1/*
2 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
3 * Use is subject to license terms.
4 */
5
6#pragma ident	"%Z%%M%	%I%	%E% SMI"
7
8 /*
9  * This module implements a simple access control language that is based on
10  * host (or domain) names, NIS (host) netgroup names, IP addresses (or
11  * network numbers) and daemon process names. When a match is found the
12  * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
13  * a list of options is executed or an optional shell command is executed.
14  *
15  * Host and user names are looked up on demand, provided that suitable endpoint
16  * information is available as sockaddr_in structures or TLI netbufs. As a
17  * side effect, the pattern matching process may change the contents of
18  * request structure fields.
19  *
20  * Diagnostics are reported through syslog(3).
21  *
22  * Compile with -DNETGROUP if your library provides support for netgroups.
23  *
24  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
25  */
26
27#ifndef lint
28static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
29#endif
30
31/* System libraries. */
32
33#include <sys/types.h>
34#include <sys/param.h>
35#include <netinet/in.h>
36#include <arpa/inet.h>
37#include <rpcsvc/ypclnt.h>
38#include <netdb.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <unistd.h>
42#include <syslog.h>
43#include <ctype.h>
44#include <errno.h>
45#include <setjmp.h>
46#include <string.h>
47
48extern char *fgets();
49extern int errno;
50
51#ifndef	INADDR_NONE
52#define	INADDR_NONE	(-1)		/* XXX should be 0xffffffff */
53#endif
54
55/* Local stuff. */
56
57#include "tcpd.h"
58
59/* Error handling. */
60
61extern jmp_buf tcpd_buf;
62
63/* Delimiters for lists of daemons or clients. */
64
65static char sep[] = ", \t\r\n";
66
67/* Constants to be used in assignments only, not in comparisons... */
68
69#define	YES		1
70#define	NO		0
71
72 /*
73  * These variables are globally visible so that they can be redirected in
74  * verification mode.
75  */
76
77char   *hosts_allow_table = HOSTS_ALLOW;
78char   *hosts_deny_table = HOSTS_DENY;
79int     hosts_access_verbose = 0;
80
81 /*
82  * In a long-running process, we are not at liberty to just go away.
83  */
84
85int     resident = (-1);		/* -1, 0: unknown; +1: yes */
86
87/* Forward declarations. */
88
89static int table_match();
90static int list_match();
91static int server_match();
92static int client_match();
93static int host_match();
94static int string_match();
95static int masked_match();
96#ifdef HAVE_IPV6
97static void ipv6_mask();
98#endif
99
100/* Size of logical line buffer. */
101
102#define	BUFLEN 2048
103
104/* hosts_access - host access control facility */
105
106int     hosts_access(request)
107struct request_info *request;
108{
109    int     verdict;
110
111    /*
112     * If the (daemon, client) pair is matched by an entry in the file
113     * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
114     * client) pair is matched by an entry in the file /etc/hosts.deny,
115     * access is denied. Otherwise, access is granted. A non-existent
116     * access-control file is treated as an empty file.
117     *
118     * After a rule has been matched, the optional language extensions may
119     * decide to grant or refuse service anyway. Or, while a rule is being
120     * processed, a serious error is found, and it seems better to play safe
121     * and deny service. All this is done by jumping back into the
122     * hosts_access() routine, bypassing the regular return from the
123     * table_match() function calls below.
124     */
125
126    if (resident <= 0)
127	resident++;
128    verdict = setjmp(tcpd_buf);
129    if (verdict != 0)
130	return (verdict == AC_PERMIT);
131    if (table_match(hosts_allow_table, request))
132	return (YES);
133    if (table_match(hosts_deny_table, request))
134	return (NO);
135    return (YES);
136}
137
138/* table_match - match table entries with (daemon, client) pair */
139
140static int table_match(table, request)
141char   *table;
142struct request_info *request;
143{
144    FILE   *fp;
145    char    sv_list[BUFLEN];		/* becomes list of daemons */
146    char   *cl_list;			/* becomes list of clients */
147    char   *sh_cmd;			/* becomes optional shell command */
148    int     match = NO;
149    struct tcpd_context saved_context;
150
151    saved_context = tcpd_context;		/* stupid compilers */
152
153    /*
154     * Between the fopen() and fclose() calls, avoid jumps that may cause
155     * file descriptor leaks.
156     */
157
158    if ((fp = fopen(table, "r")) != 0) {
159	tcpd_context.file = table;
160	tcpd_context.line = 0;
161	while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
162	    if (sv_list[strlen(sv_list) - 1] != '\n') {
163		tcpd_warn("missing newline or line too long");
164		continue;
165	    }
166	    if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
167		continue;
168	    if ((cl_list = split_at(skip_ipv6_addrs(sv_list), ':')) == 0) {
169		tcpd_warn("missing \":\" separator");
170		continue;
171	    }
172	    sh_cmd = split_at(skip_ipv6_addrs(cl_list), ':');
173	    match = list_match(sv_list, request, server_match)
174		&& list_match(cl_list, request, client_match);
175	}
176	(void) fclose(fp);
177    } else if (errno != ENOENT) {
178	tcpd_warn("cannot open %s: %m", table);
179    }
180    if (match) {
181	if (hosts_access_verbose > 1)
182	    syslog(LOG_DEBUG, "matched:  %s line %d",
183		   tcpd_context.file, tcpd_context.line);
184	if (sh_cmd) {
185#ifdef PROCESS_OPTIONS
186	    process_options(sh_cmd, request);
187#else
188	    char    cmd[BUFSIZ];
189	    shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
190#endif
191	}
192    }
193    tcpd_context = saved_context;
194    return (match);
195}
196
197/* list_match - match a request against a list of patterns with exceptions */
198
199static int list_match(list, request, match_fn)
200char   *list;
201struct request_info *request;
202int   (*match_fn) ();
203{
204    char   *tok;
205
206    /*
207     * Process tokens one at a time. We have exhausted all possible matches
208     * when we reach an "EXCEPT" token or the end of the list. If we do find
209     * a match, look for an "EXCEPT" list and recurse to determine whether
210     * the match is affected by any exceptions.
211     */
212
213    for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
214	if (STR_EQ(tok, "EXCEPT"))		/* EXCEPT: give up */
215	    return (NO);
216	if (match_fn(tok, request)) {		/* YES: look for exceptions */
217	    while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
218		 /* VOID */ ;
219	    return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
220	}
221    }
222    return (NO);
223}
224
225/* server_match - match server information */
226
227static int server_match(tok, request)
228char   *tok;
229struct request_info *request;
230{
231    char   *host;
232
233    if ((host = split_at(tok + 1, '@')) == 0) {	/* plain daemon */
234	return (string_match(tok, eval_daemon(request)));
235    } else {					/* daemon@host */
236	return (string_match(tok, eval_daemon(request))
237		&& host_match(host, request->server));
238    }
239}
240
241/* client_match - match client information */
242
243static int client_match(tok, request)
244char   *tok;
245struct request_info *request;
246{
247    char   *host;
248
249    if ((host = split_at(tok + 1, '@')) == 0) {	/* plain host */
250	return (host_match(tok, request->client));
251    } else {					/* user@host */
252	return (host_match(host, request->client)
253		&& string_match(tok, eval_user(request)));
254    }
255}
256
257/* host_match - match host name and/or address against pattern */
258
259static int host_match(tok, host)
260char   *tok;
261struct host_info *host;
262{
263    char   *mask;
264
265    /*
266     * This code looks a little hairy because we want to avoid unnecessary
267     * hostname lookups.
268     *
269     * The KNOWN pattern requires that both address AND name be known; some
270     * patterns are specific to host names or to host addresses; all other
271     * patterns are satisfied when either the address OR the name match.
272     */
273
274    if (tok[0] == '@') {			/* netgroup: look it up */
275#ifdef  NETGROUP
276	static char *mydomain = 0;
277	if (mydomain == 0)
278	    yp_get_default_domain(&mydomain);
279	return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
280#else
281	tcpd_warn("netgroup support is disabled");	/* not tcpd_jump() */
282	return (NO);
283#endif
284    } else if (STR_EQ(tok, "KNOWN")) {		/* check address and name */
285	char   *name = eval_hostname(host);
286	return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
287    } else if (STR_EQ(tok, "LOCAL")) {		/* local: no dots in name */
288	char   *name = eval_hostname(host);
289	return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
290#ifdef HAVE_IPV6
291    } else if (tok[0] == '[') {			/* IPv6 address */
292	    struct in6_addr in6, hostin6, *hip;
293	    char *cbr;
294	    char *slash;
295	    int mask = IPV6_ABITS;
296
297	    /*
298	     * In some cases we don't get the sockaddr, only the addr.
299	     * We use inet_pton to convert it to its binary representation
300	     * and match against that.
301	     */
302	    if (host->sin == NULL) {
303		if (host->addr == NULL ||
304		    inet_pton(AF_INET6, host->addr, &hostin6) != 1) {
305		    return (NO);
306		}
307		hip = &hostin6;
308	    } else {
309		if (SGFAM(host->sin) != AF_INET6)
310		    return (NO);
311		hip = &host->sin->sg_sin6.sin6_addr;
312	    }
313
314	    if (cbr = strchr(tok, ']'))
315		*cbr = '\0';
316
317	    /*
318	     * A /nnn prefix specifies how many bits of the address we
319	     * need to check.
320	     */
321	    if (slash = strchr(tok, '/')) {
322		*slash = '\0';
323		mask = atoi(slash+1);
324		if (mask < 0 || mask > IPV6_ABITS) {
325		    tcpd_warn("bad IP6 prefix specification");
326		    return (NO);
327		}
328		/* Copy, because we need to modify it below */
329		if (host->sin != NULL) {
330		    hostin6 = host->sin->sg_sin6.sin6_addr;
331		    hip = &hostin6;
332		}
333	    }
334
335	    if (cbr == NULL || inet_pton(AF_INET6, tok+1, &in6) != 1) {
336		tcpd_warn("bad IP6 address specification");
337		return (NO);
338	    }
339	    /*
340	     * Zero the bits we're not interested in in both addresses
341	     * then compare.  Note that we take a copy of the host info
342	     * in that case.
343	     */
344	    if (mask != IPV6_ABITS) {
345		ipv6_mask(&in6, mask);
346		ipv6_mask(hip, mask);
347	    }
348	    if (memcmp(&in6, hip, sizeof(in6)) == 0)
349		return (YES);
350	    return (NO);
351#endif
352    } else if ((mask = split_at(tok, '/')) != 0) {	/* net/mask */
353	return (masked_match(tok, mask, eval_hostaddr(host)));
354    } else {					/* anything else */
355	return (string_match(tok, eval_hostaddr(host))
356	    || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
357    }
358}
359
360/* string_match - match string against pattern */
361
362static int string_match(tok, string)
363char   *tok;
364char   *string;
365{
366    int     n;
367
368    if (tok[0] == '.') {			/* suffix */
369	n = strlen(string) - strlen(tok);
370	return (n > 0 && STR_EQ(tok, string + n));
371    } else if (STR_EQ(tok, "ALL")) {		/* all: match any */
372	return (YES);
373    } else if (STR_EQ(tok, "KNOWN")) {		/* not unknown */
374	return (STR_NE(string, unknown));
375    } else if (tok[(n = strlen(tok)) - 1] == '.') {	/* prefix */
376	return (STRN_EQ(tok, string, n));
377    } else {					/* exact match */
378	return (STR_EQ(tok, string));
379    }
380}
381
382/* masked_match - match address against netnumber/netmask */
383
384static int masked_match(net_tok, mask_tok, string)
385char   *net_tok;
386char   *mask_tok;
387char   *string;
388{
389    unsigned long net;
390    unsigned long mask;
391    unsigned long addr;
392
393    /*
394     * Disallow forms other than dotted quad: the treatment that inet_addr()
395     * gives to forms with less than four components is inconsistent with the
396     * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
397     */
398
399    if ((addr = dot_quad_addr(string)) == INADDR_NONE)
400	return (NO);
401    if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
402	|| (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
403	tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
404	return (NO);				/* not tcpd_jump() */
405    }
406    return ((addr & mask) == net);
407}
408
409#ifdef HAVE_IPV6
410/*
411 * Function that zeros all but the first "maskbits" bits of the IPV6 address
412 * This function can be made generic by specifying an address length as
413 * extra parameter. (So Wietse can implement 1.2.3.4/16)
414 */
415static void ipv6_mask(in6p, maskbits)
416struct in6_addr *in6p;
417int maskbits;
418{
419    uchar_t *p = (uchar_t*) in6p;
420
421    if (maskbits < 0 || maskbits >= IPV6_ABITS)
422	return;
423
424    p += maskbits / 8;
425    maskbits %= 8;
426
427    if (maskbits != 0)
428	*p++ &= 0xff << (8 - maskbits);
429
430    while (p < (((uchar_t*) in6p)) + sizeof(*in6p))
431	*p++ = 0;
432}
433#endif
434