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
206 lines
6.4 KiB
C
206 lines
6.4 KiB
C
/* $NetBSD: hash.h,v 1.5 2014/12/10 04:38:00 christos Exp $ */
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/*
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* Copyright (C) 2004-2007, 2009, 2013, 2014 Internet Systems Consortium, Inc. ("ISC")
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* Copyright (C) 2003 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: hash.h,v 1.12 2009/01/17 23:47:43 tbox Exp */
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#ifndef ISC_HASH_H
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#define ISC_HASH_H 1
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#include <isc/types.h>
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/*****
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***** Module Info
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*****/
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/*! \file isc/hash.h
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*
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* \brief The hash API
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* provides an unpredictable hash value for variable length data.
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* A hash object contains a random vector (which is hidden from clients
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* of this API) to make the actual hash value unpredictable.
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*
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* The algorithm used in the API guarantees the probability of hash
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* collision; in the current implementation, as long as the values stored
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* in the random vector are unpredictable, the probability of hash
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* collision between arbitrary two different values is at most 1/2^16.
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*
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* Although the API is generic about the hash keys, it mainly expects
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* DNS names (and sometimes IPv4/v6 addresses) as inputs. It has an
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* upper limit of the input length, and may run slow to calculate the
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* hash values for large inputs.
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*
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* This API is designed to be general so that it can provide multiple
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* different hash contexts that have different random vectors. However,
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* it should be typical to have a single context for an entire system.
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* To support such cases, the API also provides a single-context mode.
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*
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* \li MP:
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* The hash object is almost read-only. Once the internal random vector
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* is initialized, no write operation will occur, and there will be no
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* need to lock the object to calculate actual hash values.
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*
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* \li Reliability:
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* In some cases this module uses low-level data copy to initialize the
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* random vector. Errors in this part are likely to crash the server or
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* corrupt memory.
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*
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* \li Resources:
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* A buffer, used as a random vector for calculating hash values.
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*
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* \li Security:
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* This module intends to provide unpredictable hash values in
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* adversarial environments in order to avoid denial of service attacks
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* to hash buckets.
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* Its unpredictability relies on the quality of entropy to build the
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* random vector.
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*
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* \li Standards:
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* None.
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*/
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/***
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*** Imports
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***/
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#include <isc/types.h>
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/***
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*** Functions
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***/
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ISC_LANG_BEGINDECLS
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isc_result_t
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isc_hash_ctxcreate(isc_mem_t *mctx, isc_entropy_t *entropy, size_t limit,
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isc_hash_t **hctx);
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isc_result_t
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isc_hash_create(isc_mem_t *mctx, isc_entropy_t *entropy, size_t limit);
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/*!<
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* \brief Create a new hash object.
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*
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* isc_hash_ctxcreate() creates a different object.
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*
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* isc_hash_create() creates a module-internal object to support the
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* single-context mode. It should be called only once.
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*
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* 'entropy' must be NULL or a valid entropy object. If 'entropy' is NULL,
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* pseudo random values will be used to build the random vector, which may
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* weaken security.
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*
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* 'limit' specifies the maximum number of hash keys. If it is too large,
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* these functions may fail.
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*/
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void
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isc_hash_ctxattach(isc_hash_t *hctx, isc_hash_t **hctxp);
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/*!<
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* \brief Attach to a hash object.
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*
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* This function is only necessary for the multiple-context mode.
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*/
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void
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isc_hash_ctxdetach(isc_hash_t **hctxp);
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/*!<
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* \brief Detach from a hash object.
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*
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* This function is for the multiple-context mode, and takes a valid
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* hash object as an argument.
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*/
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void
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isc_hash_destroy(void);
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/*!<
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* \brief This function is for the single-context mode, and is expected to be used
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* as a counterpart of isc_hash_create().
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*
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* A valid module-internal hash object must have been created, and this
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* function should be called only once.
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*/
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/*@{*/
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void
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isc_hash_ctxinit(isc_hash_t *hctx);
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void
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isc_hash_init(void);
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/*!<
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* \brief Initialize a hash object.
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*
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* It fills in the random vector with a proper
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* source of entropy, which is typically from the entropy object specified
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* at the creation. Thus, it is desirable to call these functions after
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* initializing the entropy object with some good entropy sources.
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*
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* These functions should be called before the first hash calculation.
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*
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* isc_hash_ctxinit() is for the multiple-context mode, and takes a valid hash
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* object as an argument.
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*
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* isc_hash_init() is for the single-context mode. A valid module-internal
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* hash object must have been created, and this function should be called only
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* once.
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*/
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/*@}*/
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/*@{*/
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unsigned int
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isc_hash_ctxcalc(isc_hash_t *hctx, const unsigned char *key,
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unsigned int keylen, isc_boolean_t case_sensitive);
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unsigned int
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isc_hash_calc(const unsigned char *key, unsigned int keylen,
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isc_boolean_t case_sensitive);
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/*!<
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* \brief Calculate a hash value.
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*
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* isc_hash_ctxinit() is for the multiple-context mode, and takes a valid hash
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* object as an argument.
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*
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* isc_hash_init() is for the single-context mode. A valid module-internal
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* hash object must have been created.
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*
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* 'key' is the hash key, which is a variable length buffer.
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*
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* 'keylen' specifies the key length, which must not be larger than the limit
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* specified for the corresponding hash object.
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*
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* 'case_sensitive' specifies whether the hash key should be treated as
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* case_sensitive values. It should typically be ISC_FALSE if the hash key
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* is a DNS name.
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*/
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/*@}*/
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void
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isc__hash_setvec(const isc_uint16_t *vec);
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/*!<
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* \brief Set the contents of the random vector used in hashing.
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*
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* WARNING: This function is meant to be used only in testing code. It
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* must not be used anywhere in normally running code.
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*
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* The hash context must have been created beforehand, otherwise this
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* function is a nop.
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*
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* 'vec' is not documented here on purpose. You should know what you are
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* doing before using this function.
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*/
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ISC_LANG_ENDDECLS
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#endif /* ISC_HASH_H */
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