/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see .
***/
#include
#include
#ifdef HAVE_ACL
#include
#endif
#include
#include
#include
#include "acl-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "missing.h"
#include "nspawn-patch-uid.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#ifdef HAVE_ACL
static int get_acl(int fd, const char *name, acl_type_t type, acl_t *ret) {
char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
acl_t acl;
assert(fd >= 0);
assert(ret);
if (name) {
_cleanup_close_ int child_fd = -1;
child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (child_fd < 0)
return -errno;
xsprintf(procfs_path, "/proc/self/fd/%i", child_fd);
acl = acl_get_file(procfs_path, type);
} else if (type == ACL_TYPE_ACCESS)
acl = acl_get_fd(fd);
else {
xsprintf(procfs_path, "/proc/self/fd/%i", fd);
acl = acl_get_file(procfs_path, type);
}
if (!acl)
return -errno;
*ret = acl;
return 0;
}
static int set_acl(int fd, const char *name, acl_type_t type, acl_t acl) {
char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
int r;
assert(fd >= 0);
assert(acl);
if (name) {
_cleanup_close_ int child_fd = -1;
child_fd = openat(fd, name, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (child_fd < 0)
return -errno;
xsprintf(procfs_path, "/proc/self/fd/%i", child_fd);
r = acl_set_file(procfs_path, type, acl);
} else if (type == ACL_TYPE_ACCESS)
r = acl_set_fd(fd, acl);
else {
xsprintf(procfs_path, "/proc/self/fd/%i", fd);
r = acl_set_file(procfs_path, type, acl);
}
if (r < 0)
return -errno;
return 0;
}
static int shift_acl(acl_t acl, uid_t shift, acl_t *ret) {
_cleanup_(acl_freep) acl_t copy = NULL;
acl_entry_t i;
int r;
assert(acl);
assert(ret);
r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
if (r < 0)
return -errno;
while (r > 0) {
uid_t *old_uid, new_uid;
bool modify = false;
acl_tag_t tag;
if (acl_get_tag_type(i, &tag) < 0)
return -errno;
if (IN_SET(tag, ACL_USER, ACL_GROUP)) {
/* We don't distuingish here between uid_t and gid_t, let's make sure the compiler checks that
* this is actually OK */
assert_cc(sizeof(uid_t) == sizeof(gid_t));
old_uid = acl_get_qualifier(i);
if (!old_uid)
return -errno;
new_uid = shift | (*old_uid & UINT32_C(0xFFFF));
if (!uid_is_valid(new_uid))
return -EINVAL;
modify = new_uid != *old_uid;
if (modify && !copy) {
int n;
/* There's no copy of the ACL yet? if so, let's create one, and start the loop from the
* beginning, so that we copy all entries, starting from the first, this time. */
n = acl_entries(acl);
if (n < 0)
return -errno;
copy = acl_init(n);
if (!copy)
return -errno;
/* Seek back to the beginning */
r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
if (r < 0)
return -errno;
continue;
}
}
if (copy) {
acl_entry_t new_entry;
if (acl_create_entry(©, &new_entry) < 0)
return -errno;
if (acl_copy_entry(new_entry, i) < 0)
return -errno;
if (modify)
if (acl_set_qualifier(new_entry, &new_uid) < 0)
return -errno;
}
r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i);
if (r < 0)
return -errno;
}
*ret = copy;
copy = NULL;
return !!*ret;
}
static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) {
_cleanup_(acl_freep) acl_t acl = NULL, shifted = NULL;
bool changed = false;
int r;
assert(fd >= 0);
assert(st);
/* ACLs are not supported on symlinks, there's no point in trying */
if (S_ISLNK(st->st_mode))
return 0;
r = get_acl(fd, name, ACL_TYPE_ACCESS, &acl);
if (r == -EOPNOTSUPP)
return 0;
if (r < 0)
return r;
r = shift_acl(acl, shift, &shifted);
if (r < 0)
return r;
if (r > 0) {
r = set_acl(fd, name, ACL_TYPE_ACCESS, shifted);
if (r < 0)
return r;
changed = true;
}
if (S_ISDIR(st->st_mode)) {
acl_free(acl);
acl_free(shifted);
acl = shifted = NULL;
r = get_acl(fd, name, ACL_TYPE_DEFAULT, &acl);
if (r < 0)
return r;
r = shift_acl(acl, shift, &shifted);
if (r < 0)
return r;
if (r > 0) {
r = set_acl(fd, name, ACL_TYPE_DEFAULT, shifted);
if (r < 0)
return r;
changed = true;
}
}
return changed;
}
#else
static int patch_acls(int fd, const char *name, const struct stat *st, uid_t shift) {
return 0;
}
#endif
static int patch_fd(int fd, const char *name, const struct stat *st, uid_t shift) {
uid_t new_uid;
gid_t new_gid;
bool changed = false;
int r;
assert(fd >= 0);
assert(st);
new_uid = shift | (st->st_uid & UINT32_C(0xFFFF));
new_gid = (gid_t) shift | (st->st_gid & UINT32_C(0xFFFF));
if (!uid_is_valid(new_uid) || !gid_is_valid(new_gid))
return -EINVAL;
if (st->st_uid != new_uid || st->st_gid != new_gid) {
if (name)
r = fchownat(fd, name, new_uid, new_gid, AT_SYMLINK_NOFOLLOW);
else
r = fchown(fd, new_uid, new_gid);
if (r < 0)
return -errno;
/* The Linux kernel alters the mode in some cases of chown(). Let's undo this. */
if (name) {
if (!S_ISLNK(st->st_mode))
r = fchmodat(fd, name, st->st_mode, 0);
else /* AT_SYMLINK_NOFOLLOW is not available for fchmodat() */
r = 0;
} else
r = fchmod(fd, st->st_mode);
if (r < 0)
return -errno;
changed = true;
}
r = patch_acls(fd, name, st, shift);
if (r < 0)
return r;
return r > 0 || changed;
}
/*
* Check if the filesystem is fully compatible with user namespaces or
* UID/GID patching. Some filesystems in this list can be fully mounted inside
* user namespaces, however their inodes may relate to host resources or only
* valid in the global user namespace, therefore no patching should be applied.
*/
static int is_fs_fully_userns_compatible(int fd) {
struct statfs sfs;
assert(fd >= 0);
if (fstatfs(fd, &sfs) < 0)
return -errno;
return F_TYPE_EQUAL(sfs.f_type, BINFMTFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, CGROUP_SUPER_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, CGROUP2_SUPER_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, DEBUGFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, DEVPTS_SUPER_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, EFIVARFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, HUGETLBFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, MQUEUE_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, PROC_SUPER_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, PSTOREFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, SELINUX_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, SMACK_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, SECURITYFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, BPF_FS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, TRACEFS_MAGIC) ||
F_TYPE_EQUAL(sfs.f_type, SYSFS_MAGIC);
}
static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift, bool is_toplevel) {
bool changed = false;
int r;
assert(fd >= 0);
/* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we
* probably shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's
* stop the recursion when we hit procfs, sysfs or some other special file systems. */
r = is_fs_fully_userns_compatible(fd);
if (r < 0)
goto finish;
if (r > 0) {
r = 0; /* don't recurse */
goto finish;
}
r = patch_fd(fd, NULL, st, shift);
if (r == -EROFS) {
_cleanup_free_ char *name = NULL;
if (!is_toplevel) {
/* When we hit a ready-only subtree we simply skip it, but log about it. */
(void) fd_get_path(fd, &name);
log_debug("Skippping read-only file or directory %s.", strna(name));
r = 0;
}
goto finish;
}
if (r < 0)
goto finish;
if (S_ISDIR(st->st_mode)) {
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
if (!donate_fd) {
int copy;
copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
if (copy < 0) {
r = -errno;
goto finish;
}
fd = copy;
donate_fd = true;
}
d = fdopendir(fd);
if (!d) {
r = -errno;
goto finish;
}
fd = -1;
FOREACH_DIRENT_ALL(de, d, r = -errno; goto finish) {
struct stat fst;
if (STR_IN_SET(de->d_name, ".", ".."))
continue;
if (fstatat(dirfd(d), de->d_name, &fst, AT_SYMLINK_NOFOLLOW) < 0) {
r = -errno;
goto finish;
}
if (S_ISDIR(fst.st_mode)) {
int subdir_fd;
subdir_fd = openat(dirfd(d), de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
if (subdir_fd < 0) {
r = -errno;
goto finish;
}
r = recurse_fd(subdir_fd, true, &fst, shift, false);
if (r < 0)
goto finish;
if (r > 0)
changed = true;
} else {
r = patch_fd(dirfd(d), de->d_name, &fst, shift);
if (r < 0)
goto finish;
if (r > 0)
changed = true;
}
}
}
r = changed;
finish:
if (donate_fd)
safe_close(fd);
return r;
}
static int fd_patch_uid_internal(int fd, bool donate_fd, uid_t shift, uid_t range) {
struct stat st;
int r;
assert(fd >= 0);
/* Recursively adjusts the UID/GIDs of all files of a directory tree. This is used to automatically fix up an
* OS tree to the used user namespace UID range. Note that this automatic adjustment only works for UID ranges
* following the concept that the upper 16bit of a UID identify the container, and the lower 16bit are the actual
* UID within the container. */
if ((shift & 0xFFFF) != 0) {
/* We only support containers where the shift starts at a 2^16 boundary */
r = -EOPNOTSUPP;
goto finish;
}
if (range != 0x10000) {
/* We only support containers with 16bit UID ranges for the patching logic */
r = -EOPNOTSUPP;
goto finish;
}
if (fstat(fd, &st) < 0) {
r = -errno;
goto finish;
}
if ((uint32_t) st.st_uid >> 16 != (uint32_t) st.st_gid >> 16) {
/* We only support containers where the uid/gid container ID match */
r = -EBADE;
goto finish;
}
/* Try to detect if the range is already right. Of course, this a pretty drastic optimization, as we assume
* that if the top-level dir has the right upper 16bit assigned, then everything below will have too... */
if (((uint32_t) (st.st_uid ^ shift) >> 16) == 0)
return 0;
return recurse_fd(fd, donate_fd, &st, shift, true);
finish:
if (donate_fd)
safe_close(fd);
return r;
}
int fd_patch_uid(int fd, uid_t shift, uid_t range) {
return fd_patch_uid_internal(fd, false, shift, range);
}
int path_patch_uid(const char *path, uid_t shift, uid_t range) {
int fd;
fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
if (fd < 0)
return -errno;
return fd_patch_uid_internal(fd, true, shift, range);
}