1e28facdeSStephan Mueller /*
2e28facdeSStephan Mueller * Key Wrapping: RFC3394 / NIST SP800-38F
3e28facdeSStephan Mueller *
4e28facdeSStephan Mueller * Copyright (C) 2015, Stephan Mueller <smueller@chronox.de>
5e28facdeSStephan Mueller *
6e28facdeSStephan Mueller * Redistribution and use in source and binary forms, with or without
7e28facdeSStephan Mueller * modification, are permitted provided that the following conditions
8e28facdeSStephan Mueller * are met:
9e28facdeSStephan Mueller * 1. Redistributions of source code must retain the above copyright
10e28facdeSStephan Mueller * notice, and the entire permission notice in its entirety,
11e28facdeSStephan Mueller * including the disclaimer of warranties.
12e28facdeSStephan Mueller * 2. Redistributions in binary form must reproduce the above copyright
13e28facdeSStephan Mueller * notice, this list of conditions and the following disclaimer in the
14e28facdeSStephan Mueller * documentation and/or other materials provided with the distribution.
15e28facdeSStephan Mueller * 3. The name of the author may not be used to endorse or promote
16e28facdeSStephan Mueller * products derived from this software without specific prior
17e28facdeSStephan Mueller * written permission.
18e28facdeSStephan Mueller *
19e28facdeSStephan Mueller * ALTERNATIVELY, this product may be distributed under the terms of
20e28facdeSStephan Mueller * the GNU General Public License, in which case the provisions of the GPL2
21e28facdeSStephan Mueller * are required INSTEAD OF the above restrictions. (This clause is
22e28facdeSStephan Mueller * necessary due to a potential bad interaction between the GPL and
23e28facdeSStephan Mueller * the restrictions contained in a BSD-style copyright.)
24e28facdeSStephan Mueller *
25e28facdeSStephan Mueller * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
26e28facdeSStephan Mueller * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27e28facdeSStephan Mueller * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
28e28facdeSStephan Mueller * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
29e28facdeSStephan Mueller * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30e28facdeSStephan Mueller * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
31e28facdeSStephan Mueller * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
32e28facdeSStephan Mueller * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
33e28facdeSStephan Mueller * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34e28facdeSStephan Mueller * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
35e28facdeSStephan Mueller * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
36e28facdeSStephan Mueller * DAMAGE.
37e28facdeSStephan Mueller */
38e28facdeSStephan Mueller
39e28facdeSStephan Mueller /*
40e28facdeSStephan Mueller * Note for using key wrapping:
41e28facdeSStephan Mueller *
42e28facdeSStephan Mueller * * The result of the encryption operation is the ciphertext starting
43e28facdeSStephan Mueller * with the 2nd semiblock. The first semiblock is provided as the IV.
44e28facdeSStephan Mueller * The IV used to start the encryption operation is the default IV.
45e28facdeSStephan Mueller *
46e28facdeSStephan Mueller * * The input for the decryption is the first semiblock handed in as an
47e28facdeSStephan Mueller * IV. The ciphertext is the data starting with the 2nd semiblock. The
48e28facdeSStephan Mueller * return code of the decryption operation will be EBADMSG in case an
49e28facdeSStephan Mueller * integrity error occurs.
50e28facdeSStephan Mueller *
51e28facdeSStephan Mueller * To obtain the full result of an encryption as expected by SP800-38F, the
52e28facdeSStephan Mueller * caller must allocate a buffer of plaintext + 8 bytes:
53e28facdeSStephan Mueller *
54e28facdeSStephan Mueller * unsigned int datalen = ptlen + crypto_skcipher_ivsize(tfm);
55e28facdeSStephan Mueller * u8 data[datalen];
56e28facdeSStephan Mueller * u8 *iv = data;
57e28facdeSStephan Mueller * u8 *pt = data + crypto_skcipher_ivsize(tfm);
58e28facdeSStephan Mueller * <ensure that pt contains the plaintext of size ptlen>
596b611d98SEric Biggers * sg_init_one(&sg, pt, ptlen);
60e28facdeSStephan Mueller * skcipher_request_set_crypt(req, &sg, &sg, ptlen, iv);
61e28facdeSStephan Mueller *
62e28facdeSStephan Mueller * ==> After encryption, data now contains full KW result as per SP800-38F.
63e28facdeSStephan Mueller *
64e28facdeSStephan Mueller * In case of decryption, ciphertext now already has the expected length
65e28facdeSStephan Mueller * and must be segmented appropriately:
66e28facdeSStephan Mueller *
67e28facdeSStephan Mueller * unsigned int datalen = CTLEN;
68e28facdeSStephan Mueller * u8 data[datalen];
69e28facdeSStephan Mueller * <ensure that data contains full ciphertext>
70e28facdeSStephan Mueller * u8 *iv = data;
71e28facdeSStephan Mueller * u8 *ct = data + crypto_skcipher_ivsize(tfm);
72e28facdeSStephan Mueller * unsigned int ctlen = datalen - crypto_skcipher_ivsize(tfm);
736b611d98SEric Biggers * sg_init_one(&sg, ct, ctlen);
746b611d98SEric Biggers * skcipher_request_set_crypt(req, &sg, &sg, ctlen, iv);
75e28facdeSStephan Mueller *
76e28facdeSStephan Mueller * ==> After decryption (which hopefully does not return EBADMSG), the ct
77e28facdeSStephan Mueller * pointer now points to the plaintext of size ctlen.
78e28facdeSStephan Mueller *
79e28facdeSStephan Mueller * Note 2: KWP is not implemented as this would defy in-place operation.
80e28facdeSStephan Mueller * If somebody wants to wrap non-aligned data, he should simply pad
81e28facdeSStephan Mueller * the input with zeros to fill it up to the 8 byte boundary.
82e28facdeSStephan Mueller */
83e28facdeSStephan Mueller
84e28facdeSStephan Mueller #include <linux/module.h>
85e28facdeSStephan Mueller #include <linux/crypto.h>
86e28facdeSStephan Mueller #include <linux/scatterlist.h>
87e28facdeSStephan Mueller #include <crypto/scatterwalk.h>
880eb76ba2SArd Biesheuvel #include <crypto/internal/cipher.h>
89e28facdeSStephan Mueller #include <crypto/internal/skcipher.h>
90e28facdeSStephan Mueller
91e28facdeSStephan Mueller struct crypto_kw_block {
92e28facdeSStephan Mueller #define SEMIBSIZE 8
939e49451dSStephan Mueller __be64 A;
949e49451dSStephan Mueller __be64 R;
95e28facdeSStephan Mueller };
96e28facdeSStephan Mueller
97e28facdeSStephan Mueller /*
98e28facdeSStephan Mueller * Fast forward the SGL to the "end" length minus SEMIBSIZE.
99e28facdeSStephan Mueller * The start in the SGL defined by the fast-forward is returned with
100e28facdeSStephan Mueller * the walk variable
101e28facdeSStephan Mueller */
crypto_kw_scatterlist_ff(struct scatter_walk * walk,struct scatterlist * sg,unsigned int end)102e28facdeSStephan Mueller static void crypto_kw_scatterlist_ff(struct scatter_walk *walk,
103e28facdeSStephan Mueller struct scatterlist *sg,
104e28facdeSStephan Mueller unsigned int end)
105e28facdeSStephan Mueller {
106e28facdeSStephan Mueller unsigned int skip = 0;
107e28facdeSStephan Mueller
108e28facdeSStephan Mueller /* The caller should only operate on full SEMIBLOCKs. */
109e28facdeSStephan Mueller BUG_ON(end < SEMIBSIZE);
110e28facdeSStephan Mueller
111e28facdeSStephan Mueller skip = end - SEMIBSIZE;
112e28facdeSStephan Mueller while (sg) {
113e28facdeSStephan Mueller if (sg->length > skip) {
114e28facdeSStephan Mueller scatterwalk_start(walk, sg);
115e28facdeSStephan Mueller scatterwalk_advance(walk, skip);
116e28facdeSStephan Mueller break;
117*c29da970SMilan Djurovic }
118e28facdeSStephan Mueller
119*c29da970SMilan Djurovic skip -= sg->length;
120e28facdeSStephan Mueller sg = sg_next(sg);
121e28facdeSStephan Mueller }
122e28facdeSStephan Mueller }
123e28facdeSStephan Mueller
crypto_kw_decrypt(struct skcipher_request * req)1246b611d98SEric Biggers static int crypto_kw_decrypt(struct skcipher_request *req)
125e28facdeSStephan Mueller {
1266b611d98SEric Biggers struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
1276b611d98SEric Biggers struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
1289e49451dSStephan Mueller struct crypto_kw_block block;
1296b611d98SEric Biggers struct scatterlist *src, *dst;
1306b611d98SEric Biggers u64 t = 6 * ((req->cryptlen) >> 3);
1319e49451dSStephan Mueller unsigned int i;
132e28facdeSStephan Mueller int ret = 0;
133e28facdeSStephan Mueller
134e28facdeSStephan Mueller /*
135e28facdeSStephan Mueller * Require at least 2 semiblocks (note, the 3rd semiblock that is
136e28facdeSStephan Mueller * required by SP800-38F is the IV.
137e28facdeSStephan Mueller */
1386b611d98SEric Biggers if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE)
139e28facdeSStephan Mueller return -EINVAL;
140e28facdeSStephan Mueller
141e28facdeSStephan Mueller /* Place the IV into block A */
1426b611d98SEric Biggers memcpy(&block.A, req->iv, SEMIBSIZE);
143e28facdeSStephan Mueller
144e28facdeSStephan Mueller /*
145e28facdeSStephan Mueller * src scatterlist is read-only. dst scatterlist is r/w. During the
1466b611d98SEric Biggers * first loop, src points to req->src and dst to req->dst. For any
1476b611d98SEric Biggers * subsequent round, the code operates on req->dst only.
148e28facdeSStephan Mueller */
1496b611d98SEric Biggers src = req->src;
1506b611d98SEric Biggers dst = req->dst;
151e28facdeSStephan Mueller
152e28facdeSStephan Mueller for (i = 0; i < 6; i++) {
153e28facdeSStephan Mueller struct scatter_walk src_walk, dst_walk;
1546b611d98SEric Biggers unsigned int nbytes = req->cryptlen;
155e28facdeSStephan Mueller
1566b611d98SEric Biggers while (nbytes) {
1576b611d98SEric Biggers /* move pointer by nbytes in the SGL */
1586b611d98SEric Biggers crypto_kw_scatterlist_ff(&src_walk, src, nbytes);
159e28facdeSStephan Mueller /* get the source block */
1609e49451dSStephan Mueller scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,
161e28facdeSStephan Mueller false);
162e28facdeSStephan Mueller
163e28facdeSStephan Mueller /* perform KW operation: modify IV with counter */
1649e49451dSStephan Mueller block.A ^= cpu_to_be64(t);
165e28facdeSStephan Mueller t--;
166e28facdeSStephan Mueller /* perform KW operation: decrypt block */
1676b611d98SEric Biggers crypto_cipher_decrypt_one(cipher, (u8 *)&block,
1689e49451dSStephan Mueller (u8 *)&block);
169e28facdeSStephan Mueller
1706b611d98SEric Biggers /* move pointer by nbytes in the SGL */
1716b611d98SEric Biggers crypto_kw_scatterlist_ff(&dst_walk, dst, nbytes);
172e28facdeSStephan Mueller /* Copy block->R into place */
1739e49451dSStephan Mueller scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,
174e28facdeSStephan Mueller true);
175e28facdeSStephan Mueller
1766b611d98SEric Biggers nbytes -= SEMIBSIZE;
177e28facdeSStephan Mueller }
178e28facdeSStephan Mueller
179e28facdeSStephan Mueller /* we now start to operate on the dst SGL only */
1806b611d98SEric Biggers src = req->dst;
1816b611d98SEric Biggers dst = req->dst;
182e28facdeSStephan Mueller }
183e28facdeSStephan Mueller
184e28facdeSStephan Mueller /* Perform authentication check */
185c9683276SGeert Uytterhoeven if (block.A != cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL))
186e28facdeSStephan Mueller ret = -EBADMSG;
187e28facdeSStephan Mueller
1889e49451dSStephan Mueller memzero_explicit(&block, sizeof(struct crypto_kw_block));
189e28facdeSStephan Mueller
190e28facdeSStephan Mueller return ret;
191e28facdeSStephan Mueller }
192e28facdeSStephan Mueller
crypto_kw_encrypt(struct skcipher_request * req)1936b611d98SEric Biggers static int crypto_kw_encrypt(struct skcipher_request *req)
194e28facdeSStephan Mueller {
1956b611d98SEric Biggers struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
1966b611d98SEric Biggers struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
1979e49451dSStephan Mueller struct crypto_kw_block block;
1986b611d98SEric Biggers struct scatterlist *src, *dst;
1999e49451dSStephan Mueller u64 t = 1;
2009e49451dSStephan Mueller unsigned int i;
201e28facdeSStephan Mueller
202e28facdeSStephan Mueller /*
203e28facdeSStephan Mueller * Require at least 2 semiblocks (note, the 3rd semiblock that is
204e28facdeSStephan Mueller * required by SP800-38F is the IV that occupies the first semiblock.
205e28facdeSStephan Mueller * This means that the dst memory must be one semiblock larger than src.
206e28facdeSStephan Mueller * Also ensure that the given data is aligned to semiblock.
207e28facdeSStephan Mueller */
2086b611d98SEric Biggers if (req->cryptlen < (2 * SEMIBSIZE) || req->cryptlen % SEMIBSIZE)
209e28facdeSStephan Mueller return -EINVAL;
210e28facdeSStephan Mueller
211e28facdeSStephan Mueller /*
212e28facdeSStephan Mueller * Place the predefined IV into block A -- for encrypt, the caller
213e28facdeSStephan Mueller * does not need to provide an IV, but he needs to fetch the final IV.
214e28facdeSStephan Mueller */
215c9683276SGeert Uytterhoeven block.A = cpu_to_be64(0xa6a6a6a6a6a6a6a6ULL);
216e28facdeSStephan Mueller
217e28facdeSStephan Mueller /*
218e28facdeSStephan Mueller * src scatterlist is read-only. dst scatterlist is r/w. During the
2196b611d98SEric Biggers * first loop, src points to req->src and dst to req->dst. For any
2206b611d98SEric Biggers * subsequent round, the code operates on req->dst only.
221e28facdeSStephan Mueller */
2226b611d98SEric Biggers src = req->src;
2236b611d98SEric Biggers dst = req->dst;
224e28facdeSStephan Mueller
225e28facdeSStephan Mueller for (i = 0; i < 6; i++) {
226e28facdeSStephan Mueller struct scatter_walk src_walk, dst_walk;
2276b611d98SEric Biggers unsigned int nbytes = req->cryptlen;
228e28facdeSStephan Mueller
2296b611d98SEric Biggers scatterwalk_start(&src_walk, src);
2306b611d98SEric Biggers scatterwalk_start(&dst_walk, dst);
231e28facdeSStephan Mueller
2326b611d98SEric Biggers while (nbytes) {
233e28facdeSStephan Mueller /* get the source block */
2349e49451dSStephan Mueller scatterwalk_copychunks(&block.R, &src_walk, SEMIBSIZE,
235e28facdeSStephan Mueller false);
236e28facdeSStephan Mueller
237e28facdeSStephan Mueller /* perform KW operation: encrypt block */
2386b611d98SEric Biggers crypto_cipher_encrypt_one(cipher, (u8 *)&block,
2399e49451dSStephan Mueller (u8 *)&block);
240e28facdeSStephan Mueller /* perform KW operation: modify IV with counter */
2419e49451dSStephan Mueller block.A ^= cpu_to_be64(t);
242e28facdeSStephan Mueller t++;
243e28facdeSStephan Mueller
244e28facdeSStephan Mueller /* Copy block->R into place */
2459e49451dSStephan Mueller scatterwalk_copychunks(&block.R, &dst_walk, SEMIBSIZE,
246e28facdeSStephan Mueller true);
247e28facdeSStephan Mueller
2486b611d98SEric Biggers nbytes -= SEMIBSIZE;
249e28facdeSStephan Mueller }
250e28facdeSStephan Mueller
251e28facdeSStephan Mueller /* we now start to operate on the dst SGL only */
2526b611d98SEric Biggers src = req->dst;
2536b611d98SEric Biggers dst = req->dst;
254e28facdeSStephan Mueller }
255e28facdeSStephan Mueller
256e28facdeSStephan Mueller /* establish the IV for the caller to pick up */
2576b611d98SEric Biggers memcpy(req->iv, &block.A, SEMIBSIZE);
258e28facdeSStephan Mueller
2599e49451dSStephan Mueller memzero_explicit(&block, sizeof(struct crypto_kw_block));
260e28facdeSStephan Mueller
261e28facdeSStephan Mueller return 0;
262e28facdeSStephan Mueller }
263e28facdeSStephan Mueller
crypto_kw_create(struct crypto_template * tmpl,struct rtattr ** tb)2646b611d98SEric Biggers static int crypto_kw_create(struct crypto_template *tmpl, struct rtattr **tb)
265e28facdeSStephan Mueller {
2666b611d98SEric Biggers struct skcipher_instance *inst;
2676b611d98SEric Biggers struct crypto_alg *alg;
268e28facdeSStephan Mueller int err;
269e28facdeSStephan Mueller
270b3c16bfcSHerbert Xu inst = skcipher_alloc_instance_simple(tmpl, tb);
2716b611d98SEric Biggers if (IS_ERR(inst))
2726b611d98SEric Biggers return PTR_ERR(inst);
273e28facdeSStephan Mueller
274b3c16bfcSHerbert Xu alg = skcipher_ialg_simple(inst);
275b3c16bfcSHerbert Xu
2766b611d98SEric Biggers err = -EINVAL;
277e28facdeSStephan Mueller /* Section 5.1 requirement for KW */
278e28facdeSStephan Mueller if (alg->cra_blocksize != sizeof(struct crypto_kw_block))
2796b611d98SEric Biggers goto out_free_inst;
280e28facdeSStephan Mueller
2816b611d98SEric Biggers inst->alg.base.cra_blocksize = SEMIBSIZE;
2826b611d98SEric Biggers inst->alg.base.cra_alignmask = 0;
2836b611d98SEric Biggers inst->alg.ivsize = SEMIBSIZE;
284e28facdeSStephan Mueller
2856b611d98SEric Biggers inst->alg.encrypt = crypto_kw_encrypt;
2866b611d98SEric Biggers inst->alg.decrypt = crypto_kw_decrypt;
287e28facdeSStephan Mueller
2886b611d98SEric Biggers err = skcipher_register_instance(tmpl, inst);
289b3c16bfcSHerbert Xu if (err) {
2906b611d98SEric Biggers out_free_inst:
2916b611d98SEric Biggers inst->free(inst);
292b3c16bfcSHerbert Xu }
293b3c16bfcSHerbert Xu
2946b611d98SEric Biggers return err;
295e28facdeSStephan Mueller }
296e28facdeSStephan Mueller
297e28facdeSStephan Mueller static struct crypto_template crypto_kw_tmpl = {
298e28facdeSStephan Mueller .name = "kw",
2996b611d98SEric Biggers .create = crypto_kw_create,
300e28facdeSStephan Mueller .module = THIS_MODULE,
301e28facdeSStephan Mueller };
302e28facdeSStephan Mueller
crypto_kw_init(void)303e28facdeSStephan Mueller static int __init crypto_kw_init(void)
304e28facdeSStephan Mueller {
305e28facdeSStephan Mueller return crypto_register_template(&crypto_kw_tmpl);
306e28facdeSStephan Mueller }
307e28facdeSStephan Mueller
crypto_kw_exit(void)308e28facdeSStephan Mueller static void __exit crypto_kw_exit(void)
309e28facdeSStephan Mueller {
310e28facdeSStephan Mueller crypto_unregister_template(&crypto_kw_tmpl);
311e28facdeSStephan Mueller }
312e28facdeSStephan Mueller
313c4741b23SEric Biggers subsys_initcall(crypto_kw_init);
314e28facdeSStephan Mueller module_exit(crypto_kw_exit);
315e28facdeSStephan Mueller
316e28facdeSStephan Mueller MODULE_LICENSE("Dual BSD/GPL");
317e28facdeSStephan Mueller MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
318e28facdeSStephan Mueller MODULE_DESCRIPTION("Key Wrapping (RFC3394 / NIST SP800-38F)");
319e28facdeSStephan Mueller MODULE_ALIAS_CRYPTO("kw");
3200eb76ba2SArd Biesheuvel MODULE_IMPORT_NS(CRYPTO_INTERNAL);
321