/*
* (C) 2014-2016 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 -lcryptsetup -liniparser -lkeyutils -lykpers-1 -lyubikey
*/
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <iniparser.h>
#include <keyutils.h>
#include <yubikey.h>
#include <ykpers-1/ykdef.h>
#include <ykpers-1/ykcore.h>
#include <libcryptsetup.h>
#include "../config.h"
#include "../version.h"
#define PROGNAME "ykfde"
/* Yubikey supports write of 64 byte challenge to slot, returns
* HMAC-SHA1 response.
*
* Lengths are defined in ykpers-1/ykdef.h:
* SHA1_MAX_BLOCK_SIZE 64
* SHA1_DIGEST_SIZE 20
*
* For passphrase we use hex encoded digest, that is twice the
* length of binary digest. */
#define CHALLENGELEN SHA1_MAX_BLOCK_SIZE
#define RESPONSELEN SHA1_MAX_BLOCK_SIZE
#define PASSPHRASELEN SHA1_DIGEST_SIZE * 2
const static char optstring[] = "hn:s:V";
const static struct option options_long[] = {
/* name has_arg flag val */
{ "help", no_argument, NULL, 'h' },
{ "2nd-factor", required_argument, NULL, 's' },
{ "new-2nd-factor", required_argument, NULL, 'n' },
{ "version", no_argument, NULL, 'V' },
{ 0, 0, 0, 0 }
};
int main(int argc, char **argv) {
unsigned int version = 0, help = 0;
char challenge_old[CHALLENGELEN + 1],
challenge_new[CHALLENGELEN + 1],
response_old[RESPONSELEN],
response_new[RESPONSELEN],
passphrase_old[PASSPHRASELEN + 1],
passphrase_new[PASSPHRASELEN + 1];
const char * tmp;
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 */
const char * device_name;
int8_t luks_slot = -1;
struct crypt_device *cryptdevice;
crypt_status_info cryptstatus;
crypt_keyslot_info cryptkeyslot;
/* keyutils */
key_serial_t key;
void * payload = NULL;
char * new_2nd_factor = NULL;
size_t plen = 0;
/* 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 + 1 + sizeof(CONFLUKSSLOT) + 1];
/* get command line options */
while ((i = getopt_long(argc, argv, optstring, options_long, NULL)) != -1)
switch (i) {
case 'h':
help++;
break;
case 'n':
new_2nd_factor = strdup(optarg);
memset(optarg, '*', strlen(optarg));
break;
case 's':
payload = strdup(optarg);
memset(optarg, '*', strlen(optarg));
break;
case 'V':
version++;
break;
}
if (version > 0)
printf("%s: %s v%s (compiled: " __DATE__ ", " __TIME__ ")\n", argv[0], PROGNAME, VERSION);
if (help > 0)
fprintf(stderr, "usage: %s [-h] [-n <new-2nd-factor>] [-s <2nd-factor>] [-V]\n", argv[0]);
if (version > 0 || help > 0)
return EXIT_SUCCESS;
/* initialize random seed */
gettimeofday(&tv, NULL);
srand(tv.tv_usec * tv.tv_sec);
/* initialize static buffers */
memset(challenge_old, 0, CHALLENGELEN + 1);
memset(challenge_new, 0, CHALLENGELEN + 1);
memset(response_old, 0, RESPONSELEN);
memset(response_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;
fprintf(stderr, "No Yubikey available.\n");
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"
"Add something like this to " CONFIGFILE ":\n\n"
"[%d]\nluks slot = 1\n", serial, serial);
goto out40;
}
if (payload == NULL) {
/* get second factor from key store */
if ((key = request_key("user", "ykfde-2f", NULL, 0)) < 0)
fprintf(stderr, "Failed requesting key. That's ok if you do not use\n"
"second factor. Give it manually if required.\n");
if (key > -1) {
/* if we have a key id we have a key - so this should succeed */
if ((rc = keyctl_read_alloc(key, &payload)) < 0) {
perror("Failed reading payload from key");
goto out40;
}
} else
payload = strdup("");
}
/* 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;
/* 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 out40;
}
if ((rc = write(challengefiletmp, challenge_new, CHALLENGELEN)) < 0) {
fprintf(stderr, "Failed to write challenge to file.\n");
goto out50;
}
challengefiletmp = close(challengefiletmp);
/* now that the new challenge has been written to file...
* add second factor to new challenge */
tmp = new_2nd_factor ? new_2nd_factor : payload;
plen = strlen(tmp);
memcpy(challenge_new, tmp, plen < CHALLENGELEN / 2 ? plen : CHALLENGELEN / 2);
/* do challenge/response and encode to hex */
if ((rc = yk_challenge_response(yk, yk_slot, true,
CHALLENGELEN, (unsigned char *) challenge_new,
RESPONSELEN, (unsigned char *) response_new)) < 0) {
perror("yk_challenge_response() failed");
goto out50;
}
yubikey_hex_encode((char *) passphrase_new, (char *) response_new, SHA1_DIGEST_SIZE);
/* get status of crypt device
* We expect this to be active (or busy). It is the actual root device, no? */
cryptstatus = crypt_status(cryptdevice, device_name);
if (cryptstatus != CRYPT_ACTIVE && cryptstatus != CRYPT_BUSY) {
rc = EXIT_FAILURE;
fprintf(stderr, "Device %s is invalid or inactive.\n", device_name);
goto out60;
}
/* initialize crypt device */
if ((rc = crypt_init_by_name(&cryptdevice, device_name)) < 0) {
fprintf(stderr, "Device %s failed to initialize.\n", device_name);
goto out60;
}
cryptkeyslot = crypt_keyslot_status(cryptdevice, luks_slot);
if (cryptkeyslot == CRYPT_SLOT_INVALID) {
rc = EXIT_FAILURE;
fprintf(stderr, "Key slot %d is invalid.\n", luks_slot);
goto out60;
} else if (cryptkeyslot == CRYPT_SLOT_ACTIVE || cryptkeyslot == 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 */
/* copy the second factor */
plen = strlen(payload);
memcpy(challenge_old, payload, plen < CHALLENGELEN / 2 ? plen : CHALLENGELEN / 2);
/* do challenge/response and encode to hex */
if ((rc = yk_challenge_response(yk, yk_slot, true,
CHALLENGELEN, (unsigned char *) challenge_old,
RESPONSELEN, (unsigned char *) response_old)) < 0) {
perror("yk_challenge_response() failed");
goto out60;
}
yubikey_hex_encode((char *) passphrase_old, (char *) response_old, SHA1_DIGEST_SIZE);
if ((rc = crypt_keyslot_change_by_passphrase(cryptdevice, 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(cryptdevice, luks_slot, NULL, 0,
passphrase_new, PASSPHRASELEN)) < 0) {
fprintf(stderr, "Could not 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:
/* free crypt context */
crypt_free(cryptdevice);
out50:
/* close the challenge file */
if (challengefile)
close(challengefile);
if (challengefiletmp)
close(challengefiletmp);
if (access(challengefiletmpname, F_OK) == 0)
unlink(challengefiletmpname);
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(response_old, 0, RESPONSELEN);
memset(response_new, 0, RESPONSELEN);
memset(passphrase_old, 0, PASSPHRASELEN + 1);
memset(passphrase_new, 0, PASSPHRASELEN + 1);
free(new_2nd_factor);
free(payload);
return rc;
}
// vim: set syntax=c: