xref: /openbmc/linux/include/crypto/chacha.h (revision b4e18b29)
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);
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 
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 void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
51 static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
52 {
53 	state[0]  = 0x61707865; /* "expa" */
54 	state[1]  = 0x3320646e; /* "nd 3" */
55 	state[2]  = 0x79622d32; /* "2-by" */
56 	state[3]  = 0x6b206574; /* "te k" */
57 	state[4]  = key[0];
58 	state[5]  = key[1];
59 	state[6]  = key[2];
60 	state[7]  = key[3];
61 	state[8]  = key[4];
62 	state[9]  = key[5];
63 	state[10] = key[6];
64 	state[11] = key[7];
65 	state[12] = get_unaligned_le32(iv +  0);
66 	state[13] = get_unaligned_le32(iv +  4);
67 	state[14] = get_unaligned_le32(iv +  8);
68 	state[15] = get_unaligned_le32(iv + 12);
69 }
70 
71 static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
72 {
73 	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
74 		chacha_init_arch(state, key, iv);
75 	else
76 		chacha_init_generic(state, key, iv);
77 }
78 
79 void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
80 		       unsigned int bytes, int nrounds);
81 void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
82 			  unsigned int bytes, int nrounds);
83 
84 static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
85 				unsigned int bytes, int nrounds)
86 {
87 	if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
88 		chacha_crypt_arch(state, dst, src, bytes, nrounds);
89 	else
90 		chacha_crypt_generic(state, dst, src, bytes, nrounds);
91 }
92 
93 static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
94 				  unsigned int bytes)
95 {
96 	chacha_crypt(state, dst, src, bytes, 20);
97 }
98 
99 #endif /* _CRYPTO_CHACHA_H */
100