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 
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 
65 void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
chacha_init_generic(u32 * state,const u32 * key,const u8 * iv)66 static 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 
chacha_init(u32 * state,const u32 * key,const u8 * iv)83 static 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 
91 void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
92 		       unsigned int bytes, int nrounds);
93 void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
94 			  unsigned int bytes, int nrounds);
95 
chacha_crypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes,int nrounds)96 static 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 
chacha20_crypt(u32 * state,u8 * dst,const u8 * src,unsigned int bytes)105 static 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