diff options
Diffstat (limited to 'crypto/cts.c')
| -rw-r--r-- | crypto/cts.c | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/crypto/cts.c b/crypto/cts.c new file mode 100644 index 000000000..8f604f655 --- /dev/null +++ b/crypto/cts.c @@ -0,0 +1,410 @@ +/* + * 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_instance *inst; + struct skcipher_alg *alg; + 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(spawn); + + err = -EINVAL; + if (crypto_skcipher_alg_ivsize(alg) != 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 = 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) { +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); +} + +subsys_initcall(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"); |