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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Common values and helper functions for the ChaCha and XChaCha stream ciphers.
*
* XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
* security. Here they share the same key size, tfm context, and setkey
* function; only their IV size and encrypt/decrypt function differ.
*
* The ChaCha paper specifies 20, 12, and 8-round variants. In general, it is
* recommended to use the 20-round variant ChaCha20. However, the other
* variants can be needed in some performance-sensitive scenarios. The generic
* ChaCha code currently allows only the 20 and 12-round variants.
*/
#ifndef _CRYPTO_CHACHA_H
#define _CRYPTO_CHACHA_H
#include <linux/unaligned.h>
#include <linux/string.h>
#include <linux/types.h>
/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
#define CHACHA_IV_SIZE 16
#define CHACHA_KEY_SIZE 32
#define CHACHA_BLOCK_SIZE 64
#define CHACHAPOLY_IV_SIZE 12
#define CHACHA_KEY_WORDS 8
#define CHACHA_STATE_WORDS 16
#define HCHACHA_OUT_WORDS 8
/* 192-bit nonce, then 64-bit stream position */
#define XCHACHA_IV_SIZE 32
struct chacha_state {
u32 x[CHACHA_STATE_WORDS];
};
void chacha_block_generic(struct chacha_state *state,
u8 out[CHACHA_BLOCK_SIZE], int nrounds);
static inline void chacha20_block(struct chacha_state *state,
u8 out[CHACHA_BLOCK_SIZE])
{
chacha_block_generic(state, out, 20);
}
void hchacha_block_generic(const struct chacha_state *state,
u32 out[HCHACHA_OUT_WORDS], int nrounds);
void hchacha_block(const struct chacha_state *state,
u32 out[HCHACHA_OUT_WORDS], int nrounds);
enum chacha_constants { /* expand 32-byte k */
CHACHA_CONSTANT_EXPA = 0x61707865U,
CHACHA_CONSTANT_ND_3 = 0x3320646eU,
CHACHA_CONSTANT_2_BY = 0x79622d32U,
CHACHA_CONSTANT_TE_K = 0x6b206574U
};
static inline void chacha_init_consts(struct chacha_state *state)
{
state->x[0] = CHACHA_CONSTANT_EXPA;
state->x[1] = CHACHA_CONSTANT_ND_3;
state->x[2] = CHACHA_CONSTANT_2_BY;
state->x[3] = CHACHA_CONSTANT_TE_K;
}
static inline void chacha_init(struct chacha_state *state,
const u32 key[CHACHA_KEY_WORDS],
const u8 iv[CHACHA_IV_SIZE])
{
chacha_init_consts(state);
state->x[4] = key[0];
state->x[5] = key[1];
state->x[6] = key[2];
state->x[7] = key[3];
state->x[8] = key[4];
state->x[9] = key[5];
state->x[10] = key[6];
state->x[11] = key[7];
state->x[12] = get_unaligned_le32(iv + 0);
state->x[13] = get_unaligned_le32(iv + 4);
state->x[14] = get_unaligned_le32(iv + 8);
state->x[15] = get_unaligned_le32(iv + 12);
}
void chacha_crypt(struct chacha_state *state, u8 *dst, const u8 *src,
unsigned int bytes, int nrounds);
static inline void chacha20_crypt(struct chacha_state *state,
u8 *dst, const u8 *src, unsigned int bytes)
{
chacha_crypt(state, dst, src, bytes, 20);
}
static inline void chacha_zeroize_state(struct chacha_state *state)
{
memzero_explicit(state, sizeof(*state));
}
#endif /* _CRYPTO_CHACHA_H */
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