aboutsummaryrefslogtreecommitdiff
path: root/src/pam-freerdp.c
blob: 9fc43ed33f6d6bd37f3be37bc50b0cad07d87885 (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
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
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
/*
 * Copyright © 2012 Canonical Ltd.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 3, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranties of
 * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Author: Ted Gould <ted@canonical.com>
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <pwd.h>

#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <security/pam_appl.h>

#define PAM_TYPE_DOMAIN  1234

/* Either grab a value or prompt for it */
static char *
get_item (pam_handle_t * pamh, int type)
{
	/* Check to see if we just have the value.  If we do, great
	   let's dup it some we're consitently allocating memory */
	if (type != PAM_TYPE_DOMAIN) {
		char * value = NULL;
		if (pam_get_item(pamh, type, (const void **)&value) == PAM_SUCCESS && value != NULL) {
			return strdup(value);
		}
	}
	/* Now we need to prompt */

	/* Build up the message we're prompting for */
	struct pam_message message;
	const struct pam_message * pmessage = &message;

	message.msg = NULL;
	message.msg_style = PAM_PROMPT_ECHO_ON;

	switch (type) {
	case PAM_USER:
		message.msg = "login:";
		break;
	case PAM_RUSER:
		message.msg = "remote login:";
		break;
	case PAM_RHOST:
		message.msg = "remote host:";
		break;
	case PAM_AUTHTOK:
		message.msg = "password:";
		message.msg_style = PAM_PROMPT_ECHO_OFF;
		break;
	case PAM_TYPE_DOMAIN:
		message.msg = "domain:";
		break;
	default:
		return NULL;
	}

	struct pam_conv * conv = NULL;
	if (pam_get_item(pamh, PAM_CONV, (const void **)&conv) != PAM_SUCCESS || conv == NULL || conv->conv == NULL) {
		return NULL;
	}

	struct pam_response * responses = NULL;
	if (conv->conv(1, &pmessage, &responses, conv->appdata_ptr) != PAM_SUCCESS) {
		return NULL;
	}

	char * retval = responses->resp;
	free(responses);
	return retval;
}

#define GET_ITEM(val, type) \
	if ((val = get_item(pamh, type)) == NULL) { \
		retval = PAM_AUTH_ERR; \
		goto done; \
	}

/* TODO: Make this a build thing */
#define XFREERDP "/usr/bin/xfreerdp"

/* Authenticate.  We need to make sure we have a user account, that
   there are remote accounts and then verify them with FreeRDP */
PAM_EXTERN int
pam_sm_authenticate (pam_handle_t *pamh, int flags, int argc, const char **argv)
{
	char * username = NULL;
	char * password = NULL;
	char * ruser = NULL;
	char * rhost = NULL;
	char * rdomain = NULL;
	int retval = PAM_IGNORE;

	/* Get all the values, or prompt for them, or return with
	   an auth error */
	GET_ITEM(username, PAM_USER);
	GET_ITEM(ruser,    PAM_RUSER);
	GET_ITEM(rhost,    PAM_RHOST);
	GET_ITEM(rdomain,  PAM_TYPE_DOMAIN);
	GET_ITEM(password, PAM_AUTHTOK);

	int stdinpipe[2];
	if (pipe(stdinpipe) != 0) {
		retval = PAM_SYSTEM_ERR;
		goto done;
	}

	/* At this point we should have the values, let's check the auth */
	pid_t pid;
	switch (pid = fork()) {
	case 0: { /* child */
		dup2(stdinpipe[0], 0);

		char * args[7];

		args[0] = XFREERDP;
		args[1] = "--plugin";
		args[2] = "rdpsnd.so";
		args[3] = "--no-nla";
		args[4] = "-f";
		args[5] = "--from-stdin";
		args[6] = NULL;

		struct passwd * pwdent = getpwnam(username);
		if (pwdent == NULL) {
			_exit(EXIT_FAILURE);
		}

		if (setgid(pwdent->pw_gid) < 0 || setuid(pwdent->pw_uid) < 0 ||
				setegid(pwdent->pw_gid) < 0 || seteuid(pwdent->pw_uid) < 0) {
			_exit(EXIT_FAILURE);
		}

		setenv("HOME", pwdent->pw_dir, 1);

		execvp(args[0], args);
		_exit(EXIT_FAILURE);
		break;
	}
	case -1: { /* fork'n error! */
		retval = PAM_SYSTEM_ERR;
		break;
	}
	default: {
		int forkret = 0;
		int bytesout = 0;

		bytesout += write(stdinpipe[1], ruser, strlen(ruser));
		bytesout += write(stdinpipe[1], " ", 1);
		bytesout += write(stdinpipe[1], password, strlen(password));
		bytesout += write(stdinpipe[1], " ", 1);
		bytesout += write(stdinpipe[1], rdomain, strlen(rdomain));
		bytesout += write(stdinpipe[1], " ", 1);
		bytesout += write(stdinpipe[1], rhost, strlen(rhost));
		bytesout += write(stdinpipe[1], " ", 1);

		close(stdinpipe[1]);

		if (waitpid(pid, &forkret, 0) < 0 || bytesout == 0) {
			retval = PAM_SYSTEM_ERR;
		} else if (forkret == 0) {
			retval = PAM_SUCCESS;
		} else {
			retval = PAM_AUTH_ERR;
		}
	}
	}

	/* Free Memory and return our status */
done:
	if (username != NULL) { free(username); }
	if (password != NULL) { free(password); }
	if (ruser != NULL)    { free(ruser); }
	if (rhost != NULL)    { free(rhost); }
	if (rdomain != NULL)  { free(rdomain); }

	return retval;
}

pid_t session_pid = 0;
/* Open Session.  Here we need to fork a little process so that we can
   give the credentials to the session itself so that it can startup the
   xfreerdp viewer for the login */
PAM_EXTERN int
pam_sm_open_session (pam_handle_t *pamh, int flags, int argc, const char ** argv)
{
	if (session_pid != 0) {
		kill(session_pid, SIGKILL);
		session_pid = 0;
	}

	char * username = NULL;
	char * password = NULL;
	char * ruser = NULL;
	char * rhost = NULL;
	char * rdomain = NULL;
	int retval = PAM_SUCCESS;

	/* Get all the values, or prompt for them, or return with
	   an auth error */
	GET_ITEM(username, PAM_USER);
	GET_ITEM(ruser,    PAM_RUSER);
	GET_ITEM(rhost,    PAM_RHOST);
	GET_ITEM(rdomain,  PAM_TYPE_DOMAIN);
	GET_ITEM(password, PAM_AUTHTOK);

	struct passwd * pwdent = getpwnam(username);
	if (pwdent == NULL) {
		retval = PAM_SYSTEM_ERR;
		goto done;
	}
	
	/* Make our socket and bind it */
	int socketfd;
	struct sockaddr_un socket_addr;

	socketfd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (socketfd < 0) {
		retval = PAM_SYSTEM_ERR;
		goto done;
	}

	memset(&socket_addr, 0, sizeof(struct sockaddr_un));
	socket_addr.sun_family = AF_UNIX;
	strncpy(socket_addr.sun_path, pwdent->pw_dir, sizeof(socket_addr.sun_path) - 1);
	strncpy(socket_addr.sun_path + strlen(pwdent->pw_dir), "/.freerdp-socket", sizeof(socket_addr.sun_path) - 1);

	/* We bind the socket before forking so that we ensure that
	   there isn't a race condition to get to it.  Things will block
	   otherwise. */
	if (bind(socketfd, (struct sockaddr *)&socket_addr, sizeof(struct sockaddr_un)) < 0) {
		close(socketfd);
		retval = PAM_SYSTEM_ERR;
		goto done;
	}

	/* Build this up as a buffer so we can just write it and see that
	   very, very clearly */
	int buffer_len = 0;
	buffer_len += strlen(ruser) + 1;    /* Add one for the space */
	buffer_len += strlen(rhost) + 1;    /* Add one for the space */
	buffer_len += strlen(rdomain) + 1;  /* Add one for the space */
	buffer_len += strlen(password) + 1; /* Add one for the NULL */

	char * buffer = malloc(buffer_len);
	snprintf(buffer, buffer_len, "%s %s %s %s", ruser, password, rdomain, rhost);

	pid_t pid = fork();
	if (pid == 0) {
		if (setgid(pwdent->pw_gid) < 0 || setuid(pwdent->pw_uid) < 0 ||
				setegid(pwdent->pw_gid) < 0 || seteuid(pwdent->pw_uid) < 0) {
			_exit(EXIT_FAILURE);
		}

		if (listen(socketfd, 1) < 0) {
			_exit(EXIT_FAILURE);
		}

		socklen_t connected_addr_size;
		int connectfd;
		struct sockaddr_un connected_addr;

		connected_addr_size = sizeof(struct sockaddr_un);
		connectfd = accept(socketfd, (struct sockaddr *)&connected_addr, &connected_addr_size);
		if (connectfd < 0) {
			_exit(EXIT_FAILURE);
		}

		int writedata;
		writedata = write(connectfd, buffer, buffer_len);

		close(connectfd);
		close(socketfd);
		free(buffer);

		if (writedata == buffer_len) {
			_exit(0);
		} else {
			_exit(EXIT_FAILURE);
		}
	} else if (pid < 0) {
		retval = PAM_SYSTEM_ERR;
		close(socketfd);
		free(buffer);
	} else {
		session_pid = pid;
	}

done:
	if (username != NULL) { free(username); }
	if (password != NULL) { free(password); }
	if (ruser != NULL)    { free(ruser); }
	if (rhost != NULL)    { free(rhost); }
	if (rdomain != NULL)  { free(rdomain); }

    return retval;
}

/* Close Session.  Make sure our little guy has died so he doesn't become
   a zombie and eat things. */
PAM_EXTERN int
pam_sm_close_session (pam_handle_t *pamh, int flags, int argc, const char **argv)
{
	if (session_pid != 0) {
		kill(session_pid, SIGKILL);
		session_pid = 0;
	}

	return PAM_IGNORE;
}

#ifdef PAM_STATIC

struct pam_module _pam_freerdp_modstruct = {
     "pam-freerdp",
     pam_sm_authenticate,
     NULL,
     NULL,
     pam_sm_open_session,
     pam_sm_close_session,
     NULL,
};

#endif