/*
* (C) 2014-2024 by Christian Hesse <mail@eworm.de>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY 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 <https://www.gnu.org/licenses/>.
*
*/
#define _GNU_SOURCE
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/random.h>
#include <sys/stat.h>
#include <termios.h>
#include <unistd.h>
#include <systemd/sd-daemon.h>
#include <iniparser/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
#define MAX2FLEN CHALLENGELEN / 2
const static char optstring[] = "hn:Ns:SV";
const static struct option options_long[] = {
/* name has_arg flag val */
{ "help", no_argument, NULL, 'h' },
{ "2nd-factor", required_argument, NULL, 's' },
{ "ask-2nd-factor", no_argument, NULL, 'S' },
{ "new-2nd-factor", required_argument, NULL, 'n' },
{ "ask-new-2nd-factor", no_argument, NULL, 'N' },
{ "version", no_argument, NULL, 'V' },
{ 0, 0, 0, 0 }
};
char * ask_secret(const char * text) {
struct termios tp, tp_save;
char * factor = NULL;
size_t len;
ssize_t readlen;
bool onTerminal = false;
/* get terminal properties */
if (tcgetattr(STDIN_FILENO, &tp) == 0) {
onTerminal = true;
tp_save = tp;
/* disable echo on terminal */
tp.c_lflag &= ~ECHO;
if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &tp) < 0) {
fprintf(stderr, "Failed setting terminal attributes.\n");
return NULL;
}
printf("Please give %s:", text);
}
readlen = getline(&factor, &len, stdin);
factor[readlen - 1] = '\0';
if (onTerminal == true) {
putchar('\n');
/* restore terminal */
if (tcsetattr(STDIN_FILENO, TCSANOW, &tp_save) < 0) {
fprintf(stderr, "Failed to restore terminal attributes.\n");
free(factor);
return NULL;
}
}
return factor;
}
int main(int argc, char **argv) {
unsigned int version = 0, help = 0, challenge_int[CHALLENGELEN];
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;
int i;
size_t len;
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;
char * passphrase = NULL;
/* keyutils */
key_serial_t key = -1;
void * payload = NULL;
char * second_factor = NULL, * new_2nd_factor = NULL, * new_2nd_factor_verify = NULL;
/* 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':
case 'N':
if (new_2nd_factor != NULL) {
fprintf(stderr, "We already have a new second factor. Did you specify it twice?\n");
goto out10;
}
if (optarg == NULL) { /* N */
if ((new_2nd_factor = ask_secret("new second factor")) == NULL)
goto out10;
if ((new_2nd_factor_verify = ask_secret("new second factor for verification")) == NULL)
goto out10;
if (strcmp(new_2nd_factor, new_2nd_factor_verify) != 0) {
fprintf(stderr, "Verification failed, given strings do not match.\n");
goto out10;
}
} else { /* n */
new_2nd_factor = strdup(optarg);
memset(optarg, '*', strlen(optarg));
}
break;
case 's':
case 'S':
if (second_factor != NULL) {
fprintf(stderr, "We already have a second factor. Did you specify it twice?\n");
goto out10;
}
if (optarg == NULL) { /* S */
second_factor = ask_secret("current second factor");
} else { /* s */
second_factor = 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|--help] [-n|--new-2nd-factor <new-2nd-factor>] [-N|--ask-new-2nd-factor]\n"
" [-s|--2nd-factor <2nd-factor>] [-S|--ask-2nd-factor] [-V|--version]\n", argv[0]);
if (version > 0 || help > 0)
return EXIT_SUCCESS;
/* initialize static buffers */
memset(challenge_int, 0, CHALLENGELEN * sizeof(unsigned int));
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) {
fprintf(stderr, "Could not parse configuration file.\n");
goto out10;
}
if ((device_name = iniparser_getstring(ini, "general:" CONFDEVNAME, NULL)) == NULL) {
/* 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 (yk_init() == 0) {
perror("yk_init() failed");
goto out20;
}
if ((yk = yk_open_first_key()) == NULL) {
fprintf(stderr, "No Yubikey available.\n");
goto out30;
}
/* read the serial number from key */
if (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) {
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;
}
/* try to get a second factor */
if (iniparser_getboolean(ini, "general:" CONF2NDFACTOR, 0) > 0 &&
second_factor == NULL && new_2nd_factor == NULL) {
if (sd_notify(0, "READY=0\nSTATUS=Detecting systemd...") == 0)
fprintf(stderr, "Not running from systemd, you may have to give\n"
"second factor manually if required.\n");
else if ((key = keyctl_search(KEY_SPEC_USER_KEYRING, "user", "ykfde-2f", 0)) < 0)
/* get second factor from key store */
fprintf(stderr, "Failed requesting key. That's ok if you do not use\n"
"second factor. Give it manually if required.\n");
/* if we have a key id we have a key - so this should succeed */
if (key > -1) {
if (keyctl_read_alloc(key, &payload) < 0) {
perror("Failed reading payload from key");
goto out40;
}
second_factor = payload;
}
}
/* use an empty string if second_factor is still NULL */
if (second_factor == NULL)
second_factor = strdup("");
/* warn when second factor is not enabled in config */
if (iniparser_getboolean(ini, "general:" CONF2NDFACTOR, 0) == 0 &&
((second_factor != NULL && *second_factor != 0) ||
(new_2nd_factor != NULL && *new_2nd_factor != 0)))
fprintf(stderr, "Warning: Processing second factor, but not enabled in config!\n");
/* get random number - try random first, fall back to urandom
We generate an array of unsigned int, the use modulo to limit to printable
ASCII characters (32 to 127). */
if ((len = getrandom(challenge_int, CHALLENGELEN * sizeof(unsigned int), GRND_RANDOM|GRND_NONBLOCK)) != CHALLENGELEN * sizeof(unsigned int))
len += getrandom((void *)((size_t)challenge_int + len), CHALLENGELEN * sizeof(unsigned int) - len, 0);
for (i = 0; i < CHALLENGELEN; i++)
challenge_new[i] = (challenge_int[i] % (127 - 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 ((challengefiletmp = mkstemp(challengefiletmpname)) < 0) {
fprintf(stderr, "Could not open file %s for writing.\n", challengefiletmpname);
goto out40;
}
if (write(challengefiletmp, challenge_new, CHALLENGELEN) < 0) {
fprintf(stderr, "Failed to write challenge to file.\n");
goto out50;
}
if (fsync(challengefiletmp) < 0) {
fprintf(stderr, "Failed to sync file to disk.\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 : second_factor;
len = strlen(tmp);
memcpy(challenge_new, tmp, len < MAX2FLEN ? len : MAX2FLEN);
/* do challenge/response and encode to hex */
if (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) {
fprintf(stderr, "Device %s is invalid or inactive.\n", device_name);
goto out50;
}
/* initialize crypt device */
if (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) {
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 ((challengefile = open(challengefilename, O_RDONLY)) < 0) {
perror("Failed opening challenge file for reading");
goto out60;
}
if (read(challengefile, challenge_old, CHALLENGELEN) < 0) {
perror("Failed reading challenge from file");
goto out60;
}
challengefile = close(challengefile);
/* finished reading challenge */
/* copy the second factor */
len = strlen(second_factor);
memcpy(challenge_old, second_factor, len < MAX2FLEN ? len : MAX2FLEN);
/* do challenge/response and encode to hex */
if (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 (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 (renameat2(AT_FDCWD, challengefiletmpname, AT_FDCWD, challengefilename, RENAME_EXCHANGE) < 0) {
fprintf(stderr, "Failed to rename (exchange) challenge files.\n");
goto out60;
}
if (unlink(challengefiletmpname) < 0) {
fprintf(stderr, "Failed to delete old challenge file.\n");
goto out60;
}
} else { /* ck == CRYPT_SLOT_INACTIVE */
if ((passphrase = ask_secret("existing LUKS passphrase")) == NULL)
goto out60;
if (crypt_keyslot_add_by_passphrase(cryptdevice, luks_slot,
passphrase, strlen(passphrase),
passphrase_new, PASSPHRASELEN) < 0) {
fprintf(stderr, "Could not add passphrase for key slot %d.\n", luks_slot);
goto out60;
}
if (rename(challengefiletmpname, challengefilename) < 0) {
fprintf(stderr, "Failed to rename new challenge file.\n");
goto out60;
}
}
sd_notify(0, "READY=1\nSTATUS=All done.");
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) == 0)
perror("yk_close_key() failed");
out30:
/* release Yubikey */
if (yk_release() == 0)
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_int, 0, CHALLENGELEN * sizeof(unsigned int));
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(passphrase);
free(new_2nd_factor_verify);
free(new_2nd_factor);
free(second_factor);
return rc;
}
// vim: set syntax=c: