66 lines
2.8 KiB
C
66 lines
2.8 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "./../include/PKCS7.h"
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PKCS7_Padding* addPadding(const void* const data, const unsigned int dataLength, const unsigned char BLOCK_SIZE)
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{
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if (0 == BLOCK_SIZE)
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{
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puts("ERROR: block size value must be 0 < BLOCK_SIZE < 256");
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exit(-1);
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}
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PKCS7_Padding* paddingResult = (PKCS7_Padding*) malloc(sizeof(PKCS7_Padding));
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if (NULL == paddingResult)
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{
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perror("problem with PKCS7_Padding* paddingResult"); /* if memory allocation failed */
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exit(-1);
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}
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unsigned char paddingBytesAmount = BLOCK_SIZE - (dataLength % BLOCK_SIZE); /* number of bytes to be appended */
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paddingResult->valueOfByteForPadding = paddingBytesAmount; /* according to the PKCS7 */
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paddingResult->dataLengthWithPadding = dataLength + paddingBytesAmount; /* size of the final result */
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unsigned char* dataWithPadding = (unsigned char*) malloc(paddingResult->dataLengthWithPadding);
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if (NULL == paddingResult)
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{
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perror("problem with unsigned char* dataWithPadding"); /* if memory allocation failed */
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exit(-1);
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}
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memcpy(dataWithPadding, data, dataLength); /* copying the original data for further adding padding */
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for (int i = 0; i < paddingBytesAmount; i++)
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{
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dataWithPadding[dataLength + i] = paddingResult->valueOfByteForPadding; /* adding padding bytes */
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}
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paddingResult->dataWithPadding = dataWithPadding;
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return paddingResult;
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}
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PKCS7_unPadding* removePadding(const void* const data, const unsigned int dataLength)
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{
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PKCS7_unPadding* unpaddingResult = (PKCS7_unPadding*) malloc(sizeof(PKCS7_unPadding));
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if (NULL == unpaddingResult)
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{
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perror("problem with PKCS7_Padding* unpaddingResult"); /* if memory allocation failed */
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exit(-1);
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}
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unsigned char paddingBytesAmount = *((unsigned char *)(data + dataLength - 1)); /* last byte contains length of data to be deleted */
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unpaddingResult->valueOfRemovedByteFromData = paddingBytesAmount; /* according to the PKCS7 */
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unpaddingResult->dataLengthWithoutPadding = dataLength - paddingBytesAmount; /* size of the final result */
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unsigned char* dataWithoutPadding = (unsigned char*) malloc(unpaddingResult->dataLengthWithoutPadding);
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if (NULL == dataWithoutPadding)
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{
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perror("problem with unsigned char* dataWithoutPadding"); /* if memory allocation failed */
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exit(-1);
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}
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memcpy(dataWithoutPadding, data, unpaddingResult->dataLengthWithoutPadding); /* taking data without bytes containing the padding value */
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unpaddingResult->dataWithoutPadding = dataWithoutPadding;
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return unpaddingResult;
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} |