zfs-builds-mm/zfs-2.0.0-rc6/contrib/pam_zfs_key/pam_zfs_key.c

742 lines
18 KiB
C
Raw Normal View History

2020-11-15 11:35:49 +01:00
/*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the <organization> nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright (c) 2020, Felix Dörre
* All rights reserved.
*/
#include <sys/dsl_crypt.h>
#include <sys/byteorder.h>
#include <libzfs.h>
#include <syslog.h>
#include <sys/zio_crypt.h>
#include <openssl/evp.h>
#define PAM_SM_AUTH
#define PAM_SM_PASSWORD
#define PAM_SM_SESSION
#include <security/pam_modules.h>
#if defined(__linux__)
#include <security/pam_ext.h>
#elif defined(__FreeBSD__)
#include <security/pam_appl.h>
static void
pam_syslog(pam_handle_t *pamh, int loglevel, const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
vsyslog(loglevel, fmt, args);
va_end(args);
}
#endif
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/wait.h>
#include <pwd.h>
#include <sys/mman.h>
static const char PASSWORD_VAR_NAME[] = "pam_zfs_key_authtok";
static libzfs_handle_t *g_zfs;
static void destroy_pw(pam_handle_t *pamh, void *data, int errcode);
typedef struct {
size_t len;
char *value;
} pw_password_t;
static pw_password_t *
alloc_pw_size(size_t len)
{
pw_password_t *pw = malloc(sizeof (pw_password_t));
if (!pw) {
return (NULL);
}
pw->len = len;
pw->value = malloc(len);
if (!pw->value) {
free(pw);
return (NULL);
}
mlock(pw->value, pw->len);
return (pw);
}
static pw_password_t *
alloc_pw_string(const char *source)
{
pw_password_t *pw = malloc(sizeof (pw_password_t));
if (!pw) {
return (NULL);
}
pw->len = strlen(source) + 1;
pw->value = malloc(pw->len);
if (!pw->value) {
free(pw);
return (NULL);
}
mlock(pw->value, pw->len);
memcpy(pw->value, source, pw->len);
return (pw);
}
static void
pw_free(pw_password_t *pw)
{
bzero(pw->value, pw->len);
munlock(pw->value, pw->len);
free(pw->value);
free(pw);
}
static pw_password_t *
pw_fetch(pam_handle_t *pamh)
{
const char *token;
if (pam_get_authtok(pamh, PAM_AUTHTOK, &token, NULL) != PAM_SUCCESS) {
pam_syslog(pamh, LOG_ERR,
"couldn't get password from PAM stack");
return (NULL);
}
if (!token) {
pam_syslog(pamh, LOG_ERR,
"token from PAM stack is null");
return (NULL);
}
return (alloc_pw_string(token));
}
static const pw_password_t *
pw_fetch_lazy(pam_handle_t *pamh)
{
pw_password_t *pw = pw_fetch(pamh);
if (pw == NULL) {
return (NULL);
}
int ret = pam_set_data(pamh, PASSWORD_VAR_NAME, pw, destroy_pw);
if (ret != PAM_SUCCESS) {
pw_free(pw);
pam_syslog(pamh, LOG_ERR, "pam_set_data failed");
return (NULL);
}
return (pw);
}
static const pw_password_t *
pw_get(pam_handle_t *pamh)
{
const pw_password_t *authtok = NULL;
int ret = pam_get_data(pamh, PASSWORD_VAR_NAME,
(const void**)(&authtok));
if (ret == PAM_SUCCESS)
return (authtok);
if (ret == PAM_NO_MODULE_DATA)
return (pw_fetch_lazy(pamh));
pam_syslog(pamh, LOG_ERR, "password not available");
return (NULL);
}
static int
pw_clear(pam_handle_t *pamh)
{
int ret = pam_set_data(pamh, PASSWORD_VAR_NAME, NULL, NULL);
if (ret != PAM_SUCCESS) {
pam_syslog(pamh, LOG_ERR, "clearing password failed");
return (-1);
}
return (0);
}
static void
destroy_pw(pam_handle_t *pamh, void *data, int errcode)
{
if (data != NULL) {
pw_free((pw_password_t *)data);
}
}
static int
pam_zfs_init(pam_handle_t *pamh)
{
int error = 0;
if ((g_zfs = libzfs_init()) == NULL) {
error = errno;
pam_syslog(pamh, LOG_ERR, "Zfs initialization error: %s",
libzfs_error_init(error));
}
return (error);
}
static void
pam_zfs_free(void)
{
libzfs_fini(g_zfs);
}
static pw_password_t *
prepare_passphrase(pam_handle_t *pamh, zfs_handle_t *ds,
const char *passphrase, nvlist_t *nvlist)
{
pw_password_t *key = alloc_pw_size(WRAPPING_KEY_LEN);
if (!key) {
return (NULL);
}
uint64_t salt;
uint64_t iters;
if (nvlist != NULL) {
int fd = open("/dev/urandom", O_RDONLY);
if (fd < 0) {
pw_free(key);
return (NULL);
}
int bytes_read = 0;
char *buf = (char *)&salt;
size_t bytes = sizeof (uint64_t);
while (bytes_read < bytes) {
ssize_t len = read(fd, buf + bytes_read, bytes
- bytes_read);
if (len < 0) {
close(fd);
pw_free(key);
return (NULL);
}
bytes_read += len;
}
close(fd);
if (nvlist_add_uint64(nvlist,
zfs_prop_to_name(ZFS_PROP_PBKDF2_SALT), salt)) {
pam_syslog(pamh, LOG_ERR,
"failed to add salt to nvlist");
pw_free(key);
return (NULL);
}
iters = DEFAULT_PBKDF2_ITERATIONS;
if (nvlist_add_uint64(nvlist, zfs_prop_to_name(
ZFS_PROP_PBKDF2_ITERS), iters)) {
pam_syslog(pamh, LOG_ERR,
"failed to add iters to nvlist");
pw_free(key);
return (NULL);
}
} else {
salt = zfs_prop_get_int(ds, ZFS_PROP_PBKDF2_SALT);
iters = zfs_prop_get_int(ds, ZFS_PROP_PBKDF2_ITERS);
}
salt = LE_64(salt);
if (!PKCS5_PBKDF2_HMAC_SHA1((char *)passphrase,
strlen(passphrase), (uint8_t *)&salt,
sizeof (uint64_t), iters, WRAPPING_KEY_LEN,
(uint8_t *)key->value)) {
pam_syslog(pamh, LOG_ERR, "pbkdf failed");
pw_free(key);
return (NULL);
}
return (key);
}
static int
is_key_loaded(pam_handle_t *pamh, const char *ds_name)
{
zfs_handle_t *ds = zfs_open(g_zfs, ds_name, ZFS_TYPE_FILESYSTEM);
if (ds == NULL) {
pam_syslog(pamh, LOG_ERR, "dataset %s not found", ds_name);
return (-1);
}
int keystatus = zfs_prop_get_int(ds, ZFS_PROP_KEYSTATUS);
zfs_close(ds);
return (keystatus != ZFS_KEYSTATUS_UNAVAILABLE);
}
static int
change_key(pam_handle_t *pamh, const char *ds_name,
const char *passphrase)
{
zfs_handle_t *ds = zfs_open(g_zfs, ds_name, ZFS_TYPE_FILESYSTEM);
if (ds == NULL) {
pam_syslog(pamh, LOG_ERR, "dataset %s not found", ds_name);
return (-1);
}
nvlist_t *nvlist = fnvlist_alloc();
pw_password_t *key = prepare_passphrase(pamh, ds, passphrase, nvlist);
if (key == NULL) {
nvlist_free(nvlist);
zfs_close(ds);
return (-1);
}
if (nvlist_add_string(nvlist,
zfs_prop_to_name(ZFS_PROP_KEYLOCATION),
"prompt")) {
pam_syslog(pamh, LOG_ERR, "nvlist_add failed for keylocation");
pw_free(key);
nvlist_free(nvlist);
zfs_close(ds);
return (-1);
}
if (nvlist_add_uint64(nvlist,
zfs_prop_to_name(ZFS_PROP_KEYFORMAT),
ZFS_KEYFORMAT_PASSPHRASE)) {
pam_syslog(pamh, LOG_ERR, "nvlist_add failed for keyformat");
pw_free(key);
nvlist_free(nvlist);
zfs_close(ds);
return (-1);
}
int ret = lzc_change_key(ds_name, DCP_CMD_NEW_KEY, nvlist,
(uint8_t *)key->value, WRAPPING_KEY_LEN);
pw_free(key);
if (ret) {
pam_syslog(pamh, LOG_ERR, "change_key failed: %d", ret);
nvlist_free(nvlist);
zfs_close(ds);
return (-1);
}
nvlist_free(nvlist);
zfs_close(ds);
return (0);
}
static int
decrypt_mount(pam_handle_t *pamh, const char *ds_name,
const char *passphrase)
{
zfs_handle_t *ds = zfs_open(g_zfs, ds_name, ZFS_TYPE_FILESYSTEM);
if (ds == NULL) {
pam_syslog(pamh, LOG_ERR, "dataset %s not found", ds_name);
return (-1);
}
pw_password_t *key = prepare_passphrase(pamh, ds, passphrase, NULL);
if (key == NULL) {
zfs_close(ds);
return (-1);
}
int ret = lzc_load_key(ds_name, B_FALSE, (uint8_t *)key->value,
WRAPPING_KEY_LEN);
pw_free(key);
if (ret) {
pam_syslog(pamh, LOG_ERR, "load_key failed: %d", ret);
zfs_close(ds);
return (-1);
}
ret = zfs_mount(ds, NULL, 0);
if (ret) {
pam_syslog(pamh, LOG_ERR, "mount failed: %d", ret);
zfs_close(ds);
return (-1);
}
zfs_close(ds);
return (0);
}
static int
unmount_unload(pam_handle_t *pamh, const char *ds_name)
{
zfs_handle_t *ds = zfs_open(g_zfs, ds_name, ZFS_TYPE_FILESYSTEM);
if (ds == NULL) {
pam_syslog(pamh, LOG_ERR, "dataset %s not found", ds_name);
return (-1);
}
int ret = zfs_unmount(ds, NULL, 0);
if (ret) {
pam_syslog(pamh, LOG_ERR, "zfs_unmount failed with: %d", ret);
zfs_close(ds);
return (-1);
}
ret = lzc_unload_key(ds_name);
if (ret) {
pam_syslog(pamh, LOG_ERR, "unload_key failed with: %d", ret);
zfs_close(ds);
return (-1);
}
zfs_close(ds);
return (0);
}
typedef struct {
char *homes_prefix;
char *runstatedir;
uid_t uid;
const char *username;
int unmount_and_unload;
} zfs_key_config_t;
static int
zfs_key_config_load(pam_handle_t *pamh, zfs_key_config_t *config,
int argc, const char **argv)
{
config->homes_prefix = strdup("rpool/home");
if (config->homes_prefix == NULL) {
pam_syslog(pamh, LOG_ERR, "strdup failure");
return (-1);
}
config->runstatedir = strdup(RUNSTATEDIR "/pam_zfs_key");
if (config->runstatedir == NULL) {
pam_syslog(pamh, LOG_ERR, "strdup failure");
free(config->homes_prefix);
return (-1);
}
const char *name;
if (pam_get_user(pamh, &name, NULL) != PAM_SUCCESS) {
pam_syslog(pamh, LOG_ERR,
"couldn't get username from PAM stack");
free(config->runstatedir);
free(config->homes_prefix);
return (-1);
}
struct passwd *entry = getpwnam(name);
if (!entry) {
free(config->runstatedir);
free(config->homes_prefix);
return (-1);
}
config->uid = entry->pw_uid;
config->username = name;
config->unmount_and_unload = 1;
for (int c = 0; c < argc; c++) {
if (strncmp(argv[c], "homes=", 6) == 0) {
free(config->homes_prefix);
config->homes_prefix = strdup(argv[c] + 6);
} else if (strncmp(argv[c], "runstatedir=", 12) == 0) {
free(config->runstatedir);
config->runstatedir = strdup(argv[c] + 12);
} else if (strcmp(argv[c], "nounmount") == 0) {
config->unmount_and_unload = 0;
}
}
return (0);
}
static void
zfs_key_config_free(zfs_key_config_t *config)
{
free(config->homes_prefix);
}
static char *
zfs_key_config_get_dataset(zfs_key_config_t *config)
{
size_t len = ZFS_MAX_DATASET_NAME_LEN;
size_t total_len = strlen(config->homes_prefix) + 1
+ strlen(config->username);
if (total_len > len) {
return (NULL);
}
char *ret = malloc(len + 1);
if (!ret) {
return (NULL);
}
ret[0] = 0;
strcat(ret, config->homes_prefix);
strcat(ret, "/");
strcat(ret, config->username);
return (ret);
}
static int
zfs_key_config_modify_session_counter(pam_handle_t *pamh,
zfs_key_config_t *config, int delta)
{
const char *runtime_path = config->runstatedir;
if (mkdir(runtime_path, S_IRWXU) != 0 && errno != EEXIST) {
pam_syslog(pamh, LOG_ERR, "Can't create runtime path: %d",
errno);
return (-1);
}
if (chown(runtime_path, 0, 0) != 0) {
pam_syslog(pamh, LOG_ERR, "Can't chown runtime path: %d",
errno);
return (-1);
}
if (chmod(runtime_path, S_IRWXU) != 0) {
pam_syslog(pamh, LOG_ERR, "Can't chmod runtime path: %d",
errno);
return (-1);
}
size_t runtime_path_len = strlen(runtime_path);
size_t counter_path_len = runtime_path_len + 1 + 10;
char *counter_path = malloc(counter_path_len + 1);
if (!counter_path) {
return (-1);
}
counter_path[0] = 0;
strcat(counter_path, runtime_path);
snprintf(counter_path + runtime_path_len, counter_path_len, "/%d",
config->uid);
const int fd = open(counter_path,
O_RDWR | O_CLOEXEC | O_CREAT | O_NOFOLLOW,
S_IRUSR | S_IWUSR);
free(counter_path);
if (fd < 0) {
pam_syslog(pamh, LOG_ERR, "Can't open counter file: %d", errno);
return (-1);
}
if (flock(fd, LOCK_EX) != 0) {
pam_syslog(pamh, LOG_ERR, "Can't lock counter file: %d", errno);
close(fd);
return (-1);
}
char counter[20];
char *pos = counter;
int remaining = sizeof (counter) - 1;
int ret;
counter[sizeof (counter) - 1] = 0;
while (remaining > 0 && (ret = read(fd, pos, remaining)) > 0) {
remaining -= ret;
pos += ret;
}
*pos = 0;
long int counter_value = strtol(counter, NULL, 10);
counter_value += delta;
if (counter_value < 0) {
counter_value = 0;
}
lseek(fd, 0, SEEK_SET);
if (ftruncate(fd, 0) != 0) {
pam_syslog(pamh, LOG_ERR, "Can't truncate counter file: %d",
errno);
close(fd);
return (-1);
}
snprintf(counter, sizeof (counter), "%ld", counter_value);
remaining = strlen(counter);
pos = counter;
while (remaining > 0 && (ret = write(fd, pos, remaining)) > 0) {
remaining -= ret;
pos += ret;
}
close(fd);
return (counter_value);
}
__attribute__((visibility("default")))
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
if (pw_fetch_lazy(pamh) == NULL) {
return (PAM_AUTH_ERR);
}
return (PAM_SUCCESS);
}
__attribute__((visibility("default")))
PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
return (PAM_SUCCESS);
}
__attribute__((visibility("default")))
PAM_EXTERN int
pam_sm_chauthtok(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
if (geteuid() != 0) {
pam_syslog(pamh, LOG_ERR,
"Cannot zfs_mount when not being root.");
return (PAM_PERM_DENIED);
}
zfs_key_config_t config;
if (zfs_key_config_load(pamh, &config, argc, argv) == -1) {
return (PAM_SERVICE_ERR);
}
if (config.uid < 1000) {
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}
{
if (pam_zfs_init(pamh) != 0) {
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
char *dataset = zfs_key_config_get_dataset(&config);
if (!dataset) {
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
int key_loaded = is_key_loaded(pamh, dataset);
if (key_loaded == -1) {
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
free(dataset);
pam_zfs_free();
if (! key_loaded) {
pam_syslog(pamh, LOG_ERR,
"key not loaded, returning try_again");
zfs_key_config_free(&config);
return (PAM_PERM_DENIED);
}
}
if ((flags & PAM_UPDATE_AUTHTOK) != 0) {
const pw_password_t *token = pw_get(pamh);
if (token == NULL) {
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
if (pam_zfs_init(pamh) != 0) {
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
char *dataset = zfs_key_config_get_dataset(&config);
if (!dataset) {
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
if (change_key(pamh, dataset, token->value) == -1) {
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
if (pw_clear(pamh) == -1) {
return (PAM_SERVICE_ERR);
}
} else {
zfs_key_config_free(&config);
}
return (PAM_SUCCESS);
}
PAM_EXTERN int
pam_sm_open_session(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
if (geteuid() != 0) {
pam_syslog(pamh, LOG_ERR,
"Cannot zfs_mount when not being root.");
return (PAM_SUCCESS);
}
zfs_key_config_t config;
zfs_key_config_load(pamh, &config, argc, argv);
if (config.uid < 1000) {
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}
int counter = zfs_key_config_modify_session_counter(pamh, &config, 1);
if (counter != 1) {
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}
const pw_password_t *token = pw_get(pamh);
if (token == NULL) {
zfs_key_config_free(&config);
return (PAM_SESSION_ERR);
}
if (pam_zfs_init(pamh) != 0) {
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
char *dataset = zfs_key_config_get_dataset(&config);
if (!dataset) {
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
if (decrypt_mount(pamh, dataset, token->value) == -1) {
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
if (pw_clear(pamh) == -1) {
return (PAM_SERVICE_ERR);
}
return (PAM_SUCCESS);
}
__attribute__((visibility("default")))
PAM_EXTERN int
pam_sm_close_session(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
if (geteuid() != 0) {
pam_syslog(pamh, LOG_ERR,
"Cannot zfs_mount when not being root.");
return (PAM_SUCCESS);
}
zfs_key_config_t config;
zfs_key_config_load(pamh, &config, argc, argv);
if (config.uid < 1000) {
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}
int counter = zfs_key_config_modify_session_counter(pamh, &config, -1);
if (counter != 0) {
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}
if (config.unmount_and_unload) {
if (pam_zfs_init(pamh) != 0) {
zfs_key_config_free(&config);
return (PAM_SERVICE_ERR);
}
char *dataset = zfs_key_config_get_dataset(&config);
if (!dataset) {
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SESSION_ERR);
}
if (unmount_unload(pamh, dataset) == -1) {
free(dataset);
pam_zfs_free();
zfs_key_config_free(&config);
return (PAM_SESSION_ERR);
}
free(dataset);
pam_zfs_free();
}
zfs_key_config_free(&config);
return (PAM_SUCCESS);
}