chacha.h

  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[at_least CHACHA_BLOCK_SIZE], int nrounds);
 42static inline void chacha20_block(struct chacha_state *state,
 43				  u8 out[at_least CHACHA_BLOCK_SIZE])
 44{
 45	chacha_block_generic(state, out, 20);
 46}
 47
 48void hchacha_block_generic(const struct chacha_state *state,
 49			   u32 out[at_least HCHACHA_OUT_WORDS], int nrounds);
 50
 51void hchacha_block(const struct chacha_state *state,
 52		   u32 out[at_least HCHACHA_OUT_WORDS], int nrounds);
 53
 54enum 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
 61static 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
 69static inline void chacha_init(struct chacha_state *state,
 70			       const u32 key[at_least CHACHA_KEY_WORDS],
 71			       const u8 iv[at_least 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
 88void chacha_crypt(struct chacha_state *state, u8 *dst, const u8 *src,
 89		  unsigned int bytes, int nrounds);
 90
 91static 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
 97static inline void chacha_zeroize_state(struct chacha_state *state)
 98{
 99	memzero_explicit(state, sizeof(*state));
100}
101
102#endif /* _CRYPTO_CHACHA_H */