Why do we need cookies to maintain state across multiple HTTP requests?
HTTP is a stateless protocol, which means each request has no knowledge of any other requests.
Viewing Cookies
What stateful information might the cookies on cnn.com be storing in cookies?
Some possible answers: time zone, personal settings (such as dark mode), tracking data for advertising.
For example, if you change the website to dark mode and load an article, the cookie that gets sent to the server will tell the server to load the article in dark mode.
Cookie Scopes
Why do we need to define domain and path scopes for each cookie, instead of sending every cookie in the browser on every request?
Some cookies may have sensitive data that shouldn’t be sent to all websites.
Setting Cookie Scope
Why might we want to let mail.google.com set a cookie for google.com?
There may be many shared services under one domain, like maps.google.com, mail.google.com, etc. The policy for setting cookies allows any one of these services to set a cookie for all Google services.
This could have security vulnerabilities if different subdomains are run by different organizations, such as eecs.berkeley.edu and math.berkeley.edu.
Scope for Sending Cookies
If Cookie 1’s path was changed to /user, which of the three domains would it be sent to?
None. All three domains have path /, and /user is not a prefix of /.
Examples of Setting and Sending Cookies
Modifying Cookies in Browser
See Q3.5-Q3.9 on Homework 6 for some practice on viewing and modifying cookies in your browser.
Cookie Policy vs. Same-Origin Policy
Bypassing Same-Origin Policy with Cookies
What difference between the same-origin policy and cookie policy causes this vulnerability?
(Fill in the blanks: Same-origin policy thinks that financial.example.com and blog.example.com are controlled by ___ (the same/different) organization(s) because ___, but cookie policy thinks they are controlled by ___ (the same/different) organization(s) because ___.)
Same-origin policy thinks that financial.example.com and blog.example.com are controlled by different organizations because their domains are different, but cookie policy thinks they are controlled by the same organization because both can set a cookie for example.com.
Session Management with HTTP Auth
Session Token Analogy
Session Tokens
Storing Session Tokens
When could a man-in-the-middle attacker on the network steal a user’s session token?
All three options for storing a session token are at the application layer, so the MITM attacker just needs to be able to see the application layer payload to steal the session token.
If the request is sent over HTTP, the MITM attacker can always steal the session token. If the request is sent over HTTPS, the MITM attacker can’t steal the session token.
CS 161 Summer 2020