NAMESERVER08: Testing QNAME case insensitivity

Test case identifier

NAMESERVER08 Verify whether the authoritative nameserver response match the case of every letter in the query name

Objective

The DNS standards require that nameservers treat names with case insensitivity. That is, the names example.com and EXAMPLE.COM should resolve to the same IP address. However, in the response, most nameservers echo back the name as it appeared in the request, preserving the original case.

Therefore, another way to add entropy to requests is to randomly vary the case of letters in domain names queried. This technique, also known as "0x20" because bit 0x20 is used to set the case of of US-ASCII letters, was first proposed in the IETF internet draft Use of Bit 0x20 in DNS Labels to Improve Transaction Identity. With this technique, the nameserver response must match not only the query name, but the case of every letter in the name string; for example, wWw.eXaMpLe.CoM or WwW.ExamPLe.COm. This may add little or no entropy to queries for the top-level and root domains, but it's effective for most hostnames.

Inputs

The domain name to be tested.

Ordered description of steps to be taken to execute the test case

1. Retrieve all address records for all the name servers using Method 4 and Method 5.
2. A random query with mixed case (e.G Www.iETf.Org) is sent to each unique name server IP address found in step 1.
3. Remember the case of the QNAME in the query sent.
4. Compare the QNAME in the question section of the response with the string in step3.
5. If the string in step3 and step4 are not equal with respect to case in sensitivity, the test fails.

Outcome(s)

The test case is Ok only if there are no responses in the authority section

Special procedural requirements

None.

Intercase dependencies

None.