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