dm crypt: support using trusted keys

Commit 27f5411a718c ("dm crypt: support using encrypted keys") extended
dm-crypt to allow use of "encrypted" keys along with "user" and "logon".

Along the same lines, teach dm-crypt to support "trusted" keys as well.

Signed-off-by: Ahmad Fatoum <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

Documentation/admin-guide/device-mapper/dm-crypt.rst

···
     the value passed in <key_size>.
 
 <key_type>
-    Either 'logon', 'user' or 'encrypted' kernel key type.
+    Either 'logon', 'user', 'encrypted' or 'trusted' kernel key type.
 
 <key_description>
     The kernel keyring key description crypt target should look for

drivers/md/Kconfig

···
 	tristate "Crypt target support"
 	depends on BLK_DEV_DM
 	depends on (ENCRYPTED_KEYS || ENCRYPTED_KEYS=n)
+	depends on (TRUSTED_KEYS || TRUSTED_KEYS=n)
 	select CRYPTO
 	select CRYPTO_CBC
 	select CRYPTO_ESSIV

drivers/md/dm-crypt.c

···
 #include <linux/key-type.h>
 #include <keys/user-type.h>
 #include <keys/encrypted-type.h>
+#include <keys/trusted-type.h>
 
 #include <linux/device-mapper.h>
 
···
 	return 0;
 }
 
+static int set_key_trusted(struct crypt_config *cc, struct key *key)
+{
+	const struct trusted_key_payload *tkp;
+
+	tkp = key->payload.data[0];
+	if (!tkp)
+		return -EKEYREVOKED;
+
+	if (cc->key_size != tkp->key_len)
+		return -EINVAL;
+
+	memcpy(cc->key, tkp->key, cc->key_size);
+
+	return 0;
+}
+
 static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string)
 {
 	char *new_key_string, *key_desc;
···
 		   !strncmp(key_string, "encrypted:", key_desc - key_string + 1)) {
 		type = &key_type_encrypted;
 		set_key = set_key_encrypted;
+	} else if (IS_ENABLED(CONFIG_TRUSTED_KEYS) &&
+	           !strncmp(key_string, "trusted:", key_desc - key_string + 1)) {
+		type = &key_type_trusted;
+		set_key = set_key_trusted;
 	} else {
 		return -EINVAL;
 	}
···
 
 static struct target_type crypt_target = {
 	.name   = "crypt",
-	.version = {1, 22, 0},
+	.version = {1, 23, 0},
 	.module = THIS_MODULE,
 	.ctr    = crypt_ctr,
 	.dtr    = crypt_dtr,