1 /* $NetBSD: socket.c,v 1.3 1997/10/09 21:20:50 christos Exp $ */ 2 3 /* 4 * This module determines the type of socket (datagram, stream), the client 5 * socket address and port, the server socket address and port. In addition, 6 * it provides methods to map a transport address to a printable host name 7 * or address. Socket address information results are in static memory. 8 * 9 * The result from the hostname lookup method is STRING_PARANOID when a host 10 * pretends to have someone elses name, or when a host name is available but 11 * could not be verified. 12 * 13 * When lookup or conversion fails the result is set to STRING_UNKNOWN. 14 * 15 * Diagnostics are reported through syslog(3). 16 * 17 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 18 */ 19 20 #include <sys/cdefs.h> 21 #ifndef lint 22 #if 0 23 static char sccsid[] = "@(#) socket.c 1.14 95/01/30 19:51:50"; 24 #else 25 __RCSID("$NetBSD: socket.c,v 1.3 1997/10/09 21:20:50 christos Exp $"); 26 #endif 27 #endif 28 29 /* System libraries. */ 30 31 #include <sys/types.h> 32 #include <sys/param.h> 33 #include <sys/socket.h> 34 #include <netinet/in.h> 35 #include <netdb.h> 36 #include <stdio.h> 37 #include <syslog.h> 38 #include <string.h> 39 #include <arpa/inet.h> 40 41 /* Local stuff. */ 42 43 #include "tcpd.h" 44 45 /* Forward declarations. */ 46 47 static void sock_sink __P((int)); 48 49 #ifdef APPEND_DOT 50 static struct hostent *gethostbyname_dot __P((char *)); 51 52 /* 53 * Speed up DNS lookups by terminating the host name with a dot. Should be 54 * done with care. The speedup can give problems with lookups from sources 55 * that lack DNS-style trailing dot magic, such as local files or NIS maps. 56 */ 57 58 static struct hostent *gethostbyname_dot(name) 59 char *name; 60 { 61 char dot_name[MAXHOSTNAMELEN + 1]; 62 63 /* 64 * Don't append dots to unqualified names. Such names are likely to come 65 * from local hosts files or from NIS. 66 */ 67 68 if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) { 69 return (gethostbyname(name)); 70 } else { 71 (void)snprintf(dot_name, sizeof dot_name, "%s.", name); 72 return (gethostbyname(dot_name)); 73 } 74 } 75 76 #define gethostbyname gethostbyname_dot 77 #endif 78 79 /* sock_host - look up endpoint addresses and install conversion methods */ 80 81 void sock_host(request) 82 struct request_info *request; 83 { 84 static struct sockaddr_in client; 85 static struct sockaddr_in server; 86 int len; 87 char buf[BUFSIZ]; 88 int fd = request->fd; 89 90 sock_methods(request); 91 92 /* 93 * Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov> 94 * suggested how to get the client host info in case of UDP connections: 95 * peek at the first message without actually looking at its contents. We 96 * really should verify that client.sin_family gets the value AF_INET, 97 * but this program has already caused too much grief on systems with 98 * broken library code. 99 */ 100 101 len = sizeof(client); 102 if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) { 103 request->sink = sock_sink; 104 len = sizeof(client); 105 if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK, 106 (struct sockaddr *) & client, &len) < 0) { 107 tcpd_warn("can't get client address: %m"); 108 return; /* give up */ 109 } 110 #ifdef really_paranoid 111 memset(buf, 0 sizeof(buf)); 112 #endif 113 } 114 request->client->sin = &client; 115 116 /* 117 * Determine the server binding. This is used for client username 118 * lookups, and for access control rules that trigger on the server 119 * address or name. 120 */ 121 122 len = sizeof(server); 123 if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) { 124 tcpd_warn("getsockname: %m"); 125 return; 126 } 127 request->server->sin = &server; 128 } 129 130 /* sock_hostaddr - map endpoint address to printable form */ 131 132 void sock_hostaddr(host) 133 struct host_info *host; 134 { 135 struct sockaddr_in *sin = host->sin; 136 137 if (sin != 0) 138 STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr)); 139 } 140 141 /* sock_hostname - map endpoint address to host name */ 142 143 void sock_hostname(host) 144 struct host_info *host; 145 { 146 struct sockaddr_in *sin = host->sin; 147 struct hostent *hp; 148 int i; 149 150 /* 151 * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does 152 * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does 153 * not work the other way around: gethostbyname("INADDR_ANY") fails. We 154 * have to special-case 0.0.0.0, in order to avoid false alerts from the 155 * host name/address checking code below. 156 */ 157 if (sin != 0 && sin->sin_addr.s_addr != 0 158 && (hp = gethostbyaddr((char *) &(sin->sin_addr), 159 sizeof(sin->sin_addr), AF_INET)) != 0) { 160 161 STRN_CPY(host->name, hp->h_name, sizeof(host->name)); 162 163 /* 164 * Verify that the address is a member of the address list returned 165 * by gethostbyname(hostname). 166 * 167 * Verify also that gethostbyaddr() and gethostbyname() return the same 168 * hostname, or rshd and rlogind may still end up being spoofed. 169 * 170 * On some sites, gethostbyname("localhost") returns "localhost.domain". 171 * This is a DNS artefact. We treat it as a special case. When we 172 * can't believe the address list from gethostbyname("localhost") 173 * we're in big trouble anyway. 174 */ 175 176 if ((hp = gethostbyname(host->name)) == 0) { 177 178 /* 179 * Unable to verify that the host name matches the address. This 180 * may be a transient problem or a botched name server setup. 181 */ 182 183 tcpd_warn("can't verify hostname: gethostbyname(%s) failed", 184 host->name); 185 186 } else if (STR_NE(host->name, hp->h_name) 187 && STR_NE(host->name, "localhost")) { 188 189 /* 190 * The gethostbyaddr() and gethostbyname() calls did not return 191 * the same hostname. This could be a nameserver configuration 192 * problem. It could also be that someone is trying to spoof us. 193 */ 194 195 tcpd_warn("host name/name mismatch: %s != %s", 196 host->name, hp->h_name); 197 198 } else { 199 200 /* 201 * The address should be a member of the address list returned by 202 * gethostbyname(). We should first verify that the h_addrtype 203 * field is AF_INET, but this program has already caused too much 204 * grief on systems with broken library code. 205 */ 206 207 for (i = 0; hp->h_addr_list[i]; i++) { 208 if (memcmp(hp->h_addr_list[i], 209 (char *) &sin->sin_addr, 210 sizeof(sin->sin_addr)) == 0) 211 return; /* name is good, keep it */ 212 } 213 214 /* 215 * The host name does not map to the initial address. Perhaps 216 * someone has messed up. Perhaps someone compromised a name 217 * server. 218 */ 219 220 tcpd_warn("host name/address mismatch: %s != %s", 221 inet_ntoa(sin->sin_addr), hp->h_name); 222 } 223 /* name is bad, clobber it */ 224 (void)strncpy(host->name, paranoid, sizeof(host->name) - 1); 225 } 226 } 227 228 /* sock_sink - absorb unreceived IP datagram */ 229 230 static void sock_sink(fd) 231 int fd; 232 { 233 char buf[BUFSIZ]; 234 struct sockaddr_in sin; 235 int size = sizeof(sin); 236 237 /* 238 * Eat up the not-yet received datagram. Some systems insist on a 239 * non-zero source address argument in the recvfrom() call below. 240 */ 241 242 (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size); 243 } 244