Use of Non-Canonical URL Paths for Authorization Decisions

The product defines policy namespaces and makes authorization decisions based on the assumption that a URL is canonical. This can allow a non-canonical URL to bypass the authorization.

If an application defines policy namespaces and makes authorization decisions based on the URL, but it does not require or convert to a canonical URL before making the authorization decision, then it opens the application to attack. For example, if the application only wants to allow access to http://www.example.com/mypage, then the attacker might be able to bypass this restriction using equivalent URLs such as:

Therefore it is important to specify access control policy that is based on the path information in some canonical form with all alternate encodings rejected (which can be accomplished by a default deny rule).

• http://WWW.EXAMPLE.COM/mypage
• http://www.example.com/%6Dypage (alternate encoding)
• http://192.168.1.1/mypage (IP address)
• http://www.example.com/mypage/ (trailing /)
• http://www.example.com:80/mypage