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 error;
 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                         return error;
 110                 }
 111                 mountflags |= MS_REMOUNT;
 112         }
 113
 114         if (mount(source, new, filesystemtype, mountflags, optstr)) {
 115                 ERROR("failed to mount %s %s: %m\n", source, new);
 116                 return error;
 117         }
 118
 119         DEBUG("mount %s%s %s (%s)\n", (mountflags & MS_BIND)?"-B ":"", source, new,
 120               (mountflags & MS_RDONLY)?"ro":"rw");
 121
 122         return 0;
 123 }
 124
 125 int add_mount(const char *source, const char *target, const char *filesystemtype,
 126               unsigned long mountflags, const char *optstr, int error)
 127 {
 128         assert(target != NULL);
 129
 130         if (avl_find(&mounts, target))
 131                 return 1;
 132
 133         struct mount *m;
 134         m = calloc(1, sizeof(struct mount));
 135         assert(m != NULL);
 136         m->avl.key = m->target = strdup(target);
 137         if (source)
 138                 m->source = strdup(source);
 139         if (filesystemtype)
 140                 m->filesystemtype = strdup(filesystemtype);
 141         m->mountflags = mountflags;
 142         m->error = error;
 143
 144         avl_insert(&mounts, &m->avl);
 145         DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", m->source, m->target,
 146                 !!(m->mountflags & MS_BIND), !!(m->mountflags & MS_RDONLY), m->error != 0);
 147
 148         return 0;
 149 }
 150
 151 int add_mount_bind(const char *path, int readonly, int error)
 152 {
 153         unsigned long mountflags = MS_BIND;
 154
 155         if (readonly)
 156                 mountflags |= MS_RDONLY;
 157
 158         return add_mount(path, path, NULL, mountflags, NULL, error);
 159 }
 160
 161
 162 enum {
 163         OCI_MOUNT_SOURCE,
 164         OCI_MOUNT_DESTINATION,
 165         OCI_MOUNT_TYPE,
 166         OCI_MOUNT_OPTIONS,
 167         __OCI_MOUNT_MAX,
 168 };
 169
 170 static const struct blobmsg_policy oci_mount_policy[] = {
 171         [OCI_MOUNT_SOURCE] = { "source", BLOBMSG_TYPE_STRING },
 172         [OCI_MOUNT_DESTINATION] = { "destination", BLOBMSG_TYPE_STRING },
 173         [OCI_MOUNT_TYPE] = { "type", BLOBMSG_TYPE_STRING },
 174         [OCI_MOUNT_OPTIONS] = { "options", BLOBMSG_TYPE_ARRAY },
 175 };
 176
 177 struct mount_opt {
 178         struct list_head list;
 179         char *optstr;
 180 };
 181
 182 #ifndef MS_LAZYTIME
 183 #define MS_LAZYTIME (1 << 25)
 184 #endif
 185
 186 static int parseOCImountopts(struct blob_attr *msg, unsigned long *mount_flags, char **mount_data, int *error)
 187 {
 188         struct blob_attr *cur;
 189         int rem;
 190         unsigned long mf = 0;
 191         char *tmp;
 192         struct list_head fsopts = LIST_HEAD_INIT(fsopts);
 193         size_t len = 0;
 194         struct mount_opt *opt;
 195
 196         blobmsg_for_each_attr(cur, msg, rem) {
 197                 tmp = blobmsg_get_string(cur);
 198                 if (!strcmp("ro", tmp))
 199                         mf |= MS_RDONLY;
 200                 else if (!strcmp("rw", tmp))
 201                         mf &= ~MS_RDONLY;
 202                 else if (!strcmp("bind", tmp))
 203                         mf = MS_BIND;
 204                 else if (!strcmp("rbind", tmp))
 205                         mf |= MS_BIND | MS_REC;
 206                 else if (!strcmp("sync", tmp))
 207                         mf |= MS_SYNCHRONOUS;
 208                 else if (!strcmp("async", tmp))
 209                         mf &= ~MS_SYNCHRONOUS;
 210                 else if (!strcmp("atime", tmp))
 211                         mf &= ~MS_NOATIME;
 212                 else if (!strcmp("noatime", tmp))
 213                         mf |= MS_NOATIME;
 214                 else if (!strcmp("defaults", tmp))
 215                         mf = 0; /* rw, suid, dev, exec, auto, nouser, and async */
 216                 else if (!strcmp("dev", tmp))
 217                         mf &= ~MS_NODEV;
 218                 else if (!strcmp("nodev", tmp))
 219                         mf |= MS_NODEV;
 220                 else if (!strcmp("diratime", tmp))
 221                         mf &= ~MS_NODIRATIME;
 222                 else if (!strcmp("nodiratime", tmp))
 223                         mf |= MS_NODIRATIME;
 224                 else if (!strcmp("dirsync", tmp))
 225                         mf |= MS_DIRSYNC;
 226                 else if (!strcmp("exec", tmp))
 227                         mf &= ~MS_NOEXEC;
 228                 else if (!strcmp("noexec", tmp))
 229                         mf |= MS_NOEXEC;
 230                 else if (!strcmp("mand", tmp))
 231                         mf |= MS_MANDLOCK;
 232                 else if (!strcmp("nomand", tmp))
 233                         mf &= ~MS_MANDLOCK;
 234                 else if (!strcmp("relatime", tmp))
 235                         mf |= MS_RELATIME;
 236                 else if (!strcmp("norelatime", tmp))
 237                         mf &= ~MS_RELATIME;
 238                 else if (!strcmp("strictatime", tmp))
 239                         mf |= MS_STRICTATIME;
 240                 else if (!strcmp("nostrictatime", tmp))
 241                         mf &= ~MS_STRICTATIME;
 242                 else if (!strcmp("lazytime", tmp))
 243                         mf |= MS_LAZYTIME;
 244                 else if (!strcmp("nolazytime", tmp))
 245                         mf &= ~MS_LAZYTIME;
 246                 else if (!strcmp("suid", tmp))
 247                         mf &= ~MS_NOSUID;
 248                 else if (!strcmp("nosuid", tmp))
 249                         mf |= MS_NOSUID;
 250                 else if (!strcmp("remount", tmp))
 251                         mf |= MS_REMOUNT;
 252                 else if(!strcmp("nofail", tmp))
 253                         *error = 0;
 254                 else if (!strcmp("auto", tmp) ||
 255                          !strcmp("noauto", tmp) ||
 256                          !strcmp("user", tmp) ||
 257                          !strcmp("group", tmp) ||
 258                          !strcmp("_netdev", tmp))
 259                         DEBUG("ignoring built-in mount option %s\n", tmp);
 260                 else {
 261                         /* filesystem-specific free-form option */
 262                         opt = calloc(1, sizeof(*opt));
 263                         opt->optstr = tmp;
 264                         list_add_tail(&opt->list, &fsopts);
 265                 }
 266         };
 267
 268         *mount_flags = mf;
 269
 270         list_for_each_entry(opt, &fsopts, list) {
 271                 if (len)
 272                         ++len;
 273
 274                 len += strlen(opt->optstr);
 275         };
 276
 277         if (!len)
 278                 return 0;
 279
 280         *mount_data = calloc(len + 1, sizeof(char));
 281         if (!mount_data)
 282                 return ENOMEM;
 283
 284         len = 0;
 285         list_for_each_entry(opt, &fsopts, list) {
 286                 if (len)
 287                         strcat(*mount_data, ",");
 288
 289                 strcat(*mount_data, opt->optstr);
 290                 ++len;
 291         };
 292
 293         list_del(&fsopts);
 294
 295         DEBUG("mount flags(%08lx) fsopts(\"%s\")\n", mf, *mount_data?:"");
 296
 297         return 0;
 298 };
 299
 300 int parseOCImount(struct blob_attr *msg)
 301 {
 302         struct blob_attr *tb[__OCI_MOUNT_MAX];
 303         unsigned long mount_flags = 0;
 304         char *mount_data = NULL;
 305         int ret, err = -1;
 306
 307         blobmsg_parse(oci_mount_policy, __OCI_MOUNT_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 308
 309         if (!tb[OCI_MOUNT_DESTINATION])
 310                 return EINVAL;
 311
 312         if (tb[OCI_MOUNT_OPTIONS]) {
 313                 ret = parseOCImountopts(tb[OCI_MOUNT_OPTIONS], &mount_flags, &mount_data, &err);
 314                 if (ret)
 315                         return ret;
 316         }
 317
 318         add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL,
 319                   blobmsg_get_string(tb[OCI_MOUNT_DESTINATION]),
 320                   tb[OCI_MOUNT_TYPE] ? blobmsg_get_string(tb[OCI_MOUNT_TYPE]) : NULL,
 321                   mount_flags, mount_data, err);
 322
 323         return 0;
 324 };
 325
 326
 327 int mount_all(const char *jailroot) {
 328         struct library *l;
 329         struct mount *m;
 330
 331         avl_for_each_element(&libraries, l, avl)
 332                 add_mount_bind(l->path, 1, -1);
 333
 334         avl_for_each_element(&mounts, m, avl)
 335                 if (do_mount(jailroot, m->source, m->target, m->filesystemtype, m->mountflags, m->optstr, m->error))
 336                         return -1;
 337
 338         return 0;
 339 }
 340
 341 void mount_list_init(void) {
 342         avl_init(&mounts, avl_strcmp, false, NULL);
 343 }
 344
 345 static int add_script_interp(const char *path, const char *map, int size)
 346 {
 347         int start = 2;
 348         while (start < size && map[start] != '/') {
 349                 start++;
 350         }
 351         if (start >= size) {
 352                 ERROR("bad script interp (%s)\n", path);
 353                 return -1;
 354         }
 355         int stop = start + 1;
 356         while (stop < size && map[stop] > 0x20 && map[stop] <= 0x7e) {
 357                 stop++;
 358         }
 359         if (stop >= size || (stop-start) > PATH_MAX) {
 360                 ERROR("bad script interp (%s)\n", path);
 361                 return -1;
 362         }
 363         char buf[PATH_MAX];
 364         strncpy(buf, map+start, stop-start);
 365         return add_path_and_deps(buf, 1, -1, 0);
 366 }
 367
 368 int add_path_and_deps(const char *path, int readonly, int error, int lib)
 369 {
 370         assert(path != NULL);
 371
 372         if (lib == 0 && path[0] != '/') {
 373                 ERROR("%s is not an absolute path\n", path);
 374                 return error;
 375         }
 376
 377         char *map = NULL;
 378         int fd, ret = -1;
 379         if (path[0] == '/') {
 380                 if (avl_find(&mounts, path))
 381                         return 0;
 382                 fd = open(path, O_RDONLY|O_CLOEXEC);
 383                 if (fd == -1)
 384                         return error;
 385                 add_mount_bind(path, readonly, error);
 386         } else {
 387                 if (avl_find(&libraries, path))
 388                         return 0;
 389                 char *fullpath;
 390                 fd = lib_open(&fullpath, path);
 391                 if (fd == -1)
 392                         return error;
 393                 if (fullpath) {
 394                         alloc_library(fullpath, path);
 395                         free(fullpath);
 396                 }
 397         }
 398
 399         struct stat s;
 400         if (fstat(fd, &s) == -1) {
 401                 ERROR("fstat(%s) failed: %m\n", path);
 402                 ret = error;
 403                 goto out;
 404         }
 405
 406         if (!S_ISREG(s.st_mode)) {
 407                 ret = 0;
 408                 goto out;
 409         }
 410
 411         /* too small to be an ELF or a script -> "normal" file */
 412         if (s.st_size < 4) {
 413                 ret = 0;
 414                 goto out;
 415         }
 416
 417         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 418         if (map == MAP_FAILED) {
 419                 ERROR("failed to mmap %s: %m\n", path);
 420                 ret = -1;
 421                 goto out;
 422         }
 423
 424         if (map[0] == '#' && map[1] == '!') {
 425                 ret = add_script_interp(path, map, s.st_size);
 426                 goto out;
 427         }
 428
 429         if (map[0] == ELFMAG0 && map[1] == ELFMAG1 && map[2] == ELFMAG2 && map[3] == ELFMAG3) {
 430                 ret = elf_load_deps(path, map);
 431                 goto out;
 432         }
 433
 434         ret = 0;
 435
 436 out:
 437         if (fd >= 0)
 438                 close(fd);
 439         if (map)
 440                 munmap(map, s.st_size);
 441
 442         return ret;
 443 }