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 "port_before.h" 24 25 #include <sys/types.h> 26 #include <arpa/nameser.h> 27 #include <errno.h> 28 #include <string.h> 29 30 #include "port_after.h" 31 32 /*% 33 * Check whether a name belongs to a domain. 34 * 35 * Inputs: 36 *\li a - the domain whose ancestry is being verified 37 *\li b - the potential ancestor we're checking against 38 * 39 * Return: 40 *\li boolean - is a at or below b? 41 * 42 * Notes: 43 *\li Trailing dots are first removed from name and domain. 44 * Always compare complete subdomains, not only whether the 45 * domain name is the trailing string of the given name. 46 * 47 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in "" 48 * but NOT in "bar.top" 49 */ 50 51 int 52 ns_samedomain(const char *a, const char *b) { 53 size_t la, lb; 54 int diff, i, escaped; 55 const char *cp; 56 57 la = strlen(a); 58 lb = strlen(b); 59 60 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */ 61 if (la != 0U && a[la - 1] == '.') { 62 escaped = 0; 63 /* Note this loop doesn't get executed if la==1. */ 64 for (i = la - 2; i >= 0; i--) 65 if (a[i] == '\\') { 66 if (escaped) 67 escaped = 0; 68 else 69 escaped = 1; 70 } else 71 break; 72 if (!escaped) 73 la--; 74 } 75 76 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */ 77 if (lb != 0U && b[lb - 1] == '.') { 78 escaped = 0; 79 /* note this loop doesn't get executed if lb==1 */ 80 for (i = lb - 2; i >= 0; i--) 81 if (b[i] == '\\') { 82 if (escaped) 83 escaped = 0; 84 else 85 escaped = 1; 86 } else 87 break; 88 if (!escaped) 89 lb--; 90 } 91 92 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */ 93 if (lb == 0U) 94 return (1); 95 96 /* 'b' longer than 'a' means 'a' can't be in 'b'. */ 97 if (lb > la) 98 return (0); 99 100 /* 'a' and 'b' being equal at this point indicates sameness. */ 101 if (lb == la) 102 return (strncasecmp(a, b, lb) == 0); 103 104 /* Ok, we know la > lb. */ 105 106 diff = la - lb; 107 108 /* 109 * If 'a' is only 1 character longer than 'b', then it can't be 110 * a subdomain of 'b' (because of the need for the '.' label 111 * separator). 112 */ 113 if (diff < 2) 114 return (0); 115 116 /* 117 * If the character before the last 'lb' characters of 'b' 118 * isn't '.', then it can't be a match (this lets us avoid 119 * having "foobar.com" match "bar.com"). 120 */ 121 if (a[diff - 1] != '.') 122 return (0); 123 124 /* 125 * We're not sure about that '.', however. It could be escaped 126 * and thus not a really a label separator. 127 */ 128 escaped = 0; 129 for (i = diff - 2; i >= 0; i--) 130 if (a[i] == '\\') { 131 if (escaped) 132 escaped = 0; 133 else 134 escaped = 1; 135 } else 136 break; 137 if (escaped) 138 return (0); 139 140 /* Now compare aligned trailing substring. */ 141 cp = a + diff; 142 return (strncasecmp(cp, b, lb) == 0); 143 } 144 145 #ifndef _LIBC 146 /*% 147 * is "a" a subdomain of "b"? 148 */ 149 int 150 ns_subdomain(const char *a, const char *b) { 151 return (ns_samename(a, b) != 1 && ns_samedomain(a, b)); 152 } 153 #endif 154 155 /*% 156 * make a canonical copy of domain name "src" 157 * 158 * notes: 159 * \code 160 * foo -> foo. 161 * foo. -> foo. 162 * foo.. -> foo. 163 * foo\. -> foo\.. 164 * foo\\. -> foo\\. 165 * \endcode 166 */ 167 168 int 169 ns_makecanon(const char *src, char *dst, size_t dstsize) { 170 size_t n = strlen(src); 171 172 if (n + sizeof "." > dstsize) { /*%< Note: sizeof == 2 */ 173 errno = EMSGSIZE; 174 return (-1); 175 } 176 strcpy(dst, src); 177 while (n >= 1U && dst[n - 1] == '.') /*%< Ends in "." */ 178 if (n >= 2U && dst[n - 2] == '\\' && /*%< Ends in "\." */ 179 (n < 3U || dst[n - 3] != '\\')) /*%< But not "\\." */ 180 break; 181 else 182 dst[--n] = '\0'; 183 dst[n++] = '.'; 184 dst[n] = '\0'; 185 return (0); 186 } 187 188 /*% 189 * determine whether domain name "a" is the same as domain name "b" 190 * 191 * return: 192 *\li -1 on error 193 *\li 0 if names differ 194 *\li 1 if names are the same 195 */ 196 197 int 198 ns_samename(const char *a, const char *b) { 199 char ta[NS_MAXDNAME], tb[NS_MAXDNAME]; 200 201 if (ns_makecanon(a, ta, sizeof ta) < 0 || 202 ns_makecanon(b, tb, sizeof tb) < 0) 203 return (-1); 204 if (strcasecmp(ta, tb) == 0) 205 return (1); 206 else 207 return (0); 208 } 209 210 /*! \file */ 211