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