114 lines
3.0 KiB
C
114 lines
3.0 KiB
C
//
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// RC4 functions for PDFio.
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//
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// Copyright © 2021 by Michael R Sweet.
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//
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// Original code by Tim Martin
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// Copyright © 1999 by Carnegie Mellon University, All Rights Reserved
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//
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// Permission to use, copy, modify, and distribute this software and its
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// documentation for any purpose and without fee is hereby granted,
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// provided that the above copyright notice appear in all copies and that
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// both that copyright notice and this permission notice appear in
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// supporting documentation, and that the name of Carnegie Mellon
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// University not be used in advertising or publicity pertaining to
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// distribution of the software without specific, written prior
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// permission.
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//
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// CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
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// THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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// FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE FOR
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// ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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// OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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//
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#include "pdfio-private.h"
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//
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// '_pdfioCryptoRC4Init()' - Initialize an RC4 context with the specified key.
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//
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void
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_pdfioCryptoRC4Init(
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_pdfio_rc4_t *ctx, // IO - Context
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const uint8_t *key, // I - Key
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size_t keylen) // I - Length of key
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{
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size_t i; // Looping var
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uint8_t j, // S box counter
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tmp; // Temporary variable
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// Fill in linearly s0=0, s1=1, ...
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for (i = 0; i < 256; i ++)
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ctx->sbox[i] = (uint8_t)i;
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for (i = 0, j = 0; i < 256; i ++)
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{
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// j = (j + Si + Ki) mod 256
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j += ctx->sbox[i] + key[i % keylen];
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// Swap Si and Sj...
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tmp = ctx->sbox[i];
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ctx->sbox[i] = ctx->sbox[j];
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ctx->sbox[j] = tmp;
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}
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// Initialize counters to 0 and return...
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ctx->i = 0;
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ctx->j = 0;
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}
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//
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// '_pdfioCryptoRC4Crypt()' - De/encrypt the given buffer.
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//
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// "inbuffer" and "outbuffer" can point to the same memory.
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//
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size_t // O - Number of output bytes
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_pdfioCryptoRC4Crypt(
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_pdfio_rc4_t *ctx, // I - Context
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uint8_t *outbuffer, // I - Output buffer
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const uint8_t *inbuffer, // I - Input buffer
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size_t len) // I - Size of buffers
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{
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uint8_t tmp, // Swap variable
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i, j, // Looping vars
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t; // Current S box
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size_t outbytes = len; // Number of output bytes
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// Loop through the entire buffer...
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i = ctx->i;
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j = ctx->j;
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while (len > 0)
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{
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// Get the next S box indices...
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i ++;
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j += ctx->sbox[i];
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// Swap Si and Sj...
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tmp = ctx->sbox[i];
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ctx->sbox[i] = ctx->sbox[j];
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ctx->sbox[j] = tmp;
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// Get the S box index for this byte...
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t = ctx->sbox[i] + ctx->sbox[j];
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// Encrypt using the S box...
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*outbuffer++ = *inbuffer++ ^ ctx->sbox[t];
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len --;
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}
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// Copy current S box indices back to context...
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ctx->i = i;
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ctx->j = j;
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return (outbytes);
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}
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