/* $Id: hmac_md5.c,v 1.2 2003/10/20 18:59:57 tomcollins Exp $ */#include "global.h"#include "md5.h"/*** Function: hmac_md5*/void hmac_md5(text, text_len, key, key_len, digest)unsigned char*  text;                /* pointer to data stream */int             text_len;            /* length of data stream */unsigned char*  key;                 /* pointer to authentication key */int             key_len;             /* length of authentication key */unsigned char   *digest;              /* caller digest to be filled in */{        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 is longer than 64 bytes reset it to key=MD5(key) */        if (key_len > 64) {                MD5_CTX      tctx;                MD5Init(&tctx);                MD5Update(&tctx, key, key_len);                MD5Final(tk, &tctx);                key = tk;                key_len = 16;        }        /*         * the HMAC_MD5 transform looks like:         *         * MD5(K XOR opad, MD5(K XOR ipad, text))         *         * where K is an n byte key         * ipad is the byte 0x36 repeated 64 times         * opad is the byte 0x5c repeated 64 times         * and text is the data being protected         */        /* start out by storing key in pads */        bzero( k_ipad, sizeof k_ipad);        bzero( k_opad, sizeof k_opad);        bcopy( key, k_ipad, key_len);        bcopy( key, k_opad, key_len);        /* XOR key with ipad and opad values */        for (i=0; i<64; i++) {                k_ipad[i] ^= 0x36;                k_opad[i] ^= 0x5c;        }        /*         * perform inner MD5         */        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 */        /*         * perform outer MD5         */        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 */}