[PATCH 01/15] crypto: skcipher - Add tailsize attribute

[Herbert Xu <herbert@gondor.apana.org.au>]

This patch adds a new tailsize attribute to skcipher and lskcipher
algorithms.  This will be used by algorithms such as CTS which may
need to withhold a number of blocks until the end has been reached.

When issuing a NOTFINAL request, the user must ensure that at least
tailsize bytes will be supplied later on a final request.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 crypto/lskcipher.c                 |  1 +
 crypto/skcipher.c                  | 16 ++++++++++++++-
 include/crypto/internal/skcipher.h |  1 +
 include/crypto/skcipher.h          | 33 ++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/crypto/lskcipher.c b/crypto/lskcipher.c
index 0b6dd8aa21f2..2a602911f4fc 100644
--- a/crypto/lskcipher.c
+++ b/crypto/lskcipher.c
@@ -300,6 +300,7 @@ static void __maybe_unused crypto_lskcipher_show(
 	seq_printf(m, "ivsize       : %u\n", skcipher->co.ivsize);
 	seq_printf(m, "chunksize    : %u\n", skcipher->co.chunksize);
 	seq_printf(m, "statesize    : %u\n", skcipher->co.statesize);
+	seq_printf(m, "tailsize     : %u\n", skcipher->co.tailsize);
 }
 
 static int __maybe_unused crypto_lskcipher_report(
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index bc70e159d27d..600ec5735ce0 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -368,10 +368,21 @@ static int skcipher_walk_next(struct skcipher_walk *walk)
 			 SKCIPHER_WALK_DIFF);
 
 	n = walk->total;
-	bsize = min(walk->stride, max(n, walk->blocksize));
+
+	bsize = max(n, walk->blocksize);
+	if (n > walk->tailsize)
+		bsize = min(walk->stride, bsize);
+
 	n = scatterwalk_clamp(&walk->in, n);
 	n = scatterwalk_clamp(&walk->out, n);
 
+	/* Retain tail if necessary. */
+	if (walk->tailsize < walk->total && walk->total - n < walk->tailsize) {
+		/* Process at least one block. */
+		n = min(n, bsize);
+		n = max(n, walk->total - walk->tailsize);
+	}
+
 	if (unlikely(n < bsize)) {
 		if (unlikely(walk->total < walk->blocksize))
 			return skcipher_walk_done(walk, -EINVAL);
@@ -487,6 +498,7 @@ static int skcipher_walk_skcipher(struct skcipher_walk *walk,
 	walk->blocksize = crypto_skcipher_blocksize(tfm);
 	walk->ivsize = crypto_skcipher_ivsize(tfm);
 	walk->alignmask = crypto_skcipher_alignmask(tfm);
+	walk->tailsize = crypto_skcipher_tailsize(tfm);
 
 	if (alg->co.base.cra_type != &crypto_skcipher_type)
 		walk->stride = alg->co.chunksize;
@@ -824,6 +836,7 @@ static void crypto_skcipher_show(struct seq_file *m, struct crypto_alg *alg)
 	seq_printf(m, "chunksize    : %u\n", skcipher->chunksize);
 	seq_printf(m, "walksize     : %u\n", skcipher->walksize);
 	seq_printf(m, "statesize    : %u\n", skcipher->statesize);
+	seq_printf(m, "tailsize     : %u\n", skcipher->tailsize);
 }
 
 static int __maybe_unused crypto_skcipher_report(
@@ -939,6 +952,7 @@ int skcipher_prepare_alg_common(struct skcipher_alg_common *alg)
 	struct crypto_alg *base = &alg->base;
 
 	if (alg->ivsize > PAGE_SIZE / 8 || alg->chunksize > PAGE_SIZE / 8 ||
+	    alg->tailsize > PAGE_SIZE / 8 ||
 	    alg->statesize > PAGE_SIZE / 2 ||
 	    (alg->ivsize + alg->statesize) > PAGE_SIZE / 2)
 		return -EINVAL;
diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index 7ae42afdcf3e..1e35e7719b22 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -86,6 +86,7 @@ struct skcipher_walk {
 	int flags;
 	unsigned int blocksize;
 	unsigned int stride;
+	unsigned int tailsize;
 	unsigned int alignmask;
 };
 
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index c8857d7bdb37..6223d81fed76 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -103,6 +103,8 @@ struct crypto_istat_cipher {
  * @chunksize: Equal to the block size except for stream ciphers such as
  *	       CTR where it is set to the underlying block size.
  * @statesize: Size of the internal state for the algorithm.
+ * @tailsize: Minimum number of bytes to withhold until the end of operation.
+ *	      Used by algorithms such as CTS to support chaining.
  * @stat: Statistics for cipher algorithm
  * @base: Definition of a generic crypto algorithm.
  */
@@ -112,6 +114,7 @@ struct crypto_istat_cipher {
 	unsigned int ivsize;		\
 	unsigned int chunksize;		\
 	unsigned int statesize;		\
+	unsigned int tailsize;		\
 					\
 	SKCIPHER_ALG_COMMON_STAT	\
 					\
@@ -543,6 +546,36 @@ static inline unsigned int crypto_lskcipher_statesize(
 	return crypto_lskcipher_alg(tfm)->co.statesize;
 }
 
+/**
+ * crypto_skcipher_tailsize() - obtain tail size
+ * @tfm: cipher handle
+ *
+ * Some algorithms need to withhold a number of blocks until the end.
+ * The tail size specifies how many bytes to withhold.
+ *
+ * Return: tail size in bytes
+ */
+static inline unsigned int crypto_skcipher_tailsize(
+	struct crypto_skcipher *tfm)
+{
+	return crypto_skcipher_alg_common(tfm)->tailsize;
+}
+
+/**
+ * crypto_lskcipher_tailsize() - obtain tail size
+ * @tfm: cipher handle
+ *
+ * Some algorithms need to withhold a number of blocks until the end.
+ * The tail size specifies how many bytes to withhold.
+ *
+ * Return: tail size in bytes
+ */
+static inline unsigned int crypto_lskcipher_tailsize(
+	struct crypto_lskcipher *tfm)
+{
+	return crypto_lskcipher_alg(tfm)->co.tailsize;
+}
+
 static inline unsigned int crypto_sync_skcipher_blocksize(
 	struct crypto_sync_skcipher *tfm)
 {
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt