00b67f09dd
Also known as ISC bind. This import adds utilities such as host(1), dig(1), and nslookup(1), as well as many other tools and libraries. Change-Id: I035ca46e64f1965d57019e773f4ff0ef035e4aa3
133 lines
3.5 KiB
C
133 lines
3.5 KiB
C
/* $NetBSD: lfsr.h,v 1.4 2014/12/10 04:38:00 christos Exp $ */
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/*
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* Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
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* Copyright (C) 1999-2001 Internet Software Consortium.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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/* Id: lfsr.h,v 1.17 2007/06/19 23:47:18 tbox Exp */
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#ifndef ISC_LFSR_H
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#define ISC_LFSR_H 1
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/*! \file isc/lfsr.h */
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#include <isc/lang.h>
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#include <isc/types.h>
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typedef struct isc_lfsr isc_lfsr_t;
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/*%
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* This function is called when reseeding is needed. It is allowed to
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* modify any state in the LFSR in any way it sees fit OTHER THAN "bits".
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*
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* It MUST set "count" to a new value or the lfsr will never reseed again.
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*
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* Also, a reseed will never occur in the middle of an extraction. This
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* is purely an optimization, and is probably what one would want.
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*/
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typedef void (*isc_lfsrreseed_t)(isc_lfsr_t *, void *);
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/*%
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* The members of this structure can be used by the application, but care
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* needs to be taken to not change state once the lfsr is in operation.
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*/
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struct isc_lfsr {
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isc_uint32_t state; /*%< previous state */
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unsigned int bits; /*%< length */
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isc_uint32_t tap; /*%< bit taps */
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unsigned int count; /*%< reseed count (in BITS!) */
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isc_lfsrreseed_t reseed; /*%< reseed function */
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void *arg; /*%< reseed function argument */
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};
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ISC_LANG_BEGINDECLS
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void
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isc_lfsr_init(isc_lfsr_t *lfsr, isc_uint32_t state, unsigned int bits,
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isc_uint32_t tap, unsigned int count,
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isc_lfsrreseed_t reseed, void *arg);
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/*%<
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* Initialize an LFSR.
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*
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* Note:
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*
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*\li Putting untrusted values into this function will cause the LFSR to
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* generate (perhaps) non-maximal length sequences.
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*
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* Requires:
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*
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*\li lfsr != NULL
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*
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*\li 8 <= bits <= 32
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*
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*\li tap != 0
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*/
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void
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isc_lfsr_generate(isc_lfsr_t *lfsr, void *data, unsigned int count);
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/*%<
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* Returns "count" bytes of data from the LFSR.
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*
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* Requires:
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*
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*\li lfsr be valid.
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*
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*\li data != NULL.
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*
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*\li count > 0.
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*/
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void
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isc_lfsr_skip(isc_lfsr_t *lfsr, unsigned int skip);
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/*%<
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* Skip "skip" states.
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*
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* Requires:
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*
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*\li lfsr be valid.
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*/
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isc_uint32_t
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isc_lfsr_generate32(isc_lfsr_t *lfsr1, isc_lfsr_t *lfsr2);
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/*%<
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* Given two LFSRs, use the current state from each to skip entries in the
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* other. The next states are then xor'd together and returned.
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*
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* WARNING:
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*
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*\li This function is used only for very, very low security data, such
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* as DNS message IDs where it is desired to have an unpredictable
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* stream of bytes that are harder to predict than a simple flooding
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* attack.
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*
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* Notes:
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*
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*\li Since the current state from each of the LFSRs is used to skip
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* state in the other, it is important that no state be leaked
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* from either LFSR.
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*
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* Requires:
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*
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*\li lfsr1 and lfsr2 be valid.
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*
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*\li 1 <= skipbits <= 31
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*/
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ISC_LANG_ENDDECLS
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#endif /* ISC_LFSR_H */
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