1 files changed, 292 insertions, 0 deletions
diff --git a/crypto/xts.c b/crypto/xts.c
new file mode 100644
index 0000000..8eb08bf
--- /dev/null
+++ b/crypto/xts.c
@@ -0,0 +1,292 @@
+/* XTS: as defined in IEEE1619/D16
+ *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
+ *	(sector sizes which are not a multiple of 16 bytes are,
+ *	however currently unsupported)
+ *
+ * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
+ *
+ * Based om ecb.c
+ * Copyright (c) 2006 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.
+ */
+#include <crypto/algapi.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+
+#include <crypto/b128ops.h>
+#include <crypto/gf128mul.h>
+
+struct priv {
+	struct crypto_cipher *child;
+	struct crypto_cipher *tweak;
+};
+
+static int setkey(struct crypto_tfm *parent, const u8 *key,
+		  unsigned int keylen)
+{
+	struct priv *ctx = crypto_tfm_ctx(parent);
+	struct crypto_cipher *child = ctx->tweak;
+	u32 *flags = &parent->crt_flags;
+	int err;
+
+	/* key consists of keys of equal size concatenated, therefore
+	 * the length must be even */
+	if (keylen % 2) {
+		/* tell the user why there was an error */
+		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
+		return -EINVAL;
+	}
+
+	/* we need two cipher instances: one to compute the inital 'tweak'
+	 * by encrypting the IV (usually the 'plain' iv) and the other
+	 * one to encrypt and decrypt the data */
+
+	/* tweak cipher, uses Key2 i.e. the second half of *key */
+	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
+	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
+				       CRYPTO_TFM_REQ_MASK);
+	err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
+	if (err)
+		return err;
+
+	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
+				     CRYPTO_TFM_RES_MASK);
+
+	child = ctx->child;
+
+	/* data cipher, uses Key1 i.e. the first half of *key */
+	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
+	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
+				       CRYPTO_TFM_REQ_MASK);
+	err = crypto_cipher_setkey(child, key, keylen/2);
+	if (err)
+		return err;
+
+	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
+				     CRYPTO_TFM_RES_MASK);
+
+	return 0;
+}
+
+struct sinfo {
+	be128 t;
+	struct crypto_tfm *tfm;
+	void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
+};
+
+static inline void xts_round(struct sinfo *s, void *dst, const void *src)
+{
+	be128_xor(dst, &s->t, src);		/* PP <- T xor P */
+	s->fn(s->tfm, dst, dst);		/* CC <- E(Key1,PP) */
+	be128_xor(dst, dst, &s->t);		/* C <- T xor CC */
+}
+
+static int crypt(struct blkcipher_desc *d,
+		 struct blkcipher_walk *w, struct priv *ctx,
+		 void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
+		 void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
+{
+	int err;
+	unsigned int avail;
+	const int bs = crypto_cipher_blocksize(ctx->child);
+	struct sinfo s = {
+		.tfm = crypto_cipher_tfm(ctx->child),
+		.fn = fn
+	};
+	be128 *iv;
+	u8 *wsrc;
+	u8 *wdst;
+
+	err = blkcipher_walk_virt(d, w);
+	if (!w->nbytes)
+		return err;
+
+	avail = w->nbytes;
+
+	wsrc = w->src.virt.addr;
+	wdst = w->dst.virt.addr;
+
+	/* calculate first value of T */
+	iv = (be128 *)w->iv;
+	tw(crypto_cipher_tfm(ctx->tweak), (void *)&s.t, w->iv);
+
+	goto first;
+
+	for (;;) {
+		do {
+			gf128mul_x_ble(&s.t, &s.t);
+
+first:
+			xts_round(&s, wdst, wsrc);
+
+			wsrc += bs;
+			wdst += bs;
+		} while ((avail -= bs) >= bs);
+
+		err = blkcipher_walk_done(d, w, avail);
+		if (!w->nbytes)
+			break;
+
+		avail = w->nbytes;
+
+		wsrc = w->src.virt.addr;
+		wdst = w->dst.virt.addr;
+	}
+
+	return err;
+}
+
+static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
+		   struct scatterlist *src, unsigned int nbytes)
+{
+	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
+	struct blkcipher_walk w;
+
+	blkcipher_walk_init(&w, dst, src, nbytes);
+	return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
+		     crypto_cipher_alg(ctx->child)->cia_encrypt);
+}
+
+static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
+		   struct scatterlist *src, unsigned int nbytes)
+{
+	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
+	struct blkcipher_walk w;
+
+	blkcipher_walk_init(&w, dst, src, nbytes);
+	return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
+		     crypto_cipher_alg(ctx->child)->cia_decrypt);
+}
+
+static int init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_cipher *cipher;
+	struct crypto_instance *inst = (void *)tfm->__crt_alg;
+	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
+	struct priv *ctx = crypto_tfm_ctx(tfm);
+	u32 *flags = &tfm->crt_flags;
+
+	cipher = crypto_spawn_cipher(spawn);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	if (crypto_cipher_blocksize(cipher) != 16) {
+		*flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
+		crypto_free_cipher(cipher);
+		return -EINVAL;
+	}
+
+	ctx->child = cipher;
+
+	cipher = crypto_spawn_cipher(spawn);
+	if (IS_ERR(cipher)) {
+		crypto_free_cipher(ctx->child);
+		return PTR_ERR(cipher);
+	}
+
+	/* this check isn't really needed, leave it here just in case */
+	if (crypto_cipher_blocksize(cipher) != 16) {
+		crypto_free_cipher(cipher);
+		crypto_free_cipher(ctx->child);
+		*flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
+		return -EINVAL;
+	}
+
+	ctx->tweak = cipher;
+
+	return 0;
+}
+
+static void exit_tfm(struct crypto_tfm *tfm)
+{
+	struct priv *ctx = crypto_tfm_ctx(tfm);
+	crypto_free_cipher(ctx->child);
+	crypto_free_cipher(ctx->tweak);
+}
+
+static struct crypto_instance *alloc(struct rtattr **tb)
+{
+	struct crypto_instance *inst;
+	struct crypto_alg *alg;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
+	if (err)
+		return ERR_PTR(err);
+
+	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
+				  CRYPTO_ALG_TYPE_MASK);
+	if (IS_ERR(alg))
+		return ERR_PTR(PTR_ERR(alg));
+
+	inst = crypto_alloc_instance("xts", alg);
+	if (IS_ERR(inst))
+		goto out_put_alg;
+
+	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
+	inst->alg.cra_priority = alg->cra_priority;
+	inst->alg.cra_blocksize = alg->cra_blocksize;
+
+	if (alg->cra_alignmask < 7)
+		inst->alg.cra_alignmask = 7;
+	else
+		inst->alg.cra_alignmask = alg->cra_alignmask;
+
+	inst->alg.cra_type = &crypto_blkcipher_type;
+
+	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
+	inst->alg.cra_blkcipher.min_keysize =
+		2 * alg->cra_cipher.cia_min_keysize;
+	inst->alg.cra_blkcipher.max_keysize =
+		2 * alg->cra_cipher.cia_max_keysize;
+
+	inst->alg.cra_ctxsize = sizeof(struct priv);
+
+	inst->alg.cra_init = init_tfm;
+	inst->alg.cra_exit = exit_tfm;
+
+	inst->alg.cra_blkcipher.setkey = setkey;
+	inst->alg.cra_blkcipher.encrypt = encrypt;
+	inst->alg.cra_blkcipher.decrypt = decrypt;
+
+out_put_alg:
+	crypto_mod_put(alg);
+	return inst;
+}
+
+static void free(struct crypto_instance *inst)
+{
+	crypto_drop_spawn(crypto_instance_ctx(inst));
+	kfree(inst);
+}
+
+static struct crypto_template crypto_tmpl = {
+	.name = "xts",
+	.alloc = alloc,
+	.free = free,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_module_init(void)
+{
+	return crypto_register_template(&crypto_tmpl);
+}
+
+static void __exit crypto_module_exit(void)
+{
+	crypto_unregister_template(&crypto_tmpl);
+}
+
+module_init(crypto_module_init);
+module_exit(crypto_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("XTS block cipher mode");