[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, 46 insertions, 0 deletions

diff --git a/crypto/ablkcipher.c b/crypto/ablkcipher.c
index 0083140304d2..e403d8137ecd 100644
--- a/crypto/ablkcipher.c
+++ b/crypto/ablkcipher.c
@@ -107,6 +107,52 @@ const struct crypto_type crypto_ablkcipher_type = {
 };
 EXPORT_SYMBOL_GPL(crypto_ablkcipher_type);
 
+static int no_givdecrypt(struct skcipher_givcrypt_request *req)
+{
+        return -ENOSYS;
+}
+
+static int crypto_init_givcipher_ops(struct crypto_tfm *tfm, u32 type,
+                                      u32 mask)
+{
+        struct ablkcipher_alg *alg = &tfm->__crt_alg->cra_ablkcipher;
+        struct ablkcipher_tfm *crt = &tfm->crt_ablkcipher;
+
+        if (alg->ivsize > PAGE_SIZE / 8)
+                return -EINVAL;
+
+        crt->setkey = setkey;
+        crt->encrypt = alg->encrypt;
+        crt->decrypt = alg->decrypt;
+        crt->givencrypt = alg->givencrypt;
+        crt->givdecrypt = alg->givdecrypt ?: no_givdecrypt;
+        crt->ivsize = alg->ivsize;
+
+        return 0;
+}
+
+static void crypto_givcipher_show(struct seq_file *m, struct crypto_alg *alg)
+        __attribute__ ((unused));
+static void crypto_givcipher_show(struct seq_file *m, struct crypto_alg *alg)
+{
+        struct ablkcipher_alg *ablkcipher = &alg->cra_ablkcipher;
+
+        seq_printf(m, "type         : givcipher\n");
+        seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
+        seq_printf(m, "min keysize  : %u\n", ablkcipher->min_keysize);
+        seq_printf(m, "max keysize  : %u\n", ablkcipher->max_keysize);
+        seq_printf(m, "ivsize       : %u\n", ablkcipher->ivsize);
+}
+
+const struct crypto_type crypto_givcipher_type = {
+        .ctxsize = crypto_ablkcipher_ctxsize,
+        .init = crypto_init_givcipher_ops,
+#ifdef CONFIG_PROC_FS
+        .show = crypto_givcipher_show,
+#endif
+};
+EXPORT_SYMBOL_GPL(crypto_givcipher_type);
+
 int crypto_grab_skcipher(struct crypto_skcipher_spawn *spawn, const char *name,
                          u32 type, u32 mask)
 {