Tag: security

Linux memory analysis with Lime and Volatility

Lime is a Loadable Kernel Module (LKM) which allows for volatile memory acquisition from Linux and Linux-based devices, such as Android. This makes LiME unique as it is the first tool that allows for full memory captures on Android devices. It also minimises its interaction between user and kernel space processes during acquisition, which allows it to produce memory captures that are more forensically sound than those of other tools designed for Linux memory acquisition. – Lime. Volatility framework was released at Black Hat DC for analysis of memory during forensic investigations.

Analysing memory in Linux can be carried out using Lime which is a forensic tool to dump the memory. I am actually using CentOS 6 distribution installed on a Virtual Box to acquire memory. Normally before capturing the memory, the suspicious system’s architecture should be well known. May be you would need to compile Lime on the the suspicious machine itself if you do not know the architecture. Once you compile Lime, you would have a kernel loadable object which can be injected in the Linux Kernel itself.

Linux memory dump with Lime

1. You will first need to download Lime on the suspicious machine.

git clone https://github.com/504ensicsLabs/LiME

2. Do the compilation of Lime. Once it has been compiled, you will noticed the creation of the Lime loadable kernel object.

make

3. Now the kernel object have to be loaded into the kernel. Insert the kernel module. Then, define the location and format to save the memory image.

insmod lime-2.6.32-696.23.1.el6.x86_64.ko "path=/Linux64.mem format=lime"

4. You can view if the module have been successfully loaded.

lsmod | grep -i lime

Analysis with Volatility

5. We will now analyze the memory dump using Volatility. Download it from Github.

git clone https://github.com/volatilityfoundation/volatility

6.  Now, we will create a Linux profile. We will also need to download the DwarfDump package. Once it is downloaded go to Tools -> Linux directory, then create the module.dwarf file.

yum install epel-release libdwarf-tools -y && make

7. To proceed further, the System.map file is important to build the profile. The System.map file contains the locations of all the functions active in the compiled kernel. You will notice it inside the /boot directory. It is also important to corroborate the version appended with the System.map file together the version and architecture of the kernel. In the example below, the version is 2.6.32-696.23.1.el6.x86_64.

8. Now, go to the root of the Volatility directory using cd ../../ since I assumed that you are in the linux directory. Then, create a zip file as follows:

zip volatility/plugins/overlays/linux/Centos6-2632.zip tools/linux/module.dwarf /boot/System.map-2.6.32-696.23.1.el6.x86_64

9. The volatility module has now been successfully created as indicated in part 8 for the particular version of the Linux and kernel version. Time to have fun with some Python script. You can view the profile created with the following command:

python vol.py --info | grep Linux

As you can see the profile LinuxCentos6-2632 profile has been created.

10. Volatile contains plugins to view details about the memory dump performed. To view the plugins or parsers, use the following command:

python vol.py --info | grep -i linux_

11. Now imagine that you want to see the processes running at the time of the memory dump. You will have to execute the vol.py script, specify the location of the memory dump, define the profile created and call the parser concerned.

python vol.py --file=/Linux64.mem --profile=LinuxCentos6-2632x64 linux_psscan

12. Another example to recover the routing cache memory:

python vol.py --file=/Linux64.mem --profile=LinuxCentos6-2632x64 linux_route_cache

Automating Lime using LiMEaid

I find the LiMEaid tools really interesting to remote executing of Lime. “LiMEaide is a python application designed to remotely dump RAM of a Linux client and create a volatility profile for later analysis on your local host. I hope that this will simplify Linux digital forensics in a remote environment. In order to use LiMEaide all you need to do is feed a remote Linux client IP address, sit back, and consume your favorite caffeinated beverage.” – LiMEaid

Tips:

  • Linux architecture is very important when dealing with Lime. This is probably the first question that one would ask.
  • The kernel-headers package is a must to create the kernel loadable object.
  • Once a memory dump have been created, its important to take a hash value. It can be done using the command md5sum Linux64.mem
  • I would also consider to download the devel tools using yum groupinstall “Development Tools” -y
  • As good practice as indicated in part 8 when creating the zip file, use the proper convention when naming the file. In my case I used the OS version and the kernel version for future references.
  • Not all Parsers/Plugins will work with Volatile as same might not be compatible with the Linux system.
  • You can check out the Volatile wiki for more info about the Parsers.

 

Auditing Linux Operating System with Lynis

Auditing a Linux System is one of the most important aspect when it comes to security. After deploying a simple Centos 7 Linux machine on virtual box, I made an audit using Lynis. It is amazing how many tiny flaws can be seen right from the beginning of a fresh installation. Lynis Enterprise performs security scanning for Linux, macOS, and Unix systems. It helps you discover and solve issues quickly, so you can focus on your business and projects again.Cisofy.

Credits: cisofy.com
Credits: cisofy.com

Introduction

The Lynis tool performs both security and compliance auditing. It has a free and paid version which comes very handy especially if you are on a business environment. The installation of the Lynis tool is pretty simple. You can install it through the Linux repository itself, download the tar file or clone it directly from Github.

 

Scanning Performed by Lynis

1. I downloaded the tar file with the following command:

wget https://cisofy.com/files/lynis-2.6.0.tar.gz

2. Then, just untar the file and get into it

tar -xzf lynis-2.6.0.tar.gz && cd lynis

3. Once into the untar directory, launch the following command:

./lynis audit system --quick

 
As you can see from the output above, there are several suggestions at the end of the scan. In case the paid version of the application was used, more information and commands as how to remediate the situation would be given including support from Lynis. As regards to the free version, you can also debug by yourself several security aspects from the suggestions.
 
Suggestions, Compliance and Improvement.

 
1.The first two suggestions were about minimum and maximum password age.

Configure minimum password age in /etc/login.defs [AUTH-9286]

Configure maximum password age in /etc/login.defs [AUTH-9286]

To check the minimum and maximum password age, use the chage command :
chage -l
 

2. Use chage -m root to set the minimum password age and chage -M root to set maximum password age:

Also, you will have to set the parameter in the /etc/login.defs file

3. Delete accounts which are no longer used [AUTH-9288]

It is also suggested to delete accounts which are no longer in use. This suggestion was prompted as I created a user  “nitin” account during installation and did not use it yet. For the purpose of this blog, I deleted it using userdel -r nitin

4. Default umask in /etc/profile or /etc/profile.d/custom.sh could be more strict (e.g. 027) [AUTH-9328]

Default umask values are taken from the information provided in the /etc/login.defs file for RHEL (Red Hat) based distros. Debian and Ubuntu Linux based system use /etc/deluser.conf. To change default umask value to 027 which is actually 022 by default, you will need to modify the /etc/profile script as follows:

5. To decrease the impact of a full /home file system, place /home on a separated partition [FILE-6310]

  To decrease the impact of a full /tmp file system, place /tmp on a separated partition [FILE-6310]

  To decrease the impact of a full /var file system, place /var on a separated partition [FILE-6310]

In the article Move your /home to another partition, you will have detailed explanations to sort out this issue.

6. Disable drivers like USB storage when not used, to prevent unauthorized storage or data theft [STRG-1840]

   Disable drivers like firewire storage when not used, to prevent unauthorized storage or data theft [STRG-1846]

To disable USB and firewire storage drivers, add the following lines in /etc/modprobe.d/blacklist.conf then do a modprobe usb-storage && modprobe firewire-core

blacklist firewire-core
blacklist usb-storage

7. Split resolving between localhost and the hostname of the system [NAME-4406]

This issue is only about hostname and localhost in /etc/hosts which could confuse some applications installed on the machine. According to cisofy, for proper resolving, the entries of localhost and the local defined hostname, could be split. Using some middleware and some applications, resolving of the hostname to localhost, might confuse the software.

8. Install package ‘yum-utils’ for better consistency checking of the package database [PKGS-7384]

      Consider running ARP monitoring software (arpwatch,arpon) [NETW-3032]

The yum-utils and arpwatch are nice tools to perform more debugging and verification. Install it using the following commands:

yum install yum-utils arpwatch -y

9. You are advised to hide the mail_name (option: smtpd_banner) from your postfix configuration. Use postconf -e or change your main.cf file (/etc/postfix/main.cf) [MAIL-8818]

You just have to uncomment the following line and lauch a postconf -e. However, since this is a fresh install, and I’m not using postfix, it is better to stop the service.

 10.  Check iptables rules to see which rules are currently not used [FIRE-4513]

Since, I’m not on a production environment, it is very difficult to identify unused iptables rules right now. Once on the production environment, this situation is different. According to Cisofy, the best way is to “use iptables –list –numeric –verbose to display all rules. Check for rules which didn’t get a hit and repeat this process several times (e.g. in a few weeks). Finally remove any unneeded rules.”

 11. Consider hardening SSH configuration [SSH-7408]

  •     – Details  : AllowTcpForwarding (YES –> NO)
  •     – Details  : ClientAliveCountMax (3 –> 2)
  •     – Details  : Compression (YES –> (DELAYED|NO))
  •     – Details  : LogLevel (INFO –> VERBOSE)
  •     – Details  : MaxAuthTries (6 –> 2)
  •     – Details  : MaxSessions (10 –> 2)
  •     – Details  : PermitRootLogin (YES –> NO)
  •     – Details  : Port (22 –> )
  •     – Details  : TCPKeepAlive (YES –> NO)
  •     – Details  : UseDNS (YES –> NO)
  •     – Details  : X11Forwarding (YES –> NO)
  •     – Details  : AllowAgentForwarding (YES –> NO)

Again, hardening SSH is one of the most important to evade attacks especially from SSH bots. It all depends how your network infrastructure is configured and whether it is accessible from the internet or not. However, these details viewed are very informative.

12. Periodic system scan, malware and ransomware scanners are now a must. According to statistics, servers are being hacked constantly. Pervasive Monitoring is becoming a heavy cash deal for malicious softwares. 

The Lynis Command

Lynis documentation is pretty straight forward with a cheat sheet. The arguments are self explicit. Here are some hints.

1.Performs a system audit which is the most common audit.

lynis audit system

2. Provides command to do a remote scan.

lynis audit system remote <host>

3. Views the settings of default profile.

lynis show settings

4. Checks if you are using most recent version of Lynis

lynis update info

5. More information about a specific test-id

lynis show details <test-id>

6. To scan whole system

lynix --check-all Q

7. To see all available parameters of Lynis

lynis show options

At the end of any Lynis command, it will also prompt you where the logs have been stored for your future references. It is usually in /var/log/lynis.log. The systutorial on lynis is also a good start to grasp the command. All common systems based on Unix/Linux are supported. Examples include Linux, AIX, *BSD, HP-UX, macOS and Solaris. For package management, the following tools are supported:- dpkg/apt, pacman, pkg_info, RPM, YUM, zypper.

Securing MySQL traffic with Stunnel in a jail environment on CentOS

Stunnel is a program by Michal Trojnara that allows you to encrypt arbitrary TCP connections inside SSL. Stunnel can also allow you to secure non-SSL aware daemons and protocols (like POP, IMAP, LDAP, etc) by having Stunnel provide the encryption, requiring no changes to the daemon’s code. It is a proxy designed to add TLS encryption functionality to existing clients and servers without any changes in the programs’ code. Its architecture is optimized for security, portability, and scalability (including load-balancing), making it suitable for large deployments. – Stunnel.org

The concept that lies behind Stunnel is about the encryption methodology that is used when the client is sending a message to a server using a secure tunnel. In this article, we will focus on using MySQL alongside Stunnel. MariaDB Client will access the MariaDB server database using the Stunnel for more security and robustness.



Photo Credits: danscourses.com
Photo Credits: danscourses.com

I will demonstrate the installation and configuration using the CentOS distribution which is on my Virtual Box lab environment. I created two CentOS 7 virtual machines with hostname as stunnelserver and stunnelclient. We will tunnel the MySQL traffic via Stunnel. You can apply the same concept for SSH, Telnet, POP, IMAP or any TCP connection.

The two machines created are as follows:

  1. stunnelserver : 192.168.100.17 – Used as the Server
  2. stunnelclient : 192.168.100.18 – Used as the Client

Basic package installation and configuration on both servers

1. Install the Stunnel and OpenSSL package on both the client and the server.

yum install stunnel openssl -y

2. As we will be using Stunnel over MariaDB, you can use the MariaDB repository tools to get the links to download the repository. Make sure you have the MariaDB-client package installed on the stunnelclient which will be used as client to connect to the server. Also, install both packages on the stunnelserver. The commands to install the MariaDB packages are as follows:

sudo yum install MariaDB-server MariaDB-client

3. For more information about installations of MariaDB, Galera etc, refer to these links:

MariaDB Galera Clustering

MariaDB Master/Master installation

MariaDB Master/Slave installation

Configuration to be carried out on the stunnelserver (192.168.100.17)

 

 

4. Once you have all the packages installed, it’s time to create your privatekey.pem. Then, use the private key to create the certificate.pem. Whilst creating the certificate.pem, it will prompt you to enter some details. Feel free to fill it.

openssl genrsa -out privatekey.pem 2048

openssl req -new -x509 -days 365 -key privatekey.pem -out certificate.pem

5. Now comes the most interesting part to configure the stunnel.conf file by tunnelling it to the MySQL port on the stunnelserver. I observed that the package by default does not come with a stunnel.conf or even a Init script after installing it from the repository. So, you can create your own Init script. Here is my /etc/stunnel/stunnel.conf on the server:

chroot = /var/run/stunnel
setuid = stunnel
setgid = stunnel
pid = /stunnel.pid
debug = 7
output = /stunnel.log
sslVersion = TLSv1
[mysql]
key = /etc/stunnel/privatekey.pem
cert = /etc/stunnel/certificate.pem
accept = 44323
connect = 127.0.0.1:3306

6. Position your privatekey.pem and certificate.pem at /etc/stunnel directory. Make sure you have the right permission (400) on the privatekey.pem.

 

7. Based upon the configuration in part 5, we will now create the /var/run/stunnel directory and assign it with user and group of stunnel:

useradd -G stunnel stunnel && mkdir /var/run/stunnel && chown stunnel:stunnel /var/run/stunnel

8.  The port 44323 is a non reserved port which I chose to tunnel the traffic from the client.

9. As we do not have the Init script by default in the package, start the service as follows:

stunnel /etc/stunnel/stunnel.conf

10. A netstat or ss command on the server will show the Stunnel listening on port 44323.

Configuration to be carried out on the stunnelclient (192.168.100.18)

11. Here is the stunnel.conf file on the stunnel client :

verify = 2
chroot = /var/run/stunnel
setuid = stunnel
setgid = stunnel
pid = /stunnel.pid
CAfile = /etc/stunnel/certificate.pem
client = yes
sslVersion = TLSv1
renegotiation = no
[mysql]
accept = 24
connect = 192.168.100.17:44323

12. Import the certificate.pem in the /etc/stunnel/ directory.

scp <user>@<ipofstunnelserver>:/etc/stunnel/certificate.pem

13. Based upon the configuration in part 11, we will now create the /var/run/stunnel directory and assign it with user and group of stunnel:

useradd -G stunnel stunnel && mkdir /var/run/stunnel && chown stunnel:stunnel /var/run/stunnel

14. You can now start the service on the client as follows:

stunnel /etc/stunnel/stunnel.conf

15. A netstat on the client will show the Stunnel listening on port 24.

16. You can now connect on the MySQL database from your client to your server through the tunnel. Example:

mysql -h 127.0.0.1 -u <Name of Database> -p -P 24



Tips:

  • When starting Stunnel, the log and the pid file will be created automatically inside the jail environment that is /var/run/stunnel.
  • You can also change the debug log level. Level is a one of the syslog level names or numbers emerged (0), alert (1), crit (2), err (3), warning (4), notice (5), info (6), or debug (7). All logs for the specified level and all levels numerically less than it will be shown. Use debug = debug or debug = 7 for greatest debugging output. The default is notice (5).
  • If you compile from source, you will have a free log rotate and Init scripts. Probably on CentOS, it’s not packaged with the script!
  • You can also verify if SSLv2 and SSLv3 have been disabled using openssl s_client -connect 127.0.0.1:44323 -ssl3 and try with -tls1 to compare.
  • For the purpose of testing, you might need to check your firewall rules and SELINUX parameters.
  • You don’t need MariaDB-Server package on the client.
  • Stunnel is running on a Jail environment. The logs and the PID described in part 5 and 11 will be found in /var/run/stunnel.
  • You can invoke stunnel from inetd. Inetd is the Unix ‘super server’ that allows you to launch a program (for example the telnet daemon) whenever a connection is established to a specified port. See the “Stunnel how’s to” for more information. The Stunnel manual can also be viewed here.

 

Hackers.mu VideoStream #2 : Modem Insecurity in Mauritius

Some days back, the hackers.mu team made our first video stream on Youtube about Modem Insecurity in Mauritius. We received several feedbacks from the public, friends and local medias about the issue raised. Upon further research I noticed that there are several countries including Vietnam, China amongst others are in the same problematic situation as they are using the same Huawei modem. More and more vulnerabilities are now being faced by the end users. Users aware of the issue can mitigate it from their side whilst others are still in the dark.

On Friday, the 20th of October 2017, another video stream was carried out by the hackers.mu team alongside other friends and professionals. We started with a short introduction from everybody in the videostream.

We had Billal, Codarren, Edriss, Irshaad, Logan, Kifah, Selven, Rahul, Yash and myself (Nitin) participating in the video stream. You can view the VideoStream here:

Our agenda was as follows:

  • An introduction from participants
  • Huawei’s acceptance of upgrading Dnsmasq
  • Other discoveries in the Huawei modem
  • Implication of Krack attack
  • Understanding of the mitigation techniques on Krack attack
  • Everyone’s perspective about the vulnerabilities on the Huawei modem

Other sources talking about hackers.mu‘s insecurity detection on the Huawei modem

Hackers.mu VideoStream #1 : Modem Insecurity in Mauritius

On Tuesday the 17th of October 2017, the hackers.mu team had a public podcast on Modem Insecurity in Mauritius. Fifteen minutes after the start of the broadcast, there were already about 30 views from the public. We had over Keshav Purdassea, a student in cybersecurity as guest to ask questions. We also had people asking questions on the Facebook hackers.mu public group.

Logan from hackers.mu made a smart introduction during the podcast about its goal which is informing the public about the vulnerabilities found in Huawei Modem. You can view the video which has been uploaded on youtube here :

Codarren from hackers.mu laid emphasis on several interesting points such as the state of Dnsmasq. He also gave some interesting hints to launch commands on the router which is not similar like a usual Linux Box. He explained how all processes are running as root including Dnsmasq. Codarren recently had a conversation with engineers from Huawei and it’s quite obvious that Dnsmasq is also doing DNS. It was recommended to run Dnsmasq as a non-root user which is one of the best practice in any Linux Box. Someone can craft a DNS packet and run this on the modem with the intention to control it remotely. This security risk needs to be reviewed again.

 

In addition, I made a brief introduction on the preliminary precaution that can be taken to minimise impact such as deactivating Telnet or even SSH on the router. We also noticed how it’s possible to download the configuration file and decrypt it. All passwords can be seen clearly on the configuration files. The binary aescrypt2_huawei can be downloaded from the hackers.mu Facebook group. Here are the steps to be followed to decrypt it :

1.Use the following command to decrypt it :

[[email protected] ~]# ./aescrypt2_huawei 1 hw_ctree.xml decode.xml

2. To re-encode use the following command:

[[email protected] ~]# ./aescrypt2_huawei 0 decode.xml hw_ctree.xml

3. At line 1022, You can find the web interface password

1022 <X_HW_WebUserInfoInstance InstanceID="2" UserName="telecomadmin" Password="402931e04c03e24d360477a9f90b9eb15777e154360f06228be15c37679016ef" UserLevel="0" Enable="1" ModifyPass wordFlag="0" PassMode="2"/>

We also had Yash Paupiah, President of the UOM Computer Club who made a sensitive point regarding as to whether the patch was supposed to come from Mauritius Telecom or Huawei. After some research, we noticed that there was no patch from Huawei itself.

The whole team of hackers.mu and myself invite you to join our Facebook group and Twitter to keep in touch for our oncoming Live podcasts, Hackathons, Public events etc..

Other bloggers on the Podcast: