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