Add an internal-representation no-op function.

[u/mdw/catacomb] / pss.c

/* -*-c-*-
 *
 * $Id: pss.c,v 1.1 2000/07/20 20:13:38 mdw Exp $
 *
 * Probabistic signature scheme
 *
 * (c) 2000 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * Catacomb is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: pss.c,v $
 * Revision 1.1  2000/07/20 20:13:38  mdw
 * Added Bellare and Rogaway's PSS encoding for RSA signatures.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <string.h>

#include <mLib/alloc.h>
#include <mLib/bits.h>
#include <mLib/dstr.h>

#include "gcipher.h"
#include "ghash.h"
#include "grand.h"
#include "pss.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @pss_presign@ --- *
 *
 * Arguments:	@pss *pp@ = pointer to PSS parameter block
 *
 * Returns:	An initialized generic hash context.
 *
 * Use:		Initializes a hash function for signing with PSS.  A salt is
 *		chosen and written into the parameter block.
 */

ghash *pss_presign(pss *pp)
{
  size_t hsz = pp->ch->hashsz;
  octet *salt = xmalloc(hsz);
  ghash *h;

  pp->r->ops->fill(pp->r, salt, hsz);
  pp->salt = salt;
  h = pp->ch->init();
  h->ops->hash(h, salt, hsz);
  return (h);
}

/* --- @pss_encode@ --- *
 *
 * Arguments:	@const void *msg@ = pointer to message (hash) data
 *		@size_t msz@ = size of message data
 *		@void *buf@ = pointer to output buffer
 *		@size_t sz@ = size of the output buffer
 *		@void *p@ = pointer to PSS parameter block
 *
 * Returns:	Zero of all went well, negative on failure.
 *
 * Use:		Implements the operation @EMSA-PSS-ENCODE@, as defined in
 *		PKCS#1 v. 2.1 draft 1.
 */

int pss_encode(const void *msg, size_t msz, void *buf, size_t sz, void *p)
{
  pss *pp = p;
  octet *q, *mq, *qq;
  gcipher *c;
  size_t hsz = pp->ch->hashsz;
  size_t n;

  /* --- Ensure that everything is sensibly sized --- */

  if (hsz + msz + 1 > sz)
    return (-1);

  /* --- Fill in the initial buffer --- */

  q = buf;
  *q++ = 0; sz--;
  mq = q + msz;
  qq = q + sz;
  n = sz - msz;
  memcpy(q, msg, msz);
  if (pp->salt)
    memcpy(mq, pp->salt, hsz);
  else
    memset(mq, 0, hsz);
  memset(mq + hsz, 0, n - hsz);

  /* --- Do the encryption --- */

  c = pp->cc->init(msg, msz);
  c->ops->encrypt(c, mq, mq, n);
  c->ops->destroy(c);

  /* --- Done --- */

  return (0);
}

/* --- @pss_decode@ --- *
 *
 * Arguments:	@const void *buf@ = pointer to encoded buffer
 *		@size_t sz@ = size of the encoded byffer
 *		@dstr *d@ = pointer to destination string
 *		@void *p@ = pointer to PSS parameter block
 *
 * Returns:	The length of the output string (hash) if successful,
 *		negative on failure.
 *
 * Use:		Implements most of the operation @EMSA_PSS_VERIFY@, as
 *		defined in PCSK#1 v. 2.1 draft 1.  The salt value is filled
 *		in ready for hashing of the data to start.
 */

int pss_decode(const void *buf, size_t sz, dstr *d, void *p)
{
  pss *pp = p;
  gcipher *c;
  octet *q, *mq, *qq;
  octet *ppp;
  size_t n;
  size_t hsz = pp->ch->hashsz;
  int rc = -1;

  /* --- Ensure that the block is large enough --- */

  if (sz < 2 * hsz + 1)
    return (-1);

  q = x_alloc(d->a, sz);
  memcpy(q, buf, sz);

  /* --- Recover the salt --- */

  if (*q++ != 0)
    goto fail;
  sz--;
  mq = q + hsz;
  qq = q + sz;
  n = sz - hsz;
  c = pp->cc->init(q, hsz);
  c->ops->decrypt(c, mq, mq, n);
  c->ops->destroy(c);

  /* --- Now check the recovery --- */

  ppp = mq + hsz;
  while (ppp < qq) {
    if (*ppp)
      goto fail;
    ppp++;
  }

  /* --- Done --- */

  if (pp->salt) {
    if (memcmp(pp->salt, mq, hsz) != 0)
      goto fail;
  } else {
    qq = xmalloc(hsz);
    memcpy(qq, mq, hsz);
    pp->salt = qq;
  }
  dstr_putm(d, q, hsz);
  rc = hsz;

fail:
  x_free(d->a, q - 1);
  return (rc);
}

/* --- @pss_preverify@ --- *
 *
 * Arguments:	@pss *pp@ = pointer to PSS parameter block
 *
 * Returns:	An initialized generic hash context.
 *
 * Use:		Initializes a hash function for use with PSS.  A salt is
 *		read from the parameter block, where @pss_decode@ should have
 *		left it.
 */

ghash *pss_preverify(pss *pp)
{
  size_t hsz = pp->ch->hashsz;
  ghash *h = pp->ch->init();
  h->ops->hash(h, pp->salt, hsz);
  return (h);
}

/* --- @pss_done@ --- *
 *
 * Arguments:	@pss *pp@ = pointer to PSS parameter block
 *
 * Returns:	---
 *
 * Use:		Disposes of a PSS parameter block once it's finished with.
 */

void pss_done(pss *pp)
{
  if (pp->salt) {
    xfree(pp->salt);
    pp->salt = 0;
  }
}

/*----- That's all, folks -------------------------------------------------*/