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 
21 static 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 
33 asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
34 				     u32 *macp, u32 const rk[], u32 rounds);
35 
36 asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes,
37 				   u32 const rk[], u32 rounds, u8 mac[],
38 				   u8 ctr[]);
39 
40 asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes,
41 				   u32 const rk[], u32 rounds, u8 mac[],
42 				   u8 ctr[]);
43 
44 asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[],
45 				 u32 rounds);
46 
47 static 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 
61 static 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 
68 static 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 
106 static 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 
148 static 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 
212 static 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 
279 static 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 
297 static 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 
304 static void __exit aes_mod_exit(void)
305 {
306 	crypto_unregister_aead(&ccm_aes_alg);
307 }
308 
309 module_init(aes_mod_init);
310 module_exit(aes_mod_exit);
311 
312 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
313 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
314 MODULE_LICENSE("GPL v2");
315 MODULE_ALIAS_CRYPTO("ccm(aes)");
316