[linux-2.6-block.git] / crypto / chacha20_generic.c

/*
 * ChaCha20 256-bit cipher algorithm, RFC7539
 *
 * Copyright (C) 2015 Martin Willi
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <crypto/algapi.h>
#include <linux/crypto.h>
#include <linux/kernel.h>
#include <linux/module.h>

#define CHACHA20_NONCE_SIZE 16
#define CHACHA20_KEY_SIZE   32
#define CHACHA20_BLOCK_SIZE 64

struct chacha20_ctx {
	u32 key[8];
};

static inline u32 rotl32(u32 v, u8 n)
{
	return (v << n) | (v >> (sizeof(v) * 8 - n));
}

static inline u32 le32_to_cpuvp(const void *p)
{
	return le32_to_cpup(p);
}

static void chacha20_block(u32 *state, void *stream)
{
	u32 x[16], *out = stream;
	int i;

	for (i = 0; i < ARRAY_SIZE(x); i++)
		x[i] = state[i];

	for (i = 0; i < 20; i += 2) {
		x[0]  += x[4];    x[12] = rotl32(x[12] ^ x[0],  16);
		x[1]  += x[5];    x[13] = rotl32(x[13] ^ x[1],  16);
		x[2]  += x[6];    x[14] = rotl32(x[14] ^ x[2],  16);
		x[3]  += x[7];    x[15] = rotl32(x[15] ^ x[3],  16);

		x[8]  += x[12];   x[4]  = rotl32(x[4]  ^ x[8],  12);
		x[9]  += x[13];   x[5]  = rotl32(x[5]  ^ x[9],  12);
		x[10] += x[14];   x[6]  = rotl32(x[6]  ^ x[10], 12);
		x[11] += x[15];   x[7]  = rotl32(x[7]  ^ x[11], 12);

		x[0]  += x[4];    x[12] = rotl32(x[12] ^ x[0],   8);
		x[1]  += x[5];    x[13] = rotl32(x[13] ^ x[1],   8);
		x[2]  += x[6];    x[14] = rotl32(x[14] ^ x[2],   8);
		x[3]  += x[7];    x[15] = rotl32(x[15] ^ x[3],   8);

		x[8]  += x[12];   x[4]  = rotl32(x[4]  ^ x[8],   7);
		x[9]  += x[13];   x[5]  = rotl32(x[5]  ^ x[9],   7);
		x[10] += x[14];   x[6]  = rotl32(x[6]  ^ x[10],  7);
		x[11] += x[15];   x[7]  = rotl32(x[7]  ^ x[11],  7);

		x[0]  += x[5];    x[15] = rotl32(x[15] ^ x[0],  16);
		x[1]  += x[6];    x[12] = rotl32(x[12] ^ x[1],  16);
		x[2]  += x[7];    x[13] = rotl32(x[13] ^ x[2],  16);
		x[3]  += x[4];    x[14] = rotl32(x[14] ^ x[3],  16);

		x[10] += x[15];   x[5]  = rotl32(x[5]  ^ x[10], 12);
		x[11] += x[12];   x[6]  = rotl32(x[6]  ^ x[11], 12);
		x[8]  += x[13];   x[7]  = rotl32(x[7]  ^ x[8],  12);
		x[9]  += x[14];   x[4]  = rotl32(x[4]  ^ x[9],  12);

		x[0]  += x[5];    x[15] = rotl32(x[15] ^ x[0],   8);
		x[1]  += x[6];    x[12] = rotl32(x[12] ^ x[1],   8);
		x[2]  += x[7];    x[13] = rotl32(x[13] ^ x[2],   8);
		x[3]  += x[4];    x[14] = rotl32(x[14] ^ x[3],   8);

		x[10] += x[15];   x[5]  = rotl32(x[5]  ^ x[10],  7);
		x[11] += x[12];   x[6]  = rotl32(x[6]  ^ x[11],  7);
		x[8]  += x[13];   x[7]  = rotl32(x[7]  ^ x[8],   7);
		x[9]  += x[14];   x[4]  = rotl32(x[4]  ^ x[9],   7);
	}

	for (i = 0; i < ARRAY_SIZE(x); i++)
		out[i] = cpu_to_le32(x[i] + state[i]);

	state[12]++;
}

static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
			     unsigned int bytes)
{
	u8 stream[CHACHA20_BLOCK_SIZE];

	if (dst != src)
		memcpy(dst, src, bytes);

	while (bytes >= CHACHA20_BLOCK_SIZE) {
		chacha20_block(state, stream);
		crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
		bytes -= CHACHA20_BLOCK_SIZE;
		dst += CHACHA20_BLOCK_SIZE;
	}
	if (bytes) {
		chacha20_block(state, stream);
		crypto_xor(dst, stream, bytes);
	}
}

static void chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
{
	static const char constant[16] = "expand 32-byte k";

	state[0]  = le32_to_cpuvp(constant +  0);
	state[1]  = le32_to_cpuvp(constant +  4);
	state[2]  = le32_to_cpuvp(constant +  8);
	state[3]  = le32_to_cpuvp(constant + 12);
	state[4]  = ctx->key[0];
	state[5]  = ctx->key[1];
	state[6]  = ctx->key[2];
	state[7]  = ctx->key[3];
	state[8]  = ctx->key[4];
	state[9]  = ctx->key[5];
	state[10] = ctx->key[6];
	state[11] = ctx->key[7];
	state[12] = le32_to_cpuvp(iv +  0);
	state[13] = le32_to_cpuvp(iv +  4);
	state[14] = le32_to_cpuvp(iv +  8);
	state[15] = le32_to_cpuvp(iv + 12);
}

static int chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
			   unsigned int keysize)
{
	struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
	int i;

	if (keysize != CHACHA20_KEY_SIZE)
		return -EINVAL;

	for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
		ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));

	return 0;
}

static int chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
			  struct scatterlist *src, unsigned int nbytes)
{
	struct blkcipher_walk walk;
	u32 state[16];
	int err;

	blkcipher_walk_init(&walk, dst, src, nbytes);
	err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);

	chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);

	while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
		chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
				 rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
		err = blkcipher_walk_done(desc, &walk,
					  walk.nbytes % CHACHA20_BLOCK_SIZE);
	}

	if (walk.nbytes) {
		chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
				 walk.nbytes);
		err = blkcipher_walk_done(desc, &walk, 0);
	}

	return err;
}

static struct crypto_alg alg = {
	.cra_name		= "chacha20",
	.cra_driver_name	= "chacha20-generic",
	.cra_priority		= 100,
	.cra_flags		= CRYPTO_ALG_TYPE_BLKCIPHER,
	.cra_blocksize		= 1,
	.cra_type		= &crypto_blkcipher_type,
	.cra_ctxsize		= sizeof(struct chacha20_ctx),
	.cra_alignmask		= sizeof(u32) - 1,
	.cra_module		= THIS_MODULE,
	.cra_u			= {
		.blkcipher = {
			.min_keysize	= CHACHA20_KEY_SIZE,
			.max_keysize	= CHACHA20_KEY_SIZE,
			.ivsize		= CHACHA20_NONCE_SIZE,
			.geniv		= "seqiv",
			.setkey		= chacha20_setkey,
			.encrypt	= chacha20_crypt,
			.decrypt	= chacha20_crypt,
		},
	},
};

static int __init chacha20_generic_mod_init(void)
{
	return crypto_register_alg(&alg);
}

static void __exit chacha20_generic_mod_fini(void)
{
	crypto_unregister_alg(&alg);
}

module_init(chacha20_generic_mod_init);
module_exit(chacha20_generic_mod_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
MODULE_DESCRIPTION("chacha20 cipher algorithm");
MODULE_ALIAS_CRYPTO("chacha20");
MODULE_ALIAS_CRYPTO("chacha20-generic");
Commit	Line	Data
c08d0e64 MW	1	/*
	2	* ChaCha20 256-bit cipher algorithm, RFC7539
	3	*
	4	* Copyright (C) 2015 Martin Willi
	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 as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (at your option) any later version.
	10	*/
	11
	12	#include <crypto/algapi.h>
	13	#include <linux/crypto.h>
	14	#include <linux/kernel.h>
	15	#include <linux/module.h>
	16
	17	#define CHACHA20_NONCE_SIZE 16
	18	#define CHACHA20_KEY_SIZE 32
	19	#define CHACHA20_BLOCK_SIZE 64
	20
	21	struct chacha20_ctx {
	22	u32 key[8];
	23	};
	24
	25	static inline u32 rotl32(u32 v, u8 n)
	26	{
	27	return (v << n) \| (v >> (sizeof(v) * 8 - n));
	28	}
	29
	30	static inline u32 le32_to_cpuvp(const void *p)
	31	{
	32	return le32_to_cpup(p);
	33	}
	34
	35	static void chacha20_block(u32 state, void stream)
	36	{
	37	u32 x[16], *out = stream;
	38	int i;
	39
	40	for (i = 0; i < ARRAY_SIZE(x); i++)
	41	x[i] = state[i];
	42
	43	for (i = 0; i < 20; i += 2) {
	44	x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
	45	x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
	46	x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
	47	x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
	48
	49	x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
	50	x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
	51	x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
	52	x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
	53
	54	x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
	55	x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
	56	x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
	57	x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
	58
	59	x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
	60	x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
	61	x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
	62	x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
	63
	64	x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
65	x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
66	x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
67	x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
68
69	x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
70	x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
71	x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
72	x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
73
74	x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
75	x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
76	x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
77	x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
78
79	x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
80	x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
81	x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
82	x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
83	}
84
85	for (i = 0; i < ARRAY_SIZE(x); i++)
86	out[i] = cpu_to_le32(x[i] + state[i]);
87
88	state[12]++;
89	}
90
91	static void chacha20_docrypt(u32 state, u8 dst, const u8 *src,
92	unsigned int bytes)
93	{
94	u8 stream[CHACHA20_BLOCK_SIZE];
95
96	if (dst != src)
97	memcpy(dst, src, bytes);
98
99	while (bytes >= CHACHA20_BLOCK_SIZE) {
100	chacha20_block(state, stream);
101	crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
102	bytes -= CHACHA20_BLOCK_SIZE;
103	dst += CHACHA20_BLOCK_SIZE;
104	}
105	if (bytes) {
106	chacha20_block(state, stream);
107	crypto_xor(dst, stream, bytes);
108	}
109	}
110
111	static void chacha20_init(u32 state, struct chacha20_ctx ctx, u8 *iv)
112	{
113	static const char constant[16] = "expand 32-byte k";
114
115	state[0] = le32_to_cpuvp(constant + 0);
116	state[1] = le32_to_cpuvp(constant + 4);
117	state[2] = le32_to_cpuvp(constant + 8);
118	state[3] = le32_to_cpuvp(constant + 12);
119	state[4] = ctx->key[0];
120	state[5] = ctx->key[1];
121	state[6] = ctx->key[2];
122	state[7] = ctx->key[3];
123	state[8] = ctx->key[4];
124	state[9] = ctx->key[5];
125	state[10] = ctx->key[6];
126	state[11] = ctx->key[7];
127	state[12] = le32_to_cpuvp(iv + 0);
128	state[13] = le32_to_cpuvp(iv + 4);
129	state[14] = le32_to_cpuvp(iv + 8);
130	state[15] = le32_to_cpuvp(iv + 12);
131	}
132
133	static int chacha20_setkey(struct crypto_tfm tfm, const u8 key,
134	unsigned int keysize)
135	{
136	struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
137	int i;
138
139	if (keysize != CHACHA20_KEY_SIZE)
140	return -EINVAL;
141
142	for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
143	ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
144
145	return 0;
146	}
147
148	static int chacha20_crypt(struct blkcipher_desc desc, struct scatterlist dst,
149	struct scatterlist *src, unsigned int nbytes)
150	{
151	struct blkcipher_walk walk;
152	u32 state[16];
153	int err;
154
155	blkcipher_walk_init(&walk, dst, src, nbytes);
156	err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
157
158	chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
159
160	while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
161	chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
162	rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
163	err = blkcipher_walk_done(desc, &walk,
164	walk.nbytes % CHACHA20_BLOCK_SIZE);
165	}
166
167	if (walk.nbytes) {
168	chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
169	walk.nbytes);
170	err = blkcipher_walk_done(desc, &walk, 0);
171	}
172
173	return err;
174	}
175
176	static struct crypto_alg alg = {
177	.cra_name = "chacha20",
178	.cra_driver_name = "chacha20-generic",
179	.cra_priority = 100,
180	.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
181	.cra_blocksize = 1,
182	.cra_type = &crypto_blkcipher_type,
183	.cra_ctxsize = sizeof(struct chacha20_ctx),
184	.cra_alignmask = sizeof(u32) - 1,
185	.cra_module = THIS_MODULE,
186	.cra_u = {
187	.blkcipher = {
188	.min_keysize = CHACHA20_KEY_SIZE,
189	.max_keysize = CHACHA20_KEY_SIZE,
190	.ivsize = CHACHA20_NONCE_SIZE,
191	.geniv = "seqiv",
192	.setkey = chacha20_setkey,
193	.encrypt = chacha20_crypt,
194	.decrypt = chacha20_crypt,
195	},
196	},
197	};
198
199	static int __init chacha20_generic_mod_init(void)
200	{
201	return crypto_register_alg(&alg);
202	}
203
204	static void __exit chacha20_generic_mod_fini(void)
205	{
206	crypto_unregister_alg(&alg);
207	}
208
209	module_init(chacha20_generic_mod_init);
210	module_exit(chacha20_generic_mod_fini);
211
212	MODULE_LICENSE("GPL");
213	MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
214	MODULE_DESCRIPTION("chacha20 cipher algorithm");
215	MODULE_ALIAS_CRYPTO("chacha20");
216	MODULE_ALIAS_CRYPTO("chacha20-generic");