ima: add build time policy

IMA by default does not measure, appraise or audit files, but can be
enabled at runtime by specifying a builtin policy on the boot command line
or by loading a custom policy.

This patch defines a build time policy, which verifies kernel modules,
firmware, kexec image, and/or the IMA policy signatures.  This build time
policy is automatically enabled at runtime and persists after loading a
custom policy.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 6a8f67714c83..004919d9bf09 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -156,6 +156,64 @@ config IMA_APPRAISE
 	  <http://linux-ima.sourceforge.net>
 	  If unsure, say N.
 
+config IMA_APPRAISE_BUILD_POLICY
+	bool "IMA build time configured policy rules"
+	depends on IMA_APPRAISE && INTEGRITY_ASYMMETRIC_KEYS
+	default n
+	help
+	  This option defines an IMA appraisal policy at build time, which
+	  is enforced at run time without having to specify a builtin
+	  policy name on the boot command line.  The build time appraisal
+	  policy rules persist after loading a custom policy.
+
+	  Depending on the rules configured, this policy may require kernel
+	  modules, firmware, the kexec kernel image, and/or the IMA policy
+	  to be signed.  Unsigned files might prevent the system from
+	  booting or applications from working properly.
+
+config IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
+	bool "Appraise firmware signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  This option defines a policy requiring all firmware to be signed,
+	  including the regulatory.db.  If both this option and
+	  CFG80211_REQUIRE_SIGNED_REGDB are enabled, then both signature
+	  verification methods are necessary.
+
+config IMA_APPRAISE_REQUIRE_KEXEC_SIGS
+	bool "Appraise kexec kernel image signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require all kexec'ed kernel images to
+	  be signed and verified by a public key on the trusted IMA
+	  keyring.
+
+	  Kernel image signatures can not be verified by the original
+	  kexec_load syscall.  Enabling this rule will prevent its
+	  usage.
+
+config IMA_APPRAISE_REQUIRE_MODULE_SIGS
+	bool "Appraise kernel modules signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require all kernel modules to be signed
+	  and verified by a public key on the trusted IMA keyring.
+
+	  Kernel module signatures can only be verified by IMA-appraisal,
+	  via the finit_module syscall. Enabling this rule will prevent
+	  the usage of the init_module syscall.
+
+config IMA_APPRAISE_REQUIRE_POLICY_SIGS
+	bool "Appraise IMA policy signature"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require the IMA policy to be signed and
+	  and verified by a key on the trusted IMA keyring.
+
 config IMA_APPRAISE_BOOTPARAM
 	bool "ima_appraise boot parameter"
 	depends on IMA_APPRAISE