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−/*
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−hmac_md5 -- implements RFC 2104
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−
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−Copyright 2010, markus schnalke <meillo@marmaro.de>
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−
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−Permission to use, copy, modify, and/or distribute this software for any
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−purpose with or without fee is hereby granted, provided that the above
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−copyright notice and this permission notice appear in all copies.
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−
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−THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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−WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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−MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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−ANY SPECIAL, DIRECT, 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 OF
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−OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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−
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−
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−My motivation to write this code was the lack of a nicely licensed
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−hmac_md5 function in C. I programmed it following the RFC's text.
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−Obviously this code is highly similar to the sample code of the RFC.
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−The code is tested against the test vectors of the RFC. Wikipedia's
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−HMAC page helped me to understand the algorithm better.
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−
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−This hmac_md5 function requires an OpenSSL-compatible MD5
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−implementation. There are Public Domain MD5 implementations by Colin
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−Plumb and by Solar Designer. You probably want to use one of these.
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−*/
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−
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−#include <string.h>
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−#include "md5.h"
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−
+
−
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−const int blocksize = 64;
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−const int hashsize = 16;
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−
+
−
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−/*
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−The computed HMAC will be written to `digest'.
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−Ensure digest points to hashsize bytes of allocated memory.
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−*/
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−void
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−hmac_md5(unsigned char* text, int textlen, unsigned char* key, int keylen, unsigned char* digest)
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−{
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−	int i;
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−	MD5_CTX context;
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−	unsigned char ipad[blocksize];
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−	unsigned char opad[blocksize];
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−
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−	/* too long keys are replaced by their hash value */
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−	if (keylen > blocksize) {
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−		MD5_Init(&context);
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−		MD5_Update(&context, key, keylen);
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−		MD5_Final(digest, &context);
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−		key = digest;
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−		keylen = hashsize;
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−	}
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−
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−        /* copy the key into the pads */
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−	memset(ipad, 0, sizeof(ipad));
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−	memcpy(ipad, key, keylen);
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−
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−	memset(opad, 0, sizeof(opad));
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−	memcpy(opad, key, keylen);
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−
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−        /* xor the pads with their ``basic'' value */
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−	for (i=0; i<blocksize; i++) {
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−		ipad[i] ^= 0x36;
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−		opad[i] ^= 0x5c;
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−	}
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−
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−	/* inner pass (ipad ++ message) */
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−	MD5_Init(&context);
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−	MD5_Update(&context, ipad, sizeof(ipad));
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−	MD5_Update(&context, text, textlen);
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−	MD5_Final(digest, &context);
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−
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−	/* outer pass (opad ++ result of inner pass) */
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−	MD5_Init(&context);
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−	MD5_Update(&context, opad, sizeof(opad));
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−	MD5_Update(&context, digest, hashsize);
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−	MD5_Final(digest, &context);
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−}