Postal DNS

Lightweight API driven Authoritative DNS server. Extracted from Project Pending.

Features

• All records can be edited over REST API
• All changes are effective immediatelly (or as long as it takes Redis to distribute changes from master to replica instances)
• All basic record types (A, AAAA, CNAME, TXT, MX, CAA)
• ANAME pseudo-record for apex domains
• URL pseudo-record for HTTP and HTTPS redirects. Valid HTTPS certificates are generated automatically, HTTPS host gets A+ rating from SSLabs.
• Periodic health checks to filter out unhealthy A/AAAA records
• Lightweight
• Can be geographically distributed. All writes go to central Redis master, all reads are done from local Redis replica
• Request certificates over API

Limitations

• No support for zone files, all records must be managed over API
• Only the most basic and common record types
• No support for DNSSEC
• Only plain old DNS over UDP and TCP, no DoH, no DoT

Requirements

• Node.js, preferrably v12+
• Redis, any version should do as only basic commands are used

Usage

$ npm install --production
$ npm start

Run as SystemD service

If you want to run Postal DNS as a SystemD service, then there's an example service file with comments.

1. Setup commands

As root run the following commands to set up PostalDNS:

$ cd /opt
$ git clone git://github.com/postalsys/postal-dns.git
$ cd postal-dns
$ npm install --production
$ cp systemd/postal-dns.service /etc/systemd/system
$ cp config/default.toml /etc/postal-dns.toml

2. Configuration

Next edit the configuration file /etc/postal-dns.toml and make sure that you have correct configuration.

Also make sure that /etc/systemd/system/postal-dns.service looks correct.

3. Start

Run the following commands as root

$ systemctl enable postal-dns
$ systemctl start postal-dns

General Name Server setup

If you want to use Postal DNS as an authoritative DNS server for your domains then you need at least 2 instances of the server.

Additionally you need to set up both A and so-called GLUE records for the domain names of your name servers. Not all DNS providers allow to set GLUE records.

Here's an example how A records are set up for ns01.pendingdns.com and ns02.pendingdns.com (registrar and DNS provider for these domains is OVH):

And the corresponding GLUE records:

Without proper setup domain registrars do not allow your name server domain names to be used.

API

You can see the entire API docs from the swagger page at http://127.0.0.1:5080/docs

List Zone entries

GET /v1/zone/{zone}/records

$ curl -X GET "http://127.0.0.1:5080/v1/zone/mailtanker.com/records"

{
    "zone": "mailtanker.com",
    "records": [
        {
            "id": "Y29tLm1haWx0YW5rZXIBQQEzc3lKWkkzbGo",
            "type": "A",
            "address": "18.203.150.145"
        },
        {
            "id": "Y29tLm1haWx0YW5rZXIud3d3AUNOQU1FAXhhV1lnbnFaMA",
            "type": "CNAME",
            "subdomain": "www",
            "target": "mailtanker.com"
        }
    ]
}

NB! system records (NS, SOA) have id=null and these records can not be modified over API

Create new Resource Record

POST /v1/zone/{zone}/records

$ curl -X POST "http://127.0.0.1:5080/v1/zone/mailtanker.com/records" -H "Content-Type: application/json" -d '{
    "subdomain": "www",
    "type": "CNAME",
    "target": "@"
}'

{
    "zone": "mailtanker.com",
    "record": "Y29tLm1haWx0YW5rZXIud3d3AUNOQU1FAXhhV1lnbnFaMA"
}

All record types have the following properties

• subdomain (optional) subdomain this record applies to. If blank, or "@" or missing then the record is created for zone domain.
• type one of A, AAAA, CNAME, ANAME, URL, MX, TXT, CAA, NS

Type specific options

A

• address is an IPv4 address
• healthCheck (String) is a health check URI, either tcps?://host:port or https?://host:port/path. When doing TCP checks, successfully opened connection is considered healthy. For HTTP checks 2xx response code is considered healthy. TLS certificate is no validated, self-signed certificates are allowed.

AAAA

• address is an IPv6 address
• healthCheck (String) is a health check URI, either tcps?://host:port or https?://host:port/path. When doing TCP checks, successfully opened connection is considered healthy. For HTTP checks 2xx response code is considered healthy. TLS certificate is no validated, self-signed certificates are allowed.

CNAME

• target is a domain name or "@" for zone domain

ANAME

• target is a domain name

TXT

• data is the data string without quotes. Provide the entire value, do not chop it into substrings

MX

• exchange is the domain name of the MX server
• priority is the priority number of the MX

NS

• ns is the domain name of the NS server

CAA

• value is the domain name of the provider, eg. letsencrypt.org
• tag is the CAA tag, eg. issue or issuewild

URL

• url (string) is the URL to redirect to. If it only has the root path set (eg. http://example.com/) then URLs are redirected with source paths (http://host/path -> http://example.com/path). Otherwise all source URLs are redirected exatly to destination URL (if url is http://example.com/some/path then http://host/path -> http://example.com/some/path)
• code (Number, default is 301) is the HTTP status code to use. Only used if proxy=false
• proxy (boolean, default is false). If true then requests are proxied to destination instead of redirecting. Mostly useful when exposing HTTP-only resources through Postal DNS HTTPS.

Modify existing Resource Record

PUT /v1/zone/{zone}/records/{record}

$ curl -X PUT "http://127.0.0.1:5080/v1/zone/mailtanker.com/records/Y29tLm1haWx0YW5rZXIud3d3AUNOQU1FAXhhV1lnbnFaMA" -H "Content-Type: application/json" -d '{
    "subdomain": "www",
    "type": "CNAME",
    "target": "example.com"
}'

{
    "zone": "mailtanker.com",
    "record": "Y29tLm1haWx0YW5rZXIud3d3AUNOQU1FAXhhV1lnbnFaMA"
}

NB! resulting record ID might be different from the original ID

Delete Resource Record

DELETE /v1/zone/{zone}/records/{record}

$ curl -X DELETE "http://127.0.0.1:5080/v1/zone/mailtanker.com/records/Y29tLm1haWx0YW5rZXIBQQFjT2NWd0d6bE4"

{
    "zone": "mailtanker.com",
    "record": "Y29tLm1haWx0YW5rZXIBQQFjT2NWd0d6bE4",
    "deleted": true
}

Generate Certificate

This API endpoint requests a new certificate from Let's Encrypt or returns a previously generated one.

Certificates can only be requested for domains that:

1. have at least one resource record set for their zone (not important which kind)
2. have correctly pointed NS records to your Postal DNS servers

$ curl -X POST "http://127.0.0.1:5080/v1/acme" -H "Content-Type: application/json" -d '{
    "domains": [
        "mailtanker.com",
        "*.mailtanker.com"
    ]
}'

{
    "dnsNames": ["*.mailtanker.com", "mailtanker.com"],
    "key": "-----BEGIN RSA PRIVATE KEY-----\nMIIEpAIB...",
    "cert": "-----BEGIN CERTIFICATE-----\nMIIFaT...\n",
    "validFrom": "2020-06-03T18:50:52.000Z",
    "expires": "2020-09-01T18:50:52.000Z"
}

License

MIT