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When Good Services Go Wild: Reassembling
Web Services for Unintended Purposes
Feng Lu, Jiaqi Zhang, Stefan Savage
UC San Diego
The Web Mashup Ecosystem
2
Characteristics of “Mashup” Model
 Combines data or
functionality from more than
one source
 Produces results beyond
original service model
 Re-usability and agility at the
expense of encapsulation or
clean semantics guarantee
 Security risks: XSS, CSRF, etc.
Existing efforts focus on violations of client’s browser security policy
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New Class of Security Concerns
 Users abuse web services
 Reassemble web services for
unintended purposes at the
expense of reputation of
service providers
 Exploit combination of web
services to create new
capabilities
 Examples:
 DoS attack
 IP address laundering
CloudProxy built from unrelated web pieces as a proof of concept
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Design Overview
 CloudProxy: a functional web proxy leveraging existing
web service APIs
 Implemented most used HTTP methods: GET/POST
 Design approaches:
 Focus on public APIs that allow web content retrieval
 Re-write request to fit API requirement if necessary
 Assemble response to provide transparent web access
mashup
Cloud
Proxy
Web
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The Process of Downloading a Webpage
1. URL http://sysnet.ucsd.edu
4.get http://sysnet.ucsd.edu http/1.0
5.http 302 redirect: http://sysnet.ucsd.edu/sysnet
6.get http://sysnet.ucsd.edu/sysnet http/1.0
2. ip for
sysnet.ucsd.e
du
3. 137.110.222.10
Web Server
7.HTTP/1.0 OK index.html
8. get images, javascripts, css, and etc
DNS Server
9. return images, javascripts, css, and etc
Index.html
…
<img
src=“photos/ba
nner.jpg”>
…
Image URL: http://<absolute path> +<relative path>
sysnet.ucsd.edu/sysnet/ photos/banner.jpg
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HTTP GET
 Google spreadsheet API
 ImportData(“www.ucsd.edu”)
 Only works for ASCII content
 Google content server API (non-ASCII content)
 http://images-docsopensocial.googleusercontent.com/gadgets/proxy?url=xxxx&co
ntainter=###
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HTTP Redirection
 Facebook developer debug info API
 http://developers.facebook.com/tools/debug/og/objects?q=url
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HTTP POST
 Google gadget caching API
 http://www.gmodules.com/ig/proxy?url=xxx
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Summary of Attacking Vectors
 Facebook developer debug info API
 http://developers.facebook.com/tools/debug/og/objects?q=url
 Google spreadsheet API
 =ImportData(“url”)
 Google content server API
 http://image2focus.opensocial.googleusercontent.com/gadgets/proxy/url?=x
xx&container=###
 Google gadget caching API
 http://www.gmodules.com/ig/proxy?url=xxx
 URL shortener API
 http://www.googleapis.com/urlshortener/v1/url?key=“api_key
”
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Overall Architecture Design
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Evaluation
Web Tasks Performed
HTTP Post
IP Hiding
Video Viewing
HTTP Redirect
Spreadsheet Demo
Bing Search
All host machines are owned by either Facebook or Google!
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Security Implications
 Web content provider:
 Bypassing IP based content restriction
 End users:
 Anonymous web access
 Black hats:
 Aiding DoS attack
 Web service provider:
 Wasting storage and network resources
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Summary
 Unrelated web services can be easily combined to create
new undesired services  abuse Web services
 Demonstrated a functional Web proxy based on public
web services
 Object size <= 10MB
 Does not support cookie
 Potential security risks
 Lack or difficulty of security policy enforcement of web
services
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Thank you!
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API Friendly URL
 URL shortener API
 http://www.googleapis.com/urlshortener/v1/url?key=“api_key”
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Example of IP based Content Restriction
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