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#include "byte.h"
#include "str.h"
#include "global.h"
#include "md5.h"
/**
@file hmac_md5
@brief caculates HMAC digest from challenge + password (DJB version)
@param input: unsigned char *text : pointer to challenge
int text_len : length of challenge
unsigned char *key : pointer to password
int key_len : length of password
output: unsigned char *digest: pointer to calculated digest
*/
void hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len, unsigned char *digest)
{
MD5_CTX context;
unsigned char k_ipad[65]; /* inner padding - key XORd with ipad */
unsigned char k_opad[65]; /* outer padding - key XORd with opad */
unsigned char tk[16];
int i;
if (key_len > 64) {
MD5_CTX tctx;
MD5Init(&tctx);
MD5Update(&tctx, key, key_len);
MD5Final(tk, &tctx);
key = tk;
key_len = 16;
}
byte_zero(k_ipad, sizeof(k_ipad));
byte_zero(k_opad, sizeof(k_opad));
byte_copy(k_ipad, key_len, key);
byte_copy(k_opad, key_len, key);
for (i = 0; i < 64; i++) {
k_ipad[i] ^= 0x36;
k_opad[i] ^= 0x5c;
}
MD5Init(&context); /* init context for 1st pass */
MD5Update(&context, k_ipad, 64); /* start with inner pad */
MD5Update(&context, text, text_len); /* then text of datagram */
MD5Final(digest, &context); /* finish up 1st pass */
MD5Init(&context); /* init context for 2nd pass */
MD5Update(&context, k_opad, 64); /* start with outer pad */
MD5Update(&context, digest, 16); /* then results of 1st hash */
MD5Final(digest, &context); /* finish up 2nd pass */
}
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