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