[systemd-devel] [PATCH] mount and initialize Smack
Nathaniel Chen
nathaniel.chen at intel.com
Tue Mar 5 15:24:27 PST 2013
SMACK is the Simple Mandatory Access Control Kernel, a minimal
approach to Access Control implemented as a kernel LSM.
The kernel exposes the smackfs filesystem API through which access
rules can be loaded. At boot time, we want to load the access rules
as early as possible to ensure all early boot steps are checked by Smack.
This patch mounts smackfs at the new location at /sys/fs/smackfs for
kernels 3.8 and above, and attempts to try /smack in case it fails.
You will need to create the /smack mountpoint manually if needed.
After mounting smackfs, rules are loaded from the usual location.
For more information about Smack see:
http://www.kernel.org/doc/Documentation/security/Smack.txt
---
Makefile.am | 2 +
src/core/main.c | 3 ++
src/core/mount-setup.c | 4 +-
src/core/smack-setup.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
src/core/smack-setup.h | 26 +++++++++++++
5 files changed, 134 insertions(+), 1 deletion(-)
create mode 100644 src/core/smack-setup.c
create mode 100644 src/core/smack-setup.h
diff --git a/Makefile.am b/Makefile.am
index 2108abe..b8bac5f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -832,6 +832,8 @@ libsystemd_core_la_SOURCES = \
src/core/selinux-access.h \
src/core/selinux-setup.c \
src/core/selinux-setup.h \
+ src/core/smack-setup.c \
+ src/core/smack-setup.h \
src/core/ima-setup.c \
src/core/ima-setup.h \
src/core/locale-setup.h \
diff --git a/src/core/main.c b/src/core/main.c
index 71e0a6c..71e7124 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -67,6 +67,7 @@
#include "selinux-setup.h"
#include "ima-setup.h"
#include "fileio.h"
+#include "smack-setup.h"
static enum {
ACTION_RUN,
@@ -1350,6 +1351,8 @@ int main(int argc, char *argv[]) {
goto finish;
if (ima_setup() < 0)
goto finish;
+ if (smack_setup() < 0)
+ goto finish;
}
if (label_init(NULL) < 0)
diff --git a/src/core/mount-setup.c b/src/core/mount-setup.c
index dab3601..0917fbe 100644
--- a/src/core/mount-setup.c
+++ b/src/core/mount-setup.c
@@ -66,7 +66,7 @@ typedef struct MountPoint {
/* The first three entries we might need before SELinux is up. The
* fourth (securityfs) is needed by IMA to load a custom policy. The
* other ones we can delay until SELinux and IMA are loaded. */
-#define N_EARLY_MOUNT 4
+#define N_EARLY_MOUNT 5
static const MountPoint mount_table[] = {
{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
@@ -77,6 +77,8 @@ static const MountPoint mount_table[] = {
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "securityfs", "/sys/kernel/security", "securityfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },
+ { "smackfs", "/sys/fs/smackfs", "smackfs", "smackfsdef=*", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
+ NULL, MNT_NONE},
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devpts", "/dev/pts", "devpts", "mode=620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC,
diff --git a/src/core/smack-setup.c b/src/core/smack-setup.c
new file mode 100644
index 0000000..38ce471
--- /dev/null
+++ b/src/core/smack-setup.c
@@ -0,0 +1,100 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright (C) 2013 Intel Corporation
+ Authors:
+ Nathaniel Chen <nathaniel.chen at intel.com>
+
+ 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 <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/vfs.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <sys/mount.h>
+#include <stdint.h>
+
+#include "smack-setup.h"
+#include "mount-setup.h"
+#include "util.h"
+#include "log.h"
+#include "label.h"
+#include "macro.h"
+
+#define ACCESSES_D_PATH "/etc/smack/accesses.d/"
+
+int smack_setup(void) {
+
+ FILE *smack;
+ FILE *policy;
+ int m = -1;
+ DIR *dir;
+ struct dirent *entry;
+ char pol[PATH_MAX];
+ char buf[NAME_MAX];
+
+ /* assure that we've attempted to mount smackfs */
+ mount_setup_early();
+
+ smack = fopen("/sys/fs/smackfs/load2", "w");
+ if (smack == NULL) {
+ m = mount("smackfs", "/smack", "smackfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, "smackfsdef=*");
+ if (m == -1) {
+ log_error("Smack is not enabled in the kernel. error: %s", strerror(errno));
+ return 0;
+ }
+ smack = fopen("/smack/load2", "w");
+ }
+
+ /* write rules to load2 from every file in the directory */
+ dir = opendir(ACCESSES_D_PATH);
+ if (dir == NULL) {
+ log_error("failed to open Smack policy directory %s, error: %s", ACCESSES_D_PATH, strerror(errno));
+ fclose(smack);
+ return -errno;
+ }
+ while ((entry = readdir(dir))) {
+ if (entry->d_name[0] == '.')
+ continue;
+
+ snprintf(pol, PATH_MAX, ACCESSES_D_PATH"%s", entry->d_name);
+ policy = fopen(pol, "r");
+ if (policy == NULL) {
+ log_error("Failed to open Smack policy file %s, error: %s", pol, strerror(errno));
+ fclose(smack);
+ closedir(dir);
+ return -errno;
+ }
+ /* load2 write rules in the kernel require a line buffered stream */
+ while ((fgets(buf, NAME_MAX, policy))) {
+ fprintf(smack, "%s", buf);
+ fflush(smack);
+ log_info("Smack rule written: %s", buf);
+ }
+ log_info("Successfully loaded custom Smack policy %s", pol);
+ fclose(policy);
+ }
+ closedir(dir);
+ fclose(smack);
+
+return 0;
+}
diff --git a/src/core/smack-setup.h b/src/core/smack-setup.h
new file mode 100644
index 0000000..2397646
--- /dev/null
+++ b/src/core/smack-setup.h
@@ -0,0 +1,26 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+ This file is part of systemd.
+
+ Copyright (C) 2013 Intel Corporation
+ Authors:
+ Nathaniel Chen <nathaniel.chen at intel.com>
+
+ 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/>.
+***/
+
+int smack_setup(void);
--
1.8.1.3
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