keychain/trust/TrustedPeersTests/TPDummyDecrypter.m

   1 /*
   2  * Copyright (c) 2017 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #import "TPDummyDecrypter.h"
  25
  26 @implementation TPDummyDecrypter
  27
  28 + (instancetype)dummyDecrypter
  29 {
  30     return [[TPDummyDecrypter alloc] init];
  31 }
  32
  33 - (nullable NSData *)decryptData:(NSData *)ciphertext
  34                          withKey:(NSData *)key
  35                            error:(NSError **)error
  36 {
  37     // Repeating-key XOR
  38     NSMutableData *plaintext = [NSMutableData dataWithLength:ciphertext.length];
  39     uint8_t *plainbytes = plaintext.mutableBytes;
  40     const uint8_t *cipherbytes = ciphertext.bytes;
  41     const uint8_t *keybytes = key.bytes;
  42     NSUInteger keylen = key.length;
  43     for (NSUInteger i = 0; i < ciphertext.length; i++) {
  44         plainbytes[i] = cipherbytes[i] ^ keybytes[i % keylen];
  45     }
  46     return plaintext;
  47 }
  48
  49 @end