93 lines
2.7 KiB
C
93 lines
2.7 KiB
C
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/*
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* Copyright (c) 2007, Cameron Rich
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* * Neither the name of the axTLS project nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* An implementation of the RC4/ARC4 algorithm.
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* Originally written by Christophe Devine.
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*/
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#include <string.h>
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#include "os_port.h"
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#include "crypto.h"
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/**
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* Get ready for an encrypt/decrypt operation
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*/
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void RC4_setup(RC4_CTX *ctx, const uint8_t *key, int length)
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{
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int i, j = 0, k = 0, a;
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uint8_t *m;
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ctx->x = 0;
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ctx->y = 0;
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m = ctx->m;
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for (i = 0; i < 256; i++)
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m[i] = i;
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for (i = 0; i < 256; i++)
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{
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a = m[i];
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j = (uint8_t)(j + a + key[k]);
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m[i] = m[j];
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m[j] = a;
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if (++k >= length)
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k = 0;
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}
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}
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/**
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* Perform the encrypt/decrypt operation (can use it for either since
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* this is a stream cipher).
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* NOTE: *msg and *out must be the same pointer (performance tweak)
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*/
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void RC4_crypt(RC4_CTX *ctx, const uint8_t *msg, uint8_t *out, int length)
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{
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int i;
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uint8_t *m, x, y, a, b;
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x = ctx->x;
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y = ctx->y;
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m = ctx->m;
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for (i = 0; i < length; i++)
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{
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a = m[++x];
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y += a;
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m[x] = b = m[y];
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m[y] = a;
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out[i] ^= m[(uint8_t)(a + b)];
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}
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ctx->x = x;
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ctx->y = y;
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}
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