src/lxc/storage/storage_utils.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * Copyright © 2017 Canonical Ltd.
   5  *
   6  * Authors:
   7  * Christian Brauner <christian.brauner@ubuntu.com>
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #define _GNU_SOURCE
  25 #include <dirent.h>
  26 #include <errno.h>
  27 #include <fcntl.h>
  28 #include <grp.h>
  29 #include <inttypes.h>
  30 #include <libgen.h>
  31 #include <sched.h>
  32 #include <stdint.h>
  33 #include <stdio.h>
  34 #include <string.h>
  35 #include <unistd.h>
  36 #include <sys/mount.h>
  37 #include <sys/prctl.h>
  38 #include <sys/types.h>
  39 #include <sys/stat.h>
  40 #include <sys/wait.h>
  41
  42 #include "log.h"
  43 #include "nbd.h"
  44 #include "parse.h"
  45 #include "storage.h"
  46 #include "storage_utils.h"
  47 #include "utils.h"
  48
  49 #ifndef BLKGETSIZE64
  50 #define BLKGETSIZE64 _IOR(0x12, 114, size_t)
  51 #endif
  52
  53 lxc_log_define(storage_utils, lxc);
  54
  55 /* the bulk of this needs to become a common helper */
  56 char *dir_new_path(char *src, const char *oldname, const char *name,
  57                    const char *oldpath, const char *lxcpath)
  58 {
  59         char *ret, *p, *p2;
  60         int l1, l2, nlen;
  61
  62         nlen = strlen(src) + 1;
  63         l1 = strlen(oldpath);
  64         p = src;
  65         /* if src starts with oldpath, look for oldname only after
  66          * that path */
  67         if (strncmp(src, oldpath, l1) == 0) {
  68                 p += l1;
  69                 nlen += (strlen(lxcpath) - l1);
  70         }
  71         l2 = strlen(oldname);
  72         while ((p = strstr(p, oldname)) != NULL) {
  73                 p += l2;
  74                 nlen += strlen(name) - l2;
  75         }
  76
  77         ret = malloc(nlen);
  78         if (!ret)
  79                 return NULL;
  80
  81         p = ret;
  82         if (strncmp(src, oldpath, l1) == 0) {
  83                 p += sprintf(p, "%s", lxcpath);
  84                 src += l1;
  85         }
  86
  87         while ((p2 = strstr(src, oldname)) != NULL) {
  88                 strncpy(p, src, p2 - src); // copy text up to oldname
  89                 p += p2 - src;             // move target pointer (p)
  90                 p += sprintf(p, "%s",
  91                              name); // print new name in place of oldname
  92                 src = p2 + l2;      // move src to end of oldname
  93         }
  94         sprintf(p, "%s", src); // copy the rest of src
  95         return ret;
  96 }
  97
  98 /*
  99  * attach_block_device returns true if all went well,
 100  * meaning either a block device was attached or was not
 101  * needed.  It returns false if something went wrong and
 102  * container startup should be stopped.
 103  */
 104 bool attach_block_device(struct lxc_conf *conf)
 105 {
 106         char *path;
 107
 108         if (!conf->rootfs.path)
 109                 return true;
 110
 111         path = conf->rootfs.path;
 112         if (!requires_nbd(path))
 113                 return true;
 114
 115         path = strchr(path, ':');
 116         if (!path)
 117                 return false;
 118
 119         path++;
 120         if (!attach_nbd(path, conf))
 121                 return false;
 122
 123         return true;
 124 }
 125
 126 /*
 127  * return block size of dev->src in units of bytes
 128  */
 129 int blk_getsize(struct lxc_storage *bdev, uint64_t *size)
 130 {
 131         int fd, ret;
 132         char *src;
 133
 134         src = lxc_storage_get_path(bdev->src, bdev->type);
 135         fd = open(src, O_RDONLY);
 136         if (fd < 0)
 137                 return -1;
 138
 139         ret = ioctl(fd, BLKGETSIZE64, size); // size of device in bytes
 140         close(fd);
 141         return ret;
 142 }
 143
 144 void detach_block_device(struct lxc_conf *conf)
 145 {
 146         if (conf->nbd_idx != -1)
 147                 detach_nbd_idx(conf->nbd_idx);
 148 }
 149
 150 /*
 151  * Given a lxc_storage (presumably blockdev-based), detect the fstype
 152  * by trying mounting (in a private mntns) it.
 153  * @lxc_storage: bdev to investigate
 154  * @type: preallocated char* in which to write the fstype
 155  * @len: length of passed in char*
 156  * Returns length of fstype, of -1 on error
 157  */
 158 int detect_fs(struct lxc_storage *bdev, char *type, int len)
 159 {
 160         int p[2], ret;
 161         size_t linelen;
 162         pid_t pid;
 163         FILE *f;
 164         char *sp1, *sp2, *sp3, *srcdev, *line = NULL;
 165
 166         if (!bdev || !bdev->src || !bdev->dest)
 167                 return -1;
 168
 169         srcdev = lxc_storage_get_path(bdev->src, bdev->type);
 170
 171         ret = pipe(p);
 172         if (ret < 0)
 173                 return -1;
 174
 175         if ((pid = fork()) < 0)
 176                 return -1;
 177
 178         if (pid > 0) {
 179                 int status;
 180                 close(p[1]);
 181                 memset(type, 0, len);
 182                 ret = read(p[0], type, len - 1);
 183                 close(p[0]);
 184                 if (ret < 0) {
 185                         SYSERROR("error reading from pipe");
 186                         wait(&status);
 187                         return -1;
 188                 } else if (ret == 0) {
 189                         ERROR("child exited early - fstype not found");
 190                         wait(&status);
 191                         return -1;
 192                 }
 193                 wait(&status);
 194                 type[len - 1] = '\0';
 195                 INFO("detected fstype %s for %s", type, srcdev);
 196                 return ret;
 197         }
 198
 199         if (unshare(CLONE_NEWNS) < 0)
 200                 exit(1);
 201
 202         if (detect_shared_rootfs()) {
 203                 if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL)) {
 204                         SYSERROR("Failed to make / rslave");
 205                         ERROR("Continuing...");
 206                 }
 207         }
 208
 209         ret = mount_unknown_fs(srcdev, bdev->dest, bdev->mntopts);
 210         if (ret < 0) {
 211                 ERROR("failed mounting %s onto %s to detect fstype", srcdev,
 212                       bdev->dest);
 213                 exit(1);
 214         }
 215
 216         // if symlink, get the real dev name
 217         char devpath[MAXPATHLEN];
 218         char *l = linkderef(srcdev, devpath);
 219         if (!l)
 220                 exit(1);
 221         f = fopen("/proc/self/mounts", "r");
 222         if (!f)
 223                 exit(1);
 224
 225         while (getline(&line, &linelen, f) != -1) {
 226                 sp1 = strchr(line, ' ');
 227                 if (!sp1)
 228                         exit(1);
 229                 *sp1 = '\0';
 230                 if (strcmp(line, l))
 231                         continue;
 232                 sp2 = strchr(sp1 + 1, ' ');
 233                 if (!sp2)
 234                         exit(1);
 235                 *sp2 = '\0';
 236                 sp3 = strchr(sp2 + 1, ' ');
 237                 if (!sp3)
 238                         exit(1);
 239                 *sp3 = '\0';
 240                 sp2++;
 241                 if (write(p[1], sp2, strlen(sp2)) != strlen(sp2))
 242                         exit(1);
 243
 244                 exit(0);
 245         }
 246
 247         exit(1);
 248 }
 249
 250 int do_mkfs_exec_wrapper(void *args)
 251 {
 252         int ret;
 253         char *mkfs;
 254         char **data = args;
 255         /* strlen("mkfs.")
 256          * +
 257          * strlen(data[0])
 258          * +
 259          * \0
 260          */
 261         size_t len = 5 + strlen(data[0]) + 1;
 262
 263         mkfs = malloc(len);
 264         if (!mkfs)
 265                 return -1;
 266
 267         ret = snprintf(mkfs, len, "mkfs.%s", data[0]);
 268         if (ret < 0 || (size_t)ret >= len) {
 269                 free(mkfs);
 270                 return -1;
 271         }
 272
 273         TRACE("executing \"%s %s\"", mkfs, data[1]);
 274         execlp(mkfs, mkfs, data[1], (char *)NULL);
 275         SYSERROR("failed to run \"%s %s \"", mkfs, data[1]);
 276         return -1;
 277 }
 278
 279 /*
 280  * This will return 1 for physical disks, qemu-nbd, loop, etc right now only lvm
 281  * is a block device.
 282  */
 283 int is_blktype(struct lxc_storage *b)
 284 {
 285         if (strcmp(b->type, "lvm") == 0)
 286                 return 1;
 287
 288         return 0;
 289 }
 290
 291 int mount_unknown_fs(const char *rootfs, const char *target,
 292                      const char *options)
 293 {
 294         size_t i;
 295         int ret;
 296         struct cbarg {
 297                 const char *rootfs;
 298                 const char *target;
 299                 const char *options;
 300         } cbarg = {
 301             .rootfs = rootfs,
 302             .target = target,
 303             .options = options,
 304         };
 305
 306         /*
 307          * find the filesystem type with brute force:
 308          * first we check with /etc/filesystems, in case the modules
 309          * are auto-loaded and fall back to the supported kernel fs
 310          */
 311         char *fsfile[] = {
 312             "/etc/filesystems",
 313             "/proc/filesystems",
 314         };
 315
 316         for (i = 0; i < sizeof(fsfile) / sizeof(fsfile[0]); i++) {
 317                 if (access(fsfile[i], F_OK))
 318                         continue;
 319
 320                 ret = lxc_file_for_each_line(fsfile[i], find_fstype_cb, &cbarg);
 321                 if (ret < 0) {
 322                         ERROR("failed to parse '%s'", fsfile[i]);
 323                         return -1;
 324                 }
 325
 326                 if (ret)
 327                         return 0;
 328         }
 329
 330         ERROR("failed to determine fs type for '%s'", rootfs);
 331         return -1;
 332 }
 333
 334 /*
 335  * These are copied from conf.c.  However as conf.c will be moved to using
 336  * the callback system, they can be pulled from there eventually, so we
 337  * don't need to pollute utils.c with these low level functions
 338  */
 339 int find_fstype_cb(char *buffer, void *data)
 340 {
 341         struct cbarg {
 342                 const char *rootfs;
 343                 const char *target;
 344                 const char *options;
 345         } *cbarg = data;
 346
 347         unsigned long mntflags;
 348         char *mntdata;
 349         char *fstype;
 350
 351         /* we don't try 'nodev' entries */
 352         if (strstr(buffer, "nodev"))
 353                 return 0;
 354
 355         fstype = buffer;
 356         fstype += lxc_char_left_gc(fstype, strlen(fstype));
 357         fstype[lxc_char_right_gc(fstype, strlen(fstype))] = '\0';
 358
 359         DEBUG("trying to mount '%s'->'%s' with fstype '%s'", cbarg->rootfs,
 360               cbarg->target, fstype);
 361
 362         if (parse_mntopts(cbarg->options, &mntflags, &mntdata) < 0) {
 363                 free(mntdata);
 364                 return 0;
 365         }
 366
 367         if (mount(cbarg->rootfs, cbarg->target, fstype, mntflags, mntdata)) {
 368                 DEBUG("mount failed with error: %s", strerror(errno));
 369                 free(mntdata);
 370                 return 0;
 371         }
 372
 373         free(mntdata);
 374
 375         INFO("mounted '%s' on '%s', with fstype '%s'", cbarg->rootfs,
 376              cbarg->target, fstype);
 377
 378         return 1;
 379 }
 380
 381 char *linkderef(char *path, char *dest)
 382 {
 383         struct stat sbuf;
 384         ssize_t ret;
 385
 386         ret = stat(path, &sbuf);
 387         if (ret < 0)
 388                 return NULL;
 389
 390         if (!S_ISLNK(sbuf.st_mode))
 391                 return path;
 392
 393         ret = readlink(path, dest, MAXPATHLEN);
 394         if (ret < 0) {
 395                 SYSERROR("error reading link %s", path);
 396                 return NULL;
 397         } else if (ret >= MAXPATHLEN) {
 398                 ERROR("link in %s too long", path);
 399                 return NULL;
 400         }
 401         dest[ret] = '\0';
 402
 403         return dest;
 404 }
 405
 406 /*
 407  * is an unprivileged user allowed to make this kind of snapshot
 408  */
 409 bool unpriv_snap_allowed(struct lxc_storage *b, const char *t, bool snap,
 410                          bool maybesnap)
 411 {
 412         if (!t) {
 413                 // new type will be same as original
 414                 // (unless snap && b->type == dir, in which case it will be
 415                 // overlayfs -- which is also allowed)
 416                 if (strcmp(b->type, "dir") == 0 ||
 417                     strcmp(b->type, "aufs") == 0 ||
 418                     strcmp(b->type, "overlay") == 0 ||
 419                     strcmp(b->type, "overlayfs") == 0 ||
 420                     strcmp(b->type, "btrfs") == 0 ||
 421                     strcmp(b->type, "loop") == 0)
 422                         return true;
 423
 424                 return false;
 425         }
 426
 427         // unprivileged users can copy and snapshot dir, overlayfs,
 428         // and loop.  In particular, not zfs, btrfs, or lvm.
 429         if (strcmp(t, "dir") == 0 ||
 430             strcmp(t, "aufs") == 0 ||
 431             strcmp(t, "overlay") == 0 ||
 432             strcmp(t, "overlayfs") == 0 ||
 433             strcmp(t, "btrfs") == 0 ||
 434             strcmp(t, "loop") == 0)
 435                 return true;
 436
 437         return false;
 438 }
 439
 440 bool is_valid_storage_type(const char *type)
 441 {
 442         if (strcmp(type, "dir") == 0 ||
 443             strcmp(type, "btrfs") == 0 ||
 444             strcmp(type, "aufs") == 0 ||
 445             strcmp(type, "loop") == 0 ||
 446             strcmp(type, "lvm") == 0 ||
 447             strcmp(type, "nbd") == 0 ||
 448             strcmp(type, "overlayfs") == 0 ||
 449             strcmp(type, "rbd") == 0 ||
 450             strcmp(type, "zfs") == 0)
 451                 return true;
 452
 453         return false;
 454 }
 455
 456 int storage_destroy_wrapper(void *data)
 457 {
 458         struct lxc_conf *conf = data;
 459
 460         if (setgid(0) < 0) {
 461                 ERROR("Failed to setgid to 0");
 462                 return -1;
 463         }
 464
 465         if (setgroups(0, NULL) < 0)
 466                 WARN("Failed to clear groups");
 467
 468         if (setuid(0) < 0) {
 469                 ERROR("Failed to setuid to 0");
 470                 return -1;
 471         }
 472
 473         if (!storage_destroy(conf))
 474                 return -1;
 475
 476         return 0;
 477 }