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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include "alloc-util.h"
#include "dev-setup.h"
#include "label.h"
#include "log.h"
#include "nulstr-util.h"
#include "path-util.h"
#include "umask-util.h"
#include "user-util.h"
int dev_setup(const char *prefix, uid_t uid, gid_t gid) {
static const char symlinks[] =
"-/proc/kcore\0" "/dev/core\0"
"/proc/self/fd\0" "/dev/fd\0"
"/proc/self/fd/0\0" "/dev/stdin\0"
"/proc/self/fd/1\0" "/dev/stdout\0"
"/proc/self/fd/2\0" "/dev/stderr\0";
const char *j, *k;
int r;
NULSTR_FOREACH_PAIR(j, k, symlinks) {
_cleanup_free_ char *link_name = NULL;
const char *n;
if (j[0] == '-') {
j++;
if (access(j, F_OK) < 0)
continue;
}
if (prefix) {
link_name = path_join(prefix, k);
if (!link_name)
return -ENOMEM;
n = link_name;
} else
n = k;
r = symlink_label(j, n);
if (r < 0)
log_debug_errno(r, "Failed to symlink %s to %s: %m", j, n);
if (uid != UID_INVALID || gid != GID_INVALID)
if (lchown(n, uid, gid) < 0)
log_debug_errno(errno, "Failed to chown %s: %m", n);
}
return 0;
}
int make_inaccessible_nodes(
const char *parent_dir,
uid_t uid,
gid_t gid) {
static const struct {
const char *name;
mode_t mode;
} table[] = {
{ "inaccessible", S_IFDIR | 0755 },
{ "inaccessible/reg", S_IFREG | 0000 },
{ "inaccessible/dir", S_IFDIR | 0000 },
{ "inaccessible/fifo", S_IFIFO | 0000 },
{ "inaccessible/sock", S_IFSOCK | 0000 },
/* The following two are likely to fail if we lack the privs for it (for example in an userns
* environment, if CAP_SYS_MKNOD is missing, or if a device node policy prohibits creation of
* device nodes with a major/minor of 0). But that's entirely fine. Consumers of these files
* should implement falling back to use a different node then, for example
* <root>/inaccessible/sock, which is close enough in behaviour and semantics for most uses.
*/
{ "inaccessible/chr", S_IFCHR | 0000 },
{ "inaccessible/blk", S_IFBLK | 0000 },
};
_cleanup_umask_ mode_t u;
int r;
if (!parent_dir)
parent_dir = "/run/systemd";
u = umask(0000);
/* Set up inaccessible (and empty) file nodes of all types. This are used to as mount sources for over-mounting
* ("masking") file nodes that shall become inaccessible and empty for specific containers or services. We try
* to lock down these nodes as much as we can, but otherwise try to match them as closely as possible with the
* underlying file, i.e. in the best case we offer the same node type as the underlying node. */
for (size_t i = 0; i < ELEMENTSOF(table); i++) {
_cleanup_free_ char *path = NULL;
path = path_join(parent_dir, table[i].name);
if (!path)
return log_oom();
if (S_ISDIR(table[i].mode))
r = mkdir_label(path, table[i].mode & 07777);
else
r = mknod_label(path, table[i].mode, makedev(0, 0));
if (r < 0) {
log_debug_errno(r, "Failed to create '%s', ignoring: %m", path);
continue;
}
if (uid != UID_INVALID || gid != GID_INVALID) {
if (lchown(path, uid, gid) < 0)
log_debug_errno(errno, "Failed to chown '%s': %m", path);
}
}
return 0;
}
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