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/types.h>
17 #include <sys/param.h>
18 #include <ctype.h>
19 #include <errno.h>
20 #include <grp.h>
21 #include <netdb.h>
22 #include <pwd.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 /* Constants to be used in assignments only, not in comparisons... */
32
33 #define YES 1
34 #define NO 0
35
36 static int from_match(const char *, const char *, struct pam_login_access_options *);
37 static int list_match(char *, const char *,
38 int (*)(const char *, const char *,
39 struct pam_login_access_options *),
40 struct pam_login_access_options *);
41 static int netgroup_match(const char *, const char *, const char *);
42 static int string_match(const char *, const char *);
43 static int user_match(const char *, const char *, struct pam_login_access_options *);
44 static int group_match(const char *, const char *);
45
46 /* login_access - match username/group and host/tty with access control file */
47
48 int
login_access(const char * user,const char * from,struct pam_login_access_options * login_access_opts)49 login_access(const char *user, const char *from,
50 struct pam_login_access_options *login_access_opts)
51 {
52 FILE *fp;
53 char line[BUFSIZ];
54 char *perm; /* becomes permission field */
55 char *users; /* becomes list of login names */
56 char *froms; /* becomes list of terminals or hosts */
57 int match = NO;
58 int end;
59 int lineno = 0; /* for diagnostics */
60 const char *fieldsep = login_access_opts->fieldsep;
61
62 /*
63 * Process the table one line at a time and stop at the first match.
64 * Blank lines and lines that begin with a '#' character are ignored.
65 * Non-comment lines are broken at the ':' character. All fields are
66 * mandatory. The first field should be a "+" or "-" character. A
67 * non-existing table means no access control.
68 */
69
70 if ((fp = fopen(login_access_opts->accessfile, "r")) != NULL) {
71 while (!match && fgets(line, sizeof(line), fp)) {
72 lineno++;
73 if (line[end = strlen(line) - 1] != '\n') {
74 syslog(LOG_ERR, "%s: line %d: missing newline or line too long",
75 login_access_opts->accessfile, lineno);
76 continue;
77 }
78 if (line[0] == '#')
79 continue; /* comment line */
80 while (end > 0 && isspace(line[end - 1]))
81 end--;
82 line[end] = 0; /* strip trailing whitespace */
83 if (line[0] == 0) /* skip blank lines */
84 continue;
85 if (!(perm = strtok(line, fieldsep))
86 || !(users = strtok((char *) 0, fieldsep))
87 || !(froms = strtok((char *) 0, fieldsep))
88 || strtok((char *) 0, fieldsep)) {
89 syslog(LOG_ERR, "%s: line %d: bad field count", login_access_opts->accessfile,
90 lineno);
91 continue;
92 }
93 if (perm[0] != '+' && perm[0] != '-') {
94 syslog(LOG_ERR, "%s: line %d: bad first field", login_access_opts->accessfile,
95 lineno);
96 continue;
97 }
98 match = (list_match(froms, from, from_match, login_access_opts)
99 && list_match(users, user, user_match, login_access_opts));
100 }
101 (void) fclose(fp);
102 } else if (errno != ENOENT) {
103 syslog(LOG_ERR, "cannot open %s: %m", login_access_opts->accessfile);
104 }
105 return (match == 0 || (line[0] == '+'));
106 }
107
108 /* list_match - match an item against a list of tokens with exceptions */
109
110 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)111 list_match(char *list, const char *item,
112 int (*match_fn)(const char *, const char *, struct pam_login_access_options *),
113 struct pam_login_access_options *login_access_opts)
114 {
115 char *tok;
116 int match = NO;
117 const char *listsep = login_access_opts->listsep;
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, listsep); tok != NULL; tok = strtok((char *) 0, listsep)) {
127 if (strcmp(tok, "EXCEPT") == 0) /* EXCEPT: give up */
128 break;
129 if ((match = (*match_fn)(tok, item, login_access_opts)) != 0) /* YES */
130 break;
131 }
132 /* Process exceptions to matches. */
133
134 if (match != NO) {
135 while ((tok = strtok((char *) 0, listsep)) && strcmp(tok, "EXCEPT")) {
136 /* VOID */ ;
137 }
138 if (tok == NULL ||
139 list_match((char *) 0, item, match_fn, login_access_opts) == NO) {
140 return (match);
141 }
142 }
143 return (NO);
144 }
145
146 /* netgroup_match - match group against machine or user */
147
148 static int
netgroup_match(const char * group,const char * machine,const char * user)149 netgroup_match(const char *group, const char *machine, const char *user)
150 {
151 char domain[1024];
152 unsigned int i;
153
154 if (getdomainname(domain, sizeof(domain)) != 0 || *domain == '\0') {
155 syslog(LOG_ERR, "NIS netgroup support disabled: no NIS domain");
156 return (NO);
157 }
158
159 /* getdomainname() does not reliably terminate the string */
160 for (i = 0; i < sizeof(domain); ++i)
161 if (domain[i] == '\0')
162 break;
163 if (i == sizeof(domain)) {
164 syslog(LOG_ERR, "NIS netgroup support disabled: invalid NIS domain");
165 return (NO);
166 }
167
168 if (innetgr(group, machine, user, domain) == 1)
169 return (YES);
170 return (NO);
171 }
172
173 /* group_match - match a group against one token */
174
175 int
group_match(const char * tok,const char * username)176 group_match(const char *tok, const char *username)
177 {
178 struct group *group;
179 struct passwd *passwd;
180 gid_t *grouplist;
181 int i, ret, ngroups = NGROUPS;
182
183 if ((passwd = getpwnam(username)) == NULL)
184 return (NO);
185 errno = 0;
186 if ((group = getgrnam(tok)) == NULL) {
187 if (errno != 0)
188 syslog(LOG_ERR, "getgrnam() failed for %s: %s", username, strerror(errno));
189 else
190 syslog(LOG_NOTICE, "group not found: %s", username);
191 return (NO);
192 }
193 if ((grouplist = calloc(ngroups, sizeof(gid_t))) == NULL) {
194 syslog(LOG_ERR, "cannot allocate memory for grouplist: %s", username);
195 return (NO);
196 }
197 ret = NO;
198 if (getgrouplist(username, passwd->pw_gid, grouplist, &ngroups) != 0)
199 syslog(LOG_ERR, "getgrouplist() failed for %s", username);
200 for (i = 0; i < ngroups; i++)
201 if (grouplist[i] == group->gr_gid)
202 ret = YES;
203 free(grouplist);
204 return (ret);
205 }
206
207 /* user_match - match a username against one token */
208
209 static int
user_match(const char * tok,const char * string,struct pam_login_access_options * login_access_opts)210 user_match(const char *tok, const char *string,
211 struct pam_login_access_options *login_access_opts)
212 {
213 size_t stringlen;
214 char *grpstr;
215 int rc;
216
217 /*
218 * If a token has the magic value "ALL" the match always succeeds.
219 * Otherwise, return YES if the token fully matches the username, or if
220 * the token is a group that contains the username.
221 */
222
223 if (tok[0] == '@') { /* netgroup */
224 return (netgroup_match(tok + 1, (char *) 0, string));
225 } else if (tok[0] == '(' && tok[(stringlen = strlen(&tok[1]))] == ')') { /* group */
226 if ((grpstr = strndup(&tok[1], stringlen - 1)) == NULL) {
227 syslog(LOG_ERR, "cannot allocate memory for %s", string);
228 return (NO);
229 }
230 rc = group_match(grpstr, string);
231 free(grpstr);
232 return (rc);
233 } else if (string_match(tok, string)) { /* ALL or exact match */
234 return (YES);
235 } else if (login_access_opts->defgroup == true) {/* try group membership */
236 return (group_match(tok, string));
237 }
238 return (NO);
239 }
240
241 /* from_match - match a host or tty against a list of tokens */
242
243 static int
from_match(const char * tok,const char * string,struct pam_login_access_options * login_access_opts __unused)244 from_match(const char *tok, const char *string,
245 struct pam_login_access_options *login_access_opts __unused)
246 {
247 int tok_len;
248 int str_len;
249
250 /*
251 * If a token has the magic value "ALL" the match always succeeds. Return
252 * YES if the token fully matches the string. If the token is a domain
253 * name, return YES if it matches the last fields of the string. If the
254 * token has the magic value "LOCAL", return YES if the string does not
255 * contain a "." character. If the token is a network number, return YES
256 * if it matches the head of the string.
257 */
258
259 if (tok[0] == '@') { /* netgroup */
260 return (netgroup_match(tok + 1, string, (char *) 0));
261 } else if (string_match(tok, string)) { /* ALL or exact match */
262 return (YES);
263 } else if (tok[0] == '.') { /* domain: match last fields */
264 if ((str_len = strlen(string)) > (tok_len = strlen(tok))
265 && strcasecmp(tok, string + str_len - tok_len) == 0)
266 return (YES);
267 } else if (strcmp(tok, "LOCAL") == 0) { /* local: no dots */
268 if (strchr(string, '.') == NULL)
269 return (YES);
270 } else if (tok[(tok_len = strlen(tok)) - 1] == '.' /* network */
271 && strncmp(tok, string, tok_len) == 0) {
272 return (YES);
273 }
274 return (NO);
275 }
276
277 /* string_match - match a string against one token */
278
279 static int
string_match(const char * tok,const char * string)280 string_match(const char *tok, const char *string)
281 {
282
283 /*
284 * If the token has the magic value "ALL" the match always succeeds.
285 * Otherwise, return YES if the token fully matches the string.
286 */
287
288 if (strcmp(tok, "ALL") == 0) { /* all: always matches */
289 return (YES);
290 } else if (strcasecmp(tok, string) == 0) { /* try exact match */
291 return (YES);
292 }
293 return (NO);
294 }
295