VMware ® Virtual
Infrastructure3
Security Risk Assessment
This template is designed to describe to an IT Security Team what
VMware Virtual Infrastructure3 is and how implementation of an
infrastructure that meets or exceeds the corporate security policies will
be achieved
BY GAVIN JOLLIFFE
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Table of Contents
Table of Contents............................................................................................................................................. 2
1
Document Control .................................................................................................................................. 3
1.1
Authorisation ............................................................................................................................................ 3
1.2
Document Control/Change History .......................................................................................................... 3
1.3
Document References .............................................................................................................................. 3
1.4
Distribution List ........................................................................................................................................ 3
1.5
Terms and Abbreviations ......................................................................................................................... 3
2
Introduction ........................................................................................................................................... 5
2.1
Purpose of document ............................................................................................................................... 5
2.2
Background............................................................................................................................................... 5
2.3
Assumptions / Exclusions ......................................................................................................................... 5
2.4
Issues & unknowns ................................................................................................................................... 5
2.5
Constraints (Standards, Policies, Guidelines) ........................................................................................... 5
3
Virtual Infrastructure Risk Assessment Overview ................................................................................... 6
3.1
Introduction.............................................................................................................................................. 6
3.2
General Security Features ........................................................................................................................ 7
4
ESX Server Service Console ................................................................................................................... 10
4.1
Overview ................................................................................................................................................ 10
4.2
Risk Assessment ..................................................................................................................................... 10
4.3
Additional Best Practice Configuration .................................................................................................. 13
5
ESX Server Kernel (Virtualisation layer) ................................................................................................ 16
5.1
Overview ................................................................................................................................................ 16
5.2
Risk Assessment ..................................................................................................................................... 16
6
ESX Server Virtual Networking Layer .................................................................................................... 18
6.1
Overview ................................................................................................................................................ 18
6.2
Risk Assessment ..................................................................................................................................... 19
6.3
Additional Best Practice configuration ................................................................................................... 21
7
Virtual Machines .................................................................................................................................. 23
7.1
Overview ................................................................................................................................................ 23
7.2
Risk Assessment ..................................................................................................................................... 23
7.3
Additional Best Practice configuration ................................................................................................... 25
8
Virtual Storage ...................................................................................................................................... 26
8.1
Overview ................................................................................................................................................ 26
8.2
Risk Assessment ..................................................................................................................................... 26
9
VirtualCenter ........................................................................................................................................ 28
9.1
Overview ................................................................................................................................................ 28
9.2
Risk Assessment ..................................................................................................................................... 28
9.3
Additional Best Practice Configuration .................................................................................................. 29
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1
Document Control
Copyright in this document remains vested in <COMPANY NAME> and no copies may be made of it or any part
of it except for the purpose of evaluation in confidence.
The information contained in this document is confidential and is submitted on the understanding that it will
be used only by the staff or consultants of <COMPANY NAME> and that, where external consultants are
employed, the use of this information is restricted to use in relation to the business of the project.
In particular, the contents of this document may not be disclosed in whole or in part to any other party
without the prior written consent of <COMPANY NAME>.
1.1
Authorisation
Authorised by : <AUTHORISOR NAME>
Date : <DATE>
1.2
Document Control/Change History
Version
Draft
1.3
Date
Comment
Editor
In Progress
Document References
Title
Author
Date
Version
Security Design of the VMware Infrastructure 3 Architecture
VMware
22/02/07
Not Specified
VMware Infrastructure 3 Security Hardening
VMware
21/02/07
Not Specified
Server Configuration Guide
VMware
25/09/06
20060925
Providing LUN Security
VMware
10/03/06
Not Specified
Note: Content from referenced documents has been quoted or paraphrased throughout this document.
1.4
Distribution List
Title
<NAME / POSITION>
1.5
Date
<DATE>
Version
<VERSION NO.>
Terms and Abbreviations
Term/Abbreviation
DoS
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Definition
Denial of Service attack
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MAC
Media Access Control
SSH
Secure Shell
VC
VMware VirtualCenter
VI
VMware Virtual Infrastructure
VMM
Virtual Machine Monitor
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2
Introduction
2.1
Purpose of document
This document provides an evaluation of the possible risks and proposed countermeasures with
implementation of the project using VMware Virtual Infrastructure virtualisation based software. The
document is virtualisation focussed and is intended to provide security personnel with enough detail to ensure
that current security standards are met or exceeded and allow the design of this project to proceed in an
assured manner.
2.2
Background
<CLIENT AND/OR PROJECT BACKGROUND>
2.3
Assumptions / Exclusions
This assessment excludes security risks present with a physical site attack.
2.4
Issues & unknowns
<COMPLETE AS APPLICABLE>
2.5
Constraints (Standards, Policies, Guidelines)
<COMPLETE AS APPLICABLE>
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3
Virtual Infrastructure Risk Assessment Overview
3.1
Introduction
VMware® ESX Server installs directly on server hardware, or “bare metal”, and inserts a virtualisation layer
between the hardware and the operating system. ESX Server partitions a physical server into multiple secure
and portable virtual machines that can run side by side on the same physical server. Each virtual machine
represents a complete system—with processors, memory, networking, storage and BIOS—so that Windows,
Linux, Solaris and NetWare operating systems and software applications run in virtualised environment
without any modification. The bare metal architecture gives ESX Server complete control over the server
resources allocated to each virtual machine and provides for near native virtual machine performance and
enterprise class scalability. Virtual machines have built in high availability, resource management and security
features that can provide better service levels to software applications than static physical environments.
VMware ESX Server architecture
Source: (VMware) Server Configuration Guide
From a security perspective, VMware Infrastructure consists of several major components:

Virtualisation layer, consisting of the VMkernel and the virtual machine monitor

Virtual machines

ESX Server Service Console

ESX Server virtual networking layer

Virtual storage

VirtualCenter
For each of the components, risks have been assessed independently to allow a methodical approach to
discerning risk and countermeasure.
Note: To assess overall relative risk the countermeasures should be read in conjunction with each other.
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Risk assessments are addressed in sub-sections as per the components list above. Each sub-section provides
an overview, risk assessment and includes any additional best practice configurations.
3.1.1
Definitions
The following definitions were used as reference points within the document.
Potential Impact
Definition
Description
Loss of Confidentiality
Impact of unauthorised disclosure of sensitive information (e.g: contravene any
privacy legislation).
Loss of Integrity
Impact if system or data integrity is lost by unauthorised changes to the data or
system.
Loss of Availability
Impact to system functionality and operational effectiveness.
3.2
General Security Features
3.2.1
Product Overview – VMware ESX
VMware ESX 3 Server presents a generic x86 platform by virtualising four key hardware components:
processor, memory, disk, and network. An operating system is then installed into this virtualised platform. The
virtualisation layer, or VMkernel, is a kernel designed by VMware specifically to run virtual machines. It
controls the hardware utilised by ESX Server hosts and schedules the allocation of hardware resources among
the virtual machines. A Service Console using a modified version of Red Hat Enterprise 3 is accessible and
provides a local management interface and API to the ESX kernel. Because the VMkernel is fully dedicated to
supporting virtual machines and is not used for other purposes, the interface to the VMkernel is strictly limited
to the API required to manage virtual machines. There are no public interfaces to the VMkernel, and it cannot
execute arbitrary code.
The VMkernel alternates among all the virtual machines on the host in running the virtual machine instructions
on the processor. Every time a virtual machine’s execution is stopped, a context switch occurs. During the
context switch the processor register values are saved and the new context is loaded. When a given virtual
machine’s turn comes around again, the corresponding register state is restored.
Each virtual machine has an associated virtual machine monitor (VMM). The VMM uses binary translation to
modify the guest operating system kernel code so it can run in a less-privileged processor ring. This is
analogous to what a Java virtual machine does using just-in-time translation. Additionally, the VMM virtualises
a chip set for the guest operating system to run on. The device drivers in the guest cooperate with the VMM to
access the devices in the virtual chip set. The VMM passes request to the VMkernel to complete the device
virtualisation and support the requested operation.
The following outlines key security features of the product:

Compatibility with SAN security practices. VMware Infrastructure enforces security policies with LUN
zoning and LUN masking.
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
Implementation of secure networking features. VLAN tagging enhances network security by tagging
and filtering network traffic on VLANs, and Layer network security policies enforce security for virtual
machines at the Ethernet layer.

Integration with Microsoft® Active Directory. VMware Infrastructure bases access controls on
existing Microsoft Active Directory authentication mechanisms.

Custom roles and permissions. VMware Infrastructure enhances security and flexibility with userdefined roles which can be managed in a granular way.

Resource pool access control and delegation. VMware Infrastructure secures resource allocation at
different levels and VM management can be delegated accordingly.

Audit trails. VMware Infrastructure maintains a record of significant configuration changes and the
administrator who initiated each one. Reports for event tracking can be exported.

Session management. VMware Infrastructure enables discovery and, if necessary, terminate
VirtualCenter user sessions.

Vulnerability Response. VMware has implemented internal processes to ensure VMware products
meet highest standards for security. The VMware Security Response Policy
(www.vmware.com/vmtn/technology/security/security_response.html) documents VMware’s
commitments for resolving possible vulnerabilities in VMware products.

Security Certification. VMware ESX Server 2.5.0 and VirtualCenter 1.2.0 have been validated under
the U.S. Common Criteria Evaluation and Validation Scheme (CCEVS) process, achieving EAL2
certification. VMware ESX Server 3.0 and VirtualCenter 2.0 are currently being tested for certification
at EAL4+.
The following table details predetermined TCP and UDP ports used for management access to a VirtualCenter
management server, ESX Server host(s) and other network components of a virtual infrastructure built on
VMware ESX.
Port #
Purpose
Traffic Type
80
HTTP access. Redirected to port 443
TCP in
443
HTTPS access
TCP in
902
Authentication traffic from VI client to VirtualCenter or ESX host
TCP in, UDP out
903
Remote console traffic generated by user access to VM’s
TCP in
Traffic between ESX hosts for VMware HA
TCP out, UDP in/out
Incoming requests for VMotion
TCP in/out
Traffic between ESX hosts for VMware HA
TCP out, UDP in/out
27000
License transactions from ESX host to license server
TCP out
27010
License transactions from the license server
TCP in
2050 – 5000
8000
8042 - 8045
In addition to the above, to ensure the protection of data transmitted to and from external network
connections, ESX server uses one of the strongest block ciphers available – 256 bit AES block encryption. ESX
Server also uses 1024 bit RSA for key exchange. These encryption algorithms protect the following
connections:
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
VI client connections to the VC Server and to ESX hosts via the Service Console.

VI Web Access connections to ESX hosts via the Service Console.

Service Console connections to virtual machines through the VMkernel.

SSH connections to the ESX hosts via the Service Console.
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4
ESX Server Service Console
4.1
Overview
Whether using the VI management client or the command line, all configuration tasks for ESX Server are
performed through the Service Console, including configuring storage, controlling aspects of virtual machine
behaviour, and setting up virtual switches or virtual networks. A person logged in to the Service Console with
privileged permissions has the ability to modify, shut down, or even destroy virtual machines on that host.
While VMware ESX Server management clients use authentication and encryption to prevent unauthorised
access to the Service Console, other services might not offer the same protection. If attackers gain access to
the Service Console, they are free to reconfigure many attributes of the ESX Server host. The Service Console
is the point of control for ESX Server and safeguarding it from misuse is crucial.
The ESX Server 3.0 Service Console provides an execution environment to monitor and administer the entire
ESX Server host. The Service Console operating system is a reduced version of Red Hat Enterprise Linux,
Update 6. Much of the functionality not necessary for interacting with the ESX Server virtualisation layer has
been removed, therefore not all vulnerabilities of this distribution apply to the Service Console. VMware
monitors and tracks all known security exploits that apply to this particular reduced version and issues custom
updates as and when needed.
4.2
Risk Assessment
Threat
#
1
Infiltrate Service
Console via untrusted
network
Likelihood
Possible
Potential
Impact
Availability
Integrity
Countermeasure
Connection only to internal
trusted network
No connection allowed to
Internet.
Comments
By default, ESX Server is
installed with a high security
internal firewall setting - all
outbound ports are closed
Only inbound ports that are
open are those required for
interactions with clients such as
the VMware Virtual
Infrastructure Client.
Note: This is the VMware
recommended security setting
unless the Service Console is
connected to a trusted
network.
2
3
Service Console via
client communication
streams
Possible
Service Console via SC
web service
Possible
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Availability
Integrity
Availability
All communications from clients
are encrypted through SSL by
default. Connection uses 256bit AES block encryption and
1024-bit RSA key encryption
Service Console access across
insecure networks such as the
Internet or non-private WAN’s
could open up the risk of a
man-in-the-middle type attack
and is considered unsafe
practice
The Tomcat Web service, used
internally by ESX Server to
support access to the Service
Console by Web clients such as
VMware Virtual Infrastructure
Web Access, has been modified
to run only those functions
required for administration and
monitoring by a Web client.
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Threat
#
4
Likelihood
Potential
Impact
Comments
VMware monitors all security
alerts that could affect Service
Console security and, if needed,
issues a security patch, as it
would for any other security
vulnerability that could affect
ESX Server hosts.
VMware provides security
patches for the Service Console
which uses Red Hat Enterprise
Linux 3, Update 6 and later as
they become available
Insecure services such as FTP
and Telnet are not installed and
the ports for these services are
closed by default.
FTP, SMB and similar can be
required occasionally for
periodic maintenance of the
ESX host. When required these
ports will be opened for the
minimal time required to
complete a required function
then be closed again.
Service Console via Red
Hat vulnerability
Possible
Service Console via
insecure services
Possible
Service Console – via
file/folder permission
change
Possible
7
Service Console via
SNMP
Unlikely
Availability
ESX Server supports SNMPv1,
and the management
information base is read-only.
Nothing can be set through
SNMP management calls.
8
Service Console via
common network
Unlikely
Availability
Isolate Service Console by
creating a separate VLAN.
Configure network access for
management tool connections
with the Service Console
through a single virtual switch
and one or more uplink ports.
For this project, ESX servers are
located on an internal trusted
network and network isolation
via separate firewalled VLAN
will be used.
ESX Server 3 includes a firewall
between the Service Console
and the network. By default,
the Service Console firewall is
configured at the high security
setting, which blocks all
incoming and outgoing traffic
except for that on ports 902, 80,
443, and 22, which are used for
basic communication with ESX
Server.
Any ports opened on a full time
basis, will be documented in the
design, including the purpose
for opening each port.
5
6
9
Service Console via
tcp/udp port
Availability
Countermeasure
Integrity
Availability
Integrity
Availability
Integrity
Integrity
Possible
Availability
Integrity
The number of applications that
use a setuid or setgid flag has
been minimised.
This prevents anyone without
access to the Service Console
VLAN or virtual switch from
viewing traffic to and from the
Service Console. Also prevents
attackers from sending any
packets to the Service Console.
The server could be vulnerable
to a DoS attack using the
default ports. Additionally
placing ESX servers behind a
hardware firewall is considered
a good practice
countermeasure.
Furthermore, the ‘iptables’
program within the Service
Console can be used to further
restrict network access to a
more granular level, eg: by
subnet, nominated ip list.
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Threat
#
Likelihood
Potential
Impact
Countermeasure
Comments
10
Service Console via
applications and
services running in the
console
Unlikely
Availability
Additional software that could
run in the Service Console
includes management agents
and backup agents. Services
that could run include NIS,
SNMP, or CIM HTTPS. Software
will be limited to core support
requirements for Enterprise
Management systems such as
hardware monitoring and
backup.
The more components there
are running in the Service
Console, the more potential
objects are susceptible to
security vulnerabilities so will
be kept to a minimum.
11
Managing the Service
Console as a Linux host
Likely
Availability
Strict operating processes,
logging, file integrity checks.
The Service Console is
generated from a Red Hat Linux
distribution that has been
carefully stripped down and
modified to provide exactly the
functionality necessary to
communicate with and allow
management of the VMkernel.
Any additional software
installed should not make
assumptions about what RPM
packages are present, nor that
they can modify them. In many
cases, the packages that do
exist have been modified
especially for ESX Server.
Integrity
Confidentiality
12
Malicious code
Possible
Availability
Note: the Service Console is not
be treated like a Linux host
when it comes to patching.
Patches issued by Red Hat or
any other third-party vendor
are never to be installed.
Follow VMware best practice to
configure Service Console
network isolation to an internal
trusted network.
Because ESX Server runs a
customised, locked-down
version of Linux, there is much
less likelihood of security
exploits than in a standard
Linux distribution.
VMware state that if you follow
the best practice of isolating the
network for the Service
Console, there is no reason to
run any antivirus or other such
security agents, and their use is
not recommended.
13
Unauthorised
modification of key
Service Console
configuration files (file
system integrity)
Possible
Integrity
Key configuration files should
be monitored for integrity and
unauthorised tampering.
/etc/profile
The design will specify use of
using a tool such as Tripwire, or
a checksum tool such as
sha1sum which is built into the
Service Console.
/etc/ssh/sshd_config
/etc/pam.d/system_auth
/etc/ntp
/etc/ntp.conf
/etc/passwd
/etc/group
/etc/sudoers
/etc/shadow
/etc/vmware/
These files are also to be
backed up regularly.
14
Internal attack or user
error on ESX Service
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Possible
Availability
Use VirtualCenter via VI Client
There are some tasks that
cannot be performed via the VI
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Threat
#
Likelihood
Console
Potential
Impact
Integrity
Countermeasure
*1
The best measure to prevent
security incidents in the ESX
Service Console is to avoid
accessing it if at all possible.
Many of the tasks necessary to
configure and maintain the ESX
Server host can be achieved
using the VI Client, either
connected directly to the host,
or, preferably through
VirtualCenter. The VI Client
communicates using a welldefined API, which limits what
can be done. This is safer than
direct execution of arbitrary
commands.
Connectivity of ssh based client
communication tools such as
putty, winscp etc.. will be
limited to a discrete group of ip
addresses belonging to the
physical / virtual desktops of
the Windows Infrastucture
Management Team staff.
Limiting the connectivity will be
achieved by utilising the
/etc/hosts.allow and
/etc/hosts.deny files within
VMware ESX. The best practice
approach to this is to deny
access based on subnet range,
only allowing access based on ip
address exception.
15
Denial of Service attack
by filling up root
partition
Possible
Availability
Create separate partitions for
/home, /tmp, and /var/log.
These are all directories that
have the potential to fill up.
Comments
Client. For these tasks, you
must log in to the Service
Console. Also, if the connection
is lost to the host, executing
certain of these commands
through the command-line
interface may be the only
recourse, eg: if the network
connection fails and you are
therefore unable to connect
using VI Client.
There may be some cases in
which you want to automate
certain configuration tasks
using scripts that run in the
Service Console, but for
interactive administration, VI
Client is the most secure access
method.
A login 'grace-time' setting will
be configured to ensure idle ssh
sessions are not left connected
to an ESX Server host
indefinitely
If not isolated from the root
partition, a denial of service
could be experienced if the root
partition is full and unable to
accept any more writes.
*1. VirtualCenter has the added benefit that authorisation and authentication are performed via the standard central Active Directory
service, instead of using special local accounts in the Service Console. In addition, roles and users are stored in a database, providing an
easy way to view the current permissions as well as take a snapshot of them. VirtualCenter also keeps track of every task invoked through
it, providing an automatic audit trail.
4.3
Additional Best Practice Configuration
The following best practice configurations will be adopted within the design for this project.
Maintain Thorough Logging
In addition to identifying system issues, logging allows tracking of any unusual activity that might be a
precursor to an attack and also allows a post-mortem to be carried out on any compromised systems.
Log files can be accessed by navigating to the /var/log/ directory and provide an important tool for diagnosing
security breaches as well as other system issues. They also provide key sources of audit information. In
addition to storing log information in files on the local file system, you can send this log information to a
remote system. The syslog program is typically used for computer system management and security auditing,
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and it can serve these purposes well for ESX Server hosts. You can select individual Service Console
components for which you want the logs sent to a remote system.
The following tips provide best practices for logging:

Ensure accurate time-keeping.

Control growth of log files.

Use remote syslog logging.

Remote logging to a central host provides a way to greatly increase administration capabilities. By
gathering log files onto a central host, you can easily monitor all hosts with a single tool as well as do
aggregate analysis and searching to look for things like coordinated attacks on multiple hosts.

Use local and remote sudo logging.

If you have configured sudo to enable controlled execution of privileged commands, you can benefit
from using syslog to audit use of these commands. The following instructions show how to log all
privileged command executions using syslog. You can then benefit from the other syslog features
such as remote logging and log file rotation.

Configure sudo to use syslog to record all occurrences of its use.

Add an entry to /etc/syslog.conf to send the logging information to a file and, optionally, to a remote
host.

In ESX Server 3, only SNMPv1 is supported, and only for queries.
Use a Directory Service for Authentication for access to the ESX Server Service Console
Advanced configuration and troubleshooting of an ESX Server host may require local privileged access to the
Service Console. For this circumstance, it is recommended to set up individual host-localised user accounts and
groups for selected administrators with overall responsibility for your virtual infrastructure. These accounts
would correspond to real individuals and not be accounts shared by multiple people. More preferable, and as
proposed for the project will be to configure the server to authenticate users via Active Directory thereby
centralising accounts and allowing continuity of existing policies for password complexity, aging and reuse.
Note: Although you can create host local accounts on the Service Console that correspond to each global account, this presents the
problem of having to manage user names and passwords in multiple places. It is recommended to use a directory service, such as NIS or
LDAP, to define and authenticate users on the Service Console, so local user accounts do not have to be created.
Because Service Console authentication is Unix-based, it cannot use Active Directory to define user accounts.
However, it can use Active Directory to authenticate users. Individual user accounts can be defined on the
host, then use the local Active Directory domain to manage the passwords and account status.
Root User Logon
The root user of the Service Console has almost unlimited capabilities, and securing this account is important
to secure the ESX Server host. By default, remote access via ssh is enabled, but not for the root account. Files
can be copied remotely to and from the Service Console using an scp (secure cp) client, such as WinSCP.
Enabling remote root access is not recommended, because it opens the system to network based attack
should someone obtain the root password. The recommended approach is to log in remotely using a regular
user account, then use sudo to perform privileged commands.
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Note: The sudo command enhances security because it grants root privileges only for select activities, in contrast with the su
command, which grants root privileges for all activities. Using sudo also provides superior accountability because all sudo activities are
logged, whereas if you use su, ESX Server only logs the fact that the user switched to root by way of su. The sudo command also provides a
way for you to grant or revoke execution rights to commands on an as-needed basis.
Root access can be disallowed on the console of the ESX Server host. This approach forces anyone who wants
to access the system to first log in using a regular user account, then use sudo or su to perform tasks. If
disallowing root login on the console, a non-privileged account on the host should be created to enable logins.
This should be a local account so that in case the network connection to the directory service is lost, access to
the host is still possible. Access can be assured by defining a local password for this account, which will then
override authentication via directory services. The net effect is that administrators can still access the system,
but they never have to log in as root. Instead, they use sudo to perform particular tasks or su to perform
arbitrary commands.
Because su is a powerful command, access will be limited to it. By default, only users that are members of the
wheel group in the Service Console have permission to run su. If a user attempts to run su - to gain root
privileges and that user is not a member of the wheel group, the su - attempt fails and the event is logged.
The following list of recommendations for using sudo for the project will be :

Configure local and remote sudo logging.

Create a special admins group and allow only members of that group to use sudo.

Use sudo aliases to determine the authorisation scheme, then add and remove users in the alias
definitions instead of in the commands specification.

Be careful to permit only the minimum necessary operations to each user and alias. Permit very few
users to run the su command, because su opens a shell that has full root privileges but is not
auditable.

Require users to enter their own passwords when performing operations. This is the default setting.
Do not require the root password, because this presents a security risk, and do not disable password
checking.
In sudo the authentication only persists for a brief period of time before sudo asks for a password again.
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5
ESX Server Kernel (Virtualisation layer)
5.1
Overview
The virtualisation layer, or VMkernel, is a kernel designed by VMware from the ground up to run virtual
machines. It controls the hardware utilised by ESX Server hosts and schedules the allocation of hardware
resources among the virtual machines. Because the VMkernel is fully dedicated to supporting virtual machines
and is not used for other purposes, the interface to the VMkernel is strictly limited to the API required to
manage virtual machines.
5.2
Risk Assessment
Threat
#
Likelihood
Potential
Impact
Countermeasure
Comments
1
Buffer Overflow attack
Possible
Availability
To provide an extra layer of
security, the VMM supports the
buffer overflow prevention
capabilities built in to most Intel
and AMD CPUs, known as the
NX or XD bit. Since the binary
translator does not operate on
translation units of more than
12 instructions, it is not possible
for the translator to experience
a buffer overflow for this
operation.
Buffer overflow attacks usually
exploit code that operates on
unconstrained input without
doing a length check. If it is
possible to provide a very, very
long string and the code that
operates on the string has a
fixed size buffer, and it does not
perform length checks, a buffer
overflow occurs and may be
used in an attack.
2
Hyperthreading
exploits
Unlikely
Availability
ESX Server virtual machines do
not provide hyperthreading
technology to the guest
operating system. ESX Server,
however, can utilise
hyperthreading to run two
different virtual machines
simultaneously on the same
physical processor. However,
because virtual machines do
not necessarily run on the same
processor continuously, it is
more challenging to exploit the
vulnerability discussed above.
Intel’s hyperthreading
technology allows two process
threads to execute on the same
CPU package. These threads can
share the memory cache on the
processor. Malicious software
can exploit this feature by
having one thread monitor the
execution of another thread,
possibly allowing theft of
cryptographic keys.
3
Memory virtualisation
exploits*1
Unlikely
Availability
When a virtual machine needs
memory, each memory page is
zeroed out by the VMkernel
before being handed to the
virtual machine. Normally, the
virtual machine then has
exclusive use of the memory
page, and no other virtual
machine can touch it or even
see it.
Any attempt by the operating
system or any application
running inside a virtual machine
to address memory outside of
what has been allocated by the
VMM would cause a fault to be
delivered to the guest operating
system, typically resulting in an
immediate system crash, panic,
or halt in the virtual machine,
depending on the operating
system. This is often termed
‘hyperspacing’, when a
malicious guest operating
system attempts I/O to an
address space that is outside
normal boundaries.
4
Memory leak through
Transparent Page
sharing
Not Possible
N/A
As soon as any one virtual
machine tries to modify a
shared page, it gets its own
private copy. Because shared
Transparent page sharing is a
technique for using memory
resources more efficiently.
Memory pages that are
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#
Threat
Likelihood
Potential
Impact
Countermeasure
Comments
memory pages are marked
copy-on-write, it is impossible
for one virtual machine to leak
private information to another
through this mechanism.
Transparent page sharing is
controlled by the VMkernel and
VMM and cannot be
compromised by virtual
machines.
identical in two or more virtual
machines are stored once in the
host system’s RAM, and each of
the virtual machines has readonly access. Such shared pages
are common, for example, if
many virtual machines on the
same host run the same
operating system.
*1. The RAM allocated to a virtual machine by the VMM is defined by the virtual machine’s BIOS settings. The memory is allocated by the
VMkernel when it defines the resources to be used by the virtual machine. A guest operating system uses physical memory allocated to it
by the VMkernel and defined in the virtual machine’s configuration file.
The operating system that executes within a virtual machine expects a zero-based physical address space, as provided by real hardware.
The VMM gives each virtual machine the illusion that it is using such an address space, virtualising physical memory by adding an extra
level of address translation. A machine address refers to actual hardware memory, while a physical address is a software abstraction used
to provide the illusion of hardware memory to a virtual machine.
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6
ESX Server Virtual Networking Layer
6.1
Overview
The virtual networking layer consists of the virtual network devices through which virtual machines and the
Service Console interface with the rest of the network. ESX Server relies on the virtual networking layer to
support communications between virtual machines and their users. In addition, ESX Server hosts use the
virtual networking layer to communicate with iSCSI SANs, NAS storage, and so forth. The virtual networking
layer includes virtual network adapters and the virtual switches.
VMware ESX Server virtual networking layer
Source: (VMware) Server Configuration Guide
VMware Infrastructure 3 provides virtual network adapters to guest operating systems that have these
characteristics:

They have their own MAC addresses and unicast/multicast/broadcast filters.

They are strictly layered Ethernet adapter devices.

They interact with the low-level VMkernel layer stack via a common API.
The ESX Server 3 networking stack uses a modular design for flexibility. A virtual switch is “built to order” at
run time from a collection of small functional units, such as:

The core layer forwarding engine

VLAN tagging, stripping, and filtering units

Virtual port capabilities specific to a particular adapter or a specific port on a virtual switch

Level security, checksum, and segmentation offload units
When the virtual switch is built at run time, ESX Server loads only those components it needs. It installs and
runs only what is actually needed to support the specific physical and virtual Ethernet adapter types used in
the configuration.
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The following diagram shows how various networks can be segregated within an ESX Server host.
Network Segregation
Source: (VMware) Server Configuration Guide
6.2
Risk Assessment
Threat
#
1
Attack via Virtual
Switch integrity
Likelihood
Unlikely
Potential
Impact
Confidentiality
Integrity
Countermeasure
Comments
ESX Server provides no path for
network data to cross between
virtual switches.
A common cause of traffic leaks
in the world of physical
switches is cascading; often
needed because physical
switches have a limited number
of ports. Because each virtual
switch provides 1016 ports
there is no code to connect
virtual switches.
Virtual switches cannot share
physical Ethernet adapters, so
there is no way to fool the
Ethernet adapter into doing
loopback or something similar
that would cause a leak
between virtual switches
Each virtual switch has its own
forwarding table, and there is
no mechanism in the code to
allow an entry in one table to
point to a port on another
virtual switch. In other words,
every destination the switch
looks up must match ports on
the same virtual switch as the
port where the frame
originated, even if other virtual
switches’ lookup tables contain
entries for that address.
2
VM’s or other network
nodes influencing
Virtual Switch
behaviour
xtravirt.com
Unlikely
Availability
Virtual switches do not learn
from the network in order to
populate their forwarding
tables. This eliminates an entry
denial-of-service (DoS) or
leakage attacks, either as a
direct DoS attempt or, more
There are natural limits to
virtual switch isolation. If you
connect the uplinks of two
virtual switches together, or if
you bridge two virtual switches
with software running in a
virtual machine, you open the
door to the same kinds of
problems you might see in
physical switches.
Virtual switches make private
copies of any frame data used
to make forwarding or filtering
decisions.
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Threat
#
Likelihood
Potential
Impact
Countermeasure
Comments
likely, as a side effect of some
other attack, such as a worm or
virus, as it scans for vulnerable
hosts to infect.
3
4
Unintended inter-VLAN
traffic flow
Network attack via
Virtual Switch VLAN’s
Unlikely /
Not Possible
Unlikely
Confidentiality
Confidentiality
Integrity
Availability
It is important to ensure that
frames are contained within the
appropriate VLAN on a virtual
switch. ESX Server does so in
the following ways:

VLAN data is carried outside
the frame as it passes
through the virtual switch.
Filtering is a simple integer
comparison. This is really
just a special case of the
general principle that the
system should not trust
user accessible data.

Virtual switches have no
dynamic trunking support.

Virtual switches have no
support for what is referred
to as native VLAN.
Recommend creation of VLANs
as they provide the almost all of
the security benefits inherent in
implementing physically
separate networks without the
hardware overhead.
Also recommend use separate
physical network adapters for
virtual machine zones to ensure
that the zones are isolated.
5
Network breach by
user error or omission
Possible
Confidentiality
Availability
ESX Server supports IEEE 802
.1q VLANs, which can be used
to further protect the virtual
machine network, Service
Console, or storage
configuration. This driver is
written by VMware according
to the IEEE specification. VLANs
allow you to segment a physical
network so that two machines
on the same physical network
cannot send packets to or
receive packets from each other
unless they are on the same
VLAN.
Label all virtual networks
appropriately to prevent
confusion or security
compromises. This labelling
prevents operator error due to
a virtual machine being
attached to a network it is not
authorised for or to a network
that could allow the leakage of
sensitive information.
In the case of the project design
sensitive networks are
physically segregated from each
other by using clusters of
physical ESX hosts.
6
MAC address spoofing
Possible
Confidentiality
Virtual switch security profiles
on ESX Server hosts can protect
against this type of attack with
two options, which are set per
virtual switch:

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MAC address changes — By
default, this option is set to
Accept. To protect against
Each virtual network adapter in
a virtual machine has its own
initial MAC address assigned
when the adapter is created. In
addition, each adapter has an
effective MAC address that
filters out incoming network
traffic with a destination MAC
address different from the
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Threat
#
Likelihood
Potential
Impact
Countermeasure
MAC impersonation, you
can set this option to
Reject. ESX Server then will
not honour requests to
change the effective MAC
address to anything other
than the initial MAC
address. The port that the
virtual adapter used to send
the request is disabled and
as a result, the virtual
adapter does not receive
any more frames until it
changes the effective MAC
address to match the initial
MAC address. The guest
operating system does not
detect that the MAC
address change has not
been honoured.

Forged transmissions — By
default, this option is set to
Accept, meaning ESX Server
does not compare source
and effective MAC
addresses. The Forged
Transmits option setting
affects traffic transmitted
from a virtual machine. If
you set this option to
Reject, ESX Server compares
the source MAC address
being transmitted by the
operating system with the
effective MAC address for
its adapter to see if they
match. If the addresses do
not match, ESX Server drops
the packet. The guest
operating system does not
detect that its virtual
network adapter cannot
send packets using the
impersonated MAC address.
ESX Server intercepts any
packets with impersonated
addresses before they are
delivered, and the guest
operating system might
assume that the packets
have been dropped.
Comments
effective MAC address.
Upon creation, a network
adapter’s effective MAC
address and initial MAC address
are the same. However, the
virtual machine’s operating
system can alter the effective
MAC address to another value
at any time. If an operating
system changes the effective
MAC address, its network
adapter then receives network
traffic destined for the new
MAC address. The operating
system can send frames with an
impersonated source MAC
address at any time. Thus, an
operating system can stage
malicious attacks on the devices
in a network by impersonating a
network adapter authorised by
the receiving network.
Within the design both of these
options will be set to Reject.
6.3
Additional Best Practice configuration
The following best practice configurations will be adopted within the design for this project.
Do Not Create a Default Port Group
During ESX Server installation, there is an option to create a default virtual machine port. However, this option
creates a virtual machine port group on the same network interface as the Service Console. If this setting is left
unchanged, it could allow virtual machines to detect sensitive and often unencrypted information. Since the
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Service Console should always be on a separate, private network, this option should never be used except in a
test environment. This option will be disabled in the standard VMware ESX Server image for this project.
Use a Dedicated, Isolated Network for VMotion and iSCSI
Because VMotion information is not encrypted, the entire state of a virtual machine could potentially be
snooped on the network used for VMotion. Therefore, it is critical that this network be isolated from any other
use. To encrypt VMotion traffic, there is the option of using hardware-based SSL encryption. Encryption is not
available for iSCSI disk I/O, so this network should be strictly controlled, too. In the case of the project design
the network for VMotion will be dedicated, isolated and non-routable.
Do Not Use Promiscuous Mode on Network Interfaces
ESX Server has the ability to run virtual network adapters in promiscuous mode. Promiscuous mode may be
enabled on virtual switches that are bound to a physical network adapter (vmnic) and virtual switches that do
not bind to a physical network adapter (vmnet). When promiscuous mode is enabled for a vmnic switch, all
virtual machines connected to the virtual switch have the potential of reading all packets sent across that
network, from other virtual machines as well as any physical machines or other network devices. When
promiscuous mode is enabled for a vmnet switch, all virtual machines connected to the vmnet switch have the
potential of reading all packets across that network — that is, traffic among the virtual machines connected to
that vmnet switch.
While promiscuous mode can be useful for tracking network activity, it is an insecure mode of operation
because any adapter in promiscuous mode has access to the packets regardless of whether some of the
packets should be received only by a particular network adapter. This means that an administrator or root user
within a virtual machine can potentially view traffic destined for other guest operating systems. Promiscuous
mode should only be used for security monitoring, debugging, or troubleshooting.
By default, promiscuous mode is set to Reject and will remain so in the standard VMware ESX server image for
this project.
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7
Virtual Machines
7.1
Overview
Virtual machines are the containers in which guest operating systems and their applications run. By design, all
VMware virtual machines are isolated from one another. Virtual machine isolation is imperceptible to the
guest operating system. Even a user with system administrator privileges or kernel system level access on a
virtual machine’s guest operating system cannot breach this layer of isolation to access another virtual
machine without privileges explicitly granted by the ESX Server system administrator.
This isolation enables multiple virtual machines to run securely while sharing hardware and ensures both their
ability to access hardware and their uninterrupted performance. For example, if a guest operating system
running in a virtual machine crashes, other virtual machines on the same ESX Server host continue to run. The
guest operating system crash has no effect on:

The ability of users to access the other virtual machines

The ability of the running virtual machines to access the resources they need

The performance of the other virtual machines
Each virtual machine is isolated from other virtual machines running on the same hardware. While virtual
machines share physical resources such as CPU, memory, and I/O devices, a guest operating system in an
individual virtual machine cannot detect any device other than the virtual devices made available to it.
Virtual Machine Resources
Source: (VMware) Server Configuration Guide
7.2
Risk Assessment
Threat
#
1
Attack VM via
communication path
from another VM on
same ESX server
xtravirt.com
Likelihood
Not possible
Potential
Impact
Availability
Countermeasure
Comments
Because the VMkernel and
VMM mediate access to the
physical resources and all
physical hardware access takes
place through the VMkernel,
virtual machines cannot
Just as a physical machine can
communicate with other
machines in a network only
through a network adapter, a
virtual machine can
communicate with other virtual
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Threat
#
2
Denial of Service attack
via resource starvation
Likelihood
Possible
Potential
Impact
Availability
Countermeasure
circumvent this level of
isolation.
machines running on the same
ESX Server host only through a
virtual switch. Further, a virtual
machine communicates with
the physical network, including
virtual machines on other ESX
Server hosts, only through a
physical network adapter.
By default, ESX Server imposes
a form of resource reservation
by applying a distribution
algorithm that divides the
available host resources equally
among the virtual machines
while keeping a certain
percentage of resources for use
by system components, such as
the Service Console. This
default behaviour provides a
degree of natural protection
from denial-of-service and
distributed denial-of-service
attacks.
Resource reservations and
limits protect virtual machines
from performance degradation
if another virtual machine tries
to consume too many resources
on shared hardware. For
example, if one of the virtual
machines on an ESX Server host
is incapacitated by a denial-ofservice or distributed denial-ofservice attack, a resource limit
on that machine prevents the
attack from taking up so many
hardware resources that the
other virtual machines are also
affected. Similarly, a resource
reservation on each of the
virtual machines ensures that,
in the event of high resource
demands by the virtual machine
targeted by the denial-ofservice attack, all the other
virtual machines still have
enough resources to operate.
Resource reservations and
limits can be set on an
individual basis if you want to
customise the default
behaviour so the distribution is
not equal across all virtual
machines on the host.
3
Virtual Machine
security risks - general
Possible
Confidentiality
Integrity
Availability
Comments
In every virtual machine in the
virtual infrastructure, antivirus
agents, spyware filters,
intrusion detection systems,
and any other standard security
measures present on physical
servers should be installed and
kept up to date including
patching.
The project design will require
all virtual machine servers to
maintain current standard
security measures.
4
Attack via VI Console
xtravirt.com
Possible
Availability
The project design will be based
upon role based administrative
tiers to restrict use of the VI
Console to as few operatives as
required. The standard console
access route for virtual
machines will be via RDP.
The VI Console allows a user to
connect to the console of a
virtual machine, in effect seeing
what a monitor on a physical
server would show. However,
the VI Console also provides
power management and
removable device connectivity
controls, which could
potentially allow a malicious
user to bring down a virtual
machine. In addition, it also has
a performance impact on the
Service Console, especially if
many VI Console sessions are
open simultaneously. Instead of
VI Console, use native remote
management services, such as
terminal services and ssh, to
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Threat
#
Likelihood
Potential
Impact
Countermeasure
Comments
interact with virtual machines.
7.3
Additional Best Practice configuration
The following best practice configurations will be adopted within the Low Level design for this component.
Create template images
Only approved pre-hardened and patched server images will be available for deployment.
VM Configuration Options
Unneeded devices such as cd, floppy, usb drives will be disconnected by default on virtual machines and only
approved staff will have rights to modify based upon role based permissions.
Copy and paste operations between the guest operating system and remote console will be disabled so that
sensitive information can not be inadvertently copied over.
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8
Virtual Storage
8.1
Overview
Virtual disk files are stored on high performance shared storage such as Fibre Channel or iSCSI SAN. VMFS is a
cluster file system which enables multiple installations of ESX Server to have concurrent fast access to the
same virtual machine storage. Since virtual machines are hardware independent and portable across servers,
VMFS ensures that individual servers are not single points of failure and enables resource balancing across
multiple servers.
Fibre Channel HBA consolidation allows the sharing of storage network components across many virtual
machines while maintaining hardware fault tolerance.
Virtual Storage
Source: (VMware) vmware.com
8.2
Risk Assessment
Threat
#
1
Unauthorised
presentation of SAN
based data from other
sources
Likelihood
Unlikely
Potential
Impact
Integrity
Confidentiality
Countermeasure
Comments
Zoning and LUN masking are
implemented to segregate SAN
activity. Where applicable, this
methodology will be
maintained in the context of
this project.
Zoning provides access control
in a SAN topology; it defines
which host bus adapters (HBAs)
can connect to which SAN
device storage processors.
When a SAN is configured using
zoning, the devices outside a
zone are not visible to the
devices inside the zone. In
addition, SAN traffic within each
zone is isolated from the other
zones.
LUN masking is commonly used
for permission management.
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Threat
#
Likelihood
Potential
Impact
Countermeasure
Comments
LUN masking is performed at
the storage processor or server
level; it makes a LUN invisible
when a target is scanned. The
administrator configures the
disk array so each server or
group of servers can see only
certain LUNs.
2
Data capture or Denial
of Service attack via
virtualised storage
xtravirt.com
Unlikely
Integrity
Confidentiality
Virtual machines have no
knowledge or understanding of
Fibre Channel. The only storage
available to virtual machines is
on SCSI devices. Each virtual
machine is able to see only the
virtual disks that are presented
to it on its virtual SCSI adapters.
This isolation is complete, with
regard to both security and
performance. A VMware virtual
machine has no visibility into
the WWN (world wide name),
the physical Fibre Channel
HBAs, or even the target ID or
other information about the
LUNs upon which its virtual
disks reside. The virtual
machine is isolated to such a
degree that software executing
in the virtual machine cannot
even detect that it is running on
a SAN fabric. Even multipathing
is handled in a way that is
transparent to a virtual
machine. Additionally, virtual
machines can be configured to
limit the bandwidth they use to
communicate with storage
devices. This prevents the
possibility of a denial-of-service
attack against other virtual
machines on the same host by
one virtual machine taking over
the Fibre Channel HBA.
A virtual machine does not have
virtual Fibre Channel HBAs but
only has virtual SCSI adapters.
A host running ESX Server is
attached to a Fibre Channel
SAN in the same way that any
other host is. It uses Fibre
Channel HBAs, with the drivers
for those HBAs installed in the
software layer that interacts
directly with the hardware. In
environments that do not
include virtualisation software,
the drivers are installed on the
operating system, but for ESX
Server, the drivers are installed
in the ESX Server VMkernel. ESX
Server also includes VMware
Virtual Machine File System
(VMware VMFS), a distributed
file system and volume
manager that creates and
manages virtual volumes on top
of the LUNs that are presented
to the ESX Server host. Those
virtual volumes, usually
referred to as virtual disks, are
allocated to specific virtual
machines.
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9
VirtualCenter
9.1
Overview
VirtualCenter is composed of five main components:

VirtualCenter Management Server is the central control node for configuring, provisioning and
managing virtualised IT environments.

VirtualCenter Database is used to store persistent information about the physical servers, resource
pools and virtual machines managed by the VirtualCenter Management Server. The database resides
on standard versions of Oracle, Microsoft® SQL Server, or Microsoft® MSDE.

Virtual Infrastructure Client allows administrators and users to connect remotely to the VirtualCenter
Management Server or individual ESX Servers from any Windows PC.

VirtualCenter Agent connects VMware ESX Servers with the VirtualCenter Management Server.

Virtual Infrastructure Web access allows virtual machine management and access to virtual machine
graphical consoles without installing a client.
VMware VirtualCenter Overview
Source: (VMware) vmware.com
9.2
Risk Assessment
Threat
#
1
Non-specific attack on
Windows host running
VirtualCenter
Likelihood
Possible
Potential
Impact
Availability
Integrity
Countermeasure
Comments
The standard set of
recommendations applies, as it
would for any host: install
antivirus agents, spyware filters,
intrusion detection systems,
and any other standard security
measures present on physical
servers should be installed and
kept up to date including
patching.
The design will require all
virtual machine servers to meet
or exceed standard security
measures.
xtravirt.com
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28
Threat
#
2
3
Likelihood
Error or omission by
use of administrative
access
Possible
Unauthorised
modification of key
VirtualCenter
configuration (system
integrity)
Possible
Potential
Impact
Availability
Integrity
Availability
Integrity
Countermeasure
Comments
VirtualCenter runs as a user
that requires local
administrator privilege and
must be installed by a local
administrative user. To limit the
scope of administrative access,
it is recommended to avoid
using the Windows
Administrator user to run
VirtualCenter installation.
Instead a dedicated
VirtualCenter administrator
account is to be used.
This avoids automatically
providing administrative access
to domain administrators, who
could belong to the local
Administrators group. It also
provides a way of accessing
VirtualCenter when the domain
controller is down, because the
local VirtualCenter
administrator account does not
require remote authentication.
For compliance and auditing, it
is recommended that a record
of various configurations over
time. To capture these it is
recommended to use the
‘Generate VirtualCenter Server’
log bundle command, in the
VMware program file menu on
the VirtualCenter host. This tool
was designed to capture
information to be used for
troubleshooting and debugging,
but the resulting archive file
serves as a convenient way to
maintain a historical record.
Although most of a VMware
Infrastructure environment is
defined by information
contained in the VirtualCenter
database, certain important
configuration information
resides only on the
VirtualCenter Server host’s local
file system. This includes the
main configuration file vpxd.cfg,
various log files, and, implicitly,
the Windows registry settings
that pertain to VirtualCenter.
For the design this task will be
planned for on a regular basis,
so as to track changes made to
the VirtualCenter configuration
over time.
9.3
The resulting ZIP archive
includes:

licmgr_reg.txt, odbc_reg.txt,
vmware_reg.txt — all the
relevant Windows registry
entries

vpxd.cfg — the main
VirtualCenter Server
configuration file (in XML
format)

vpxd-*.log — log files for
VirtualCenter Server

lmgrd.log — log file for the
license server (if present)
Additional Best Practice Configuration
The following best practice configurations will be adopted within the Low Level design for this component.
Role Based Administration
VirtualCenter has a advanced system of roles and permissions, to allow granular determination of
authorisation for administrative and user tasks, based on user or group and inventory item, such as clusters,
resource pools, and hosts. This system ensures that only the minimum necessary privileges are assigned to
people in order to prevent unauthorised access or modification. Custom task based roles can also be defined
to specifically tailor user access and functionality. The design will detail role based administration access to
VirtualCenter deployments.
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Limit Network Connectivity to VirtualCenter
The only network connection VirtualCenter requires is to the ESX Server Service Console and to a network on
which instances of VI Client are running. Avoid putting the VirtualCenter server on any other network, such as
your production or storage networks. Limiting network connectivity reduces the possible avenues of attack.
It is recommended to further protect the VirtualCenter server using a firewall. This firewall may sit between
the clients and the VirtualCenter server, or both the VirtualCenter Server and the clients may sit behind the
firewall, depending on the deployment. The main consideration is ensuring that a firewall is present at what is
considered to be an entry point for the system as a whole.
Note: Networks configured with a VirtualCenter server can receive communications from several types of clients: the VI Client, VI Web
Access, or third-party network management clients that use the SDK to interact with the host. During normal operation, VirtualCenter
listens on designated ports for data from the hosts it is managing and from clients. VirtualCenter also assumes that the hosts it is
managing listen for data from VirtualCenter on designated ports. If a firewall is present between any of these components, it must be
ensured that the appropriate ports are open to support data transfer through the firewall.
Ensure Proper Security Measures Are Used when Configuring the Database for VirtualCenter
It is recommended to install the VirtualCenter database on a separate server and subject it to the same
security measures as any production database. Permissions used for access should be configured to the
database to the minimum necessary.
Enable Full and Secure Use of Certificate-based Encryption
All versions of VMware products, including all releases of VirtualCenter Server use X.509 certificates to encrypt
session information sent over SSL (secure sockets layer protocol) connections between server and client
components.
During the installation of VMware products, default, self-signed certificates are automatically generated.
However, the default certificates generated by VirtualCenter up to and including version 2.0.1 Patch 1 are
defective and should not be used.
Note: By contrast, the default certificates generated by ESX Server hosts are valid and can be used as-is. This requires that any VI Client
that wishes to connect to ESX Server directly (that is, without going through VirtualCenter), must pre-trust the default certificates.
For environments that require strong security, VMware recommends that administrators replace all default
self-signed certificates generated at installation time with legitimate certificates signed by their local root
certificate authority or public, third-party certificates available from multiple public certificate authorities.
Server-certificate verification on all VI Client installations and the VirtualCenter host should be enabled. This
involves a modification to the Windows registry on all client hosts.
Note: VirtualCenter asks for root credentials when it first connects to an ESX Server host. The root password for that host is cached
only long enough to enable VirtualCenter management functionality, and the communication channel to the host is encrypted.
VirtualCenter then creates a user called vpxuser with a pseudo-randomly generated password and uses the vpxuser account for
subsequent connections and management operations. The vpxuser account for each ESX Server host has a unique, 32 -character (2 56-bit)
password that is generated from a cryptographically random string of data that is mapped to a set of legal password characters. Once
generated, the password is encrypted using 102 4-bit RSA key encryption. The password is also stored encrypted on the host, as any local
account password would be.
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The vpxuser account is created for VirtualCenter management when a host is added to VirtualCenter and is used only to authenticate the
connection between VirtualCenter and the ESX Server host. Entries corresponding to the account are added to /etc/passwd and
/etc/shadow, but no process actually runs as vpxuser on ESX Server.
The vpxuser password is reset every time a host is added to VirtualCenter. If VirtualCenter is disconnected from a host, it tries to
reconnect with the vpxuser and password that is stored encrypted in the VirtualCenter database. If that fails, the user is prompted to
reenter the root password so the system can reset (that is, automatically generate a new password for the vpxuser account).
In the VirtualCenter code, database specific variable protection mechanisms, such as parameterised queries in SQL Server are used
extensively, thereby greatly reducing the risk of any SQL injection attack. The VIM API, which is the main SDK library, allows for a
mechanism to specify privileges necessary to invoke the API as part of the API definition. This ensures that security implications are taken
into consideration from the beginning of writing a new API.
This concludes the VMware® Virtual Infrastructure3 Risk Assessment.
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