/*

 * purple

 *

 * Purple is the legal property of its developers, whose names are too numerous

 * to list here.  Please refer to the COPYRIGHT file distributed with this

 * source distribution.

 *

 * 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; either version 2 of the License, or

 * (at your option) any later version.

 *

 * 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.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA

 */

#include <cipher.h>

#include <util.h>

struct RC4Context {

  guchar state[256];

  guchar x;

  guchar y;

  gint key_len;

};

static void

rc4_init(PurpleCipherContext *context, void *extra) {

  struct RC4Context *rc4_ctx;

  rc4_ctx = g_new0(struct RC4Context, 1);

  purple_cipher_context_set_data(context, rc4_ctx);

  purple_cipher_context_reset(context, extra);

}

static void

rc4_reset(PurpleCipherContext *context, void *extra) {

  struct RC4Context *rc4_ctx;

  guint i;

  rc4_ctx = purple_cipher_context_get_data(context);

  g_return_if_fail(rc4_ctx);

  for(i = 0; i < 256; i++)

    rc4_ctx->state[i] = i;

  rc4_ctx->x = 0;

  rc4_ctx->y = 0;

  /* default is 5 bytes (40bit key) */

  rc4_ctx->key_len = 5;

}

static void

rc4_uninit(PurpleCipherContext *context) {

  struct RC4Context *rc4_ctx;

  rc4_ctx = purple_cipher_context_get_data(context);

  memset(rc4_ctx, 0, sizeof(*rc4_ctx));

  g_free(rc4_ctx);

  rc4_ctx = NULL;

}

static void

rc4_set_key (PurpleCipherContext *context, const guchar * key) {

  struct RC4Context *ctx;

  guchar *state;

  guchar temp_swap;

  guchar x, y;

  guint i;

  ctx = purple_cipher_context_get_data(context);

  x = 0;

  y = 0;

  state = &ctx->state[0];

  for(i = 0; i < 256; i++)

  {

    y = (key[x] + state[i] + y) % 256;

    temp_swap = state[i];

    state[i] = state[y];

    state[y] = temp_swap;

    x = (x + 1) % ctx->key_len;

  }

}

static void

rc4_set_opt(PurpleCipherContext *context, const gchar *name, void *value) {

  struct RC4Context *ctx;

  ctx = purple_cipher_context_get_data(context);

  if(purple_strequal(name, "key_len")) {

    ctx->key_len = GPOINTER_TO_INT(value);

  }

}

static size_t

rc4_get_key_size (PurpleCipherContext *context)

{

  struct RC4Context *ctx;

  g_return_val_if_fail(context, -1);

  ctx = purple_cipher_context_get_data(context);

  g_return_val_if_fail(ctx, -1);

  return ctx->key_len;

}

static void *

rc4_get_opt(PurpleCipherContext *context, const gchar *name) {

  struct RC4Context *ctx;

  ctx = purple_cipher_context_get_data(context);

  if(purple_strequal(name, "key_len")) {

    return GINT_TO_POINTER(ctx->key_len);

  }

  return NULL;

}

static gint

rc4_encrypt(PurpleCipherContext *context, const guchar data[],

            size_t len, guchar output[], size_t *outlen) {

  struct RC4Context *ctx;

  guchar temp_swap;

  guchar x, y, z;

  guchar *state;

  guint i;

  ctx = purple_cipher_context_get_data(context);

  x = ctx->x;

  y = ctx->y;

  state = &ctx->state[0];

  for(i = 0; i < len; i++)

  {

    x = (x + 1) % 256;

    y = (state[x] + y) % 256;

    temp_swap = state[x];

    state[x] = state[y];

    state[y] = temp_swap;

    z = state[x] + (state[y]) % 256;

    output[i] = data[i] ^ state[z];

  }

  ctx->x = x;

  ctx->y = y;

  if(outlen)

    *outlen = len;

  return 0;

}

static PurpleCipherOps RC4Ops = {

  rc4_set_opt,   /* Set Option    */

  rc4_get_opt,   /* Get Option    */

  rc4_init,      /* init          */

  rc4_reset,     /* reset         */

  rc4_uninit,    /* uninit        */

  NULL,          /* set iv        */

  NULL,          /* append        */

  NULL,          /* digest        */

  rc4_encrypt,   /* encrypt       */

  NULL,          /* decrypt       */

  NULL,          /* set salt      */

  NULL,          /* get salt size */

  rc4_set_key,   /* set key       */

  rc4_get_key_size, /* get key size  */

  NULL,          /* set batch mode */

  NULL,          /* get batch mode */

  NULL,          /* get block size */

  NULL           /* set key with len */

};

PurpleCipherOps *

purple_rc4_cipher_get_ops(void) {

  return &RC4Ops;

}