1 /*
2 * An implementation of the ARCFOUR algorithm
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19 /*
20 * The ARCFOUR algorithm was publicly disclosed on 94/09.
21 *
22 * http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
23 */
24
25 #include "common.h"
26
27 #if defined(MBEDTLS_ARC4_C)
28
29 #include "mbedtls/arc4.h"
30 #include "mbedtls/platform_util.h"
31
32 #include <string.h>
33
34 #if defined(MBEDTLS_SELF_TEST)
35 #if defined(MBEDTLS_PLATFORM_C)
36 #include "mbedtls/platform.h"
37 #else
38 #include <stdio.h>
39 #define mbedtls_printf printf
40 #endif /* MBEDTLS_PLATFORM_C */
41 #endif /* MBEDTLS_SELF_TEST */
42
43 #if !defined(MBEDTLS_ARC4_ALT)
44
mbedtls_arc4_init(mbedtls_arc4_context * ctx)45 void mbedtls_arc4_init( mbedtls_arc4_context *ctx )
46 {
47 memset( ctx, 0, sizeof( mbedtls_arc4_context ) );
48 }
49
mbedtls_arc4_free(mbedtls_arc4_context * ctx)50 void mbedtls_arc4_free( mbedtls_arc4_context *ctx )
51 {
52 if( ctx == NULL )
53 return;
54
55 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_arc4_context ) );
56 }
57
58 /*
59 * ARC4 key schedule
60 */
mbedtls_arc4_setup(mbedtls_arc4_context * ctx,const unsigned char * key,unsigned int keylen)61 void mbedtls_arc4_setup( mbedtls_arc4_context *ctx, const unsigned char *key,
62 unsigned int keylen )
63 {
64 int i, j, a;
65 unsigned int k;
66 unsigned char *m;
67
68 ctx->x = 0;
69 ctx->y = 0;
70 m = ctx->m;
71
72 for( i = 0; i < 256; i++ )
73 m[i] = (unsigned char) i;
74
75 j = k = 0;
76
77 for( i = 0; i < 256; i++, k++ )
78 {
79 if( k >= keylen ) k = 0;
80
81 a = m[i];
82 j = ( j + a + key[k] ) & 0xFF;
83 m[i] = m[j];
84 m[j] = (unsigned char) a;
85 }
86 }
87
88 /*
89 * ARC4 cipher function
90 */
mbedtls_arc4_crypt(mbedtls_arc4_context * ctx,size_t length,const unsigned char * input,unsigned char * output)91 int mbedtls_arc4_crypt( mbedtls_arc4_context *ctx, size_t length, const unsigned char *input,
92 unsigned char *output )
93 {
94 int x, y, a, b;
95 size_t i;
96 unsigned char *m;
97
98 x = ctx->x;
99 y = ctx->y;
100 m = ctx->m;
101
102 for( i = 0; i < length; i++ )
103 {
104 x = ( x + 1 ) & 0xFF; a = m[x];
105 y = ( y + a ) & 0xFF; b = m[y];
106
107 m[x] = (unsigned char) b;
108 m[y] = (unsigned char) a;
109
110 output[i] = (unsigned char)
111 ( input[i] ^ m[(unsigned char)( a + b )] );
112 }
113
114 ctx->x = x;
115 ctx->y = y;
116
117 return( 0 );
118 }
119
120 #endif /* !MBEDTLS_ARC4_ALT */
121
122 #if defined(MBEDTLS_SELF_TEST)
123 /*
124 * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
125 *
126 * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
127 */
128 static const unsigned char arc4_test_key[3][8] =
129 {
130 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
131 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
132 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
133 };
134
135 static const unsigned char arc4_test_pt[3][8] =
136 {
137 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
138 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
139 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
140 };
141
142 static const unsigned char arc4_test_ct[3][8] =
143 {
144 { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
145 { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
146 { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
147 };
148
149 /*
150 * Checkup routine
151 */
mbedtls_arc4_self_test(int verbose)152 int mbedtls_arc4_self_test( int verbose )
153 {
154 int i, ret = 0;
155 unsigned char ibuf[8];
156 unsigned char obuf[8];
157 mbedtls_arc4_context ctx;
158
159 mbedtls_arc4_init( &ctx );
160
161 for( i = 0; i < 3; i++ )
162 {
163 if( verbose != 0 )
164 mbedtls_printf( " ARC4 test #%d: ", i + 1 );
165
166 memcpy( ibuf, arc4_test_pt[i], 8 );
167
168 mbedtls_arc4_setup( &ctx, arc4_test_key[i], 8 );
169 mbedtls_arc4_crypt( &ctx, 8, ibuf, obuf );
170
171 if( memcmp( obuf, arc4_test_ct[i], 8 ) != 0 )
172 {
173 if( verbose != 0 )
174 mbedtls_printf( "failed\n" );
175
176 ret = 1;
177 goto exit;
178 }
179
180 if( verbose != 0 )
181 mbedtls_printf( "passed\n" );
182 }
183
184 if( verbose != 0 )
185 mbedtls_printf( "\n" );
186
187 exit:
188 mbedtls_arc4_free( &ctx );
189
190 return( ret );
191 }
192
193 #endif /* MBEDTLS_SELF_TEST */
194
195 #endif /* MBEDTLS_ARC4_C */
196