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 <linux/unaligned.h>
19#include <linux/string.h>
20#include <linux/types.h>
21
22/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
23#define CHACHA_IV_SIZE 16
24
25#define CHACHA_KEY_SIZE 32
26#define CHACHA_BLOCK_SIZE 64
27#define CHACHAPOLY_IV_SIZE 12
28
29#define CHACHA_KEY_WORDS 8
30#define CHACHA_STATE_WORDS 16
31#define HCHACHA_OUT_WORDS 8
32
33/* 192-bit nonce, then 64-bit stream position */
34#define XCHACHA_IV_SIZE 32
35
36struct chacha_state {
37 u32 x[CHACHA_STATE_WORDS];
38};
39
40void chacha_block_generic(struct chacha_state *state,
41 u8 out[CHACHA_BLOCK_SIZE], int nrounds);
42static inline void chacha20_block(struct chacha_state *state,
43 u8 out[CHACHA_BLOCK_SIZE])
44{
45 chacha_block_generic(state, out, nrounds: 20);
46}
47
48void hchacha_block_arch(const struct chacha_state *state,
49 u32 out[HCHACHA_OUT_WORDS], int nrounds);
50void hchacha_block_generic(const struct chacha_state *state,
51 u32 out[HCHACHA_OUT_WORDS], int nrounds);
52
53static inline void hchacha_block(const struct chacha_state *state,
54 u32 out[HCHACHA_OUT_WORDS], int nrounds)
55{
56 if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
57 hchacha_block_arch(state, out, nrounds);
58 else
59 hchacha_block_generic(state, out, nrounds);
60}
61
62enum chacha_constants { /* expand 32-byte k */
63 CHACHA_CONSTANT_EXPA = 0x61707865U,
64 CHACHA_CONSTANT_ND_3 = 0x3320646eU,
65 CHACHA_CONSTANT_2_BY = 0x79622d32U,
66 CHACHA_CONSTANT_TE_K = 0x6b206574U
67};
68
69static inline void chacha_init_consts(struct chacha_state *state)
70{
71 state->x[0] = CHACHA_CONSTANT_EXPA;
72 state->x[1] = CHACHA_CONSTANT_ND_3;
73 state->x[2] = CHACHA_CONSTANT_2_BY;
74 state->x[3] = CHACHA_CONSTANT_TE_K;
75}
76
77static inline void chacha_init(struct chacha_state *state,
78 const u32 key[CHACHA_KEY_WORDS],
79 const u8 iv[CHACHA_IV_SIZE])
80{
81 chacha_init_consts(state);
82 state->x[4] = key[0];
83 state->x[5] = key[1];
84 state->x[6] = key[2];
85 state->x[7] = key[3];
86 state->x[8] = key[4];
87 state->x[9] = key[5];
88 state->x[10] = key[6];
89 state->x[11] = key[7];
90 state->x[12] = get_unaligned_le32(p: iv + 0);
91 state->x[13] = get_unaligned_le32(p: iv + 4);
92 state->x[14] = get_unaligned_le32(p: iv + 8);
93 state->x[15] = get_unaligned_le32(p: iv + 12);
94}
95
96void chacha_crypt_arch(struct chacha_state *state, u8 *dst, const u8 *src,
97 unsigned int bytes, int nrounds);
98void chacha_crypt_generic(struct chacha_state *state, u8 *dst, const u8 *src,
99 unsigned int bytes, int nrounds);
100
101static inline void chacha_crypt(struct chacha_state *state,
102 u8 *dst, const u8 *src,
103 unsigned int bytes, int nrounds)
104{
105 if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
106 chacha_crypt_arch(state, dst, src, bytes, nrounds);
107 else
108 chacha_crypt_generic(state, dst, src, bytes, nrounds);
109}
110
111static inline void chacha20_crypt(struct chacha_state *state,
112 u8 *dst, const u8 *src, unsigned int bytes)
113{
114 chacha_crypt(state, dst, src, bytes, nrounds: 20);
115}
116
117static inline void chacha_zeroize_state(struct chacha_state *state)
118{
119 memzero_explicit(s: state, count: sizeof(*state));
120}
121
122#if IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA)
123bool chacha_is_arch_optimized(void);
124#else
125static inline bool chacha_is_arch_optimized(void)
126{
127 return false;
128}
129#endif
130
131#endif /* _CRYPTO_CHACHA_H */
132

source code of linux/include/crypto/chacha.h

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