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relabel-etc: Split remount into, remount and relabel-etc
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Split these into two different binaries we two different
resonsibilities. They don't share so much functionality.

Signed-off-by: Eric Curtin <[email protected]>
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ericcurtin committed Jun 19, 2024
1 parent f280b12 commit 4c565cd
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Showing 8 changed files with 249 additions and 100 deletions.
2 changes: 2 additions & 0 deletions Makefile-boot.am
Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ endif
if BUILDOPT_SYSTEMD
systemdsystemunit_DATA = src/boot/ostree-prepare-root.service \
src/boot/ostree-remount.service \
src/boot/ostree-relabel-etc.service \
src/boot/ostree-boot-complete.service \
src/boot/ostree-finalize-staged.service \
src/boot/ostree-finalize-staged.path \
Expand Down Expand Up @@ -71,6 +72,7 @@ EXTRA_DIST += src/boot/dracut/module-setup.sh \
src/boot/ostree-prepare-root.service \
src/boot/ostree-finalize-staged.path \
src/boot/ostree-remount.service \
src/boot/ostree-relabel-etc.service \
src/boot/ostree-finalize-staged.service \
src/boot/ostree-finalize-staged-hold.service \
src/boot/[email protected] \
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14 changes: 10 additions & 4 deletions Makefile-switchroot.am
Original file line number Diff line number Diff line change
Expand Up @@ -22,11 +22,11 @@ ostree_prepare_root_CPPFLAGS = $(AM_CPPFLAGS)
ostree_prepare_root_LDADD =

if BUILDOPT_SYSTEMD
ostree_boot_PROGRAMS += ostree-remount
ostree_boot_PROGRAMS += ostree-remount ostree-relabel-etc
else
# It is built anyway as a side-effect of having the symlink in tests/,
# and if we declare it here, it gets cleaned up properly
check_PROGRAMS += ostree-remount
check_PROGRAMS += ostree-remount ostree-relabel-etc
endif

if BUILDOPT_USE_STATIC_COMPILER
Expand Down Expand Up @@ -63,9 +63,15 @@ ostree_remount_SOURCES = \
ostree_remount_CPPFLAGS = $(AM_CPPFLAGS) $(OT_INTERNAL_GIO_UNIX_CFLAGS) -Isrc/switchroot -I$(srcdir)/src/libotcore -I$(srcdir)/src/libotutil -I$(srcdir)/libglnx
ostree_remount_LDADD = $(AM_LDFLAGS) $(OT_INTERNAL_GIO_UNIX_LIBS) libotcore.la libotutil.la libglnx.la

ostree_relabel_etc_SOURCES = \
src/switchroot/ostree-relabel-etc.c \
$(NULL)
ostree_relabel_etc_CPPFLAGS = $(AM_CPPFLAGS) $(OT_INTERNAL_GIO_UNIX_CFLAGS) -Isrc/switchroot -I$(srcdir)/src/libotcore -I$(srcdir)/src/libotutil -I$(srcdir)/libglnx
ostree_relabel_etc_LDADD = $(AM_LDFLAGS) $(OT_INTERNAL_GIO_UNIX_LIBS) libotcore.la libotutil.la libglnx.la

if USE_SELINUX
ostree_remount_CPPFLAGS += $(OT_DEP_SELINUX_CFLAGS)
ostree_remount_LDADD += $(OT_DEP_SELINUX_LIBS)
ostree_relabel_etc_CPPFLAGS += $(OT_DEP_SELINUX_CFLAGS)
ostree_relabel_etc_LDADD += $(OT_DEP_SELINUX_LIBS)
endif

if USE_COMPOSEFS
Expand Down
1 change: 1 addition & 0 deletions src/boot/mkinitcpio/ostree
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
build() {
add_binary /usr/lib/ostree/ostree-prepare-root
add_binary /usr/lib/ostree/ostree-remount
add_binary /usr/lib/ostree/ostree-relabel-etc

add_file /usr/lib/systemd/system/ostree-prepare-root.service
add_symlink /usr/lib/systemd/system/initrd-root-fs.target.wants/ostree-prepare-root.service \
Expand Down
40 changes: 40 additions & 0 deletions src/boot/ostree-relabel-etc.service
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
# Copyright (C) 2013 Colin Walters <[email protected]>
#
# This library 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 of the License, or (at your option) any later version.
#
# This library 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 this library. If not, see <https://www.gnu.org/licenses/>.

[Unit]
Description=OSTree Relabel etc
Documentation=man:ostree(1)
DefaultDependencies=no
ConditionKernelCommandLine=ostree
OnFailure=emergency.target
Conflicts=umount.target
# Run after core mounts
After=-.mount var.mount
After=systemd-remount-fs.service
# But we run *before* most other core bootup services that need write access to /etc and /var
Before=local-fs.target umount.target
Before=systemd-random-seed.service plymouth-read-write.service systemd-journal-flush.service systemd-sysusers.service
Before=systemd-tmpfiles-setup.service systemd-rfkill.service systemd-rfkill.socket

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/lib/ostree/ostree-relabel-etc
StandardInput=null
StandardOutput=journal
StandardError=journal+console

[Install]
WantedBy=local-fs.target
5 changes: 5 additions & 0 deletions src/libostree/ostree-impl-system-generator.c
Original file line number Diff line number Diff line change
Expand Up @@ -109,6 +109,11 @@ require_internal_units (const char *normal_dir, const char *early_dir, const cha
< 0)
return glnx_throw_errno_prefix (error, "symlinkat");

if (symlinkat (SYSTEM_DATA_UNIT_PATH "/ostree-relabel-etc.service", normal_dir_dfd,
"local-fs.target.requires/ostree-relabel-etc.service")
< 0)
return glnx_throw_errno_prefix (error, "symlinkat");

if (!glnx_shutil_mkdir_p_at (normal_dir_dfd, "multi-user.target.wants", 0755, cancellable, error))
return FALSE;
if (symlinkat (SYSTEM_DATA_UNIT_PATH "/ostree-finalize-staged.path", normal_dir_dfd,
Expand Down
190 changes: 190 additions & 0 deletions src/switchroot/ostree-relabel-etc.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,190 @@
/*
* Copyright (C) 2011 Colin Walters <[email protected]>
*
* SPDX-License-Identifier: LGPL-2.0+
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library. If not, see <https://www.gnu.org/licenses/>.
*
* Author: Colin Walters <[email protected]>
*/

#include "config.h"

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <unistd.h>
#ifdef HAVE_SELINUX
#include <selinux/restorecon.h>
#endif

#include "ostree-mount-util.h"
#include "otcore.h"

/* Relabel the directory $real_path, which is going to be an overlayfs mount,
* based on the content of an overlayfs upperdirectory that is in use by the mount.
* The goal is that we relabel in the overlay mount all the files that have been
* modified (directly or via parent copyup operations) since the overlayfs was
* mounted. This will be used for the /etc overlayfs mount where no selinux labels
* are set before selinux policy is loaded.
*/
static void
relabel_dir_for_upper (const char *upper_path, const char *real_path, gboolean is_dir)
{
#ifdef HAVE_SELINUX
/* Ignore ENOENT, because if there is no file to relabel we can continue,
* systemd-sysusers runs in parallel and can create temporary files in /etc
* causing failures like:
* "Failed to relabel /etc/.#gshadowJzu4Rx: No such file or directory"
*/
if (selinux_restorecon (real_path, 0))
{
if (errno == ENOENT)
return;

err (EXIT_FAILURE, "Failed to relabel %s", real_path);
}

if (!is_dir)
return;

g_auto (GLnxDirFdIterator) dfd_iter = {
0,
};

if (!glnx_dirfd_iterator_init_at (AT_FDCWD, upper_path, FALSE, &dfd_iter, NULL))
err (EXIT_FAILURE, "Failed to open upper directory %s for relabeling", upper_path);

while (TRUE)
{
struct dirent *dent;

if (!glnx_dirfd_iterator_next_dent_ensure_dtype (&dfd_iter, &dent, NULL, NULL))
{
err (EXIT_FAILURE, "Failed to read upper directory %s for relabelin", upper_path);
break;
}

if (dent == NULL)
break;

g_autofree char *upper_child = g_build_filename (upper_path, dent->d_name, NULL);
g_autofree char *real_child = g_build_filename (real_path, dent->d_name, NULL);
relabel_dir_for_upper (upper_child, real_child, dent->d_type == DT_DIR);
}
#endif
}

int
main (int argc, char *argv[])
{
g_autoptr (GError) error = NULL;
g_autoptr (GVariant) ostree_run_metadata_v = NULL;
{
glnx_autofd int fd = open (OTCORE_RUN_BOOTED, O_RDONLY | O_CLOEXEC);
if (fd < 0)
{
/* We really expect that nowadays that everything is done in the initramfs,
* but historically we created this file here, so we'll continue to do be
* sure here it exists. This code should be removed at some point though.
*/
if (errno == ENOENT)
{
int subfd = open (OTCORE_RUN_BOOTED, O_EXCL | O_CREAT | O_WRONLY | O_NOCTTY | O_CLOEXEC,
0640);
if (subfd != -1)
(void)close (subfd);
}
else
{
err (EXIT_FAILURE, "failed to open %s", OTCORE_RUN_BOOTED);
}
}
else
{
if (!ot_variant_read_fd (fd, 0, G_VARIANT_TYPE_VARDICT, TRUE, &ostree_run_metadata_v,
&error))
errx (EXIT_FAILURE, "failed to read %s: %s", OTCORE_RUN_BOOTED, error->message);
}
}
g_autoptr (GVariantDict) ostree_run_metadata = g_variant_dict_new (ostree_run_metadata_v);

/* The /sysroot mount needs to be private to avoid having a mount for e.g. /var/cache
* also propagate to /sysroot/ostree/deploy/$stateroot/var/cache
*
* Today systemd remounts / (recursively) as shared, so we're undoing that as early
* as possible. See also a copy of this in ostree-prepare-root.c.
*/
if (mount ("none", "/sysroot", NULL, MS_REC | MS_PRIVATE, NULL) < 0)
perror ("warning: While remounting /sysroot MS_PRIVATE");

const char *transient_etc = NULL;
g_variant_dict_lookup (ostree_run_metadata, OTCORE_RUN_BOOTED_KEY_TRANSIENT_ETC, "&s",
&transient_etc);

if (transient_etc)
{
/* If the initramfs created any files in /etc (directly or via overlay copy-up) they
* will be unlabeled, because the selinux policy is not loaded until after the
* pivot-root. So, for all files in the upper dir, relabel the corresponding overlay
* file.
*
* Also, note that during boot systemd will create a /run/machine-id ->
* /etc/machine-id bind mount (as /etc is read-only early on). It will then later
* replace this mount with a real one (in systemd-machine-id-commit.service).
*
* We need to label the actual overlayfs file, not the temporary bind-mount. To do
* this we unmount the covering mount before relabeling, but we do so in a temporary
* private namespace to avoid affecting other parts of the system.
*/

glnx_autofd int initial_ns_fd = -1;
if (g_file_test ("/run/machine-id", G_FILE_TEST_EXISTS)
&& g_file_test ("/etc/machine-id", G_FILE_TEST_EXISTS))
{
initial_ns_fd = open ("/proc/self/ns/mnt", O_RDONLY | O_NOCTTY | O_CLOEXEC);
if (initial_ns_fd < 0)
err (EXIT_FAILURE, "Failed to open initial namespace");

if (unshare (CLONE_NEWNS) < 0)
err (EXIT_FAILURE, "Failed to unshare initial namespace");

/* Ensure unmount is not propagated */
if (mount ("none", "/etc", NULL, MS_REC | MS_PRIVATE, NULL) < 0)
err (EXIT_FAILURE, "warning: While remounting /etc MS_PRIVATE");

if (umount2 ("/etc/machine-id", MNT_DETACH) < 0)
err (EXIT_FAILURE, "Failed to unmount machine-id");
}

g_autofree char *upper = g_build_filename (transient_etc, "upper", NULL);
relabel_dir_for_upper (upper, "/etc", TRUE);

if (initial_ns_fd != -1 && setns (initial_ns_fd, CLONE_NEWNS) < 0)
err (EXIT_FAILURE, "Failed to join initial namespace");
}

exit (EXIT_SUCCESS);
}

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