123 lines
3.4 KiB
C
123 lines
3.4 KiB
C
/*-
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* Copyright 2007-2009 Colin Percival
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file was originally written by Colin Percival as part of the Tarsnap
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* online backup system.
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <openssl/aes.h>
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#include "sysendian.h"
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#include "crypto_aesctr.h"
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struct crypto_aesctr {
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AES_KEY * key;
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uint64_t nonce;
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uint64_t bytectr;
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uint8_t buf[16];
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};
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/**
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* crypto_aesctr_init(key, nonce):
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* Prepare to encrypt/decrypt data with AES in CTR mode, using the provided
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* expanded key and nonce. The key provided must remain valid for the
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* lifetime of the stream.
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*/
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struct crypto_aesctr *
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crypto_aesctr_init(AES_KEY * key, uint64_t nonce)
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{
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struct crypto_aesctr * stream;
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/* Allocate memory. */
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if ((stream = malloc(sizeof(struct crypto_aesctr))) == NULL)
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goto err0;
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/* Initialize values. */
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stream->key = key;
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stream->nonce = nonce;
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stream->bytectr = 0;
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/* Success! */
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return (stream);
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err0:
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/* Failure! */
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return (NULL);
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}
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/**
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* crypto_aesctr_stream(stream, inbuf, outbuf, buflen):
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* Generate the next ${buflen} bytes of the AES-CTR stream and xor them with
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* bytes from ${inbuf}, writing the result into ${outbuf}. If the buffers
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* ${inbuf} and ${outbuf} overlap, they must be identical.
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*/
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void
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crypto_aesctr_stream(struct crypto_aesctr * stream, const uint8_t * inbuf,
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uint8_t * outbuf, size_t buflen)
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{
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uint8_t pblk[16];
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size_t pos;
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int bytemod;
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for (pos = 0; pos < buflen; pos++) {
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/* How far through the buffer are we? */
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bytemod = stream->bytectr % 16;
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/* Generate a block of cipherstream if needed. */
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if (bytemod == 0) {
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be64enc(pblk, stream->nonce);
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be64enc(pblk + 8, stream->bytectr / 16);
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AES_encrypt(pblk, stream->buf, stream->key);
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}
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/* Encrypt a byte. */
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outbuf[pos] = inbuf[pos] ^ stream->buf[bytemod];
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/* Move to the next byte of cipherstream. */
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stream->bytectr += 1;
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}
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}
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/**
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* crypto_aesctr_free(stream):
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* Free the provided stream object.
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*/
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void
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crypto_aesctr_free(struct crypto_aesctr * stream)
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{
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int i;
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/* Zero potentially sensitive information. */
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for (i = 0; i < 16; i++)
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stream->buf[i] = 0;
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stream->bytectr = stream->nonce = 0;
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/* Free the stream. */
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free(stream);
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}
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