/usr/include/isc/lfsr.h is in libbind-dev 1:9.11.3+dfsg-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 | /*
* Copyright (C) 1999-2001, 2004-2007, 2016 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/.
*/
/* $Id: lfsr.h,v 1.17 2007/06/19 23:47:18 tbox Exp $ */
#ifndef ISC_LFSR_H
#define ISC_LFSR_H 1
/*! \file isc/lfsr.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 {
isc_uint32_t state; /*%< previous state */
unsigned int bits; /*%< length */
isc_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, isc_uint32_t state, unsigned int bits,
isc_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.
*/
isc_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 */
|