jail/fs.c

   1 /*
   2  * Copyright (C) 2015 John Crispin <blogic@openwrt.org>
   3  * Copyright (C) 2015 Etienne Champetier <champetier.etienne@gmail.com>
   4  * Copyright (C) 2020 Daniel Golle <daniel@makrotopia.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU Lesser General Public License version 2.1
   8  * as published by the Free Software Foundation
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #define _GNU_SOURCE
  17
  18 #include <assert.h>
  19 #include <elf.h>
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <linux/limits.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include <sys/mman.h>
  27 #include <unistd.h>
  28 #include <libgen.h>
  29
  30 #include <libubox/avl.h>
  31 #include <libubox/avl-cmp.h>
  32 #include <libubox/blobmsg.h>
  33 #include <libubox/list.h>
  34
  35 #include "elf.h"
  36 #include "fs.h"
  37 #include "jail.h"
  38 #include "log.h"
  39
  40 struct mount {
  41         struct avl_node avl;
  42         const char *source;
  43         const char *target;
  44         const char *filesystemtype;
  45         unsigned long mountflags;
  46         const char *optstr;
  47         int error;
  48 };
  49
  50 struct avl_tree mounts;
  51
  52 int mkdir_p(char *dir, mode_t mask)
  53 {
  54         char *l = strrchr(dir, '/');
  55         int ret;
  56
  57         if (!l)
  58                 return 0;
  59
  60         *l = '\0';
  61
  62         if (mkdir_p(dir, mask))
  63                 return -1;
  64
  65         *l = '/';
  66
  67         ret = mkdir(dir, mask);
  68         if (ret && errno == EEXIST)
  69                 return 0;
  70
  71         if (ret)
  72                 ERROR("mkdir(%s, %d) failed: %m\n", dir, mask);
  73
  74         return ret;
  75 }
  76
  77 static int do_mount(const char *root, const char *source, const char *target, const char *filesystemtype,
  78                     unsigned long orig_mountflags, const char *optstr, int error)
  79 {
  80         struct stat s;
  81         char new[PATH_MAX];
  82         int fd;
  83         bool is_bind = (orig_mountflags & MS_BIND);
  84         unsigned long mountflags = orig_mountflags;
  85
  86         if (is_bind && stat(source, &s)) {
  87                 ERROR("stat(%s) failed: %m\n", source);
  88                 return error;
  89         }
  90
  91         snprintf(new, sizeof(new), "%s%s", root, target?target:source);
  92
  93         if (!is_bind || S_ISDIR(s.st_mode)) {
  94                 mkdir_p(new, 0755);
  95         } else {
  96                 mkdir_p(dirname(new), 0755);
  97                 snprintf(new, sizeof(new), "%s%s", root, target?target:source);
  98                 fd = creat(new, 0644);
  99                 if (fd == -1) {
 100                         ERROR("creat(%s) failed: %m\n", new);
 101                         return -1;
 102                 }
 103                 close(fd);
 104         }
 105
 106         if (mountflags & MS_BIND) {
 107                 if (mount(source, new, filesystemtype, MS_BIND, optstr)) {
 108                         ERROR("failed to mount -B %s %s: %m\n", source, new);
 109                 }
 110                 mountflags |= MS_REMOUNT;
 111         }
 112
 113         if (mount(source, new, filesystemtype, mountflags, optstr)) {
 114                 ERROR("failed to mount %s %s: %m\n", source, new);
 115                 return -1;
 116         }
 117
 118         DEBUG("mount %s%s %s (%s)\n", (mountflags & MS_BIND)?"-B ":"", source, new,
 119               (mountflags & MS_RDONLY)?"ro":"rw");
 120
 121         return 0;
 122 }
 123
 124 int add_mount(const char *source, const char *target, const char *filesystemtype,
 125               unsigned long mountflags, const char *optstr, int error)
 126 {
 127         assert(target != NULL);
 128
 129         if (avl_find(&mounts, target))
 130                 return 1;
 131
 132         struct mount *m;
 133         m = calloc(1, sizeof(struct mount));
 134         assert(m != NULL);
 135         m->avl.key = m->target = strdup(target);
 136         if (source)
 137                 m->source = strdup(source);
 138         if (filesystemtype)
 139                 m->filesystemtype = strdup(filesystemtype);
 140         m->mountflags = mountflags;
 141         m->error = error;
 142
 143         avl_insert(&mounts, &m->avl);
 144         DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", m->source, m->target,
 145                 !!(m->mountflags & MS_BIND), !!(m->mountflags & MS_RDONLY), m->error != 0);
 146
 147         return 0;
 148 }
 149
 150 int add_mount_bind(const char *path, int readonly, int error)
 151 {
 152         unsigned long mountflags = MS_BIND;
 153
 154         if (readonly)
 155                 mountflags |= MS_RDONLY;
 156
 157         return add_mount(path, path, NULL, mountflags, NULL, error);
 158 }
 159
 160
 161 enum {
 162         OCI_MOUNT_SOURCE,
 163         OCI_MOUNT_DESTINATION,
 164         OCI_MOUNT_TYPE,
 165         OCI_MOUNT_OPTIONS,
 166         __OCI_MOUNT_MAX,
 167 };
 168
 169 static const struct blobmsg_policy oci_mount_policy[] = {
 170         [OCI_MOUNT_SOURCE] = { "source", BLOBMSG_TYPE_STRING },
 171         [OCI_MOUNT_DESTINATION] = { "destination", BLOBMSG_TYPE_STRING },
 172         [OCI_MOUNT_TYPE] = { "type", BLOBMSG_TYPE_STRING },
 173         [OCI_MOUNT_OPTIONS] = { "options", BLOBMSG_TYPE_ARRAY },
 174 };
 175
 176 struct mount_opt {
 177         struct list_head list;
 178         char *optstr;
 179 };
 180
 181 static int parseOCImountopts(struct blob_attr *msg, unsigned long *mount_flags, char **mount_data, int *error)
 182 {
 183         struct blob_attr *cur;
 184         int rem;
 185         unsigned long mf = 0;
 186         char *tmp;
 187         struct list_head fsopts = LIST_HEAD_INIT(fsopts);
 188         size_t len = 0;
 189         struct mount_opt *opt;
 190
 191         blobmsg_for_each_attr(cur, msg, rem) {
 192                 tmp = blobmsg_get_string(cur);
 193                 if (!strcmp("ro", tmp))
 194                         mf |= MS_RDONLY;
 195                 else if (!strcmp("rw", tmp))
 196                         mf &= ~MS_RDONLY;
 197                 else if (!strcmp("bind", tmp))
 198                         mf = MS_BIND;
 199                 else if (!strcmp("rbind", tmp))
 200                         mf |= MS_BIND | MS_REC;
 201                 else if (!strcmp("sync", tmp))
 202                         mf |= MS_SYNCHRONOUS;
 203                 else if (!strcmp("async", tmp))
 204                         mf &= ~MS_SYNCHRONOUS;
 205                 else if (!strcmp("atime", tmp))
 206                         mf &= ~MS_NOATIME;
 207                 else if (!strcmp("noatime", tmp))
 208                         mf |= MS_NOATIME;
 209                 else if (!strcmp("defaults", tmp))
 210                         mf = 0; /* rw, suid, dev, exec, auto, nouser, and async */
 211                 else if (!strcmp("dev", tmp))
 212                         mf &= ~MS_NODEV;
 213                 else if (!strcmp("nodev", tmp))
 214                         mf |= MS_NODEV;
 215                 else if (!strcmp("diratime", tmp))
 216                         mf &= ~MS_NODIRATIME;
 217                 else if (!strcmp("nodiratime", tmp))
 218                         mf |= MS_NODIRATIME;
 219                 else if (!strcmp("dirsync", tmp))
 220                         mf |= MS_DIRSYNC;
 221                 else if (!strcmp("exec", tmp))
 222                         mf &= ~MS_NOEXEC;
 223                 else if (!strcmp("noexec", tmp))
 224                         mf |= MS_NOEXEC;
 225                 else if (!strcmp("mand", tmp))
 226                         mf |= MS_MANDLOCK;
 227                 else if (!strcmp("nomand", tmp))
 228                         mf &= ~MS_MANDLOCK;
 229                 else if (!strcmp("relatime", tmp))
 230                         mf |= MS_RELATIME;
 231                 else if (!strcmp("norelatime", tmp))
 232                         mf &= ~MS_RELATIME;
 233                 else if (!strcmp("strictatime", tmp))
 234                         mf |= MS_STRICTATIME;
 235                 else if (!strcmp("nostrictatime", tmp))
 236                         mf &= ~MS_STRICTATIME;
 237                 else if (!strcmp("lazytime", tmp))
 238                         mf |= MS_LAZYTIME;
 239                 else if (!strcmp("nostrictatime", tmp))
 240                         mf &= ~MS_LAZYTIME;
 241                 else if (!strcmp("suid", tmp))
 242                         mf &= ~MS_NOSUID;
 243                 else if (!strcmp("nosuid", tmp))
 244                         mf |= MS_NOSUID;
 245                 else if (!strcmp("remount", tmp))
 246                         mf |= MS_REMOUNT;
 247                 else if(!strcmp("nofail", tmp))
 248                         *error = 0;
 249                 else if (!strcmp("auto", tmp) ||
 250                          !strcmp("noauto", tmp) ||
 251                          !strcmp("user", tmp) ||
 252                          !strcmp("group", tmp) ||
 253                          !strcmp("_netdev", tmp))
 254                         DEBUG("ignoring built-in mount option %s\n", tmp);
 255                 else {
 256                         /* filesystem-specific free-form option */
 257                         opt = calloc(1, sizeof(*opt));
 258                         opt->optstr = tmp;
 259                         list_add_tail(&opt->list, &fsopts);
 260                 }
 261         };
 262
 263         *mount_flags = mf;
 264
 265         list_for_each_entry(opt, &fsopts, list) {
 266                 if (len)
 267                         ++len;
 268
 269                 len += strlen(opt->optstr);
 270         };
 271
 272         if (!len)
 273                 return 0;
 274
 275         *mount_data = calloc(len + 1, sizeof(char));
 276         if (!mount_data)
 277                 return ENOMEM;
 278
 279         len = 0;
 280         list_for_each_entry(opt, &fsopts, list) {
 281                 if (len)
 282                         strcat(*mount_data, ",");
 283
 284                 strcat(*mount_data, opt->optstr);
 285                 ++len;
 286         };
 287
 288         list_del(&fsopts);
 289
 290         DEBUG("mount flags(%08lx) fsopts(\"%s\")\n", mf, *mount_data?:"");
 291
 292         return 0;
 293 };
 294
 295 int parseOCImount(struct blob_attr *msg)
 296 {
 297         struct blob_attr *tb[__OCI_MOUNT_MAX];
 298         unsigned long mount_flags = 0;
 299         char *mount_data = NULL;
 300         int ret, err = -1;
 301
 302         blobmsg_parse(oci_mount_policy, __OCI_MOUNT_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 303
 304         if (!tb[OCI_MOUNT_DESTINATION])
 305                 return EINVAL;
 306
 307         if (tb[OCI_MOUNT_OPTIONS]) {
 308                 ret = parseOCImountopts(tb[OCI_MOUNT_OPTIONS], &mount_flags, &mount_data, &err);
 309                 if (ret)
 310                         return ret;
 311         }
 312
 313         add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL,
 314                   blobmsg_get_string(tb[OCI_MOUNT_DESTINATION]),
 315                   tb[OCI_MOUNT_TYPE] ? blobmsg_get_string(tb[OCI_MOUNT_TYPE]) : NULL,
 316                   mount_flags, mount_data, err);
 317
 318         return 0;
 319 };
 320
 321
 322 int mount_all(const char *jailroot) {
 323         struct library *l;
 324         struct mount *m;
 325
 326         avl_for_each_element(&libraries, l, avl)
 327                 add_mount_bind(l->path, 1, -1);
 328
 329         avl_for_each_element(&mounts, m, avl)
 330                 if (do_mount(jailroot, m->source, m->target, m->filesystemtype, m->mountflags, m->optstr, m->error))
 331                         return -1;
 332
 333         return 0;
 334 }
 335
 336 void mount_list_init(void) {
 337         avl_init(&mounts, avl_strcmp, false, NULL);
 338 }
 339
 340 static int add_script_interp(const char *path, const char *map, int size)
 341 {
 342         int start = 2;
 343         while (start < size && map[start] != '/') {
 344                 start++;
 345         }
 346         if (start >= size) {
 347                 ERROR("bad script interp (%s)\n", path);
 348                 return -1;
 349         }
 350         int stop = start + 1;
 351         while (stop < size && map[stop] > 0x20 && map[stop] <= 0x7e) {
 352                 stop++;
 353         }
 354         if (stop >= size || (stop-start) > PATH_MAX) {
 355                 ERROR("bad script interp (%s)\n", path);
 356                 return -1;
 357         }
 358         char buf[PATH_MAX];
 359         strncpy(buf, map+start, stop-start);
 360         return add_path_and_deps(buf, 1, -1, 0);
 361 }
 362
 363 int add_path_and_deps(const char *path, int readonly, int error, int lib)
 364 {
 365         assert(path != NULL);
 366
 367         if (lib == 0 && path[0] != '/') {
 368                 ERROR("%s is not an absolute path\n", path);
 369                 return error;
 370         }
 371
 372         char *map = NULL;
 373         int fd, ret = -1;
 374         if (path[0] == '/') {
 375                 if (avl_find(&mounts, path))
 376                         return 0;
 377                 fd = open(path, O_RDONLY|O_CLOEXEC);
 378                 if (fd == -1)
 379                         return error;
 380                 add_mount_bind(path, readonly, error);
 381         } else {
 382                 if (avl_find(&libraries, path))
 383                         return 0;
 384                 char *fullpath;
 385                 fd = lib_open(&fullpath, path);
 386                 if (fd == -1)
 387                         return error;
 388                 if (fullpath) {
 389                         alloc_library(fullpath, path);
 390                         free(fullpath);
 391                 }
 392         }
 393
 394         struct stat s;
 395         if (fstat(fd, &s) == -1) {
 396                 ERROR("fstat(%s) failed: %m\n", path);
 397                 ret = error;
 398                 goto out;
 399         }
 400
 401         if (!S_ISREG(s.st_mode)) {
 402                 ret = 0;
 403                 goto out;
 404         }
 405
 406         /* too small to be an ELF or a script -> "normal" file */
 407         if (s.st_size < 4) {
 408                 ret = 0;
 409                 goto out;
 410         }
 411
 412         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 413         if (map == MAP_FAILED) {
 414                 ERROR("failed to mmap %s: %m\n", path);
 415                 ret = -1;
 416                 goto out;
 417         }
 418
 419         if (map[0] == '#' && map[1] == '!') {
 420                 ret = add_script_interp(path, map, s.st_size);
 421                 goto out;
 422         }
 423
 424         if (map[0] == ELFMAG0 && map[1] == ELFMAG1 && map[2] == ELFMAG2 && map[3] == ELFMAG3) {
 425                 ret = elf_load_deps(path, map);
 426                 goto out;
 427         }
 428
 429         ret = 0;
 430
 431 out:
 432         if (fd >= 0)
 433                 close(fd);
 434         if (map)
 435                 munmap(map, s.st_size);
 436
 437         return ret;
 438 }