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<chapter id="Security">

<title>Security guide</title>

<sect1>

<title>Overview</title>

<para>

</para>

<sect2>

<title>General Security Principles</title>

<para>The following principles are fundamental to using any application

securely.

<glosslist>

<glossentry>

<glossterm>Keep Software Up To Date</glossterm>

<glossdef>

<para>

One of the principles of good security practise is to keep all

software versions and patches up to date. Activate the VirtualBox

update notification to get notified when a new VirtualBox release

is available. When updating VirtualBox, do not forget to update

the Guest Additions. Keep the host operating system as well as the

guest operating system up to date.

</para>

</glossdef>

</glossentry>

<glossentry>

<glossterm>Restrict Network Access to Critical Services</glossterm>

<glossdef>

<para>

Use proper means, for instance a firewall, to protect your computer

and your guest(s) from accesses from the outside. Choosing the proper

networking mode for VMs helps to separate host networking from the

guest and vice versa.

</para>

</glossdef>

</glossentry>

<glossentry>

<glossterm>Follow the Principle of Least Privilege</glossterm>

<glossdef>

<para>

The principle of least privilege states that users should be given the

least amount of privilege necessary to perform their jobs. Always execute VirtualBox

as a regular user. We strongly discourage anyone from executing

VirtualBox with system privileges.

</para>

<para>

Choose restrictive permissions when creating configuration files,

for instance when creating /etc/default/virtualbox, see

<xref linkend="linux_install_opts"/>. Mode 0600 would be preferred.

</para>

</glossdef>

</glossentry>

<glossentry>

<glossterm>Monitor System Activity</glossterm>

<glossdef>

<para>

System security builds on three pillars: good security protocols, proper

system configuration and system monitoring. Auditing and reviewing audit

records address the third requirement. Each component within a system

has some degree of monitoring capability. Follow audit advice in this

document and regularly monitor audit records.

</para>

</glossdef>

</glossentry>

<glossentry>

<glossterm>Keep Up To Date on Latest Security Information</glossterm>

<glossdef>

<para>

Oracle continually improves its software and documentation. Check this

note note yearly for revisions.

</para>

</glossdef>

</glossentry>

</glosslist>

</para>

</sect2>

</sect1>

<sect1>

<title>Secure Installation and Configuration</title>

</sect1>

<sect2>

<title>Installation Overview</title>

<para>

The VirtualBox base package should be downloaded only from a trusted source,

for instance the official website

<ulink url="http://www.virtualbox.org">http://www.virtualbox.org</ulink>.

The integrity of the package should be verified with the provided SHA256

checksum which can be found on the official website.

</para>

<para>

General VirtualBox installation instructions for the supported hosts

can be found in <xref linkend="installation"/>.

</para>

<para>

On Windows hosts, the installer allows for disabling USB support, support

for bridged networking, support for host-only networking and the Python

language bindings, see <xref linkend="installation_windows"/>.

All these features are enabled by default but disabling some

of them could be appropriate if the corresponding functionality is not

required by any virtual machine. The Python language bindings are only

required if the VirtualBox API is to be used by external Python

applications. In particular USB support and support

for the two networking modes require the installation of Windows kernel

drivers on the host. Therefore disabling those selected features can

not only be used to restrict the user to certain functionality but

also to minimize the surface provided to a potential attacker. </para>

<para>

The general case is to install the complete VirtualBox package. The

installation must be done with system privileges. All VirtualBox binaries

should be executed as a regular user and never as a privileged user.

</para>

<para>

The Oracle VM VirtualBox extension pack provides additional features

and must be downloaded and installed separately, see

<xref linkend="intro-installing"/>. As for the base package, the SHA256

checksum of the extension pack should be verified. As the installation

requires system privileges, VirtualBox will ask for the system

password during the installation of the extension pack.

</para>

</sect2>

<sect2>

<title>Post Installation Configuration</title>

<para>

Normally there is no post installation configuration of VirtualBox components

required. However, on Solaris and Linux hosts it is necessary to configure

the proper permissions for users executing VMs and who should be able to

access certain host resources. For instance, Linux users must be member of

the <emphasis>vboxusers</emphasis> group to be able to pass USB devices to a

guest. If a serial host interface should be accessed from a VM, the proper

permissions must be granted to the user to be able to access that device.

The same applies to other resources like raw partitions, DVD/CD drives

and sound devices.

</para>

</sect2>

<sect1>

<title>Security Features</title>

<para>This section outlines the specific security mechanisms offered

by VirtualBox.</para>

<sect2>

<title>The Security Model</title>

<para>

One property of virtual machine monitors (VMMs) like VirtualBox is to encapsulate

a guest by executing it in a protected environment, a virtual machine,

running as a user process on the host operating system. The guest cannot

communicate directly with the hardware or other computers but only through

the VMM. The VMM provides emulated physical resources and devices to the

guest which are accessed by the guest operating system to perform the required

tasks. The VM settings control the resources provided to the guest, for example

the amount of guest memory or the number of guest processors, (see

<xref linkend="generalsettings"/>) and the enabled features for that guest

(for example remote control, certain screen settings and others).

</para>

</sect2>

<sect2>

<title>Secure Configuration of Virtual Machines</title>

<para>

Several aspects of a virtual machine configuration are subject to security

considerations.</para>

<sect3>

<title>Networking</title>

<para>

The default networking mode for VMs is NAT which means that

the VM acts like a computer behind a router, see

<xref linkend="network_nat"/>. The guest is part of a private

subnet belonging to this VM and the guest IP is not visible

from the outside. This networking mode works without

any additional setup and is sufficient for many purposes.

</para>

<para>

If bridged networking is used, the VM acts like a computer inside

the same network as the host, see <xref linkend="network_bridged"/>.

In this case, the guest has the same network access as the host and

a firewall might be necessary to protect other computers on the

subnet from a potential malicious guest as well as to protect the

guest from a direct access from other computers. In some cases it is

worth considering using a forwarding rule for a specific port in NAT

mode instead of using bridged networking.

</para>

<para>

Some setups do not require a VM to be connected to the public network

at all. Internal networking (see <xref linkend="network_internal"/>)

or host-only networking (see <xref linkend="network_hostonly"/>)

are often sufficient to connect VMs among each other or to connect

VMs only with the host but not with the public network.

</para>

</sect3>

<sect3>

<title>VRDP remote desktop authentication</title>

<para>When using the VirtualBox extension pack provided by Oracle

for VRDP remote desktop support, you can optionally use various

methods to configure RDP authentication. The "null" method is

very insecure and should be avoided in a public network.

See <xref linkend="vbox-auth" /> for details.</para>

</sect3>

<sect3>

<title>Clipboard</title>

<para>

The shared clipboard allows users to share data between the host and

the guest. Enabling the clipboard in "Bidirectional" mode allows

the guest to read and write the host clipboard. The "Host to guest"

mode and the "Guest to host" mode limit the access to one

direction. If the guest is able to access the host clipboard it

could also access sensitive data from the host which is shared over

the clipboard.

</para>

</sect3>

<sect3>

<title>3D graphics acceleration</title>

<para>Enabling 3D graphics via the Guest Additions exposes the host

to additional security risks; see <xref

linkend="guestadd-3d" />.</para>

</sect3>

<sect3>

<title>CD/DVD passthrough</title>

<para>Enabling CD/DVD passthrough allows the guest to perform advanced

operations on the CD/DVD drive, see <xref linkend="storage-cds"/>.

This could induce a security risk as a guest could overwrite data

on a CD/DVD medium.

</para>

</sect3>

<sect3>

<title>USB passthrough</title>

<para>

Passing USB devices to the guest provides the guest full access

to these devices, see <xref linkend="settings-usb"/>. For instance,

in addition to reading and writing the content of the partitions

of an external USB disk the guest will be also able to read and

write the partition table and hardware data of that disk.

</para>

</sect3>

</sect2>

<sect2>

<title>Configuring and Using Authentication</title>

<para>The following components of VirtualBox can use passwords for

authentication:<itemizedlist>

<listitem>

<para>When using teleporting, passwords can optionally be used to

protect a machine waiting to be teleported from unauthorized access.

Note however that these passwords are stored <emphasis

role="bold">unencrypted</emphasis> in the machine configuration XML

and therefore potentially readable on the host. See <xref

linkend="teleporting" /> and <xref

linkend="vboxmanage-modifyvm-teleport" />.</para>

</listitem>

<listitem>

<para>When using remote iSCSI storage and the storage server

requires authentication, a password can optionally be supplied with

the <computeroutput>VBoxManage storageattach</computeroutput>

command. Note however that this is stored <emphasis

role="bold">unencrypted</emphasis> in the machine configuration and

is therefore potentially readable on the host. See <xref

linkend="storage-iscsi" /> and <xref

linkend="vboxmanage-storageattach" />.</para>

</listitem>

<listitem>

<para>When using the VirtualBox web service to control a VirtualBox

host remotely, connections to the web service are authenticated in

various ways. This is described in detail in the VirtualBox Software

Development Kit (SDK) reference; please see <xref

linkend="VirtualBoxAPI" />.</para>

</listitem>

</itemizedlist></para>

</sect2>

<!--

<sect2>

<title>Potentially insecure operations</title>

<para>The following features of VirtualBox can present security

problems:<itemizedlist>

<listitem>

<para>Enabling 3D graphics via the Guest Additions exposes the host

to additional security risks; see <xref

linkend="guestadd-3d" />.</para>

</listitem>

<listitem>

<para>When teleporting a machine, the data stream through which the

machine's memory contents are transferred from one host to another

is not encrypted. A third party with access to the network through

which the data is transferred could therefore intercept that

data. An SSH tunnel could be used to secure the connection between

the two hosts. But when considering teleporting a VM over an untrusted

network the first question to answer is how both VMs can securely

access the same virtual disk image(s) with a reasonable performance. </para>

</listitem>

<listitem>

<para>When using the VirtualBox web service to control a VirtualBox

host remotely, connections to the web service (through which the API

calls are transferred via SOAP XML) are not encrypted, but use plain

HTTP. This is a potential security risk! For details about the web

service, please see <xref linkend="VirtualBoxAPI" />.</para>

<para>The web services are not started by default. Please refer to

<xref linkend="vboxwebsrv-daemon"/> to find out how to start this

service. It has to be started as a regular user and only the VMs

of that user can be controled. By default, the service binds to

localhost preventing any remote connection.</para>

</listitem>

<listitem>

<para>Traffic sent over a UDP Tunnel network attachment is not

encrypted. You can either encrypt it on the host network level (with

IPsec), or use encrypted protocols in the guest network (such as

SSH). The security properties are similar to bridged Ethernet.</para>

</listitem>

</itemizedlist></para>

</sect2>

<sect2>

<title>Encryption</title>

<para>The following components of VirtualBox use encryption to protect

sensitive data:<itemizedlist>

<listitem>

<para>When using the VirtualBox extension pack provided by Oracle

for VRDP remote desktop support, RDP data can optionally be

encrypted. See <xref linkend="vrde-crypt" /> for details. Only

the Enhanced RDP Security method (RDP5.2) with TLS protocol

provides a secure connection. Standard RDP Security (RDP4 and

RDP5.1) is vulnerable to a man-in-the-middle attack.</para>

</listitem>

</itemizedlist></para>

</sect2>

</sect1>

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</chapter>