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 <stdio.h>
  25 #include <string.h>
  26 #include <sys/stat.h>
  27 #include <sys/mman.h>
  28 #include <unistd.h>
  29 #include <libgen.h>
  30
  31 #include <libubox/avl.h>
  32 #include <libubox/avl-cmp.h>
  33 #include <libubox/blobmsg.h>
  34 #include <libubox/list.h>
  35
  36 #include "elf.h"
  37 #include "fs.h"
  38 #include "jail.h"
  39 #include "log.h"
  40
  41 #define UJAIL_NOAFILE "/tmp/.ujailnoafile"
  42
  43 struct mount {
  44         struct avl_node avl;
  45         const char *source;
  46         const char *target;
  47         const char *filesystemtype;
  48         unsigned long mountflags;
  49         unsigned long propflags;
  50         const char *optstr;
  51         int error;
  52         bool inner;
  53 };
  54
  55 struct avl_tree mounts;
  56
  57 int mkdir_p(char *dir, mode_t mask)
  58 {
  59         char *l = strrchr(dir, '/');
  60         int ret;
  61
  62         if (!l)
  63                 return 0;
  64
  65         *l = '\0';
  66
  67         if (mkdir_p(dir, mask))
  68                 return -1;
  69
  70         *l = '/';
  71
  72         ret = mkdir(dir, mask);
  73         if (ret && errno == EEXIST)
  74                 return 0;
  75
  76         if (ret)
  77                 ERROR("mkdir(%s, %d) failed: %m\n", dir, mask);
  78
  79         return ret;
  80 }
  81
  82 static int do_mount(const char *root, const char *orig_source, const char *target, const char *filesystemtype,
  83                     unsigned long orig_mountflags, unsigned long propflags, const char *optstr, int error, bool inner)
  84 {
  85         struct stat s;
  86         char new[PATH_MAX];
  87         char *source = (char *)orig_source;
  88         int fd;
  89         bool is_bind = (orig_mountflags & MS_BIND);
  90         bool is_mask = (source == (void *)(-1));
  91         unsigned long mountflags = orig_mountflags;
  92
  93         if (source && is_bind && stat(source, &s)) {
  94                 ERROR("stat(%s) failed: %m\n", source);
  95                 return error;
  96         }
  97
  98         if (!is_mask && orig_source && inner) {
  99                 if (asprintf(&source, "%s%s", root, orig_source) < 0)
 100                         return ENOMEM;
 101         }
 102
 103         snprintf(new, sizeof(new), "%s%s", root, target?target:source);
 104
 105         if (is_mask) {
 106                 if (stat(new, &s))
 107                         return 0; /* doesn't exists, nothing to mask */
 108
 109                 if (S_ISDIR(s.st_mode)) {/* use empty 0-sized tmpfs for directories */
 110                         if (mount(NULL, new, "tmpfs", MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, "size=0,mode=000"))
 111                                 return error;
 112                 } else {
 113                         /* mount-bind 0-sized file having mode 000 */
 114                         if (mount(UJAIL_NOAFILE, new, NULL, MS_BIND, NULL))
 115                                 return error;
 116
 117                         if (mount(UJAIL_NOAFILE, new, NULL, MS_REMOUNT | MS_BIND | MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, NULL))
 118                                 return error;
 119                 }
 120
 121                 DEBUG("masked path %s\n", new);
 122                 return 0;
 123         }
 124
 125
 126         if (!is_bind || (source && S_ISDIR(s.st_mode))) {
 127                 mkdir_p(new, 0755);
 128         } else if (is_bind && source) {
 129                 mkdir_p(dirname(new), 0755);
 130                 snprintf(new, sizeof(new), "%s%s", root, target?target:source);
 131                 fd = creat(new, 0644);
 132                 if (fd == -1) {
 133                         ERROR("creat(%s) failed: %m\n", new);
 134                         return error;
 135                 }
 136                 close(fd);
 137         }
 138
 139         if (is_bind) {
 140                 if (mount(source?:new, new, filesystemtype, MS_BIND | (mountflags & MS_REC), optstr)) {
 141                         if (error)
 142                                 ERROR("failed to mount -B %s %s: %m\n", source, new);
 143
 144                         if (inner)
 145                                 free(source);
 146
 147                         return error;
 148                 }
 149                 mountflags |= MS_REMOUNT;
 150         }
 151
 152         if (mount(source?:(is_bind?new:NULL), new, filesystemtype, mountflags, optstr)) {
 153                 if (error)
 154                         ERROR("failed to mount %s %s: %m\n", source, new);
 155
 156                 if (inner)
 157                         free(source);
 158
 159                 return error;
 160         }
 161
 162         DEBUG("mount %s%s %s (%s)\n", (mountflags & MS_BIND)?"-B ":"", source, new,
 163               (mountflags & MS_RDONLY)?"ro":"rw");
 164
 165         if (propflags && mount(NULL, new, NULL, propflags, NULL)) {
 166                 if (error)
 167                         ERROR("failed to mount --make-... %s \n", new);
 168
 169                 if (inner)
 170                         free(source);
 171
 172                 return error;
 173         }
 174
 175         if (inner)
 176                 free(source);
 177
 178         return 0;
 179 }
 180
 181 static int _add_mount(const char *source, const char *target, const char *filesystemtype,
 182                       unsigned long mountflags, unsigned long propflags, const char *optstr,
 183                       int error, bool inner)
 184 {
 185         assert(target != NULL);
 186
 187         if (avl_find(&mounts, target))
 188                 return 1;
 189
 190         struct mount *m;
 191         m = calloc(1, sizeof(struct mount));
 192         assert(m != NULL);
 193         m->avl.key = m->target = strdup(target);
 194         if (source) {
 195                 if (source != (void*)(-1))
 196                         m->source = strdup(source);
 197                 else
 198                         m->source = (void*)(-1);
 199         }
 200         if (filesystemtype)
 201                 m->filesystemtype = strdup(filesystemtype);
 202
 203         if (optstr)
 204                 m->optstr = strdup(optstr);
 205
 206         m->mountflags = mountflags;
 207         m->propflags = propflags;
 208         m->error = error;
 209         m->inner = inner;
 210
 211         avl_insert(&mounts, &m->avl);
 212         DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", (m->source == (void*)(-1))?"mask":m->source, m->target,
 213                 !!(m->mountflags & MS_BIND), !!(m->mountflags & MS_RDONLY), m->error != 0);
 214
 215         return 0;
 216 }
 217
 218 int add_mount(const char *source, const char *target, const char *filesystemtype,
 219               unsigned long mountflags, unsigned long propflags, const char *optstr, int error)
 220 {
 221         return _add_mount(source, target, filesystemtype, mountflags, propflags, optstr, error, false);
 222 }
 223
 224 int add_mount_inner(const char *source, const char *target, const char *filesystemtype,
 225               unsigned long mountflags, unsigned long propflags, const char *optstr, int error)
 226 {
 227         return _add_mount(source, target, filesystemtype, mountflags, propflags, optstr, error, true);
 228 }
 229
 230 int add_mount_bind(const char *path, int readonly, int error)
 231 {
 232         unsigned long mountflags = MS_BIND;
 233
 234         if (readonly)
 235                 mountflags |= MS_RDONLY;
 236
 237         return add_mount(path, path, NULL, mountflags, 0, NULL, error);
 238 }
 239
 240 enum {
 241         OCI_MOUNT_SOURCE,
 242         OCI_MOUNT_DESTINATION,
 243         OCI_MOUNT_TYPE,
 244         OCI_MOUNT_OPTIONS,
 245         __OCI_MOUNT_MAX,
 246 };
 247
 248 static const struct blobmsg_policy oci_mount_policy[] = {
 249         [OCI_MOUNT_SOURCE] = { "source", BLOBMSG_TYPE_STRING },
 250         [OCI_MOUNT_DESTINATION] = { "destination", BLOBMSG_TYPE_STRING },
 251         [OCI_MOUNT_TYPE] = { "type", BLOBMSG_TYPE_STRING },
 252         [OCI_MOUNT_OPTIONS] = { "options", BLOBMSG_TYPE_ARRAY },
 253 };
 254
 255 struct mount_opt {
 256         struct list_head list;
 257         char *optstr;
 258 };
 259
 260 #ifndef MS_LAZYTIME
 261 #define MS_LAZYTIME (1 << 25)
 262 #endif
 263
 264 static int parseOCImountopts(struct blob_attr *msg, unsigned long *mount_flags, unsigned long *propagation_flags, char **mount_data, int *error)
 265 {
 266         struct blob_attr *cur;
 267         int rem;
 268         unsigned long mf = 0;
 269         unsigned long pf = 0;
 270         char *tmp;
 271         struct list_head fsopts = LIST_HEAD_INIT(fsopts);
 272         size_t len = 0;
 273         struct mount_opt *opt;
 274
 275         blobmsg_for_each_attr(cur, msg, rem) {
 276                 tmp = blobmsg_get_string(cur);
 277                 if (!strcmp("ro", tmp))
 278                         mf |= MS_RDONLY;
 279                 else if (!strcmp("rw", tmp))
 280                         mf &= ~MS_RDONLY;
 281                 else if (!strcmp("bind", tmp))
 282                         mf = MS_BIND;
 283                 else if (!strcmp("rbind", tmp))
 284                         mf |= MS_BIND | MS_REC;
 285                 else if (!strcmp("sync", tmp))
 286                         mf |= MS_SYNCHRONOUS;
 287                 else if (!strcmp("async", tmp))
 288                         mf &= ~MS_SYNCHRONOUS;
 289                 else if (!strcmp("atime", tmp))
 290                         mf &= ~MS_NOATIME;
 291                 else if (!strcmp("noatime", tmp))
 292                         mf |= MS_NOATIME;
 293                 else if (!strcmp("defaults", tmp))
 294                         mf = 0; /* rw, suid, dev, exec, auto, nouser, and async */
 295                 else if (!strcmp("dev", tmp))
 296                         mf &= ~MS_NODEV;
 297                 else if (!strcmp("nodev", tmp))
 298                         mf |= MS_NODEV;
 299                 else if (!strcmp("iversion", tmp))
 300                         mf |= MS_I_VERSION;
 301                 else if (!strcmp("noiversion", tmp))
 302                         mf &= ~MS_I_VERSION;
 303                 else if (!strcmp("diratime", tmp))
 304                         mf &= ~MS_NODIRATIME;
 305                 else if (!strcmp("nodiratime", tmp))
 306                         mf |= MS_NODIRATIME;
 307                 else if (!strcmp("dirsync", tmp))
 308                         mf |= MS_DIRSYNC;
 309                 else if (!strcmp("exec", tmp))
 310                         mf &= ~MS_NOEXEC;
 311                 else if (!strcmp("noexec", tmp))
 312                         mf |= MS_NOEXEC;
 313                 else if (!strcmp("mand", tmp))
 314                         mf |= MS_MANDLOCK;
 315                 else if (!strcmp("nomand", tmp))
 316                         mf &= ~MS_MANDLOCK;
 317                 else if (!strcmp("relatime", tmp))
 318                         mf |= MS_RELATIME;
 319                 else if (!strcmp("norelatime", tmp))
 320                         mf &= ~MS_RELATIME;
 321                 else if (!strcmp("strictatime", tmp))
 322                         mf |= MS_STRICTATIME;
 323                 else if (!strcmp("nostrictatime", tmp))
 324                         mf &= ~MS_STRICTATIME;
 325                 else if (!strcmp("lazytime", tmp))
 326                         mf |= MS_LAZYTIME;
 327                 else if (!strcmp("nolazytime", tmp))
 328                         mf &= ~MS_LAZYTIME;
 329                 else if (!strcmp("suid", tmp))
 330                         mf &= ~MS_NOSUID;
 331                 else if (!strcmp("nosuid", tmp))
 332                         mf |= MS_NOSUID;
 333                 else if (!strcmp("remount", tmp))
 334                         mf |= MS_REMOUNT;
 335                 /* propagation flags */
 336                 else if (!strcmp("private", tmp))
 337                         pf |= MS_PRIVATE;
 338                 else if (!strcmp("rprivate", tmp))
 339                         pf |= MS_PRIVATE | MS_REC;
 340                 else if (!strcmp("slave", tmp))
 341                         pf |= MS_SLAVE;
 342                 else if (!strcmp("rslave", tmp))
 343                         pf |= MS_SLAVE | MS_REC;
 344                 else if (!strcmp("shared", tmp))
 345                         pf |= MS_SHARED;
 346                 else if (!strcmp("rshared", tmp))
 347                         pf |= MS_SHARED | MS_REC;
 348                 else if (!strcmp("unbindable", tmp))
 349                         pf |= MS_UNBINDABLE;
 350                 else if (!strcmp("runbindable", tmp))
 351                         pf |= MS_UNBINDABLE | MS_REC;
 352                 /* special case: 'nofail' */
 353                 else if(!strcmp("nofail", tmp))
 354                         *error = 0;
 355                 else if (!strcmp("auto", tmp) ||
 356                          !strcmp("noauto", tmp) ||
 357                          !strcmp("user", tmp) ||
 358                          !strcmp("group", tmp) ||
 359                          !strcmp("_netdev", tmp))
 360                         DEBUG("ignoring built-in mount option %s\n", tmp);
 361                 else {
 362                         /* filesystem-specific free-form option */
 363                         opt = calloc(1, sizeof(*opt));
 364                         opt->optstr = tmp;
 365                         list_add_tail(&opt->list, &fsopts);
 366                 }
 367         };
 368
 369         *mount_flags = mf;
 370         *propagation_flags = pf;
 371
 372         list_for_each_entry(opt, &fsopts, list) {
 373                 if (len)
 374                         ++len;
 375
 376                 len += strlen(opt->optstr);
 377         };
 378
 379         if (len) {
 380                 *mount_data = calloc(len + 1, sizeof(char));
 381                 if (!mount_data)
 382                         return ENOMEM;
 383
 384                 len = 0;
 385                 list_for_each_entry(opt, &fsopts, list) {
 386                         if (len)
 387                                 strcat(*mount_data, ",");
 388
 389                         strcat(*mount_data, opt->optstr);
 390                         ++len;
 391                 };
 392
 393                 list_del(&fsopts);
 394         }
 395
 396         DEBUG("mount flags(%08lx) propagation(%08lx) fsopts(\"%s\")\n", mf, pf, *mount_data?:"");
 397
 398         return 0;
 399 }
 400
 401 int parseOCImount(struct blob_attr *msg)
 402 {
 403         struct blob_attr *tb[__OCI_MOUNT_MAX];
 404         unsigned long mount_flags = 0;
 405         unsigned long propagation_flags = 0;
 406         char *mount_data = NULL;
 407         int ret, err = -1;
 408
 409         blobmsg_parse(oci_mount_policy, __OCI_MOUNT_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 410
 411         if (!tb[OCI_MOUNT_DESTINATION])
 412                 return EINVAL;
 413
 414         if (tb[OCI_MOUNT_OPTIONS]) {
 415                 ret = parseOCImountopts(tb[OCI_MOUNT_OPTIONS], &mount_flags, &propagation_flags, &mount_data, &err);
 416                 if (ret)
 417                         return ret;
 418         }
 419
 420         ret = add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL,
 421                   blobmsg_get_string(tb[OCI_MOUNT_DESTINATION]),
 422                   tb[OCI_MOUNT_TYPE] ? blobmsg_get_string(tb[OCI_MOUNT_TYPE]) : NULL,
 423                   mount_flags, propagation_flags, mount_data, err);
 424
 425         if (mount_data)
 426                 free(mount_data);
 427
 428         return ret;
 429 }
 430
 431 static void build_noafile(void) {
 432         int fd;
 433
 434         fd = creat(UJAIL_NOAFILE, 0000);
 435         if (fd == -1)
 436                 return;
 437
 438         close(fd);
 439         return;
 440 }
 441
 442 int mount_all(const char *jailroot) {
 443         struct library *l;
 444         struct mount *m;
 445
 446         build_noafile();
 447
 448         avl_for_each_element(&libraries, l, avl)
 449                 add_mount_bind(l->path, 1, -1);
 450
 451         avl_for_each_element(&mounts, m, avl)
 452                 if (do_mount(jailroot, m->source, m->target, m->filesystemtype, m->mountflags,
 453                              m->propflags, m->optstr, m->error, m->inner))
 454                         return -1;
 455
 456         return 0;
 457 }
 458
 459 void mount_list_init(void) {
 460         avl_init(&mounts, avl_strcmp, false, NULL);
 461 }
 462
 463 static int add_script_interp(const char *path, const char *map, int size)
 464 {
 465         int start = 2;
 466         while (start < size && map[start] != '/') {
 467                 start++;
 468         }
 469         if (start >= size) {
 470                 ERROR("bad script interp (%s)\n", path);
 471                 return -1;
 472         }
 473         int stop = start + 1;
 474         while (stop < size && map[stop] > 0x20 && map[stop] <= 0x7e) {
 475                 stop++;
 476         }
 477         if (stop >= size || (stop-start) > PATH_MAX) {
 478                 ERROR("bad script interp (%s)\n", path);
 479                 return -1;
 480         }
 481         char buf[PATH_MAX];
 482         strncpy(buf, map+start, stop-start);
 483         return add_path_and_deps(buf, 1, -1, 0);
 484 }
 485
 486 int add_path_and_deps(const char *path, int readonly, int error, int lib)
 487 {
 488         assert(path != NULL);
 489
 490         if (lib == 0 && path[0] != '/') {
 491                 ERROR("%s is not an absolute path\n", path);
 492                 return error;
 493         }
 494
 495         char *map = NULL;
 496         int fd, ret = -1;
 497         if (path[0] == '/') {
 498                 if (avl_find(&mounts, path))
 499                         return 0;
 500                 fd = open(path, O_RDONLY|O_CLOEXEC);
 501                 if (fd == -1)
 502                         return error;
 503                 add_mount_bind(path, readonly, error);
 504         } else {
 505                 if (avl_find(&libraries, path))
 506                         return 0;
 507                 char *fullpath;
 508                 fd = lib_open(&fullpath, path);
 509                 if (fd == -1)
 510                         return error;
 511                 if (fullpath) {
 512                         alloc_library(fullpath, path);
 513                         free(fullpath);
 514                 }
 515         }
 516
 517         struct stat s;
 518         if (fstat(fd, &s) == -1) {
 519                 ERROR("fstat(%s) failed: %m\n", path);
 520                 ret = error;
 521                 goto out;
 522         }
 523
 524         if (!S_ISREG(s.st_mode)) {
 525                 ret = 0;
 526                 goto out;
 527         }
 528
 529         /* too small to be an ELF or a script -> "normal" file */
 530         if (s.st_size < 4) {
 531                 ret = 0;
 532                 goto out;
 533         }
 534
 535         map = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 536         if (map == MAP_FAILED) {
 537                 ERROR("failed to mmap %s: %m\n", path);
 538                 ret = -1;
 539                 goto out;
 540         }
 541
 542         if (map[0] == '#' && map[1] == '!') {
 543                 ret = add_script_interp(path, map, s.st_size);
 544                 goto out;
 545         }
 546
 547         if (map[0] == ELFMAG0 && map[1] == ELFMAG1 && map[2] == ELFMAG2 && map[3] == ELFMAG3) {
 548                 ret = elf_load_deps(path, map);
 549                 goto out;
 550         }
 551
 552         ret = 0;
 553
 554 out:
 555         if (fd >= 0)
 556                 close(fd);
 557         if (map)
 558                 munmap(map, s.st_size);
 559
 560         return ret;
 561 }