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lib/chacha.c
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// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* The "hash function" used as the core of the ChaCha stream cipher (RFC7539) |
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* * Copyright (C) 2015 Martin Willi |
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*/ #include <linux/kernel.h> #include <linux/export.h> #include <linux/bitops.h> #include <linux/cryptohash.h> #include <asm/unaligned.h> |
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#include <crypto/chacha.h> |
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static void chacha_permute(u32 *x, int nrounds) |
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{ |
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int i; |
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/* whitelist the allowed round counts */ |
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WARN_ON_ONCE(nrounds != 20 && nrounds != 12); |
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for (i = 0; i < nrounds; i += 2) { |
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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); |
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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); |
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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); |
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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); |
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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); |
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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); |
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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); |
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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); |
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} |
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} /** |
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* chacha_block - generate one keystream block and increment block counter |
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* @state: input state matrix (16 32-bit words) * @stream: output keystream block (64 bytes) |
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* @nrounds: number of rounds (20 or 12; 20 is recommended) |
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* |
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* 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. |
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*/ |
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void chacha_block(u32 *state, u8 *stream, int nrounds) |
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{ u32 x[16]; int i; memcpy(x, state, 64); |
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chacha_permute(x, nrounds); |
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for (i = 0; i < ARRAY_SIZE(x); i++) |
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put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]); |
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state[12]++; } |
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EXPORT_SYMBOL(chacha_block); |
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/** |
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* hchacha_block - abbreviated ChaCha core, for XChaCha |
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* @in: input state matrix (16 32-bit words) * @out: output (8 32-bit words) |
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* @nrounds: number of rounds (20 or 12; 20 is recommended) |
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* |
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* 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. |
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*/ |
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void hchacha_block(const u32 *in, u32 *out, int nrounds) |
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{ u32 x[16]; memcpy(x, in, 64); |
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chacha_permute(x, nrounds); |
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memcpy(&out[0], &x[0], 16); memcpy(&out[4], &x[12], 16); } |
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EXPORT_SYMBOL(hchacha_block); |