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 #include "port_before.h" 21 22 #include <sys/types.h> 23 #include <arpa/nameser.h> 24 #include <errno.h> 25 #include <string.h> 26 27 #include "port_after.h" 28 29 /*% 30 * Check whether a name belongs to a domain. 31 * 32 * Inputs: 33 *\li a - the domain whose ancestry is being verified 34 *\li b - the potential ancestor we're checking against 35 * 36 * Return: 37 *\li boolean - is a at or below b? 38 * 39 * Notes: 40 *\li Trailing dots are first removed from name and domain. 41 * Always compare complete subdomains, not only whether the 42 * domain name is the trailing string of the given name. 43 * 44 *\li "host.foobar.top" lies in "foobar.top" and in "top" and in "" 45 * but NOT in "bar.top" 46 */ 47 48 int 49 ns_samedomain(const char *a, const char *b) { 50 size_t la, lb; 51 int diff, i, escaped; 52 const char *cp; 53 54 la = strlen(a); 55 lb = strlen(b); 56 57 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'a'. */ 58 if (la != 0U && a[la - 1] == '.') { 59 escaped = 0; 60 /* Note this loop doesn't get executed if la==1. */ 61 for (i = la - 2; i >= 0; i--) 62 if (a[i] == '\\') { 63 if (escaped) 64 escaped = 0; 65 else 66 escaped = 1; 67 } else 68 break; 69 if (!escaped) 70 la--; 71 } 72 73 /* Ignore a trailing label separator (i.e. an unescaped dot) in 'b'. */ 74 if (lb != 0U && b[lb - 1] == '.') { 75 escaped = 0; 76 /* note this loop doesn't get executed if lb==1 */ 77 for (i = lb - 2; i >= 0; i--) 78 if (b[i] == '\\') { 79 if (escaped) 80 escaped = 0; 81 else 82 escaped = 1; 83 } else 84 break; 85 if (!escaped) 86 lb--; 87 } 88 89 /* lb == 0 means 'b' is the root domain, so 'a' must be in 'b'. */ 90 if (lb == 0U) 91 return (1); 92 93 /* 'b' longer than 'a' means 'a' can't be in 'b'. */ 94 if (lb > la) 95 return (0); 96 97 /* 'a' and 'b' being equal at this point indicates sameness. */ 98 if (lb == la) 99 return (strncasecmp(a, b, lb) == 0); 100 101 /* Ok, we know la > lb. */ 102 103 diff = la - lb; 104 105 /* 106 * If 'a' is only 1 character longer than 'b', then it can't be 107 * a subdomain of 'b' (because of the need for the '.' label 108 * separator). 109 */ 110 if (diff < 2) 111 return (0); 112 113 /* 114 * If the character before the last 'lb' characters of 'b' 115 * isn't '.', then it can't be a match (this lets us avoid 116 * having "foobar.com" match "bar.com"). 117 */ 118 if (a[diff - 1] != '.') 119 return (0); 120 121 /* 122 * We're not sure about that '.', however. It could be escaped 123 * and thus not a really a label separator. 124 */ 125 escaped = 0; 126 for (i = diff - 2; i >= 0; i--) 127 if (a[i] == '\\') { 128 if (escaped) 129 escaped = 0; 130 else 131 escaped = 1; 132 } else 133 break; 134 if (escaped) 135 return (0); 136 137 /* Now compare aligned trailing substring. */ 138 cp = a + diff; 139 return (strncasecmp(cp, b, lb) == 0); 140 } 141 142 #ifndef _LIBC 143 /*% 144 * is "a" a subdomain of "b"? 145 */ 146 int 147 ns_subdomain(const char *a, const char *b) { 148 return (ns_samename(a, b) != 1 && ns_samedomain(a, b)); 149 } 150 #endif 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