1 /* 1
2 * Key Wrapping: RFC3394 / NIST SP800-38F
3 *
4 * Copyright (C) 2015, Stephan Mueller <smuell
5 *
6 * Redistribution and use in source and binary
7 * modification, are permitted provided that t
8 * are met:
9 * 1. Redistributions of source code must reta
10 * notice, and the entire permission notice
11 * including the disclaimer of warranties.
12 * 2. Redistributions in binary form must repr
13 * notice, this list of conditions and the
14 * documentation and/or other materials pro
15 * 3. The name of the author may not be used t
16 * products derived from this software with
17 * written permission.
18 *
19 * ALTERNATIVELY, this product may be distribu
20 * the GNU General Public License, in which ca
21 * are required INSTEAD OF the above restricti
22 * necessary due to a potential bad interactio
23 * the restrictions contained in a BSD-style c
24 *
25 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY
26 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTIC
28 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT S
29 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL
30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT L
31 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF US
32 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND O
33 * LIABILITY, WHETHER IN CONTRACT, STRICT LIAB
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
35 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED O
36 * DAMAGE.
37 */
38
39 /*
40 * Note for using key wrapping:
41 *
42 * * The result of the encryption operati
43 * with the 2nd semiblock. The first se
44 * The IV used to start the encryption
45 *
46 * * The input for the decryption is the
47 * IV. The ciphertext is the data start
48 * return code of the decryption operat
49 * integrity error occurs.
50 *
51 * To obtain the full result of an encryption
52 * caller must allocate a buffer of plaintext
53 *
54 * unsigned int datalen = ptlen + crypto_
55 * u8 data[datalen];
56 * u8 *iv = data;
57 * u8 *pt = data + crypto_skcipher_ivsize
58 * <ensure that pt contains the p
59 * sg_init_one(&sg, pt, ptlen);
60 * skcipher_request_set_crypt(req, &sg, &
61 *
62 * ==> After encryption, data now contain
63 *
64 * In case of decryption, ciphertext now alrea
65 * and must be segmented appropriately:
66 *
67 * unsigned int datalen = CTLEN;
68 * u8 data[datalen];
69 * <ensure that data contains ful
70 * u8 *iv = data;
71 * u8 *ct = data + crypto_skcipher_ivsize
72 * unsigned int ctlen = datalen - crypto_
73 * sg_init_one(&sg, ct, ctlen);
74 * skcipher_request_set_crypt(req, &sg, &
75 *
76 * ==> After decryption (which hopefully
77 * pointer now points to the plaintext of
78 *
79 * Note 2: KWP is not implemented as this woul
80 * If somebody wants to wrap non-align
81 * the input with zeros to fill it up
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
91 struct crypto_kw_block {
92 #define SEMIBSIZE 8
93 __be64 A;
94 __be64 R;
95 };
96
97 /*
98 * Fast forward the SGL to the "end" length mi
99 * The start in the SGL defined by the fast-fo
100 * the walk variable
101 */
102 static void crypto_kw_scatterlist_ff(struct sc
103 struct sc
104 unsigned
105 {
106 unsigned int skip = 0;
107
108 /* The caller should only operate on f
109 BUG_ON(end < SEMIBSIZE);
110
111 skip = end - SEMIBSIZE;
112 while (sg) {
113 if (sg->length > skip) {
114 scatterwalk_start(walk
115 scatterwalk_advance(wa
116 break;
117 }
118
119 skip -= sg->length;
120 sg = sg_next(sg);
121 }
122 }
123
124 static int crypto_kw_decrypt(struct skcipher_r
125 {
126 struct crypto_skcipher *tfm = crypto_s
127 struct crypto_cipher *cipher = skciphe
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
136 * required by SP800-38F is the IV.
137 */
138 if (req->cryptlen < (2 * 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 s
146 * first loop, src points to req->src
147 * subsequent round, the code operates
148 */
149 src = req->src;
150 dst = req->dst;
151
152 for (i = 0; i < 6; i++) {
153 struct scatter_walk src_walk,
154 unsigned int nbytes = req->cry
155
156 while (nbytes) {
157 /* move pointer by nby
158 crypto_kw_scatterlist_
159 /* get the source bloc
160 scatterwalk_copychunks
161
162
163 /* perform KW operatio
164 block.A ^= cpu_to_be64
165 t--;
166 /* perform KW operatio
167 crypto_cipher_decrypt_
168
169
170 /* move pointer by nby
171 crypto_kw_scatterlist_
172 /* Copy block->R into
173 scatterwalk_copychunks
174
175
176 nbytes -= SEMIBSIZE;
177 }
178
179 /* we now start to operate on
180 src = req->dst;
181 dst = req->dst;
182 }
183
184 /* Perform authentication check */
185 if (block.A != cpu_to_be64(0xa6a6a6a6a
186 ret = -EBADMSG;
187
188 memzero_explicit(&block, sizeof(struct
189
190 return ret;
191 }
192
193 static int crypto_kw_encrypt(struct skcipher_r
194 {
195 struct crypto_skcipher *tfm = crypto_s
196 struct crypto_cipher *cipher = skciphe
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
204 * required by SP800-38F is the IV tha
205 * This means that the dst memory must
206 * Also ensure that the given data is
207 */
208 if (req->cryptlen < (2 * SEMIBSIZE) ||
209 return -EINVAL;
210
211 /*
212 * Place the predefined IV into block
213 * does not need to provide an IV, but
214 */
215 block.A = cpu_to_be64(0xa6a6a6a6a6a6a6
216
217 /*
218 * src scatterlist is read-only. dst s
219 * first loop, src points to req->src
220 * subsequent round, the code operates
221 */
222 src = req->src;
223 dst = req->dst;
224
225 for (i = 0; i < 6; i++) {
226 struct scatter_walk src_walk,
227 unsigned int nbytes = req->cry
228
229 scatterwalk_start(&src_walk, s
230 scatterwalk_start(&dst_walk, d
231
232 while (nbytes) {
233 /* get the source bloc
234 scatterwalk_copychunks
235
236
237 /* perform KW operatio
238 crypto_cipher_encrypt_
239
240 /* perform KW operatio
241 block.A ^= cpu_to_be64
242 t++;
243
244 /* Copy block->R into
245 scatterwalk_copychunks
246
247
248 nbytes -= SEMIBSIZE;
249 }
250
251 /* we now start to operate on
252 src = req->dst;
253 dst = req->dst;
254 }
255
256 /* establish the IV for the caller to
257 memcpy(req->iv, &block.A, SEMIBSIZE);
258
259 memzero_explicit(&block, sizeof(struct
260
261 return 0;
262 }
263
264 static int crypto_kw_create(struct crypto_temp
265 {
266 struct skcipher_instance *inst;
267 struct crypto_alg *alg;
268 int err;
269
270 inst = skcipher_alloc_instance_simple(
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(struc
279 goto out_free_inst;
280
281 inst->alg.base.cra_blocksize = SEMIBSI
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,
289 if (err) {
290 out_free_inst:
291 inst->free(inst);
292 }
293
294 return err;
295 }
296
297 static struct crypto_template crypto_kw_tmpl =
298 .name = "kw",
299 .create = crypto_kw_create,
300 .module = THIS_MODULE,
301 };
302
303 static int __init crypto_kw_init(void)
304 {
305 return crypto_register_template(&crypt
306 }
307
308 static void __exit crypto_kw_exit(void)
309 {
310 crypto_unregister_template(&crypto_kw_
311 }
312
313 subsys_initcall(crypto_kw_init);
314 module_exit(crypto_kw_exit);
315
316 MODULE_LICENSE("Dual BSD/GPL");
317 MODULE_AUTHOR("Stephan Mueller <smueller@chron
318 MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NI
319 MODULE_ALIAS_CRYPTO("kw");
320 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
321
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