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
13static 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
34int rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
35
36static jmp_buf timebuf;
37
38/* fsocket - open stdio stream on top of socket */
39
40static FILE *fsocket(domain, type, protocol)
41int domain;
42int type;
43int 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
62static void timeout(sig)
63int sig;
64{
65 longjmp(timebuf, sig);
66}
67
68/* rfc931 - return remote user name, given socket structures */
69
70void rfc931(rmt_sin, our_sin, dest)
71struct sockaddr_in *rmt_sin;
72struct sockaddr_in *our_sin;
73char *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}