login_access.c revision 90145 
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#if 0
11#ifndef lint
12static char sccsid[] = "%Z% %M% %I% %E% %U%";
13#endif
14#endif
15
16#include <sys/cdefs.h>
17__FBSDID("$FreeBSD: head/lib/libpam/modules/pam_login_access/login_access.c 90145 2002-02-03 15:17:57Z markm $");
18
19#include <sys/types.h>
20#include <ctype.h>
21#include <errno.h>
22#include <grp.h>
23#include <stdio.h>
24#include <stdlib.h>
25#include <string.h>
26#include <syslog.h>
27#include <unistd.h>
28
29#include "pam_login_access.h"
30
31#define _PATH_LOGACCESS		"/etc/login.access"
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(const char *, const char *);
44static int	list_match(char *, const char *,
45				int (*)(const char *, const char *));
46static int	netgroup_match(const char *, const char *, const char *);
47static int	string_match(const char *, const char *);
48static int	user_match(const char *, const char *);
49
50/* login_access - match username/group and host/tty with access control file */
51
52int
53login_access(const char *user, const char *from)
54{
55    FILE   *fp;
56    char    line[BUFSIZ];
57    char   *perm;			/* becomes permission field */
58    char   *users;			/* becomes list of login names */
59    char   *froms;			/* becomes list of terminals or hosts */
60    int     match = NO;
61    int     end;
62    int     lineno = 0;			/* for diagnostics */
63
64    /*
65     * Process the table one line at a time and stop at the first match.
66     * Blank lines and lines that begin with a '#' character are ignored.
67     * Non-comment lines are broken at the ':' character. All fields are
68     * mandatory. The first field should be a "+" or "-" character. A
69     * non-existing table means no access control.
70     */
71
72    if ((fp = fopen(_PATH_LOGACCESS, "r")) != NULL) {
73	while (!match && fgets(line, sizeof(line), fp)) {
74	    lineno++;
75	    if (line[end = strlen(line) - 1] != '\n') {
76		syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
77		       _PATH_LOGACCESS, lineno);
78		continue;
79	    }
80	    if (line[0] == '#')
81		continue;			/* comment line */
82	    while (end > 0 && isspace(line[end - 1]))
83		end--;
84	    line[end] = 0;			/* strip trailing whitespace */
85	    if (line[0] == 0)			/* skip blank lines */
86		continue;
87	    if (!(perm = strtok(line, fs))
88		|| !(users = strtok((char *) 0, fs))
89		|| !(froms = strtok((char *) 0, fs))
90		|| strtok((char *) 0, fs)) {
91		syslog(LOG_ERR, "%s: line %d: bad field count", _PATH_LOGACCESS,
92		       lineno);
93		continue;
94	    }
95	    if (perm[0] != '+' && perm[0] != '-') {
96		syslog(LOG_ERR, "%s: line %d: bad first field", _PATH_LOGACCESS,
97		       lineno);
98		continue;
99	    }
100	    match = (list_match(froms, from, from_match)
101		     && list_match(users, user, user_match));
102	}
103	(void) fclose(fp);
104    } else if (errno != ENOENT) {
105	syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
106    }
107    return (match == 0 || (line[0] == '+'));
108}
109
110/* list_match - match an item against a list of tokens with exceptions */
111
112static int
113list_match(char *list, const char *item,
114    int (*match_fn)(const char *, const char *))
115{
116    char   *tok;
117    int     match = NO;
118
119    /*
120     * Process tokens one at a time. We have exhausted all possible matches
121     * when we reach an "EXCEPT" token or the end of the list. If we do find
122     * a match, look for an "EXCEPT" list and recurse to determine whether
123     * the match is affected by any exceptions.
124     */
125
126    for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
127	if (strcasecmp(tok, "EXCEPT") == 0)	/* EXCEPT: give up */
128	    break;
129	if ((match = (*match_fn)(tok, item)) != NULL)	/* YES */
130	    break;
131    }
132    /* Process exceptions to matches. */
133
134    if (match != NO) {
135	while ((tok = strtok((char *) 0, sep)) && strcasecmp(tok, "EXCEPT"))
136	     /* VOID */ ;
137	if (tok == 0 || list_match((char *) 0, item, match_fn) == NO)
138	    return (match);
139    }
140    return (NO);
141}
142
143/* netgroup_match - match group against machine or user */
144
145static int
146netgroup_match(const char *group __unused,
147    const char *machine __unused, const char *user __unused)
148{
149    syslog(LOG_ERR, "NIS netgroup support not configured");
150    return 0;
151}
152
153/* user_match - match a username against one token */
154
155static int
156user_match(const char *tok, const char *string)
157{
158    struct group *group;
159    int     i;
160
161    /*
162     * If a token has the magic value "ALL" the match always succeeds.
163     * Otherwise, return YES if the token fully matches the username, or if
164     * the token is a group that contains the username.
165     */
166
167    if (tok[0] == '@') {			/* netgroup */
168	return (netgroup_match(tok + 1, (char *) 0, string));
169    } else if (string_match(tok, string)) {	/* ALL or exact match */
170	return (YES);
171    } else if ((group = getgrnam(tok)) != NULL) {/* try group membership */
172	for (i = 0; group->gr_mem[i]; i++)
173	    if (strcasecmp(string, group->gr_mem[i]) == 0)
174		return (YES);
175    }
176    return (NO);
177}
178
179/* from_match - match a host or tty against a list of tokens */
180
181static int
182from_match(const char *tok, const char *string)
183{
184    int     tok_len;
185    int     str_len;
186
187    /*
188     * If a token has the magic value "ALL" the match always succeeds. Return
189     * YES if the token fully matches the string. If the token is a domain
190     * name, return YES if it matches the last fields of the string. If the
191     * token has the magic value "LOCAL", return YES if the string does not
192     * contain a "." character. If the token is a network number, return YES
193     * if it matches the head of the string.
194     */
195
196    if (tok[0] == '@') {			/* netgroup */
197	return (netgroup_match(tok + 1, string, (char *) 0));
198    } else if (string_match(tok, string)) {	/* ALL or exact match */
199	return (YES);
200    } else if (tok[0] == '.') {			/* domain: match last fields */
201	if ((str_len = strlen(string)) > (tok_len = strlen(tok))
202	    && strcasecmp(tok, string + str_len - tok_len) == 0)
203	    return (YES);
204    } else if (strcasecmp(tok, "LOCAL") == 0) {	/* local: no dots */
205	if (strchr(string, '.') == 0)
206	    return (YES);
207    } else if (tok[(tok_len = strlen(tok)) - 1] == '.'	/* network */
208	       && strncmp(tok, string, tok_len) == 0) {
209	return (YES);
210    }
211    return (NO);
212}
213
214/* string_match - match a string against one token */
215
216static int
217string_match(const char *tok, const char *string)
218{
219
220    /*
221     * If the token has the magic value "ALL" the match always succeeds.
222     * Otherwise, return YES if the token fully matches the string.
223     */
224
225    if (strcasecmp(tok, "ALL") == 0) {		/* all: always matches */
226	return (YES);
227    } else if (strcasecmp(tok, string) == 0) {	/* try exact match */
228	return (YES);
229    }
230    return (NO);
231}
232