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Currently, our generic ChaCha implementation consists of a permute function in lib/chacha.c that operates on the 64-byte ChaCha state directly [and which is always included into the core kernel since it is used by the /dev/random driver], and the crypto API plumbing to expose it as a skcipher. In order to support in-kernel users that need the ChaCha streamcipher but have no need [or tolerance] for going through the abstractions of the crypto API, let's expose the streamcipher bits via a library API as well, in a way that permits the implementation to be superseded by an architecture specific one if provided. So move the streamcipher code into a separate module in lib/crypto, and expose the init() and crypt() routines to users of the library. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
36 lines
896 B
C
36 lines
896 B
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* The ChaCha stream cipher (RFC7539)
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*
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* Copyright (C) 2015 Martin Willi
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/module.h>
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#include <crypto/algapi.h> // for crypto_xor_cpy
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#include <crypto/chacha.h>
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void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
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unsigned int bytes, int nrounds)
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{
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/* aligned to potentially speed up crypto_xor() */
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u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
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while (bytes >= CHACHA_BLOCK_SIZE) {
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chacha_block_generic(state, stream, nrounds);
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crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
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bytes -= CHACHA_BLOCK_SIZE;
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dst += CHACHA_BLOCK_SIZE;
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src += CHACHA_BLOCK_SIZE;
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}
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if (bytes) {
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chacha_block_generic(state, stream, nrounds);
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crypto_xor_cpy(dst, src, stream, bytes);
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}
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}
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EXPORT_SYMBOL(chacha_crypt_generic);
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MODULE_LICENSE("GPL");
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