summaryrefslogtreecommitdiffstats
path: root/udev/ykfde.c
blob: c97c9bdbee89f22c58ede23a4a11bb78994d3f18 (about) (plain) (blame)
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
/*
 * (C) 2014 by Christian Hesse <mail@eworm.de>
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 * compile with:
 * $ gcc -o ykfde ykfde.c -lykpers-1 -lyubikey -liniparser
 *
 * test woth:
 * $ systemd-ask-password --no-tty "Please enter passphrase for disk foobar..."
 */

#include <dirent.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/inotify.h>
#include <sys/poll.h>
#include <sys/signalfd.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>

#include <yubikey.h>
#include <ykpers-1/ykdef.h>
#include <ykpers-1/ykcore.h>

#include <iniparser.h>

#define EVENT_SIZE	(sizeof (struct inotify_event))
#define EVENT_BUF_LEN	(1024 * (EVENT_SIZE + 16))

#define ASK_PATH	"/run/systemd/ask-password/"
#define ASK_MESSAGE	"Please enter passphrase for disk"

#define	CONFIGFILE	"/etc/ykfde.conf"
#define CHALLENGEDIR	"/etc/ykfde.d/"

static int send_on_socket(int fd, const char *socket_name, const void *packet, size_t size) {
        union {
                struct sockaddr sa;
                struct sockaddr_un un;
        } sa = {
                .un.sun_family = AF_UNIX,
        };

        strncpy(sa.un.sun_path, socket_name, sizeof(sa.un.sun_path));

        if (sendto(fd, packet, size, MSG_NOSIGNAL, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(socket_name)) < 0) {
                perror("sendto() failed");
                return EXIT_FAILURE;
        }

        return EXIT_SUCCESS;
}

static int try_answer(char * ask_file, char * response) {
	int8_t ret = EXIT_FAILURE;
	dictionary * ini;
	char * ask_message, * ask_socket;
	int fd_askpass;

	if ((ini = iniparser_load(ask_file)) == NULL)
		perror("cannot parse file");

	ask_message = iniparser_getstring(ini, "Ask:Message", NULL);

	if (strncmp(ask_message, ASK_MESSAGE, strlen(ASK_MESSAGE)) != 0)
		goto out1;

	ask_socket = iniparser_getstring(ini, "Ask:Socket", NULL);

	if ((fd_askpass = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0)) < 0) {
		perror("socket() failed");
		goto out1;
	}

	if (send_on_socket(fd_askpass, ask_socket, response, strlen(response)) < 0) {
		perror("send_on_socket() failed");
		goto out2;
	}

	ret = EXIT_SUCCESS;

out2:
	close(fd_askpass);

out1:
	iniparser_freedict(ini);

	return ret;
}

int main(int argc, char **argv) {
	int8_t ret = EXIT_FAILURE;
	/* Yubikey */
	YK_KEY * yk;
	uint8_t slot = SLOT_CHAL_HMAC2;
	unsigned int serial = 0;
	unsigned char response[SHA1_MAX_BLOCK_SIZE];
	unsigned char response_hex[(SHA1_MAX_BLOCK_SIZE * 2) + 1];
	char response_askpass[(SHA1_MAX_BLOCK_SIZE * 2) + 2];
	/* iniparser */
	dictionary * ini;
	char section_serial[10 /* unsigned int in char */ + 5 /* ":slot" */ + 1];
	/* read challenge */
	size_t fsize;
	char * challenge;
	char challengefilename[sizeof(CHALLENGEDIR) + 11 /* "/challenge-" */ + 10 /* unsigned int in char */ + 1];
        FILE * challengefile;
	/* read dir */
	DIR * dir;
	struct dirent * ent;
	/* inotify */
	struct inotify_event * event;
	int fd_inotify, watch, length, i = 0;
	char buffer[EVENT_BUF_LEN];

	/* reopening stderr to /dev/console may help debugging... */
	/* freopen("/dev/console", "w", stderr); */

	/* init and open first Yubikey */
	if (!yk_init()) {
		perror("yk_init() failed");
		goto out10;
	}

	if ((yk = yk_open_first_key()) == NULL) {
		perror("yk_open_first_key() failed");
		goto out20;
	}

	/* read the serial number from key */
	if(!yk_get_serial(yk, 0, 0, &serial)) {
		perror("yk_get_serial() failed");
		goto out30;
	}

	sprintf(challengefilename, CHALLENGEDIR "/challenge-%d", serial);

	/* check if challenge file exists */
	if (access(challengefilename, R_OK) == -1)
		goto out30;

	/* read challenge from file */
	if ((challengefile = fopen(challengefilename, "r")) == NULL) {
		perror("Failed opening challenge file for reading");
		goto out30;
	}
	fseek(challengefile, 0, SEEK_END);
	fsize = ftell(challengefile);
	fseek(challengefile, 0, SEEK_SET);

	if ((challenge = malloc(fsize + 1)) == NULL) {
		perror("malloc() failed");
		goto out40;
	}

	if ((fread(challenge, fsize, 1, challengefile)) != 1) {
		perror("Failed reading challenge from file");
		goto out50;
	}
	challenge[fsize] = 0;
	/* finished reading challenge */

	/* try to read config file
	 * if anything here fails we do not care... slot 2 is the default */
	if ((ini = iniparser_load(CONFIGFILE)) != NULL) {
		/* first try the general setting */
		slot = iniparser_getint(ini, "general:slot", slot);

		sprintf(section_serial, "%d:slot", serial);

		/* then probe for setting with serial number */
		slot = iniparser_getint(ini, section_serial, slot);

		switch (slot) {
			case '1':
				slot = SLOT_CHAL_HMAC1;
				break;
			default: /* slot 2 is default */
				slot = SLOT_CHAL_HMAC2;
				break;
		}

		iniparser_freedict(ini);
	}

	memset(response, 0, sizeof(response));
	memset(response_hex, 0, sizeof(response_hex));

	/* do challenge/response and encode to hex */
	if (!yk_challenge_response(yk, slot, true, strlen(challenge), (unsigned char *)challenge, sizeof(response), response)) {
		perror("yk_challenge_response() failed");
		goto out50;
	}
	yubikey_hex_encode((char *)response_hex, (char *)response, 20);

	sprintf(response_askpass, "+%s", response_hex);

	/* change to directory so we do not have to assemble complete/absolute path */
	if (chdir(ASK_PATH) != 0) {
		perror("chdir() failed");
		goto out50;
	}

	/* creating the INOTIFY instance and add ASK_PATH directory into watch list */
	if ((fd_inotify = inotify_init()) < 0) {
		perror("inotify_init() failed");
		goto out50;
	}

	watch = inotify_add_watch(fd_inotify, ASK_PATH, IN_MOVED_TO);

	/* Is the request already there?
	 * We do this AFTER setting up the inotify watch. This way we do not have race condition. */
	if ((dir = opendir(ASK_PATH)) != NULL) {
		while ((ent = readdir(dir)) != NULL) {
			if (strncmp(ent->d_name, "ask.", 4) == 0) {
				if ((ret = try_answer(ent->d_name, response_askpass)) == EXIT_SUCCESS)
					goto out70;
			}
		}
	} else {
		perror ("opendir() failed");
		goto out60;
	}

	/* read to determine the event change happens. Actually this read blocks until the change event occurs */
	if ((length = read(fd_inotify, buffer, EVENT_BUF_LEN)) < 0) {
		perror("read() failed");
		goto out70;
	}

	/* actually read return the list of change events happens.
	 * Here, read the change event one by one and process it accordingly. */
	while (i < length) {
		event = (struct inotify_event *)&buffer[i];
		if (event->len > 0)
			if ((ret = try_answer(event->name, response_askpass)) == EXIT_SUCCESS)
				goto out70;
		i += EVENT_SIZE + event->len;
	}

out70:
	/* close dir */
	closedir(dir);

out60:
	/* remove inotify watch and remove file handle */
	inotify_rm_watch(fd_inotify, watch);
	close(fd_inotify);

out50:
	/* free challenge */
	free(challenge);

out40:
	/* close the challenge file */
	fclose(challengefile);
	/* Unlink it if we were successful, we can not try again later! */
	if (ret == EXIT_SUCCESS)
		unlink(challengefilename);

out30:
	/* wipe response (cleartext password!) from memory */
	memset(response, 0, sizeof(response));
	memset(response_hex, 0, sizeof(response_hex));
	memset(response_askpass, 0, sizeof(response_askpass));

	/* close Yubikey */
	if (!yk_close_key(yk))
		perror("yk_close_key() failed");

out20:
	/* release Yubikey */
	if (!yk_release())
		perror("yk_release() failed");

out10:
	return ret;
}

// vim: set syntax=c: