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
 33void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
 34static inline void chacha20_block(u32 *state, u8 *stream)
 35{
 36	chacha_block_generic(state, stream, 20);
 37}
 38
 39void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
 40void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
 41
 42static 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
 50enum 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
 57static 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
 65void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
 66static 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
 83static 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
 91void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
 92		       unsigned int bytes, int nrounds);
 93void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
 94			  unsigned int bytes, int nrounds);
 95
 96static 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
105static 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 */