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1 /**
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2 * This file is part of the dcrypt project.
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3 *
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4 * Copyright: Copyright (C) dcrypt contributors 2008. All rights reserved.
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5 * License: MIT
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6 * Authors: Thomas Dixon
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7 */
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8
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9 module dcrypt.crypto.padding.PKCS7;
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10
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11 import dcrypt.crypto.BlockCipherPadding;
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12
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13 /**
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14 * This class implements the padding scheme described in PKCS7
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15 * from RSA Security. Ex. [... 0x03, 0x03, 0x03]
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16 */
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17 class PKCS7 : BlockCipherPadding {
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18 char[] name() {
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19 return "PKCS7";
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20 }
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21
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22 /* Assumes input_ is a multiple of the underlying
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23 * block cipher's block size.
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24 */
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25 uint padBlock(void[] input_, uint inOff) {
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26 ubyte[] input = cast(ubyte[]) input_;
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27
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28 ubyte len = (input.length - inOff);
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29
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30 input[inOff..input.length] = len;
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31
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32 return len;
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33 }
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34
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35 uint padLength(void[] input_) {
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36 ubyte[] input = cast(ubyte[]) input_;
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37
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38 ubyte len = input[input.length-1];
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39
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40 if (len > input.length || len == 0)
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41 throw new InvalidPaddingError(name()~": Incorrect padding.");
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42
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43 uint limit = input.length;
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44 for (int i = 0; i < len; i++)
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45 if (input[--limit] != len)
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46 throw new InvalidPaddingError(
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47 name()~": Pad value does not match pad length.");
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48 return len;
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49 }
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50 }
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