What are valid S3 key names that can be accessed via the S3 rest API

Question

From the AWS documentation, I know that:

• S3 key names can be any UNICODE name less than1024 characters.
• I have to URL encode the key name in order to access it when using the GET OBJ.

These guidelines, nevertheless, appear overly permissive.

For instance, if I create a key called "../../d," when I try to access it using the GET OBJECT API, I receive a 400 ERROR. Oddly enough, I have no trouble accessing "../d."

Is there a paper that outlines what is and isn't legal?