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 #define UJAIL_NOAFILE "/tmp/.ujailnoafile"
  41
  42 struct mount {
  43         struct avl_node avl;
  44         const char *source;
  45         const char *target;
  46         const char *filesystemtype;
  47         unsigned long mountflags;
  48         const char *optstr;
  49         int error;
  50 };
  51
  52 struct avl_tree mounts;
  53
  54 int mkdir_p(char *dir, mode_t mask)
  55 {
  56         char *l = strrchr(dir, '/');
  57         int ret;
  58
  59         if (!l)
  60                 return 0;
  61
  62         *l = '\0';
  63
  64         if (mkdir_p(dir, mask))
  65                 return -1;
  66
  67         *l = '/';
  68
  69         ret = mkdir(dir, mask);
  70         if (ret && errno == EEXIST)
  71                 return 0;
  72
  73         if (ret)
  74                 ERROR("mkdir(%s, %d) failed: %m\n", dir, mask);
  75
  76         return ret;
  77 }
  78
  79 static int do_mount(const char *root, const char *source, const char *target, const char *filesystemtype,
  80                     unsigned long orig_mountflags, const char *optstr, int error)
  81 {
  82         struct stat s;
  83         char new[PATH_MAX];
  84         int fd;
  85         bool is_bind = (orig_mountflags & MS_BIND);
  86         bool is_mask = (source == (void *)(-1));
  87         unsigned long mountflags = orig_mountflags;
  88
  89         if (source && is_bind && stat(source, &s)) {
  90                 ERROR("stat(%s) failed: %m\n", source);
  91                 return error;
  92         }
  93
  94         snprintf(new, sizeof(new), "%s%s", root, target?target:source);
  95
  96         if (is_mask) {
  97                 if (stat(new, &s))
  98                         return 0; /* doesn't exists, nothing to mask */
  99
 100                 if (S_ISDIR(s.st_mode)) {/* use empty 0-sized tmpfs for directories */
 101                         if (mount(NULL, new, "tmpfs", MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, "size=0,mode=000"))
 102                                 return error;
 103                 } else {
 104                         /* mount-bind 0-sized file having mode 000 */
 105                         if (mount(UJAIL_NOAFILE, new, NULL, MS_BIND, NULL))
 106                                 return error;
 107
 108                         if (mount(UJAIL_NOAFILE, new, NULL, MS_REMOUNT | MS_BIND | MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, NULL))
 109                                 return error;
 110                 }
 111
 112                 DEBUG("masked path %s\n", new);
 113                 return 0;
 114         }
 115
 116
 117         if (!is_bind || (source && S_ISDIR(s.st_mode))) {
 118                 mkdir_p(new, 0755);
 119         } else if (is_bind && source) {
 120                 mkdir_p(dirname(new), 0755);
 121                 snprintf(new, sizeof(new), "%s%s", root, target?target:source);
 122                 fd = creat(new, 0644);
 123                 if (fd == -1) {
 124                         ERROR("creat(%s) failed: %m\n", new);
 125                         return error;
 126                 }
 127                 close(fd);
 128         }
 129
 130         if (is_bind) {
 131                 if (mount(source?:new, new, filesystemtype, MS_BIND | (mountflags & MS_REC), optstr)) {
 132                         if (error)
 133                                 ERROR("failed to mount -B %s %s: %m\n", source, new);
 134
 135                         return error;
 136                 }
 137                 mountflags |= MS_REMOUNT;
 138         }
 139
 140         if (mount(source?:(is_bind?new:NULL), new, filesystemtype, mountflags, optstr)) {
 141                 if (error)
 142                         ERROR("failed to mount %s %s: %m\n", source, new);
 143
 144                 return error;
 145         }
 146
 147         DEBUG("mount %s%s %s (%s)\n", (mountflags & MS_BIND)?"-B ":"", source, new,
 148               (mountflags & MS_RDONLY)?"ro":"rw");
 149
 150         return 0;
 151 }
 152
 153 int add_mount(const char *source, const char *target, const char *filesystemtype,
 154               unsigned long mountflags, const char *optstr, int error)
 155 {
 156         assert(target != NULL);
 157
 158         if (avl_find(&mounts, target))
 159                 return 1;
 160
 161         struct mount *m;
 162         m = calloc(1, sizeof(struct mount));
 163         assert(m != NULL);
 164         m->avl.key = m->target = strdup(target);
 165         if (source) {
 166                 if (source != (void*)(-1))
 167                         m->source = strdup(source);
 168                 else
 169                         m->source = (void*)(-1);
 170         }
 171         if (filesystemtype)
 172                 m->filesystemtype = strdup(filesystemtype);
 173         m->mountflags = mountflags;
 174         m->error = error;
 175
 176         avl_insert(&mounts, &m->avl);
 177         DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", (m->source == (void*)(-1))?"mask":m->source, m->target,
 178                 !!(m->mountflags & MS_BIND), !!(m->mountflags & MS_RDONLY), m->error != 0);
 179
 180         return 0;
 181 }
 182
 183 int add_mount_bind(const char *path, int readonly, int error)
 184 {
 185         unsigned long mountflags = MS_BIND;
 186
 187         if (readonly)
 188                 mountflags |= MS_RDONLY;
 189
 190         return add_mount(path, path, NULL, mountflags, NULL, error);
 191 }
 192
 193 enum {
 194         OCI_MOUNT_SOURCE,
 195         OCI_MOUNT_DESTINATION,
 196         OCI_MOUNT_TYPE,
 197         OCI_MOUNT_OPTIONS,
 198         __OCI_MOUNT_MAX,
 199 };
 200
 201 static const struct blobmsg_policy oci_mount_policy[] = {
 202         [OCI_MOUNT_SOURCE] = { "source", BLOBMSG_TYPE_STRING },
 203         [OCI_MOUNT_DESTINATION] = { "destination", BLOBMSG_TYPE_STRING },
 204         [OCI_MOUNT_TYPE] = { "type", BLOBMSG_TYPE_STRING },
 205         [OCI_MOUNT_OPTIONS] = { "options", BLOBMSG_TYPE_ARRAY },
 206 };
 207
 208 struct mount_opt {
 209         struct list_head list;
 210         char *optstr;
 211 };
 212
 213 #ifndef MS_LAZYTIME
 214 #define MS_LAZYTIME (1 << 25)
 215 #endif
 216
 217 static int parseOCImountopts(struct blob_attr *msg, unsigned long *mount_flags, char **mount_data, int *error)
 218 {
 219         struct blob_attr *cur;
 220         int rem;
 221         unsigned long mf = 0;
 222         char *tmp;
 223         struct list_head fsopts = LIST_HEAD_INIT(fsopts);
 224         size_t len = 0;
 225         struct mount_opt *opt;
 226
 227         blobmsg_for_each_attr(cur, msg, rem) {
 228                 tmp = blobmsg_get_string(cur);
 229                 if (!strcmp("ro", tmp))
 230                         mf |= MS_RDONLY;
 231                 else if (!strcmp("rw", tmp))
 232                         mf &= ~MS_RDONLY;
 233                 else if (!strcmp("bind", tmp))
 234                         mf = MS_BIND;
 235                 else if (!strcmp("rbind", tmp))
 236                         mf |= MS_BIND | MS_REC;
 237                 else if (!strcmp("sync", tmp))
 238                         mf |= MS_SYNCHRONOUS;
 239                 else if (!strcmp("async", tmp))
 240                         mf &= ~MS_SYNCHRONOUS;
 241                 else if (!strcmp("atime", tmp))
 242                         mf &= ~MS_NOATIME;
 243                 else if (!strcmp("noatime", tmp))
 244                         mf |= MS_NOATIME;
 245                 else if (!strcmp("defaults", tmp))
 246                         mf = 0; /* rw, suid, dev, exec, auto, nouser, and async */
 247                 else if (!strcmp("dev", tmp))
 248                         mf &= ~MS_NODEV;
 249                 else if (!strcmp("nodev", tmp))
 250                         mf |= MS_NODEV;
 251                 else if (!strcmp("iversion", tmp))
 252                         mf |= MS_I_VERSION;
 253                 else if (!strcmp("noiversion", tmp))
 254                         mf &= ~MS_I_VERSION;
 255                 else if (!strcmp("diratime", tmp))
 256                         mf &= ~MS_NODIRATIME;
 257                 else if (!strcmp("nodiratime", tmp))
 258                         mf |= MS_NODIRATIME;
 259                 else if (!strcmp("dirsync", tmp))
 260                         mf |= MS_DIRSYNC;
 261                 else if (!strcmp("exec", tmp))
 262                         mf &= ~MS_NOEXEC;
 263                 else if (!strcmp("noexec", tmp))
 264                         mf |= MS_NOEXEC;
 265                 else if (!strcmp("mand", tmp))
 266                         mf |= MS_MANDLOCK;
 267                 else if (!strcmp("nomand", tmp))
 268                         mf &= ~MS_MANDLOCK;
 269                 else if (!strcmp("relatime", tmp))
 270                         mf |= MS_RELATIME;
 271                 else if (!strcmp("norelatime", tmp))
 272                         mf &= ~MS_RELATIME;
 273                 else if (!strcmp("strictatime", tmp))
 274                         mf |= MS_STRICTATIME;
 275                 else if (!strcmp("nostrictatime", tmp))
 276                         mf &= ~MS_STRICTATIME;
 277                 else if (!strcmp("lazytime", tmp))
 278                         mf |= MS_LAZYTIME;
 279                 else if (!strcmp("nolazytime", tmp))
 280                         mf &= ~MS_LAZYTIME;
 281                 else if (!strcmp("suid", tmp))
 282                         mf &= ~MS_NOSUID;
 283                 else if (!strcmp("nosuid", tmp))
 284                         mf |= MS_NOSUID;
 285                 else if (!strcmp("remount", tmp))
 286                         mf |= MS_REMOUNT;
 287                 else if(!strcmp("nofail", tmp))
 288                         *error = 0;
 289                 else if (!strcmp("auto", tmp) ||
 290                          !strcmp("noauto", tmp) ||
 291                          !strcmp("user", tmp) ||
 292                          !strcmp("group", tmp) ||
 293                          !strcmp("_netdev", tmp))
 294                         DEBUG("ignoring built-in mount option %s\n", tmp);
 295                 else {
 296                         /* filesystem-specific free-form option */
 297                         opt = calloc(1, sizeof(*opt));
 298                         opt->optstr = tmp;
 299                         list_add_tail(&opt->list, &fsopts);
 300                 }
 301         };
 302
 303         *mount_flags = mf;
 304
 305         list_for_each_entry(opt, &fsopts, list) {
 306                 if (len)
 307                         ++len;
 308
 309                 len += strlen(opt->optstr);
 310         };
 311
 312         if (!len)
 313                 return 0;
 314
 315         *mount_data = calloc(len + 1, sizeof(char));
 316         if (!mount_data)
 317                 return ENOMEM;
 318
 319         len = 0;
 320         list_for_each_entry(opt, &fsopts, list) {
 321                 if (len)
 322                         strcat(*mount_data, ",");
 323
 324                 strcat(*mount_data, opt->optstr);
 325                 ++len;
 326         };
 327
 328         list_del(&fsopts);
 329
 330         DEBUG("mount flags(%08lx) fsopts(\"%s\")\n", mf, *mount_data?:"");
 331
 332         return 0;
 333 }
 334
 335 int parseOCImount(struct blob_attr *msg)
 336 {
 337         struct blob_attr *tb[__OCI_MOUNT_MAX];
 338         unsigned long mount_flags = 0;
 339         char *mount_data = NULL;
 340         int ret, err = -1;
 341
 342         blobmsg_parse(oci_mount_policy, __OCI_MOUNT_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 343
 344         if (!tb[OCI_MOUNT_DESTINATION])
 345                 return EINVAL;
 346
 347         if (tb[OCI_MOUNT_OPTIONS]) {
 348                 ret = parseOCImountopts(tb[OCI_MOUNT_OPTIONS], &mount_flags, &mount_data, &err);
 349                 if (ret)
 350                         return ret;
 351         }
 352
 353         return add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL,
 354                   blobmsg_get_string(tb[OCI_MOUNT_DESTINATION]),
 355                   tb[OCI_MOUNT_TYPE] ? blobmsg_get_string(tb[OCI_MOUNT_TYPE]) : NULL,
 356                   mount_flags, mount_data, err);
 357 }
 358
 359 static void build_noafile(void) {
 360         int fd;
 361
 362         fd = creat(UJAIL_NOAFILE, 0000);
 363         if (fd == -1)
 364                 return;
 365
 366         close(fd);
 367         return;
 368 }
 369
 370 int mount_all(const char *jailroot) {
 371         struct library *l;
 372         struct mount *m;
 373
 374         build_noafile();
 375
 376         avl_for_each_element(&libraries, l, avl)
 377                 add_mount_bind(l->path, 1, -1);
 378
 379         avl_for_each_element(&mounts, m, avl)
 380                 if (do_mount(jailroot, m->source, m->target, m->filesystemtype, m->mountflags, m->optstr, m->error))
 381                         return -1;
 382
 383         return 0;
 384 }
 385
 386 void mount_list_init(void) {
 387         avl_init(&mounts, avl_strcmp, false, NULL);
 388 }
 389
 390 static int add_script_interp(const char *path, const char *map, int size)
 391 {
 392         int start = 2;
 393         while (start < size && map[start] != '/') {
 394                 start++;
 395         }
 396         if (start >= size) {
 397                 ERROR("bad script interp (%s)\n", path);
 398                 return -1;
 399         }
 400         int stop = start + 1;
 401         while (stop < size && map[stop] > 0x20 && map[stop] <= 0x7e) {
 402                 stop++;
 403         }
 404         if (stop >= size || (stop-start) > PATH_MAX) {
 405                 ERROR("bad script interp (%s)\n", path);
 406                 return -1;
 407         }
 408         char buf[PATH_MAX];
 409         strncpy(buf, map+start, stop-start);
 410         return add_path_and_deps(buf, 1, -1, 0);
 411 }
 412
 413 int add_path_and_deps(const char *path, int readonly, int error, int lib)
 414 {
 415         assert(path != NULL);
 416
 417         if (lib == 0 && path[0] != '/') {
 418                 ERROR("%s is not an absolute path\n", path);
 419                 return error;
 420         }
 421
 422         char *map = NULL;
 423         int fd, ret = -1;
 424         if (path[0] == '/') {
 425                 if (avl_find(&mounts, path))
 426                         return 0;
 427                 fd = open(path, O_RDONLY|O_CLOEXEC);
 428                 if (fd == -1)
 429                         return error;
 430                 add_mount_bind(path, readonly, error);
 431         } else {
 432                 if (avl_find(&libraries, path))
 433                         return 0;
 434                 char *fullpath;
 435                 fd = lib_open(&fullpath, path);
 436                 if (fd == -1)
 437                         return error;
 438                 if (fullpath) {
 439                         alloc_library(fullpath, path);
 440                         free(fullpath);
 441                 }
 442         }
 443
 444         struct stat s;
 445         if (fstat(fd, &s) == -1) {
 446                 ERROR("fstat(%s) failed: %m\n", path);
 447                 ret = error;
 448                 goto out;
 449         }
 450
 451         if (!S_ISREG(s.st_mode)) {
 452                 ret = 0;
 453                 goto out;
 454         }
 455
 456         /* too small to be an ELF or a script -> "normal" file */
 457         if (s.st_size < 4) {
 458                 ret = 0;
 459                 goto out;
 460         }
 461
 462         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 463         if (map == MAP_FAILED) {
 464                 ERROR("failed to mmap %s: %m\n", path);
 465                 ret = -1;
 466                 goto out;
 467         }
 468
 469         if (map[0] == '#' && map[1] == '!') {
 470                 ret = add_script_interp(path, map, s.st_size);
 471                 goto out;
 472         }
 473
 474         if (map[0] == ELFMAG0 && map[1] == ELFMAG1 && map[2] == ELFMAG2 && map[3] == ELFMAG3) {
 475                 ret = elf_load_deps(path, map);
 476                 goto out;
 477         }
 478
 479         ret = 0;
 480
 481 out:
 482         if (fd >= 0)
 483                 close(fd);
 484         if (map)
 485                 munmap(map, s.st_size);
 486
 487         return ret;
 488 }