#include <md5.h>
#include <stdarg.h>
#include <stdlib.h>
#include <strings.h>

#include "algs.h"

typedef struct hmac_md5_96_state HMAC_MD5_96_STATE;

struct hmac_md5_96_state {
  void *k_xor_opad;
  void *k_xor_ipad;
  } ;

static void *init_xor_block(const void *key, int keylen, unsigned char xorv)
{
 unsigned char kblk[64];
 int i;
 void *h;

 if (keylen > 64) abort();
 bcopy(key,&kblk[0],keylen);
 if (keylen < 64) bzero(&kblk[keylen],64-keylen);
 for (i=0;i<64;i++) kblk[i] ^= xorv;
 h = md5_init();
 md5_process_bytes(h,&kblk[0],64);
 return(h);
}

static void mac_va(HMAC_MD5_96_STATE *s, int nb, va_list ap, void *into)
{
 void *h;
 const void *buf;
 int len;
 unsigned char first[16];

 h = md5_clone(s->k_xor_ipad);
 for (;nb>0;nb--)
  { buf = va_arg(ap,const void *);
    len = va_arg(ap,int);
    md5_process_bytes(h,buf,len);
  }
 md5_result(h,&first[0]);
 h = md5_clone(s->k_xor_opad);
 md5_process_bytes(h,&first[0],16);
 md5_result(h,into);
}

static void *mac_hmac_md5_96_init(const void *key)
{
 HMAC_MD5_96_STATE *s;

 s = malloc(sizeof(HMAC_MD5_96_STATE));
 if (! s) return(0);
 s->k_xor_opad = init_xor_block(key,16,0x5c);
 s->k_xor_ipad = init_xor_block(key,16,0x36);
 return(s);
}

static int mac_hmac_md5_96_check(void *state, const void *vs, int nblk, ...)
{
 va_list ap;
 char tmp[16];

 va_start(ap,nblk);
 mac_va(state,nblk,ap,&tmp[0]);
 va_end(ap);
 return(!bcmp(&tmp[0],vs,12));
}

static void mac_hmac_md5_96_gen(void *state, void *into, int nblk, ...)
{
 va_list ap;
 char tmp[16];

 va_start(ap,nblk);
 mac_va(state,nblk,ap,&tmp[0]);
 va_end(ap);
 bcopy(&tmp[0],into,12);
}

static void mac_hmac_md5_96_done(void *state)
{
 HMAC_MD5_96_STATE *s;

 s = state;
 md5_drop(s->k_xor_opad);
 md5_drop(s->k_xor_ipad);
 free(s);
}

MACALG macalg_hmac_md5_96
 = { "hmac-md5-96", 12, 16,
     mac_hmac_md5_96_init,
     mac_hmac_md5_96_check,
     mac_hmac_md5_96_gen,
     mac_hmac_md5_96_done };