![Page 1: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/1.jpg)
1
Protection and Communication Abstractions for Web Browsers
in MashupOS
Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR)Collin Jackson (Stanford)
February, 2008
![Page 2: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/2.jpg)
2
![Page 3: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/3.jpg)
3
… but most of all, Samy is my hero
![Page 4: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/4.jpg)
4
![Page 5: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/5.jpg)
5
Outline
• The problem• The MashupOS project• Protection• Communication• Implementation and demo• Evaluation• Related work• Conclusions
![Page 6: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/6.jpg)
6
Client Mashups• Web content has evolved from single-principal services
to multi-principal services, rivaling that of desktop PCs.• Principal is domain
![Page 7: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/7.jpg)
7
Browsers Remain Single-Principal Systems
• The Same Origin Policy (SOP), an all-or-nothing trust model:– No cross-domain interactions allowed– (External) scripts run with the privilege of the
enclosing page
http://integrator.com/
<iframe src=“http://provider.com/p.html”></iframe>
http://integrator.com/
<scriptsrc=“http://provider.com/p.js”></script>
X
![Page 8: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/8.jpg)
8
Insufficiency of the SOP
• Sacrifice security for functionality when including an external script without fully trusting it
• E.g., iGoogle, Live gadget aggregators’ inline gadget
![Page 9: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/9.jpg)
9
Insufficiency of the SOP, Cont.• Third-party content
sanitization is hard– Cross site scripting
(XSS): • Unchecked user input in
a generated page • E.g., Samy worm:
infected 1 million MySpace.com users in 20 hours
• Root cause:– The injected scripts run
with the page’s privilege
Samy is my hero
![Page 10: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/10.jpg)
10
Insufficiency of the SOP, Cont.
• Sacrifice functionality for security when denying scripts in third-party content
• E.g., MySpace.com disallows scripts in user profiles
![Page 11: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/11.jpg)
11
The MashupOS Project• Enable browser to be a multi-principal OS• Focus of this paper: protection and
communication abstractions• Protection:
– Provide default isolation boundaries
• Communications: – Allow service-specific, fine-grained access control
across isolation boundaries
![Page 12: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/12.jpg)
12
Design Principles• Match all common trust levels to balance
ease-of-use and security– Goal: enable programmers to build robust
services– Non-goal: make it impossible for programmers
to shoot themselves in the foot • Easy adoption and no unintended
behaviors
![Page 13: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/13.jpg)
13
Outline
The problemThe MashupOS project• Protection• Communication• Implementation and demo• Evaluation• Related work• Conclusions
![Page 14: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/14.jpg)
14
A Principal’s Resources
• Memory: – heap of script objects including DOM objects
that control the display• Persistent state:
– cookies, etc.• Remote data access:
– XMLHttpRequest
![Page 15: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/15.jpg)
15
Trust Relationship between Providers and Integrators
i.com
i.com
ContentSemantics
Abstraction Run-as
p.com i.com
Internet
http://i.com/
HTML
XHR
X
XXHR
No No Isolated <Frame> p.com
<iframe src=“http://p.com/c.html”></iframe>
X
![Page 16: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/16.jpg)
16
Trust Relationship between Providers and Integrators
i.com
i.com
ContentSemantics
Abstraction Run-as
p.com i.com
Internet
http://i.com/
Script
XHR
No No Isolated <Frame> p.com
Yes Yes Open <Script> i.com
<script src=“http://p.com/c.js”></script>
![Page 17: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/17.jpg)
17
Trust Relationship between Providers and Integrators
i.com
i.com
ContentSemantics
Abstraction Run-as
p.com i.com
Internet
http://i.com/
No No Isolated <Frame> p.com
Yes Yes Open <Script> i.com
No Yes
X
![Page 18: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/18.jpg)
Trust Relationship between Providers and Integrators
18
p.com i.com
Internet
http://i.com/
X
XXHR
NoneYes No <Sandbox><OpenSandbox>
Unauthorized
Unauth
XXHR
i.com
i.com
ContentSemantics
Abstraction Run-as
No No Isolated <Frame> p.com
Yes Yes Open <Script> i.com
No Yes
Unauthorized content is not authorized to access any principal’s resources.
<sandboxsrc=“http://p.com/c.html”></sandbox>
![Page 19: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/19.jpg)
19
Properties of Sandbox• Asymmetric access
– Access: reading/writing script global objects, function invocations, modifying/creating DOM elements inside the sandbox
• Invoking a sandbox’s function is done in the context of the sandbox– setuid (“unauthorized”) before invocation and setuid
(“enclosingPagePrincipal) upon exit
• The enclosing page cannot pass non-sandbox object references into the sandbox.– Programmers can put needed objects inside the sandbox
• Private vs. Open sandboxes
![Page 20: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/20.jpg)
20
Private Sandbox<sandbox src=“file”>
Content if tag not supported</sandbox>
• Belongs to a domain and can only be accessed by that domain– E.g., private location history marked on a map
• Private sandboxes cannot access one another even when nested– Otherwise, a malicious script can nest another
private sandbox and access its private content
![Page 21: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/21.jpg)
21
Open Sandbox
<OpenSandbox src=“file”>Content if tag not supported
</OpenSandbox>• Can be accessed by any domain• Can access its descendant open
sandboxes --- important for third party service composition– E.g., e-mail containing a map; don’t want an
e-mail to tamper hotmail.com; don’t want the map library to tamper the e-mail
![Page 22: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/22.jpg)
22
Provider-Browser Protocol for Unauthorized Content
• Unauthorized content must be sandboxed and must not be renderable by frames– Otherwise, unauthorized content would run as the principal of the frame
• MIME protocol seems to be what we want: – Require providers to prefix unauthorized content subtype with
x-privateUnauthorized+ or x-openUnauthorized+– E.g., text/html text/x-privateUnauthorized+html– Verified that Firefox cannot render these content types with <frame>
and <script>– But, IE’s MIME sniffing allows rendering sometimes
• Alternative: encraption (e.g., Base64 encoding)• Prevent providers from unintentionally publishing unauthorized
content as other types of content: – Constrain sandbox to take only unauthorized content
![Page 23: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/23.jpg)
23
Key Benefits of Sandbox
• Safe mashups with ease• Beneficial to host third-party content as
unauthorized content
![Page 24: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/24.jpg)
24
Sandbox for Safe Mashups with Ease
http://Mashup.com/index.htm
<script src=“a.com/a.js”> </script>
<script src=“b.com/b.js”> </script>
<script>// local script to Mashup.com // calling functions in a.js and b.js</script>
<div id=“displayAreaForA”> … </div>
X
X
![Page 25: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/25.jpg)
25
Hosting Third-Party Content as Unauthorized Content
• Combats cross site scripting attacks in a fundamental way– Put user input into a sandbox– Does not have to sacrifice functionality
• Helps with Web spam– Discount the score of hyperlinks in third party
content
![Page 26: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/26.jpg)
26
Outline
The problemThe MashupOS projectProtection• Communication• Implementation & demo• Evaluation• Related work• Conclusions
![Page 27: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/27.jpg)
27
Communications
• Message passing across the isolation boundaries enable custom, fine-grained access control
Isolated Isolated
a.com b.com
CommRequest
Unauthorized
Com
mR
eque
st
![Page 28: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/28.jpg)
28
CommRequest• Server:
server = new CommServer();server.listenTo(“aPort”,
requestHandlerFunction);• Client:
req = new CommRequest();req.open (“INVOKE”,
“local:http://bob.com//aPort”, isSynchronous);
req.send (requestData);req.onreadystatechange = function ()
{ …}
![Page 29: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/29.jpg)
29
CommRequest vs. XMLHttpRequest
• Cross domain• Source labeled• No cookies sent• “Server” can be on client• Reply from remote server tagged with
special MIME type• Syntax similar to socket API and XHR
![Page 30: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/30.jpg)
30
Outline
The problemThe MashupOS projectProtectionCommunication• Implementation & demo• Evaluation• Related work• Conclusions
![Page 31: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/31.jpg)
31
Implementation
• Use frames as our building blocks, but we apply our access control
ScriptEngine
MashupOSScript Engine
Proxy
MashupOSMIMEFilter
Script executionDOM object access
DOM object update
Original HTML
MashupOS transformed HTML
HTML Layout Engine
![Page 32: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/32.jpg)
32
Evaluation: Showcase Application
• PhotoLoc, a photo location service– Mash up Google’s map service and Flickr’s
geo-tagged photo gallery service– Map out the locations of photographs taken
• PhotoLoc doesn’t trust flickr nor gmap
![Page 33: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/33.jpg)
33
PhotoLoc/index.htm<script>
function setPhotoLoc(request) { var coordinate = request.body; var latitude = getLatitude (coordinate); var longitude = getLongitude (coordinate); G.map.setCenter(new GLatLng(latitude, longitude), 6);}var svr = new CommServer();svr.listenTo(“recvLocationPort”, setPhotoLoc);
</script>
<Sandbox src=”f.uhtml” id=F> </Sandbox>
<Sandbox src=”g.uhtml” id=G> </Sandbox>
Direct access
CommRequest
![Page 34: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/34.jpg)
34
Demo
![Page 35: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/35.jpg)
35
Evaluation:Prototype Performance
• Microbenchmarking for script engine proxy– Negligible overhead for no or moderate DOM
manipulations– 33%--82% overhead with heavy DOM manipulations
• Macrobenchmark measures overall page-loading time using top 500 pages from the top click-through search results of MSN search from 2005– shows no impact
• Anticipate in-browser implementation to have low overhead
![Page 36: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/36.jpg)
36
Outline
The problemThe MashupOS projectProtectionCommunicationImplementation & demoEvaluation• Related work• Conclusions
![Page 37: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/37.jpg)
37
Related work• Crockford’s <Module>
– Symmetric isolation with socket-like communication with the enclosing page
• Wahbe et al’s Software Fault Isolation– Asymmetric access though never leveraged– Primary goal was to avoid context switches for
untrusted code in a process
• Cox et al’s Tahoma browser operating system uses VM to– Protect the host system from browser and web
services– Protect web applications (a set of web sites) from one
another
![Page 38: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/38.jpg)
38
Future Work
• Robust implementation of the protection model
• Tools to detect whether a browser extension violates the browser’s protection model
• Tools for ensuring proper segregation of different content types
• Resource management, OS facilities
![Page 39: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/39.jpg)
39
Conclusions
• Web content involves multiple principals• Browsers remain a single principal platform• The missing protection abstraction: Unauthorized
content and <sandbox>– Enable safe mashups with ease– Combats cross-site scripting in a fundamental way
• CommRequest allows fine-grained access control across isolation boundaries
• Practical for deployment
![Page 40: Protection and Communication Abstractions for Web Browsers in MashupOS Helen J. Wang, Xiaofeng Fan, Jon Howell (MSR) Collin Jackson (Stanford) February,](https://reader036.vdocuments.mx/reader036/viewer/2022062421/56649d435503460f94a1fceb/html5/thumbnails/40.jpg)
40
Thank you!