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/* arctwo.c --- The RC2 cipher as described in RFC 2268.
* Copyright (C) 2003-2006, 2008-2021 Free Software Foundation, Inc.
*
* This file is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This file 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/* Code from GnuTLS/Libgcrypt adapted for gnulib by Simon Josefsson. */
/* This implementation was written by Nikos Mavroyanopoulos for GNUTLS
* as a Libgcrypt module (gnutls/lib/x509/rc2.c) and later adapted for
* direct use by Libgcrypt by Werner Koch. This implementation is
* only useful for pkcs#12 decryption.
*
* The implementation here is based on Peter Gutmann's RRC.2 paper.
*/
#include <config.h>
#include "arctwo.h"
#include "bitrotate.h"
static const uint8_t arctwo_sbox[] = {
217, 120, 249, 196, 25, 221, 181, 237,
40, 233, 253, 121, 74, 160, 216, 157,
198, 126, 55, 131, 43, 118, 83, 142,
98, 76, 100, 136, 68, 139, 251, 162,
23, 154, 89, 245, 135, 179, 79, 19,
97, 69, 109, 141, 9, 129, 125, 50,
189, 143, 64, 235, 134, 183, 123, 11,
240, 149, 33, 34, 92, 107, 78, 130,
84, 214, 101, 147, 206, 96, 178, 28,
115, 86, 192, 20, 167, 140, 241, 220,
18, 117, 202, 31, 59, 190, 228, 209,
66, 61, 212, 48, 163, 60, 182, 38,
111, 191, 14, 218, 70, 105, 7, 87,
39, 242, 29, 155, 188, 148, 67, 3,
248, 17, 199, 246, 144, 239, 62, 231,
6, 195, 213, 47, 200, 102, 30, 215,
8, 232, 234, 222, 128, 82, 238, 247,
132, 170, 114, 172, 53, 77, 106, 42,
150, 26, 210, 113, 90, 21, 73, 116,
75, 159, 208, 94, 4, 24, 164, 236,
194, 224, 65, 110, 15, 81, 203, 204,
36, 145, 175, 80, 161, 244, 112, 57,
153, 124, 58, 133, 35, 184, 180, 122,
252, 2, 54, 91, 37, 85, 151, 49,
45, 93, 250, 152, 227, 138, 146, 174,
5, 223, 41, 16, 103, 108, 186, 201,
211, 0, 230, 207, 225, 158, 168, 44,
99, 22, 1, 63, 88, 226, 137, 169,
13, 56, 52, 27, 171, 51, 255, 176,
187, 72, 12, 95, 185, 177, 205, 46,
197, 243, 219, 71, 229, 165, 156, 119,
10, 166, 32, 104, 254, 127, 193, 173
};
/* C89 compliant way to cast 'char' to 'unsigned char'. */
static unsigned char
to_uchar (char ch)
{
return ch;
}
void
arctwo_encrypt (arctwo_context *context, const char *inbuf,
char *outbuf, size_t length)
{
for (; length >= ARCTWO_BLOCK_SIZE; length -= ARCTWO_BLOCK_SIZE,
inbuf += ARCTWO_BLOCK_SIZE, outbuf += ARCTWO_BLOCK_SIZE)
{
size_t i, j;
uint16_t word0 = 0, word1 = 0, word2 = 0, word3 = 0;
word0 = (word0 << 8) | to_uchar (inbuf[1]);
word0 = (word0 << 8) | to_uchar (inbuf[0]);
word1 = (word1 << 8) | to_uchar (inbuf[3]);
word1 = (word1 << 8) | to_uchar (inbuf[2]);
word2 = (word2 << 8) | to_uchar (inbuf[5]);
word2 = (word2 << 8) | to_uchar (inbuf[4]);
word3 = (word3 << 8) | to_uchar (inbuf[7]);
word3 = (word3 << 8) | to_uchar (inbuf[6]);
for (i = 0; i < 16; i++)
{
j = i * 4;
/* For some reason I cannot combine those steps. */
word0 += (word1 & ~word3) + (word2 & word3) + context->S[j];
word0 = rotl16 (word0, 1);
word1 += (word2 & ~word0) + (word3 & word0) + context->S[j + 1];
word1 = rotl16 (word1, 2);
word2 += (word3 & ~word1) + (word0 & word1) + context->S[j + 2];
word2 = rotl16 (word2, 3);
word3 += (word0 & ~word2) + (word1 & word2) + context->S[j + 3];
word3 = rotl16 (word3, 5);
if (i == 4 || i == 10)
{
word0 += context->S[word3 & 63];
word1 += context->S[word0 & 63];
word2 += context->S[word1 & 63];
word3 += context->S[word2 & 63];
}
}
outbuf[0] = word0 & 255;
outbuf[1] = word0 >> 8;
outbuf[2] = word1 & 255;
outbuf[3] = word1 >> 8;
outbuf[4] = word2 & 255;
outbuf[5] = word2 >> 8;
outbuf[6] = word3 & 255;
outbuf[7] = word3 >> 8;
}
}
void
arctwo_decrypt (arctwo_context *context, const char *inbuf,
char *outbuf, size_t length)
{
for (; length >= ARCTWO_BLOCK_SIZE; length -= ARCTWO_BLOCK_SIZE,
inbuf += ARCTWO_BLOCK_SIZE, outbuf += ARCTWO_BLOCK_SIZE)
{
size_t i, j;
uint16_t word0 = 0, word1 = 0, word2 = 0, word3 = 0;
word0 = (word0 << 8) | to_uchar (inbuf[1]);
word0 = (word0 << 8) | to_uchar (inbuf[0]);
word1 = (word1 << 8) | to_uchar (inbuf[3]);
word1 = (word1 << 8) | to_uchar (inbuf[2]);
word2 = (word2 << 8) | to_uchar (inbuf[5]);
word2 = (word2 << 8) | to_uchar (inbuf[4]);
word3 = (word3 << 8) | to_uchar (inbuf[7]);
word3 = (word3 << 8) | to_uchar (inbuf[6]);
for (i = 16; i > 0; i--)
{
j = (i - 1) * 4;
word3 = rotr16 (word3, 5);
word3 -= (word0 & ~word2) + (word1 & word2) + context->S[j + 3];
word2 = rotr16 (word2, 3);
word2 -= (word3 & ~word1) + (word0 & word1) + context->S[j + 2];
word1 = rotr16 (word1, 2);
word1 -= (word2 & ~word0) + (word3 & word0) + context->S[j + 1];
word0 = rotr16 (word0, 1);
word0 -= (word1 & ~word3) + (word2 & word3) + context->S[j];
if (i == 6 || i == 12)
{
word3 = word3 - context->S[word2 & 63];
word2 = word2 - context->S[word1 & 63];
word1 = word1 - context->S[word0 & 63];
word0 = word0 - context->S[word3 & 63];
}
}
outbuf[0] = word0 & 255;
outbuf[1] = word0 >> 8;
outbuf[2] = word1 & 255;
outbuf[3] = word1 >> 8;
outbuf[4] = word2 & 255;
outbuf[5] = word2 >> 8;
outbuf[6] = word3 & 255;
outbuf[7] = word3 >> 8;
}
}
void
arctwo_setkey_ekb (arctwo_context *context,
size_t keylen, const char *key, size_t effective_keylen)
{
size_t i;
uint8_t *S, x;
if (keylen < 40 / 8 || effective_keylen > 1024)
return;
S = (uint8_t *) context->S;
for (i = 0; i < keylen; i++)
S[i] = (uint8_t) key[i];
for (i = keylen; i < 128; i++)
S[i] = arctwo_sbox[(S[i - keylen] + S[i - 1]) & 255];
S[0] = arctwo_sbox[S[0]];
/* Phase 2 - reduce effective key size to "bits". This was not
* discussed in Gutmann's paper. I've copied that from the public
* domain code posted in sci.crypt. */
if (effective_keylen)
{
size_t len = (effective_keylen + 7) >> 3;
i = 128 - len;
x = arctwo_sbox[S[i] & (255 >> (7 & -effective_keylen))];
S[i] = x;
while (i--)
{
x = arctwo_sbox[x ^ S[i + len]];
S[i] = x;
}
}
/* Make the expanded key, endian independent. */
for (i = 0; i < 64; i++)
context->S[i] = ((uint16_t) S[i * 2] | (((uint16_t) S[i * 2 + 1]) << 8));
}
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