[CRYPTO] cts: Add CTS mode required for Kerberos AES support

Implement CTS wrapper for CBC mode required for support of AES encryption support for Kerberos (rfc3962). Signed-off-by: Kevin Coffman <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
ambv · Apr 21, 2008 · 76cb952 · 76cb952
1 parent fd4609a
commit 76cb952
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Showing 5 changed files with 582 additions and 2 deletions.
diff --git a/crypto/Kconfig b/crypto/Kconfig
@@ -213,6 +213,17 @@ config CRYPTO_CTR
 	  CTR: Counter mode
 	  This block cipher algorithm is required for IPSec.
 
+config CRYPTO_CTS
+	tristate "CTS support"
+	select CRYPTO_BLKCIPHER
+	help
+	  CTS: Cipher Text Stealing
+	  This is the Cipher Text Stealing mode as described by
+	  Section 8 of rfc2040 and referenced by rfc3962.
+	  (rfc3962 includes errata information in its Appendix A)
+	  This mode is required for Kerberos gss mechanism support
+	  for AES encryption.
+
 config CRYPTO_GCM
 	tristate "GCM/GMAC support"
 	select CRYPTO_CTR

diff --git a/crypto/Makefile b/crypto/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_CRYPTO_GF128MUL) += gf128mul.o
 obj-$(CONFIG_CRYPTO_ECB) += ecb.o
 obj-$(CONFIG_CRYPTO_CBC) += cbc.o
 obj-$(CONFIG_CRYPTO_PCBC) += pcbc.o
+obj-$(CONFIG_CRYPTO_CTS) += cts.o
 obj-$(CONFIG_CRYPTO_LRW) += lrw.o
 obj-$(CONFIG_CRYPTO_XTS) += xts.o
 obj-$(CONFIG_CRYPTO_CTR) += ctr.o

diff --git a/crypto/cts.c b/crypto/cts.c
@@ -0,0 +1,347 @@
+/*
+ * CTS: Cipher Text Stealing mode
+ *
+ * COPYRIGHT (c) 2008
+ * The Regents of the University of Michigan
+ * ALL RIGHTS RESERVED
+ *
+ * Permission is granted to use, copy, create derivative works
+ * and redistribute this software and such derivative works
+ * for any purpose, so long as the name of The University of
+ * Michigan is not used in any advertising or publicity
+ * pertaining to the use of distribution of this software
+ * without specific, written prior authorization.  If the
+ * above copyright notice or any other identification of the
+ * University of Michigan is included in any copy of any
+ * portion of this software, then the disclaimer below must
+ * also be included.
+ *
+ * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
+ * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
+ * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
+ * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
+ * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
+ * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
+ * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
+ * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
+ * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGES.
+ */
+
+/* Derived from various:
+ *	Copyright (c) 2006 Herbert Xu <[email protected]>
+ */
+
+/*
+ * This is the Cipher Text Stealing mode as described by
+ * Section 8 of rfc2040 and referenced by rfc3962.
+ * rfc3962 includes errata information in its Appendix A.
+ */
+
+#include <crypto/algapi.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/log2.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <crypto/scatterwalk.h>
+#include <linux/slab.h>
+
+struct crypto_cts_ctx {
+	struct crypto_blkcipher *child;
+};
+
+static int crypto_cts_setkey(struct crypto_tfm *parent, const u8 *key,
+			     unsigned int keylen)
+{
+	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(parent);
+	struct crypto_blkcipher *child = ctx->child;
+	int err;
+
+	crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
+	crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
+				       CRYPTO_TFM_REQ_MASK);
+	err = crypto_blkcipher_setkey(child, key, keylen);
+	crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
+				     CRYPTO_TFM_RES_MASK);
+	return err;
+}
+
+static int cts_cbc_encrypt(struct crypto_cts_ctx *ctx,
+			   struct blkcipher_desc *desc,
+			   struct scatterlist *dst,
+			   struct scatterlist *src,
+			   unsigned int offset,
+			   unsigned int nbytes)
+{
+	int bsize = crypto_blkcipher_blocksize(desc->tfm);
+	u8 tmp[bsize], tmp2[bsize];
+	struct blkcipher_desc lcldesc;
+	struct scatterlist sgsrc[1], sgdst[1];
+	int lastn = nbytes - bsize;
+	u8 iv[bsize];
+	u8 s[bsize * 2], d[bsize * 2];
+	int err;
+
+	if (lastn < 0)
+		return -EINVAL;
+
+	memset(s, 0, sizeof(s));
+	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
+
+	memcpy(iv, desc->info, bsize);
+
+	lcldesc.tfm = ctx->child;
+	lcldesc.info = iv;
+	lcldesc.flags = desc->flags;
+
+	sg_set_buf(&sgsrc[0], s, bsize);
+	sg_set_buf(&sgdst[0], tmp, bsize);
+	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
+
+	memcpy(d + bsize, tmp, lastn);
+
+	lcldesc.info = tmp;
+
+	sg_set_buf(&sgsrc[0], s + bsize, bsize);
+	sg_set_buf(&sgdst[0], tmp2, bsize);
+	err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
+
+	memcpy(d, tmp2, bsize);
+
+	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
+
+	memcpy(desc->info, tmp2, bsize);
+
+	return err;
+}
+
+static int crypto_cts_encrypt(struct blkcipher_desc *desc,
+			      struct scatterlist *dst, struct scatterlist *src,
+			      unsigned int nbytes)
+{
+	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
+	int bsize = crypto_blkcipher_blocksize(desc->tfm);
+	int tot_blocks = (nbytes + bsize - 1) / bsize;
+	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
+	struct blkcipher_desc lcldesc;
+	int err;
+
+	lcldesc.tfm = ctx->child;
+	lcldesc.info = desc->info;
+	lcldesc.flags = desc->flags;
+
+	if (tot_blocks == 1) {
+		err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src, bsize);
+	} else if (nbytes <= bsize * 2) {
+		err = cts_cbc_encrypt(ctx, desc, dst, src, 0, nbytes);
+	} else {
+		/* do normal function for tot_blocks - 2 */
+		err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src,
+							cbc_blocks * bsize);
+		if (err == 0) {
+			/* do cts for final two blocks */
+			err = cts_cbc_encrypt(ctx, desc, dst, src,
+						cbc_blocks * bsize,
+						nbytes - (cbc_blocks * bsize));
+		}
+	}
+
+	return err;
+}
+
+static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
+			   struct blkcipher_desc *desc,
+			   struct scatterlist *dst,
+			   struct scatterlist *src,
+			   unsigned int offset,
+			   unsigned int nbytes)
+{
+	int bsize = crypto_blkcipher_blocksize(desc->tfm);
+	u8 tmp[bsize];
+	struct blkcipher_desc lcldesc;
+	struct scatterlist sgsrc[1], sgdst[1];
+	int lastn = nbytes - bsize;
+	u8 iv[bsize];
+	u8 s[bsize * 2], d[bsize * 2];
+	int err;
+
+	if (lastn < 0)
+		return -EINVAL;
+
+	scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
+
+	lcldesc.tfm = ctx->child;
+	lcldesc.info = iv;
+	lcldesc.flags = desc->flags;
+
+	/* 1. Decrypt Cn-1 (s) to create Dn (tmp)*/
+	memset(iv, 0, sizeof(iv));
+	sg_set_buf(&sgsrc[0], s, bsize);
+	sg_set_buf(&sgdst[0], tmp, bsize);
+	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
+	if (err)
+		return err;
+	/* 2. Pad Cn with zeros at the end to create C of length BB */
+	memset(iv, 0, sizeof(iv));
+	memcpy(iv, s + bsize, lastn);
+	/* 3. Exclusive-or Dn (tmp) with C (iv) to create Xn (tmp) */
+	crypto_xor(tmp, iv, bsize);
+	/* 4. Select the first Ln bytes of Xn (tmp) to create Pn */
+	memcpy(d + bsize, tmp, lastn);
+
+	/* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
+	memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
+	/* 6. Decrypt En to create Pn-1 */
+	memset(iv, 0, sizeof(iv));
+	sg_set_buf(&sgsrc[0], s + bsize, bsize);
+	sg_set_buf(&sgdst[0], d, bsize);
+	err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
+
+	/* XOR with previous block */
+	crypto_xor(d, desc->info, bsize);
+
+	scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
+
+	memcpy(desc->info, s, bsize);
+	return err;
+}
+
+static int crypto_cts_decrypt(struct blkcipher_desc *desc,
+			      struct scatterlist *dst, struct scatterlist *src,
+			      unsigned int nbytes)
+{
+	struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
+	int bsize = crypto_blkcipher_blocksize(desc->tfm);
+	int tot_blocks = (nbytes + bsize - 1) / bsize;
+	int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
+	struct blkcipher_desc lcldesc;
+	int err;
+
+	lcldesc.tfm = ctx->child;
+	lcldesc.info = desc->info;
+	lcldesc.flags = desc->flags;
+
+	if (tot_blocks == 1) {
+		err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src, bsize);
+	} else if (nbytes <= bsize * 2) {
+		err = cts_cbc_decrypt(ctx, desc, dst, src, 0, nbytes);
+	} else {
+		/* do normal function for tot_blocks - 2 */
+		err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src,
+							cbc_blocks * bsize);
+		if (err == 0) {
+			/* do cts for final two blocks */
+			err = cts_cbc_decrypt(ctx, desc, dst, src,
+						cbc_blocks * bsize,
+						nbytes - (cbc_blocks * bsize));
+		}
+	}
+	return err;
+}
+
+static int crypto_cts_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_instance *inst = (void *)tfm->__crt_alg;
+	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
+	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
+	struct crypto_blkcipher *cipher;
+
+	cipher = crypto_spawn_blkcipher(spawn);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	ctx->child = cipher;
+	return 0;
+}
+
+static void crypto_cts_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
+	crypto_free_blkcipher(ctx->child);
+}
+
+static struct crypto_instance *crypto_cts_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_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
+				  CRYPTO_ALG_TYPE_MASK);
+	err = PTR_ERR(alg);
+	if (IS_ERR(alg))
+		return ERR_PTR(err);
+
+	inst = ERR_PTR(-EINVAL);
+	if (!is_power_of_2(alg->cra_blocksize))
+		goto out_put_alg;
+
+	inst = crypto_alloc_instance("cts", 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;
+	inst->alg.cra_alignmask = alg->cra_alignmask;
+	inst->alg.cra_type = &crypto_blkcipher_type;
+
+	/* We access the data as u32s when xoring. */
+	inst->alg.cra_alignmask |= __alignof__(u32) - 1;
+
+	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
+	inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
+	inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
+
+	inst->alg.cra_blkcipher.geniv = "seqiv";
+
+	inst->alg.cra_ctxsize = sizeof(struct crypto_cts_ctx);
+
+	inst->alg.cra_init = crypto_cts_init_tfm;
+	inst->alg.cra_exit = crypto_cts_exit_tfm;
+
+	inst->alg.cra_blkcipher.setkey = crypto_cts_setkey;
+	inst->alg.cra_blkcipher.encrypt = crypto_cts_encrypt;
+	inst->alg.cra_blkcipher.decrypt = crypto_cts_decrypt;
+
+out_put_alg:
+	crypto_mod_put(alg);
+	return inst;
+}
+
+static void crypto_cts_free(struct crypto_instance *inst)
+{
+	crypto_drop_spawn(crypto_instance_ctx(inst));
+	kfree(inst);
+}
+
+static struct crypto_template crypto_cts_tmpl = {
+	.name = "cts",
+	.alloc = crypto_cts_alloc,
+	.free = crypto_cts_free,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_cts_module_init(void)
+{
+	return crypto_register_template(&crypto_cts_tmpl);
+}
+
+static void __exit crypto_cts_module_exit(void)
+{
+	crypto_unregister_template(&crypto_cts_tmpl);
+}
+
+module_init(crypto_cts_module_init);
+module_exit(crypto_cts_module_exit);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");