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Subject[PATCH bpf-next v3 02/10] bpf: lsm: Add a skeleton and config options
Date
From: KP Singh <kpsingh@google.com>

The LSM can be enabled by CONFIG_SECURITY_BPF. Without
CONFIG_SECURITY_BPF_ENFORCE, the LSM will run the attached eBPF programs
but not enforce MAC policy based on the return value of the attached
programs.

The BPF LSM has two kinds of hooks:

- Statically defined hooks defined at init with __lsm_ro_after_init
which are attached to the security_hook_heads defined in
security/security.c similar to other LSMs.
- Mutable hooks that are attached to a separate security_hook_heads
maintained by the BPF LSM (introduced in a subsequent patch).

The mutable hooks are always executed after all the static hooks
(irrespective of the position of "bpf" in the list of LSMs). Therefore,
the newly introduced LSM_ORDER_LAST represents the behaviour of this LSM
correctly

Signed-off-by: KP Singh <kpsingh@google.com>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
---
MAINTAINERS | 7 +++++++
include/linux/lsm_hooks.h | 1 +
security/Kconfig | 11 ++++++-----
security/Makefile | 2 ++
security/bpf/Kconfig | 22 ++++++++++++++++++++++
security/bpf/Makefile | 5 +++++
security/bpf/lsm.c | 26 ++++++++++++++++++++++++++
security/security.c | 5 +++++
8 files changed, 74 insertions(+), 5 deletions(-)
create mode 100644 security/bpf/Kconfig
create mode 100644 security/bpf/Makefile
create mode 100644 security/bpf/lsm.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 702382b89c37..e2b7f76a1a70 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3203,6 +3203,13 @@ S: Supported
F: arch/x86/net/
X: arch/x86/net/bpf_jit_comp32.c

+BPF SECURITY MODULE
+M: KP Singh <kpsingh@chromium.org>
+L: linux-security-module@vger.kernel.org
+L: bpf@vger.kernel.org
+S: Maintained
+F: security/bpf/
+
BROADCOM B44 10/100 ETHERNET DRIVER
M: Michael Chan <michael.chan@broadcom.com>
L: netdev@vger.kernel.org
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 20d8cf194fb7..5f744fcb2275 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2121,6 +2121,7 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
enum lsm_order {
LSM_ORDER_FIRST = -1, /* This is only for capabilities. */
LSM_ORDER_MUTABLE = 0,
+ LSM_ORDER_LAST = 1,
};

struct lsm_info {
diff --git a/security/Kconfig b/security/Kconfig
index 2a1a2d396228..6f1aab195e7d 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/bpf/Kconfig"
source "security/safesetid/Kconfig"
source "security/lockdown/Kconfig"

@@ -277,11 +278,11 @@ endchoice

config LSM
string "Ordered list of enabled LSMs"
- default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor" if DEFAULT_SECURITY_SMACK
- default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo" if DEFAULT_SECURITY_APPARMOR
- default "lockdown,yama,loadpin,safesetid,integrity,tomoyo" if DEFAULT_SECURITY_TOMOYO
- default "lockdown,yama,loadpin,safesetid,integrity" if DEFAULT_SECURITY_DAC
- default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor"
+ default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
+ default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
+ default "lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
+ default "lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
+ default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
help
A comma-separated list of LSMs, in initialization order.
Any LSMs left off this list will be ignored. This can be
diff --git a/security/Makefile b/security/Makefile
index be1dd9d2cb2f..50e6821dd7b7 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -12,6 +12,7 @@ subdir-$(CONFIG_SECURITY_YAMA) += yama
subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin
subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid
subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown
+subdir-$(CONFIG_SECURITY_BPF) += bpf

# always enable default capabilities
obj-y += commoncap.o
@@ -29,6 +30,7 @@ obj-$(CONFIG_SECURITY_YAMA) += yama/
obj-$(CONFIG_SECURITY_LOADPIN) += loadpin/
obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/
obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/
+obj-$(CONFIG_SECURITY_BPF) += bpf/
obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o

# Object integrity file lists
diff --git a/security/bpf/Kconfig b/security/bpf/Kconfig
new file mode 100644
index 000000000000..a5f6c67ae526
--- /dev/null
+++ b/security/bpf/Kconfig
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright 2019 Google LLC.
+
+config SECURITY_BPF
+ bool "BPF-based MAC and audit policy"
+ depends on SECURITY
+ depends on BPF_SYSCALL
+ help
+ This enables instrumentation of the security hooks with
+ eBPF programs.
+
+ If you are unsure how to answer this question, answer N.
+
+config SECURITY_BPF_ENFORCE
+ bool "Deny operations based on the evaluation of the attached programs"
+ depends on SECURITY_BPF
+ 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 or deny the operation
+ guarded by the security hook.
diff --git a/security/bpf/Makefile b/security/bpf/Makefile
new file mode 100644
index 000000000000..26a0ab6f99b7
--- /dev/null
+++ b/security/bpf/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright 2019 Google LLC.
+
+obj-$(CONFIG_SECURITY_BPF) := lsm.o
diff --git a/security/bpf/lsm.c b/security/bpf/lsm.c
new file mode 100644
index 000000000000..dc9ac03c7aa0
--- /dev/null
+++ b/security/bpf/lsm.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright 2019 Google LLC.
+ */
+
+#include <linux/lsm_hooks.h>
+
+/* This is only for internal hooks, always statically shipped as part of the
+ * BPF LSM. Statically defined hooks are appended to the security_hook_heads
+ * which is common for LSMs and R/O after init.
+ */
+static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {};
+
+static int __init bpf_lsm_init(void)
+{
+ security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), "bpf");
+ pr_info("LSM support for eBPF active\n");
+ return 0;
+}
+
+DEFINE_LSM(bpf) = {
+ .name = "bpf",
+ .init = bpf_lsm_init,
+ .order = LSM_ORDER_LAST,
+};
diff --git a/security/security.c b/security/security.c
index cd2d18d2d279..30a8aa700557 100644
--- a/security/security.c
+++ b/security/security.c
@@ -264,6 +264,11 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
}
}

+ for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+ if (lsm->order == LSM_ORDER_LAST)
+ append_ordered_lsm(lsm, "last");
+ }
+
/* Disable all LSMs not in the ordered list. */
for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
if (exists_ordered_lsm(lsm))
--
2.20.1
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