/*

  silchash.c

  Author: Pekka Riikonen <priikone@silcnet.org>

  Copyright (C) 1997 - 2007 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.

*/
/* $Id$ */

#include "silc.h"

#include "md5.h"
#include "sha1.h"
#include "sha256.h"
#include "sha512.h"

/* The main SILC hash structure. */
struct SilcHashStruct {
  SilcHashObject *hash;
  void *context;
};

#ifndef SILC_SYMBIAN
/* List of dynamically registered hash functions. */
SilcDList silc_hash_list = NULL;
#endif /* SILC_SYMBIAN */

/* Default hash functions for silc_hash_register_default(). */
const SilcHashObject silc_default_hash[] =
{
  { "sha256", "2.16.840.1.101.3.4.2.1",
    32, 64, silc_sha256_init, silc_sha256_update, silc_sha256_final,
    silc_sha256_transform, silc_sha256_context_len },
  { "sha512", "2.16.840.1.101.3.4.2.3",
    32, 64, silc_sha512_init, silc_sha512_update, silc_sha512_final,
    silc_sha512_transform, silc_sha512_context_len },
  { "sha1", "1.3.14.3.2.26",
    20, 64, silc_sha1_init, silc_sha1_update, silc_sha1_final,
    silc_sha1_transform, silc_sha1_context_len },
  { "md5", "1.2.840.113549.2.5",
    16, 64, silc_md5_init, silc_md5_update, silc_md5_final,
    silc_md5_transform, silc_md5_context_len },

  { NULL, NULL, 0, 0, NULL, NULL, NULL, NULL, NULL }
};

/* Registers a new hash function */

SilcBool silc_hash_register(const SilcHashObject *hash)
{
#ifndef SILC_SYMBIAN
  SilcHashObject *new;

  SILC_LOG_DEBUG(("Registering new hash function `%s'", hash->name));

  /* Check for existing */
  if (silc_hash_list) {
    SilcHashObject *entry;
    silc_dlist_start(silc_hash_list);
    while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
      if (!strcmp(entry->name, hash->name))
	return FALSE;
    }
  }

  new = silc_calloc(1, sizeof(*new));
  if (!new)
    return FALSE;
  new->name = strdup(hash->name);
  if (!new->name) {
    silc_free(new);
    return FALSE;
  }
  new->oid = strdup(hash->oid);
  if (!new->oid) {
    silc_free(new);
    return FALSE;
  }
  new->hash_len = hash->hash_len;
  new->block_len = hash->block_len;
  new->init = hash->init;
  new->update = hash->update;
  new->final = hash->final;
  new->transform = hash->transform;
  new->context_len = hash->context_len;

  /* Add to list */
  if (silc_hash_list == NULL)
    silc_hash_list = silc_dlist_init();
  silc_dlist_add(silc_hash_list, new);

#endif /* SILC_SYMBIAN */
  return TRUE;
}

/* Unregister a hash function */

SilcBool silc_hash_unregister(SilcHashObject *hash)
{
#ifndef SILC_SYMBIAN
  SilcHashObject *entry;

  SILC_LOG_DEBUG(("Unregistering hash function"));

  if (!silc_hash_list)
    return FALSE;

  silc_dlist_start(silc_hash_list);
  while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
    if (hash == SILC_ALL_HASH_FUNCTIONS || entry == hash) {
      silc_dlist_del(silc_hash_list, entry);
      silc_free(entry->name);
      silc_free(entry->oid);
      silc_free(entry);

      if (silc_dlist_count(silc_hash_list) == 0) {
	silc_dlist_uninit(silc_hash_list);
	silc_hash_list = NULL;
      }

      return TRUE;
    }
  }

#endif /* SILC_SYMBIAN */
  return FALSE;
}

/* Register default hash functions */

SilcBool silc_hash_register_default(void)
{
  /* We use builtin hash functions */
  return TRUE;
}

/* Unregister all hash functions */

SilcBool silc_hash_unregister_all(void)
{
#ifndef SILC_SYMBIAN
  SilcHashObject *entry;

  if (!silc_hash_list)
    return FALSE;

  silc_dlist_start(silc_hash_list);
  while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
    silc_hash_unregister(entry);
    if (!silc_hash_list)
      break;
  }
#endif /* SILC_SYMBIAN */
  return TRUE;
}

/* Allocates a new SilcHash object. New object is returned into new_hash
   argument. */

SilcBool silc_hash_alloc(const char *name, SilcHash *new_hash)
{
  SilcHashObject *entry = NULL;
  int i;

  SILC_LOG_DEBUG(("Allocating new hash %s", name));

#ifndef SILC_SYMBIAN
  /* Check list of registered hash functions */
  if (silc_hash_list) {
    silc_dlist_start(silc_hash_list);
    while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
      if (!strcmp(entry->name, name))
	break;
    }
  }
#endif /* SILC_SYMBIAN */

  if (!entry) {
    /* Check builtin hash function list */
    for (i = 0; silc_default_hash[i].name; i++) {
      if (!strcmp(silc_default_hash[i].name, name)) {
	entry = (SilcHashObject *)&(silc_default_hash[i]);
	break;
      }
    }
  }

  if (entry) {
    *new_hash = silc_calloc(1, sizeof(**new_hash));
    if (!(*new_hash))
      return FALSE;
    (*new_hash)->hash = entry;
    (*new_hash)->context = silc_calloc(1, entry->context_len());
    if (!(*new_hash)->context) {
      silc_free(*new_hash);
      return FALSE;
    }
    return TRUE;
  }

  return FALSE;
}

/* Allocate hash by OID string */

SilcBool silc_hash_alloc_by_oid(const char *oid, SilcHash *new_hash)
{
  SilcHashObject *entry = NULL;
  int i;

  SILC_LOG_DEBUG(("Allocating new hash %s", oid));

#ifndef SILC_SYMBIAN
  /* Check list of registered hash functions */
  if (silc_hash_list) {
    silc_dlist_start(silc_hash_list);
    while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
      if (!strcmp(entry->oid, oid))
	break;
    }
  }
#endif /* SILC_SYMBIAN */

  if (!entry) {
    /* Check builtin hash function list */
    for (i = 0; silc_default_hash[i].oid; i++) {
      if (!strcmp(silc_default_hash[i].oid, oid)) {
	entry = (SilcHashObject *)&(silc_default_hash[i]);
	break;
      }
    }
  }

  if (entry) {
    *new_hash = silc_calloc(1, sizeof(**new_hash));
    if (!(*new_hash))
      return FALSE;
    (*new_hash)->hash = entry;
    (*new_hash)->context = silc_calloc(1, entry->context_len());
    if (!(*new_hash)->context) {
      silc_free(*new_hash);
      return FALSE;
    }
    return TRUE;
  }

  return FALSE;
}

/* Free's the SilcHash object */

void silc_hash_free(SilcHash hash)
{
  if (hash) {
    silc_free(hash->context);
    silc_free(hash);
  }
}

/* Returns the length of the hash digest. */

SilcUInt32 silc_hash_len(SilcHash hash)
{
  return hash->hash->hash_len;
}

/* Returns the block lenght of the hash. */

SilcUInt32 silc_hash_block_len(SilcHash hash)
{
  return hash->hash->block_len;
}

/* Returns the name of the hash function */

const char *silc_hash_get_name(SilcHash hash)
{
  return hash->hash->name;
}

/* Returns hash OID string */

const char *silc_hash_get_oid(SilcHash hash)
{
  return hash->hash->oid;
}

/* Returns TRUE if hash algorithm `name' is supported. */

SilcBool silc_hash_is_supported(const char *name)
{
  SilcHashObject *entry;
  int i;

#ifndef SILC_SYMBIAN
  if (silc_hash_list) {
    silc_dlist_start(silc_hash_list);
    while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
      if (!strcmp(entry->name, name))
	return TRUE;
    }
  }
#endif /* SILC_SYMBIAN */

  for (i = 0; silc_default_hash[i].name; i++)
    if (!strcmp(silc_default_hash[i].name, name))
      return TRUE;

  return FALSE;
}

/* Returns comma separated list of supported hash functions. */

char *silc_hash_get_supported(void)
{
  SilcHashObject *entry, *entry2;
  char *list = NULL;
  int i, len = 0;

#ifndef SILC_SYMBIAN
  if (silc_hash_list) {
    silc_dlist_start(silc_hash_list);
    while ((entry = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
      len += strlen(entry->name);
      list = silc_realloc(list, len + 1);

      memcpy(list + (len - strlen(entry->name)),
	     entry->name, strlen(entry->name));
      memcpy(list + len, ",", 1);
      len++;
    }
  }
#endif /* SILC_SYMBIAN */

  for (i = 0; silc_default_hash[i].name; i++) {
    entry = (SilcHashObject *)&(silc_default_hash[i]);

    if (silc_hash_list) {
      silc_dlist_start(silc_hash_list);
      while ((entry2 = silc_dlist_get(silc_hash_list)) != SILC_LIST_END) {
	if (!strcmp(entry2->name, entry->name))
	  break;
      }
      if (entry2)
	continue;
    }

    len += strlen(entry->name);
    list = silc_realloc(list, len + 1);

    memcpy(list + (len - strlen(entry->name)),
	   entry->name, strlen(entry->name));
    memcpy(list + len, ",", 1);
    len++;
  }

  list[len - 1] = 0;

  return list;
}

/* Creates the hash value and returns it to the return_hash argument. */

void silc_hash_make(SilcHash hash, const unsigned char *data,
		    SilcUInt32 len, unsigned char *return_hash)
{
  silc_hash_init(hash);
  silc_hash_update(hash, data, len);
  silc_hash_final(hash, return_hash);
}

void silc_hash_init(SilcHash hash)
{
  hash->hash->init(hash->context);
}

void silc_hash_update(SilcHash hash, const unsigned char *data,
		      SilcUInt32 data_len)
{
  hash->hash->update(hash->context, (unsigned char *)data, data_len);
}

void silc_hash_final(SilcHash hash, unsigned char *return_hash)
{
  hash->hash->final(hash->context, return_hash);
}

void silc_hash_transform(SilcHash hash, void *state,
			 const unsigned char *data)
{
  hash->hash->transform(state, data);
}

/* Creates fingerprint of the data. If `hash' is NULL SHA1 is used as
   default hash function. The returned fingerprint must be freed by the
   caller. */

char *silc_hash_fingerprint(SilcHash hash, const unsigned char *data,
			    SilcUInt32 data_len)
{
  SilcHash new_hash = NULL;
  unsigned char h[32];
  char *ret;

  if (!hash) {
    if (!silc_hash_alloc("sha1", &new_hash))
      return NULL;
    hash = new_hash;
  }

  silc_hash_make(hash, data, data_len, h);
  ret = silc_fingerprint(h, hash->hash->hash_len);

  if (new_hash != NULL)
    silc_hash_free(new_hash);
  return ret;
}

static const char vo[]= "aeiouy";
static const char co[]= "bcdfghklmnprstvzx";

/* Creates a babbleprint (Bubble Babble Encoding, developed by Antti
   Huima (draft-huima-babble-01.txt)), by first computing real fingerprint
   using `hash' or if NULL, then using SHA1, and then encoding the
   fingerprint to the babbleprint. */

char *silc_hash_babbleprint(SilcHash hash, const unsigned char *data,
			    SilcUInt32 data_len)
{
  SilcHash new_hash = NULL;
  char *babbleprint;
  unsigned char hval[32];
  unsigned int a, b, c, d, e, check;
  int i, k, out_len;

  if (!hash) {
    if (!silc_hash_alloc("sha1", &new_hash))
      return NULL;
    hash = new_hash;
  }

  /* Take fingerprint */
  silc_hash_make(hash, data, data_len, hval);

  /* Encode babbleprint */
  out_len = (((hash->hash->hash_len + 1) / 2) + 1) * 6;
  babbleprint = silc_calloc(out_len, sizeof(*babbleprint));
  if (!babbleprint) {
    silc_hash_free(new_hash);
    return NULL;
  }
  babbleprint[0] = co[16];

  check = 1;
  for (i = 0, k = 1; i < hash->hash->hash_len - 1; i += 2, k += 6) {
    a = (((hval[i] >> 6) & 3) + check) % 6;
    b = (hval[i] >> 2) & 15;
    c = ((hval[i] & 3) + (check / 6)) % 6;
    d = (hval[i + 1] >> 4) & 15;
    e = hval[i + 1] & 15;

    check = ((check * 5) + (hval[i] * 7) + hval[i + 1]) % 36;

    babbleprint[k + 0] = vo[a];
    babbleprint[k + 1] = co[b];
    babbleprint[k + 2] = vo[c];
    babbleprint[k + 3] = co[d];
    babbleprint[k + 4] = '-';
    babbleprint[k + 5] = co[e];
  }

  if ((hash->hash->hash_len % 2) != 0) {
    a = (((hval[i] >> 6) & 3) + check) % 6;
    b = (hval[i] >> 2) & 15;
    c = ((hval[i] & 3) + (check / 6)) % 6;
    babbleprint[k + 0] = vo[a];
    babbleprint[k + 1] = co[b];
    babbleprint[k + 2] = vo[c];
  } else {
    a = check % 6;
    b = 16;
    c = check / 6;
    babbleprint[k + 0] = vo[a];
    babbleprint[k + 1] = co[b];
    babbleprint[k + 2] = vo[c];
  }
  babbleprint[k + 3] = co[16];

  if (new_hash != NULL)
    silc_hash_free(new_hash);
  return babbleprint;
}