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Diffstat (limited to 'lib/crypto/chacha-block-generic.c')
| -rw-r--r-- | lib/crypto/chacha-block-generic.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/lib/crypto/chacha-block-generic.c b/lib/crypto/chacha-block-generic.c new file mode 100644 index 000000000000..77f68de71066 --- /dev/null +++ b/lib/crypto/chacha-block-generic.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * The "hash function" used as the core of the ChaCha stream cipher (RFC7539) + * + * Copyright (C) 2015 Martin Willi + */ + +#include <crypto/chacha.h> +#include <linux/bitops.h> +#include <linux/bug.h> +#include <linux/export.h> +#include <linux/kernel.h> +#include <linux/string.h> +#include <linux/unaligned.h> + +static void chacha_permute(struct chacha_state *state, int nrounds) +{ + u32 *x = state->x; + int i; + + /* whitelist the allowed round counts */ + WARN_ON_ONCE(nrounds != 20 && nrounds != 12); + + for (i = 0; i < nrounds; i += 2) { + x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16); + x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16); + x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16); + x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16); + + x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12); + x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12); + x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12); + x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12); + + x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8); + x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8); + x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8); + x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8); + + x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7); + x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7); + x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7); + x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7); + + x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16); + x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16); + x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16); + x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16); + + x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12); + x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12); + x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12); + x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12); + + x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8); + x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8); + x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8); + x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8); + + x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7); + x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7); + x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7); + x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7); + } +} + +/** + * chacha_block_generic - generate one keystream block and increment block counter + * @state: input state matrix + * @out: output keystream block + * @nrounds: number of rounds (20 or 12; 20 is recommended) + * + * This is the ChaCha core, a function from 64-byte strings to 64-byte strings. + * The caller has already converted the endianness of the input. This function + * also handles incrementing the block counter in the input matrix. + */ +void chacha_block_generic(struct chacha_state *state, + u8 out[CHACHA_BLOCK_SIZE], int nrounds) +{ + struct chacha_state permuted_state = *state; + int i; + + chacha_permute(&permuted_state, nrounds); + + for (i = 0; i < ARRAY_SIZE(state->x); i++) + put_unaligned_le32(permuted_state.x[i] + state->x[i], + &out[i * sizeof(u32)]); + + state->x[12]++; +} +EXPORT_SYMBOL(chacha_block_generic); + +/** + * hchacha_block_generic - abbreviated ChaCha core, for XChaCha + * @state: input state matrix + * @out: the output words + * @nrounds: number of rounds (20 or 12; 20 is recommended) + * + * HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step + * towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha + * skips the final addition of the initial state, and outputs only certain words + * of the state. It should not be used for streaming directly. + */ +void hchacha_block_generic(const struct chacha_state *state, + u32 out[HCHACHA_OUT_WORDS], int nrounds) +{ + struct chacha_state permuted_state = *state; + + chacha_permute(&permuted_state, nrounds); + + memcpy(&out[0], &permuted_state.x[0], 16); + memcpy(&out[4], &permuted_state.x[12], 16); +} +EXPORT_SYMBOL(hchacha_block_generic); |