| 1 | /* |
| 2 | * Copyright (c) 2007, Cameron Rich |
| 3 | * |
| 4 | * All rights reserved. |
| 5 | * |
| 6 | * Redistribution and use in source and binary forms, with or without |
| 7 | * modification, are permitted provided that the following conditions are met: |
| 8 | * |
| 9 | * * Redistributions of source code must retain the above copyright notice, |
| 10 | * this list of conditions and the following disclaimer. |
| 11 | * * Redistributions in binary form must reproduce the above copyright notice, |
| 12 | * this list of conditions and the following disclaimer in the documentation |
| 13 | * and/or other materials provided with the distribution. |
| 14 | * * Neither the name of the axTLS project nor the names of its contributors |
| 15 | * may be used to endorse or promote products derived from this software |
| 16 | * without specific prior written permission. |
| 17 | * |
| 18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 19 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 20 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 21 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
| 22 | * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| 23 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 24 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| 25 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
| 26 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| 27 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| 28 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 29 | */ |
| 30 | |
| 31 | /** |
| 32 | * An implementation of the RC4/ARC4 algorithm. |
| 33 | * Originally written by Christophe Devine. |
| 34 | */ |
| 35 | |
| 36 | #include <string.h> |
| 37 | #include "os_port.h" |
| 38 | #include "crypto.h" |
| 39 | |
| 40 | /** |
| 41 | * Get ready for an encrypt/decrypt operation |
| 42 | */ |
| 43 | void RC4_setup(RC4_CTX *ctx, const uint8_t *key, int length) |
| 44 | { |
| 45 | int i, j = 0, k = 0, a; |
| 46 | uint8_t *m; |
| 47 | |
| 48 | ctx->x = 0; |
| 49 | ctx->y = 0; |
| 50 | m = ctx->m; |
| 51 | |
| 52 | for (i = 0; i < 256; i++) |
| 53 | m[i] = i; |
| 54 | |
| 55 | for (i = 0; i < 256; i++) |
| 56 | { |
| 57 | a = m[i]; |
| 58 | j = (uint8_t)(j + a + key[k]); |
| 59 | m[i] = m[j]; |
| 60 | m[j] = a; |
| 61 | |
| 62 | if (++k >= length) |
| 63 | k = 0; |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | /** |
| 68 | * Perform the encrypt/decrypt operation (can use it for either since |
| 69 | * this is a stream cipher). |
| 70 | * NOTE: *msg and *out must be the same pointer (performance tweak) |
| 71 | */ |
| 72 | void RC4_crypt(RC4_CTX *ctx, const uint8_t *msg, uint8_t *out, int length) |
| 73 | { |
| 74 | int i; |
| 75 | uint8_t *m, x, y, a, b; |
| 76 | |
| 77 | x = ctx->x; |
| 78 | y = ctx->y; |
| 79 | m = ctx->m; |
| 80 | |
| 81 | for (i = 0; i < length; i++) |
| 82 | { |
| 83 | a = m[++x]; |
| 84 | y += a; |
| 85 | m[x] = b = m[y]; |
| 86 | m[y] = a; |
| 87 | out[i] ^= m[(uint8_t)(a + b)]; |
| 88 | } |
| 89 | |
| 90 | ctx->x = x; |
| 91 | ctx->y = y; |
| 92 | } |