maximizing performance with spdy & ssl - maximizing...spdy optimization • spdy only works over...
TRANSCRIPT
What is SPDY?
Massive Browser Support
Massive Server Support
Cast of Characters
• TCP • HTTP • SSL • X.509 Certificate • Cryptography (asymmetric & symmetric) • SPDY
HTTP/HTTPS
HTTP/SPDY/SSL Sandwich
• SPDY encapsulates HTTP requests – Single Multiplexed stream
• Transmits contents over SSL channel
Today’s Focus
• Setting the Stage for SPDY – Can speak SSL with a server – Can create a valid SSL connection – Client and Server agree to use SPDY
• Optimizing SPDY – Optimizing SSL – Optimizing SPDY – Avoiding optimizations that hurt SPDY
• Tools to help
SETTING THE STAGE FOR SPDY
SSL Connectivity
• Hostname resolves • IP is reachable • Web server is listening on SSL port • Web server understands SSL • Web server knows which site you want
– Shared Hosting and SNI
Listener on 443 is speaking SSL?
Creating a Valid SSL connection
• Agreement on crypto algorithms
• X.509 certificate is valid
X.509 Cert: Correct Domain?
X.509 Cert: Valid Time Period?
X.509 Cert: Is it Trusted?
X.509 Cert: Is it Trusted?
• Do I trust the issuer? – If not, was it signed by someone I trust?
• Has it been revoked? – CRL lists – Online Certificate Status Protocol (OCSP)
Agreeing to Use SPDY
• Client tells server it supports SPDY • Server tells client it supports SPDY • Client sends SPDY over SSL • Else, falls back to HTTP over SSL
SSL Handshake
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
Announcing SPDY support in the SSL Handshake
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
+ Ext:13172/ALPN
+ NPN/ALPN
+ Ext:13172/ALPN
ClientHello with Extension 13172
ServerHello with NPN
Review: Speaking SPDY
• Client resolves and connects to SSL port • Client announces SPDY support inside
ClientHello • Server announces SPDY support in
ServerHello • Client validates X.509 cert, finalized SSL
connection • SPDY conversation happens
OPTIMIZING SSL/SPDY
The SSL Tarpits
• SSL handshake requires 2 round trips • Certificates can be large • Certificates need to be validated • Keys can be too large • Algorithms can be slow
The SSL Handshake is Costly!
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
Resume SSL Session
• Avoid regenerating keys • Avoid unneeded trips • 2 methods
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
• Both sides keep state/cache • Reuse based on id • Widely supported
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
sessionid: 3a8a…
Big cache of all ids given
out, and associated
keys/ciphers
Session Identifiers
• Client stores “Magic Ticket” • RFC 5077, optional • No IIS support
Microsoft Technet: Host TLS/SSL Works http://bit.ly/16Zx0en
Encrypted summary of keys/ciphers, signed by
server
Verifies summary is valid, uses
values
Session Tickets
SSL False Start
False Start: Not Gone
• “The Failure of False Start” • Chrome still does it!
– Desktop and mobile
• Any server that supports NPN! (with forward secure) – Any server with SPDY support… – Or SSL + NPN, but only announces HTTP/1.1!
Minimize the Certificate Chain
OCSP Validation causes delays
OCSP Stapling
• Good in theory, bad in practice • Browsers are moving away from OSCP
Oversized Asymmetric Keys
• 1024 is fine • 2048 for banks • Anything more is
overkill
Cipher Order/Choice Matters
• RC4 is the best • Unless on a
machine with AES-NI – Intel i7, Xeons,
some AMD – Not most virtual
machines!!!
• First match wins
http://zombe.es/post/4078724716
Is SSL really helping you?
• SSL doesn’t “secure” your website – Prevents eavesdropping, tampering – Not XSS, CSRF, SQL Injection, Unpatched/out-
of-date software, RCE, LFI, etc.
• Consider: NULL-MD5, NULL-SHA • SSL with no encryption
“Does this really matter?”
• Seriously? • 1024 more bytes in key? • 2 more kilobytes in the X.509 cert? • Accidently using AES-256? • Really?
“Does this really matter?”
SPDY Optimization
• SPDY only works over SSL • Ensure that all your traffic if over SSL • HTTP 301 direct for http: to https:
– Add a cache-control header!
• HTTP Strict Transport Security (HSTS) – Like the browser’s cache, but for protocol
access. Make (semi) far future – Wide support (>90% of SPDY capable
browsers)
Avoid These Optimizations
• Domain Sharding – Hack to request multiplexing, not needed – Hurts SPDY by spreading requests out
• JavaScript CDNs – These are a horrible blight on the web! – http://statichtml.com/2011/google-ajax-
libraries-caching.html – https://github.com/h5bp/html5-boilerplate/
pull/1327
TOOLS
SSL Labs
SPDYCheck.org
Now on Github, GPL licensed!
SSL/SPDY Optimization Check List
• Website responds over SSL/443 • Website has NPN extension (even without
SPDY for False Start) • X.509 certificate is valid • X.509 chain is short • SSL Asymmetric keys are <= 2048 • Cipher is RC4 (or AES-128 if supports
dedicated instructions)
SSL/SPDY Optimization Check List
• SSL session resumption is enabled (both identifiers and tickets)
• No SSL compression • Website is using latest version of SPDY • HTTP permanently (301) redirects to
HTTPS (including cache header) • HTTPS sends HTTP Strict Transport
Security header
Great Resources
• Ivan Ristic (blog.ivanristic.com) • Adam Langley (www.imperialviolet.org) • Mark Nottingham (www.mnot.net/blog/)
• Qualys SSL Labs (ssllabs.com) • SPDYCheck (spdycheck.org)
Free Performance Assessment zoompf.com/free
