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