/*

  silchash.h 

  Author: Pekka Riikonen <priikone@silcnet.org>

  Copyright (C) 1997 - 2002 Pekka Riikonen

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; version 2 of the License.

  This program 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 General Public License for more details.

*/

#ifndef SILCHASH_H
#define SILCHASH_H

/****h* silccrypt/SILC Hash Interface
 *
 * DESCRIPTION
 *
 *    This is the interface for hash functions which are used to create
 *    message digests.  The routines are used in various cryptographic
 *    operations.  SILC Hash Interface is used for example by the
 *    SILC HMAC Interface (SilcHmac).
 *
 ***/

/****s* silccrypt/SilcHashAPI/SilcHash
 *
 * NAME
 * 
 *    typedef struct SilcHashStruct *SilcHash;
 *
 * DESCRIPTION
 *
 *    This context is the actual hash function context and is allocated
 *    by silc_hash_alloc and given as argument usually to all
 *    silc_hash_* functions.  It is freed by the silc_hash_free
 *    function.
 *
 ***/
typedef struct SilcHashStruct *SilcHash;

/****s* silccrypt/SilcHashAPI/SilcHashObject
 *
 * NAME
 * 
 *    typedef struct { ... } SilcHashObject;
 *
 * DESCRIPTION
 *
 *    This structure represents one hash function.  The hash function's
 *    name, digest length and block length are defined in the structure.
 *    This structure is then given as argument to the silc_hash_register.
 *    That function is used to register all hash functions into SILC.
 *    They can be then allocated by the name found in this structure by
 *    calling the silc_hash_alloc.
 *
 ***/
typedef struct {
  char *name;
  SilcUInt32 hash_len;
  SilcUInt32 block_len;

  void (*init)(void *);
  void (*update)(void *, const unsigned char *, SilcUInt32);
  void (*final)(void *, unsigned char *);
  void (*transform)(SilcUInt32 *, const unsigned char *);
  SilcUInt32 (*context_len)();
} SilcHashObject;

/* Marks for all hash functions. This can be used in silc_hash_unregister
   to unregister all hash function at once. */
#define SILC_ALL_HASH_FUNCTIONS ((SilcHashObject *)1)

/* Default hash functions for silc_hash_register_default(). */
extern DLLAPI const SilcHashObject silc_default_hash[];

/* Default HASH function in the SILC protocol */
#define SILC_DEFAULT_HASH "sha1"

/* Macros */

/* Following macros are used to implement the SILC Hash API. These
   macros should be used instead of declaring functions by hand. */

/* Function names in SILC Hash modules. The name of the hash function
   is appended into these names and used to the get correct symbol out
   of the module. All SILC Hash API compliant modules has to support
   these names as function names (use macros below to assure this). */
#define SILC_HASH_SIM_INIT "init"
#define SILC_HASH_SIM_UPDATE "update"
#define SILC_HASH_SIM_FINAL "final"
#define SILC_HASH_SIM_TRANSFORM "transform"
#define SILC_HASH_SIM_CONTEXT_LEN "context_len"

/* Macros that can be used to declare SILC Hash API functions. */
#define SILC_HASH_API_INIT(hash)					\
void silc_##hash##_init(void *context)
#define SILC_HASH_API_UPDATE(hash)					\
void silc_##hash##_update(void *context, const unsigned char *data,	\
                          SilcUInt32 len)
#define SILC_HASH_API_FINAL(hash)					\
void silc_##hash##_final(void *context, unsigned char *digest)
#define SILC_HASH_API_TRANSFORM(hash)					\
void silc_##hash##_transform(SilcUInt32 *state,	const unsigned char *buffer)
#define SILC_HASH_API_CONTEXT_LEN(hash)					\
SilcUInt32 silc_##hash##_context_len()

/* Prototypes */

/****f* silccrypt/SilcHashAPI/silc_hash_register
 *
 * SYNOPSIS
 *
 *    bool silc_hash_register(const SilcHashObject *hash);
 *
 * DESCRIPTION
 *
 *    Registers a new hash function into the SILC.  This function is used
 *    at the initialization of the SILC.  All registered hash functions
 *    should be unregistered with silc_hash_unregister.  The `hash' includes
 *    the name of the hash function, digest length and block length.  Usually
 *    this function is not called directly.  Instead, application can call
 *    the silc_hash_register_default to register all default hash functions
 *    that are builtin the sources.  Returns FALSE on error.
 *
 ***/
bool silc_hash_register(const SilcHashObject *hash);

/****f* silccrypt/SilcHashAPI/silc_hash_unregister
 *
 * SYNOPSIS
 *
 *    bool silc_hash_unregister(SilcHashObject *hash);
 *
 * DESCRIPTION
 *
 *    Unregister a hash function from SILC by the SilcHashObject `hash'.
 *    This should be called for all registered hash functions.  Returns
 *    FALSE on error.
 *
 ***/
bool silc_hash_unregister(SilcHashObject *hash);

/****f* silccrypt/SilcHashAPI/silc_hash_register_default
 *
 * SYNOPSIS
 *
 *    bool silc_hash_register_default(void);
 *
 * DESCRIPTION
 *
 *    Registers all default hash functions into the SILC.  These are the
 *    hash functions that are builtin in the sources.  See the list of
 *    default hash functions in the silchash.c source file.  The application
 *    may use this to register default hash functions if specific hash
 *    function in any specific order is not wanted (application's
 *    configuration usually may decide the order of the registration, in
 *    which case this function should not be used).
 *
 ***/
bool silc_hash_register_default(void);

/****f* silccrypt/SilcHashAPI/silc_hash_unregister_all
 *
 * SYNOPSIS
 *
 *    bool silc_hash_unregister_all(void);
 *
 * DESCRIPTION
 *
 *    Unregisters all registered hash functions.
 *
 ***/
bool silc_hash_unregister_all(void);

/****f* silccrypt/SilcHashAPI/silc_hash_alloc
 *
 * SYNOPSIS
 *
 *    bool silc_hash_alloc(const unsigned char *name, SilcHash *new_hash);
 *
 * DESCRIPTION
 *
 *    Allocates a new SilcHash object of name of `name'.  The new allocated
 *    hash function is returned into `new_hash' pointer.  This function
 *    returns FALSE if such hash function does not exist.
 *
 ***/
bool silc_hash_alloc(const unsigned char *name, SilcHash *new_hash);

/****f* silccrypt/SilcHashAPI/silc_hash_free
 *
 * SYNOPSIS
 *
 *    void silc_hash_free(SilcHash hash);
 *
 * DESCRIPTION
 *
 *    Frees the allocated hash function context.
 *
 ***/
void silc_hash_free(SilcHash hash);

/****f* silccrypt/SilcHashAPI/silc_hash_is_supported
 *
 * SYNOPSIS
 *
 *    bool silc_hash_is_supported(const unsigned char *name);
 *
 * DESCRIPTION
 *
 *    Returns TRUE if the hash function indicated by the `name' exists.
 *
 ***/
bool silc_hash_is_supported(const unsigned char *name);

/****f* silccrypt/SilcHashAPI/silc_hash_get_supported
 *
 * SYNOPSIS
 *
 *    char *silc_hash_get_supported(void);
 *
 * DESCRIPTION
 *
 *    Returns comma (`,') separated list of registered hash functions  This
 *    is used for example when sending supported hash function list during
 *    the SILC Key Exchange protocol (SKE).  The caller must free the returned
 *    pointer.
 *
 ***/
char *silc_hash_get_supported(void);

/****f* silccrypt/SilcHashAPI/silc_hash_len
 *
 * SYNOPSIS
 *
 *    SilcUInt32 silc_hash_len(SilcHash hash);
 *
 * DESCRIPTION
 *
 *    Returns the length of the message digest the hash function produce.
 *
 ***/
SilcUInt32 silc_hash_len(SilcHash hash);

/****f* silccrypt/SilcHashAPI/silc_hash_block_len
 *
 * SYNOPSIS
 *
 *    SilcUInt32 silc_hash_block_len(SilcHash hash);
 *
 * DESCRIPTION
 *
 *    Returns the block length of the hash function.
 *
 ***/
SilcUInt32 silc_hash_block_len(SilcHash hash);

/****f* silccrypt/SilcHashAPI/silc_hash_get_name
 *
 * SYNOPSIS
 *
 *    const char *silc_hash_get_name(SilcHash hash);
 *
 * DESCRIPTION
 *
 *    Returns the name of the hash function indicated by the `hash' context.
 *
 ***/
const char *silc_hash_get_name(SilcHash hash);

/****f* silccrypt/SilcHashAPI/silc_hash_make
 *
 * SYNOPSIS
 *
 *    void silc_hash_make(SilcHash hash, const unsigned char *data,
 *                        SilcUInt32 len, unsigned char *return_hash);
 *
 * DESCRIPTION
 *
 *    Computes the message digest (hash) out of the data indicated by
 *    `data' of length of `len' bytes.  Returns the message digest to the
 *    `return_hash' buffer which must be at least of the size of the
 *    message digest the `hash' produces.
 *
 ***/
void silc_hash_make(SilcHash hash, const unsigned char *data,
		    SilcUInt32 len, unsigned char *return_hash);

/****f* silccrypt/SilcHashAPI/silc_hash_init
 *
 * SYNOPSIS
 *
 *    void silc_hash_init(SilcHash hash);
 *
 * DESCRIPTION
 *
 *    Sometimes calling the silc_hash_make might not be the most optimal
 *    case of computing digests.  If you have a lot of different data
 *    that you need to put together for computing a digest you may either
 *    put them into a buffer and compute the digest from the buffer by
 *    calling the silc_hash_make, or you can use the silc_hash_init,
 *    silc_hash_update and silc_hash_final to do the digest.  This function
 *    prepares the allocated hash function context for this kind of digest 
 *    computation.  To add the data to be used in the digest computation
 *    call the silc_hash_update function.
 *
 ***/
void silc_hash_init(SilcHash hash);

/****f* silccrypt/SilcHashAPI/silc_hash_update
 *
 * SYNOPSIS
 *
 *    void silc_hash_update(SilcHash hash, const unsigned char *data,
 *                          SilcUInt32 data_len);
 *
 * DESCRIPTION
 *
 *    This function may be called to add data to be used in the digest
 *    computation.  This can be called multiple times to add data from
 *    many sources before actually computing the digest.  Once you've
 *    added all the data you need you can call the silc_hash_final to
 *    actually produce the message digest value.
 *
 * EXAMPLE
 *
 *    unsigned char digest[20];
 *
 *    silc_hash_init(hash);
 *    silc_hash_update(hash, data, data_len);
 *    silc_hash_update(hash, more_data, more_data_len);
 *    silc_hash_final(hash, digest);
 *
 ***/
void silc_hash_update(SilcHash hash, const unsigned char *data,
		      SilcUInt32 data_len);

/****f* silccrypt/SilcHashAPI/silc_hash_final
 *
 * SYNOPSIS
 *
 *    void silc_hash_final(SilcHash hash, unsigned char *return_hash);
 *
 * DESCRIPTION
 *
 *    This function is used to produce the final message digest from
 *    the data that has been added to the hash function context by calling
 *    the silc_hash_update function.  The digest is copied in to the
 *    `return_hash' pointer which must be at least the size that
 *    the silc_hash_len returns.
 *
 ***/
void silc_hash_final(SilcHash hash, unsigned char *return_hash);

/****f* silccrypt/SilcHashAPI/silc_hash_transform
 *
 * SYNOPSIS
 *
 *    void silc_hash_transform(SilcHash hash, SilcUInt32 *state,
 *                             const unsigned char *data);
 *
 * DESCRIPTION
 *
 *    This is special function for calling the hash function's internal
 *    digest generation function.  The size of the `state' array and the
 *    sizeof the `data' buffer is hash function specific and must be
 *    known by the caller.  Usually this function is not needed.
 *
 ***/
void silc_hash_transform(SilcHash hash, SilcUInt32 *state,
			 const unsigned char *data);

/****f* silccrypt/SilcHashAPI/silc_hash_fingerprint
 *
 * SYNOPSIS
 *
 *    char *silc_hash_fingerprint(SilcHash hash, const unsigned char *data,
 *                                SilcUInt32 data_len);
 *
 * DESCRIPTION
 *
 *    Utility function which can be used to create a textual fingerprint
 *    out of the data indicated by `data' of length of `data_len' bytes.
 *    If `hash' is NULL then SHA1 hash function is used automatically.
 *    The caller must free the returned string.
 *
 *    Example output could be:
 *      41BF 5C2E 4149 039A 3917  831F 65C4 0A69 F98B 0A4D
 *
 ***/
char *silc_hash_fingerprint(SilcHash hash, const unsigned char *data,
			    SilcUInt32 data_len);

/****f* silccrypt/SilcHashAPI/silc_hash_babbleprint
 *
 * SYNOPSIS
 *
 *    char *silc_hash_babbleprint(SilcHash hash, const unsigned char *data,
 *                                SilcUInt32 data_len);
 *
 * DESCRIPTION
 *
 *    Utility function which can be used to create a textual babbleprint
 *    out of the data indicated by `data' of length of `data_len' bytes.
 *    If `hash' is NULL then SHA1 hash function is used automatically.
 *    The caller must free the returned string.
 *
 *    The babbleprint is same as fingerprint but encoded in a form which
 *    makes it easier to pronounce.  When verifying fingerprint for example
 *    over a phone call, the babbleprint makes it easier to read the
 *    fingerprint.
 *
 *    Example output could be:
 *      xiber-zulad-vubug-noban-puvyc-labac-zonos-gedik-novem-rudog-tyxix
 *
 ***/
char *silc_hash_babbleprint(SilcHash hash, const unsigned char *data,
			    SilcUInt32 data_len);

#endif
