1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Scalar fixed time AES core transform
4  *
5  * Copyright (C) 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
6  */
7 
8 #include <crypto/aes.h>
9 #include <linux/crypto.h>
10 #include <linux/module.h>
11 
aesti_set_key(struct crypto_tfm * tfm,const u8 * in_key,unsigned int key_len)12 static int aesti_set_key(struct crypto_tfm *tfm, const u8 *in_key,
13 			 unsigned int key_len)
14 {
15 	struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
16 
17 	return aes_expandkey(ctx, in_key, key_len);
18 }
19 
aesti_encrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)20 static void aesti_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
21 {
22 	const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
23 	unsigned long flags;
24 
25 	/*
26 	 * Temporarily disable interrupts to avoid races where cachelines are
27 	 * evicted when the CPU is interrupted to do something else.
28 	 */
29 	local_irq_save(flags);
30 
31 	aes_encrypt(ctx, out, in);
32 
33 	local_irq_restore(flags);
34 }
35 
aesti_decrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)36 static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
37 {
38 	const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
39 	unsigned long flags;
40 
41 	/*
42 	 * Temporarily disable interrupts to avoid races where cachelines are
43 	 * evicted when the CPU is interrupted to do something else.
44 	 */
45 	local_irq_save(flags);
46 
47 	aes_decrypt(ctx, out, in);
48 
49 	local_irq_restore(flags);
50 }
51 
52 static struct crypto_alg aes_alg = {
53 	.cra_name			= "aes",
54 	.cra_driver_name		= "aes-fixed-time",
55 	.cra_priority			= 100 + 1,
56 	.cra_flags			= CRYPTO_ALG_TYPE_CIPHER,
57 	.cra_blocksize			= AES_BLOCK_SIZE,
58 	.cra_ctxsize			= sizeof(struct crypto_aes_ctx),
59 	.cra_module			= THIS_MODULE,
60 
61 	.cra_cipher.cia_min_keysize	= AES_MIN_KEY_SIZE,
62 	.cra_cipher.cia_max_keysize	= AES_MAX_KEY_SIZE,
63 	.cra_cipher.cia_setkey		= aesti_set_key,
64 	.cra_cipher.cia_encrypt		= aesti_encrypt,
65 	.cra_cipher.cia_decrypt		= aesti_decrypt
66 };
67 
aes_init(void)68 static int __init aes_init(void)
69 {
70 	return crypto_register_alg(&aes_alg);
71 }
72 
aes_fini(void)73 static void __exit aes_fini(void)
74 {
75 	crypto_unregister_alg(&aes_alg);
76 }
77 
78 module_init(aes_init);
79 module_exit(aes_fini);
80 
81 MODULE_DESCRIPTION("Generic fixed time AES");
82 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
83 MODULE_LICENSE("GPL v2");
84