Merge branch 'master' of git+ssh://metalzone.distorted.org.uk/~mdw/public-git/catacomb/

[u/mdw/catacomb] / gcipher.h

/* -*-c-*-
 *
 * $Id: gcipher.h,v 1.5 2004/04/21 00:37:32 mdw Exp $
 *
 * Generic symmetric cipher interface
 *
 * (c) 1999 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.
 */

#ifndef CATACOMB_GCIPHER_H
#define CATACOMB_GCIPHER_H

#ifdef __cplusplus
  extern "C" {
#endif

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

#include <stddef.h>

#include <mLib/bits.h>

/*----- Generic symmetric cipher interface --------------------------------*/

typedef struct gcipher {
  const struct gcipher_ops *ops;	/* Pointer to cipher operations */
} gcipher;

typedef struct gcipher_ops {
  const struct gccipher *c;		/* Pointer to cipher class */
  void (*encrypt)(gcipher */*c*/, const void */*s*/,
		  void */*t*/, size_t /*sz*/);
  void (*decrypt)(gcipher */*c*/, const void */*s*/,
		  void */*t*/, size_t /*sz*/);
  void (*destroy)(gcipher */*c*/);
  void (*setiv)(gcipher */*c*/, const void */*iv*/);
  void (*bdry)(gcipher */*c*/);
} gcipher_ops;

typedef struct gccipher {
  const char *name;			/* Cipher name */
  const octet *keysz;			/* Preferred key size table */
  size_t blksz;				/* Block size or zero if none */
  gcipher *(*init)(const void */*k*/, size_t /*sz*/);
} gccipher;

#define GC_INIT(cc, k, sz)	(cc)->init((k), (sz))
#define GC_CLASS(cc)		(cc)->ops->c
#define GC_ENCRYPT(c, s, t, sz)	(c)->ops->encrypt((c), (s), (t), (sz))
#define GC_DECRYPT(c, s, t, sz)	(c)->ops->decrypt((c), (s), (t), (sz))
#define GC_DESTROY(c)		(c)->ops->destroy((c))
#define GC_SETIV(c, iv)		(c)->ops->setiv((c), (iv))
#define GC_BDRY(c)		(c)->ops->bdry((c))

/*----- Key size management -----------------------------------------------*/

/* --- Key size type constants --- *
 *
 * A key size limitation is an array of bytes.  The first byte describes the
 * kind of limitation on the key size %$k$%; the rest are argument bytes
 * %$a_i$%, for %$i \ge 0$%.  In all cases, %$a_0$% is the `recommended' key
 * size.
 *
 *   * @KSZ_ANY@ means there is no restriction.
 *
 *   * @KSZ_RANGE@ requires that %$k \ge a_1$%, %$k \equiv 0 \pmod{a_3}$%,
 *     and, if %$a_2 \ne 0$%, %$k \le a_2$%.
 *
 *   * @KSZ_SET@ requires that %$k \in {\,a_i\,}$%.
 */

enum {
  KSZ_ANY,				/* Allows any key at all */
  KSZ_RANGE,				/* Allows keys within a range */
  KSZ_SET				/* Allows specific sizes of keys */
};

/* --- @keysz@ --- *
 *
 * Arguments:	@size_t sz@ = a proposed key size, or zero
 *		@const octet *ksz@ = pointer to key size table
 *
 * Returns:	See below.
 *
 * Use:		Returns a sensible key size.  If @sz@ is nonzero, it is
 *		interpreted as an amount (in bytes) of key material which the
 *		caller has available, and the return value is either the
 *		largest allowable key size less than or equal to the caller's
 *		size, or zero if there is no valid key length small enough.
 *		If @sz@ is zero, the function returns a `recommended' key
 *		size.
 */

extern size_t keysz(size_t /*sz*/, const octet */*ksz*/);

#define KSZ_CHECK(pre, sz) (keysz((sz), pre##_keysz) == (sz))
#define KSZ_ASSERT(pre, sz)						\
  assert(((void)"Bad key size for " #pre, KSZ_CHECK(pre, sz)))

/*----- Tables ------------------------------------------------------------*/

extern const gccipher *const gciphertab[];

/* --- @gcipher_byname@ --- *
 *
 * Arguments:	@const char *p@ = pointer to name string
 *
 * Returns:	The named cipher class, or null.
 */

extern const gccipher *gcipher_byname(const char */*p*/);

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

#ifdef __cplusplus
  }
#endif

#endif