return 0;
 253 }
 254
 255 int elf_load_deps(char *library)
 256 {
 257         unsigned int dyn_offset, dyn_size;
 258         unsigned int load_offset, load_vaddr;
 259         struct stat s;
 260         char *map = NULL, *dir = NULL;
 261         int clazz, fd, ret = -1;
 262
 263         if (avl_find(&libraries, library))
 264                 return 0;
 265
 266         fd = elf_open(&dir, library);
 267
 268         if (fd < 0) {
 269                 ERROR("failed to open %s\n", library);
 270                 return -1;
 271         }
 272
 273         if (fstat(fd, &s) == -1) {
 274                 ERROR("failed to stat %s\n", library);
 275                 ret = -1;
 276                 goto err_out;
 277         }
 278
 279         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 280         if (map == MAP_FAILED) {
 281                 ERROR("failed to mmap %s\n", library);
 282                 ret = -1;
 283                 goto err_out;
 284         }
 285
 286         if (elf_find_section(map, PT_LOAD, &load_offset, NULL, &load_vaddr)) {
 287                 ERROR("failed to load the .load section from %s\n", library);
 288                 ret = -1;
 289                 goto err_out;
 290         }
 291
 292         if (elf_find_section(map, PT_DYNAMIC, &dyn_offset, &dyn_size, NULL)) {
 293                 ERROR("failed to load the .dynamic section from %s\n", library);
 294                 ret = -1;
 295                 goto err_out;
 296         }
 297
 298         if (dir) {
 299                 alloc_library(dir, library);
 300         } else {
 301                 char *elf = strdup(library);
 302
 303                 alloc_library(dirname(elf), basename(library));
 304                 free(elf);
 305         }
 306         clazz = map[EI_CLASS];
 307
 308         if (clazz == ELFCLASS32)
 309                 ret = elf32_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 310         else if (clazz == ELFCLASS64)
 311                 ret = elf64_scan_dynamic(map, dyn_offset, dyn_size, load_vaddr - load_offset);
 312
 313 err_out:
 314         if (map)
 315                 munmap(map, s.st_size);
 316         close(fd);
 317
 318         return ret;
 319 }
 320
 321 void load_ldso_conf(const char *conf)
 322 {
 323         FILE* fp = fopen(conf, "r");
 324         char line[256];
 325
 326         if (!fp) {
 327                 DEBUG("failed to open %s\n", conf);
 328                 return;
 329         }
 330
 331         while (!feof(fp)) {
 332                 int len;
 333
 334                 if (!fgets(line, 256, fp))
 335                         break;
 336                 len = strlen(line);
 337                 if (len < 2)
 338                         continue;
 339                 if (*line == '#')
 340                         continue;
 341                 if (line[len - 1] == '\n')
 342                         line[len - 1] = '\0';
 343                 if (!strncmp(line, "include ", 8)) {
 344                         char *sep = strstr(line, " ");
 345                         glob_t gl;
 346                         int i;
 347
 348                         if (!sep)
 349                                 continue;;
 350                         while (*sep == ' ')
 351                                 sep++;
 352                         if (glob(sep, GLOB_NOESCAPE | GLOB_MARK, NULL, &gl)) {
 353                                 ERROR("glob failed on %s\n", sep);
 354                                 continue;
 355                         }
 356                         for (i = 0; i < gl.gl_pathc; i++)
 357                                 load_ldso_conf(gl.gl_pathv[i]);
 358                         globfree(&gl);
 359                 } else {
 360                         struct stat s;
 361
 362                         if (stat(line, &s))
 363                                 continue;
 364                         alloc_library_path(line);
 365                 }
 366         }
 367
 368         fclose(fp);
 369 }