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 36 struct chacha_state { 37 u32 x[CHACHA_STATE_WORDS]; 38 }; 39 40 void chacha_block_generic(struct chacha_state *state, 41 u8 out[CHACHA_BLOCK_SIZE], int nrounds); 42 static inline void chacha20_block(struct chacha_state *state, 43 u8 out[CHACHA_BLOCK_SIZE]) 44 { 45 chacha_block_generic(state, out, 20); 46 } 47 48 void hchacha_block_generic(const struct chacha_state *state, 49 u32 out[HCHACHA_OUT_WORDS], int nrounds); 50 51 void hchacha_block(const struct chacha_state *state, 52 u32 out[HCHACHA_OUT_WORDS], int nrounds); 53 54 enum chacha_constants { /* expand 32-byte k */ 55 CHACHA_CONSTANT_EXPA = 0x61707865U, 56 CHACHA_CONSTANT_ND_3 = 0x3320646eU, 57 CHACHA_CONSTANT_2_BY = 0x79622d32U, 58 CHACHA_CONSTANT_TE_K = 0x6b206574U 59 }; 60 61 static inline void chacha_init_consts(struct chacha_state *state) 62 { 63 state->x[0] = CHACHA_CONSTANT_EXPA; 64 state->x[1] = CHACHA_CONSTANT_ND_3; 65 state->x[2] = CHACHA_CONSTANT_2_BY; 66 state->x[3] = CHACHA_CONSTANT_TE_K; 67 } 68 69 static inline void chacha_init(struct chacha_state *state, 70 const u32 key[CHACHA_KEY_WORDS], 71 const u8 iv[CHACHA_IV_SIZE]) 72 { 73 chacha_init_consts(state); 74 state->x[4] = key[0]; 75 state->x[5] = key[1]; 76 state->x[6] = key[2]; 77 state->x[7] = key[3]; 78 state->x[8] = key[4]; 79 state->x[9] = key[5]; 80 state->x[10] = key[6]; 81 state->x[11] = key[7]; 82 state->x[12] = get_unaligned_le32(iv + 0); 83 state->x[13] = get_unaligned_le32(iv + 4); 84 state->x[14] = get_unaligned_le32(iv + 8); 85 state->x[15] = get_unaligned_le32(iv + 12); 86 } 87 88 void chacha_crypt(struct chacha_state *state, u8 *dst, const u8 *src, 89 unsigned int bytes, int nrounds); 90 91 static inline void chacha20_crypt(struct chacha_state *state, 92 u8 *dst, const u8 *src, unsigned int bytes) 93 { 94 chacha_crypt(state, dst, src, bytes, 20); 95 } 96 97 static inline void chacha_zeroize_state(struct chacha_state *state) 98 { 99 memzero_explicit(state, sizeof(*state)); 100 } 101 102 #endif /* _CRYPTO_CHACHA_H */ 103