/* * This module determines the type of socket (datagram, stream), the client * socket address and port, the server socket address and port. In addition, * it provides methods to map a transport address to a printable host name * or address. Socket address information results are in static memory. * * The result from the hostname lookup method is STRING_PARANOID when a host * pretends to have someone elses name, or when a host name is available but * could not be verified. * * When lookup or conversion fails the result is set to STRING_UNKNOWN. * * Diagnostics are reported through syslog(3). * * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. */ #ifndef lint static char sccsid[] = "@(#) socket.c 1.14 95/01/30 19:51:50"; #endif /* System libraries. */ #include #include #include #include #include #include #include #include extern char *inet_ntoa(); /* Local stuff. */ #include "tcpd.h" /* Forward declarations. */ static void sock_sink(); #ifdef APPEND_DOT /* * Speed up DNS lookups by terminating the host name with a dot. Should be * done with care. The speedup can give problems with lookups from sources * that lack DNS-style trailing dot magic, such as local files or NIS maps. */ static struct hostent *gethostbyname_dot(name) char *name; { char dot_name[MAXHOSTNAMELEN + 1]; /* * Don't append dots to unqualified names. Such names are likely to come * from local hosts files or from NIS. */ if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) { return (gethostbyname(name)); } else { sprintf(dot_name, "%s.", name); return (gethostbyname(dot_name)); } } #define gethostbyname gethostbyname_dot #endif /* sock_host - look up endpoint addresses and install conversion methods */ void sock_host(request) struct request_info *request; { static struct sockaddr_in client; static struct sockaddr_in server; int len; char buf[BUFSIZ]; int fd = request->fd; sock_methods(request); /* * Look up the client host address. Hal R. Brand * suggested how to get the client host info in case of UDP connections: * peek at the first message without actually looking at its contents. We * really should verify that client.sin_family gets the value AF_INET, * but this program has already caused too much grief on systems with * broken library code. */ len = sizeof(client); if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) { request->sink = sock_sink; len = sizeof(client); if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK, (struct sockaddr *) & client, &len) < 0) { tcpd_warn("can't get client address: %m"); return; /* give up */ } #ifdef really_paranoid memset(buf, 0 sizeof(buf)); #endif } request->client->sin = &client; /* * Determine the server binding. This is used for client username * lookups, and for access control rules that trigger on the server * address or name. */ len = sizeof(server); if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) { tcpd_warn("getsockname: %m"); return; } request->server->sin = &server; } /* sock_hostaddr - map endpoint address to printable form */ void sock_hostaddr(host) struct host_info *host; { struct sockaddr_in *sin = host->sin; if (sin != 0) STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr)); } /* sock_hostname - map endpoint address to host name */ void sock_hostname(host) struct host_info *host; { struct sockaddr_in *sin = host->sin; struct hostent *hp; int i; /* * On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does * not fail. Instead it returns "INADDR_ANY". Unfortunately, this does * not work the other way around: gethostbyname("INADDR_ANY") fails. We * have to special-case 0.0.0.0, in order to avoid false alerts from the * host name/address checking code below. */ if (sin != 0 && sin->sin_addr.s_addr != 0 && (hp = gethostbyaddr((char *) &(sin->sin_addr), sizeof(sin->sin_addr), AF_INET)) != 0) { STRN_CPY(host->name, hp->h_name, sizeof(host->name)); /* * Verify that the address is a member of the address list returned * by gethostbyname(hostname). * * Verify also that gethostbyaddr() and gethostbyname() return the same * hostname, or rshd and rlogind may still end up being spoofed. * * On some sites, gethostbyname("localhost") returns "localhost.domain". * This is a DNS artefact. We treat it as a special case. When we * can't believe the address list from gethostbyname("localhost") * we're in big trouble anyway. */ if ((hp = gethostbyname(host->name)) == 0) { /* * Unable to verify that the host name matches the address. This * may be a transient problem or a botched name server setup. */ tcpd_warn("can't verify hostname: gethostbyname(%s) failed", host->name); } else if (STR_NE(host->name, hp->h_name) && STR_NE(host->name, "localhost")) { /* * The gethostbyaddr() and gethostbyname() calls did not return * the same hostname. This could be a nameserver configuration * problem. It could also be that someone is trying to spoof us. */ tcpd_warn("host name/name mismatch: %s != %s", host->name, hp->h_name); } else { /* * The address should be a member of the address list returned by * gethostbyname(). We should first verify that the h_addrtype * field is AF_INET, but this program has already caused too much * grief on systems with broken library code. */ for (i = 0; hp->h_addr_list[i]; i++) { if (memcmp(hp->h_addr_list[i], (char *) &sin->sin_addr, sizeof(sin->sin_addr)) == 0) return; /* name is good, keep it */ } /* * The host name does not map to the initial address. Perhaps * someone has messed up. Perhaps someone compromised a name * server. */ tcpd_warn("host name/address mismatch: %s != %s", inet_ntoa(sin->sin_addr), hp->h_name); } strcpy(host->name, paranoid); /* name is bad, clobber it */ } } /* sock_sink - absorb unreceived IP datagram */ static void sock_sink(fd) int fd; { char buf[BUFSIZ]; struct sockaddr_in sin; int size = sizeof(sin); /* * Eat up the not-yet received datagram. Some systems insist on a * non-zero source address argument in the recvfrom() call below. */ (void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size); }