1. SFS-HTTP: Securing the Web with Self-Certifying URLs
Eric Banks & Michael Kaminsky
Topics in Networking
2 December 1999

2. Current State of Web SecurityCA
Connection request
Client
Server
Certificate
Encrypted connection

3. Goal: Extensible Host Authentication
Client
Server
Public
keys

4. Self-certifying Pathnames and URLs
/sfs/host:HostID/path
(SFS)
(SFS-HTTP)
Example:

5. Overall Picture Client Client Server Server Daemon Daemon (Browser)
Encrypted
Daemon
Daemon
(Browser)
(e.g.. Apache)
Network
Connection
User
Agent

6. Communicate via Sun RPC over an encrypted transport
Client
Server
Encrypted
Daemon
Daemon
Network
Connection
Communicate via Sun RPC over an encrypted transport
RPC transport uses:
arc4 stream cipher for encryption
SHA1-based MAC for integrity
Server sends copy of its public key to the client
Client verifies public key with HostID

7. Both processes are on same machine
Server
Server
Daemon
(e.g.. Apache)
Both processes are on same machine
Server daemon makes requests to local web server
Works asynchronously (multiple requests sent in parallel)

8. Client
Client
Daemon
(Browser)
Both processes are on same machine
Client daemon acts as a web proxy
Client daemon parses request and checks for HostID
HostID given: establish encrypted connection
No HostID: ask User Agent for HostID
HostID returned: establish encrypted connection
No HostID: unencrypted connection

9. Server Authentication #1: Direct Authentication
Client
Client
“GET
Daemon

10. Server Authentication #2: Agent Authentication
Client
Client
“GET
Daemon
host?
HostID
User
Agent

11. No Authentication: Unencrypted Connection
Client
Client
“GET
Direct connection
Daemon
to web server
host?
???
User
Agent

12. User Authentication
None
Password (over an encrypted connection)

13. Contributions It Works! Can be done….
Don’t need to modify existing software
Arbitrary user-defined security model for the Web
Persistent connections

14. Performance
Normal:
SFS-HTTP Unencrypted:
SFS-HTTP Encrypted:

15. Future Work One proxy per machine
Automatically add HostIDs to User Agent
Scalability (public key crypto is expensive)
Access control in server daemon