acme-dns

A simplified DNS server with a RESTful HTTP API to provide a simple way to automate ACME DNS challenges.

Why?

Many DNS servers do not provide an API to enable automation for the ACME DNS challenges. Those which do, give the keys way too much power. Leaving the keys laying around your random boxes is too often a requirement to have a meaningful process automation.

Acme-dns provides a simple API exclusively for TXT record updates and should be used with ACME magic "_acme-challenge" - subdomain CNAME records. This way, in the unfortunate exposure of API keys, the effetcs are limited to the subdomain TXT record in question.

So basically it boils down to accessibility and security

Features

• Simplified DNS server, serving your ACME DNS challenges (TXT)
• Custom records (have your required A, AAAA, NS, etc. records served)
• HTTP API automatically acquires and uses Let's Encrypt TLS certificate
• Limit /update API endpoint access to specific CIDR mask(s), defined in the /register request
• Supports SQLite & PostgreSQL as DB backends
• Simple deployment (it's Go after all)

Usage

Using acme-dns is a three-step process (provided you already have the self-hosted server set up, or are using a service like acme-dns.io):

• Get credentials and unique subdomain (simple POST request to eg. https://auth.acme-dns.io/register)
• Create a (ACME magic) CNAME record to your existing zone, pointing to the subdomain you got from the registration. (eg. _acme-challenge.domainiwantcertfor.tld. CNAME a097455b-52cc-4569-90c8-7a4b97c6eba8.auth.example.org )
• Use your credentials to POST a new DNS challenge values to an acme-dns server for the CA to validate them off of.
• Crontab and forget.

API

Register endpoint

The method returns a new unique subdomain and credentials needed to update your record. Fulldomain is where you can point your own _acme-challenge subdomain CNAME record to. With the credentials, you can update the TXT response in the service to match the challenge token, later referred as ___validation_token_recieved_from_the_ca___, given out by the Certificate Authority.

Optional:: You can POST JSON data to limit the /update requests to predefined source networks using CIDR notation.

POST /register

OPTIONAL Example input

{
    "allowfrom": [
        "192.168.100.1/24",
        "1.2.3.4/32",
        "2002:c0a8:2a00::0/40",
}

Status: 201 Created

{
    "allowfrom": [
        "192.168.100.1/24",
        "1.2.3.4/32"
    ],
    "fulldomain": "8e5700ea-a4bf-41c7-8a77-e990661dcc6a.auth.acme-dns.io",
    "password": "htB9mR9DYgcu9bX_afHF62erXaH2TS7bg9KW3F7Z",
    "subdomain": "8e5700ea-a4bf-41c7-8a77-e990661dcc6a",
    "username": "c36f50e8-4632-44f0-83fe-e070fef28a10"
}

Update endpoint

The method allows you to update the TXT answer contents of your unique subdomain. Usually carried automatically by automated ACME client.

POST /update

Required headers

Header name	Description	Example
X-Api-User	UUIDv4 username recieved from registration	X-Api-User: c36f50e8-4632-44f0-83fe-e070fef28a10
X-Api-Key	Password recieved from registration	X-Api-Key: htB9mR9DYgcu9bX_afHF62erXaH2TS7bg9KW3F7Z

Example input

{
    "subdomain": "8e5700ea-a4bf-41c7-8a77-e990661dcc6a",
    "txt": "___validation_token_recieved_from_the_ca___",
}

Response

Status: 200 OK

{
    "txt": "___validation_token_recieved_from_the_ca___",
}

Self-hosted

You are encouraged to run your own acme-dns instance, because you are effectively authorizing the acme-dns server to act on your behalf in providing the answer to challengeing CA, making the instance able to request (and get issued) a TLS certificate for the domain that has CNAME pointing to it.

Check out how in the INSTALL section.

As a service

Acme-dns instance is running as a service for everyone wanting to get on in fast. You can find it at auth.acme-dns.io, so to get started, try: curl -X POST https://auth.acme-dns.io/register

Installation

1. Install Go

2. Clone this repo: git clone https://github.com/joohoi/acme-dns $GOPATH/src/acme-dns

3. Install govendor. ‘go get -u github.com/kardianos/govendor’ . This is used for dependency handling.

4. Get dependencies: cd $GOPATH/src/acme-dns and govendor sync

5. Build ACME-DNS: go build

6. Edit config.cfg to suit your needs (see configuration)

7. Run acme-dns. Please note that acme-dns needs to open a privileged port (53, domain), so it needs to be run with elevated privileges.

Configuration

[general]
# dns interface
listen = ":53"
# protocol, "udp", "udp4", "udp6" or "tcp", "tcp4", "tcp6"
protocol = "udp"
# domain name to serve the requests off of 
domain = "auth.example.org"
# zone name server 
nsname = "ns1.auth.example.org"
# admin email address, where @ is substituted with .
nsadmin = "admin.example.org"
# predefined records served in addition to the TXT
records = [
    # default A
    "auth.example.org. A 192.168.1.100",
    # A 
    "ns1.auth.example.org. A 192.168.1.100",
    "ns2.auth.example.org. A 192.168.1.100",
    # NS
    "auth.example.org. NS ns1.auth.example.org.",
    "auth.example.org. NS ns2.auth.example.org.",
]
# debug messages from CORS etc
debug = false

[database]
# Database engine to use, sqlite3 or postgres
engine = "sqlite3"
# Connection string, filename for sqlite3 and postgres://$username:$password@$host/$db_name for postgres
connection = "acme-dns.db"
# connection = "postgres://user:password@localhost/acmedns_db"

[api]
# domain name to listen requests for, mandatory if using tls = "letsencrypt"
api_domain = ""
# listen port, eg. 443 for default HTTPS
port = "8080"
# possible values: "letsencrypt", "cert", "none"
tls = "none"
# only used if tls = "cert"
tls_cert_privkey = "/etc/tls/example.org/privkey.pem"
tls_cert_fullchain = "/etc/tls/example.org/fullchain.pem"
# CORS AllowOrigins, wildcards can be used
corsorigins = [
    "*"
]

[logconfig]
# logging level: "error", "warning", "info" or "debug"
loglevel = "debug"
# possible values: stdout, TODO file & integrations
logtype = "stdout"
# file path for logfile TODO
# logfile = "./acme-dns.log"
# format, either "json" or "text" 
logformat = "text"
# use HTTP header to get the client ip
use_header = false
# header name to pull the ip address / list of ip addresses from
header_name = "X-Forwarded-For"

Changelog

• v0.1 Initial release

TODO

• Logging to a file
• Want to see something implemented, make a feature request!

Contributing

acme-dns is open for contributions. If you have an improvement, please open a Pull Request.

License

acme-dns is released under the MIT License.