12088Ssos /*
22088Ssos  * General skeleton for adding options to the access control language. The
32088Ssos  * features offered by this module are documented in the hosts_options(5)
42088Ssos  * manual page (source file: hosts_options.5, "nroff -man" format).
5  *
6  * Notes and warnings for those who want to add features:
7  *
8  * In case of errors, abort options processing and deny access. There are too
9  * many irreversible side effects to make error recovery feasible. For
10  * example, it makes no sense to continue after we have already changed the
11  * userid.
12  *
13  * In case of errors, do not terminate the process: the routines might be
14  * called from a long-running daemon that should run forever. Instead, call
15  * tcpd_jump() which does a non-local goto back into the hosts_access()
16  * routine.
17  *
18  * In case of severe errors, use clean_exit() instead of directly calling
19  * exit(), or the inetd may loop on an UDP request.
20  *
21  * In verification mode (for example, with the "tcpdmatch" command) the
22  * "dry_run" flag is set. In this mode, an option function should just "say"
23  * what it is going to do instead of really doing it.
24  *
25  * Some option functions do not return (for example, the twist option passes
26  * control to another program). In verification mode (dry_run flag is set)
27  * such options should clear the "dry_run" flag to inform the caller of this
28  * course of action.
29  *
30  * $FreeBSD: stable/10/contrib/tcp_wrappers/options.c 311814 2017-01-09 20:14:02Z dim $
31  */
32
33#ifndef lint
34static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
35#endif
36
37/* System libraries. */
38
39#include <sys/types.h>
40#include <sys/param.h>
41#include <sys/socket.h>
42#include <sys/stat.h>
43#include <netinet/in.h>
44#include <netdb.h>
45#include <stdio.h>
46#define SYSLOG_NAMES
47#include <syslog.h>
48#include <pwd.h>
49#include <grp.h>
50#include <ctype.h>
51#include <setjmp.h>
52#include <string.h>
53#include <unistd.h>
54#include <stdlib.h>
55
56#ifndef MAXPATHNAMELEN
57#define MAXPATHNAMELEN  BUFSIZ
58#endif
59
60/* Local stuff. */
61
62#include "tcpd.h"
63
64/* Options runtime support. */
65
66int     dry_run = 0;			/* flag set in verification mode */
67extern jmp_buf tcpd_buf;		/* tcpd_jump() support */
68
69/* Options parser support. */
70
71static char whitespace_eq[] = "= \t\r\n";
72#define whitespace (whitespace_eq + 1)
73
74static char *get_field();		/* chew :-delimited field off string */
75static char *chop_string();		/* strip leading and trailing blanks */
76
77/* List of functions that implement the options. Add yours here. */
78
79static void user_option();		/* execute "user name.group" option */
80static void group_option();		/* execute "group name" option */
81static void umask_option();		/* execute "umask mask" option */
82static void linger_option();		/* execute "linger time" option */
83static void keepalive_option();		/* execute "keepalive" option */
84static void spawn_option();		/* execute "spawn command" option */
85static void twist_option();		/* execute "twist command" option */
86static void rfc931_option();		/* execute "rfc931" option */
87static void setenv_option();		/* execute "setenv name value" */
88static void nice_option();		/* execute "nice" option */
89static void severity_option();		/* execute "severity value" */
90static void allow_option();		/* execute "allow" option */
91static void deny_option();		/* execute "deny" option */
92static void banners_option();		/* execute "banners path" option */
93
94/* Structure of the options table. */
95
96struct option {
97    char   *name;			/* keyword name, case is ignored */
98    void  (*func) ();			/* function that does the real work */
99    int     flags;			/* see below... */
100};
101
102#define NEED_ARG	(1<<1)		/* option requires argument */
103#define USE_LAST	(1<<2)		/* option must be last */
104#define OPT_ARG		(1<<3)		/* option has optional argument */
105#define EXPAND_ARG	(1<<4)		/* do %x expansion on argument */
106
107#define need_arg(o)	((o)->flags & NEED_ARG)
108#define opt_arg(o)	((o)->flags & OPT_ARG)
109#define permit_arg(o)	((o)->flags & (NEED_ARG | OPT_ARG))
110#define use_last(o)	((o)->flags & USE_LAST)
111#define expand_arg(o)	((o)->flags & EXPAND_ARG)
112
113/* List of known keywords. Add yours here. */
114
115static struct option option_table[] = {
116    "user", user_option, NEED_ARG,
117    "group", group_option, NEED_ARG,
118    "umask", umask_option, NEED_ARG,
119    "linger", linger_option, NEED_ARG,
120    "keepalive", keepalive_option, 0,
121    "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
122    "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
123    "rfc931", rfc931_option, OPT_ARG,
124    "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
125    "nice", nice_option, OPT_ARG,
126    "severity", severity_option, NEED_ARG,
127    "allow", allow_option, USE_LAST,
128    "deny", deny_option, USE_LAST,
129    "banners", banners_option, NEED_ARG,
130    0,
131};
132
133/* process_options - process access control options */
134
135void    process_options(options, request)
136char   *options;
137struct request_info *request;
138{
139    char   *key;
140    char   *value;
141    char   *curr_opt;
142    char   *next_opt;
143    struct option *op;
144    char    bf[BUFSIZ];
145
146    for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
147	next_opt = get_field((char *) 0);
148
149	/*
150	 * Separate the option into name and value parts. For backwards
151	 * compatibility we ignore exactly one '=' between name and value.
152	 */
153	curr_opt = chop_string(curr_opt);
154	if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
155	    if (*value != '=') {
156		*value++ = 0;
157		value += strspn(value, whitespace);
158	    }
159	    if (*value == '=') {
160		*value++ = 0;
161		value += strspn(value, whitespace);
162	    }
163	}
164	if (*value == 0)
165	    value = 0;
166	key = curr_opt;
167
168	/*
169	 * Disallow missing option names (and empty option fields).
170	 */
171	if (*key == 0)
172	    tcpd_jump("missing option name");
173
174	/*
175	 * Lookup the option-specific info and do some common error checks.
176	 * Delegate option-specific processing to the specific functions.
177	 */
178
179	for (op = option_table; op->name && STR_NE(op->name, key); op++)
180	     /* VOID */ ;
181	if (op->name == 0)
182	    tcpd_jump("bad option name: \"%s\"", key);
183	if (!value && need_arg(op))
184	    tcpd_jump("option \"%s\" requires value", key);
185	if (value && !permit_arg(op))
186	    tcpd_jump("option \"%s\" requires no value", key);
187	if (next_opt && use_last(op))
188	    tcpd_jump("option \"%s\" must be at end", key);
189	if (value && expand_arg(op))
190	    value = chop_string(percent_x(bf, sizeof(bf), value, request));
191	if (hosts_access_verbose)
192	    syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
193	(*(op->func)) (value, request);
194    }
195}
196
197/* allow_option - grant access */
198
199/* ARGSUSED */
200
201static void allow_option(value, request)
202char   *value;
203struct request_info *request;
204{
205    longjmp(tcpd_buf, AC_PERMIT);
206}
207
208/* deny_option - deny access */
209
210/* ARGSUSED */
211
212static void deny_option(value, request)
213char   *value;
214struct request_info *request;
215{
216    longjmp(tcpd_buf, AC_DENY);
217}
218
219/* banners_option - expand %<char>, terminate each line with CRLF */
220
221static void banners_option(value, request)
222char   *value;
223struct request_info *request;
224{
225    char    path[MAXPATHNAMELEN];
226    char    ibuf[BUFSIZ];
227    char    obuf[2 * BUFSIZ];
228    struct stat st;
229    int     ch;
230    FILE   *fp;
231
232    sprintf(path, "%s/%s", value, eval_daemon(request));
233    if ((fp = fopen(path, "r")) != 0) {
234	while ((ch = fgetc(fp)) == 0)
235	    write(request->fd, "", 1);
236	ungetc(ch, fp);
237	while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
238	    if (split_at(ibuf, '\n'))
239		strcat(ibuf, "\r\n");
240	    percent_x(obuf, sizeof(obuf), ibuf, request);
241	    write(request->fd, obuf, strlen(obuf));
242	}
243	fclose(fp);
244    } else if (stat(value, &st) < 0) {
245	tcpd_warn("%s: %m", value);
246    }
247}
248
249/* group_option - switch group id */
250
251/* ARGSUSED */
252
253static void group_option(value, request)
254char   *value;
255struct request_info *request;
256{
257    struct group *grp;
258    struct group *getgrnam();
259
260    if ((grp = getgrnam(value)) == 0)
261	tcpd_jump("unknown group: \"%s\"", value);
262    endgrent();
263
264    if (dry_run == 0 && setgid(grp->gr_gid))
265	tcpd_jump("setgid(%s): %m", value);
266}
267
268/* user_option - switch user id */
269
270/* ARGSUSED */
271
272static void user_option(value, request)
273char   *value;
274struct request_info *request;
275{
276    struct passwd *pwd;
277    struct passwd *getpwnam();
278    char   *group;
279
280    if ((group = split_at(value, '.')) != 0)
281	group_option(group, request);
282    if ((pwd = getpwnam(value)) == 0)
283	tcpd_jump("unknown user: \"%s\"", value);
284    endpwent();
285
286    if (dry_run == 0 && setuid(pwd->pw_uid))
287	tcpd_jump("setuid(%s): %m", value);
288}
289
290/* umask_option - set file creation mask */
291
292/* ARGSUSED */
293
294static void umask_option(value, request)
295char   *value;
296struct request_info *request;
297{
298    unsigned mask;
299    char    junk;
300
301    if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
302	tcpd_jump("bad umask value: \"%s\"", value);
303    (void) umask(mask);
304}
305
306/* spawn_option - spawn a shell command and wait */
307
308/* ARGSUSED */
309
310static void spawn_option(value, request)
311char   *value;
312struct request_info *request;
313{
314    if (dry_run == 0)
315	shell_cmd(value);
316}
317
318/* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
319
320/* ARGSUSED */
321
322static void linger_option(value, request)
323char   *value;
324struct request_info *request;
325{
326    struct linger linger;
327    char    junk;
328
329    if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
330	|| linger.l_linger < 0)
331	tcpd_jump("bad linger value: \"%s\"", value);
332    if (dry_run == 0) {
333	linger.l_onoff = (linger.l_linger != 0);
334	if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
335		       sizeof(linger)) < 0)
336	    tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
337    }
338}
339
340/* keepalive_option - set the socket keepalive option */
341
342/* ARGSUSED */
343
344static void keepalive_option(value, request)
345char   *value;
346struct request_info *request;
347{
348    static int on = 1;
349
350    if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
351				   (char *) &on, sizeof(on)) < 0)
352	tcpd_warn("setsockopt SO_KEEPALIVE: %m");
353}
354
355/* nice_option - set nice value */
356
357/* ARGSUSED */
358
359static void nice_option(value, request)
360char   *value;
361struct request_info *request;
362{
363    int     niceval = 10;
364    char    junk;
365
366    if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
367	tcpd_jump("bad nice value: \"%s\"", value);
368    if (dry_run == 0 && nice(niceval) < 0)
369	tcpd_warn("nice(%d): %m", niceval);
370}
371
372/* twist_option - replace process by shell command */
373
374static void twist_option(value, request)
375char   *value;
376struct request_info *request;
377{
378    char   *error;
379
380    if (dry_run != 0) {
381	dry_run = 0;
382    } else {
383	if (resident > 0)
384	    tcpd_jump("twist option in resident process");
385
386	syslog(deny_severity, "twist %s to %s", eval_client(request), value);
387
388	/* Before switching to the shell, set up stdin, stdout and stderr. */
389
390#define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
391
392	if (maybe_dup2(request->fd, 0) != 0 ||
393	    maybe_dup2(request->fd, 1) != 1 ||
394	    maybe_dup2(request->fd, 2) != 2) {
395	    error = "twist_option: dup: %m";
396	} else {
397	    if (request->fd > 2)
398		close(request->fd);
399	    (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
400	    error = "twist_option: /bin/sh: %m";
401	}
402
403	/* Something went wrong: we MUST terminate the process. */
404
405	tcpd_warn(error);
406	clean_exit(request);
407    }
408}
409
410/* rfc931_option - look up remote user name */
411
412static void rfc931_option(value, request)
413char   *value;
414struct request_info *request;
415{
416    int     timeout;
417    char    junk;
418
419    if (value != 0) {
420	if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
421	    tcpd_jump("bad rfc931 timeout: \"%s\"", value);
422	rfc931_timeout = timeout;
423    }
424    (void) eval_user(request);
425}
426
427/* setenv_option - set environment variable */
428
429/* ARGSUSED */
430
431static void setenv_option(value, request)
432char   *value;
433struct request_info *request;
434{
435    char   *var_value;
436
437    if (*(var_value = value + strcspn(value, whitespace)))
438	*var_value++ = 0;
439    if (setenv(chop_string(value), chop_string(var_value), 1))
440	tcpd_jump("memory allocation failure");
441}
442
443/* severity_map - lookup facility or severity value */
444
445static int severity_map(table, name)
446const CODE   *table;
447char   *name;
448{
449    const CODE *t;
450    int ret = -1;
451
452    for (t = table; t->c_name; t++)
453	if (STR_EQ(t->c_name, name)) {
454	    ret = t->c_val;
455	    break;
456	}
457    if (ret == -1)
458    	tcpd_jump("bad syslog facility or severity: \"%s\"", name);
459
460    return (ret);
461}
462
463/* severity_option - change logging severity for this event (Dave Mitchell) */
464
465/* ARGSUSED */
466
467static void severity_option(value, request)
468char   *value;
469struct request_info *request;
470{
471    char   *level = split_at(value, '.');
472
473    allow_severity = deny_severity = level ?
474	severity_map(facilitynames, value) | severity_map(prioritynames, level)
475	: severity_map(prioritynames, value);
476}
477
478/* get_field - return pointer to next field in string */
479
480static char *get_field(string)
481char   *string;
482{
483    static char *last = "";
484    char   *src;
485    char   *dst;
486    char   *ret;
487    int     ch;
488
489    /*
490     * This function returns pointers to successive fields within a given
491     * string. ":" is the field separator; warn if the rule ends in one. It
492     * replaces a "\:" sequence by ":", without treating the result of
493     * substitution as field terminator. A null argument means resume search
494     * where the previous call terminated. This function destroys its
495     * argument.
496     *
497     * Work from explicit source or from memory. While processing \: we
498     * overwrite the input. This way we do not have to maintain buffers for
499     * copies of input fields.
500     */
501
502    src = dst = ret = (string ? string : last);
503    if (src[0] == 0)
504	return (0);
505
506    while (ch = *src) {
507	if (ch == ':') {
508	    if (*++src == 0)
509		tcpd_warn("rule ends in \":\"");
510	    break;
511	}
512	if (ch == '\\' && src[1] == ':')
513	    src++;
514	*dst++ = *src++;
515    }
516    last = src;
517    *dst = 0;
518    return (ret);
519}
520
521/* chop_string - strip leading and trailing blanks from string */
522
523static char *chop_string(string)
524register char *string;
525{
526    char   *start = 0;
527    char   *end;
528    char   *cp;
529
530    for (cp = string; *cp; cp++) {
531	if (!isspace(*cp)) {
532	    if (start == 0)
533		start = cp;
534	    end = cp;
535	}
536    }
537    return (start ? (end[1] = 0, start) : cp);
538}
539