1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
|
/*
* pam_securetty module
*
* by Elliot Lee <sopwith@redhat.com>, Red Hat Software.
* July 25, 1996.
* This code shamelessly ripped from the pam_rootok module.
* Slight modifications AGM. 1996/12/3
*/
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <syslog.h>
#include <stdarg.h>
#include <pwd.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <errno.h>
#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <security/pam_ext.h>
#include "pam_inline.h"
#define PAM_DEBUG_ARG 0x0001
#define PAM_NOCONSOLE_ARG 0x0002
#define SECURETTY_FILE "/etc/securetty"
#ifdef VENDORDIR
#define SECURETTY2_FILE VENDORDIR"/securetty"
#endif
#define TTY_PREFIX "/dev/"
#define CMDLINE_FILE "/proc/cmdline"
#define CONSOLEACTIVE_FILE "/sys/class/tty/console/active"
static int
_pam_parse (const pam_handle_t *pamh, int argc, const char **argv)
{
int ctrl=0;
/* step through arguments */
for (ctrl=0; argc-- > 0; ++argv) {
/* generic options */
if (!strcmp(*argv,"debug"))
ctrl |= PAM_DEBUG_ARG;
else if (!strcmp(*argv, "noconsole"))
ctrl |= PAM_NOCONSOLE_ARG;
else {
pam_syslog(pamh, LOG_ERR, "unknown option: %s", *argv);
}
}
return ctrl;
}
static int
securetty_perform_check (pam_handle_t *pamh, int ctrl,
const char *function_name)
{
int retval = PAM_AUTH_ERR;
const char *securettyfile;
const char *username;
const char *uttyname;
const char *str;
const void *void_uttyname;
char ttyfileline[256];
char ptname[256];
struct stat ttyfileinfo;
struct passwd *user_pwd;
FILE *ttyfile;
/* log a trail for debugging */
if (ctrl & PAM_DEBUG_ARG) {
pam_syslog(pamh, LOG_DEBUG, "pam_securetty called via %s function",
function_name);
}
retval = pam_get_user(pamh, &username, NULL);
if (retval != PAM_SUCCESS) {
pam_syslog(pamh, LOG_WARNING, "cannot determine username");
return (retval == PAM_CONV_AGAIN ? PAM_INCOMPLETE:PAM_SERVICE_ERR);
}
user_pwd = pam_modutil_getpwnam(pamh, username);
if (user_pwd != NULL && user_pwd->pw_uid != 0) {
/* If the user is not root, securetty's does not apply to them */
return PAM_SUCCESS;
}
/* The user is now either root or an invalid / mistyped username */
retval = pam_get_item(pamh, PAM_TTY, &void_uttyname);
uttyname = void_uttyname;
if (retval != PAM_SUCCESS || uttyname == NULL) {
pam_syslog (pamh, LOG_ERR, "cannot determine user's tty");
return PAM_SERVICE_ERR;
}
/* The PAM_TTY item may be prefixed with "/dev/" - skip that */
if ((str = pam_str_skip_prefix(uttyname, TTY_PREFIX)) != NULL)
uttyname = str;
if (stat(SECURETTY_FILE, &ttyfileinfo)) {
#ifdef VENDORDIR
if (errno == ENOENT) {
if (stat(SECURETTY2_FILE, &ttyfileinfo)) {
pam_syslog(pamh, LOG_NOTICE,
"Couldn't open %s: %m", SECURETTY2_FILE);
return PAM_SUCCESS; /* for compatibility with old securetty handling,
this needs to succeed. But we still log the
error. */
}
securettyfile = SECURETTY2_FILE;
} else {
#endif
pam_syslog(pamh, LOG_NOTICE, "Couldn't open %s: %m", SECURETTY_FILE);
return PAM_SUCCESS; /* for compatibility with old securetty handling,
this needs to succeed. But we still log the
error. */
#ifdef VENDORDIR
}
#endif
} else {
securettyfile = SECURETTY_FILE;
}
if ((ttyfileinfo.st_mode & S_IWOTH) || !S_ISREG(ttyfileinfo.st_mode)) {
/* If the file is world writable or is not a
normal file, return error */
pam_syslog(pamh, LOG_ERR,
"%s is either world writable or not a normal file",
securettyfile);
return PAM_AUTH_ERR;
}
ttyfile = fopen(securettyfile,"r");
if (ttyfile == NULL) { /* Check that we opened it successfully */
pam_syslog(pamh, LOG_ERR, "Error opening %s: %m", securettyfile);
return PAM_SERVICE_ERR;
}
if (isdigit(uttyname[0])) {
snprintf(ptname, sizeof(ptname), "pts/%s", uttyname);
} else {
ptname[0] = '\0';
}
retval = 1;
while ((fgets(ttyfileline, sizeof(ttyfileline)-1, ttyfile) != NULL)
&& retval) {
if (ttyfileline[strlen(ttyfileline) - 1] == '\n')
ttyfileline[strlen(ttyfileline) - 1] = '\0';
retval = ( strcmp(ttyfileline, uttyname)
&& (!ptname[0] || strcmp(ptname, uttyname)) );
}
fclose(ttyfile);
if (retval && !(ctrl & PAM_NOCONSOLE_ARG)) {
FILE *cmdlinefile;
/* Allow access from the kernel console, if enabled */
cmdlinefile = fopen(CMDLINE_FILE, "r");
if (cmdlinefile != NULL) {
char line[LINE_MAX], *p;
p = fgets(line, sizeof(line), cmdlinefile);
fclose(cmdlinefile);
for (; p; p = strstr(p+1, "console=")) {
const char *e;
/* Test whether this is a beginning of a word? */
if (p > line && p[-1] != ' ')
continue;
/* Is this our console? */
if ((e = pam_str_skip_prefix_len(p + 8, uttyname, strlen(uttyname))) == NULL)
continue;
/* Is there any garbage after the TTY name? */
if (*e == ',' || *e == ' ' || *e == '\n' || *e == 0) {
retval = 0;
break;
}
}
}
}
if (retval && !(ctrl & PAM_NOCONSOLE_ARG)) {
FILE *consoleactivefile;
/* Allow access from the active console */
consoleactivefile = fopen(CONSOLEACTIVE_FILE, "r");
if (consoleactivefile != NULL) {
char line[LINE_MAX], *p, *n;
line[0] = 0;
p = fgets(line, sizeof(line), consoleactivefile);
fclose(consoleactivefile);
if (p) {
/* remove the newline character at end */
if (line[strlen(line)-1] == '\n')
line[strlen(line)-1] = 0;
for (n = p; n != NULL; p = n+1) {
if ((n = strchr(p, ' ')) != NULL)
*n = '\0';
if (strcmp(p, uttyname) == 0) {
retval = 0;
break;
}
}
}
}
}
if (retval) {
pam_syslog(pamh, LOG_NOTICE, "access denied: tty '%s' is not secure !",
uttyname);
retval = PAM_AUTH_ERR;
if (user_pwd == NULL) {
retval = PAM_USER_UNKNOWN;
}
} else {
if (ctrl & PAM_DEBUG_ARG) {
pam_syslog(pamh, LOG_DEBUG, "access allowed for '%s' on '%s'",
username, uttyname);
}
retval = PAM_SUCCESS;
}
return retval;
}
/* --- authentication management functions --- */
int pam_sm_authenticate(pam_handle_t *pamh, int flags UNUSED, int argc,
const char **argv)
{
int ctrl;
/* parse the arguments */
ctrl = _pam_parse (pamh, argc, argv);
return securetty_perform_check(pamh, ctrl, __FUNCTION__);
}
int
pam_sm_setcred (pam_handle_t *pamh UNUSED, int flags UNUSED,
int argc UNUSED, const char **argv UNUSED)
{
return PAM_SUCCESS;
}
/* --- account management functions --- */
int
pam_sm_acct_mgmt (pam_handle_t *pamh, int flags UNUSED,
int argc, const char **argv)
{
int ctrl;
/* parse the arguments */
ctrl = _pam_parse (pamh, argc, argv);
/* take the easy route */
return securetty_perform_check(pamh, ctrl, __FUNCTION__);
}
/* end of module definition */
|
