89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
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/**
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* WinPR: Windows Portable Runtime
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* RC4 implementation for RDP
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*
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* Copyright 2023 Armin Novak <anovak@thincast.com>
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* Copyright 2023 Thincast Technologies GmbH
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <winpr/assert.h>
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#include "rc4.h"
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#define CTX_SIZE 256
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struct winpr_int_rc4_ctx
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{
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size_t i;
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size_t j;
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BYTE s[CTX_SIZE];
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BYTE t[CTX_SIZE];
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};
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static void swap(BYTE* p1, BYTE* p2)
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{
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BYTE t = *p1;
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*p1 = *p2;
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*p2 = t;
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}
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winpr_int_RC4_CTX* winpr_int_rc4_new(const BYTE* key, size_t keylength)
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{
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winpr_int_RC4_CTX* ctx = calloc(1, sizeof(winpr_int_RC4_CTX));
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if (!ctx)
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return NULL;
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for (size_t i = 0; i < CTX_SIZE; i++)
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{
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ctx->s[i] = i;
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ctx->t[i] = key[i % keylength];
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}
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size_t j = 0;
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for (size_t i = 0; i < CTX_SIZE; i++)
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{
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j = (j + ctx->s[i] + ctx->t[i]) % CTX_SIZE;
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swap(&ctx->s[i], &ctx->s[j]);
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}
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return ctx;
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}
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void winpr_int_rc4_free(winpr_int_RC4_CTX* ctx)
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{
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free(ctx);
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}
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BOOL winpr_int_rc4_update(winpr_int_RC4_CTX* ctx, size_t length, const BYTE* input, BYTE* output)
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{
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WINPR_ASSERT(ctx);
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UINT32 t1 = ctx->i;
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UINT32 t2 = ctx->j;
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for (size_t i = 0; i < length; i++)
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{
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t1 = (t1 + 1) % CTX_SIZE;
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t2 = (t2 + ctx->s[t1]) % CTX_SIZE;
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swap(&ctx->s[t1], &ctx->s[t2]);
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const size_t idx = ((size_t)ctx->s[t1] + ctx->s[t2]) % CTX_SIZE;
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const BYTE val = ctx->s[idx];
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const BYTE out = *input++ ^ val;
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*output++ = out;
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}
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ctx->i = t1;
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ctx->j = t2;
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return TRUE;
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}
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