| /* |
| * 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/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> |
| |
| 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; |
| int err; |
| |
| crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); |
| crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) & |
| CRYPTO_TFM_REQ_MASK); |
| err = crypto_skcipher_setkey(child, key, keylen); |
| crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) & |
| CRYPTO_TFM_RES_MASK); |
| return err; |
| } |
| |
| static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err) |
| { |
| struct skcipher_request *req = areq->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[bsize * 2] __attribute__ ((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(struct crypto_async_request *areq, int err) |
| { |
| struct skcipher_request *req = areq->data; |
| |
| if (err) |
| goto out; |
| |
| err = cts_cbc_encrypt(req); |
| if (err == -EINPROGRESS || |
| (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) |
| 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; |
| int cbc_blocks = (nbytes + bsize - 1) / bsize - 1; |
| unsigned int offset; |
| |
| skcipher_request_set_tfm(subreq, ctx->child); |
| |
| if (cbc_blocks <= 0) { |
| 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 = cbc_blocks * 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[bsize * 2] __attribute__ ((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(struct crypto_async_request *areq, int err) |
| { |
| struct skcipher_request *req = areq->data; |
| |
| if (err) |
| goto out; |
| |
| err = cts_cbc_decrypt(req); |
| if (err == -EINPROGRESS || |
| (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG)) |
| 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; |
| int cbc_blocks = (nbytes + bsize - 1) / bsize - 1; |
| unsigned int offset; |
| u8 *space; |
| |
| skcipher_request_set_tfm(subreq, ctx->child); |
| |
| if (cbc_blocks <= 0) { |
| 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 = cbc_blocks * bsize; |
| rctx->offset = offset; |
| |
| if (cbc_blocks <= 1) |
| 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_skcipher2(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_instance *inst; |
| struct crypto_attr_type *algt; |
| struct skcipher_alg *alg; |
| const char *cipher_name; |
| int err; |
| |
| algt = crypto_get_attr_type(tb); |
| if (IS_ERR(algt)) |
| return PTR_ERR(algt); |
| |
| if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask) |
| return -EINVAL; |
| |
| cipher_name = crypto_attr_alg_name(tb[1]); |
| if (IS_ERR(cipher_name)) |
| return PTR_ERR(cipher_name); |
| |
| inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); |
| if (!inst) |
| return -ENOMEM; |
| |
| spawn = skcipher_instance_ctx(inst); |
| |
| crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst)); |
| err = crypto_grab_skcipher2(spawn, cipher_name, 0, |
| crypto_requires_sync(algt->type, |
| algt->mask)); |
| if (err) |
| goto err_free_inst; |
| |
| alg = crypto_spawn_skcipher_alg(spawn); |
| |
| err = -EINVAL; |
| if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize) |
| goto err_drop_spawn; |
| |
| if (strncmp(alg->base.cra_name, "cbc(", 4)) |
| goto err_drop_spawn; |
| |
| err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts", |
| &alg->base); |
| if (err) |
| goto err_drop_spawn; |
| |
| inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC; |
| 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; |
| |
| /* We access the data as u32s when xoring. */ |
| inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; |
| |
| inst->alg.ivsize = alg->base.cra_blocksize; |
| inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg); |
| inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg); |
| inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg); |
| |
| 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) |
| goto err_drop_spawn; |
| |
| out: |
| return err; |
| |
| err_drop_spawn: |
| crypto_drop_skcipher(spawn); |
| err_free_inst: |
| kfree(inst); |
| goto out; |
| } |
| |
| 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"); |