Web Security

We learned the danger of trusting or making assumptions about user’s input to web applications.

Identifying vulnerable code

• Server Side Request Forgery to XML External Entity Injection

  The following excerpt has been obtained from a vulnerable version of Microsoft Exchange OnPrem and is related to CVE-2020-17143 with credits to Steven Seely of Qihoo360

  

  Can you spot the bug(s)? An attacker can control the endPointUrl parameter to OneDriveProUtilities.GetWacUrl

Vulnerabilities in your code

You have probably implemented some web applications. Using your own experience building an application, discuss with your peers and brainstorm about:

• What functionalities required user input and how those functionalities could be safely implemented.

  Consider:

  • Whitelist/Blacklist
  • Sanitization

• What trust boundaries existed within the application and how user input could be safely transferred across boundaries

  Consider:

  • How can input be validated at any of the following boundaries (if they existed)
    • Client / Web server boundaries
    • Web server / OS boundaries
    • Web server / Database boundaries