Branch data     Line data    Source code

       1                 :            : /* SPDX-License-Identifier: LGPL-2.1+ */
       2                 :            : 
       3                 :            : #include <errno.h>
       4                 :            : #include <stdlib.h>
       5                 :            : #include <unistd.h>
       6                 :            : 
       7                 :            : #include "alloc-util.h"
       8                 :            : #include "dev-setup.h"
       9                 :            : #include "label.h"
      10                 :            : #include "log.h"
      11                 :            : #include "nulstr-util.h"
      12                 :            : #include "path-util.h"
      13                 :            : #include "umask-util.h"
      14                 :            : #include "user-util.h"
      15                 :            : 
      16                 :          0 : int dev_setup(const char *prefix, uid_t uid, gid_t gid) {
      17                 :            :         static const char symlinks[] =
      18                 :            :                 "-/proc/kcore\0"     "/dev/core\0"
      19                 :            :                 "/proc/self/fd\0"    "/dev/fd\0"
      20                 :            :                 "/proc/self/fd/0\0"  "/dev/stdin\0"
      21                 :            :                 "/proc/self/fd/1\0"  "/dev/stdout\0"
      22                 :            :                 "/proc/self/fd/2\0"  "/dev/stderr\0";
      23                 :            : 
      24                 :            :         const char *j, *k;
      25                 :            :         int r;
      26                 :            : 
      27   [ #  #  #  #  :          0 :         NULSTR_FOREACH_PAIR(j, k, symlinks) {
                   #  # ]
      28      [ #  #  # ]:          0 :                 _cleanup_free_ char *link_name = NULL;
      29                 :            :                 const char *n;
      30                 :            : 
      31         [ #  # ]:          0 :                 if (j[0] == '-') {
      32                 :          0 :                         j++;
      33                 :            : 
      34         [ #  # ]:          0 :                         if (access(j, F_OK) < 0)
      35                 :          0 :                                 continue;
      36                 :            :                 }
      37                 :            : 
      38         [ #  # ]:          0 :                 if (prefix) {
      39                 :          0 :                         link_name = path_join(prefix, k);
      40         [ #  # ]:          0 :                         if (!link_name)
      41                 :          0 :                                 return -ENOMEM;
      42                 :            : 
      43                 :          0 :                         n = link_name;
      44                 :            :                 } else
      45                 :          0 :                         n = k;
      46                 :            : 
      47                 :          0 :                 r = symlink_label(j, n);
      48         [ #  # ]:          0 :                 if (r < 0)
      49         [ #  # ]:          0 :                         log_debug_errno(r, "Failed to symlink %s to %s: %m", j, n);
      50                 :            : 
      51   [ #  #  #  # ]:          0 :                 if (uid != UID_INVALID || gid != GID_INVALID)
      52         [ #  # ]:          0 :                         if (lchown(n, uid, gid) < 0)
      53         [ #  # ]:          0 :                                 log_debug_errno(errno, "Failed to chown %s: %m", n);
      54                 :            :         }
      55                 :            : 
      56                 :          0 :         return 0;
      57                 :            : }
      58                 :            : 
      59                 :          0 : int make_inaccessible_nodes(const char *root, uid_t uid, gid_t gid) {
      60                 :            :         static const struct {
      61                 :            :                 const char *name;
      62                 :            :                 mode_t mode;
      63                 :            :         } table[] = {
      64                 :            :                 { "/run/systemd",                   S_IFDIR  | 0755 },
      65                 :            :                 { "/run/systemd/inaccessible",      S_IFDIR  | 0000 },
      66                 :            :                 { "/run/systemd/inaccessible/reg",  S_IFREG  | 0000 },
      67                 :            :                 { "/run/systemd/inaccessible/dir",  S_IFDIR  | 0000 },
      68                 :            :                 { "/run/systemd/inaccessible/fifo", S_IFIFO  | 0000 },
      69                 :            :                 { "/run/systemd/inaccessible/sock", S_IFSOCK | 0000 },
      70                 :            : 
      71                 :            :                 /* The following two are likely to fail if we lack the privs for it (for example in an userns
      72                 :            :                  * environment, if CAP_SYS_MKNOD is missing, or if a device node policy prohibit major/minor of 0
      73                 :            :                  * device nodes to be created). But that's entirely fine. Consumers of these files should carry
      74                 :            :                  * fallback to use a different node then, for example /run/systemd/inaccessible/sock, which is close
      75                 :            :                  * enough in behaviour and semantics for most uses. */
      76                 :            :                 { "/run/systemd/inaccessible/chr",  S_IFCHR  | 0000 },
      77                 :            :                 { "/run/systemd/inaccessible/blk",  S_IFBLK  | 0000 },
      78                 :            :         };
      79                 :            : 
      80                 :          0 :         _cleanup_umask_ mode_t u;
      81                 :            :         size_t i;
      82                 :            :         int r;
      83                 :            : 
      84                 :          0 :         u = umask(0000);
      85                 :            : 
      86                 :            :         /* Set up inaccessible (and empty) file nodes of all types. This are used to as mount sources for over-mounting
      87                 :            :          * ("masking") file nodes that shall become inaccessible and empty for specific containers or services. We try
      88                 :            :          * to lock down these nodes as much as we can, but otherwise try to match them as closely as possible with the
      89                 :            :          * underlying file, i.e. in the best case we offer the same node type as the underlying node. */
      90                 :            : 
      91         [ #  # ]:          0 :         for (i = 0; i < ELEMENTSOF(table); i++) {
      92      [ #  #  # ]:          0 :                 _cleanup_free_ char *path = NULL;
      93                 :            : 
      94                 :          0 :                 path = path_join(root, table[i].name);
      95         [ #  # ]:          0 :                 if (!path)
      96                 :          0 :                         return log_oom();
      97                 :            : 
      98         [ #  # ]:          0 :                 if (S_ISDIR(table[i].mode))
      99                 :          0 :                         r = mkdir(path, table[i].mode & 07777);
     100                 :            :                 else
     101                 :          0 :                         r = mknod(path, table[i].mode, makedev(0, 0));
     102         [ #  # ]:          0 :                 if (r < 0) {
     103         [ #  # ]:          0 :                         if (errno != EEXIST)
     104         [ #  # ]:          0 :                                 log_debug_errno(errno, "Failed to create '%s', ignoring: %m", path);
     105                 :          0 :                         continue;
     106                 :            :                 }
     107                 :            : 
     108   [ #  #  #  # ]:          0 :                 if (uid != UID_INVALID || gid != GID_INVALID) {
     109         [ #  # ]:          0 :                         if (lchown(path, uid, gid) < 0)
     110         [ #  # ]:          0 :                                 log_debug_errno(errno, "Failed to chown '%s': %m", path);
     111                 :            :                 }
     112                 :            :         }
     113                 :            : 
     114                 :          0 :         return 0;
     115                 :            : }