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: stable/10/contrib/tcp_wrappers/rfc931.c 311814 2017-01-09 20:14:02Z dim $
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(sig)
70int     sig;
71{
72    longjmp(timebuf, sig);
73}
74
75/* rfc931 - return remote user name, given socket structures */
76
77void    rfc931(rmt_sin, our_sin, dest)
78#ifdef INET6
79struct sockaddr *rmt_sin;
80struct sockaddr *our_sin;
81#else
82struct sockaddr_in *rmt_sin;
83struct sockaddr_in *our_sin;
84#endif
85char   *dest;
86{
87    unsigned rmt_port;
88    unsigned our_port;
89#ifdef INET6
90    struct sockaddr_storage rmt_query_sin;
91    struct sockaddr_storage our_query_sin;
92    int alen;
93#else
94    struct sockaddr_in rmt_query_sin;
95    struct sockaddr_in our_query_sin;
96#endif
97    char    user[256];			/* XXX */
98    char    buffer[512];		/* XXX */
99    char   *cp;
100    char   *result = unknown;
101    FILE   *fp;
102
103#ifdef INET6
104    /* address family must be the same */
105    if (rmt_sin->sa_family != our_sin->sa_family) {
106	STRN_CPY(dest, result, STRING_LENGTH);
107	return;
108    }
109    switch (our_sin->sa_family) {
110    case AF_INET:
111	alen = sizeof(struct sockaddr_in);
112	break;
113    case AF_INET6:
114	alen = sizeof(struct sockaddr_in6);
115	break;
116    default:
117	STRN_CPY(dest, result, STRING_LENGTH);
118	return;
119    }
120#endif
121
122    /*
123     * If we use a single, buffered, bidirectional stdio stream ("r+" or
124     * "w+" mode) we may read our own output. Such behaviour would make sense
125     * with resources that support random-access operations, but not with
126     * sockets. ANSI C suggests several functions which can be called when
127     * you want to change IO direction, fseek seems the most portable.
128     */
129
130#ifdef INET6
131    if ((fp = fsocket(our_sin->sa_family, SOCK_STREAM, 0)) != 0) {
132#else
133    if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
134#endif
135	/*
136	 * Set up a timer so we won't get stuck while waiting for the server.
137	 */
138
139	if (setjmp(timebuf) == 0) {
140	    signal(SIGALRM, timeout);
141	    alarm(rfc931_timeout);
142
143	    /*
144	     * Bind the local and remote ends of the query socket to the same
145	     * IP addresses as the connection under investigation. We go
146	     * through all this trouble because the local or remote system
147	     * might have more than one network address. The RFC931 etc.
148	     * client sends only port numbers; the server takes the IP
149	     * addresses from the query socket.
150	     */
151
152#ifdef INET6
153	    memcpy(&our_query_sin, our_sin, alen);
154	    memcpy(&rmt_query_sin, rmt_sin, alen);
155	    switch (our_sin->sa_family) {
156	    case AF_INET:
157		((struct sockaddr_in *)&our_query_sin)->sin_port = htons(ANY_PORT);
158		((struct sockaddr_in *)&rmt_query_sin)->sin_port = htons(RFC931_PORT);
159		break;
160	    case AF_INET6:
161		((struct sockaddr_in6 *)&our_query_sin)->sin6_port = htons(ANY_PORT);
162		((struct sockaddr_in6 *)&rmt_query_sin)->sin6_port = htons(RFC931_PORT);
163		break;
164	    }
165
166	    if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
167		     alen) >= 0 &&
168		connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
169			alen) >= 0) {
170#else
171	    our_query_sin = *our_sin;
172	    our_query_sin.sin_port = htons(ANY_PORT);
173	    rmt_query_sin = *rmt_sin;
174	    rmt_query_sin.sin_port = htons(RFC931_PORT);
175
176	    if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
177		     sizeof(our_query_sin)) >= 0 &&
178		connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
179			sizeof(rmt_query_sin)) >= 0) {
180#endif
181
182		/*
183		 * Send query to server. Neglect the risk that a 13-byte
184		 * write would have to be fragmented by the local system and
185		 * cause trouble with buggy System V stdio libraries.
186		 */
187
188		fprintf(fp, "%u,%u\r\n",
189#ifdef INET6
190			ntohs(((struct sockaddr_in *)rmt_sin)->sin_port),
191			ntohs(((struct sockaddr_in *)our_sin)->sin_port));
192#else
193			ntohs(rmt_sin->sin_port),
194			ntohs(our_sin->sin_port));
195#endif
196		fflush(fp);
197		fseek(fp, 0, SEEK_SET);
198
199		/*
200		 * Read response from server. Use fgets()/sscanf() so we can
201		 * work around System V stdio libraries that incorrectly
202		 * assume EOF when a read from a socket returns less than
203		 * requested.
204		 */
205
206		if (fgets(buffer, sizeof(buffer), fp) != 0
207		    && ferror(fp) == 0 && feof(fp) == 0
208		    && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
209			      &rmt_port, &our_port, user) == 3
210#ifdef INET6
211		    && ntohs(((struct sockaddr_in *)rmt_sin)->sin_port) == rmt_port
212		    && ntohs(((struct sockaddr_in *)our_sin)->sin_port) == our_port) {
213#else
214		    && ntohs(rmt_sin->sin_port) == rmt_port
215		    && ntohs(our_sin->sin_port) == our_port) {
216#endif
217
218		    /*
219		     * Strip trailing carriage return. It is part of the
220		     * protocol, not part of the data.
221		     */
222
223		    if (cp = strchr(user, '\r'))
224			*cp = 0;
225		    result = user;
226		}
227	    }
228	    alarm(0);
229	}
230	fclose(fp);
231    }
232    STRN_CPY(dest, result, STRING_LENGTH);
233}
234