nspawn: optionally fix up OS tree uid/gids for userns
This adds a new --private-userns-chown switch that may be used in combination with --private-userns. If it is passed a recursive chmod() operation is run on the OS tree, fixing all file owner UID/GIDs to the right ranges. This should make user namespacing pretty workable, as the OS trees don't need to be prepared manually anymore.
This commit is contained in:
Lennart Poettering
@@ -0,0 +1,417 @@
|
||||
/***
|
||||
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 <http://www.gnu.org/licenses/>.
|
||||
***/
|
||||
|
||||
#include <fcntl.h>
|
||||
#ifdef HAVE_ACL
|
||||
#include <sys/acl.h>
|
||||
#endif
|
||||
#include <sys/stat.h>
|
||||
#include <unistd.h>
|
||||
|
||||
#include "acl-util.h"
|
||||
#include "dirent-util.h"
|
||||
#include "fd-util.h"
|
||||
#include "nspawn-patch-uid.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 && !S_ISLNK(st->st_mode))
|
||||
r = fchmodat(fd, name, st->st_mode, 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;
|
||||
}
|
||||
|
||||
static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift) {
|
||||
bool changed = false;
|
||||
int r;
|
||||
|
||||
assert(fd >= 0);
|
||||
|
||||
r = patch_fd(fd, NULL, st, shift);
|
||||
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)
|
||||
return -errno;
|
||||
|
||||
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);
|
||||
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);
|
||||
|
||||
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);
|
||||
}
|
||||
Reference in New Issue
Block a user