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245 lines
6.6 KiB
245 lines
6.6 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* POLYVAL: hash function for HCTR2. |
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* |
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* Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <[email protected]> |
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* Copyright (c) 2009 Intel Corp. |
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* Author: Huang Ying <[email protected]> |
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* Copyright 2021 Google LLC |
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*/ |
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/* |
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* Code based on crypto/ghash-generic.c |
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* |
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* POLYVAL is a keyed hash function similar to GHASH. POLYVAL uses a different |
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* modulus for finite field multiplication which makes hardware accelerated |
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* implementations on little-endian machines faster. POLYVAL is used in the |
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* kernel to implement HCTR2, but was originally specified for AES-GCM-SIV |
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* (RFC 8452). |
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* |
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* For more information see: |
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* Length-preserving encryption with HCTR2: |
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* https://eprint.iacr.org/2021/1441.pdf |
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* AES-GCM-SIV: Nonce Misuse-Resistant Authenticated Encryption: |
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* https://datatracker.ietf.org/doc/html/rfc8452 |
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* |
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* Like GHASH, POLYVAL is not a cryptographic hash function and should |
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* not be used outside of crypto modes explicitly designed to use POLYVAL. |
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* |
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* This implementation uses a convenient trick involving the GHASH and POLYVAL |
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* fields. This trick allows multiplication in the POLYVAL field to be |
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* implemented by using multiplication in the GHASH field as a subroutine. An |
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* element of the POLYVAL field can be converted to an element of the GHASH |
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* field by computing x*REVERSE(a), where REVERSE reverses the byte-ordering of |
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* a. Similarly, an element of the GHASH field can be converted back to the |
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* POLYVAL field by computing REVERSE(x^{-1}*a). For more information, see: |
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* https://datatracker.ietf.org/doc/html/rfc8452#appendix-A |
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* |
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* By using this trick, we do not need to implement the POLYVAL field for the |
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* generic implementation. |
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* |
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* Warning: this generic implementation is not intended to be used in practice |
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* and is not constant time. For practical use, a hardware accelerated |
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* implementation of POLYVAL should be used instead. |
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* |
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*/ |
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#include <asm/unaligned.h> |
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#include <crypto/algapi.h> |
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#include <crypto/gf128mul.h> |
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#include <crypto/polyval.h> |
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#include <crypto/internal/hash.h> |
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#include <linux/crypto.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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struct polyval_tfm_ctx { |
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struct gf128mul_4k *gf128; |
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}; |
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struct polyval_desc_ctx { |
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union { |
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u8 buffer[POLYVAL_BLOCK_SIZE]; |
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be128 buffer128; |
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}; |
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u32 bytes; |
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}; |
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static void copy_and_reverse(u8 dst[POLYVAL_BLOCK_SIZE], |
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const u8 src[POLYVAL_BLOCK_SIZE]) |
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{ |
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u64 a = get_unaligned((const u64 *)&src[0]); |
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u64 b = get_unaligned((const u64 *)&src[8]); |
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put_unaligned(swab64(a), (u64 *)&dst[8]); |
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put_unaligned(swab64(b), (u64 *)&dst[0]); |
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} |
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/* |
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* Performs multiplication in the POLYVAL field using the GHASH field as a |
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* subroutine. This function is used as a fallback for hardware accelerated |
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* implementations when simd registers are unavailable. |
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* |
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* Note: This function is not used for polyval-generic, instead we use the 4k |
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* lookup table implementation for finite field multiplication. |
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*/ |
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void polyval_mul_non4k(u8 *op1, const u8 *op2) |
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{ |
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be128 a, b; |
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// Assume one argument is in Montgomery form and one is not. |
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copy_and_reverse((u8 *)&a, op1); |
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copy_and_reverse((u8 *)&b, op2); |
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gf128mul_x_lle(&a, &a); |
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gf128mul_lle(&a, &b); |
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copy_and_reverse(op1, (u8 *)&a); |
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} |
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EXPORT_SYMBOL_GPL(polyval_mul_non4k); |
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/* |
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* Perform a POLYVAL update using non4k multiplication. This function is used |
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* as a fallback for hardware accelerated implementations when simd registers |
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* are unavailable. |
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* |
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* Note: This function is not used for polyval-generic, instead we use the 4k |
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* lookup table implementation of finite field multiplication. |
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*/ |
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void polyval_update_non4k(const u8 *key, const u8 *in, |
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size_t nblocks, u8 *accumulator) |
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{ |
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while (nblocks--) { |
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crypto_xor(accumulator, in, POLYVAL_BLOCK_SIZE); |
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polyval_mul_non4k(accumulator, key); |
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in += POLYVAL_BLOCK_SIZE; |
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} |
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} |
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EXPORT_SYMBOL_GPL(polyval_update_non4k); |
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static int polyval_setkey(struct crypto_shash *tfm, |
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const u8 *key, unsigned int keylen) |
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{ |
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struct polyval_tfm_ctx *ctx = crypto_shash_ctx(tfm); |
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be128 k; |
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if (keylen != POLYVAL_BLOCK_SIZE) |
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return -EINVAL; |
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gf128mul_free_4k(ctx->gf128); |
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BUILD_BUG_ON(sizeof(k) != POLYVAL_BLOCK_SIZE); |
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copy_and_reverse((u8 *)&k, key); |
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gf128mul_x_lle(&k, &k); |
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ctx->gf128 = gf128mul_init_4k_lle(&k); |
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memzero_explicit(&k, POLYVAL_BLOCK_SIZE); |
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if (!ctx->gf128) |
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return -ENOMEM; |
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return 0; |
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} |
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static int polyval_init(struct shash_desc *desc) |
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{ |
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struct polyval_desc_ctx *dctx = shash_desc_ctx(desc); |
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memset(dctx, 0, sizeof(*dctx)); |
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return 0; |
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} |
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static int polyval_update(struct shash_desc *desc, |
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const u8 *src, unsigned int srclen) |
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{ |
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struct polyval_desc_ctx *dctx = shash_desc_ctx(desc); |
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const struct polyval_tfm_ctx *ctx = crypto_shash_ctx(desc->tfm); |
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u8 *pos; |
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u8 tmp[POLYVAL_BLOCK_SIZE]; |
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int n; |
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if (dctx->bytes) { |
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n = min(srclen, dctx->bytes); |
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pos = dctx->buffer + dctx->bytes - 1; |
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dctx->bytes -= n; |
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srclen -= n; |
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while (n--) |
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*pos-- ^= *src++; |
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if (!dctx->bytes) |
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gf128mul_4k_lle(&dctx->buffer128, ctx->gf128); |
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} |
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while (srclen >= POLYVAL_BLOCK_SIZE) { |
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copy_and_reverse(tmp, src); |
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crypto_xor(dctx->buffer, tmp, POLYVAL_BLOCK_SIZE); |
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gf128mul_4k_lle(&dctx->buffer128, ctx->gf128); |
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src += POLYVAL_BLOCK_SIZE; |
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srclen -= POLYVAL_BLOCK_SIZE; |
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} |
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if (srclen) { |
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dctx->bytes = POLYVAL_BLOCK_SIZE - srclen; |
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pos = dctx->buffer + POLYVAL_BLOCK_SIZE - 1; |
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while (srclen--) |
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*pos-- ^= *src++; |
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} |
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return 0; |
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} |
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static int polyval_final(struct shash_desc *desc, u8 *dst) |
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{ |
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struct polyval_desc_ctx *dctx = shash_desc_ctx(desc); |
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const struct polyval_tfm_ctx *ctx = crypto_shash_ctx(desc->tfm); |
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if (dctx->bytes) |
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gf128mul_4k_lle(&dctx->buffer128, ctx->gf128); |
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copy_and_reverse(dst, dctx->buffer); |
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return 0; |
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} |
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static void polyval_exit_tfm(struct crypto_tfm *tfm) |
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{ |
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struct polyval_tfm_ctx *ctx = crypto_tfm_ctx(tfm); |
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gf128mul_free_4k(ctx->gf128); |
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} |
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static struct shash_alg polyval_alg = { |
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.digestsize = POLYVAL_DIGEST_SIZE, |
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.init = polyval_init, |
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.update = polyval_update, |
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.final = polyval_final, |
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.setkey = polyval_setkey, |
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.descsize = sizeof(struct polyval_desc_ctx), |
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.base = { |
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.cra_name = "polyval", |
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.cra_driver_name = "polyval-generic", |
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.cra_priority = 100, |
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.cra_blocksize = POLYVAL_BLOCK_SIZE, |
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.cra_ctxsize = sizeof(struct polyval_tfm_ctx), |
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.cra_module = THIS_MODULE, |
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.cra_exit = polyval_exit_tfm, |
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}, |
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}; |
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static int __init polyval_mod_init(void) |
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{ |
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return crypto_register_shash(&polyval_alg); |
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} |
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static void __exit polyval_mod_exit(void) |
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{ |
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crypto_unregister_shash(&polyval_alg); |
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} |
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subsys_initcall(polyval_mod_init); |
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module_exit(polyval_mod_exit); |
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MODULE_LICENSE("GPL"); |
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MODULE_DESCRIPTION("POLYVAL hash function"); |
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MODULE_ALIAS_CRYPTO("polyval"); |
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MODULE_ALIAS_CRYPTO("polyval-generic");
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