[CRYPTO] skcipher: Add givcrypt operations and givcipher type

Different block cipher modes have different requirements for intialisation
vectors.  For example, CBC can use a simple randomly generated IV while
modes such as CTR must use an IV generation mechanisms that give a stronger
guarantee on the lack of collisions.  Furthermore, disk encryption modes
have their own IV generation algorithms.

Up until now IV generation has been left to the users of the symmetric
key cipher API.  This is inconvenient as the number of block cipher modes
increase because the user needs to be aware of which mode is supposed to
be paired with which IV generation algorithm.

Therefore it makes sense to integrate the IV generation into the crypto
API.  This patch takes the first step in that direction by creating two
new ablkcipher operations, givencrypt and givdecrypt that generates an
IV before performing the actual encryption or decryption.

The operations are currently not exposed to the user.  That will be done
once the underlying functionality has actually been implemented.

It also creates the underlying givcipher type.  Algorithms that directly
generate IVs would use it instead of ablkcipher.  All other algorithms
(including all existing ones) would generate a givcipher algorithm upon
registration.  This givcipher algorithm will be constructed from the geniv
string that's stored in every algorithm.  That string will locate a template
which is instantiated by the blkcipher/ablkcipher algorithm in question to
give a givcipher algorithm.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 38 insertions, 0 deletions

diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
new file mode 100644
index 00000000000..c283fab5edd
--- /dev/null
+++ b/include/crypto/skcipher.h
@@ -0,0 +1,38 @@
+/*
+ * Symmetric key ciphers.
+ * 
+ * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option) 
+ * any later version.
+ *
+ */
+
+#ifndef _CRYPTO_SKCIPHER_H
+#define _CRYPTO_SKCIPHER_H
+
+#include <linux/crypto.h>
+
+/**
+ *	struct skcipher_givcrypt_request - Crypto request with IV generation
+ *	@seq: Sequence number for IV generation
+ *	@giv: Space for generated IV
+ *	@creq: The crypto request itself
+ */
+struct skcipher_givcrypt_request {
+	u64 seq;
+	u8 *giv;
+
+	struct ablkcipher_request creq;
+};
+
+static inline struct crypto_ablkcipher *skcipher_givcrypt_reqtfm(
+	struct skcipher_givcrypt_request *req)
+{
+	return crypto_ablkcipher_reqtfm(&req->creq);
+}
+
+#endif	/* _CRYPTO_SKCIPHER_H */
+