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
12 static char sccsid[] = "%Z% %M% %I% %E% %U%";
13 #endif
14 #endif
15
16 #include <sys/cdefs.h>
17 __FBSDID("$FreeBSD$");
18
19 #include <sys/types.h>
20 #include <sys/param.h>
21 #include <ctype.h>
22 #include <errno.h>
23 #include <grp.h>
24 #include <netdb.h>
25 #include <pwd.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <syslog.h>
30 #include <unistd.h>
31
32 #include "pam_login_access.h"
33
34 /* Constants to be used in assignments only, not in comparisons... */
35
36 #define YES 1
37 #define NO 0
38
39 static int from_match(const char *, const char *, struct pam_login_access_options *);
40 static int list_match(char *, const char *,
41 int (*)(const char *, const char *,
42 struct pam_login_access_options *),
43 struct pam_login_access_options *);
44 static int netgroup_match(const char *, const char *, const char *);
45 static int string_match(const char *, const char *);
46 static int user_match(const char *, const char *, struct pam_login_access_options *);
47 static int group_match(const char *, const char *);
48
49 /* login_access - match username/group and host/tty with access control file */
50
51 int
login_access(const char * user,const char * from,struct pam_login_access_options * login_access_opts)52 login_access(const char *user, const char *from,
53 struct pam_login_access_options *login_access_opts)
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 const char *fieldsep = login_access_opts->fieldsep;
64
65 /*
66 * Process the table one line at a time and stop at the first match.
67 * Blank lines and lines that begin with a '#' character are ignored.
68 * Non-comment lines are broken at the ':' character. All fields are
69 * mandatory. The first field should be a "+" or "-" character. A
70 * non-existing table means no access control.
71 */
72
73 if ((fp = fopen(login_access_opts->accessfile, "r")) != NULL) {
74 while (!match && fgets(line, sizeof(line), fp)) {
75 lineno++;
76 if (line[end = strlen(line) - 1] != '\n') {
77 syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
78 login_access_opts->accessfile, lineno);
79 continue;
80 }
81 if (line[0] == '#')
82 continue; /* comment line */
83 while (end > 0 && isspace(line[end - 1]))
84 end--;
85 line[end] = 0; /* strip trailing whitespace */
86 if (line[0] == 0) /* skip blank lines */
87 continue;
88 if (!(perm = strtok(line, fieldsep))
89 || !(users = strtok((char *) 0, fieldsep))
90 || !(froms = strtok((char *) 0, fieldsep))
91 || strtok((char *) 0, fieldsep)) {
92 syslog(LOG_ERR, "%s: line %d: bad field count", login_access_opts->accessfile,
93 lineno);
94 continue;
95 }
96 if (perm[0] != '+' && perm[0] != '-') {
97 syslog(LOG_ERR, "%s: line %d: bad first field", login_access_opts->accessfile,
98 lineno);
99 continue;
100 }
101 match = (list_match(froms, from, from_match, login_access_opts)
102 && list_match(users, user, user_match, login_access_opts));
103 }
104 (void) fclose(fp);
105 } else if (errno != ENOENT) {
106 syslog(LOG_ERR, "cannot open %s: %m", login_access_opts->accessfile);
107 }
108 return (match == 0 || (line[0] == '+'));
109 }
110
111 /* list_match - match an item against a list of tokens with exceptions */
112
113 static int
list_match(char * list,const char * item,int (* match_fn)(const char *,const char *,struct pam_login_access_options *),struct pam_login_access_options * login_access_opts)114 list_match(char *list, const char *item,
115 int (*match_fn)(const char *, const char *, struct pam_login_access_options *),
116 struct pam_login_access_options *login_access_opts)
117 {
118 char *tok;
119 int match = NO;
120 const char *listsep = login_access_opts->listsep;
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, listsep); tok != NULL; tok = strtok((char *) 0, listsep)) {
130 if (strcmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */
131 break;
132 if ((match = (*match_fn)(tok, item, login_access_opts)) != 0) /* YES */
133 break;
134 }
135 /* Process exceptions to matches. */
136
137 if (match != NO) {
138 while ((tok = strtok((char *) 0, listsep)) && strcmp(tok, "EXCEPT")) {
139 /* VOID */ ;
140 }
141 if (tok == NULL ||
142 list_match((char *) 0, item, match_fn, login_access_opts) == NO) {
143 return (match);
144 }
145 }
146 return (NO);
147 }
148
149 /* netgroup_match - match group against machine or user */
150
151 static int
netgroup_match(const char * group,const char * machine,const char * user)152 netgroup_match(const char *group, const char *machine, const char *user)
153 {
154 char domain[1024];
155 unsigned int i;
156
157 if (getdomainname(domain, sizeof(domain)) != 0 || *domain == '\0') {
158 syslog(LOG_ERR, "NIS netgroup support disabled: no NIS domain");
159 return (NO);
160 }
161
162 /* getdomainname() does not reliably terminate the string */
163 for (i = 0; i < sizeof(domain); ++i)
164 if (domain[i] == '\0')
165 break;
166 if (i == sizeof(domain)) {
167 syslog(LOG_ERR, "NIS netgroup support disabled: invalid NIS domain");
168 return (NO);
169 }
170
171 if (innetgr(group, machine, user, domain) == 1)
172 return (YES);
173 return (NO);
174 }
175
176 /* group_match - match a group against one token */
177
178 int
group_match(const char * tok,const char * username)179 group_match(const char *tok, const char *username)
180 {
181 struct group *group;
182 struct passwd *passwd;
183 gid_t *grouplist;
184 int i, ret, ngroups = NGROUPS;
185
186 if ((passwd = getpwnam(username)) == NULL)
187 return (NO);
188 errno = 0;
189 if ((group = getgrnam(tok)) == NULL) {
190 if (errno != 0)
191 syslog(LOG_ERR, "getgrnam() failed for %s: %s", username, strerror(errno));
192 else
193 syslog(LOG_NOTICE, "group not found: %s", username);
194 return (NO);
195 }
196 if ((grouplist = calloc(ngroups, sizeof(gid_t))) == NULL) {
197 syslog(LOG_ERR, "cannot allocate memory for grouplist: %s", username);
198 return (NO);
199 }
200 ret = NO;
201 if (getgrouplist(username, passwd->pw_gid, grouplist, &ngroups) != 0)
202 syslog(LOG_ERR, "getgrouplist() failed for %s", username);
203 for (i = 0; i < ngroups; i++)
204 if (grouplist[i] == group->gr_gid)
205 ret = YES;
206 free(grouplist);
207 return (ret);
208 }
209
210 /* user_match - match a username against one token */
211
212 static int
user_match(const char * tok,const char * string,struct pam_login_access_options * login_access_opts)213 user_match(const char *tok, const char *string,
214 struct pam_login_access_options *login_access_opts)
215 {
216 size_t stringlen;
217 char *grpstr;
218 int rc;
219
220 /*
221 * If a token has the magic value "ALL" the match always succeeds.
222 * Otherwise, return YES if the token fully matches the username, or if
223 * the token is a group that contains the username.
224 */
225
226 if (tok[0] == '@') { /* netgroup */
227 return (netgroup_match(tok + 1, (char *) 0, string));
228 } else if (tok[0] == '(' && tok[(stringlen = strlen(&tok[1]))] == ')') { /* group */
229 if ((grpstr = strndup(&tok[1], stringlen - 1)) == NULL) {
230 syslog(LOG_ERR, "cannot allocate memory for %s", string);
231 return (NO);
232 }
233 rc = group_match(grpstr, string);
234 free(grpstr);
235 return (rc);
236 } else if (string_match(tok, string)) { /* ALL or exact match */
237 return (YES);
238 } else if (login_access_opts->defgroup == true) {/* try group membership */
239 return (group_match(tok, string));
240 }
241 return (NO);
242 }
243
244 /* from_match - match a host or tty against a list of tokens */
245
246 static int
from_match(const char * tok,const char * string,struct pam_login_access_options * login_access_opts __unused)247 from_match(const char *tok, const char *string,
248 struct pam_login_access_options *login_access_opts __unused)
249 {
250 int tok_len;
251 int str_len;
252
253 /*
254 * If a token has the magic value "ALL" the match always succeeds. Return
255 * YES if the token fully matches the string. If the token is a domain
256 * name, return YES if it matches the last fields of the string. If the
257 * token has the magic value "LOCAL", return YES if the string does not
258 * contain a "." character. If the token is a network number, return YES
259 * if it matches the head of the string.
260 */
261
262 if (tok[0] == '@') { /* netgroup */
263 return (netgroup_match(tok + 1, string, (char *) 0));
264 } else if (string_match(tok, string)) { /* ALL or exact match */
265 return (YES);
266 } else if (tok[0] == '.') { /* domain: match last fields */
267 if ((str_len = strlen(string)) > (tok_len = strlen(tok))
268 && strcasecmp(tok, string + str_len - tok_len) == 0)
269 return (YES);
270 } else if (strcmp(tok, "LOCAL") == 0) { /* local: no dots */
271 if (strchr(string, '.') == NULL)
272 return (YES);
273 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */
274 && strncmp(tok, string, tok_len) == 0) {
275 return (YES);
276 }
277 return (NO);
278 }
279
280 /* string_match - match a string against one token */
281
282 static int
string_match(const char * tok,const char * string)283 string_match(const char *tok, const char *string)
284 {
285
286 /*
287 * If the token has the magic value "ALL" the match always succeeds.
288 * Otherwise, return YES if the token fully matches the string.
289 */
290
291 if (strcmp(tok, "ALL") == 0) { /* all: always matches */
292 return (YES);
293 } else if (strcasecmp(tok, string) == 0) { /* try exact match */
294 return (YES);
295 }
296 return (NO);
297 }
298