integrity: digital signature verification using multiple keyrings

Define separate keyrings for each of the different use cases - evm, ima,
and modules. Using different keyrings improves search performance, and also
allows "locking" specific keyring to prevent adding new keys.
This is useful for evm and module keyrings, when keys are usually only
added from initramfs.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>

security/integrity/Kconfig

@@ -3,5 +3,19 @@ config INTEGRITY
 	def_bool y
 	depends on IMA || EVM
 
+config INTEGRITY_DIGSIG
+	boolean "Digital signature verification using multiple keyrings"
+	depends on INTEGRITY
+	default n
+	select DIGSIG
+	help
+	  This option enables digital signature verification support
+	  using multiple keyrings. It defines separate keyrings for each
+	  of the different use cases - evm, ima, and modules.
+	  Different keyrings improves search performance, but also allow
+	  to "lock" certain keyring to prevent adding new keys.
+	  This is useful for evm and module keyrings, when keys are
+	  usually only added from initramfs.
+
 source security/integrity/ima/Kconfig
 source security/integrity/evm/Kconfig