/* * 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 <crypto/internal/skcipher.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>#include <linux/compiler.h> struct crypto_cts_ctx {	struct crypto_skcipher *child;}; struct crypto_cts_reqctx {	struct scatterlist sg[2];	unsigned offset;	struct skcipher_request subreq;}; static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req){	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);	struct crypto_skcipher *child = ctx->child; 	return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),			 crypto_skcipher_alignmask(tfm) + 1);} static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key,			     unsigned int keylen){	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);	struct crypto_skcipher *child = ctx->child; 	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &					 CRYPTO_TFM_REQ_MASK);	return crypto_skcipher_setkey(child, key, keylen);} static void cts_cbc_crypt_done(void *data, int err){	struct skcipher_request *req = data; 	if (err == -EINPROGRESS)		return; 	skcipher_request_complete(req, err);} static int cts_cbc_encrypt(struct skcipher_request *req){	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);	struct skcipher_request *subreq = &rctx->subreq;	int bsize = crypto_skcipher_blocksize(tfm);	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));	struct scatterlist *sg;	unsigned int offset;	int lastn; 	offset = rctx->offset;	lastn = req->cryptlen - offset; 	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0); 	memset(d, 0, bsize);	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0); 	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);	memzero_explicit(d, sizeof(d)); 	skcipher_request_set_callback(subreq, req->base.flags &					      CRYPTO_TFM_REQ_MAY_BACKLOG,				      cts_cbc_crypt_done, req);	skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);	return crypto_skcipher_encrypt(subreq);} static void crypto_cts_encrypt_done(void *data, int err){	struct skcipher_request *req = data; 	if (err)		goto out; 	err = cts_cbc_encrypt(req);	if (err == -EINPROGRESS || err == -EBUSY)		return; out:	skcipher_request_complete(req, err);} static int crypto_cts_encrypt(struct skcipher_request *req){	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);	struct skcipher_request *subreq = &rctx->subreq;	int bsize = crypto_skcipher_blocksize(tfm);	unsigned int nbytes = req->cryptlen;	unsigned int offset; 	skcipher_request_set_tfm(subreq, ctx->child); 	if (nbytes < bsize)		return -EINVAL; 	if (nbytes == bsize) {		skcipher_request_set_callback(subreq, req->base.flags,					      req->base.complete,					      req->base.data);		skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,					   req->iv);		return crypto_skcipher_encrypt(subreq);	} 	offset = rounddown(nbytes - 1, bsize);	rctx->offset = offset; 	skcipher_request_set_callback(subreq, req->base.flags,				      crypto_cts_encrypt_done, req);	skcipher_request_set_crypt(subreq, req->src, req->dst,				   offset, req->iv); 	return crypto_skcipher_encrypt(subreq) ?:	       cts_cbc_encrypt(req);} static int cts_cbc_decrypt(struct skcipher_request *req){	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);	struct skcipher_request *subreq = &rctx->subreq;	int bsize = crypto_skcipher_blocksize(tfm);	u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32));	struct scatterlist *sg;	unsigned int offset;	u8 *space;	int lastn; 	offset = rctx->offset;	lastn = req->cryptlen - offset; 	sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize); 	/* 1. Decrypt Cn-1 (s) to create Dn */	scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);	space = crypto_cts_reqctx_space(req);	crypto_xor(d + bsize, space, bsize);	/* 2. Pad Cn with zeros at the end to create C of length BB */	memset(d, 0, bsize);	scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);	/* 3. Exclusive-or Dn with C to create Xn */	/* 4. Select the first Ln bytes of Xn to create Pn */	crypto_xor(d + bsize, d, lastn); 	/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */	memcpy(d + lastn, d + bsize + lastn, bsize - lastn);	/* 6. Decrypt En to create Pn-1 */ 	scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);	memzero_explicit(d, sizeof(d)); 	skcipher_request_set_callback(subreq, req->base.flags &					      CRYPTO_TFM_REQ_MAY_BACKLOG,				      cts_cbc_crypt_done, req); 	skcipher_request_set_crypt(subreq, sg, sg, bsize, space);	return crypto_skcipher_decrypt(subreq);} static void crypto_cts_decrypt_done(void *data, int err){	struct skcipher_request *req = data; 	if (err)		goto out; 	err = cts_cbc_decrypt(req);	if (err == -EINPROGRESS || err == -EBUSY)		return; out:	skcipher_request_complete(req, err);} static int crypto_cts_decrypt(struct skcipher_request *req){	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);	struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);	struct skcipher_request *subreq = &rctx->subreq;	int bsize = crypto_skcipher_blocksize(tfm);	unsigned int nbytes = req->cryptlen;	unsigned int offset;	u8 *space; 	skcipher_request_set_tfm(subreq, ctx->child); 	if (nbytes < bsize)		return -EINVAL; 	if (nbytes == bsize) {		skcipher_request_set_callback(subreq, req->base.flags,					      req->base.complete,					      req->base.data);		skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,					   req->iv);		return crypto_skcipher_decrypt(subreq);	} 	skcipher_request_set_callback(subreq, req->base.flags,				      crypto_cts_decrypt_done, req); 	space = crypto_cts_reqctx_space(req); 	offset = rounddown(nbytes - 1, bsize);	rctx->offset = offset; 	if (offset <= bsize)		memcpy(space, req->iv, bsize);	else		scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,					 bsize, 0); 	skcipher_request_set_crypt(subreq, req->src, req->dst,				   offset, req->iv); 	return crypto_skcipher_decrypt(subreq) ?:	       cts_cbc_decrypt(req);} static int crypto_cts_init_tfm(struct crypto_skcipher *tfm){	struct skcipher_instance *inst = skcipher_alg_instance(tfm);	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);	struct crypto_skcipher *cipher;	unsigned reqsize;	unsigned bsize;	unsigned align; 	cipher = crypto_spawn_skcipher(spawn);	if (IS_ERR(cipher))		return PTR_ERR(cipher); 	ctx->child = cipher; 	align = crypto_skcipher_alignmask(tfm);	bsize = crypto_skcipher_blocksize(cipher);	reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +			crypto_skcipher_reqsize(cipher),			crypto_tfm_ctx_alignment()) +		  (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize; 	crypto_skcipher_set_reqsize(tfm, reqsize); 	return 0;} static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm){	struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); 	crypto_free_skcipher(ctx->child);} static void crypto_cts_free(struct skcipher_instance *inst){	crypto_drop_skcipher(skcipher_instance_ctx(inst));	kfree(inst);} static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb){	struct crypto_skcipher_spawn *spawn;	struct skcipher_alg_common *alg;	struct skcipher_instance *inst;	u32 mask;	int err; 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);	if (err)		return err; 	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);	if (!inst)		return -ENOMEM; 	spawn = skcipher_instance_ctx(inst); 	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),				   crypto_attr_alg_name(tb[1]), 0, mask);	if (err)		goto err_free_inst; 	alg = crypto_spawn_skcipher_alg_common(spawn); 	err = -EINVAL;	if (alg->ivsize != alg->base.cra_blocksize)		goto err_free_inst; 	if (strncmp(alg->base.cra_name, "cbc(", 4))		goto err_free_inst; 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",				  &alg->base);	if (err)		goto err_free_inst; 	inst->alg.base.cra_priority = alg->base.cra_priority;	inst->alg.base.cra_blocksize = alg->base.cra_blocksize;	inst->alg.base.cra_alignmask = alg->base.cra_alignmask; 	inst->alg.ivsize = alg->base.cra_blocksize;	inst->alg.chunksize = alg->chunksize;	inst->alg.min_keysize = alg->min_keysize;	inst->alg.max_keysize = alg->max_keysize; 	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx); 	inst->alg.init = crypto_cts_init_tfm;	inst->alg.exit = crypto_cts_exit_tfm; 	inst->alg.setkey = crypto_cts_setkey;	inst->alg.encrypt = crypto_cts_encrypt;	inst->alg.decrypt = crypto_cts_decrypt; 	inst->free = crypto_cts_free; 	err = skcipher_register_instance(tmpl, inst);	if (err) {err_free_inst:		crypto_cts_free(inst);	}	return err;} static struct crypto_template crypto_cts_tmpl = {	.name = "cts",	.create = crypto_cts_create,	.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");MODULE_ALIAS_CRYPTO("cts");