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