core: mount and initialize Smack

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. The /smack mountpoint is not supported.
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

diff --git a/Makefile.am b/Makefile.am
index 7e408798a62cf9eb06107900f7b31d58c1de2e15..3f6493773207d01da664b4dbd928db3a92a580a5 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -842,6 +842,8 @@ 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/README b/README
index 5649a51689624631be90ac4d48aa88f089995382..9d7a54769d5f1c6564a10f36f1df1524a257bd76 100644 (file)
--- a/README
+++ b/README
@@ -44,6 +44,8 @@ REQUIREMENTS:
           CONFIG_NET
           CONFIG_SYSFS
 
+        Linux kernel >= 3.8 for Smack support
+
         Udev will fail to work with the legacy layout:
           CONFIG_SYSFS_DEPRECATED=n
 

diff --git a/src/core/main.c b/src/core/main.c
index 24d8d3e9824223c93999303e0e38b60a6a95c891..727a41074071a5030d1cbe63dad5cb8d9f34d222 100644 (file)
--- 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,
@@ -1362,6 +1363,8 @@ 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 dab36014675223dcb4bb9c0c353f406e24b9de10..42cdc6dc52423a07192b2f7ee7baf0db7d0591e9 100644 (file)
--- 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 (file)
index 0000000..88e6437
--- /dev/null
+++ b/src/core/smack-setup.c
@@ -0,0 +1,98 @@
+/*-*- 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@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 "macro.h"
+#include "smack-setup.h"
+#include "util.h"
+#include "log.h"
+#include "label.h"
+
+#define ACCESSES_D_PATH "/etc/smack/accesses.d/"
+
+int smack_setup(void) {
+        _cleanup_fclose_ FILE *smack = NULL;
+        _cleanup_closedir_ DIR *dir = NULL;
+        struct dirent *entry;
+        char buf[NAME_MAX];
+        int dfd = -1;
+
+        smack = fopen("/sys/fs/smackfs/load2", "we");
+        if (!smack)  {
+                log_info("Smack is not enabled in the kernel, not loading access rules.");
+                return 0;
+        }
+
+        /* write rules to load2 from every file in the directory */
+        dir = opendir(ACCESSES_D_PATH);
+        if (!dir) {
+                log_info("Smack access rules directory not found: " ACCESSES_D_PATH);
+                return 0;
+        }
+
+        dfd = dirfd(dir);
+        if (dfd < 0) {
+                log_error("Smack access rules directory " ACCESSES_D_PATH " not opened: %m");
+                return 0;
+        }
+
+        FOREACH_DIRENT(entry, dir, return 0) {
+                _cleanup_fclose_ FILE *policy = NULL;
+                _cleanup_close_ int pol = -1;
+
+                pol = openat(dfd, entry->d_name, O_RDONLY|O_CLOEXEC);
+                if (pol < 0) {
+                        log_error("Smack access rule file %s not opened: %m", entry->d_name);
+                        continue;
+                }
+
+                policy = fdopen(pol, "re");
+                if (!policy) {
+                        log_error("Smack access rule file %s not opened: %m", entry->d_name);
+                        continue;
+                }
+
+                pol = -1;
+
+                /* load2 write rules in the kernel require a line buffered stream */
+                FOREACH_LINE(buf, policy, log_error("Failed to read from Smack access rule file %s: %m", entry->d_name)) {
+                        fputs(buf, smack);
+                        fflush(smack);
+                }
+        }
+
+        log_info("Successfully loaded Smack policies.");
+
+        return 0;
+}

diff --git a/src/core/smack-setup.h b/src/core/smack-setup.h
new file mode 100644 (file)
index 0000000..ffe9184
--- /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@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);