scripts: add boot policy generation program

Enables an IPE policy to be enforced from kernel start, enabling access
control based on trust from kernel startup. This is accomplished by
transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a
c-string literal that is parsed at kernel startup as an unsigned policy.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

5 files changed, 43 insertions, 0 deletions

diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore
new file mode 100644
index 000000000000..6e9939be1cb7
--- /dev/null
+++ b/security/ipe/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+boot_policy.c
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 6bc487b689e0..fccc69e66af1 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -21,6 +21,16 @@ menuconfig SECURITY_IPE
 	  If unsure, answer N.
 
 if SECURITY_IPE
+config IPE_BOOT_POLICY
+	string "Integrity policy to apply on system startup"
+	help
+	  This option specifies a filepath to an IPE policy that is compiled
+	  into the kernel. This policy will be enforced until a policy update
+	  is deployed via the $securityfs/ipe/policies/$policy_name/active
+	  interface.
+
+	  If unsure, leave blank.
+
 menu "IPE Trust Providers"
 
 config IPE_PROP_DM_VERITY
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index e1019bb9f0f3..70eea140306b 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -5,7 +5,16 @@
 # Makefile for building the IPE module as part of the kernel tree.
 #
 
+quiet_cmd_polgen = IPE_POL $(2)
+      cmd_polgen = scripts/ipe/polgen/polgen security/ipe/boot_policy.c $(2)
+
+targets += boot_policy.c
+
+$(obj)/boot_policy.c: scripts/ipe/polgen/polgen $(CONFIG_IPE_BOOT_POLICY) FORCE
+	$(call if_changed,polgen,$(CONFIG_IPE_BOOT_POLICY))
+
 obj-$(CONFIG_SECURITY_IPE) += \
+	boot_policy.o \
 	digest.o \
 	eval.o \
 	hooks.o \
@@ -15,3 +24,5 @@ obj-$(CONFIG_SECURITY_IPE) += \
 	policy_fs.o \
 	policy_parser.o \
 	audit.o \
+
+clean-files := boot_policy.c \
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index b52fb6023904..5b6d19fb844a 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -190,6 +190,7 @@ static const struct file_operations enforce_fops = {
 static int __init ipe_init_securityfs(void)
 {
 	int rc = 0;
+	struct ipe_policy *ap;
 
 	if (!ipe_enabled)
 		return -EOPNOTSUPP;
@@ -220,6 +221,13 @@ static int __init ipe_init_securityfs(void)
 		goto err;
 	}
 
+	ap = rcu_access_pointer(ipe_active_policy);
+	if (ap) {
+		rc = ipe_new_policyfs_node(ap);
+		if (rc)
+			goto err;
+	}
+
 	np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops);
 	if (IS_ERR(np)) {
 		rc = PTR_ERR(np);
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index b410db0b486c..e19a18078cf3 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -9,6 +9,7 @@
 #include "hooks.h"
 #include "eval.h"
 
+extern const char *const ipe_boot_policy;
 bool ipe_enabled;
 
 static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
@@ -74,9 +75,20 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
  */
 static int __init ipe_init(void)
 {
+	struct ipe_policy *p = NULL;
+
 	security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), &ipe_lsmid);
 	ipe_enabled = true;
 
+	if (ipe_boot_policy) {
+		p = ipe_new_policy(ipe_boot_policy, strlen(ipe_boot_policy),
+				   NULL, 0);
+		if (IS_ERR(p))
+			return PTR_ERR(p);
+
+		rcu_assign_pointer(ipe_active_policy, p);
+	}
+
 	return 0;
 }