321 lines · c
1/*2 * Key Wrapping: RFC3394 / NIST SP800-38F3 *4 * Copyright (C) 2015, Stephan Mueller <smueller@chronox.de>5 *6 * Redistribution and use in source and binary forms, with or without7 * modification, are permitted provided that the following conditions8 * are met:9 * 1. Redistributions of source code must retain the above copyright10 * notice, and the entire permission notice in its entirety,11 * including the disclaimer of warranties.12 * 2. Redistributions in binary form must reproduce the above copyright13 * notice, this list of conditions and the following disclaimer in the14 * documentation and/or other materials provided with the distribution.15 * 3. The name of the author may not be used to endorse or promote16 * products derived from this software without specific prior17 * written permission.18 *19 * ALTERNATIVELY, this product may be distributed under the terms of20 * the GNU General Public License, in which case the provisions of the GPL221 * are required INSTEAD OF the above restrictions. (This clause is22 * necessary due to a potential bad interaction between the GPL and23 * the restrictions contained in a BSD-style copyright.)24 *25 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED26 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF28 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE29 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT31 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR32 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF33 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE35 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH36 * DAMAGE.37 */38 39/*40 * Note for using key wrapping:41 *42 * * The result of the encryption operation is the ciphertext starting43 * with the 2nd semiblock. The first semiblock is provided as the IV.44 * The IV used to start the encryption operation is the default IV.45 *46 * * The input for the decryption is the first semiblock handed in as an47 * IV. The ciphertext is the data starting with the 2nd semiblock. The48 * return code of the decryption operation will be EBADMSG in case an49 * integrity error occurs.50 *51 * To obtain the full result of an encryption as expected by SP800-38F, the52 * caller must allocate a buffer of plaintext + 8 bytes:53 *54 * unsigned int datalen = ptlen + crypto_skcipher_ivsize(tfm);55 * u8 data[datalen];56 * u8 *iv = data;57 * u8 *pt = data + crypto_skcipher_ivsize(tfm);58 * <ensure that pt contains the plaintext of size ptlen>59 * sg_init_one(&sg, pt, ptlen);60 * skcipher_request_set_crypt(req, &sg, &sg, ptlen, iv);61 *62 * ==> After encryption, data now contains full KW result as per SP800-38F.63 *64 * In case of decryption, ciphertext now already has the expected length65 * and must be segmented appropriately:66 *67 * unsigned int datalen = CTLEN;68 * u8 data[datalen];69 * <ensure that data contains full ciphertext>70 * u8 *iv = data;71 * u8 *ct = data + crypto_skcipher_ivsize(tfm);72 * unsigned int ctlen = datalen - crypto_skcipher_ivsize(tfm);73 * sg_init_one(&sg, ct, ctlen);74 * skcipher_request_set_crypt(req, &sg, &sg, ctlen, iv);75 *76 * ==> After decryption (which hopefully does not return EBADMSG), the ct77 * pointer now points to the plaintext of size ctlen.78 *79 * Note 2: KWP is not implemented as this would defy in-place operation.80 * If somebody wants to wrap non-aligned data, he should simply pad81 * the input with zeros to fill it up to the 8 byte boundary.82 */83 84#include <linux/module.h>85#include <linux/crypto.h>86#include <linux/scatterlist.h>87#include <crypto/scatterwalk.h>88#include <crypto/internal/cipher.h>89#include <crypto/internal/skcipher.h>90 91struct crypto_kw_block {92#define SEMIBSIZE 893 __be64 A;94 __be64 R;95};96 97/*98 * Fast forward the SGL to the "end" length minus SEMIBSIZE.99 * The start in the SGL defined by the fast-forward is returned with100 * the walk variable101 */102static void crypto_kw_scatterlist_ff(struct scatter_walk *walk,103 struct scatterlist *sg,104 unsigned int end)105{106 unsigned int skip = 0;107 108 /* The caller should only operate on full SEMIBLOCKs. */109 BUG_ON(end < SEMIBSIZE);110 111 skip = end - SEMIBSIZE;112 while (sg) {113 if (sg->length > skip) {114 scatterwalk_start(walk, sg);115 scatterwalk_advance(walk, skip);116 break;117 }118 119 skip -= sg->length;120 sg = sg_next(sg);121 }122}123 124static int crypto_kw_decrypt(struct skcipher_request *req)125{126 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);127 struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);128 struct crypto_kw_block block;129 struct scatterlist *src, *dst;130 u64 t = 6 * ((req->cryptlen) >> 3);131 unsigned int i;132 int ret = 0;133 134 /*135 * Require at least 2 semiblocks (note, the 3rd semiblock that is136 * required by SP800-38F is the IV.137 */138 if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE)139 return -EINVAL;140 141 /* Place the IV into block A */142 memcpy(&block.A, req->iv, SEMIBSIZE);143 144 /*145 * src scatterlist is read-only. dst scatterlist is r/w. During the146 * first loop, src points to req->src and dst to req->dst. For any147 * subsequent round, the code operates on req->dst only.148 */149 src = req->src;150 dst = req->dst;151 152 for (i = 0; i < 6; i++) {153 struct scatter_walk src_walk, dst_walk;154 unsigned int nbytes = req->cryptlen;155 156 while (nbytes) {157 /* move pointer by nbytes in the SGL */158 crypto_kw_scatterlist_ff(&src_walk, src, nbytes);159 /* get the source block */160 scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,161 false);162 163 /* perform KW operation: modify IV with counter */164 block.A ^= cpu_to_be64(t);165 t--;166 /* perform KW operation: decrypt block */167 crypto_cipher_decrypt_one(cipher, (u8 *)&block,168 (u8 *)&block);169 170 /* move pointer by nbytes in the SGL */171 crypto_kw_scatterlist_ff(&dst_walk, dst, nbytes);172 /* Copy block->R into place */173 scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,174 true);175 176 nbytes -= SEMIBSIZE;177 }178 179 /* we now start to operate on the dst SGL only */180 src = req->dst;181 dst = req->dst;182 }183 184 /* Perform authentication check */185 if (block.A != cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL))186 ret = -EBADMSG;187 188 memzero_explicit(&block, sizeof(struct crypto_kw_block));189 190 return ret;191}192 193static int crypto_kw_encrypt(struct skcipher_request *req)194{195 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);196 struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);197 struct crypto_kw_block block;198 struct scatterlist *src, *dst;199 u64 t = 1;200 unsigned int i;201 202 /*203 * Require at least 2 semiblocks (note, the 3rd semiblock that is204 * required by SP800-38F is the IV that occupies the first semiblock.205 * This means that the dst memory must be one semiblock larger than src.206 * Also ensure that the given data is aligned to semiblock.207 */208 if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE)209 return -EINVAL;210 211 /*212 * Place the predefined IV into block A -- for encrypt, the caller213 * does not need to provide an IV, but he needs to fetch the final IV.214 */215 block.A = cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL);216 217 /*218 * src scatterlist is read-only. dst scatterlist is r/w. During the219 * first loop, src points to req->src and dst to req->dst. For any220 * subsequent round, the code operates on req->dst only.221 */222 src = req->src;223 dst = req->dst;224 225 for (i = 0; i < 6; i++) {226 struct scatter_walk src_walk, dst_walk;227 unsigned int nbytes = req->cryptlen;228 229 scatterwalk_start(&src_walk, src);230 scatterwalk_start(&dst_walk, dst);231 232 while (nbytes) {233 /* get the source block */234 scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,235 false);236 237 /* perform KW operation: encrypt block */238 crypto_cipher_encrypt_one(cipher, (u8 *)&block,239 (u8 *)&block);240 /* perform KW operation: modify IV with counter */241 block.A ^= cpu_to_be64(t);242 t++;243 244 /* Copy block->R into place */245 scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,246 true);247 248 nbytes -= SEMIBSIZE;249 }250 251 /* we now start to operate on the dst SGL only */252 src = req->dst;253 dst = req->dst;254 }255 256 /* establish the IV for the caller to pick up */257 memcpy(req->iv, &block.A, SEMIBSIZE);258 259 memzero_explicit(&block, sizeof(struct crypto_kw_block));260 261 return 0;262}263 264static int crypto_kw_create(struct crypto_template *tmpl, struct rtattr **tb)265{266 struct skcipher_instance *inst;267 struct crypto_alg *alg;268 int err;269 270 inst = skcipher_alloc_instance_simple(tmpl, tb);271 if (IS_ERR(inst))272 return PTR_ERR(inst);273 274 alg = skcipher_ialg_simple(inst);275 276 err = -EINVAL;277 /* Section 5.1 requirement for KW */278 if (alg->cra_blocksize != sizeof(struct crypto_kw_block))279 goto out_free_inst;280 281 inst->alg.base.cra_blocksize = SEMIBSIZE;282 inst->alg.base.cra_alignmask = 0;283 inst->alg.ivsize = SEMIBSIZE;284 285 inst->alg.encrypt = crypto_kw_encrypt;286 inst->alg.decrypt = crypto_kw_decrypt;287 288 err = skcipher_register_instance(tmpl, inst);289 if (err) {290out_free_inst:291 inst->free(inst);292 }293 294 return err;295}296 297static struct crypto_template crypto_kw_tmpl = {298 .name = "kw",299 .create = crypto_kw_create,300 .module = THIS_MODULE,301};302 303static int __init crypto_kw_init(void)304{305 return crypto_register_template(&crypto_kw_tmpl);306}307 308static void __exit crypto_kw_exit(void)309{310 crypto_unregister_template(&crypto_kw_tmpl);311}312 313subsys_initcall(crypto_kw_init);314module_exit(crypto_kw_exit);315 316MODULE_LICENSE("Dual BSD/GPL");317MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");318MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)");319MODULE_ALIAS_CRYPTO("kw");320MODULE_IMPORT_NS(CRYPTO_INTERNAL);321