lgl/arctwo.c

   1 /* arctwo.c --- The RC2 cipher as described in RFC 2268.
   2  * Copyright (C) 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   3  *
   4  * This file is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License as published
   6  * by the Free Software Foundation; either version 2.1, or (at your
   7  * option) any later version.
   8  *
   9  * This file is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this file; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  */
  19
  20 /* Code from GnuTLS/Libgcrypt adapted for gnulib by Simon Josefsson. */
  21
  22 /* This implementation was written by Nikos Mavroyanopoulos for GNUTLS
  23  * as a Libgcrypt module (gnutls/lib/x509/rc2.c) and later adapted for
  24  * direct use by Libgcrypt by Werner Koch.  This implementation is
  25  * only useful for pkcs#12 decryption.
  26  *
  27  * The implementation here is based on Peter Gutmann's RRC.2 paper.
  28  */
  29
  30 #include <config.h>
  31
  32 #include "arctwo.h"
  33
  34 static const uint8_t arctwo_sbox[] = {
  35   217, 120, 249, 196, 25, 221, 181, 237,
  36   40, 233, 253, 121, 74, 160, 216, 157,
  37   198, 126, 55, 131, 43, 118, 83, 142,
  38   98, 76, 100, 136, 68, 139, 251, 162,
  39   23, 154, 89, 245, 135, 179, 79, 19,
  40   97, 69, 109, 141, 9, 129, 125, 50,
  41   189, 143, 64, 235, 134, 183, 123, 11,
  42   240, 149, 33, 34, 92, 107, 78, 130,
  43   84, 214, 101, 147, 206, 96, 178, 28,
  44   115, 86, 192, 20, 167, 140, 241, 220,
  45   18, 117, 202, 31, 59, 190, 228, 209,
  46   66, 61, 212, 48, 163, 60, 182, 38,
  47   111, 191, 14, 218, 70, 105, 7, 87,
  48   39, 242, 29, 155, 188, 148, 67, 3,
  49   248, 17, 199, 246, 144, 239, 62, 231,
  50   6, 195, 213, 47, 200, 102, 30, 215,
  51   8, 232, 234, 222, 128, 82, 238, 247,
  52   132, 170, 114, 172, 53, 77, 106, 42,
  53   150, 26, 210, 113, 90, 21, 73, 116,
  54   75, 159, 208, 94, 4, 24, 164, 236,
  55   194, 224, 65, 110, 15, 81, 203, 204,
  56   36, 145, 175, 80, 161, 244, 112, 57,
  57   153, 124, 58, 133, 35, 184, 180, 122,
  58   252, 2, 54, 91, 37, 85, 151, 49,
  59   45, 93, 250, 152, 227, 138, 146, 174,
  60   5, 223, 41, 16, 103, 108, 186, 201,
  61   211, 0, 230, 207, 225, 158, 168, 44,
  62   99, 22, 1, 63, 88, 226, 137, 169,
  63   13, 56, 52, 27, 171, 51, 255, 176,
  64   187, 72, 12, 95, 185, 177, 205, 46,
  65   197, 243, 219, 71, 229, 165, 156, 119,
  66   10, 166, 32, 104, 254, 127, 193, 173
  67 };
  68
  69 #define rotl16(x,n)   (((x) << ((uint16_t)(n))) | ((x) >> (16 - (uint16_t)(n))))
  70 #define rotr16(x,n)   (((x) >> ((uint16_t)(n))) | ((x) << (16 - (uint16_t)(n))))
  71
  72 /* C89 compliant way to cast 'char' to 'unsigned char'. */
  73 static inline unsigned char
  74 to_uchar (char ch)
  75 {
  76   return ch;
  77 }
  78
  79 void
  80 arctwo_encrypt (arctwo_context *context, const char *inbuf,
  81                 char *outbuf, size_t length)
  82 {
  83   for (; length >= ARCTWO_BLOCK_SIZE; length -= ARCTWO_BLOCK_SIZE,
  84          inbuf += ARCTWO_BLOCK_SIZE, outbuf += ARCTWO_BLOCK_SIZE)
  85     {
  86       size_t i, j;
  87       uint16_t word0 = 0, word1 = 0, word2 = 0, word3 = 0;
  88
  89       word0 = (word0 << 8) | to_uchar (inbuf[1]);
  90       word0 = (word0 << 8) | to_uchar (inbuf[0]);
  91       word1 = (word1 << 8) | to_uchar (inbuf[3]);
  92       word1 = (word1 << 8) | to_uchar (inbuf[2]);
  93       word2 = (word2 << 8) | to_uchar (inbuf[5]);
  94       word2 = (word2 << 8) | to_uchar (inbuf[4]);
  95       word3 = (word3 << 8) | to_uchar (inbuf[7]);
  96       word3 = (word3 << 8) | to_uchar (inbuf[6]);
  97
  98       for (i = 0; i < 16; i++)
  99         {
 100           j = i * 4;
 101           /* For some reason I cannot combine those steps. */
 102           word0 += (word1 & ~word3) + (word2 & word3) + context->S[j];
 103           word0 = rotl16 (word0, 1);
 104
 105           word1 += (word2 & ~word0) + (word3 & word0) + context->S[j + 1];
 106           word1 = rotl16 (word1, 2);
 107
 108           word2 += (word3 & ~word1) + (word0 & word1) + context->S[j + 2];
 109           word2 = rotl16 (word2, 3);
 110
 111           word3 += (word0 & ~word2) + (word1 & word2) + context->S[j + 3];
 112           word3 = rotl16 (word3, 5);
 113
 114           if (i == 4 || i == 10)
 115             {
 116               word0 += context->S[word3 & 63];
 117               word1 += context->S[word0 & 63];
 118               word2 += context->S[word1 & 63];
 119               word3 += context->S[word2 & 63];
 120             }
 121         }
 122
 123       outbuf[0] = word0 & 255;
 124       outbuf[1] = word0 >> 8;
 125       outbuf[2] = word1 & 255;
 126       outbuf[3] = word1 >> 8;
 127       outbuf[4] = word2 & 255;
 128       outbuf[5] = word2 >> 8;
 129       outbuf[6] = word3 & 255;
 130       outbuf[7] = word3 >> 8;
 131     }
 132 }
 133
 134 void
 135 arctwo_decrypt (arctwo_context *context, const char *inbuf,
 136                 char *outbuf, size_t length)
 137 {
 138   for (; length >= ARCTWO_BLOCK_SIZE; length -= ARCTWO_BLOCK_SIZE,
 139          inbuf += ARCTWO_BLOCK_SIZE, outbuf += ARCTWO_BLOCK_SIZE)
 140     {
 141       size_t i, j;
 142       uint16_t word0 = 0, word1 = 0, word2 = 0, word3 = 0;
 143
 144       word0 = (word0 << 8) | to_uchar (inbuf[1]);
 145       word0 = (word0 << 8) | to_uchar (inbuf[0]);
 146       word1 = (word1 << 8) | to_uchar (inbuf[3]);
 147       word1 = (word1 << 8) | to_uchar (inbuf[2]);
 148       word2 = (word2 << 8) | to_uchar (inbuf[5]);
 149       word2 = (word2 << 8) | to_uchar (inbuf[4]);
 150       word3 = (word3 << 8) | to_uchar (inbuf[7]);
 151       word3 = (word3 << 8) | to_uchar (inbuf[6]);
 152
 153       for (i = 16; i > 0; i--)
 154         {
 155           j = (i - 1) * 4;
 156
 157           word3 = rotr16 (word3, 5);
 158           word3 -= (word0 & ~word2) + (word1 & word2) + context->S[j + 3];
 159
 160           word2 = rotr16 (word2, 3);
 161           word2 -= (word3 & ~word1) + (word0 & word1) + context->S[j + 2];
 162
 163           word1 = rotr16 (word1, 2);
 164           word1 -= (word2 & ~word0) + (word3 & word0) + context->S[j + 1];
 165
 166           word0 = rotr16 (word0, 1);
 167           word0 -= (word1 & ~word3) + (word2 & word3) + context->S[j];
 168
 169           if (i == 6 || i == 12)
 170             {
 171               word3 = word3 - context->S[word2 & 63];
 172               word2 = word2 - context->S[word1 & 63];
 173           word1 = word1 - context->S[word0 & 63];
 174           word0 = word0 - context->S[word3 & 63];
 175             }
 176         }
 177
 178       outbuf[0] = word0 & 255;
 179       outbuf[1] = word0 >> 8;
 180       outbuf[2] = word1 & 255;
 181       outbuf[3] = word1 >> 8;
 182       outbuf[4] = word2 & 255;
 183       outbuf[5] = word2 >> 8;
 184       outbuf[6] = word3 & 255;
 185       outbuf[7] = word3 >> 8;
 186     }
 187 }
 188
 189 void
 190 arctwo_setkey_ekb (arctwo_context *context,
 191                    size_t keylen, const char *key, size_t effective_keylen)
 192 {
 193   size_t i;
 194   uint8_t *S, x;
 195
 196   if (keylen < 40 / 8 || effective_keylen > 1024)
 197     return;
 198
 199   S = (uint8_t *) context->S;
 200
 201   for (i = 0; i < keylen; i++)
 202     S[i] = (uint8_t) key[i];
 203
 204   for (i = keylen; i < 128; i++)
 205     S[i] = arctwo_sbox[(S[i - keylen] + S[i - 1]) & 255];
 206
 207   S[0] = arctwo_sbox[S[0]];
 208
 209   /* Phase 2 - reduce effective key size to "bits". This was not
 210    * discussed in Gutmann's paper. I've copied that from the public
 211    * domain code posted in sci.crypt. */
 212   if (effective_keylen)
 213     {
 214       size_t len = (effective_keylen + 7) >> 3;
 215       i = 128 - len;
 216       x = arctwo_sbox[S[i] & (255 >> (7 & -effective_keylen))];
 217       S[i] = x;
 218
 219       while (i--)
 220         {
 221           x = arctwo_sbox[x ^ S[i + len]];
 222           S[i] = x;
 223         }
 224     }
 225
 226   /* Make the expanded key, endian independent. */
 227   for (i = 0; i < 64; i++)
 228     context->S[i] = ((uint16_t) S[i * 2] | (((uint16_t) S[i * 2 + 1]) << 8));
 229 }