1 /* $NetBSD: rfc931.c,v 1.2 1997/10/09 21:20:46 christos Exp $ */ 2 3 /* 4 * rfc931() speaks a common subset of the RFC 931, AUTH, TAP, IDENT and RFC 5 * 1413 protocols. It queries an RFC 931 etc. compatible daemon on a remote 6 * host to look up the owner of a connection. The information should not be 7 * used for authentication purposes. This routine intercepts alarm signals. 8 * 9 * Diagnostics are reported through syslog(3). 10 * 11 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands. 12 */ 13 14 #include <sys/cdefs.h> 15 #ifndef lint 16 #if 0 17 static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34"; 18 #else 19 __RCSID("$NetBSD: rfc931.c,v 1.2 1997/10/09 21:20:46 christos Exp $"); 20 #endif 21 #endif 22 23 /* System libraries. */ 24 25 #include <stdio.h> 26 #include <syslog.h> 27 #include <sys/types.h> 28 #include <sys/socket.h> 29 #include <netinet/in.h> 30 #include <stdlib.h> 31 #include <unistd.h> 32 #include <setjmp.h> 33 #include <signal.h> 34 #include <string.h> 35 36 /* Local stuff. */ 37 38 #include "tcpd.h" 39 40 #define RFC931_PORT 113 /* Semi-well-known port */ 41 #define ANY_PORT 0 /* Any old port will do */ 42 43 int rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */ 44 45 static jmp_buf timebuf; 46 47 static FILE *fsocket __P((int, int, int)); 48 static void timeout __P((int)); 49 50 /* fsocket - open stdio stream on top of socket */ 51 52 static FILE *fsocket(domain, type, protocol) 53 int domain; 54 int type; 55 int protocol; 56 { 57 int s; 58 FILE *fp; 59 60 if ((s = socket(domain, type, protocol)) < 0) { 61 tcpd_warn("socket: %m"); 62 return (0); 63 } else { 64 if ((fp = fdopen(s, "r+")) == 0) { 65 tcpd_warn("fdopen: %m"); 66 close(s); 67 } 68 return (fp); 69 } 70 } 71 72 /* timeout - handle timeouts */ 73 74 static void timeout(sig) 75 int sig; 76 { 77 longjmp(timebuf, sig); 78 } 79 80 /* rfc931 - return remote user name, given socket structures */ 81 82 void rfc931(rmt_sin, our_sin, dest) 83 struct sockaddr_in *rmt_sin; 84 struct sockaddr_in *our_sin; 85 char *dest; 86 { 87 unsigned rmt_port; 88 unsigned our_port; 89 struct sockaddr_in rmt_query_sin; 90 struct sockaddr_in our_query_sin; 91 char user[256]; /* XXX */ 92 char buffer[512]; /* XXX */ 93 char *cp; 94 char *result = unknown; 95 FILE *fp; 96 97 #ifdef __GNUC__ 98 (void) &result; /* Avoid longjmp clobbering */ 99 #endif 100 101 /* 102 * Use one unbuffered stdio stream for writing to and for reading from 103 * the RFC931 etc. server. This is done because of a bug in the SunOS 104 * 4.1.x stdio library. The bug may live in other stdio implementations, 105 * too. When we use a single, buffered, bidirectional stdio stream ("r+" 106 * or "w+" mode) we read our own output. Such behaviour would make sense 107 * with resources that support random-access operations, but not with 108 * sockets. 109 */ 110 111 if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) { 112 setbuf(fp, (char *) 0); 113 114 /* 115 * Set up a timer so we won't get stuck while waiting for the server. 116 */ 117 118 if (setjmp(timebuf) == 0) { 119 signal(SIGALRM, timeout); 120 alarm(rfc931_timeout); 121 122 /* 123 * Bind the local and remote ends of the query socket to the same 124 * IP addresses as the connection under investigation. We go 125 * through all this trouble because the local or remote system 126 * might have more than one network address. The RFC931 etc. 127 * client sends only port numbers; the server takes the IP 128 * addresses from the query socket. 129 */ 130 131 our_query_sin = *our_sin; 132 our_query_sin.sin_port = htons(ANY_PORT); 133 rmt_query_sin = *rmt_sin; 134 rmt_query_sin.sin_port = htons(RFC931_PORT); 135 136 if (bind(fileno(fp), (struct sockaddr *) & our_query_sin, 137 sizeof(our_query_sin)) >= 0 && 138 connect(fileno(fp), (struct sockaddr *) & rmt_query_sin, 139 sizeof(rmt_query_sin)) >= 0) { 140 141 /* 142 * Send query to server. Neglect the risk that a 13-byte 143 * write would have to be fragmented by the local system and 144 * cause trouble with buggy System V stdio libraries. 145 */ 146 147 fprintf(fp, "%u,%u\r\n", 148 ntohs(rmt_sin->sin_port), 149 ntohs(our_sin->sin_port)); 150 fflush(fp); 151 152 /* 153 * Read response from server. Use fgets()/sscanf() so we can 154 * work around System V stdio libraries that incorrectly 155 * assume EOF when a read from a socket returns less than 156 * requested. 157 */ 158 159 if (fgets(buffer, sizeof(buffer), fp) != 0 160 && ferror(fp) == 0 && feof(fp) == 0 161 && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s", 162 &rmt_port, &our_port, user) == 3 163 && ntohs(rmt_sin->sin_port) == rmt_port 164 && ntohs(our_sin->sin_port) == our_port) { 165 166 /* 167 * Strip trailing carriage return. It is part of the 168 * protocol, not part of the data. 169 */ 170 171 if ((cp = strchr(user, '\r')) != NULL) 172 *cp = '\0'; 173 result = user; 174 } 175 } 176 alarm(0); 177 } 178 fclose(fp); 179 } 180 STRN_CPY(dest, result, STRING_LENGTH); 181 } 182