static void test_load_chalresp_state(void) {
int ret;
FILE *file = tmpfile();
CR_STATE state;
memset(&state, 0, sizeof(state));
fprintf(file, "v2:%s:%s:%s:%d:%d\n", CHALLENGE1, RESPONSE1, SALT1, 1000, 2);
rewind(file);
ret = load_chalresp_state(file, &state, true);
assert(ret == 1);
assert(state.iterations == 1000);
assert(state.slot == 2);
assert(state.challenge_len == CR_CHALLENGE_SIZE);
assert(state.response_len == CR_RESPONSE_SIZE);
assert(state.salt_len == CR_SALT_SIZE);
rewind(file);
memset(&state, 0, sizeof(state));
fprintf(file, "v1:%s:%s:%d\n", CHALLENGE2, RESPONSE2, 1);
rewind(file);
ret = load_chalresp_state(file, &state, true);
assert(ret == 1);
assert(state.iterations == CR_DEFAULT_ITERATIONS);
assert(state.slot == 1);
assert(state.challenge_len == CR_CHALLENGE_SIZE);
assert(state.response_len == CR_RESPONSE_SIZE);
assert(state.salt_len == 0);
rewind(file);
/* slot 3 should fail.. */
fprintf(file, "v2:%s:%s:%s:%d:%d\n", CHALLENGE1, RESPONSE1, SALT1, 1000, 3);
rewind(file);
ret = load_chalresp_state(file, &state, true);
assert(ret == 0);
fclose(file);
}
static int
do_challenge_response(pam_handle_t *pamh, struct cfg *cfg, const char *username)
{
char *userfile = NULL, *tmpfile = NULL;
FILE *f = NULL;
unsigned char buf[CR_RESPONSE_SIZE + 16], response_hex[CR_RESPONSE_SIZE * 2 + 1];
int ret;
unsigned int flags = 0;
unsigned int response_len = 0;
unsigned int expect_bytes = 0;
YK_KEY *yk = NULL;
CR_STATE state;
int len;
char *errstr = NULL;
ret = PAM_AUTH_ERR;
flags |= YK_FLAG_MAYBLOCK;
if (! init_yubikey(&yk)) {
D(("Failed initializing YubiKey"));
goto out;
}
if (! check_firmware_version(yk, false, true)) {
D(("YubiKey does not support Challenge-Response (version 2.2 required)"));
goto out;
}
if (! get_user_challenge_file (yk, cfg->chalresp_path, username, &userfile)) {
D(("Failed getting user challenge file for user %s", username));
goto out;
}
DBG(("Loading challenge from file %s", userfile));
/* XXX should drop root privileges before opening file in user's home directory */
f = fopen(userfile, "r");
if (! load_chalresp_state(f, &state))
goto out;
if (fclose(f) < 0) {
f = NULL;
goto out;
}
if (! challenge_response(yk, state.slot, state.challenge, state.challenge_len,
true, flags, false,
buf, sizeof(buf), &response_len)) {
D(("Challenge-response FAILED"));
goto out;
}
/*
* Check YubiKey response against the expected response
*/
yubikey_hex_encode(response_hex, (char *)buf, response_len);
if (memcmp(buf, state.response, response_len) == 0) {
ret = PAM_SUCCESS;
} else {
D(("Unexpected C/R response : %s", response_hex));
goto out;
}
DBG(("Got the expected response, generating new challenge (%i bytes).", CR_CHALLENGE_SIZE));
errstr = "Error generating new challenge, please check syslog or contact your system administrator";
if (generate_random(state.challenge, sizeof(state.challenge))) {
D(("Failed generating new challenge!"));
goto out;
}
errstr = "Error communicating with Yubikey, please check syslog or contact your system administrator";
if (! challenge_response(yk, state.slot, state.challenge, CR_CHALLENGE_SIZE,
true, flags, false,
buf, sizeof(buf), &response_len)) {
D(("Second challenge-response FAILED"));
goto out;
}
/* the yk_* functions leave 'junk' in errno */
errno = 0;
/*
* Write the challenge and response we will expect the next time to the state file.
*/
if (response_len > sizeof(state.response)) {
D(("Got too long response ??? (%i/%i)", response_len, sizeof(state.response)));
goto out;
}
memcpy (state.response, buf, response_len);
state.response_len = response_len;
/* Write out the new file */
tmpfile = malloc(strlen(userfile) + 1 + 4);
if (! tmpfile)
goto out;
strcpy(tmpfile, userfile);
strcat(tmpfile, ".tmp");
f = fopen(tmpfile, "w");
if (! f)
goto out;
errstr = "Error updating Yubikey challenge, please check syslog or contact your system administrator";
if (! write_chalresp_state (f, &state))
goto out;
if (fclose(f) < 0) {
f = NULL;
goto out;
}
f = NULL;
if (rename(tmpfile, userfile) < 0) {
goto out;
}
DBG(("Challenge-response success!"));
errstr = NULL;
out:
if (yk_errno) {
if (yk_errno == YK_EUSBERR) {
syslog(LOG_ERR, "USB error: %s", yk_usb_strerror());
D(("USB error: %s", yk_usb_strerror()));
} else {
syslog(LOG_ERR, "Yubikey core error: %s", yk_strerror(yk_errno));
D(("Yubikey core error: %s", yk_strerror(yk_errno)));
}
}
if (errstr)
display_error(pamh, errstr);
if (errno) {
syslog(LOG_ERR, "Challenge response failed: %s", strerror(errno));
D(("Challenge response failed: %s", strerror(errno)));
}
if (yk)
yk_close_key(yk);
yk_release();
if (f)
fclose(f);
free(userfile);
free(tmpfile);
return ret;
}
static int
do_challenge_response(pam_handle_t *pamh, struct cfg *cfg, const char *username)
{
char *userfile = NULL, *tmpfile = NULL;
FILE *f = NULL;
char buf[CR_RESPONSE_SIZE + 16], response_hex[CR_RESPONSE_SIZE * 2 + 1];
int ret, fd;
unsigned int flags = 0;
unsigned int response_len = 0;
YK_KEY *yk = NULL;
CR_STATE state;
char *errstr = NULL;
struct passwd *p;
struct stat st;
ret = PAM_AUTH_ERR;
flags |= YK_FLAG_MAYBLOCK;
if (! init_yubikey(&yk)) {
D(("Failed initializing YubiKey"));
goto out;
}
if (! check_firmware_version(yk, false, true)) {
D(("YubiKey does not support Challenge-Response (version 2.2 required)"));
goto out;
}
if (! get_user_challenge_file (yk, cfg->chalresp_path, username, &userfile)) {
D(("Failed getting user challenge file for user %s", username));
goto out;
}
DBG(("Loading challenge from file %s", userfile));
p = getpwnam (username);
if (p == NULL) {
DBG (("getpwnam: %s", strerror(errno)));
goto out;
}
/* Drop privileges before opening user file. */
if (drop_privileges(p, pamh) < 0) {
D (("could not drop privileges"));
goto out;
}
fd = open(userfile, O_RDONLY, 0);
if (fd < 0) {
DBG (("Cannot open file: %s (%s)", userfile, strerror(errno)));
goto out;
}
if (fstat(fd, &st) < 0) {
DBG (("Cannot stat file: %s (%s)", userfile, strerror(errno)));
close(fd);
goto out;
}
if (!S_ISREG(st.st_mode)) {
DBG (("%s is not a regular file", userfile));
close(fd);
goto out;
}
f = fdopen(fd, "r");
if (f == NULL) {
DBG (("fdopen: %s", strerror(errno)));
close(fd);
goto out;
}
if (! load_chalresp_state(f, &state, cfg->debug))
goto out;
if (fclose(f) < 0) {
f = NULL;
goto out;
}
f = NULL;
if (restore_privileges(pamh) < 0) {
DBG (("could not restore privileges"));
goto out;
}
if (! challenge_response(yk, state.slot, state.challenge, state.challenge_len,
true, flags, false,
buf, sizeof(buf), &response_len)) {
D(("Challenge-response FAILED"));
goto out;
}
/*
* Check YubiKey response against the expected response
*/
yubikey_hex_encode(response_hex, buf, response_len);
if (memcmp(buf, state.response, response_len) == 0) {
ret = PAM_SUCCESS;
} else {
D(("Unexpected C/R response : %s", response_hex));
goto out;
}
DBG(("Got the expected response, generating new challenge (%i bytes).", CR_CHALLENGE_SIZE));
errstr = "Error generating new challenge, please check syslog or contact your system administrator";
if (generate_random(state.challenge, sizeof(state.challenge))) {
D(("Failed generating new challenge!"));
goto out;
}
errstr = "Error communicating with Yubikey, please check syslog or contact your system administrator";
if (! challenge_response(yk, state.slot, state.challenge, CR_CHALLENGE_SIZE,
true, flags, false,
buf, sizeof(buf), &response_len)) {
D(("Second challenge-response FAILED"));
goto out;
}
/* There is a bug that makes the YubiKey 2.2 send the same response for all challenges
unless HMAC_LT64 is set, check for that here */
if (memcmp(buf, state.response, response_len) == 0) {
errstr = "Same response for second challenge, YubiKey should be reconfigured with the option HMAC_LT64";
goto out;
}
/* the yk_* functions leave 'junk' in errno */
errno = 0;
/*
* Write the challenge and response we will expect the next time to the state file.
*/
if (response_len > sizeof(state.response)) {
D(("Got too long response ??? (%u/%lu)", response_len, (unsigned long) sizeof(state.response)));
goto out;
}
memcpy (state.response, buf, response_len);
state.response_len = response_len;
/* Drop privileges before creating new challenge file. */
if (drop_privileges(p, pamh) < 0) {
D (("could not drop privileges"));
goto out;
}
/* Write out the new file */
tmpfile = malloc(strlen(userfile) + 1 + 4);
if (! tmpfile)
goto out;
strcpy(tmpfile, userfile);
strcat(tmpfile, ".tmp");
fd = open(tmpfile, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (fd < 0) {
DBG (("Cannot open file: %s (%s)", tmpfile, strerror(errno)));
goto out;
}
f = fdopen(fd, "w");
if (! f) {
close(fd);
goto out;
}
errstr = "Error updating Yubikey challenge, please check syslog or contact your system administrator";
if (! write_chalresp_state (f, &state))
goto out;
if (fclose(f) < 0) {
f = NULL;
goto out;
}
f = NULL;
if (rename(tmpfile, userfile) < 0) {
goto out;
}
if (restore_privileges(pamh) < 0) {
DBG (("could not restore privileges"));
goto out;
}
DBG(("Challenge-response success!"));
errstr = NULL;
errno = 0;
out:
if (yk_errno) {
if (yk_errno == YK_EUSBERR) {
syslog(LOG_ERR, "USB error: %s", yk_usb_strerror());
D(("USB error: %s", yk_usb_strerror()));
} else {
syslog(LOG_ERR, "Yubikey core error: %s", yk_strerror(yk_errno));
D(("Yubikey core error: %s", yk_strerror(yk_errno)));
}
}
if (errstr)
display_error(pamh, errstr);
if (errno) {
syslog(LOG_ERR, "Challenge response failed: %s", strerror(errno));
D(("Challenge response failed: %s", strerror(errno)));
}
if (yk)
yk_close_key(yk);
yk_release();
if (f)
fclose(f);
free(userfile);
free(tmpfile);
return ret;
}
