summaryrefslogtreecommitdiff
path: root/modules/pam_securetty/pam_securetty.c
blob: 274b3b7439e05e4b78215dc37d8b1d765d94a25a (plain)
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
/* pam_securetty module */

#define SECURETTY_FILE "/etc/securetty"
#define TTY_PREFIX     "/dev/"

/*
 * 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
 */

#define _GNU_SOURCE

#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>

/*
 * here, we make a definition for the externally accessible function
 * in this file (this definition is required for static a module
 * but strongly encouraged generally) it is used to instruct the
 * modules include file to define the function prototypes.
 */

#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT

#include <security/pam_modules.h>

/* some syslogging */

static void _pam_log(int err, const char *format, ...)
{
    va_list args;

    va_start(args, format);
    openlog("PAM-securetty", LOG_CONS|LOG_PID, LOG_AUTH);
    vsyslog(err, format, args);
    va_end(args);
    closelog();
}

/* argument parsing */

#define PAM_DEBUG_ARG       0x0001

static int _pam_parse(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 {
	    _pam_log(LOG_ERR,"pam_parse: unknown option; %s",*argv);
	}
    }

    return ctrl;
}

static int securetty_perform_check(pam_handle_t *pamh, int flags, int ctrl,
				   const char *function_name)
{
    int retval = PAM_AUTH_ERR;
    const char *username;
    char *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_log(LOG_DEBUG, "pam_securetty called via %s function",
		 function_name);
    }

    retval = pam_get_user(pamh, &username, NULL);
    if (retval != PAM_SUCCESS || username == NULL) {
	if (ctrl & PAM_DEBUG_ARG) {
            _pam_log(LOG_WARNING, "cannot determine username");
	}
	return (retval == PAM_CONV_AGAIN ? PAM_INCOMPLETE:PAM_SERVICE_ERR);
    }

    user_pwd = getpwnam(username);
    if (user_pwd == NULL) {
	return PAM_IGNORE;
    } else if (user_pwd->pw_uid != 0) { /* If the user is not root,
					   securetty's does not apply
					   to them */
	return PAM_SUCCESS;
    }

    retval = pam_get_item(pamh, PAM_TTY, (const void **)&uttyname);
    if (retval != PAM_SUCCESS || uttyname == NULL) {
        if (ctrl & PAM_DEBUG_ARG) {
            _pam_log(LOG_WARNING, "cannot determine user's tty");
	}
	return PAM_SERVICE_ERR;
    }

    /* The PAM_TTY item may be prefixed with "/dev/" - skip that */
    if (strncmp(TTY_PREFIX, uttyname, sizeof(TTY_PREFIX)-1) == 0) {
	uttyname += sizeof(TTY_PREFIX)-1;
    }

    if (stat(SECURETTY_FILE, &ttyfileinfo)) {
	_pam_log(LOG_NOTICE, "Couldn't open " SECURETTY_FILE);
	return PAM_SUCCESS; /* for compatibility with old securetty handling,
			       this needs to succeed.  But we still log the
			       error. */
    }

    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_log(LOG_ERR, SECURETTY_FILE
		 " is either world writable or not a normal file");
	return PAM_AUTH_ERR;
    }

    ttyfile = fopen(SECURETTY_FILE,"r");
    if (ttyfile == NULL) { /* Check that we opened it successfully */
	_pam_log(LOG_ERR,
		 "Error opening " SECURETTY_FILE);
	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) {
	if (ctrl & PAM_DEBUG_ARG) {
	    _pam_log(LOG_WARNING, "access denied: tty '%s' is not secure !",
		     uttyname);
	}
	retval = PAM_AUTH_ERR;

    } else {
	if ((retval == PAM_SUCCESS) && (ctrl & PAM_DEBUG_ARG)) {
	    _pam_log(LOG_DEBUG, "access allowed for '%s' on '%s'",
		     username, uttyname);
	}
	retval = PAM_SUCCESS;

    }

    return retval;
}

/* --- authentication management functions --- */

PAM_EXTERN
int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc,
			const char **argv)
{
    int ctrl;

    /* parse the arguments */
    ctrl = _pam_parse(argc, argv);

    return securetty_perform_check(pamh, flags, ctrl, __FUNCTION__);
}

PAM_EXTERN
int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
    return PAM_SUCCESS;
}

/* --- account management functions --- */

PAM_EXTERN
int pam_sm_acct_mgmt(pam_handle_t *pamh, int flags, int argc,
		     const char **argv)
{
    int ctrl;

    /* parse the arguments */
    ctrl = _pam_parse(argc, argv);

    /* take the easy route */
    return securetty_perform_check(pamh, flags, ctrl, __FUNCTION__);
}


#ifdef PAM_STATIC

/* static module data */

struct pam_module _pam_securetty_modstruct = {
     "pam_securetty",
     pam_sm_authenticate,
     pam_sm_setcred,
     pam_sm_acct_mgmt,
     NULL,
     NULL,
     NULL,
};

#endif /* PAM_STATIC */

/* end of module definition */