BitVisor is a security-focused virtual machine monitor (VMM) developed in Japan with the goals of encrypting storage and networks and using smart cards for authentication and key management. It uses a para-virtualization approach where most device I/O is passed through directly to the guest operating system, unlike Xen which uses full virtualization and device emulation. This makes BitVisor's VMM smaller and lower overhead than Xen. Experimental results showed BitVisor running Windows and Linux guests with encryption of storage and networking.
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XS Japan 2008 BitVisor English
1. Xen Summit Tokyo 2008
マスタ サブタイトルの書式設定
Takahiro Shinagawa
University of Tsukuba
Introduction to BitVisor and
Comparison with Xen
2008/11/21 Xen Summit Tokyo 2008
2. What is BitVisor ?
A VMM featuring security functionalities
Has been developed by “Secure VM Project”
A R&D project with governmental support
▪
Initiated by NISC (National Information Security Center)
▪
Funded by SCF of MEXT
▪
SCF: Special Coordination Funds for Promoting Science and Technology
MEXT: Ministry of education, culture, sports, science and technology
developed from scratch (an all-Japanese product)
Several universities and organizations are involved
▪
* VMM: Virtual Machine
2008/11/21 Xen Summit Tokyo 2008 22
Monitor
3. Background & Purpose
Increasing threats of information leakage
From lost or stolen PCs and USB memories
Through the Internet
Via viruses and P2P file-sharing software
▪
Using a VMM to prevent information leakage
Enforce encryption and authentication
Encrypt storages and networks
▪
▪ Authenticate with smart cards
2008/11/21 Xen Summit Tokyo 2008 33
4. Functions of the BitVisor
Storage management Guest OS
Encryption of HDDs
and USB memories VMM
Storage ID Network
management management management
Encryptio Auth & VPN
n Keys
ID management
VMM core
Hardware Virtualization
Key & ID management
Hardware
using smart cards
2008/11/21 Xen Summit Tokyo 2008 44
5. Assumptions behind Design
Decisions
Security of the VMM itself is important
VMM should be kept as small as possible
Used in desktop environments
Windows is the target OS to be secured
Limited development cost & period
3 years, 5 full-time researchers, limited budget
2008/11/21 Xen Summit Tokyo 2008 55
6. Para Pass-through Architecture
Pass-through most I/Os
Guest OS
Guest handles the devices Device Driver
Devices are not virtualized
▪
Para pass-through VMM
Parapass-through driver
Intercept partial I/Os Control I/Os Other I/Os Data I/Os
Pass-through
Access Encryption
Control
Control I/Os are monitored Hardware
Device
for access control
▪
Data I/Os are converted
▪ for encryption
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2008/11/21 Xen Summit Tokyo 2008
7. Advantages
The VMM becomes small
CPU & memory virtualization is simplified
No scheduling and protection among VMs
▪
Drivers are simplified
Need to handle only control I/Os and data I/Os
▪
Overhead becomes lower
Pass-through most I/Os
▪ Even Windows Vista Aero will work
2008/11/21 Xen Summit Tokyo 2008 77
8. Disadvantages
Multiple OSes cannot run simultaneously
The guest OS directly handles the devices
-> Acceptable since the target is desktop computers
Hardware support is limited
A driver is required for each (monitored) device
-> Acceptable in office (government) environments
2008/11/21 Xen Summit Tokyo 2008 88
9. Comparison with other VMMs
Type II VMM
Guest OS Guest OS
VMM
Device Model
TCB = Host OS + VMM
Host OS
Device Driver
Ex. Linux(56M LOC)+QEMU(310K LOC)
▪
hardware
Guest OS Guest OS
VMM
Device Model
Type I VMM
Device Driver
VMM has device model and drivers hardware
Ex. VMWare ESX hypervisor has 200K LOC
▪
* LOC: Lines Of
Code
2008/11/21 Xen Summit Tokyo 2008 99
10. Comparison with Xen (Size)
Xen
Guest
Domain 0
VMM (hypervisor) is relatively small OS
Device
Model
Device Driver
About 100 K LOC [Murray et al. VEE2008]
▪ VMM
hardware
TCB is not necesssarily small
Including Domain 0
▪
BitVisor
VMM is small
▪ VMM core has about 20 K LOC
2008/11/21 Xen Summit Tokyo 2008 1010
11. Comparison with Xen (Overhead)
Xen BitVisor
Need scheduling among Yes No
VMs (support multiple (support only
VMs) single VM)
Need shadow paging Yes Yes
(for address (for protection of
translation and the VMM)
protection among
VMs and the
VMM)
- Shadow paging Optimized Preliminary
implementation (EPT/NPT will help)
Device driver Para- Parapass-through
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15. Summary
A Secure VMM called BitVisor was introduced
Encryption of storages and networks
Authentication and key management using smart
cards
Comparisons with Xen were presented
Difference in the architectures
Para-virtualization v.s. Para-passthrough
▪
Difference in the performances
2008/11/21 Xen Summit Tokyo 2008 1515
16. Current Status
BitVisor 0.7 has been (will be) released
Intel VT, 32/64bit, and SMP/Multicore
Also AMD SVM (single processor only)
▪
Major operating systems are supported
Windows Vista/XP, Linux, FreeBSD, ...
▪
HDD encryption (ATA only)
USB memory encryption (UHCI only)
Type B smart cards
IPsec VPN (Intel PRO100 only)
2008/11/21 Xen Summit Tokyo 2008 1616
17. Download
http://www.securevm.org/
2008/11/21 Xen Summit Tokyo 2008 1717