1 /*
2 * An implementation of the ARCFOUR algorithm
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 */
7 /*
8 * The ARCFOUR algorithm was publicly disclosed on 94/09.
9 *
10 * http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
11 */
12
13 #include "common.h"
14
15 #if defined(MBEDTLS_ARC4_C)
16
17 #include "mbedtls/arc4.h"
18 #include "mbedtls/platform_util.h"
19
20 #include <string.h>
21
22 #include "mbedtls/platform.h"
23
24 #if !defined(MBEDTLS_ARC4_ALT)
25
mbedtls_arc4_init(mbedtls_arc4_context * ctx)26 void mbedtls_arc4_init(mbedtls_arc4_context *ctx)
27 {
28 memset(ctx, 0, sizeof(mbedtls_arc4_context));
29 }
30
mbedtls_arc4_free(mbedtls_arc4_context * ctx)31 void mbedtls_arc4_free(mbedtls_arc4_context *ctx)
32 {
33 if (ctx == NULL) {
34 return;
35 }
36
37 mbedtls_platform_zeroize(ctx, sizeof(mbedtls_arc4_context));
38 }
39
40 /*
41 * ARC4 key schedule
42 */
mbedtls_arc4_setup(mbedtls_arc4_context * ctx,const unsigned char * key,unsigned int keylen)43 void mbedtls_arc4_setup(mbedtls_arc4_context *ctx, const unsigned char *key,
44 unsigned int keylen)
45 {
46 int i, j, a;
47 unsigned int k;
48 unsigned char *m;
49
50 ctx->x = 0;
51 ctx->y = 0;
52 m = ctx->m;
53
54 for (i = 0; i < 256; i++) {
55 m[i] = (unsigned char) i;
56 }
57
58 j = k = 0;
59
60 for (i = 0; i < 256; i++, k++) {
61 if (k >= keylen) {
62 k = 0;
63 }
64
65 a = m[i];
66 j = (j + a + key[k]) & 0xFF;
67 m[i] = m[j];
68 m[j] = (unsigned char) a;
69 }
70 }
71
72 /*
73 * ARC4 cipher function
74 */
mbedtls_arc4_crypt(mbedtls_arc4_context * ctx,size_t length,const unsigned char * input,unsigned char * output)75 int mbedtls_arc4_crypt(mbedtls_arc4_context *ctx, size_t length, const unsigned char *input,
76 unsigned char *output)
77 {
78 int x, y, a, b;
79 size_t i;
80 unsigned char *m;
81
82 x = ctx->x;
83 y = ctx->y;
84 m = ctx->m;
85
86 for (i = 0; i < length; i++) {
87 x = (x + 1) & 0xFF; a = m[x];
88 y = (y + a) & 0xFF; b = m[y];
89
90 m[x] = (unsigned char) b;
91 m[y] = (unsigned char) a;
92
93 output[i] = (unsigned char)
94 (input[i] ^ m[(unsigned char) (a + b)]);
95 }
96
97 ctx->x = x;
98 ctx->y = y;
99
100 return 0;
101 }
102
103 #endif /* !MBEDTLS_ARC4_ALT */
104
105 #if defined(MBEDTLS_SELF_TEST)
106 /*
107 * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
108 *
109 * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
110 */
111 static const unsigned char arc4_test_key[3][8] =
112 {
113 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
114 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
115 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
116 };
117
118 static const unsigned char arc4_test_pt[3][8] =
119 {
120 { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
121 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
122 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
123 };
124
125 static const unsigned char arc4_test_ct[3][8] =
126 {
127 { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
128 { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
129 { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
130 };
131
132 /*
133 * Checkup routine
134 */
mbedtls_arc4_self_test(int verbose)135 int mbedtls_arc4_self_test(int verbose)
136 {
137 int i, ret = 0;
138 unsigned char ibuf[8];
139 unsigned char obuf[8];
140 mbedtls_arc4_context ctx;
141
142 mbedtls_arc4_init(&ctx);
143
144 for (i = 0; i < 3; i++) {
145 if (verbose != 0) {
146 mbedtls_printf(" ARC4 test #%d: ", i + 1);
147 }
148
149 memcpy(ibuf, arc4_test_pt[i], 8);
150
151 mbedtls_arc4_setup(&ctx, arc4_test_key[i], 8);
152 mbedtls_arc4_crypt(&ctx, 8, ibuf, obuf);
153
154 if (memcmp(obuf, arc4_test_ct[i], 8) != 0) {
155 if (verbose != 0) {
156 mbedtls_printf("failed\n");
157 }
158
159 ret = 1;
160 goto exit;
161 }
162
163 if (verbose != 0) {
164 mbedtls_printf("passed\n");
165 }
166 }
167
168 if (verbose != 0) {
169 mbedtls_printf("\n");
170 }
171
172 exit:
173 mbedtls_arc4_free(&ctx);
174
175 return ret;
176 }
177
178 #endif /* MBEDTLS_SELF_TEST */
179
180 #endif /* MBEDTLS_ARC4_C */
181