[RFC v1 01/14] krsi: Add a skeleton and config options for the KRSI LSM

[KP Singh <kpsingh@chromium.org>]

From: KP Singh <kpsingh@google.com>

The LSM can be enabled by:

- Enabling CONFIG_SECURITY_KRSI.
- Adding "krsi" to the CONFIG_LSM string.

Signed-off-by: KP Singh <kpsingh@google.com>
---
 MAINTAINERS            |  5 +++++
 security/Kconfig       |  1 +
 security/Makefile      |  2 ++
 security/krsi/Kconfig  | 22 ++++++++++++++++++++++
 security/krsi/Makefile |  1 +
 security/krsi/krsi.c   | 24 ++++++++++++++++++++++++
 6 files changed, 55 insertions(+)
 create mode 100644 security/krsi/Kconfig
 create mode 100644 security/krsi/Makefile
 create mode 100644 security/krsi/krsi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 9cbcf167bdd0..8e0364391d8b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9002,6 +9002,11 @@ F:	include/linux/kprobes.h
 F:	include/asm-generic/kprobes.h
 F:	kernel/kprobes.c
 
+KRSI SECURITY MODULE
+M:	KP Singh <kpsingh@chromium.org>
+S:	Supported
+F:	security/krsi/
+
 KS0108 LCD CONTROLLER DRIVER
 M:	Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
 S:	Maintained
diff --git a/security/Kconfig b/security/Kconfig
index 0d65594b5196..febf7953803f 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -236,6 +236,7 @@ source "security/tomoyo/Kconfig"
 source "security/apparmor/Kconfig"
 source "security/loadpin/Kconfig"
 source "security/yama/Kconfig"
+source "security/krsi/Kconfig"
 source "security/safesetid/Kconfig"
 
 source "security/integrity/Kconfig"
diff --git a/security/Makefile b/security/Makefile
index c598b904938f..25779ce89bf2 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -9,6 +9,7 @@ subdir-$(CONFIG_SECURITY_SMACK)		+= smack
 subdir-$(CONFIG_SECURITY_TOMOYO)        += tomoyo
 subdir-$(CONFIG_SECURITY_APPARMOR)	+= apparmor
 subdir-$(CONFIG_SECURITY_YAMA)		+= yama
+subdir-$(CONFIG_SECURITY_KRSI)		+= krsi
 subdir-$(CONFIG_SECURITY_LOADPIN)	+= loadpin
 subdir-$(CONFIG_SECURITY_SAFESETID)    += safesetid
 
@@ -25,6 +26,7 @@ obj-$(CONFIG_AUDIT)			+= lsm_audit.o
 obj-$(CONFIG_SECURITY_TOMOYO)		+= tomoyo/
 obj-$(CONFIG_SECURITY_APPARMOR)		+= apparmor/
 obj-$(CONFIG_SECURITY_YAMA)		+= yama/
+obj-$(CONFIG_SECURITY_KRSI)		+= krsi/
 obj-$(CONFIG_SECURITY_LOADPIN)		+= loadpin/
 obj-$(CONFIG_SECURITY_SAFESETID)       += safesetid/
 obj-$(CONFIG_CGROUP_DEVICE)		+= device_cgroup.o
diff --git a/security/krsi/Kconfig b/security/krsi/Kconfig
new file mode 100644
index 000000000000..bf5eab4355af
--- /dev/null
+++ b/security/krsi/Kconfig
@@ -0,0 +1,22 @@
+config SECURITY_KRSI
+	bool "Runtime Security Instrumentation (BPF-based MAC and audit policy)"
+	depends on SECURITY
+	depends on SECURITYFS
+	depends on BPF
+	depends on BPF_SYSCALL
+	help
+	  This selects the Kernel Runtime Security Instrumentation
+	  LSM which allows dynamic instrumentation of the security hooks with
+	  eBPF programs. The LSM creates per-hook files in securityfs to which
+	  eBPF programs can be attached.
+
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_KRSI_ENFORCE
+	bool "Deny operations based on the evaluation of the attached programs"
+	depends on SECURITY_KRSI
+	help
+	  eBPF programs attached to hooks can be used for both auditing and
+	  enforcement. Enabling enforcement implies that the evaluation result
+	  from the attached eBPF programs will allow and deny the operation
+	  guarded by the security hook.
diff --git a/security/krsi/Makefile b/security/krsi/Makefile
new file mode 100644
index 000000000000..73320e8d16f8
--- /dev/null
+++ b/security/krsi/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SECURITY_KRSI) := krsi.o
diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c
new file mode 100644
index 000000000000..9ce4f56fb78d
--- /dev/null
+++ b/security/krsi/krsi.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/lsm_hooks.h>
+
+static int krsi_process_execution(struct linux_binprm *bprm)
+{
+	return 0;
+}
+
+static struct security_hook_list krsi_hooks[] __lsm_ro_after_init = {
+	LSM_HOOK_INIT(bprm_check_security, krsi_process_execution),
+};
+
+static int __init krsi_init(void)
+{
+	security_add_hooks(krsi_hooks, ARRAY_SIZE(krsi_hooks), "krsi");
+	pr_info("eBPF and LSM are friends now.\n");
+	return 0;
+}
+
+DEFINE_LSM(krsi) = {
+	.name = "krsi",
+	.init = krsi_init,
+};
-- 
2.20.1