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
num_rounds(struct crypto_aes_ctx * ctx)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
ccm_setkey(struct crypto_aead * tfm,const u8 * in_key,unsigned int key_len)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
ccm_setauthsize(struct crypto_aead * tfm,unsigned int authsize)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
ccm_init_mac(struct aead_request * req,u8 maciv[],u32 msglen)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
ccm_calculate_auth_mac(struct aead_request * req,u8 mac[])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, <ag.h);
122 ltag.len = 6;
123 }
124
125 ce_aes_ccm_auth_data(mac, (u8 *)<ag, 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
ccm_encrypt(struct aead_request * req)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
ccm_decrypt(struct aead_request * req)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
aes_mod_init(void)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
aes_mod_exit(void)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