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systemd/src/nss-systemd/nss-systemd.c
Yu Watanabe 06202b9e65 nss: do not modify errno when NSS_STATUS_NOTFOUND or NSS_STATUS_SUCCESS 
This also adds PROTECT_ERRNO for all nss module functions.

C.f. glibc NSS documents https://www.gnu.org/software/libc/manual/html_node/NSS-Modules-Interface.html
and discussion in https://sourceware.org/bugzilla/show_bug.cgi?id=23410.

Fixes #9585.
2018-07-25 10:23:22 +02:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <nss.h>
#include <pthread.h>
#include "sd-bus.h"
#include "alloc-util.h"
#include "bus-common-errors.h"
#include "dirent-util.h"
#include "env-util.h"
#include "fd-util.h"
#include "fs-util.h"
#include "list.h"
#include "macro.h"
#include "nss-util.h"
#include "signal-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "user-util.h"
#include "util.h"
#define DYNAMIC_USER_GECOS "Dynamic User"
#define DYNAMIC_USER_PASSWD "*" /* locked */
#define DYNAMIC_USER_DIR "/"
#define DYNAMIC_USER_SHELL "/sbin/nologin"
static const struct passwd root_passwd = {
.pw_name = (char*) "root",
.pw_passwd = (char*) "x", /* see shadow file */
.pw_uid = 0,
.pw_gid = 0,
.pw_gecos = (char*) "Super User",
.pw_dir = (char*) "/root",
.pw_shell = (char*) "/bin/sh",
};
static const struct passwd nobody_passwd = {
.pw_name = (char*) NOBODY_USER_NAME,
.pw_passwd = (char*) "*", /* locked */
.pw_uid = UID_NOBODY,
.pw_gid = GID_NOBODY,
.pw_gecos = (char*) "User Nobody",
.pw_dir = (char*) "/",
.pw_shell = (char*) "/sbin/nologin",
};
static const struct group root_group = {
.gr_name = (char*) "root",
.gr_gid = 0,
.gr_passwd = (char*) "x", /* see shadow file */
.gr_mem = (char*[]) { NULL },
};
static const struct group nobody_group = {
.gr_name = (char*) NOBODY_GROUP_NAME,
.gr_gid = GID_NOBODY,
.gr_passwd = (char*) "*", /* locked */
.gr_mem = (char*[]) { NULL },
};
typedef struct UserEntry UserEntry;
typedef struct GetentData GetentData;
struct UserEntry {
uid_t id;
char *name;
GetentData *data;
LIST_FIELDS(UserEntry, entries);
};
struct GetentData {
/* As explained in NOTES section of getpwent_r(3) as 'getpwent_r() is not really
* reentrant since it shares the reading position in the stream with all other threads',
* we need to protect the data in UserEntry from multithreaded programs which may call
* setpwent(), getpwent_r(), or endpwent() simultaneously. So, each function locks the
* data by using the mutex below. */
pthread_mutex_t mutex;
UserEntry *position;
LIST_HEAD(UserEntry, entries);
};
static GetentData getpwent_data = { PTHREAD_MUTEX_INITIALIZER, NULL, NULL };
static GetentData getgrent_data = { PTHREAD_MUTEX_INITIALIZER, NULL, NULL };
NSS_GETPW_PROTOTYPES(systemd);
NSS_GETGR_PROTOTYPES(systemd);
enum nss_status _nss_systemd_endpwent(void) _public_;
enum nss_status _nss_systemd_setpwent(int stayopen) _public_;
enum nss_status _nss_systemd_getpwent_r(struct passwd *result, char *buffer, size_t buflen, int *errnop) _public_;
enum nss_status _nss_systemd_endgrent(void) _public_;
enum nss_status _nss_systemd_setgrent(int stayopen) _public_;
enum nss_status _nss_systemd_getgrent_r(struct group *result, char *buffer, size_t buflen, int *errnop) _public_;
static int direct_lookup_name(const char *name, uid_t *ret) {
_cleanup_free_ char *s = NULL;
const char *path;
int r;
assert(name);
/* Normally, we go via the bus to resolve names. That has the benefit that it is available from any mount
* namespace and subject to proper authentication. However, there's one problem: if our module is called from
* dbus-daemon itself we really can't use D-Bus to communicate. In this case, resort to a client-side hack,
* and look for the dynamic names directly. This is pretty ugly, but breaks the cyclic dependency. */
path = strjoina("/run/systemd/dynamic-uid/direct:", name);
r = readlink_malloc(path, &s);
if (r < 0)
return r;
return parse_uid(s, ret);
}
static int direct_lookup_uid(uid_t uid, char **ret) {
char path[STRLEN("/run/systemd/dynamic-uid/direct:") + DECIMAL_STR_MAX(uid_t) + 1], *s;
int r;
xsprintf(path, "/run/systemd/dynamic-uid/direct:" UID_FMT, uid);
r = readlink_malloc(path, &s);
if (r < 0)
return r;
if (!valid_user_group_name(s)) { /* extra safety check */
free(s);
return -EINVAL;
}
*ret = s;
return 0;
}
enum nss_status _nss_systemd_getpwnam_r(
const char *name,
struct passwd *pwd,
char *buffer, size_t buflen,
int *errnop) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
uint32_t translated;
size_t l;
int bypass, r;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert(name);
assert(pwd);
/* If the username is not valid, then we don't know it. Ideally libc would filter these for us anyway. We don't
* generate EINVAL here, because it isn't really out business to complain about invalid user names. */
if (!valid_user_group_name(name))
return NSS_STATUS_NOTFOUND;
/* Synthesize entries for the root and nobody users, in case they are missing in /etc/passwd */
if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) {
if (streq(name, root_passwd.pw_name)) {
*pwd = root_passwd;
return NSS_STATUS_SUCCESS;
}
if (synthesize_nobody() &&
streq(name, nobody_passwd.pw_name)) {
*pwd = nobody_passwd;
return NSS_STATUS_SUCCESS;
}
}
/* Make sure that we don't go in circles when allocating a dynamic UID by checking our own database */
if (getenv_bool_secure("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
return NSS_STATUS_NOTFOUND;
bypass = getenv_bool_secure("SYSTEMD_NSS_BYPASS_BUS");
if (bypass <= 0) {
r = sd_bus_open_system(&bus);
if (r < 0)
bypass = 1;
}
if (bypass > 0) {
r = direct_lookup_name(name, (uid_t*) &translated);
if (r == -ENOENT)
return NSS_STATUS_NOTFOUND;
if (r < 0)
goto fail;
} else {
r = sd_bus_call_method(bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"LookupDynamicUserByName",
&error,
&reply,
"s",
name);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
return NSS_STATUS_NOTFOUND;
goto fail;
}
r = sd_bus_message_read(reply, "u", &translated);
if (r < 0)
goto fail;
}
l = strlen(name);
if (buflen < l+1) {
*errnop = ERANGE;
return NSS_STATUS_TRYAGAIN;
}
memcpy(buffer, name, l+1);
pwd->pw_name = buffer;
pwd->pw_uid = (uid_t) translated;
pwd->pw_gid = (uid_t) translated;
pwd->pw_gecos = (char*) DYNAMIC_USER_GECOS;
pwd->pw_passwd = (char*) DYNAMIC_USER_PASSWD;
pwd->pw_dir = (char*) DYNAMIC_USER_DIR;
pwd->pw_shell = (char*) DYNAMIC_USER_SHELL;
return NSS_STATUS_SUCCESS;
fail:
*errnop = -r;
return NSS_STATUS_UNAVAIL;
}
enum nss_status _nss_systemd_getpwuid_r(
uid_t uid,
struct passwd *pwd,
char *buffer, size_t buflen,
int *errnop) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
_cleanup_free_ char *direct = NULL;
const char *translated;
size_t l;
int bypass, r;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
if (!uid_is_valid(uid))
return NSS_STATUS_NOTFOUND;
/* Synthesize data for the root user and for nobody in case they are missing from /etc/passwd */
if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) {
if (uid == root_passwd.pw_uid) {
*pwd = root_passwd;
return NSS_STATUS_SUCCESS;
}
if (synthesize_nobody() &&
uid == nobody_passwd.pw_uid) {
*pwd = nobody_passwd;
return NSS_STATUS_SUCCESS;
}
}
if (!uid_is_dynamic(uid))
return NSS_STATUS_NOTFOUND;
if (getenv_bool_secure("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
return NSS_STATUS_NOTFOUND;
bypass = getenv_bool_secure("SYSTEMD_NSS_BYPASS_BUS");
if (bypass <= 0) {
r = sd_bus_open_system(&bus);
if (r < 0)
bypass = 1;
}
if (bypass > 0) {
r = direct_lookup_uid(uid, &direct);
if (r == -ENOENT)
return NSS_STATUS_NOTFOUND;
if (r < 0)
goto fail;
translated = direct;
} else {
r = sd_bus_call_method(bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"LookupDynamicUserByUID",
&error,
&reply,
"u",
(uint32_t) uid);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
return NSS_STATUS_NOTFOUND;
goto fail;
}
r = sd_bus_message_read(reply, "s", &translated);
if (r < 0)
goto fail;
}
l = strlen(translated) + 1;
if (buflen < l) {
*errnop = ERANGE;
return NSS_STATUS_TRYAGAIN;
}
memcpy(buffer, translated, l);
pwd->pw_name = buffer;
pwd->pw_uid = uid;
pwd->pw_gid = uid;
pwd->pw_gecos = (char*) DYNAMIC_USER_GECOS;
pwd->pw_passwd = (char*) DYNAMIC_USER_PASSWD;
pwd->pw_dir = (char*) DYNAMIC_USER_DIR;
pwd->pw_shell = (char*) DYNAMIC_USER_SHELL;
return NSS_STATUS_SUCCESS;
fail:
*errnop = -r;
return NSS_STATUS_UNAVAIL;
}
#pragma GCC diagnostic ignored "-Wsizeof-pointer-memaccess"
enum nss_status _nss_systemd_getgrnam_r(
const char *name,
struct group *gr,
char *buffer, size_t buflen,
int *errnop) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
uint32_t translated;
size_t l;
int bypass, r;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert(name);
assert(gr);
if (!valid_user_group_name(name))
return NSS_STATUS_NOTFOUND;
/* Synthesize records for root and nobody, in case they are missing form /etc/group */
if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) {
if (streq(name, root_group.gr_name)) {
*gr = root_group;
return NSS_STATUS_SUCCESS;
}
if (synthesize_nobody() &&
streq(name, nobody_group.gr_name)) {
*gr = nobody_group;
return NSS_STATUS_SUCCESS;
}
}
if (getenv_bool_secure("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
return NSS_STATUS_NOTFOUND;
bypass = getenv_bool_secure("SYSTEMD_NSS_BYPASS_BUS");
if (bypass <= 0) {
r = sd_bus_open_system(&bus);
if (r < 0)
bypass = 1;
}
if (bypass > 0) {
r = direct_lookup_name(name, (uid_t*) &translated);
if (r == -ENOENT)
return NSS_STATUS_NOTFOUND;
if (r < 0)
goto fail;
} else {
r = sd_bus_call_method(bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"LookupDynamicUserByName",
&error,
&reply,
"s",
name);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
return NSS_STATUS_NOTFOUND;
goto fail;
}
r = sd_bus_message_read(reply, "u", &translated);
if (r < 0)
goto fail;
}
l = sizeof(char*) + strlen(name) + 1;
if (buflen < l) {
*errnop = ERANGE;
return NSS_STATUS_TRYAGAIN;
}
memzero(buffer, sizeof(char*));
strcpy(buffer + sizeof(char*), name);
gr->gr_name = buffer + sizeof(char*);
gr->gr_gid = (gid_t) translated;
gr->gr_passwd = (char*) DYNAMIC_USER_PASSWD;
gr->gr_mem = (char**) buffer;
return NSS_STATUS_SUCCESS;
fail:
*errnop = -r;
return NSS_STATUS_UNAVAIL;
}
enum nss_status _nss_systemd_getgrgid_r(
gid_t gid,
struct group *gr,
char *buffer, size_t buflen,
int *errnop) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
_cleanup_free_ char *direct = NULL;
const char *translated;
size_t l;
int bypass, r;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
if (!gid_is_valid(gid))
return NSS_STATUS_NOTFOUND;
/* Synthesize records for root and nobody, in case they are missing from /etc/group */
if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) {
if (gid == root_group.gr_gid) {
*gr = root_group;
return NSS_STATUS_SUCCESS;
}
if (synthesize_nobody() &&
gid == nobody_group.gr_gid) {
*gr = nobody_group;
return NSS_STATUS_SUCCESS;
}
}
if (!gid_is_dynamic(gid))
return NSS_STATUS_NOTFOUND;
if (getenv_bool_secure("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
return NSS_STATUS_NOTFOUND;
bypass = getenv_bool_secure("SYSTEMD_NSS_BYPASS_BUS");
if (bypass <= 0) {
r = sd_bus_open_system(&bus);
if (r < 0)
bypass = 1;
}
if (bypass > 0) {
r = direct_lookup_uid(gid, &direct);
if (r == -ENOENT)
return NSS_STATUS_NOTFOUND;
if (r < 0)
goto fail;
translated = direct;
} else {
r = sd_bus_call_method(bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"LookupDynamicUserByUID",
&error,
&reply,
"u",
(uint32_t) gid);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_DYNAMIC_USER))
return NSS_STATUS_NOTFOUND;
goto fail;
}
r = sd_bus_message_read(reply, "s", &translated);
if (r < 0)
goto fail;
}
l = sizeof(char*) + strlen(translated) + 1;
if (buflen < l) {
*errnop = ERANGE;
return NSS_STATUS_TRYAGAIN;
}
memzero(buffer, sizeof(char*));
strcpy(buffer + sizeof(char*), translated);
gr->gr_name = buffer + sizeof(char*);
gr->gr_gid = gid;
gr->gr_passwd = (char*) DYNAMIC_USER_PASSWD;
gr->gr_mem = (char**) buffer;
return NSS_STATUS_SUCCESS;
fail:
*errnop = -r;
return NSS_STATUS_UNAVAIL;
}
static void user_entry_free(UserEntry *p) {
if (!p)
return;
if (p->data)
LIST_REMOVE(entries, p->data->entries, p);
free(p->name);
free(p);
}
static int user_entry_add(GetentData *data, const char *name, uid_t id) {
UserEntry *p;
assert(data);
/* This happens when User= or Group= already exists statically. */
if (!uid_is_dynamic(id))
return -EINVAL;
p = new0(UserEntry, 1);
if (!p)
return -ENOMEM;
p->name = strdup(name);
if (!p->name) {
free(p);
return -ENOMEM;
}
p->id = id;
p->data = data;
LIST_PREPEND(entries, data->entries, p);
return 0;
}
static void systemd_endent(GetentData *data) {
UserEntry *p;
assert(data);
while ((p = data->entries))
user_entry_free(p);
data->position = NULL;
}
static enum nss_status nss_systemd_endent(GetentData *p) {
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert_se(pthread_mutex_lock(&p->mutex) == 0);
systemd_endent(p);
assert_se(pthread_mutex_unlock(&p->mutex) == 0);
return NSS_STATUS_SUCCESS;
}
enum nss_status _nss_systemd_endpwent(void) {
return nss_systemd_endent(&getpwent_data);
}
enum nss_status _nss_systemd_endgrent(void) {
return nss_systemd_endent(&getgrent_data);
}
static int direct_enumeration(GetentData *p) {
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
int r;
assert(p);
d = opendir("/run/systemd/dynamic-uid/");
if (!d)
return -errno;
FOREACH_DIRENT(de, d, return -errno) {
_cleanup_free_ char *name = NULL;
uid_t uid, verified;
if (!dirent_is_file(de))
continue;
r = parse_uid(de->d_name, &uid);
if (r < 0)
continue;
r = direct_lookup_uid(uid, &name);
if (r == -ENOMEM)
return r;
if (r < 0)
continue;
r = direct_lookup_name(name, &verified);
if (r < 0)
continue;
if (uid != verified)
continue;
r = user_entry_add(p, name, uid);
if (r == -ENOMEM)
return r;
if (r < 0)
continue;
}
return 0;
}
static enum nss_status systemd_setent(GetentData *p) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message* reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
const char *name;
uid_t id;
int bypass, r;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert(p);
assert_se(pthread_mutex_lock(&p->mutex) == 0);
systemd_endent(p);
if (getenv_bool_secure("SYSTEMD_NSS_DYNAMIC_BYPASS") > 0)
goto finish;
bypass = getenv_bool_secure("SYSTEMD_NSS_BYPASS_BUS");
if (bypass <= 0) {
r = sd_bus_open_system(&bus);
if (r < 0)
bypass = 1;
}
if (bypass > 0) {
r = direct_enumeration(p);
if (r < 0)
goto fail;
goto finish;
}
r = sd_bus_call_method(bus,
"org.freedesktop.systemd1",
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"GetDynamicUsers",
&error,
&reply,
NULL);
if (r < 0)
goto fail;
r = sd_bus_message_enter_container(reply, 'a', "(us)");
if (r < 0)
goto fail;
while ((r = sd_bus_message_read(reply, "(us)", &id, &name)) > 0) {
r = user_entry_add(p, name, id);
if (r == -ENOMEM)
goto fail;
if (r < 0)
continue;
}
if (r < 0)
goto fail;
r = sd_bus_message_exit_container(reply);
if (r < 0)
goto fail;
finish:
p->position = p->entries;
assert_se(pthread_mutex_unlock(&p->mutex) == 0);
return NSS_STATUS_SUCCESS;
fail:
systemd_endent(p);
assert_se(pthread_mutex_unlock(&p->mutex) == 0);
return NSS_STATUS_UNAVAIL;
}
enum nss_status _nss_systemd_setpwent(int stayopen) {
return systemd_setent(&getpwent_data);
}
enum nss_status _nss_systemd_setgrent(int stayopen) {
return systemd_setent(&getgrent_data);
}
enum nss_status _nss_systemd_getpwent_r(struct passwd *result, char *buffer, size_t buflen, int *errnop) {
enum nss_status ret;
UserEntry *p;
size_t len;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert(result);
assert(buffer);
assert(errnop);
assert_se(pthread_mutex_lock(&getpwent_data.mutex) == 0);
LIST_FOREACH(entries, p, getpwent_data.position) {
len = strlen(p->name) + 1;
if (buflen < len) {
*errnop = ERANGE;
ret = NSS_STATUS_TRYAGAIN;
goto finalize;
}
memcpy(buffer, p->name, len);
result->pw_name = buffer;
result->pw_uid = p->id;
result->pw_gid = p->id;
result->pw_gecos = (char*) DYNAMIC_USER_GECOS;
result->pw_passwd = (char*) DYNAMIC_USER_PASSWD;
result->pw_dir = (char*) DYNAMIC_USER_DIR;
result->pw_shell = (char*) DYNAMIC_USER_SHELL;
break;
}
if (!p) {
ret = NSS_STATUS_NOTFOUND;
goto finalize;
}
/* On success, step to the next entry. */
p = p->entries_next;
ret = NSS_STATUS_SUCCESS;
finalize:
/* Save position for the next call. */
getpwent_data.position = p;
assert_se(pthread_mutex_unlock(&getpwent_data.mutex) == 0);
return ret;
}
enum nss_status _nss_systemd_getgrent_r(struct group *result, char *buffer, size_t buflen, int *errnop) {
enum nss_status ret;
UserEntry *p;
size_t len;
PROTECT_ERRNO;
BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
assert(result);
assert(buffer);
assert(errnop);
assert_se(pthread_mutex_lock(&getgrent_data.mutex) == 0);
LIST_FOREACH(entries, p, getgrent_data.position) {
len = sizeof(char*) + strlen(p->name) + 1;
if (buflen < len) {
*errnop = ERANGE;
ret = NSS_STATUS_TRYAGAIN;
goto finalize;
}
memzero(buffer, sizeof(char*));
strcpy(buffer + sizeof(char*), p->name);
result->gr_name = buffer + sizeof(char*);
result->gr_gid = p->id;
result->gr_passwd = (char*) DYNAMIC_USER_PASSWD;
result->gr_mem = (char**) buffer;
break;
}
if (!p) {
ret = NSS_STATUS_NOTFOUND;
goto finalize;
}
/* On success, step to the next entry. */
p = p->entries_next;
ret = NSS_STATUS_SUCCESS;
finalize:
/* Save position for the next call. */
getgrent_data.position = p;
assert_se(pthread_mutex_unlock(&getgrent_data.mutex) == 0);
return ret;
}
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