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| 1 /*- | |
| 2 * Copyright 2007-2009 Colin Percival | |
| 3 * All rights reserved. | |
| 4 * | |
| 5 * Redistribution and use in source and binary forms, with or without | |
| 6 * modification, are permitted provided that the following conditions | |
| 7 * are met: | |
| 8 * 1. Redistributions of source code must retain the above copyright | |
| 9 * notice, this list of conditions and the following disclaimer. | |
| 10 * 2. Redistributions in binary form must reproduce the above copyright | |
| 11 * notice, this list of conditions and the following disclaimer in the | |
| 12 * documentation and/or other materials provided with the distribution. | |
| 13 * | |
| 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND | |
| 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | |
| 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 24 * SUCH DAMAGE. | |
| 25 * | |
| 26 * This file was originally written by Colin Percival as part of the Tarsnap | |
| 27 * online backup system. | |
| 28 */ | |
| 29 #include "scrypt_platform.h" | |
| 30 | |
| 31 #include <stdint.h> | |
| 32 #include <stdlib.h> | |
| 33 | |
| 34 #include <openssl/aes.h> | |
| 35 | |
| 36 #include "sysendian.h" | |
| 37 | |
| 38 #include "crypto_aesctr.h" | |
| 39 | |
| 40 struct crypto_aesctr { | |
| 41 AES_KEY * key; | |
| 42 uint64_t nonce; | |
| 43 uint64_t bytectr; | |
| 44 uint8_t buf[16]; | |
| 45 }; | |
| 46 | |
| 47 /** | |
| 48 * crypto_aesctr_init(key, nonce): | |
| 49 * Prepare to encrypt/decrypt data with AES in CTR mode, using the provided | |
| 50 * expanded key and nonce. The key provided must remain valid for the | |
| 51 * lifetime of the stream. | |
| 52 */ | |
| 53 struct crypto_aesctr * | |
| 54 crypto_aesctr_init(AES_KEY * key, uint64_t nonce) | |
| 55 { | |
| 56 struct crypto_aesctr * stream; | |
| 57 | |
| 58 /* Allocate memory. */ | |
| 59 if ((stream = malloc(sizeof(struct crypto_aesctr))) == NULL) | |
| 60 goto err0; | |
| 61 | |
| 62 /* Initialize values. */ | |
| 63 stream->key = key; | |
| 64 stream->nonce = nonce; | |
| 65 stream->bytectr = 0; | |
| 66 | |
| 67 /* Success! */ | |
| 68 return (stream); | |
| 69 | |
| 70 err0: | |
| 71 /* Failure! */ | |
| 72 return (NULL); | |
| 73 } | |
| 74 | |
| 75 /** | |
| 76 * crypto_aesctr_stream(stream, inbuf, outbuf, buflen): | |
| 77 * Generate the next ${buflen} bytes of the AES-CTR stream and xor them with | |
| 78 * bytes from ${inbuf}, writing the result into ${outbuf}. If the buffers | |
| 79 * ${inbuf} and ${outbuf} overlap, they must be identical. | |
| 80 */ | |
| 81 void | |
| 82 crypto_aesctr_stream(struct crypto_aesctr * stream, const uint8_t * inbuf, | |
| 83 uint8_t * outbuf, size_t buflen) | |
| 84 { | |
| 85 uint8_t pblk[16]; | |
| 86 size_t pos; | |
| 87 int bytemod; | |
| 88 | |
| 89 for (pos = 0; pos < buflen; pos++) { | |
| 90 /* How far through the buffer are we? */ | |
| 91 bytemod = stream->bytectr % 16; | |
| 92 | |
| 93 /* Generate a block of cipherstream if needed. */ | |
| 94 if (bytemod == 0) { | |
| 95 be64enc(pblk, stream->nonce); | |
| 96 be64enc(pblk + 8, stream->bytectr / 16); | |
| 97 AES_encrypt(pblk, stream->buf, stream->key); | |
| 98 } | |
| 99 | |
| 100 /* Encrypt a byte. */ | |
| 101 outbuf[pos] = inbuf[pos] ^ stream->buf[bytemod]; | |
| 102 | |
| 103 /* Move to the next byte of cipherstream. */ | |
| 104 stream->bytectr += 1; | |
| 105 } | |
| 106 } | |
| 107 | |
| 108 /** | |
| 109 * crypto_aesctr_free(stream): | |
| 110 * Free the provided stream object. | |
| 111 */ | |
| 112 void | |
| 113 crypto_aesctr_free(struct crypto_aesctr * stream) | |
| 114 { | |
| 115 int i; | |
| 116 | |
| 117 /* Zero potentially sensitive information. */ | |
| 118 for (i = 0; i < 16; i++) | |
| 119 stream->buf[i] = 0; | |
| 120 stream->bytectr = stream->nonce = 0; | |
| 121 | |
| 122 /* Free the stream. */ | |
| 123 free(stream); | |
| 124 } | |
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