tcpd.c revision 44743 
1 /*
2  * General front end for stream and datagram IP services. This program logs
3  * the remote host name and then invokes the real daemon. For example,
4  * install as /usr/etc/{tftpd,fingerd,telnetd,ftpd,rlogind,rshd,rexecd},
5  * after saving the real daemons in the directory specified with the
6  * REAL_DAEMON_DIR macro. This arrangement requires that the network daemons
7  * are started by inetd or something similar. Connections and diagnostics
8  * are logged through syslog(3).
9  *
10  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
11  */
12
13#ifndef lint
14static char sccsid[] = "@(#) tcpd.c 1.10 96/02/11 17:01:32";
15#endif
16
17/* System libraries. */
18
19#include <sys/types.h>
20#include <sys/param.h>
21#include <sys/stat.h>
22#include <sys/socket.h>
23#include <netinet/in.h>
24#include <stdio.h>
25#include <syslog.h>
26#include <string.h>
27
28#ifndef MAXPATHNAMELEN
29#define MAXPATHNAMELEN	BUFSIZ
30#endif
31
32#ifndef STDIN_FILENO
33#define STDIN_FILENO	0
34#endif
35
36/* Local stuff. */
37
38#include "patchlevel.h"
39#include "tcpd.h"
40
41int     allow_severity = SEVERITY;	/* run-time adjustable */
42int     deny_severity = LOG_WARNING;	/* ditto */
43
44main(argc, argv)
45int     argc;
46char  **argv;
47{
48    struct request_info request;
49    char    path[MAXPATHNAMELEN];
50
51    /* Attempt to prevent the creation of world-writable files. */
52
53#ifdef DAEMON_UMASK
54    umask(DAEMON_UMASK);
55#endif
56
57    /*
58     * If argv[0] is an absolute path name, ignore REAL_DAEMON_DIR, and strip
59     * argv[0] to its basename.
60     */
61
62    if (argv[0][0] == '/') {
63	strcpy(path, argv[0]);
64	argv[0] = strrchr(argv[0], '/') + 1;
65    } else {
66	sprintf(path, "%s/%s", REAL_DAEMON_DIR, argv[0]);
67    }
68
69    /*
70     * Open a channel to the syslog daemon. Older versions of openlog()
71     * require only two arguments.
72     */
73
74#ifdef LOG_MAIL
75    (void) openlog(argv[0], LOG_PID, FACILITY);
76#else
77    (void) openlog(argv[0], LOG_PID);
78#endif
79
80    /*
81     * Find out the endpoint addresses of this conversation. Host name
82     * lookups and double checks will be done on demand.
83     */
84
85    request_init(&request, RQ_DAEMON, argv[0], RQ_FILE, STDIN_FILENO, 0);
86    fromhost(&request);
87
88    /*
89     * Optionally look up and double check the remote host name. Sites
90     * concerned with security may choose to refuse connections from hosts
91     * that pretend to have someone elses host name.
92     */
93
94#ifdef PARANOID
95    if (STR_EQ(eval_hostname(request.client), paranoid))
96	refuse(&request);
97#endif
98
99    /*
100     * The BSD rlogin and rsh daemons that came out after 4.3 BSD disallow
101     * socket options at the IP level. They do so for a good reason.
102     * Unfortunately, we cannot use this with SunOS 4.1.x because the
103     * getsockopt() system call can panic the system.
104     */
105
106#ifdef KILL_IP_OPTIONS
107    fix_options(&request);
108#endif
109
110    /*
111     * Check whether this host can access the service in argv[0]. The
112     * access-control code invokes optional shell commands as specified in
113     * the access-control tables.
114     */
115
116#ifdef HOSTS_ACCESS
117    if (!hosts_access(&request))
118	refuse(&request);
119#endif
120
121    /* Report request and invoke the real daemon program. */
122
123    syslog(allow_severity, "connect from %s", eval_client(&request));
124    closelog();
125    (void) execv(path, argv);
126    syslog(LOG_ERR, "error: cannot execute %s: %m", path);
127    clean_exit(&request);
128    /* NOTREACHED */
129}
130