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px-hmac.c

/*
 * px-hmac.c
 *          HMAC implementation.
 *
 * Copyright (c) 2001 Marko Kreen
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.      IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $PostgreSQL$
 */

#include "postgres.h"

#include "px.h"

#define HMAC_IPAD 0x36
#define HMAC_OPAD 0x5C

static unsigned
hmac_result_size(PX_HMAC * h)
{
      return px_md_result_size(h->md);
}

static unsigned
hmac_block_size(PX_HMAC * h)
{
      return px_md_block_size(h->md);
}

static void
hmac_init(PX_HMAC * h, const uint8 *key, unsigned klen)
{
      unsigned    bs,
                        hlen,
                        i;
      uint8    *keybuf;
      PX_MD    *md = h->md;

      bs = px_md_block_size(md);
      hlen = px_md_result_size(md);
      keybuf = px_alloc(bs);
      memset(keybuf, 0, bs);

      if (klen > bs)
      {
            px_md_update(md, key, klen);
            px_md_finish(md, keybuf);
            px_md_reset(md);
      }
      else
            memcpy(keybuf, key, klen);

      for (i = 0; i < bs; i++)
      {
            h->p.ipad[i] = keybuf[i] ^ HMAC_IPAD;
            h->p.opad[i] = keybuf[i] ^ HMAC_OPAD;
      }

      memset(keybuf, 0, bs);
      px_free(keybuf);

      px_md_update(md, h->p.ipad, bs);
}

static void
hmac_reset(PX_HMAC * h)
{
      PX_MD    *md = h->md;
      unsigned    bs = px_md_block_size(md);

      px_md_reset(md);
      px_md_update(md, h->p.ipad, bs);
}

static void
hmac_update(PX_HMAC * h, const uint8 *data, unsigned dlen)
{
      px_md_update(h->md, data, dlen);
}

static void
hmac_finish(PX_HMAC * h, uint8 *dst)
{
      PX_MD    *md = h->md;
      unsigned    bs,
                        hlen;
      uint8    *buf;

      bs = px_md_block_size(md);
      hlen = px_md_result_size(md);

      buf = px_alloc(hlen);

      px_md_finish(md, buf);

      px_md_reset(md);
      px_md_update(md, h->p.opad, bs);
      px_md_update(md, buf, hlen);
      px_md_finish(md, dst);

      memset(buf, 0, hlen);
      px_free(buf);
}

static void
hmac_free(PX_HMAC * h)
{
      unsigned    bs;

      bs = px_md_block_size(h->md);
      px_md_free(h->md);

      memset(h->p.ipad, 0, bs);
      memset(h->p.opad, 0, bs);
      px_free(h->p.ipad);
      px_free(h->p.opad);
      px_free(h);
}


/* PUBLIC FUNCTIONS */

int
px_find_hmac(const char *name, PX_HMAC ** res)
{
      int               err;
      PX_MD    *md;
      PX_HMAC    *h;
      unsigned    bs;

      err = px_find_digest(name, &md);
      if (err)
            return err;

      bs = px_md_block_size(md);
      if (bs < 2)
      {
            px_md_free(md);
            return PXE_HASH_UNUSABLE_FOR_HMAC;
      }

      h = px_alloc(sizeof(*h));
      h->p.ipad = px_alloc(bs);
      h->p.opad = px_alloc(bs);
      h->md = md;

      h->result_size = hmac_result_size;
      h->block_size = hmac_block_size;
      h->reset = hmac_reset;
      h->update = hmac_update;
      h->finish = hmac_finish;
      h->free = hmac_free;
      h->init = hmac_init;

      *res = h;

      return 0;
}

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