main: added support for loading IMA custom policies

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The new function ima_setup() loads an IMA custom policy from a file in the
default location '/etc/ima/ima-policy', if present, and writes it to the
path 'ima/policy' in the security filesystem. This function is executed
at early stage in order to avoid that some file operations are not measured
by IMA and it is placed after the initialization of SELinux because IMA
needs the latter (or other security modules) to understand LSM-specific
rules. This feature is enabled by default and can be disabled by providing
the option '--disable-ima' to the configure script.

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Acked-by: Gianluca Ramunno <ramunno@polito.it>

1 files changed, 115 insertions, 0 deletions

diff --git a/src/ima-setup.c b/src/ima-setup.c
new file mode 100644
index 0000000000..03e43dcf16
--- /dev/null
+++ b/src/ima-setup.c
@@ -0,0 +1,115 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+  Copyright (C) 2012 Roberto Sassu - Politecnico di Torino, Italy
+                                     TORSEC group -- http://security.polito.it
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include "ima-setup.h"
+#include "mount-setup.h"
+#include "macro.h"
+#include "util.h"
+#include "log.h"
+#include "label.h"
+
+#define IMA_SECFS_DIR "/sys/kernel/security/ima"
+#define IMA_SECFS_POLICY IMA_SECFS_DIR "/policy"
+#define IMA_POLICY_PATH "/etc/ima/ima-policy"
+
+int ima_setup(void) {
+
+#ifdef HAVE_IMA
+       struct stat st;
+       ssize_t policy_size = 0, written = 0;
+       char *policy;
+       int policyfd = -1, imafd = -1;
+       int result = 0;
+
+#ifndef HAVE_SELINUX
+       /* Mount the securityfs filesystem */
+       mount_setup_early();
+#endif
+
+       if (stat(IMA_POLICY_PATH, &st) < 0)
+               return 0;
+
+       policy_size = st.st_size;
+       if (stat(IMA_SECFS_DIR, &st) < 0) {
+               log_debug("IMA support is disabled in the kernel, ignoring.");
+               return 0;
+       }
+
+       if (stat(IMA_SECFS_POLICY, &st) < 0) {
+               log_error("Another IMA custom policy has already been loaded, "
+                         "ignoring.");
+               return 0;
+       }
+
+       policyfd = open(IMA_POLICY_PATH, O_RDONLY|O_CLOEXEC);
+       if (policyfd < 0) {
+               log_error("Failed to open the IMA custom policy file %s (%m), "
+                         "ignoring.", IMA_POLICY_PATH);
+               return 0;
+       }
+
+       imafd = open(IMA_SECFS_POLICY, O_WRONLY|O_CLOEXEC);
+       if (imafd < 0) {
+               log_error("Failed to open the IMA kernel interface %s (%m), "
+                         "ignoring.", IMA_SECFS_POLICY);
+               goto out;
+       }
+
+       policy = mmap(NULL, policy_size, PROT_READ, MAP_PRIVATE, policyfd, 0);
+       if (policy == MAP_FAILED) {
+               log_error("mmap() failed (%m), freezing");
+               result = -errno;
+               goto out;
+       }
+
+       written = loop_write(imafd, policy, (size_t)policy_size, false);
+       if (written != policy_size) {
+               log_error("Failed to load the IMA custom policy file %s (%m), "
+                         "ignoring.", IMA_POLICY_PATH);
+               goto out_mmap;
+       }
+
+       log_info("Successfully loaded the IMA custom policy %s.",
+                IMA_POLICY_PATH);
+out_mmap:
+       munmap(policy, policy_size);
+out:
+       if (policyfd >= 0)
+                close_nointr_nofail(policyfd);
+       if (imafd >= 0)
+                close_nointr_nofail(imafd);
+       if (result)
+                return result;
+#endif /* HAVE_IMA */
+
+       return 0;
+}