Domain Name System (DNS)

Setup

This is a setup section for the Domain Name System (DNS) project.

1. Clone repo

  git clone https://github.com/tdadadavid/go-dns.git

2. Install dependencies

	go mod tidy

3. Run command to start the DNS server.

	make run

4. Run command to lookup domain using this DNS resolver.

	nslookup <desired domain> localhost -port=8090

Resource Records

1. Address

This category of records contains the information about the IP address of a domain name. The IP address is used to locate the server that hosts the website or service. It is divide into 2

1. A (IPv4 Address); this is used to store the IPv4 address of a domain name.
2. AAAA (IPv6 Address); this is used to store the IPv6 address of a domain name.

    # get the ipv4 address of google.com
    dig google.com -t A

    # get the ipv6 address of google.com
    dig google.com -t AAAA

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2. CNAME (Canonical Name)

This is used create alias for a domain name. For example if you have domain with example.com, and you also have docs.example.com, drive.example.com, these records still point to the same IP Address (example.com) but with different hostnames.

Host	Type	Value
example.com	A	142.234.53.1
docs.example.com	CNAME	example.com
drive.example.com	CNAME	example.com
mail.example.com	CNAME	example.com

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3. MX (Mail Exchange)

This record is how servers know which mail server to use for a domain name. It is used to specify the mail server that is responsible for accepting email messages for a domain name. For example I (obadafidi@example.com) sends a mail to my friend (tolulope@yahoo.com) the DNS resolution flow will be like this

1. The DNS resolver will first look up the MX record for the domain name example.com.
2. The MX record will specify the mail server that is responsible for accepting email messages for the domain name example.com.
3. The DNS resolver will then look up the IP address of the mail server using the A record (IPv4)
4. The mail server will then accept the email message and deliver it to the recipient email server (yahoo.com)
5. Then the mail server on yahoo.com will authenticate the email message to ensure it is from a trusted source.
6. The mail server on yahoo.com will then deliver the email message to the recipient's email once verification is complete.

sequenceDiagram
    participant Obadafidi as Obadafidi@example.com
    participant GMail as GMail Mail Server
    participant DNS as DNS Server
    participant Yahoo as Yahoo Mail Server
    participant Tolulope as tolulope@yahoo.com

    Note over Bob,GMail: MX Record Resolution & Mail Delivery Process

    Bob->>GMail: (1) Sends email to tolulope@yahoo.com
    GMail->>DNS: (2) Requests MX record for yahoo.com
    DNS-->>GMail: (3) Returns MX record (Yahoo Mail Server details)
    GMail->>DNS: (3b) Resolves A record to get IP address of Yahoo Mail Server
    GMail->>Yahoo: (4) Sends mail data to Yahoo Mail Server
    Yahoo->>DNS: (5) Verifies that sending mail server (GMail) is authenticated
    DNS-->>Yahoo: Returns authentication confirmation (SPF/DKIM/DMARC)
    Yahoo->>Tolulope: (6) Delivers email to tolulope@yahoo.com

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Results

1. Lookup real domains

The server responds with the domain name and IP for address for amazon.com

Same thing happens for google.com

2. Lookup fake domains

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Future Improvements

• [] Write DSN parser
• [] Implement TLS/SSL support
• [] Add support for other DNS record types (TXT, CNAME, etc.)