maximizing performance with spdy and ssl
DESCRIPTION
Billy Hoffman from Zoompf shows how to improve the performance of your website using SPDY and SSLTRANSCRIPT
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What is SPDY?
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Massive Browser Support
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Massive Server Support
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Cast of Characters
• TCP• HTTP• SSL• X.509 Certificate• Cryptography (asymmetric & symmetric) • SPDY
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HTTP/HTTPS
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HTTP/SPDY/SSL Sandwich
• SPDY encapsulates HTTP requests– Single Multiplexed stream
• Transmits contents over SSL channel
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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
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SETTING THE STAGE FOR SPDY
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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
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Listener on 443 is speaking SSL?
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Creating a Valid SSL connection
• Agreement on crypto algorithms
• X.509 certificate is valid
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X.509 Cert: Correct Domain?
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X.509 Cert: Valid Time Period?
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X.509 Cert: Is it Trusted?
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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• Has it been revoked?– CRL lists– Online Certificate Status Protocol (OCSP)
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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
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SSL Handshake
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
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Announcing SPDY support in the SSL Handshake
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
+ Ext:13172/AL
PN
+ NPN/ALPN
+ Ext:13172/ALPN
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ClientHello with Extension 13172
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ServerHello with NPN
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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
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OPTIMIZING SSL/SPDY
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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
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The SSL Handshake is Costly!
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
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Resume SSL Session
• Avoid regenerating keys• Avoid unneeded trips• 2 methods
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
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• Both sides keep state/cache• Reuse based on id• Widely supported
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
sessionid: 3a8a…
Big cache of all ids given
out, and associated
keys/ciphers
Session Identifiers
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• Client stores “Magic Ticket”• RFC 5077, optional• No IIS support
Microsoft Technet: Host TLS/SSL Workshttp://bit.ly/16Zx0en
Encrypted summary of keys/ciphers, signed by
server
Verifies summary is valid, uses
values
Session Tickets
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SSL False Start
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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!
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Minimize the Certificate Chain
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OCSP Validation causes delays
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OCSP Stapling
• Good in theory, bad in practice• Browsers are moving away from OSCP
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Oversized Asymmetric Keys
• 1024 is fine• 2048 for banks• Anything more is
overkill
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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
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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
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“Does this really matter?”
• Seriously?• 1024 more bytes in key?• 2 more kilobytes in the X.509 cert?• Accidently using AES-256?• Really?
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“Does this really matter?”
OMG WTF MS?
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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)
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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
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TOOLS
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SSL Labs
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SPDYCheck.org
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Now on Github, GPL licensed!
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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)
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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
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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)
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Free Performance Assessmentzoompf.com/free