DnChain - DNAME Alias Chains

DnChain - DNAME Alias Chains

This module implements incremental alias chains using DNAME (Delegation Name) records. It returns an alias record with an incremented domain name index, forming a chain that continues to increment indefinitely.

Specifically, this module generates a DNAME alias record in the format dnchain###.yourdomain.com, where ### represents the incremented index.

The concept is that if the client/resolver attempts to resolve this alias further, it will generate yet another incremented alias, causing the process to continue indefinitely and potentially keeping the resolver occupied.

However, in practice, most modern resolvers detect such chains and terminate the resolution after encountering a certain number of consecutive aliases (e.g., 20 aliases) or upon reaching a specified time limit for the resolution (e.g., 30 seconds).

Note that this feature provides the same functionality as requesting a DNAME record for the generic chain feature.

⚠BEWARE⚠This could potentially lead to a domain lock-up (DoS).

Category: Alias chains

Tags: Domain Lock-Up, Denial of Service

RFCs: RFC2672, RFC6672

Format 

dnchain<NUMBER>.yourdomain.com

Where:

  • The <NUMBER> parameter specifies an arbitrary number that will be incremented in the response.

Examples

By default, the module generates a DNAME alias with the index of 1:

# dig dnchain.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> dnchain.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40077
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dnchain.yourdomain.com.		IN	A

;; ANSWER SECTION:
dnchain.yourdomain.com.	60	IN	DNAME	dnchain1.yourdomain.com.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Fri Nov 08 23:23:46 +04 2024
;; MSG SIZE  rcvd: 77

Download PCAP File


If we attempt to resolve the resulting domain name (dnchain1.yourdomain.com), we receive an incremented alias record:

# dig dnchain1.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> dnchain1.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10784
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dnchain1.yourdomain.com.	IN	A

;; ANSWER SECTION:
dnchain1.yourdomain.com. 60	IN	DNAME	dnchain2.yourdomain.com.

;; Query time: 4 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Fri Nov 08 23:23:48 +04 2024
;; MSG SIZE  rcvd: 78

Download PCAP File


If we continue to resolve the next domain name (dnchain2.yourdomain.com), we again receive an incremented alias record:

# dig dnchain2.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> dnchain2.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 65235
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dnchain2.yourdomain.com.	IN	A

;; ANSWER SECTION:
dnchain2.yourdomain.com. 60	IN	DNAME	dnchain3.yourdomain.com.

;; Query time: 4 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Fri Nov 08 23:23:49 +04 2024
;; MSG SIZE  rcvd: 78

Download PCAP File


This resolution process can continue indefinitely, as there are no limits on the size of the index number. Each resolution yields another incremented alias record:

# dig dnchain9999999999999999999999999.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> dnchain9999999999999999999999999.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5030
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dnchain9999999999999999999999999.yourdomain.com. IN A

;; ANSWER SECTION:
dnchain9999999999999999999999999.yourdomain.com. 60 IN DNAME dnchain10000000000000000000000000.yourdomain.com.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Fri Nov 08 23:23:50 +04 2024
;; MSG SIZE  rcvd: 127

Download PCAP File

The domain name will never be fully resolved as the incremental process continues indefinitely.


From the same category

See also


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