1/************************************************************************
2* Copyright 1995 by Wietse Venema.  All rights reserved.  Some individual
3* files may be covered by other copyrights.
4*
5* This material was originally written and compiled by Wietse Venema at
6* Eindhoven University of Technology, The Netherlands, in 1990, 1991,
7* 1992, 1993, 1994 and 1995.
8*
9* Redistribution and use in source and binary forms, with or without
10* modification, are permitted provided that this entire copyright notice
11* is duplicated in all such copies.
12*
13* This software is provided "as is" and without any expressed or implied
14* warranties, including, without limitation, the implied warranties of
15* merchantibility and fitness for any particular purpose.
16************************************************************************/
17 /*
18  * This module implements a simple but effective form of login access
19  * control based on login names and on host (or domain) names, internet
20  * addresses (or network numbers), or on terminal line names in case of
21  * non-networked logins. Diagnostics are reported through syslog(3).
22  *
23  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
24  */
25
26#include "login_locl.h"
27
28RCSID("$Id$");
29
30 /* Delimiters for fields and for lists of users, ttys or hosts. */
31
32static char fs[] = ":";			/* field separator */
33static char sep[] = ", \t";		/* list-element separator */
34
35 /* Constants to be used in assignments only, not in comparisons... */
36
37#define YES             1
38#define NO              0
39
40 /*
41  * A structure to bundle up all login-related information to keep the
42  * functional interfaces as generic as possible.
43  */
44struct login_info {
45    struct passwd *user;
46    char   *from;
47};
48
49static int list_match(char *list, struct login_info *item,
50		      int (*match_fn)(char *, struct login_info *));
51static int user_match(char *tok, struct login_info *item);
52static int from_match(char *tok, struct login_info *item);
53static int string_match(char *tok, char *string);
54
55/* login_access - match username/group and host/tty with access control file */
56
57int login_access(struct passwd *user, char *from)
58{
59    struct login_info item;
60    FILE   *fp;
61    char    line[BUFSIZ];
62    char   *perm;			/* becomes permission field */
63    char   *users;			/* becomes list of login names */
64    char   *froms;			/* becomes list of terminals or hosts */
65    int     match = NO;
66    int     end;
67    int     lineno = 0;			/* for diagnostics */
68    char   *foo;
69
70    /*
71     * Bundle up the arguments to avoid unnecessary clumsiness lateron.
72     */
73    item.user = user;
74    item.from = from;
75
76    /*
77     * Process the table one line at a time and stop at the first match.
78     * Blank lines and lines that begin with a '#' character are ignored.
79     * Non-comment lines are broken at the ':' character. All fields are
80     * mandatory. The first field should be a "+" or "-" character. A
81     * non-existing table means no access control.
82     */
83
84    if ((fp = fopen(_PATH_LOGACCESS, "r")) != 0) {
85	while (!match && fgets(line, sizeof(line), fp)) {
86	    lineno++;
87	    if (line[end = strlen(line) - 1] != '\n') {
88		syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
89		       _PATH_LOGACCESS, lineno);
90		continue;
91	    }
92	    if (line[0] == '#')
93		continue;			/* comment line */
94	    while (end > 0 && isspace((unsigned char)line[end - 1]))
95		end--;
96	    line[end] = 0;			/* strip trailing whitespace */
97	    if (line[0] == 0)			/* skip blank lines */
98		continue;
99	    foo = NULL;
100	    if (!(perm = strtok_r(line, fs, &foo))
101		|| !(users = strtok_r(NULL, fs, &foo))
102		|| !(froms = strtok_r(NULL, fs, &foo))
103		|| strtok_r(NULL, fs, &foo)) {
104		syslog(LOG_ERR, "%s: line %d: bad field count",
105		       _PATH_LOGACCESS,
106		       lineno);
107		continue;
108	    }
109	    if (perm[0] != '+' && perm[0] != '-') {
110		syslog(LOG_ERR, "%s: line %d: bad first field",
111		       _PATH_LOGACCESS,
112		       lineno);
113		continue;
114	    }
115	    match = (list_match(froms, &item, from_match)
116		     && list_match(users, &item, user_match));
117	}
118	fclose(fp);
119    } else if (errno != ENOENT) {
120	syslog(LOG_ERR, "cannot open %s: %m", _PATH_LOGACCESS);
121    }
122    return (match == 0 || (line[0] == '+'));
123}
124
125/* list_match - match an item against a list of tokens with exceptions */
126
127static int
128list_match(char *list,
129	   struct login_info *item,
130	   int (*match_fn)(char *, struct login_info *))
131{
132    char   *tok;
133    int     match = NO;
134    char   *foo = NULL;
135
136    /*
137     * Process tokens one at a time. We have exhausted all possible matches
138     * when we reach an "EXCEPT" token or the end of the list. If we do find
139     * a match, look for an "EXCEPT" list and recurse to determine whether
140     * the match is affected by any exceptions.
141     */
142
143    for (tok = strtok_r(list, sep, &foo);
144	 tok != NULL;
145	 tok = strtok_r(NULL, sep, &foo)) {
146	if (strcasecmp(tok, "EXCEPT") == 0)	/* EXCEPT: give up */
147	    break;
148	if ((match = (*match_fn) (tok, item)) != 0)	/* YES */
149	    break;
150    }
151    /* Process exceptions to matches. */
152
153    if (match != NO) {
154	while ((tok = strtok_r(NULL, sep, &foo)) && strcasecmp(tok, "EXCEPT"))
155	     /* VOID */ ;
156	if (tok == 0 || list_match(NULL, item, match_fn) == NO)
157	    return (match);
158    }
159    return (NO);
160}
161
162/* myhostname - figure out local machine name */
163
164static char *myhostname(void)
165{
166    static char name[MAXHOSTNAMELEN + 1] = "";
167
168    if (name[0] == 0) {
169	gethostname(name, sizeof(name));
170	name[MAXHOSTNAMELEN] = 0;
171    }
172    return (name);
173}
174
175/* netgroup_match - match group against machine or user */
176
177static int netgroup_match(char *group, char *machine, char *user)
178{
179#ifdef HAVE_YP_GET_DEFAULT_DOMAIN
180    static char *mydomain = 0;
181
182    if (mydomain == 0)
183	yp_get_default_domain(&mydomain);
184    return (innetgr(group, machine, user, mydomain));
185#else
186    syslog(LOG_ERR, "NIS netgroup support not configured");
187    return 0;
188#endif
189}
190
191/* user_match - match a username against one token */
192
193static int user_match(char *tok, struct login_info *item)
194{
195    char   *string = item->user->pw_name;
196    struct login_info fake_item;
197    struct group *group;
198    int     i;
199    char   *at;
200
201    /*
202     * If a token has the magic value "ALL" the match always succeeds.
203     * Otherwise, return YES if the token fully matches the username, if the
204     * token is a group that contains the username, or if the token is the
205     * name of the user's primary group.
206     */
207
208    if ((at = strchr(tok + 1, '@')) != 0) {	/* split user@host pattern */
209	*at = 0;
210	fake_item.from = myhostname();
211	return (user_match(tok, item) && from_match(at + 1, &fake_item));
212    } else if (tok[0] == '@') {			/* netgroup */
213	return (netgroup_match(tok + 1, (char *) 0, string));
214    } else if (string_match(tok, string)) {	/* ALL or exact match */
215	return (YES);
216    } else if ((group = getgrnam(tok)) != 0) { /* try group membership */
217	if (item->user->pw_gid == group->gr_gid)
218	    return (YES);
219	for (i = 0; group->gr_mem[i]; i++)
220	    if (strcasecmp(string, group->gr_mem[i]) == 0)
221		return (YES);
222    }
223    return (NO);
224}
225
226/* from_match - match a host or tty against a list of tokens */
227
228static int from_match(char *tok, struct login_info *item)
229{
230    char   *string = item->from;
231    int     tok_len;
232    int     str_len;
233
234    /*
235     * If a token has the magic value "ALL" the match always succeeds. Return
236     * YES if the token fully matches the string. If the token is a domain
237     * name, return YES if it matches the last fields of the string. If the
238     * token has the magic value "LOCAL", return YES if the string does not
239     * contain a "." character. If the token is a network number, return YES
240     * if it matches the head of the string.
241     */
242
243    if (tok[0] == '@') {			/* netgroup */
244	return (netgroup_match(tok + 1, string, (char *) 0));
245    } else if (string_match(tok, string)) {	/* ALL or exact match */
246	return (YES);
247    } else if (tok[0] == '.') {			/* domain: match last fields */
248	if ((str_len = strlen(string)) > (tok_len = strlen(tok))
249	    && strcasecmp(tok, string + str_len - tok_len) == 0)
250	    return (YES);
251    } else if (strcasecmp(tok, "LOCAL") == 0) {	/* local: no dots */
252	if (strchr(string, '.') == 0)
253	    return (YES);
254    } else if (tok[(tok_len = strlen(tok)) - 1] == '.'	/* network */
255	       && strncmp(tok, string, tok_len) == 0) {
256	return (YES);
257    }
258    return (NO);
259}
260
261/* string_match - match a string against one token */
262
263static int string_match(char *tok, char *string)
264{
265
266    /*
267     * If the token has the magic value "ALL" the match always succeeds.
268     * Otherwise, return YES if the token fully matches the string.
269     */
270
271    if (strcasecmp(tok, "ALL") == 0) {		/* all: always matches */
272	return (YES);
273    } else if (strcasecmp(tok, string) == 0) {	/* try exact match */
274	return (YES);
275    }
276    return (NO);
277}
278