arc4.c

00001 /*
00002  *  An implementation of the ARCFOUR algorithm
00003  *
00004  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  *
00019  *  This file is part of mbed TLS (https://tls.mbed.org)
00020  */
00021 /*
00022  *  The ARCFOUR algorithm was publicly disclosed on 94/09.
00023  *
00024  *  http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
00025  */
00026 
00027 #if !defined(MBEDTLS_CONFIG_FILE)
00028 #include "mbedtls/config.h"
00029 #else
00030 #include MBEDTLS_CONFIG_FILE
00031 #endif
00032 
00033 #if defined(MBEDTLS_ARC4_C)
00034 
00035 #include "mbedtls/arc4.h"
00036 #include "mbedtls/platform_util.h"
00037 
00038 #include <string.h>
00039 
00040 #if defined(MBEDTLS_SELF_TEST)
00041 #if defined(MBEDTLS_PLATFORM_C)
00042 #include "mbedtls/platform.h"
00043 #else
00044 #include <stdio.h>
00045 #define mbedtls_printf printf
00046 #endif /* MBEDTLS_PLATFORM_C */
00047 #endif /* MBEDTLS_SELF_TEST */
00048 
00049 #if !defined(MBEDTLS_ARC4_ALT)
00050 
00051 void mbedtls_arc4_init( mbedtls_arc4_context *ctx )
00052 {
00053     memset( ctx, 0, sizeof( mbedtls_arc4_context ) );
00054 }
00055 
00056 void mbedtls_arc4_free( mbedtls_arc4_context *ctx )
00057 {
00058     if( ctx == NULL )
00059         return;
00060 
00061     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_arc4_context ) );
00062 }
00063 
00064 /*
00065  * ARC4 key schedule
00066  */
00067 void mbedtls_arc4_setup( mbedtls_arc4_context *ctx, const unsigned char *key,
00068                  unsigned int keylen )
00069 {
00070     int i, j, a;
00071     unsigned int k;
00072     unsigned char *m;
00073 
00074     ctx->x  = 0;
00075     ctx->y  = 0;
00076     m = ctx->m ;
00077 
00078     for( i = 0; i < 256; i++ )
00079         m[i] = (unsigned char) i;
00080 
00081     j = k = 0;
00082 
00083     for( i = 0; i < 256; i++, k++ )
00084     {
00085         if( k >= keylen ) k = 0;
00086 
00087         a = m[i];
00088         j = ( j + a + key[k] ) & 0xFF;
00089         m[i] = m[j];
00090         m[j] = (unsigned char) a;
00091     }
00092 }
00093 
00094 /*
00095  * ARC4 cipher function
00096  */
00097 int mbedtls_arc4_crypt( mbedtls_arc4_context *ctx, size_t length, const unsigned char *input,
00098                 unsigned char *output )
00099 {
00100     int x, y, a, b;
00101     size_t i;
00102     unsigned char *m;
00103 
00104     x = ctx->x ;
00105     y = ctx->y ;
00106     m = ctx->m ;
00107 
00108     for( i = 0; i < length; i++ )
00109     {
00110         x = ( x + 1 ) & 0xFF; a = m[x];
00111         y = ( y + a ) & 0xFF; b = m[y];
00112 
00113         m[x] = (unsigned char) b;
00114         m[y] = (unsigned char) a;
00115 
00116         output[i] = (unsigned char)
00117             ( input[i] ^ m[(unsigned char)( a + b )] );
00118     }
00119 
00120     ctx->x  = x;
00121     ctx->y  = y;
00122 
00123     return( 0 );
00124 }
00125 
00126 #endif /* !MBEDTLS_ARC4_ALT */
00127 
00128 #if defined(MBEDTLS_SELF_TEST)
00129 /*
00130  * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
00131  *
00132  * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
00133  */
00134 static const unsigned char arc4_test_key[3][8] =
00135 {
00136     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
00137     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
00138     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
00139 };
00140 
00141 static const unsigned char arc4_test_pt[3][8] =
00142 {
00143     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
00144     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
00145     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
00146 };
00147 
00148 static const unsigned char arc4_test_ct[3][8] =
00149 {
00150     { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
00151     { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
00152     { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
00153 };
00154 
00155 /*
00156  * Checkup routine
00157  */
00158 int mbedtls_arc4_self_test( int verbose )
00159 {
00160     int i, ret = 0;
00161     unsigned char ibuf[8];
00162     unsigned char obuf[8];
00163     mbedtls_arc4_context ctx;
00164 
00165     mbedtls_arc4_init( &ctx );
00166 
00167     for( i = 0; i < 3; i++ )
00168     {
00169         if( verbose != 0 )
00170             mbedtls_printf( "  ARC4 test #%d: ", i + 1 );
00171 
00172         memcpy( ibuf, arc4_test_pt[i], 8 );
00173 
00174         mbedtls_arc4_setup( &ctx, arc4_test_key[i], 8 );
00175         mbedtls_arc4_crypt( &ctx, 8, ibuf, obuf );
00176 
00177         if( memcmp( obuf, arc4_test_ct[i], 8 ) != 0 )
00178         {
00179             if( verbose != 0 )
00180                 mbedtls_printf( "failed\n" );
00181 
00182             ret = 1;
00183             goto exit;
00184         }
00185 
00186         if( verbose != 0 )
00187             mbedtls_printf( "passed\n" );
00188     }
00189 
00190     if( verbose != 0 )
00191         mbedtls_printf( "\n" );
00192 
00193 exit:
00194     mbedtls_arc4_free( &ctx );
00195 
00196     return( ret );
00197 }
00198 
00199 #endif /* MBEDTLS_SELF_TEST */
00200 
00201 #endif /* MBEDTLS_ARC4_C */