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Diffstat (limited to 'crypto/keywrap.c')
| -rw-r--r-- | crypto/keywrap.c | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/crypto/keywrap.c b/crypto/keywrap.c new file mode 100644 index 000000000..0355cce21 --- /dev/null +++ b/crypto/keywrap.c @@ -0,0 +1,318 @@ +/* + * Key Wrapping: RFC3394 / NIST SP800-38F + * + * Copyright (C) 2015, Stephan Mueller <smueller@chronox.de> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, and the entire permission notice in its entirety, + * including the disclaimer of warranties. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of the author may not be used to endorse or promote + * products derived from this software without specific prior + * written permission. + * + * ALTERNATIVELY, this product may be distributed under the terms of + * the GNU General Public License, in which case the provisions of the GPL2 + * are required INSTEAD OF the above restrictions. (This clause is + * necessary due to a potential bad interaction between the GPL and + * the restrictions contained in a BSD-style copyright.) + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF + * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT + * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR + * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE + * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH + * DAMAGE. + */ + +/* + * Note for using key wrapping: + * + * * The result of the encryption operation is the ciphertext starting + * with the 2nd semiblock. The first semiblock is provided as the IV. + * The IV used to start the encryption operation is the default IV. + * + * * The input for the decryption is the first semiblock handed in as an + * IV. The ciphertext is the data starting with the 2nd semiblock. The + * return code of the decryption operation will be EBADMSG in case an + * integrity error occurs. + * + * To obtain the full result of an encryption as expected by SP800-38F, the + * caller must allocate a buffer of plaintext + 8 bytes: + * + * unsigned int datalen = ptlen + crypto_skcipher_ivsize(tfm); + * u8 data[datalen]; + * u8 *iv = data; + * u8 *pt = data + crypto_skcipher_ivsize(tfm); + * <ensure that pt contains the plaintext of size ptlen> + * sg_init_one(&sg, pt, ptlen); + * skcipher_request_set_crypt(req, &sg, &sg, ptlen, iv); + * + * ==> After encryption, data now contains full KW result as per SP800-38F. + * + * In case of decryption, ciphertext now already has the expected length + * and must be segmented appropriately: + * + * unsigned int datalen = CTLEN; + * u8 data[datalen]; + * <ensure that data contains full ciphertext> + * u8 *iv = data; + * u8 *ct = data + crypto_skcipher_ivsize(tfm); + * unsigned int ctlen = datalen - crypto_skcipher_ivsize(tfm); + * sg_init_one(&sg, ct, ctlen); + * skcipher_request_set_crypt(req, &sg, &sg, ctlen, iv); + * + * ==> After decryption (which hopefully does not return EBADMSG), the ct + * pointer now points to the plaintext of size ctlen. + * + * Note 2: KWP is not implemented as this would defy in-place operation. + * If somebody wants to wrap non-aligned data, he should simply pad + * the input with zeros to fill it up to the 8 byte boundary. + */ + +#include <linux/module.h> +#include <linux/crypto.h> +#include <linux/scatterlist.h> +#include <crypto/scatterwalk.h> +#include <crypto/internal/skcipher.h> + +struct crypto_kw_block { +#define SEMIBSIZE 8 + __be64 A; + __be64 R; +}; + +/* + * Fast forward the SGL to the "end" length minus SEMIBSIZE. + * The start in the SGL defined by the fast-forward is returned with + * the walk variable + */ +static void crypto_kw_scatterlist_ff(struct scatter_walk *walk, + struct scatterlist *sg, + unsigned int end) +{ + unsigned int skip = 0; + + /* The caller should only operate on full SEMIBLOCKs. */ + BUG_ON(end < SEMIBSIZE); + + skip = end - SEMIBSIZE; + while (sg) { + if (sg->length > skip) { + scatterwalk_start(walk, sg); + scatterwalk_advance(walk, skip); + break; + } else + skip -= sg->length; + + sg = sg_next(sg); + } +} + +static int crypto_kw_decrypt(struct skcipher_request *req) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + struct crypto_cipher *cipher = skcipher_cipher_simple(tfm); + struct crypto_kw_block block; + struct scatterlist *src, *dst; + u64 t = 6 * ((req->cryptlen) >> 3); + unsigned int i; + int ret = 0; + + /* + * Require at least 2 semiblocks (note, the 3rd semiblock that is + * required by SP800-38F is the IV. + */ + if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE) + return -EINVAL; + + /* Place the IV into block A */ + memcpy(&block.A, req->iv, SEMIBSIZE); + + /* + * src scatterlist is read-only. dst scatterlist is r/w. During the + * first loop, src points to req->src and dst to req->dst. For any + * subsequent round, the code operates on req->dst only. + */ + src = req->src; + dst = req->dst; + + for (i = 0; i < 6; i++) { + struct scatter_walk src_walk, dst_walk; + unsigned int nbytes = req->cryptlen; + + while (nbytes) { + /* move pointer by nbytes in the SGL */ + crypto_kw_scatterlist_ff(&src_walk, src, nbytes); + /* get the source block */ + scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE, + false); + + /* perform KW operation: modify IV with counter */ + block.A ^= cpu_to_be64(t); + t--; + /* perform KW operation: decrypt block */ + crypto_cipher_decrypt_one(cipher, (u8 *)&block, + (u8 *)&block); + + /* move pointer by nbytes in the SGL */ + crypto_kw_scatterlist_ff(&dst_walk, dst, nbytes); + /* Copy block->R into place */ + scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE, + true); + + nbytes -= SEMIBSIZE; + } + + /* we now start to operate on the dst SGL only */ + src = req->dst; + dst = req->dst; + } + + /* Perform authentication check */ + if (block.A != cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL)) + ret = -EBADMSG; + + memzero_explicit(&block, sizeof(struct crypto_kw_block)); + + return ret; +} + +static int crypto_kw_encrypt(struct skcipher_request *req) +{ + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); + struct crypto_cipher *cipher = skcipher_cipher_simple(tfm); + struct crypto_kw_block block; + struct scatterlist *src, *dst; + u64 t = 1; + unsigned int i; + + /* + * Require at least 2 semiblocks (note, the 3rd semiblock that is + * required by SP800-38F is the IV that occupies the first semiblock. + * This means that the dst memory must be one semiblock larger than src. + * Also ensure that the given data is aligned to semiblock. + */ + if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE) + return -EINVAL; + + /* + * Place the predefined IV into block A -- for encrypt, the caller + * does not need to provide an IV, but he needs to fetch the final IV. + */ + block.A = cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL); + + /* + * src scatterlist is read-only. dst scatterlist is r/w. During the + * first loop, src points to req->src and dst to req->dst. For any + * subsequent round, the code operates on req->dst only. + */ + src = req->src; + dst = req->dst; + + for (i = 0; i < 6; i++) { + struct scatter_walk src_walk, dst_walk; + unsigned int nbytes = req->cryptlen; + + scatterwalk_start(&src_walk, src); + scatterwalk_start(&dst_walk, dst); + + while (nbytes) { + /* get the source block */ + scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE, + false); + + /* perform KW operation: encrypt block */ + crypto_cipher_encrypt_one(cipher, (u8 *)&block, + (u8 *)&block); + /* perform KW operation: modify IV with counter */ + block.A ^= cpu_to_be64(t); + t++; + + /* Copy block->R into place */ + scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE, + true); + + nbytes -= SEMIBSIZE; + } + + /* we now start to operate on the dst SGL only */ + src = req->dst; + dst = req->dst; + } + + /* establish the IV for the caller to pick up */ + memcpy(req->iv, &block.A, SEMIBSIZE); + + memzero_explicit(&block, sizeof(struct crypto_kw_block)); + + return 0; +} + +static int crypto_kw_create(struct crypto_template *tmpl, struct rtattr **tb) +{ + struct skcipher_instance *inst; + struct crypto_alg *alg; + int err; + + inst = skcipher_alloc_instance_simple(tmpl, tb); + if (IS_ERR(inst)) + return PTR_ERR(inst); + + alg = skcipher_ialg_simple(inst); + + err = -EINVAL; + /* Section 5.1 requirement for KW */ + if (alg->cra_blocksize != sizeof(struct crypto_kw_block)) + goto out_free_inst; + + inst->alg.base.cra_blocksize = SEMIBSIZE; + inst->alg.base.cra_alignmask = 0; + inst->alg.ivsize = SEMIBSIZE; + + inst->alg.encrypt = crypto_kw_encrypt; + inst->alg.decrypt = crypto_kw_decrypt; + + err = skcipher_register_instance(tmpl, inst); + if (err) { +out_free_inst: + inst->free(inst); + } + + return err; +} + +static struct crypto_template crypto_kw_tmpl = { + .name = "kw", + .create = crypto_kw_create, + .module = THIS_MODULE, +}; + +static int __init crypto_kw_init(void) +{ + return crypto_register_template(&crypto_kw_tmpl); +} + +static void __exit crypto_kw_exit(void) +{ + crypto_unregister_template(&crypto_kw_tmpl); +} + +subsys_initcall(crypto_kw_init); +module_exit(crypto_kw_exit); + +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>"); +MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)"); +MODULE_ALIAS_CRYPTO("kw"); |