1 /*- 2 * SPDX-License-Identifier: ISC 3 * 4 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") 5 * Copyright (c) 1995,1999 by Internet Software Consortium. 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 17 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 20 #ifndef lint 21 static const char rcsid[] = "$Id: ns_samedomain.c,v 1.6 2005/04/27 04:56:40 sra Exp $"; 22 #endif 23 #include <sys/cdefs.h> 24 #include "port_before.h" 25 26 #include <sys/types.h> 27 #include <arpa/nameser.h> 28 #include <errno.h> 29 #include <string.h> 30 31 #include "port_after.h" 32 33 /*% 34 * Check whether a name belongs to a domain. 35 * 36 * Inputs: 37 *\li a - the domain whose ancestry is being verified 38 *\li b - the potential ancestor we're checking against 39 * 40 * Return: 41 *\li boolean - is a at or below b? 42 * 43 * Notes: 44 *\li Trailing dots are first removed from name and domain. 45 * Always compare complete subdomains, not only whether the 46 * domain name is the trailing string of the given name. 47 * 48 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in "" 49 * but NOT in "bar.top" 50 */ 51 52 int 53 ns_samedomain(const char *a, const char *b) { 54 size_t la, lb; 55 int diff, i, escaped; 56 const char *cp; 57 58 la = strlen(a); 59 lb = strlen(b); 60 61 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */ 62 if (la != 0U && a[la - 1] == '.') { 63 escaped = 0; 64 /* Note this loop doesn't get executed if la==1. */ 65 for (i = la - 2; i >= 0; i--) 66 if (a[i] == '\\') { 67 if (escaped) 68 escaped = 0; 69 else 70 escaped = 1; 71 } else 72 break; 73 if (!escaped) 74 la--; 75 } 76 77 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */ 78 if (lb != 0U && b[lb - 1] == '.') { 79 escaped = 0; 80 /* note this loop doesn't get executed if lb==1 */ 81 for (i = lb - 2; i >= 0; i--) 82 if (b[i] == '\\') { 83 if (escaped) 84 escaped = 0; 85 else 86 escaped = 1; 87 } else 88 break; 89 if (!escaped) 90 lb--; 91 } 92 93 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */ 94 if (lb == 0U) 95 return (1); 96 97 /* 'b' longer than 'a' means 'a' can't be in 'b'. */ 98 if (lb > la) 99 return (0); 100 101 /* 'a' and 'b' being equal at this point indicates sameness. */ 102 if (lb == la) 103 return (strncasecmp(a, b, lb) == 0); 104 105 /* Ok, we know la > lb. */ 106 107 diff = la - lb; 108 109 /* 110 * If 'a' is only 1 character longer than 'b', then it can't be 111 * a subdomain of 'b' (because of the need for the '.' label 112 * separator). 113 */ 114 if (diff < 2) 115 return (0); 116 117 /* 118 * If the character before the last 'lb' characters of 'b' 119 * isn't '.', then it can't be a match (this lets us avoid 120 * having "foobar.com" match "bar.com"). 121 */ 122 if (a[diff - 1] != '.') 123 return (0); 124 125 /* 126 * We're not sure about that '.', however. It could be escaped 127 * and thus not a really a label separator. 128 */ 129 escaped = 0; 130 for (i = diff - 2; i >= 0; i--) 131 if (a[i] == '\\') { 132 if (escaped) 133 escaped = 0; 134 else 135 escaped = 1; 136 } else 137 break; 138 if (escaped) 139 return (0); 140 141 /* Now compare aligned trailing substring. */ 142 cp = a + diff; 143 return (strncasecmp(cp, b, lb) == 0); 144 } 145 146 #ifndef _LIBC 147 /*% 148 * is "a" a subdomain of "b"? 149 */ 150 int 151 ns_subdomain(const char *a, const char *b) { 152 return (ns_samename(a, b) != 1 && ns_samedomain(a, b)); 153 } 154 #endif 155 156 /*% 157 * make a canonical copy of domain name "src" 158 * 159 * notes: 160 * \code 161 * foo -> foo. 162 * foo. -> foo. 163 * foo.. -> foo. 164 * foo\. -> foo\.. 165 * foo\\. -> foo\\. 166 * \endcode 167 */ 168 169 int 170 ns_makecanon(const char *src, char *dst, size_t dstsize) { 171 size_t n = strlen(src); 172 173 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */ 174 errno = EMSGSIZE; 175 return (-1); 176 } 177 strcpy(dst, src); 178 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */ 179 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */ 180 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */ 181 break; 182 else 183 dst[--n] = '\0'; 184 dst[n++] = '.'; 185 dst[n] = '\0'; 186 return (0); 187 } 188 189 /*% 190 * determine whether domain name "a" is the same as domain name "b" 191 * 192 * return: 193 *\li -1 on error 194 *\li 0 if names differ 195 *\li 1 if names are the same 196 */ 197 198 int 199 ns_samename(const char *a, const char *b) { 200 char ta[NS_MAXDNAME], tb[NS_MAXDNAME]; 201 202 if (ns_makecanon(a, ta, sizeof ta) < 0 || 203 ns_makecanon(b, tb, sizeof tb) < 0) 204 return (-1); 205 if (strcasecmp(ta, tb) == 0) 206 return (1); 207 else 208 return (0); 209 } 210 211 /*! \file */ 212