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https://github.com/torvalds/linux
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dc51f25752
Refactor the core rc4 handling so we can move most users to a library interface, permitting us to drop the cipher interface entirely in a future patch. This is part of an effort to simplify the crypto API and improve its robustness against incorrect use. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
74 lines
1.1 KiB
C
74 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Cryptographic API
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*
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* ARC4 Cipher Algorithm
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*
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* Jon Oberheide <jon@oberheide.org>
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*/
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#include <crypto/arc4.h>
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#include <linux/module.h>
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int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
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{
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int i, j = 0, k = 0;
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ctx->x = 1;
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ctx->y = 0;
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for (i = 0; i < 256; i++)
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ctx->S[i] = i;
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for (i = 0; i < 256; i++) {
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u32 a = ctx->S[i];
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j = (j + in_key[k] + a) & 0xff;
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ctx->S[i] = ctx->S[j];
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ctx->S[j] = a;
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if (++k >= key_len)
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k = 0;
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}
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return 0;
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}
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EXPORT_SYMBOL(arc4_setkey);
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void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
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{
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u32 *const S = ctx->S;
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u32 x, y, a, b;
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u32 ty, ta, tb;
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if (len == 0)
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return;
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x = ctx->x;
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y = ctx->y;
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a = S[x];
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y = (y + a) & 0xff;
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b = S[y];
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do {
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S[y] = a;
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a = (a + b) & 0xff;
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S[x] = b;
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x = (x + 1) & 0xff;
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ta = S[x];
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ty = (y + ta) & 0xff;
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tb = S[ty];
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*out++ = *in++ ^ S[a];
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if (--len == 0)
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break;
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y = ty;
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a = ta;
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b = tb;
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} while (true);
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ctx->x = x;
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ctx->y = y;
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}
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EXPORT_SYMBOL(arc4_crypt);
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MODULE_LICENSE("GPL");
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