common/mbedtls/arc4.c

   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
  45 void mbedtls_arc4_init(mbedtls_arc4_context *ctx) {
  46     memset(ctx, 0, sizeof(mbedtls_arc4_context));
  47 }
  48
  49 void mbedtls_arc4_free(mbedtls_arc4_context *ctx) {
  50     if (ctx == NULL)
  51         return;
  52
  53     mbedtls_platform_zeroize(ctx, sizeof(mbedtls_arc4_context));
  54 }
  55
  56 /*
  57  * ARC4 key schedule
  58  */
  59 void mbedtls_arc4_setup(mbedtls_arc4_context *ctx, const unsigned char *key,
  60                         unsigned int keylen) {
  61     int i, j, a;
  62     unsigned int k;
  63     unsigned char *m;
  64
  65     ctx->x = 0;
  66     ctx->y = 0;
  67     m = ctx->m;
  68
  69     for (i = 0; i < 256; i++)
  70         m[i] = (unsigned char) i;
  71
  72     j = k = 0;
  73
  74     for (i = 0; i < 256; i++, k++) {
  75         if (k >= keylen) k = 0;
  76
  77         a = m[i];
  78         j = (j + a + key[k]) & 0xFF;
  79         m[i] = m[j];
  80         m[j] = (unsigned char) a;
  81     }
  82 }
  83
  84 /*
  85  * ARC4 cipher function
  86  */
  87 int mbedtls_arc4_crypt(mbedtls_arc4_context *ctx, size_t length, const unsigned char *input,
  88                        unsigned char *output) {
  89     int x, y, a, b;
  90     size_t i;
  91     unsigned char *m;
  92
  93     x = ctx->x;
  94     y = ctx->y;
  95     m = ctx->m;
  96
  97     for (i = 0; i < length; i++) {
  98         x = (x + 1) & 0xFF;
  99         a = m[x];
 100         y = (y + a) & 0xFF;
 101         b = m[y];
 102
 103         m[x] = (unsigned char) b;
 104         m[y] = (unsigned char) a;
 105
 106         output[i] = (unsigned char)
 107                     (input[i] ^ m[(unsigned char)(a + b)]);
 108     }
 109
 110     ctx->x = x;
 111     ctx->y = y;
 112
 113     return (0);
 114 }
 115
 116 #endif /* !MBEDTLS_ARC4_ALT */
 117
 118 #if defined(MBEDTLS_SELF_TEST)
 119 /*
 120  * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
 121  *
 122  * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
 123  */
 124 static const unsigned char arc4_test_key[3][8] = {
 125     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 126     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 127     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
 128 };
 129
 130 static const unsigned char arc4_test_pt[3][8] = {
 131     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 132     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
 133     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
 134 };
 135
 136 static const unsigned char arc4_test_ct[3][8] = {
 137     { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
 138     { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
 139     { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
 140 };
 141
 142 /*
 143  * Checkup routine
 144  */
 145 int mbedtls_arc4_self_test(int verbose) {
 146     int i, ret = 0;
 147     unsigned char ibuf[8];
 148     unsigned char obuf[8];
 149     mbedtls_arc4_context ctx;
 150
 151     mbedtls_arc4_init(&ctx);
 152
 153     for (i = 0; i < 3; i++) {
 154         if (verbose != 0)
 155             mbedtls_printf("  ARC4 test #%d: ", i + 1);
 156
 157         memcpy(ibuf, arc4_test_pt[i], 8);
 158
 159         mbedtls_arc4_setup(&ctx, arc4_test_key[i], 8);
 160         mbedtls_arc4_crypt(&ctx, 8, ibuf, obuf);
 161
 162         if (memcmp(obuf, arc4_test_ct[i], 8) != 0) {
 163             if (verbose != 0)
 164                 mbedtls_printf("failed\n");
 165
 166             ret = 1;
 167             goto exit;
 168         }
 169
 170         if (verbose != 0)
 171             mbedtls_printf("passed\n");
 172     }
 173
 174     if (verbose != 0)
 175         mbedtls_printf("\n");
 176
 177 exit:
 178     mbedtls_arc4_free(&ctx);
 179
 180     return (ret);
 181 }
 182
 183 #endif /* MBEDTLS_SELF_TEST */
 184
 185 #endif /* MBEDTLS_ARC4_C */