1/*
2 * aes-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions
3 *
4 * Copyright (C) 2013 - 2014 Linaro Ltd <ard.biesheuvel@linaro.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <asm/neon.h>
12#include <asm/unaligned.h>
13#include <crypto/aes.h>
14#include <crypto/algapi.h>
15#include <crypto/scatterwalk.h>
16#include <crypto/internal/aead.h>
17#include <linux/module.h>
18
19#include "aes-ce-setkey.h"
20
21static int num_rounds(struct crypto_aes_ctx *ctx)
22{
23	/*
24	 * # of rounds specified by AES:
25	 * 128 bit key		10 rounds
26	 * 192 bit key		12 rounds
27	 * 256 bit key		14 rounds
28	 * => n byte key	=> 6 + (n/4) rounds
29	 */
30	return 6 + ctx->key_length / 4;
31}
32
33asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
34				     u32 *macp, u32 const rk[], u32 rounds);
35
36asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes,
37				   u32 const rk[], u32 rounds, u8 mac[],
38				   u8 ctr[]);
39
40asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes,
41				   u32 const rk[], u32 rounds, u8 mac[],
42				   u8 ctr[]);
43
44asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[],
45				 u32 rounds);
46
47static int ccm_setkey(struct crypto_aead *tfm, const u8 *in_key,
48		      unsigned int key_len)
49{
50	struct crypto_aes_ctx *ctx = crypto_aead_ctx(tfm);
51	int ret;
52
53	ret = ce_aes_expandkey(ctx, in_key, key_len);
54	if (!ret)
55		return 0;
56
57	tfm->base.crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
58	return -EINVAL;
59}
60
61static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
62{
63	if ((authsize & 1) || authsize < 4)
64		return -EINVAL;
65	return 0;
66}
67
68static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
69{
70	struct crypto_aead *aead = crypto_aead_reqtfm(req);
71	__be32 *n = (__be32 *)&maciv[AES_BLOCK_SIZE - 8];
72	u32 l = req->iv[0] + 1;
73
74	/* verify that CCM dimension 'L' is set correctly in the IV */
75	if (l < 2 || l > 8)
76		return -EINVAL;
77
78	/* verify that msglen can in fact be represented in L bytes */
79	if (l < 4 && msglen >> (8 * l))
80		return -EOVERFLOW;
81
82	/*
83	 * Even if the CCM spec allows L values of up to 8, the Linux cryptoapi
84	 * uses a u32 type to represent msglen so the top 4 bytes are always 0.
85	 */
86	n[0] = 0;
87	n[1] = cpu_to_be32(msglen);
88
89	memcpy(maciv, req->iv, AES_BLOCK_SIZE - l);
90
91	/*
92	 * Meaning of byte 0 according to CCM spec (RFC 3610/NIST 800-38C)
93	 * - bits 0..2	: max # of bytes required to represent msglen, minus 1
94	 *                (already set by caller)
95	 * - bits 3..5	: size of auth tag (1 => 4 bytes, 2 => 6 bytes, etc)
96	 * - bit 6	: indicates presence of authenticate-only data
97	 */
98	maciv[0] |= (crypto_aead_authsize(aead) - 2) << 2;
99	if (req->assoclen)
100		maciv[0] |= 0x40;
101
102	memset(&req->iv[AES_BLOCK_SIZE - l], 0, l);
103	return 0;
104}
105
106static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
107{
108	struct crypto_aead *aead = crypto_aead_reqtfm(req);
109	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
110	struct __packed { __be16 l; __be32 h; u16 len; } ltag;
111	struct scatter_walk walk;
112	u32 len = req->assoclen;
113	u32 macp = 0;
114
115	/* prepend the AAD with a length tag */
116	if (len < 0xff00) {
117		ltag.l = cpu_to_be16(len);
118		ltag.len = 2;
119	} else  {
120		ltag.l = cpu_to_be16(0xfffe);
121		put_unaligned_be32(len, &ltag.h);
122		ltag.len = 6;
123	}
124
125	ce_aes_ccm_auth_data(mac, (u8 *)&ltag, ltag.len, &macp, ctx->key_enc,
126			     num_rounds(ctx));
127	scatterwalk_start(&walk, req->src);
128
129	do {
130		u32 n = scatterwalk_clamp(&walk, len);
131		u8 *p;
132
133		if (!n) {
134			scatterwalk_start(&walk, sg_next(walk.sg));
135			n = scatterwalk_clamp(&walk, len);
136		}
137		p = scatterwalk_map(&walk);
138		ce_aes_ccm_auth_data(mac, p, n, &macp, ctx->key_enc,
139				     num_rounds(ctx));
140		len -= n;
141
142		scatterwalk_unmap(p);
143		scatterwalk_advance(&walk, n);
144		scatterwalk_done(&walk, 0, len);
145	} while (len);
146}
147
148static int ccm_encrypt(struct aead_request *req)
149{
150	struct crypto_aead *aead = crypto_aead_reqtfm(req);
151	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
152	struct blkcipher_desc desc = { .info = req->iv };
153	struct blkcipher_walk walk;
154	struct scatterlist srcbuf[2];
155	struct scatterlist dstbuf[2];
156	struct scatterlist *src;
157	struct scatterlist *dst;
158	u8 __aligned(8) mac[AES_BLOCK_SIZE];
159	u8 buf[AES_BLOCK_SIZE];
160	u32 len = req->cryptlen;
161	int err;
162
163	err = ccm_init_mac(req, mac, len);
164	if (err)
165		return err;
166
167	kernel_neon_begin_partial(6);
168
169	if (req->assoclen)
170		ccm_calculate_auth_mac(req, mac);
171
172	/* preserve the original iv for the final round */
173	memcpy(buf, req->iv, AES_BLOCK_SIZE);
174
175	src = scatterwalk_ffwd(srcbuf, req->src, req->assoclen);
176	dst = src;
177	if (req->src != req->dst)
178		dst = scatterwalk_ffwd(dstbuf, req->dst, req->assoclen);
179
180	blkcipher_walk_init(&walk, dst, src, len);
181	err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
182					     AES_BLOCK_SIZE);
183
184	while (walk.nbytes) {
185		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
186
187		if (walk.nbytes == len)
188			tail = 0;
189
190		ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
191				   walk.nbytes - tail, ctx->key_enc,
192				   num_rounds(ctx), mac, walk.iv);
193
194		len -= walk.nbytes - tail;
195		err = blkcipher_walk_done(&desc, &walk, tail);
196	}
197	if (!err)
198		ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
199
200	kernel_neon_end();
201
202	if (err)
203		return err;
204
205	/* copy authtag to end of dst */
206	scatterwalk_map_and_copy(mac, dst, req->cryptlen,
207				 crypto_aead_authsize(aead), 1);
208
209	return 0;
210}
211
212static int ccm_decrypt(struct aead_request *req)
213{
214	struct crypto_aead *aead = crypto_aead_reqtfm(req);
215	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
216	unsigned int authsize = crypto_aead_authsize(aead);
217	struct blkcipher_desc desc = { .info = req->iv };
218	struct blkcipher_walk walk;
219	struct scatterlist srcbuf[2];
220	struct scatterlist dstbuf[2];
221	struct scatterlist *src;
222	struct scatterlist *dst;
223	u8 __aligned(8) mac[AES_BLOCK_SIZE];
224	u8 buf[AES_BLOCK_SIZE];
225	u32 len = req->cryptlen - authsize;
226	int err;
227
228	err = ccm_init_mac(req, mac, len);
229	if (err)
230		return err;
231
232	kernel_neon_begin_partial(6);
233
234	if (req->assoclen)
235		ccm_calculate_auth_mac(req, mac);
236
237	/* preserve the original iv for the final round */
238	memcpy(buf, req->iv, AES_BLOCK_SIZE);
239
240	src = scatterwalk_ffwd(srcbuf, req->src, req->assoclen);
241	dst = src;
242	if (req->src != req->dst)
243		dst = scatterwalk_ffwd(dstbuf, req->dst, req->assoclen);
244
245	blkcipher_walk_init(&walk, dst, src, len);
246	err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
247					     AES_BLOCK_SIZE);
248
249	while (walk.nbytes) {
250		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
251
252		if (walk.nbytes == len)
253			tail = 0;
254
255		ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
256				   walk.nbytes - tail, ctx->key_enc,
257				   num_rounds(ctx), mac, walk.iv);
258
259		len -= walk.nbytes - tail;
260		err = blkcipher_walk_done(&desc, &walk, tail);
261	}
262	if (!err)
263		ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
264
265	kernel_neon_end();
266
267	if (err)
268		return err;
269
270	/* compare calculated auth tag with the stored one */
271	scatterwalk_map_and_copy(buf, src, req->cryptlen - authsize,
272				 authsize, 0);
273
274	if (crypto_memneq(mac, buf, authsize))
275		return -EBADMSG;
276	return 0;
277}
278
279static struct aead_alg ccm_aes_alg = {
280	.base = {
281		.cra_name		= "ccm(aes)",
282		.cra_driver_name	= "ccm-aes-ce",
283		.cra_priority		= 300,
284		.cra_blocksize		= 1,
285		.cra_ctxsize		= sizeof(struct crypto_aes_ctx),
286		.cra_alignmask		= 7,
287		.cra_module		= THIS_MODULE,
288	},
289	.ivsize		= AES_BLOCK_SIZE,
290	.maxauthsize	= AES_BLOCK_SIZE,
291	.setkey		= ccm_setkey,
292	.setauthsize	= ccm_setauthsize,
293	.encrypt	= ccm_encrypt,
294	.decrypt	= ccm_decrypt,
295};
296
297static int __init aes_mod_init(void)
298{
299	if (!(elf_hwcap & HWCAP_AES))
300		return -ENODEV;
301	return crypto_register_aead(&ccm_aes_alg);
302}
303
304static void __exit aes_mod_exit(void)
305{
306	crypto_unregister_aead(&ccm_aes_alg);
307}
308
309module_init(aes_mod_init);
310module_exit(aes_mod_exit);
311
312MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
313MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
314MODULE_LICENSE("GPL v2");
315MODULE_ALIAS_CRYPTO("ccm(aes)");
316