crypto: cbc - Export CBC implementation

This patch moves the core CBC implementation into a header file
so that it can be reused by drivers implementing CBC.

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

1 files changed, 146 insertions, 0 deletions

diff --git a/include/crypto/cbc.h b/include/crypto/cbc.h
new file mode 100644
index 000000000000..f5b8bfc22e6d
--- /dev/null
+++ b/include/crypto/cbc.h
@@ -0,0 +1,146 @@
+/*
+ * CBC: Cipher Block Chaining mode
+ *
+ * Copyright (c) 2016 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_CBC_H
+#define _CRYPTO_CBC_H
+
+#include <crypto/internal/skcipher.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+static inline int crypto_cbc_encrypt_segment(
+	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
+	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
+{
+	unsigned int bsize = crypto_skcipher_blocksize(tfm);
+	unsigned int nbytes = walk->nbytes;
+	u8 *src = walk->src.virt.addr;
+	u8 *dst = walk->dst.virt.addr;
+	u8 *iv = walk->iv;
+
+	do {
+		crypto_xor(iv, src, bsize);
+		fn(tfm, iv, dst);
+		memcpy(iv, dst, bsize);
+
+		src += bsize;
+		dst += bsize;
+	} while ((nbytes -= bsize) >= bsize);
+
+	return nbytes;
+}
+
+static inline int crypto_cbc_encrypt_inplace(
+	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
+	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
+{
+	unsigned int bsize = crypto_skcipher_blocksize(tfm);
+	unsigned int nbytes = walk->nbytes;
+	u8 *src = walk->src.virt.addr;
+	u8 *iv = walk->iv;
+
+	do {
+		crypto_xor(src, iv, bsize);
+		fn(tfm, src, src);
+		iv = src;
+
+		src += bsize;
+	} while ((nbytes -= bsize) >= bsize);
+
+	memcpy(walk->iv, iv, bsize);
+
+	return nbytes;
+}
+
+static inline int crypto_cbc_encrypt_walk(struct skcipher_request *req,
+					  void (*fn)(struct crypto_skcipher *,
+						     const u8 *, u8 *))
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct skcipher_walk walk;
+	int err;
+
+	err = skcipher_walk_virt(&walk, req, false);
+
+	while (walk.nbytes) {
+		if (walk.src.virt.addr == walk.dst.virt.addr)
+			err = crypto_cbc_encrypt_inplace(&walk, tfm, fn);
+		else
+			err = crypto_cbc_encrypt_segment(&walk, tfm, fn);
+		err = skcipher_walk_done(&walk, err);
+	}
+
+	return err;
+}
+
+static inline int crypto_cbc_decrypt_segment(
+	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
+	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
+{
+	unsigned int bsize = crypto_skcipher_blocksize(tfm);
+	unsigned int nbytes = walk->nbytes;
+	u8 *src = walk->src.virt.addr;
+	u8 *dst = walk->dst.virt.addr;
+	u8 *iv = walk->iv;
+
+	do {
+		fn(tfm, src, dst);
+		crypto_xor(dst, iv, bsize);
+		iv = src;
+
+		src += bsize;
+		dst += bsize;
+	} while ((nbytes -= bsize) >= bsize);
+
+	memcpy(walk->iv, iv, bsize);
+
+	return nbytes;
+}
+
+static inline int crypto_cbc_decrypt_inplace(
+	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
+	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
+{
+	unsigned int bsize = crypto_skcipher_blocksize(tfm);
+	unsigned int nbytes = walk->nbytes;
+	u8 *src = walk->src.virt.addr;
+	u8 last_iv[bsize];
+
+	/* Start of the last block. */
+	src += nbytes - (nbytes & (bsize - 1)) - bsize;
+	memcpy(last_iv, src, bsize);
+
+	for (;;) {
+		fn(tfm, src, src);
+		if ((nbytes -= bsize) < bsize)
+			break;
+		crypto_xor(src, src - bsize, bsize);
+		src -= bsize;
+	}
+
+	crypto_xor(src, walk->iv, bsize);
+	memcpy(walk->iv, last_iv, bsize);
+
+	return nbytes;
+}
+
+static inline int crypto_cbc_decrypt_blocks(
+	struct skcipher_walk *walk, struct crypto_skcipher *tfm,
+	void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
+{
+	if (walk->src.virt.addr == walk->dst.virt.addr)
+		return crypto_cbc_decrypt_inplace(walk, tfm, fn);
+	else
+		return crypto_cbc_decrypt_segment(walk, tfm, fn);
+}
+
+#endif	/* _CRYPTO_CBC_H */