bouncycastle - Java Punycode String

Question

I want to punycode a String in order to generate a csr using bouncycastle. Here I need the byte representation of the domain name. E.g

new GeneralName(GeneralName.dNSName, new DEROctetString(bytes..)) 

My question is: How do I encode www.??.tld correctly. I assumed that I could use IDN.toASCII(domain).getBytes(). Unfortunately this fails with:

Caused by: java.text.ParseException: An unassigned code point was found in the input ?
    at java.base/sun.net.idn.StringPrep.map(StringPrep.java:303)
    at java.base/sun.net.idn.StringPrep.prepare(StringPrep.java:426)
    at java.base/java.net.IDN.toASCIIInternal(IDN.java:272)

question from:https://stackoverflow.com/questions/66048061/java-punycode-string

Answer 1

You just need to use the IDN.ALLOW_UNASSIGNED flag:

IDN.toASCII("www.??.tld", IDN.ALLOW_UNASSIGNED)