tls-alpn-01 challenge, you prove to the CA that you are able to control the web server of the domain to be authorized, by letting it respond to a request with a specific self-signed cert utilizing the ALPN extension. This challenge is specified in RFC 8737.
TlsAlpn01Challenge provides a byte array called
TlsAlpn01Challenge challenge = auth.findChallenge(TlsAlpn01Challenge.class); Identifier identifier = auth.getIdentifier(); byte acmeValidation = challenge.getAcmeValidation();
You need to create a self-signed certificate with the domain to be validated set as the only Subject Alternative Name. The
acmeValidation must be set as DER encoded
OCTET STRING extension with the object id
184.108.40.206.220.127.116.11.31. It is required to set this extension as critical.
After that, configure your web server so it will use this certificate on an incoming TLS request having the SNI
identifier and the ALPN protocol
TlsAlpn01Challenge class does not generate a self-signed certificate for you, as it would require Bouncy Castle. However, there is a utility method in the acme4j-utils module for this use case:
KeyPair certKeyPair = KeyPairUtils.createKeyPair(2048); X509Certificate cert = CertificateUtils. createTlsAlpn01Certificate(certKeyPair, identifier, acmeValidation);
certKeyPair to let your web server respond to TLS requests containing an ALPN extension with the value
acme-tls/1 and a SNI extension containing your subject (
The request is sent to port 443 only. If your domain has multiple IP addresses, the CA randomly selects one of them. There is no way to choose a different port or a fixed IP address.