hash.c revision 1.3
1 /* $NetBSD: hash.c,v 1.3 2019/01/09 16:55:14 christos Exp $ */ 2 3 /* 4 * Copyright (C) Internet Systems Consortium, Inc. ("ISC") 5 * 6 * This Source Code Form is subject to the terms of the Mozilla Public 7 * License, v. 2.0. If a copy of the MPL was not distributed with this 8 * file, You can obtain one at http://mozilla.org/MPL/2.0/. 9 * 10 * See the COPYRIGHT file distributed with this work for additional 11 * information regarding copyright ownership. 12 */ 13 14 /* 15 * 32 bit Fowler/Noll/Vo FNV-1a hash code with modification for BIND 16 */ 17 18 #include <config.h> // IWYU pragma: keep 19 20 #include <stdbool.h> 21 #include <stddef.h> 22 #include <inttypes.h> 23 24 #include "isc/hash.h" // IWYU pragma: keep 25 #include "isc/likely.h" 26 #include "isc/once.h" 27 #include "isc/random.h" 28 #include "isc/result.h" 29 #include "isc/types.h" 30 #include "isc/util.h" 31 32 static uint32_t fnv_offset_basis; 33 static isc_once_t fnv_once = ISC_ONCE_INIT; 34 static bool fnv_initialized = false; 35 36 static unsigned char maptolower[] = { 37 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 38 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 39 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 40 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 41 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 42 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 43 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 44 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 45 0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 46 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 47 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 48 0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 49 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 50 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 51 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 52 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 53 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 54 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 55 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 56 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 57 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 58 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, 59 0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 60 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 61 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 62 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 63 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 64 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 65 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 66 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 67 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 68 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff 69 }; 70 71 static void 72 fnv_initialize(void) { 73 /* 74 * This function should not leave fnv_offset_basis set to 75 * 0. Also, after this function has been called, if it is called 76 * again, it should not change fnv_offset_basis. 77 */ 78 while (fnv_offset_basis == 0) { 79 fnv_offset_basis = isc_random32(); 80 } 81 82 fnv_initialized = true; 83 } 84 85 const void * 86 isc_hash_get_initializer(void) { 87 if (ISC_UNLIKELY(!fnv_initialized)) 88 RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == 89 ISC_R_SUCCESS); 90 91 return (&fnv_offset_basis); 92 } 93 94 void 95 isc_hash_set_initializer(const void *initializer) { 96 REQUIRE(initializer != NULL); 97 98 /* 99 * Ensure that fnv_initialize() is not called after 100 * isc_hash_set_initializer() is called. 101 */ 102 if (ISC_UNLIKELY(!fnv_initialized)) 103 RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == 104 ISC_R_SUCCESS); 105 106 fnv_offset_basis = *((const unsigned int *)initializer); 107 } 108 109 #define FNV_32_PRIME ((uint32_t)0x01000193) 110 111 uint32_t 112 isc_hash_function(const void *data, size_t length, bool case_sensitive, 113 const uint32_t *previous_hashp) 114 { 115 uint32_t hval; 116 const unsigned char *bp; 117 const unsigned char *be; 118 119 REQUIRE(length == 0 || data != NULL); 120 121 if (ISC_UNLIKELY(!fnv_initialized)) { 122 RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == 123 ISC_R_SUCCESS); 124 } 125 126 hval = ISC_UNLIKELY(previous_hashp != NULL) ? *previous_hashp 127 : fnv_offset_basis; 128 129 if (length == 0) { 130 return (hval); 131 } 132 133 bp = (const unsigned char *)data; 134 be = bp + length; 135 136 /* 137 * Fowler-Noll-Vo FNV-1a hash function. 138 * 139 * NOTE: A random FNV offset basis is used by default to avoid 140 * collision attacks as the hash function is reversible. This 141 * makes the mapping non-deterministic, but the distribution in 142 * the domain is still uniform. 143 */ 144 145 if (case_sensitive) { 146 while (bp < be) { 147 hval ^= *bp++; 148 hval *= FNV_32_PRIME; 149 } 150 } else { 151 while (bp < be) { 152 hval ^= maptolower[*bp++]; 153 hval *= FNV_32_PRIME; 154 } 155 } 156 157 return (hval); 158 } 159 160 uint32_t 161 isc_hash_function_reverse(const void *data, size_t length, bool case_sensitive, 162 const uint32_t *previous_hashp) 163 { 164 uint32_t hval; 165 const unsigned char *bp; 166 const unsigned char *be; 167 168 REQUIRE(length == 0 || data != NULL); 169 170 if (ISC_UNLIKELY(!fnv_initialized)) { 171 RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == 172 ISC_R_SUCCESS); 173 } 174 175 hval = ISC_UNLIKELY(previous_hashp != NULL) ? *previous_hashp 176 : fnv_offset_basis; 177 178 if (length == 0) { 179 return (hval); 180 } 181 182 bp = (const unsigned char *)data; 183 be = bp + length; 184 185 /* 186 * Fowler-Noll-Vo FNV-1a hash function. 187 * 188 * NOTE: A random FNV offset basis is used by default to avoid 189 * collision attacks as the hash function is reversible. This 190 * makes the mapping non-deterministic, but the distribution in 191 * the domain is still uniform. 192 */ 193 194 if (case_sensitive) { 195 while (--be >= bp) { 196 hval ^= *be; 197 hval *= FNV_32_PRIME; 198 } 199 } else { 200 while (--be >= bp) { 201 hval ^= maptolower[*be]; 202 hval *= FNV_32_PRIME; 203 } 204 } 205 206 return (hval); 207 } 208
Indexes created Tue Mar 03 05:31:39 UTC 2026