/* * 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 <herbert@gondor.apana.org.au> */ /* * 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; 	sg_init_table(sgsrc, 1);	sg_init_table(sgdst, 1); 	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; 	sg_init_table(sgsrc, 1);	sg_init_table(sgdst, 1); 	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");