login_access.c revision 89994 
1 /*
2  * This module implements a simple but effective form of login access
3  * control based on login names and on host (or domain) names, internet
4  * addresses (or network numbers), or on terminal line names in case of
5  * non-networked logins. Diagnostics are reported through syslog(3).
6  *
7  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
8  */
9
10#ifdef LOGIN_ACCESS
11#if 0
12#ifndef lint
13static char sccsid[] = "%Z% %M% %I% %E% %U%";
14#endif
15#endif
16
17#include <sys/cdefs.h>
18__FBSDID("$FreeBSD: head/lib/libpam/modules/pam_login_access/login_access.c 89994 2002-01-30 19:10:21Z des $");
19
20#include <sys/types.h>
21#include <ctype.h>
22#include <errno.h>
23#include <grp.h>
24#include <stdio.h>
25#include <stdlib.h>
26#include <string.h>
27#include <syslog.h>
28#include <unistd.h>
29
30#include "login.h"
31#include "pathnames.h"
32
33 /* Delimiters for fields and for lists of users, ttys or hosts. */
34
35static char fs[] = ":";			/* field separator */
36static char sep[] = ", \t";		/* list-element separator */
37
38 /* Constants to be used in assignments only, not in comparisons... */
39
40#define YES             1
41#define NO              0
42
43static int	from_match __P((const char *, const char *));
44static int	list_match __P((char *, const char *,
45				int (*)(const char *, const char *)));
46static int	netgroup_match __P((const char *, const char *, const char *));
47static int	string_match __P((const char *, const char *));
48static int	user_match __P((const char *, const char *));
49
50/* login_access - match username/group and host/tty with access control file */
51
52int
53login_access(user, from)
54const char   *user;
55const char   *from;
56{
57    FILE   *fp;
58    char    line[BUFSIZ];
59    char   *perm;			/* becomes permission field */
60    char   *users;			/* becomes list of login names */
61    char   *froms;			/* becomes list of terminals or hosts */
62    int     match = NO;
63    int     end;
64    int     lineno = 0;			/* for diagnostics */
65
66    /*
67     * Process the table one line at a time and stop at the first match.
68     * Blank lines and lines that begin with a '#' character are ignored.
69     * Non-comment lines are broken at the ':' character. All fields are
70     * mandatory. The first field should be a "+" or "-" character. A
71     * non-existing table means no access control.
72     */
73
74    if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) {
75	while (!match && fgets(line, sizeof(line), fp)) {
76	    lineno++;
77	    if (line[end = strlen(line) - 1] != '\n') {
78		syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
79		       _PATH_LOGACCESS, lineno);
80		continue;
81	    }
82	    if (line[0] == '#')
83		continue;			/* comment line */
84	    while (end > 0 && isspace(line[end - 1]))
85		end--;
86	    line[end] = 0;			/* strip trailing whitespace */
87	    if (line[0] == 0)			/* skip blank lines */
88		continue;
89	    if (!(perm = strtok(line, fs))
90		|| !(users = strtok((char *) 0, fs))
91		|| !(froms = strtok((char *) 0, fs))
92		|| strtok((char *) 0, fs)) {
93		syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS,
94		       lineno);
95		continue;
96	    }
97	    if (perm[0] != '+' && perm[0] != '-') {
98		syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS,
99		       lineno);
100		continue;
101	    }
102	    match = (list_match(froms, from, from_match)
103		     && list_match(users, user, user_match));
104	}
105	(void) fclose(fp);
106    } else if (errno != ENOENT) {
107	syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
108    }
109    return (match == 0 || (line[0] == '+'));
110}
111
112/* list_match - match an item against a list of tokens with exceptions */
113
114static int list_match(list, item, match_fn)
115char         *list;
116const char   *item;
117int         (*match_fn) __P((const char *, const char *));
118{
119    char   *tok;
120    int     match = NO;
121
122    /*
123     * Process tokens one at a time. We have exhausted all possible matches
124     * when we reach an "EXCEPT" token or the end of the list. If we do find
125     * a match, look for an "EXCEPT" list and recurse to determine whether
126     * the match is affected by any exceptions.
127     */
128
129    for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
130	if (strcasecmp(tok, "EXCEPT") == 0)	/* EXCEPT: give up */
131	    break;
132	if ((match = (*match_fn)(tok, item)) != NULL)	/* YES */
133	    break;
134    }
135    /* Process exceptions to matches. */
136
137    if (match != NO) {
138	while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT"))
139	     /* VOID */ ;
140	if (tok == 0 || list_match((char *) 0, item, match_fn) == NO)
141	    return (match);
142    }
143    return (NO);
144}
145
146/* netgroup_match - match group against machine or user */
147
148static int netgroup_match(group, machine, user)
149const char   *group __unused;
150const char   *machine __unused;
151const char   *user __unused;
152{
153    syslog(LOG_ERR, "NIS netgroup support not configured");
154    return 0;
155}
156
157/* user_match - match a username against one token */
158
159static int user_match(tok, string)
160const char   *tok;
161const char   *string;
162{
163    struct group *group;
164    int     i;
165
166    /*
167     * If a token has the magic value "ALL" the match always succeeds.
168     * Otherwise, return YES if the token fully matches the username, or if
169     * the token is a group that contains the username.
170     */
171
172    if (tok[0] == '@') {			/* netgroup */
173	return (netgroup_match(tok + 1, (char *) 0, string));
174    } else if (string_match(tok, string)) {	/* ALL or exact match */
175	return (YES);
176    } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */
177	for (i = 0; group->gr_mem[i]; i++)
178	    if (strcasecmp(string, group->gr_mem[i]) == 0)
179		return (YES);
180    }
181    return (NO);
182}
183
184/* from_match - match a host or tty against a list of tokens */
185
186static int from_match(tok, string)
187const char   *tok;
188const char   *string;
189{
190    int     tok_len;
191    int     str_len;
192
193    /*
194     * If a token has the magic value "ALL" the match always succeeds. Return
195     * YES if the token fully matches the string. If the token is a domain
196     * name, return YES if it matches the last fields of the string. If the
197     * token has the magic value "LOCAL", return YES if the string does not
198     * contain a "." character. If the token is a network number, return YES
199     * if it matches the head of the string.
200     */
201
202    if (tok[0] == '@') {			/* netgroup */
203	return (netgroup_match(tok + 1, string, (char *) 0));
204    } else if (string_match(tok, string)) {	/* ALL or exact match */
205	return (YES);
206    } else if (tok[0] == '.') {			/* domain: match last fields */
207	if ((str_len = strlen(string)) > (tok_len = strlen(tok))
208	    && strcasecmp(tok, string + str_len - tok_len) == 0)
209	    return (YES);
210    } else if (strcasecmp(tok, "LOCAL") == 0) {	/* local: no dots */
211	if (strchr(string, '.') == 0)
212	    return (YES);
213    } else if (tok[(tok_len = strlen(tok)) - 1] == '.'	/* network */
214	       && strncmp(tok, string, tok_len) == 0) {
215	return (YES);
216    }
217    return (NO);
218}
219
220/* string_match - match a string against one token */
221
222static int string_match(tok, string)
223const char   *tok;
224const char   *string;
225{
226
227    /*
228     * If the token has the magic value "ALL" the match always succeeds.
229     * Otherwise, return YES if the token fully matches the string.
230     */
231
232    if (strcasecmp(tok, "ALL") == 0) {		/* all: always matches */
233	return (YES);
234    } else if (strcasecmp(tok, string) == 0) {	/* try exact match */
235	return (YES);
236    }
237    return (NO);
238}
239#endif /* LOGIN_ACCES */
240