From 0498dd512161b7fb07e703e03bc9b8ca8b3dd400 Mon Sep 17 00:00:00 2001 From: Christian Hesse Date: Mon, 22 Dec 2014 22:03:21 +0100 Subject: replace shell script with C code, and many more * place bin/ykfde with C source code bin/ykfde.c * challenge/response can be updated in place WARNING: This required config file syntax change! * updates and simplification to udev/ykfde * a lot more... Signed-off-by: Christian Hesse --- bin/ykfde.c | 280 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 280 insertions(+) create mode 100644 bin/ykfde.c (limited to 'bin/ykfde.c') diff --git a/bin/ykfde.c b/bin/ykfde.c new file mode 100644 index 0000000..43735d5 --- /dev/null +++ b/bin/ykfde.c @@ -0,0 +1,280 @@ +/* + * (C) 2014 by Christian Hesse + * + * 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 +#include +#include +#include +#include +#include + +#include + +#include +#include +#include + +#include + +/* 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 + +#define CONFIGFILE "/etc/ykfde.conf" +#define CHALLENGEDIR "/etc/ykfde.d/" +#define CONFYKSLOT "yk slot" +#define CONFLUKSSLOT "luks slot" +#define CONFDEVNAME "device name" + +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: -- cgit v1.2.3-54-g00ecf