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  * $FreeBSD$
12  */
13
14#ifndef lint
15static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34";
16#endif
17
18/* System libraries. */
19
20#include <stdio.h>
21#include <syslog.h>
22#include <sys/types.h>
23#include <sys/socket.h>
24#include <netinet/in.h>
25#include <setjmp.h>
26#include <signal.h>
27#include <string.h>
28#include <unistd.h>
29
30#ifndef SEEK_SET
31#define SEEK_SET 0
32#endif
33
34/* Local stuff. */
35
36#include "tcpd.h"
37
38#define	RFC931_PORT	113		/* Semi-well-known port */
39#define	ANY_PORT	0		/* Any old port will do */
40
41int     rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
42
43static jmp_buf timebuf;
44
45/* fsocket - open stdio stream on top of socket */
46
47static FILE *fsocket(domain, type, protocol)
48int     domain;
49int     type;
50int     protocol;
51{
52    int     s;
53    FILE   *fp;
54
55    if ((s = socket(domain, type, protocol)) < 0) {
56	tcpd_warn("socket: %m");
57	return (0);
58    } else {
59	if ((fp = fdopen(s, "r+")) == 0) {
60	    tcpd_warn("fdopen: %m");
61	    close(s);
62	}
63	return (fp);
64    }
65}
66
67/* timeout - handle timeouts */
68
69static void timeout(int sig)
70{
71    longjmp(timebuf, sig);
72}
73
74/* rfc931 - return remote user name, given socket structures */
75
76void    rfc931(rmt_sin, our_sin, dest)
77#ifdef INET6
78struct sockaddr *rmt_sin;
79struct sockaddr *our_sin;
80#else
81struct sockaddr_in *rmt_sin;
82struct sockaddr_in *our_sin;
83#endif
84char   *dest;
85{
86    unsigned rmt_port;
87    unsigned our_port;
88#ifdef INET6
89    struct sockaddr_storage rmt_query_sin;
90    struct sockaddr_storage our_query_sin;
91    int alen;
92#else
93    struct sockaddr_in rmt_query_sin;
94    struct sockaddr_in our_query_sin;
95#endif
96    char    user[256];			/* XXX */
97    char    buffer[512];		/* XXX */
98    char   *cp;
99    char   *result = unknown;
100    FILE   *fp;
101
102#ifdef INET6
103    /* address family must be the same */
104    if (rmt_sin->sa_family != our_sin->sa_family) {
105	STRN_CPY(dest, result, STRING_LENGTH);
106	return;
107    }
108    switch (our_sin->sa_family) {
109    case AF_INET:
110	alen = sizeof(struct sockaddr_in);
111	break;
112    case AF_INET6:
113	alen = sizeof(struct sockaddr_in6);
114	break;
115    default:
116	STRN_CPY(dest, result, STRING_LENGTH);
117	return;
118    }
119#endif
120
121    /*
122     * If we use a single, buffered, bidirectional stdio stream ("r+" or
123     * "w+" mode) we may read our own output. Such behaviour would make sense
124     * with resources that support random-access operations, but not with
125     * sockets. ANSI C suggests several functions which can be called when
126     * you want to change IO direction, fseek seems the most portable.
127     */
128
129#ifdef INET6
130    if ((fp = fsocket(our_sin->sa_family, SOCK_STREAM, 0)) != 0) {
131#else
132    if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
133#endif
134	/*
135	 * Set up a timer so we won't get stuck while waiting for the server.
136	 */
137
138	if (setjmp(timebuf) == 0) {
139	    signal(SIGALRM, timeout);
140	    alarm(rfc931_timeout);
141
142	    /*
143	     * Bind the local and remote ends of the query socket to the same
144	     * IP addresses as the connection under investigation. We go
145	     * through all this trouble because the local or remote system
146	     * might have more than one network address. The RFC931 etc.
147	     * client sends only port numbers; the server takes the IP
148	     * addresses from the query socket.
149	     */
150
151#ifdef INET6
152	    memcpy(&our_query_sin, our_sin, alen);
153	    memcpy(&rmt_query_sin, rmt_sin, alen);
154	    switch (our_sin->sa_family) {
155	    case AF_INET:
156		((struct sockaddr_in *)&our_query_sin)->sin_port = htons(ANY_PORT);
157		((struct sockaddr_in *)&rmt_query_sin)->sin_port = htons(RFC931_PORT);
158		break;
159	    case AF_INET6:
160		((struct sockaddr_in6 *)&our_query_sin)->sin6_port = htons(ANY_PORT);
161		((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port = htons(RFC931_PORT);
162		break;
163	    }
164
165	    if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
166		     alen) >= 0 &&
167		connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
168			alen) >= 0) {
169#else
170	    our_query_sin = *our_sin;
171	    our_query_sin.sin_port = htons(ANY_PORT);
172	    rmt_query_sin = *rmt_sin;
173	    rmt_query_sin.sin_port = htons(RFC931_PORT);
174
175	    if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
176		     sizeof(our_query_sin)) >= 0 &&
177		connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
178			sizeof(rmt_query_sin)) >= 0) {
179#endif
180
181		/*
182		 * Send query to server. Neglect the risk that a 13-byte
183		 * write would have to be fragmented by the local system and
184		 * cause trouble with buggy System V stdio libraries.
185		 */
186
187		fprintf(fp, "%u,%u\r\n",
188#ifdef INET6
189			ntohs(((struct sockaddr_in *)rmt_sin)->sin_port),
190			ntohs(((struct sockaddr_in *)our_sin)->sin_port));
191#else
192			ntohs(rmt_sin->sin_port),
193			ntohs(our_sin->sin_port));
194#endif
195		fflush(fp);
196		fseek(fp, 0, SEEK_SET);
197
198		/*
199		 * Read response from server. Use fgets()/sscanf() so we can
200		 * work around System V stdio libraries that incorrectly
201		 * assume EOF when a read from a socket returns less than
202		 * requested.
203		 */
204
205		if (fgets(buffer, sizeof(buffer), fp) != 0
206		    && ferror(fp) == 0 && feof(fp) == 0
207		    && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
208			      &rmt_port, &our_port, user) == 3
209#ifdef INET6
210		    && ntohs(((struct sockaddr_in *)rmt_sin)->sin_port) == rmt_port
211		    && ntohs(((struct sockaddr_in *)our_sin)->sin_port) == our_port) {
212#else
213		    && ntohs(rmt_sin->sin_port) == rmt_port
214		    && ntohs(our_sin->sin_port) == our_port) {
215#endif
216
217		    /*
218		     * Strip trailing carriage return. It is part of the
219		     * protocol, not part of the data.
220		     */
221
222		    if (cp = strchr(user, '\r'))
223			*cp = 0;
224		    result = user;
225		}
226	    }
227	    alarm(0);
228	}
229	fclose(fp);
230    }
231    STRN_CPY(dest, result, STRING_LENGTH);
232}
233