summaryrefslogtreecommitdiffstats
path: root/bin/ykfde.c
blob: 30a4665d5e6cc47f7004763e999c776162503582 (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
/*
 * (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 -lcryptsetup -liniparser
 */

#ifndef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE
#endif

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/stat.h>

#include <iniparser.h>

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

#include <libcryptsetup.h>

#include "../config.h"

/* challenge is 64 byte,
 * HMAC-SHA1 response is 40 byte */
#define CHALLENGELEN	64
#define RESPONSELEN	SHA1_MAX_BLOCK_SIZE
#define PASSPHRASELEN	SHA1_DIGEST_SIZE * 2

int main(int argc, char **argv) {
	char challenge_old[CHALLENGELEN + 1],
		challenge_new[CHALLENGELEN + 1],
		repose_old[RESPONSELEN],
		repose_new[RESPONSELEN],
		passphrase_old[PASSPHRASELEN + 1],
		passphrase_new[PASSPHRASELEN + 1];
	char challengefilename[sizeof(CHALLENGEDIR) + 11 /* "/challenge-" */ + 10 /* unsigned int in char */ + 1],
		challengefiletmpname[sizeof(CHALLENGEDIR) + 11 /* "/challenge-" */ + 10 /* unsigned int in char */ + 7 /* -XXXXXX */ + 1];
	int challengefile = 0, challengefiletmp = 0;
	struct timeval tv;
	int i;
	int8_t rc = EXIT_FAILURE;
	/* cryptsetup */
	char * device_name;
	int8_t luks_slot = -1;
	struct crypt_device *cd;
	crypt_status_info cs;
	crypt_keyslot_info ck;
	/* yubikey */
	YK_KEY * yk;
	uint8_t yk_slot = SLOT_CHAL_HMAC2;
	unsigned int serial = 0;
	/* iniparser */
	dictionary * ini;
	char section_ykslot[10 /* unsigned int in char */ + 1 + sizeof(CONFYKSLOT) + 1];
	char section_luksslot[10 /* unsigned int in char */ + 1 + sizeof(CONFLUKSSLOT) + 1];

	/* initialize random seed */
	gettimeofday(&tv, NULL);
	srand(tv.tv_usec * tv.tv_sec);

	memset(challenge_old, 0, CHALLENGELEN + 1);
	memset(challenge_new, 0, CHALLENGELEN + 1);
	memset(repose_old, 0, RESPONSELEN);
	memset(repose_new, 0, RESPONSELEN);
	memset(passphrase_old, 0, PASSPHRASELEN + 1);
	memset(passphrase_new, 0, PASSPHRASELEN + 1);

	if ((ini = iniparser_load(CONFIGFILE)) == NULL) {
		rc = EXIT_FAILURE;
		fprintf(stderr, "Could not parse configuration file.\n");
		goto out10;
	}

	if ((device_name = iniparser_getstring(ini, "general:" CONFDEVNAME, NULL)) == NULL) {
		rc = EXIT_FAILURE;
		/* read from crypttab? */
		/* get device from currently open devices? */
		fprintf(stderr, "Could not read LUKS device from configuration file.\n");
		goto out20;
	}

	/* init and open first Yubikey */
	if ((rc = yk_init()) < 0) {
		perror("yk_init() failed");
		goto out20;
	}

	if ((yk = yk_open_first_key()) == NULL) {
		rc = EXIT_FAILURE;
		perror("yk_open_first_key() failed");
		goto out30;
	}

	/* read the serial number from key */
	if ((rc = yk_get_serial(yk, 0, 0, &serial)) < 0) {
		perror("yk_get_serial() failed");
		goto out40;
	}

	/* get the yk slot */
	sprintf(section_ykslot, "%d:" CONFYKSLOT, serial);
	yk_slot = iniparser_getint(ini, "general:" CONFYKSLOT, yk_slot);
	yk_slot = iniparser_getint(ini, section_ykslot, yk_slot);
	switch (yk_slot) {
		case 1:
		case SLOT_CHAL_HMAC1:
			yk_slot = SLOT_CHAL_HMAC1;
			break;
		case 2:
		case SLOT_CHAL_HMAC2:
		default:
			yk_slot = SLOT_CHAL_HMAC2;
			break;
	}

	/* get the luks slot */
	sprintf(section_luksslot, "%d:" CONFLUKSSLOT, serial);
	luks_slot = iniparser_getint(ini, section_luksslot, luks_slot);
	if (luks_slot < 0) {
		rc = EXIT_FAILURE;
		fprintf(stderr, "Please set LUKS key slot for Yubikey with serial %d!\n", serial);
		printf("Add something like this to " CONFIGFILE ":\n\n[%d]\nluks slot = 1\n", serial);
		goto out40;
	}

	/* get random number and limit to printable ASCII character (32 to 126) */
	for(i = 0; i < CHALLENGELEN; i++)
		challenge_new[i] = (rand() % (126 - 32)) + 32;

	/* do challenge/response and encode to hex */
	if ((rc = yk_challenge_response(yk, yk_slot, true,
				CHALLENGELEN, (unsigned char *)challenge_new,
				RESPONSELEN, (unsigned char *)repose_new)) < 0) {
		perror("yk_challenge_response() failed");
		goto out40;
	}
	yubikey_hex_encode((char *)passphrase_new, (char *)repose_new, 20);

	/* initialize crypt device */
	if ((rc = crypt_init_by_name(&cd, device_name)) < 0) {
		fprintf(stderr, "Device %s failed to initialize.\n", device_name);
		goto out40;
	}

	/* these are the filenames for challenge
	 * we need this for reading and writing */
	sprintf(challengefilename, CHALLENGEDIR "/challenge-%d", serial);
	sprintf(challengefiletmpname, CHALLENGEDIR "/challenge-%d-XXXXXX", serial);

	/* write new challenge to file */
	if ((rc = challengefiletmp = mkstemp(challengefiletmpname)) < 0) {
		fprintf(stderr, "Could not open file %s for writing.\n", challengefiletmpname);
		goto out50;
	}
	if ((rc = write(challengefiletmp, challenge_new, CHALLENGELEN)) < 0) {
		fprintf(stderr, "Failed to write challenge to file.\n");
		goto out60;
	}
	challengefiletmp = close(challengefiletmp);

	/* get status of crypt device
	 * We expect this to be active (or busy). It is the actual root device, no? */
	cs = crypt_status(cd, device_name);
	if (cs != CRYPT_ACTIVE && cs != CRYPT_BUSY) {
		rc = EXIT_FAILURE;
                fprintf(stderr, "Device %s is invalid or inactive.\n", device_name);
		goto out60;
	}

	ck = crypt_keyslot_status(cd, luks_slot);
	if (ck == CRYPT_SLOT_INVALID) {
		rc = EXIT_FAILURE;
		fprintf(stderr, "Key slot %d is invalid.\n", luks_slot);
		goto out60;
	} else if (ck == CRYPT_SLOT_ACTIVE || ck == CRYPT_SLOT_ACTIVE_LAST) {
		/* read challenge from file */
		if ((rc = challengefile = open(challengefilename, O_RDONLY)) < 0) {
			perror("Failed opening challenge file for reading");
			goto out60;
		}

		if ((rc = read(challengefile, challenge_old, CHALLENGELEN)) < 0) {
			perror("Failed reading challenge from file");
			goto out60;
		}

		challengefile = close(challengefile);
		/* finished reading challenge */

		/* do challenge/response and encode to hex */
		if ((rc = yk_challenge_response(yk, yk_slot, true,
					CHALLENGELEN, (unsigned char *)challenge_old,
					RESPONSELEN, (unsigned char *)repose_old)) < 0) {
			perror("yk_challenge_response() failed");
			goto out60;
		}
		yubikey_hex_encode((char *)passphrase_old, (char *)repose_old, 20);

		if ((rc = crypt_keyslot_change_by_passphrase(cd, luks_slot, luks_slot,
				passphrase_old, PASSPHRASELEN,
				passphrase_new, PASSPHRASELEN)) < 0) {
			fprintf(stderr, "Could not update passphrase for key slot %d.\n", luks_slot);
			goto out60;
		}

		if ((rc = unlink(challengefilename)) < 0) {
			fprintf(stderr, "Failed to delete old challenge file.\n");
			goto out60;
		}
	} else { /* ck == CRYPT_SLOT_INACTIVE */
		if ((rc = crypt_keyslot_add_by_passphrase(cd, luks_slot, NULL, 0,
				passphrase_new, PASSPHRASELEN)) < 0) {
			fprintf(stderr, "Could add passphrase for key slot %d.\n", luks_slot);
			goto out60;
		}
	}

	if ((rc = rename(challengefiletmpname, challengefilename)) < 0) {
		fprintf(stderr, "Failed to rename new challenge file.\n");
		goto out60;
	}

	rc = EXIT_SUCCESS;

out60:
	/* close the challenge file */
	if (challengefile)
		close(challengefile);
	if (challengefiletmp)
		close(challengefiletmp);
	if (access(challengefiletmpname, F_OK) == 0 )
		unlink(challengefiletmpname);

out50:
	/* free crypt context */
	crypt_free(cd);

out40:
	/* close Yubikey */
	if (!yk_close_key(yk))
		perror("yk_close_key() failed");

out30:
	/* release Yubikey */
	if (!yk_release())
		perror("yk_release() failed");

out20:
	/* free iniparser dictionary */
	iniparser_freedict(ini);


out10:
	/* wipe response (cleartext password!) from memory */
	/* This is statically allocated and always save to wipe! */
	memset(challenge_old, 0, CHALLENGELEN + 1);
	memset(challenge_new, 0, CHALLENGELEN + 1);
	memset(repose_old, 0, RESPONSELEN);
	memset(repose_new, 0, RESPONSELEN);
	memset(passphrase_old, 0, PASSPHRASELEN + 1);
	memset(passphrase_new, 0, PASSPHRASELEN + 1);

	return rc;
}

// vim: set syntax=c: