lib/crypto/arcfour.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    An implementation of the arcfour algorithm
   5
   6    Copyright (C) Andrew Tridgell 1998
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "replace.h"
  23 #include "../lib/crypto/arcfour.h"
  24
  25 /* initialise the arcfour sbox with key */
  26 _PUBLIC_ void arcfour_init(struct arcfour_state *state, const DATA_BLOB *key)
  27 {
  28         size_t ind;
  29         uint8_t j = 0;
  30         for (ind = 0; ind < sizeof(state->sbox); ind++) {
  31                 state->sbox[ind] = (uint8_t)ind;
  32         }
  33
  34         for (ind = 0; ind < sizeof(state->sbox); ind++) {
  35                 uint8_t tc;
  36
  37                 j += (state->sbox[ind] + key->data[ind%key->length]);
  38
  39                 tc = state->sbox[ind];
  40                 state->sbox[ind] = state->sbox[j];
  41                 state->sbox[j] = tc;
  42         }
  43         state->index_i = 0;
  44         state->index_j = 0;
  45 }
  46
  47 /* crypt the data with arcfour */
  48 _PUBLIC_ void arcfour_crypt_sbox(struct arcfour_state *state, uint8_t *data,
  49                                  int len)
  50 {
  51         int ind;
  52
  53         for (ind = 0; ind < len; ind++) {
  54                 uint8_t tc;
  55                 uint8_t t;
  56
  57                 state->index_i++;
  58                 state->index_j += state->sbox[state->index_i];
  59
  60                 tc = state->sbox[state->index_i];
  61                 state->sbox[state->index_i] = state->sbox[state->index_j];
  62                 state->sbox[state->index_j] = tc;
  63
  64                 t = state->sbox[state->index_i] + state->sbox[state->index_j];
  65                 data[ind] = data[ind] ^ state->sbox[t];
  66         }
  67 }
  68
  69 /*
  70   arcfour encryption with a blob key
  71 */
  72 _PUBLIC_ void arcfour_crypt_blob(uint8_t *data, int len, const DATA_BLOB *key)
  73 {
  74         struct arcfour_state state;
  75         arcfour_init(&state, key);
  76         arcfour_crypt_sbox(&state, data, len);
  77 }
  78
  79 /*
  80   a variant that assumes a 16 byte key. This should be removed
  81   when the last user is gone
  82 */
  83 _PUBLIC_ void arcfour_crypt(uint8_t *data, const uint8_t keystr[16], int len)
  84 {
  85         uint8_t keycopy[16];
  86         DATA_BLOB key = { .data = keycopy, .length = sizeof(keycopy) };
  87
  88         memcpy(keycopy, keystr, sizeof(keycopy));
  89
  90         arcfour_crypt_blob(data, len, &key);
  91 }
  92
  93