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The product security team is responsible for ensuring the security of all code Twitter ships. This means proactively finding and fixing vulnerabilities using automation, working closely with engineering teams throughout the company to design and implement secure systems, and building security features into the product. To make all this happen and execute at a fast pace, we practice an agile process and build tools to support rapid information transfer. First, we'll talk about our approach to using automation to ensure that we ship secure code by getting the right information to the right people at the right time. We will also discuss our security review process, which is focused on improving the pace of development and cooperative problem solving. Finally, we'll talk about how we develop security features for Twitter, including our recent improvements to login verification. At Twitter, our goal is to reach every person on the planet. Having a global reach means understanding and responding to many threats. We want to share the details of our team's organization and process that allows us to keep Twitter secure as we continue to rapidly scale.
Citation preview
Defending the Bird
Product Security Engineering at Twitter
Alex Smolen (@alsmola)
Justin Collins (@presidentbeef)
YAC, Moscow, 2013
What does it mean to “Defend the Bird”?
500+ million Tweets a day
Hyper-growth
2000+ employees around the world
200+ million daily active users
Twitter as the global town square.
3 floors~700 employees
1 floor~100 employees
5+ floors~2000+ employees
https://twitter.com
https://mobile.twitter.com
https://twitter.com
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We are 1 out of 100 engineers.
We can’t do everything.
Automation
Code review
Security features
Automating Security
Avoid tedious tasks
Catch issues early
Notify right people
We need a central location where information is collected and transferred.
Static analysisDynamic analysisInternal metrics
How do we let developers know when they check in bad code?
Brakeman
Static analysis for Rails
Needs infrastructure for integration
Reports to SADB
Coffee Break
Javascript static analysis
Catch DOM-based XSS
Reports to SADB
Phantom Gang
Dynamic HTTP scanning
Specific, not full scan
Reports to SADB
We manually review what slips through the cracks.
Code Reviews
Code goes through a review system
Security is automatically added to sensitive reviews
Security can be manually added to any review
Accountability
Email when there are new reviews
Dashboard of pending reviews
Once a month clean sweep
Teams request security reviews through a self-service form.
Security features
Two-factor authentication
Something we’ve wanted to build for a long time
Designed and implemented by the product security team
How do you build a robust yet simple solution?
SMS-based two-factor
Send a six digit code the user
Requires a temporary password to sign in to other apps and devices
Native two-factor
Client has a private/public keypair
Signs request sent by server over push, which has public key
One-tap sign in
Two-factor challenges
Happy case is easy, sad case is hard
Doesn’t deal with many-to-many account access
People can’t manage their own keys
Twitter was one of the first major
services to require 100% SSL.
HTTP Strict Transport Security
How do you bootstrap?
Tells browser not to use HTTP
Sub-domains, CDNs, mobile
Certificate pinning
Implemented in mobile apps, Chrome
Only one certificate is valid
Also working on TACK
ECDHE
SSL mode with perfect forward secrecy
Ephemeral keys used for conversations
We need to build security in to our custom frameworks.
Security headers
Adds several default security headers
Implements interoperable CSP
https://github.com/twitter/secureheaders
Keybird
Keys delivered securely to production environment
Uses puppet
The bird is big, and we’re small.
We use tools to accomplish more.
![[James J. Smolen] Cased Hole and Production Log Ev(Bookos.org)](https://img.pdfslide.us/doc/110x75/55cf9984550346d0339dc624/james-j-smolen-cased-hole-and-production-log-evbookosorg.jpg)
