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/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
33 void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
chacha20_block(u32 * state,u8 * stream)34 static inline void chacha20_block(u32 *state, u8 *stream)
35 {
36 chacha_block_generic(state, stream, 20);
37 }
38
39 void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
40 void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
41
hchacha_block(const u32 * state,u32 * out,int nrounds)42 static 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
50 enum 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
chacha_init_consts(u32 * state)57 static 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
chacha_init(u32 * state,const u32 * key,const u8 * iv)65 static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
66 {
67 chacha_init_consts(state);
68 state[4] = key[0];
69 state[5] = key[1];
70 state[6] = key[2];
71 state[7] = key[3];
72 state[8] = key[4];
73 state[9] = key[5];
74 state[10] = key[6];
75 state[11] = key[7];
76 state[12] = get_unaligned_le32(iv + 0);
77 state[13] = get_unaligned_le32(iv + 4);
78 state[14] = get_unaligned_le32(iv + 8);
79 state[15] = get_unaligned_le32(iv + 12);
80 }
81
82 void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
83 unsigned int bytes, int nrounds);
84 void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
85 unsigned int bytes, int nrounds);
86
chacha_crypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes,int nrounds)87 static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
88 unsigned int bytes, int nrounds)
89 {
90 if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
91 chacha_crypt_arch(state, dst, src, bytes, nrounds);
92 else
93 chacha_crypt_generic(state, dst, src, bytes, nrounds);
94 }
95
chacha20_crypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes)96 static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
97 unsigned int bytes)
98 {
99 chacha_crypt(state, dst, src, bytes, 20);
100 }
101
102 #endif /* _CRYPTO_CHACHA_H */
103