[RFC] [Patch 1/1] IBAC Patch

Mimi Zohar
2007-03-14T10:36:34Z

This is a posting of an updated IBAC patch, based on comments from the
LSM and LKML mailing lists, which include the following fixes:
- Updated Kconfig SECURITY_IBAC description
and SECURITY_IBAC_BOOTPARAM default value
- Prefixed all log messages with "ibac:"
- Redefined a couple of 'int' variables as 'static int'

This is a request for comments for a new Integrity Based Access
Control(IBAC) LSM module which bases access control decisions
on the new integrity framework services.

(Hopefully this will help clarify the interaction between an LSM
module and LIM module.)

Index: linux-2.6.21-rc3-mm2/security/ibac/Kconfig
===================================================================
--- /dev/null
+++ linux-2.6.21-rc3-mm2/security/ibac/Kconfig
@@ -0,0 +1,41 @@
+config SECURITY_IBAC
+ boolean "IBAC support"
+ depends on SECURITY && SECURITY_NETWORK && INTEGRITY
+ help
+ Integrity Based Access Control(IBAC) uses the Linux
+ Integrity Module(LIM) API calls to verify an executable's
+ metadata and data's integrity. Based on the results,
+ execution permission is permitted/denied. Integrity
+ providers may implement the LIM hooks differently. For
+ more information on integrity verification refer to the
+ specific integrity provider documentation.
+
+config SECURITY_IBAC_BOOTPARAM
+ bool "IBAC boot parameter"
+ depends on SECURITY_IBAC
+ default n
+ help
+ This option adds a kernel parameter 'ibac', which allows IBAC
+ to be disabled at boot. If this option is selected, IBAC
+ functionality can be disabled with ibac=0 on the kernel
+ command line. The purpose of this option is to allow a
+ single kernel image to be distributed with IBAC built in,
+ but not necessarily enabled.
+
+ If you are unsure how to answer this question, answer N.
+
+config SECURITY_IBAC_BOOTPARAM_VALUE
+ int "IBAC boot parameter default value"
+ depends on SECURITY_IBAC_BOOTPARAM
+ range 0 1
+ default 0
+ help
+ This option sets the default value for the kernel parameter
+ 'ibac', which allows IBAC to be disabled at boot. If this
+ option is set to 0 (zero), the IBAC kernel parameter will
+ default to 0, disabling IBAC at bootup. If this option is
+ set to 1 (one), the IBAC kernel parameter will default to 1,
+ enabling IBAC at bootup.
+
+ If you are unsure how to answer this question, answer 0.
+
Index: linux-2.6.21-rc3-mm2/security/ibac/Makefile
===================================================================
--- /dev/null
+++ linux-2.6.21-rc3-mm2/security/ibac/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for building IBAC
+#
+
+obj-$(CONFIG_SECURITY_IBAC) += ibac.o
+ibac-y := ibac_main.o
Index: linux-2.6.21-rc3-mm2/security/ibac/ibac_main.c
===================================================================
--- /dev/null
+++ linux-2.6.21-rc3-mm2/security/ibac/ibac_main.c
@@ -0,0 +1,126 @@
+/*
+ * Integrity Based Access Control (IBAC)
+ *
+ * Copyright (C) 2007 IBM Corporation
+ * Author: Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program 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, version 2 of the License.
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kernel.h>
+#include <linux/security.h>
+#include <linux/integrity.h>
+
+#ifdef CONFIG_SECURITY_IBAC_BOOTPARAM
+static int ibac_enabled = CONFIG_SECURITY_IBAC_BOOTPARAM_VALUE;
+
+static int __init ibac_enabled_setup(char *str)
+{
+ ibac_enabled = simple_strtol(str, NULL, 0);
+ return 1;
+}
+
+__setup("ibac=", ibac_enabled_setup);
+#else
+static int ibac_enabled = 0;
+#endif
+
+static unsigned int integrity_enforce;
+static int __init integrity_enforce_setup(char *str)
+{
+ integrity_enforce = simple_strtol(str, NULL, 0);
+ return 1;
+}
+
+__setup("ibac_enforce=", integrity_enforce_setup);
+
+#define XATTR_NAME "security.evm.hash"
+
+static inline int is_kernel_thread(struct task_struct *tsk)
+{
+ return (!tsk->mm) ? 1 : 0;
+}
+
+static int ibac_bprm_check_security(struct linux_binprm *bprm)
+{
+ struct dentry *dentry = bprm->file->f_dentry;
+ int xattr_len;
+ char *xattr_value = NULL;
+ int rc, status;
+
+ rc = integrity_verify_metadata(dentry, XATTR_NAME,
+ &xattr_value, &xattr_len, &status);
+ if (rc == -EOPNOTSUPP) {
+ kfree(xattr_value);
+ return 0;
+ }
+
+ if (rc < 0) {
+ printk(KERN_INFO "ibac: verify_metadata %s failed "
+ "(rc: %d - status: %d)\n", bprm->filename, rc, status);
+ if (!integrity_enforce)
+ rc = 0;
+ goto out;
+ }
+ if (status != INTEGRITY_PASS) { /* FAIL | NO_LABEL */
+ if (!is_kernel_thread(current)) {
+ printk(KERN_INFO "ibac: verify_metadata %s "
+ "(Integrity status: FAIL)\n", bprm->filename);
+ if (integrity_enforce) {
+ rc = -EACCES;
+ goto out;
+ }
+ }
+ }
+
+ rc = integrity_verify_data(dentry, &status);
+ if (rc < 0) {
+ printk(KERN_INFO "ibac: %s verify_data failed "
+ "(rc: %d - status: %d)\n", bprm->filename, rc, status);
+ if (!integrity_enforce)
+ rc = 0;
+ goto out;
+ }
+ if (status != INTEGRITY_PASS) {
+ if (!is_kernel_thread(current)) {
+ printk(KERN_INFO "ibac: verify_data %s "
+ "(Integrity status: FAIL)\n", bprm->filename);
+ if (integrity_enforce) {
+ rc = -EACCES;
+ goto out;
+ }
+ }
+ }
+
+ kfree(xattr_value);
+
+ /* measure all integrity level executables */
+ integrity_measure(dentry, bprm->filename, MAY_EXEC);
+ return 0;
+out:
+ kfree(xattr_value);
+ return rc;
+}
+
+static struct security_operations ibac_security_ops = {
+ .bprm_check_security = ibac_bprm_check_security
+};
+
+static int __init init_ibac(void)
+{
+ int rc;
+
+ if (!ibac_enabled)
+ return 0;
+
+ rc = register_security(&ibac_security_ops);
+ if (rc != 0)
+ panic("ibac: unable to register with kernel\n");
+ return rc;
+}
+
+security_initcall(init_ibac);
Index: linux-2.6.21-rc3-mm2/security/Kconfig
===================================================================
--- linux-2.6.21-rc3-mm2.orig/security/Kconfig
+++ linux-2.6.21-rc3-mm2/security/Kconfig
@@ -125,5 +125,6 @@ config SECURITY_ROOTPLUG
source security/selinux/Kconfig

source security/slim/Kconfig
+source security/ibac/Kconfig
endmenu

Index: linux-2.6.21-rc3-mm2/security/Makefile
===================================================================
--- linux-2.6.21-rc3-mm2.orig/security/Makefile
+++ linux-2.6.21-rc3-mm2/security/Makefile
@@ -14,6 +14,7 @@ endif
obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o
obj-$(CONFIG_INTEGRITY) += integrity.o integrity_dummy.o
obj-$(CONFIG_INTEGRITY_EVM) += evm/
+obj-$(CONFIG_SECURITY_IBAC) += ibac/
# Must precede capability.o in order to stack properly.
obj-$(CONFIG_SECURITY_SLIM) += slim/
obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o