1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
4 *
5 * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
6 * security.  Here they share the same key size, tfm context, and setkey
7 * function; only their IV size and encrypt/decrypt function differ.
8 *
9 * The ChaCha paper specifies 20, 12, and 8-round variants.  In general, it is
10 * recommended to use the 20-round variant ChaCha20.  However, the other
11 * variants can be needed in some performance-sensitive scenarios.  The generic
12 * ChaCha code currently allows only the 20 and 12-round variants.
13 */
14
15#ifndef _CRYPTO_CHACHA_H
16#define _CRYPTO_CHACHA_H
17
18#include <asm/unaligned.h>
19#include <linux/types.h>
20
21/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
22#define CHACHA_IV_SIZE		16
23
24#define CHACHA_KEY_SIZE		32
25#define CHACHA_BLOCK_SIZE	64
26#define CHACHAPOLY_IV_SIZE	12
27
28#define CHACHA_STATE_WORDS	(CHACHA_BLOCK_SIZE / sizeof(u32))
29
30/* 192-bit nonce, then 64-bit stream position */
31#define XCHACHA_IV_SIZE		32
32
33void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
34static inline void chacha20_block(u32 *state, u8 *stream)
35{
36	chacha_block_generic(state, stream, 20);
37}
38
39void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
40void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
41
42static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
43{
44	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
45		hchacha_block_arch(state, out, nrounds);
46	else
47		hchacha_block_generic(state, out, nrounds);
48}
49
50enum chacha_constants { /* expand 32-byte k */
51	CHACHA_CONSTANT_EXPA = 0x61707865U,
52	CHACHA_CONSTANT_ND_3 = 0x3320646eU,
53	CHACHA_CONSTANT_2_BY = 0x79622d32U,
54	CHACHA_CONSTANT_TE_K = 0x6b206574U
55};
56
57static inline void chacha_init_consts(u32 *state)
58{
59	state[0]  = CHACHA_CONSTANT_EXPA;
60	state[1]  = CHACHA_CONSTANT_ND_3;
61	state[2]  = CHACHA_CONSTANT_2_BY;
62	state[3]  = CHACHA_CONSTANT_TE_K;
63}
64
65void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
66static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
67{
68	chacha_init_consts(state);
69	state[4]  = key[0];
70	state[5]  = key[1];
71	state[6]  = key[2];
72	state[7]  = key[3];
73	state[8]  = key[4];
74	state[9]  = key[5];
75	state[10] = key[6];
76	state[11] = key[7];
77	state[12] = get_unaligned_le32(iv +  0);
78	state[13] = get_unaligned_le32(iv +  4);
79	state[14] = get_unaligned_le32(iv +  8);
80	state[15] = get_unaligned_le32(iv + 12);
81}
82
83static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
84{
85	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
86		chacha_init_arch(state, key, iv);
87	else
88		chacha_init_generic(state, key, iv);
89}
90
91void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
92		       unsigned int bytes, int nrounds);
93void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
94			  unsigned int bytes, int nrounds);
95
96static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
97				unsigned int bytes, int nrounds)
98{
99	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
100		chacha_crypt_arch(state, dst, src, bytes, nrounds);
101	else
102		chacha_crypt_generic(state, dst, src, bytes, nrounds);
103}
104
105static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
106				  unsigned int bytes)
107{
108	chacha_crypt(state, dst, src, bytes, 20);
109}
110
111#endif /* _CRYPTO_CHACHA_H */
112