forked from osmocom/wireshark
9ba4c6e091
This has two expected uses: - Many current users of wmem_tree don't actually need the predecessor lookup it provides (the lookup_le function family). A hash map provides straight insertion and lookup much more efficiently than a wmem_tree when predecessor lookup isn't needed. - Many current users of glib's hash table and hash functions use untrusted data for keys, making them vulnerable to algorithmic complexity attacks. Care has been taken to make this implementation secure against such attacks, so it should be used whenever data is untrusted. In my benchmarks it is measurably slower than GHashTable, but not excessively so. Given the additional security it provides this seems like a reasonable trade-off (and it is still faster than a wmem_tree). Change-Id: I2d67a0d06029f14c153eaa42d5cfc774aefd9918 Reviewed-on: https://code.wireshark.org/review/1272 Reviewed-by: Evan Huus <eapache@gmail.com>
162 lines
4.9 KiB
C
162 lines
4.9 KiB
C
/* wmem_map.h
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* Definitions for the Wireshark Memory Manager Hash Map
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* Copyright 2014, Evan Huus <eapache@gmail.com>
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef __WMEM_MAP_H__
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#define __WMEM_MAP_H__
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#include <glib.h>
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#include "wmem_core.h"
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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/** @addtogroup wmem
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* @{
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* @defgroup wmem-map Hash Map
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*
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* A hash map implementation on top of wmem. Provides insertion, deletion and
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* lookup in expected amortized constant time. Uses universal hashing to map
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* keys into buckets, and provides a generic strong hash function that makes
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* it secure against algorithmic complexity attacks, and suitable for use
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* even with untrusted data.
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*
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* @{
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*/
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struct _wmem_map_t;
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typedef struct _wmem_map_t wmem_map_t;
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/** Creates a map with the given allocator scope. When the scope is emptied,
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* the map is fully destroyed. Items stored in it will not be freed unless they
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* were allocated from the same scope. For details on the GHashFunc and
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* GEqualFunc parameters, see the glib documentation at:
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* https://developer.gnome.org/glib/unstable/glib-Hash-Tables.html
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*
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* If the keys are coming from untrusted data, do *not* use glib's default hash
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* functions for strings, int64s or doubles. Wmem provides stronger equivalents
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* below. Feel free to use the g_direct_hash, g_int_hash, and any of the
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* g_*_equal functions though, as they should be safe.
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*
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* @param allocator The allocator scope with which to create the map.
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* @param hash_func The hash function used to place inserted keys.
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* @param eql_func The equality function used to compare inserted keys.
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* @return The newly-allocated map.
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*/
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WS_DLL_PUBLIC
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wmem_map_t *
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wmem_map_new(wmem_allocator_t *allocator,
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GHashFunc hash_func, GEqualFunc eql_func)
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G_GNUC_MALLOC;
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/** Inserts a value into the map.
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*
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* @param map The map to insert into.
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* @param key The key to insert by.
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* @param value The value to insert.
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* @return The previous value stored at this key if any, or NULL.
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*/
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WS_DLL_PUBLIC
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void *
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wmem_map_insert(wmem_map_t *map, const void *key, void *value);
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/** Lookup a value in the map.
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*
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* @param map The map to search in.
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* @param key The key to lookup.
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* @return The value stored at the key if any, or NULL.
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*/
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WS_DLL_PUBLIC
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void *
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wmem_map_lookup(wmem_map_t *map, const void *key);
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/** Remove a value from the map. If no value is stored at that key, nothing
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* happens.
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*
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* @param map The map to remove from.
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* @param key The key of the value to remove.
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* @return The (removed) value stored at the key if any, or NULL.
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*/
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WS_DLL_PUBLIC
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void *
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wmem_map_remove(wmem_map_t *map, const void *key);
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/** Compute a strong hash value for an arbitrary sequence of bytes. Use of this
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* hash value should be secure against algorithmic complexity attacks, even for
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* short keys. The computation uses a random seed which is generated on wmem
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* initialization, so the same key will hash to different values on different
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* runs of the application.
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*
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* @param buf The buffer of bytes (does not have to be aligned).
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* @param len The length of buf to use for the hash computation.
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* @return The hash value.
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*/
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WS_DLL_PUBLIC
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guint32
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wmem_strong_hash(const guint8 *buf, const size_t len);
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/** An implementation of GHashFunc using wmem_strong_hash. Prefer this over
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* g_str_hash when the data comes from an untrusted source.
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*/
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WS_DLL_PUBLIC
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guint
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wmem_str_hash(gconstpointer key);
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/** An implementation of GHashFunc using wmem_strong_hash. Prefer this over
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* g_int64_hash when the data comes from an untrusted source.
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*/
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WS_DLL_PUBLIC
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guint
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wmem_int64_hash(gconstpointer key);
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/** An implementation of GHashFunc using wmem_strong_hash. Prefer this over
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* g_double_hash when the data comes from an untrusted source.
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*/
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WS_DLL_PUBLIC
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guint
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wmem_double_hash(gconstpointer key);
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/** @}
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* @} */
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif /* __WMEM_MAP_H__ */
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/*
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* Editor modelines - http://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 4
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* tab-width: 8
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* indent-tabs-mode: nil
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* End:
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*
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* vi: set shiftwidth=4 tabstop=8 expandtab:
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* :indentSize=4:tabSize=8:noTabs=true:
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*/
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