mirror of
https://github.com/isc-projects/bind9.git
synced 2026-03-27 21:04:17 -04:00
125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/*
|
|
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
|
|
*
|
|
* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
*
|
|
* See the COPYRIGHT file distributed with this work for additional
|
|
* information regarding copyright ownership.
|
|
*/
|
|
|
|
|
|
#ifndef ISC_LFSR_H
|
|
#define ISC_LFSR_H 1
|
|
|
|
/*! \file isc/lfsr.h */
|
|
|
|
#include <inttypes.h>
|
|
|
|
#include <isc/lang.h>
|
|
#include <isc/types.h>
|
|
|
|
typedef struct isc_lfsr isc_lfsr_t;
|
|
|
|
/*%
|
|
* This function is called when reseeding is needed. It is allowed to
|
|
* modify any state in the LFSR in any way it sees fit OTHER THAN "bits".
|
|
*
|
|
* It MUST set "count" to a new value or the lfsr will never reseed again.
|
|
*
|
|
* Also, a reseed will never occur in the middle of an extraction. This
|
|
* is purely an optimization, and is probably what one would want.
|
|
*/
|
|
typedef void (*isc_lfsrreseed_t)(isc_lfsr_t *, void *);
|
|
|
|
/*%
|
|
* The members of this structure can be used by the application, but care
|
|
* needs to be taken to not change state once the lfsr is in operation.
|
|
*/
|
|
struct isc_lfsr {
|
|
uint32_t state; /*%< previous state */
|
|
unsigned int bits; /*%< length */
|
|
uint32_t tap; /*%< bit taps */
|
|
unsigned int count; /*%< reseed count (in BITS!) */
|
|
isc_lfsrreseed_t reseed; /*%< reseed function */
|
|
void *arg; /*%< reseed function argument */
|
|
};
|
|
|
|
ISC_LANG_BEGINDECLS
|
|
|
|
|
|
void
|
|
isc_lfsr_init(isc_lfsr_t *lfsr, uint32_t state, unsigned int bits,
|
|
uint32_t tap, unsigned int count,
|
|
isc_lfsrreseed_t reseed, void *arg);
|
|
/*%<
|
|
* Initialize an LFSR.
|
|
*
|
|
* Note:
|
|
*
|
|
*\li Putting untrusted values into this function will cause the LFSR to
|
|
* generate (perhaps) non-maximal length sequences.
|
|
*
|
|
* Requires:
|
|
*
|
|
*\li lfsr != NULL
|
|
*
|
|
*\li 8 <= bits <= 32
|
|
*
|
|
*\li tap != 0
|
|
*/
|
|
|
|
void
|
|
isc_lfsr_generate(isc_lfsr_t *lfsr, void *data, unsigned int count);
|
|
/*%<
|
|
* Returns "count" bytes of data from the LFSR.
|
|
*
|
|
* Requires:
|
|
*
|
|
*\li lfsr be valid.
|
|
*
|
|
*\li data != NULL.
|
|
*
|
|
*\li count > 0.
|
|
*/
|
|
|
|
void
|
|
isc_lfsr_skip(isc_lfsr_t *lfsr, unsigned int skip);
|
|
/*%<
|
|
* Skip "skip" states.
|
|
*
|
|
* Requires:
|
|
*
|
|
*\li lfsr be valid.
|
|
*/
|
|
|
|
uint32_t
|
|
isc_lfsr_generate32(isc_lfsr_t *lfsr1, isc_lfsr_t *lfsr2);
|
|
/*%<
|
|
* Given two LFSRs, use the current state from each to skip entries in the
|
|
* other. The next states are then xor'd together and returned.
|
|
*
|
|
* WARNING:
|
|
*
|
|
*\li This function is used only for very, very low security data, such
|
|
* as DNS message IDs where it is desired to have an unpredictable
|
|
* stream of bytes that are harder to predict than a simple flooding
|
|
* attack.
|
|
*
|
|
* Notes:
|
|
*
|
|
*\li Since the current state from each of the LFSRs is used to skip
|
|
* state in the other, it is important that no state be leaked
|
|
* from either LFSR.
|
|
*
|
|
* Requires:
|
|
*
|
|
*\li lfsr1 and lfsr2 be valid.
|
|
*
|
|
*\li 1 <= skipbits <= 31
|
|
*/
|
|
|
|
ISC_LANG_ENDDECLS
|
|
|
|
#endif /* ISC_LFSR_H */
|