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410 lines
12 KiB
410 lines
12 KiB
/* |
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* CTS: Cipher Text Stealing mode |
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* |
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* COPYRIGHT (c) 2008 |
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* The Regents of the University of Michigan |
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* ALL RIGHTS RESERVED |
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* |
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* Permission is granted to use, copy, create derivative works |
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* and redistribute this software and such derivative works |
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* for any purpose, so long as the name of The University of |
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* Michigan is not used in any advertising or publicity |
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* pertaining to the use of distribution of this software |
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* without specific, written prior authorization. If the |
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* above copyright notice or any other identification of the |
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* University of Michigan is included in any copy of any |
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* portion of this software, then the disclaimer below must |
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* also be included. |
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* |
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* THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION |
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* FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY |
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* PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF |
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* MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING |
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* WITHOUT LIMITATION THE IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE |
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* REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE |
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* FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR |
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* CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING |
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* OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN |
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* IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGES. |
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*/ |
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/* Derived from various: |
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* Copyright (c) 2006 Herbert Xu <[email protected]> |
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*/ |
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/* |
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* This is the Cipher Text Stealing mode as described by |
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* Section 8 of rfc2040 and referenced by rfc3962. |
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* rfc3962 includes errata information in its Appendix A. |
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*/ |
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#include <crypto/algapi.h> |
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#include <crypto/internal/skcipher.h> |
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#include <linux/err.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/log2.h> |
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#include <linux/module.h> |
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#include <linux/scatterlist.h> |
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#include <crypto/scatterwalk.h> |
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#include <linux/slab.h> |
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#include <linux/compiler.h> |
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struct crypto_cts_ctx { |
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struct crypto_skcipher *child; |
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}; |
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struct crypto_cts_reqctx { |
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struct scatterlist sg[2]; |
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unsigned offset; |
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struct skcipher_request subreq; |
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}; |
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static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req) |
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{ |
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struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
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struct crypto_skcipher *child = ctx->child; |
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return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child), |
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crypto_skcipher_alignmask(tfm) + 1); |
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} |
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static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key, |
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unsigned int keylen) |
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{ |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent); |
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struct crypto_skcipher *child = ctx->child; |
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crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); |
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crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) & |
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CRYPTO_TFM_REQ_MASK); |
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return crypto_skcipher_setkey(child, key, keylen); |
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} |
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static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err) |
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{ |
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struct skcipher_request *req = areq->data; |
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if (err == -EINPROGRESS) |
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return; |
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skcipher_request_complete(req, err); |
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} |
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static int cts_cbc_encrypt(struct skcipher_request *req) |
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{ |
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struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
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struct skcipher_request *subreq = &rctx->subreq; |
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int bsize = crypto_skcipher_blocksize(tfm); |
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u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32)); |
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struct scatterlist *sg; |
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unsigned int offset; |
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int lastn; |
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offset = rctx->offset; |
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lastn = req->cryptlen - offset; |
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sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize); |
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scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0); |
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memset(d, 0, bsize); |
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scatterwalk_map_and_copy(d, req->src, offset, lastn, 0); |
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scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1); |
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memzero_explicit(d, sizeof(d)); |
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skcipher_request_set_callback(subreq, req->base.flags & |
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CRYPTO_TFM_REQ_MAY_BACKLOG, |
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cts_cbc_crypt_done, req); |
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skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv); |
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return crypto_skcipher_encrypt(subreq); |
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} |
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static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err) |
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{ |
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struct skcipher_request *req = areq->data; |
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if (err) |
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goto out; |
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err = cts_cbc_encrypt(req); |
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if (err == -EINPROGRESS || err == -EBUSY) |
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return; |
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out: |
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skcipher_request_complete(req, err); |
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} |
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static int crypto_cts_encrypt(struct skcipher_request *req) |
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{ |
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
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struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
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struct skcipher_request *subreq = &rctx->subreq; |
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int bsize = crypto_skcipher_blocksize(tfm); |
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unsigned int nbytes = req->cryptlen; |
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unsigned int offset; |
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skcipher_request_set_tfm(subreq, ctx->child); |
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if (nbytes < bsize) |
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return -EINVAL; |
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if (nbytes == bsize) { |
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skcipher_request_set_callback(subreq, req->base.flags, |
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req->base.complete, |
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req->base.data); |
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skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes, |
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req->iv); |
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return crypto_skcipher_encrypt(subreq); |
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} |
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offset = rounddown(nbytes - 1, bsize); |
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rctx->offset = offset; |
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skcipher_request_set_callback(subreq, req->base.flags, |
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crypto_cts_encrypt_done, req); |
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skcipher_request_set_crypt(subreq, req->src, req->dst, |
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offset, req->iv); |
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return crypto_skcipher_encrypt(subreq) ?: |
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cts_cbc_encrypt(req); |
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} |
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static int cts_cbc_decrypt(struct skcipher_request *req) |
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{ |
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struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
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struct skcipher_request *subreq = &rctx->subreq; |
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int bsize = crypto_skcipher_blocksize(tfm); |
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u8 d[MAX_CIPHER_BLOCKSIZE * 2] __aligned(__alignof__(u32)); |
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struct scatterlist *sg; |
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unsigned int offset; |
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u8 *space; |
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int lastn; |
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offset = rctx->offset; |
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lastn = req->cryptlen - offset; |
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sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize); |
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/* 1. Decrypt Cn-1 (s) to create Dn */ |
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scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0); |
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space = crypto_cts_reqctx_space(req); |
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crypto_xor(d + bsize, space, bsize); |
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/* 2. Pad Cn with zeros at the end to create C of length BB */ |
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memset(d, 0, bsize); |
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scatterwalk_map_and_copy(d, req->src, offset, lastn, 0); |
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/* 3. Exclusive-or Dn with C to create Xn */ |
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/* 4. Select the first Ln bytes of Xn to create Pn */ |
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crypto_xor(d + bsize, d, lastn); |
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/* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */ |
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memcpy(d + lastn, d + bsize + lastn, bsize - lastn); |
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/* 6. Decrypt En to create Pn-1 */ |
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scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1); |
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memzero_explicit(d, sizeof(d)); |
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skcipher_request_set_callback(subreq, req->base.flags & |
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CRYPTO_TFM_REQ_MAY_BACKLOG, |
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cts_cbc_crypt_done, req); |
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skcipher_request_set_crypt(subreq, sg, sg, bsize, space); |
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return crypto_skcipher_decrypt(subreq); |
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} |
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static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err) |
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{ |
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struct skcipher_request *req = areq->data; |
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if (err) |
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goto out; |
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err = cts_cbc_decrypt(req); |
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if (err == -EINPROGRESS || err == -EBUSY) |
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return; |
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out: |
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skcipher_request_complete(req, err); |
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} |
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static int crypto_cts_decrypt(struct skcipher_request *req) |
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{ |
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
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struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req); |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
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struct skcipher_request *subreq = &rctx->subreq; |
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int bsize = crypto_skcipher_blocksize(tfm); |
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unsigned int nbytes = req->cryptlen; |
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unsigned int offset; |
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u8 *space; |
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skcipher_request_set_tfm(subreq, ctx->child); |
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if (nbytes < bsize) |
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return -EINVAL; |
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if (nbytes == bsize) { |
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skcipher_request_set_callback(subreq, req->base.flags, |
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req->base.complete, |
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req->base.data); |
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skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes, |
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req->iv); |
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return crypto_skcipher_decrypt(subreq); |
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} |
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skcipher_request_set_callback(subreq, req->base.flags, |
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crypto_cts_decrypt_done, req); |
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space = crypto_cts_reqctx_space(req); |
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offset = rounddown(nbytes - 1, bsize); |
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rctx->offset = offset; |
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if (offset <= bsize) |
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memcpy(space, req->iv, bsize); |
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else |
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scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize, |
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bsize, 0); |
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skcipher_request_set_crypt(subreq, req->src, req->dst, |
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offset, req->iv); |
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return crypto_skcipher_decrypt(subreq) ?: |
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cts_cbc_decrypt(req); |
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} |
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static int crypto_cts_init_tfm(struct crypto_skcipher *tfm) |
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{ |
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struct skcipher_instance *inst = skcipher_alg_instance(tfm); |
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struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst); |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
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struct crypto_skcipher *cipher; |
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unsigned reqsize; |
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unsigned bsize; |
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unsigned align; |
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cipher = crypto_spawn_skcipher(spawn); |
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if (IS_ERR(cipher)) |
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return PTR_ERR(cipher); |
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ctx->child = cipher; |
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align = crypto_skcipher_alignmask(tfm); |
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bsize = crypto_skcipher_blocksize(cipher); |
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reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) + |
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crypto_skcipher_reqsize(cipher), |
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crypto_tfm_ctx_alignment()) + |
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(align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize; |
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crypto_skcipher_set_reqsize(tfm, reqsize); |
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return 0; |
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} |
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static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm) |
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{ |
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struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm); |
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crypto_free_skcipher(ctx->child); |
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} |
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static void crypto_cts_free(struct skcipher_instance *inst) |
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{ |
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crypto_drop_skcipher(skcipher_instance_ctx(inst)); |
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kfree(inst); |
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} |
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static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb) |
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{ |
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struct crypto_skcipher_spawn *spawn; |
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struct skcipher_instance *inst; |
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struct skcipher_alg *alg; |
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u32 mask; |
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int err; |
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err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask); |
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if (err) |
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return err; |
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inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); |
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if (!inst) |
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return -ENOMEM; |
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spawn = skcipher_instance_ctx(inst); |
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err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst), |
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crypto_attr_alg_name(tb[1]), 0, mask); |
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if (err) |
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goto err_free_inst; |
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alg = crypto_spawn_skcipher_alg(spawn); |
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err = -EINVAL; |
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if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize) |
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goto err_free_inst; |
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if (strncmp(alg->base.cra_name, "cbc(", 4)) |
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goto err_free_inst; |
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err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts", |
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&alg->base); |
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if (err) |
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goto err_free_inst; |
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inst->alg.base.cra_priority = alg->base.cra_priority; |
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inst->alg.base.cra_blocksize = alg->base.cra_blocksize; |
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inst->alg.base.cra_alignmask = alg->base.cra_alignmask; |
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inst->alg.ivsize = alg->base.cra_blocksize; |
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inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg); |
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inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg); |
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inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg); |
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inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx); |
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inst->alg.init = crypto_cts_init_tfm; |
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inst->alg.exit = crypto_cts_exit_tfm; |
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inst->alg.setkey = crypto_cts_setkey; |
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inst->alg.encrypt = crypto_cts_encrypt; |
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inst->alg.decrypt = crypto_cts_decrypt; |
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inst->free = crypto_cts_free; |
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err = skcipher_register_instance(tmpl, inst); |
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if (err) { |
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err_free_inst: |
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crypto_cts_free(inst); |
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} |
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return err; |
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} |
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static struct crypto_template crypto_cts_tmpl = { |
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.name = "cts", |
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.create = crypto_cts_create, |
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.module = THIS_MODULE, |
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}; |
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static int __init crypto_cts_module_init(void) |
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{ |
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return crypto_register_template(&crypto_cts_tmpl); |
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} |
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static void __exit crypto_cts_module_exit(void) |
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{ |
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crypto_unregister_template(&crypto_cts_tmpl); |
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} |
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subsys_initcall(crypto_cts_module_init); |
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module_exit(crypto_cts_module_exit); |
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MODULE_LICENSE("Dual BSD/GPL"); |
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MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC"); |
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MODULE_ALIAS_CRYPTO("cts");
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