From 40a0f31f1838d4774ebd960640bfb230dc562ea1 Mon Sep 17 00:00:00 2001 From: Christian Hesse Date: Sat, 16 Jan 2016 02:13:22 +0100 Subject: We have support for second factor. Yeah! --- udev/Makefile | 2 +- udev/ykfde.c | 234 ++++++++++++++++++++++++++++++++++++---------------------- 2 files changed, 148 insertions(+), 88 deletions(-) (limited to 'udev') diff --git a/udev/Makefile b/udev/Makefile index b2b8994..2ee1319 100644 --- a/udev/Makefile +++ b/udev/Makefile @@ -8,7 +8,7 @@ CFLAGS += -std=c11 -O2 -fpic -pie -Wall -Werror all: ykfde ykfde: ykfde.c ../config.h - $(CC) $(CFLAGS) -lykpers-1 -lyubikey -liniparser $(LDFLAGS) -o ykfde ykfde.c + $(CC) $(CFLAGS) -liniparser -lkeyutils -lykpers-1 -lyubikey $(LDFLAGS) -o ykfde ykfde.c install: ykfde $(INSTALL) -D -m0755 ykfde $(DESTDIR)/usr/lib/udev/ykfde diff --git a/udev/ykfde.c b/udev/ykfde.c index bf53eb4..9e0d1d3 100644 --- a/udev/ykfde.c +++ b/udev/ykfde.c @@ -5,7 +5,7 @@ * of the GNU General Public License, incorporated herein by reference. * * compile with: - * $ gcc -o ykfde ykfde.c -lykpers-1 -lyubikey -liniparser + * $ gcc -o ykfde ykfde.c -liniparser -lkeyutils -lykpers-1 -lyubikey * * test with: * $ systemd-ask-password --no-tty "Please enter passphrase for disk foobar..." @@ -15,36 +15,49 @@ #include #include #include +#include #include #include #include #include -#include #include -#include #include #include #include #include #include +#include + +#include + #include #include #include -#include - #include "../config.h" -#define EVENT_SIZE (sizeof (struct inotify_event)) -#define EVENT_BUF_LEN (1024 * (EVENT_SIZE + 16)) - -#define CHALLENGELEN 64 +/* 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 ASK_PATH "/run/systemd/ask-password/" #define ASK_MESSAGE "Please enter passphrase for disk" +#define PID_PATH "/run/ykfde.pid" + +void received_signal(int signal) { + /* Do nothing, just interrupt the sleep. */ + return; +} static int send_on_socket(int fd, const char *socket_name, const void *packet, size_t size) { union { @@ -64,50 +77,121 @@ static int send_on_socket(int fd, const char *socket_name, const void *packet, s return EXIT_SUCCESS; } -static int try_answer(char * ask_file, char * response) { +static int try_answer(YK_KEY * yk, uint8_t slot, const char * ask_file, char * challenge) { int8_t rc = EXIT_FAILURE; dictionary * ini; const char * ask_message, * ask_socket; int fd_askpass; + char response[RESPONSELEN], + passphrase[PASSPHRASELEN + 1], + passphrase_askpass[PASSPHRASELEN + 2]; + /* keyutils */ + key_serial_t key; + void * payload = NULL; + size_t plen; + + memset(response, 0, RESPONSELEN); + memset(passphrase, 0, PASSPHRASELEN + 1); + memset(passphrase_askpass, 0, PASSPHRASELEN + 2); + + /* get second factor from key store + * if this fails it is not critical... possibly we just do not + * use second factor */ + key = request_key("user", "ykfde-2f", NULL, 0); + + if (key > 0) { + /* 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 out1; + } + + /* we replace part of the challenge with the second factor */ + plen = strlen(payload); + memcpy(challenge, payload, plen < CHALLENGELEN / 2 ? plen : CHALLENGELEN / 2); + + free(payload); + } + + /* do challenge/response and encode to hex */ + if ((rc = yk_challenge_response(yk, slot, true, + CHALLENGELEN, (unsigned char *) challenge, + RESPONSELEN, (unsigned char *) response)) < 0) { + perror("yk_challenge_response() failed"); + goto out1; + } + yubikey_hex_encode((char *) passphrase, (char *) response, SHA1_DIGEST_SIZE); + + /* add key to kernel key store */ + if ((key = add_key("user", "cryptsetup", passphrase, PASSPHRASELEN, KEY_SPEC_USER_KEYRING)) > 0) { + if (keyctl_set_timeout(key, 150) < 0) + perror("keyctl_set_timeout() failed"); + } else + perror("add_key() failed"); + + /* key is placed, no ask file... quit here */ + if (ask_file == NULL) { + rc = key > 0 ? EXIT_SUCCESS : EXIT_FAILURE; + goto out1; + } - if ((ini = iniparser_load(ask_file)) == NULL) + if ((ini = iniparser_load(ask_file)) == NULL) { + rc = EXIT_FAILURE; perror("cannot parse file"); + goto out1; + } ask_message = iniparser_getstring(ini, "Ask:Message", NULL); - if (strncmp(ask_message, ASK_MESSAGE, strlen(ASK_MESSAGE)) != 0) - goto out1; + if (strncmp(ask_message, ASK_MESSAGE, strlen(ASK_MESSAGE)) != 0) { + rc = EXIT_FAILURE; + goto out2; + } - ask_socket = iniparser_getstring(ini, "Ask:Socket", NULL); + if ((ask_socket = iniparser_getstring(ini, "Ask:Socket", NULL)) == NULL) { + rc = EXIT_FAILURE; + perror("Could not get socket name"); + goto out2; + } + + sprintf(passphrase_askpass, "+%s", passphrase); if ((fd_askpass = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0)) < 0) { + rc = EXIT_FAILURE; perror("socket() failed"); - goto out1; + goto out2; } - if (send_on_socket(fd_askpass, ask_socket, response, PASSPHRASELEN + 1) < 0) { + if (send_on_socket(fd_askpass, ask_socket, passphrase_askpass, PASSPHRASELEN + 1) < 0) { + rc = EXIT_FAILURE; perror("send_on_socket() failed"); - goto out2; + goto out3; } rc = EXIT_SUCCESS; -out2: +out3: close(fd_askpass); -out1: +out2: iniparser_freedict(ini); +out1: + /* wipe response (cleartext password!) from memory */ + memset(response, 0, RESPONSELEN); + memset(passphrase, 0, PASSPHRASELEN + 1); + memset(passphrase_askpass, 0, PASSPHRASELEN + 2); + return rc; } int main(int argc, char **argv) { int8_t rc = EXIT_FAILURE; + FILE *pidfile; /* Yubikey */ YK_KEY * yk; uint8_t slot = SLOT_CHAL_HMAC2; unsigned int serial = 0; - char response[RESPONSELEN], passphrase[PASSPHRASELEN + 1], passphrase_askpass[PASSPHRASELEN + 2]; /* iniparser */ dictionary * ini; char section_ykslot[10 /* unsigned int in char */ + 1 + sizeof(CONFYKSLOT) + 1]; @@ -118,17 +202,32 @@ int main(int argc, char **argv) { /* read dir */ DIR * dir; struct dirent * ent; - /* inotify */ - struct inotify_event * event; - int fd_inotify, watch, length, i = 0; - char buffer[EVENT_BUF_LEN]; -#if DEBUG +#ifdef DEBUG /* reopening stderr to /dev/console may help debugging... */ - freopen("/dev/console", "w", stderr); + FILE * tmp = freopen("/dev/console", "w", stderr); + (void) tmp; #endif - memset(challenge, 0, CHALLENGELEN); + if ((pidfile = fopen(PID_PATH, "w")) != NULL) { + if (fprintf(pidfile, "%d", getpid()) < 0) { + rc = EXIT_FAILURE; + perror("Failed writing pid"); + fclose(pidfile); + goto out10; + } + fclose(pidfile); + } else { + rc = EXIT_FAILURE; + perror("Failed opening pid file"); + goto out10; + } + + /* connect to signal */ + signal(SIGUSR1, received_signal); + + /* initialize static memory */ + memset(challenge, 0, CHALLENGELEN + 1); /* init and open first Yubikey */ if ((rc = yk_init()) < 0) { @@ -143,7 +242,7 @@ int main(int argc, char **argv) { } /* read the serial number from key */ - if((rc = !yk_get_serial(yk, 0, 0, &serial)) < 0) { + if ((rc = yk_get_serial(yk, 0, 0, &serial)) < 0) { perror("yk_get_serial() failed"); goto out30; } @@ -151,8 +250,10 @@ int main(int argc, char **argv) { sprintf(challengefilename, CHALLENGEDIR "/challenge-%d", serial); /* check if challenge file exists */ - if (access(challengefilename, R_OK) == -1) + if (access(challengefilename, R_OK) == -1) { + rc = EXIT_FAILURE; goto out30; + } /* read challenge from file */ if ((rc = challengefile = open(challengefilename, O_RDONLY)) < 0) { @@ -162,10 +263,8 @@ int main(int argc, char **argv) { if ((rc = read(challengefile, challenge, CHALLENGELEN)) < 0) { perror("Failed reading challenge from file"); - goto out50; + goto out40; } - challengefile = close(challengefile); - /* finished reading challenge */ /* try to read config file * if anything here fails we do not care... slot 2 is the default */ @@ -193,75 +292,39 @@ int main(int argc, char **argv) { iniparser_freedict(ini); } - memset(response, 0, RESPONSELEN); - memset(passphrase, 0, PASSPHRASELEN + 1); - - /* do challenge/response and encode to hex */ - if ((rc = yk_challenge_response(yk, slot, true, - CHALLENGELEN, (unsigned char *)challenge, - RESPONSELEN, (unsigned char *)response)) < 0) { - perror("yk_challenge_response() failed"); - goto out50; - } - yubikey_hex_encode((char *)passphrase, (char *)response, 20); - - sprintf(passphrase_askpass, "+%s", passphrase); - /* change to directory so we do not have to assemble complete/absolute path */ if ((rc = chdir(ASK_PATH)) != 0) { perror("chdir() failed"); - goto out50; - } - - /* creating the INOTIFY instance and add ASK_PATH directory into watch list */ - if ((rc = fd_inotify = inotify_init()) < 0) { - perror("inotify_init() failed"); - goto out50; + goto out40; } - 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. */ + /* Is the request already there? */ if ((dir = opendir(ASK_PATH)) != NULL) { while ((ent = readdir(dir)) != NULL) { if (strncmp(ent->d_name, "ask.", 4) == 0) { - if ((rc = try_answer(ent->d_name, passphrase_askpass)) == EXIT_SUCCESS) - goto out70; + if ((rc = try_answer(yk, slot, ent->d_name, challenge)) == EXIT_SUCCESS) + goto out50; } } } else { rc = EXIT_FAILURE; perror ("opendir() failed"); - goto out60; + goto out50; } - /* read to determine the event change happens. Actually this read blocks until the change event occurs */ - if ((rc = length = read(fd_inotify, buffer, EVENT_BUF_LEN)) < 0) { - perror("read() failed"); - goto out70; - } + /* Wait for 90 seconds. + * The user has this time to enter his second factor, resulting in + * SIGUSR1 being sent to us. */ + sleep(90); - /* 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 ((rc = try_answer(event->name, passphrase_askpass)) == EXIT_SUCCESS) - goto out70; - i += EVENT_SIZE + event->len; - } + /* try again, but for key store this time */ + rc = try_answer(yk, slot, NULL, challenge); -out70: +out50: /* close dir */ closedir(dir); -out60: - /* remove inotify watch and remove file handle */ - inotify_rm_watch(fd_inotify, watch); - close(fd_inotify); - -out50: +out40: /* close the challenge file */ if (challengefile) close(challengefile); @@ -270,12 +333,6 @@ out50: unlink(challengefilename); out30: - /* wipe response (cleartext password!) from memory */ - memset(challenge, 0, CHALLENGELEN); - memset(response, 0, RESPONSELEN); - memset(passphrase, 0, PASSPHRASELEN + 1); - memset(passphrase_askpass, 0, PASSPHRASELEN + 2); - /* close Yubikey */ if (yk_close_key(yk) < 0) perror("yk_close_key() failed"); @@ -286,6 +343,9 @@ out20: perror("yk_release() failed"); out10: + /* wipe challenge from memory */ + memset(challenge, 0, CHALLENGELEN + 1); + return rc; } -- cgit v1.2.3-54-g00ecf