Parsing the CN out of a certificate DN [duplicate]

Answer 1

If I understood it correctly this should produce the same result, just looks a bit more readable. \w matches any word-character.

"CN=[\\w]*[., ]+[\\w ]*"

If you want something more flexible you can do this:

Matcher m = Pattern.compile("(CN=.*?),[A-Z]{2}=").matcher(dn);
if (m.find())
  cn = m.group(1);

That matches anything between "CN=" and ",XX=", where XX are two uppercase letters. group(1) returns the first group (the match inside the parentheses).

Regexp's aren't as difficult as they look !

Answer 2

Regex expressions, are rather expensive to use. For such a simple task it will probably be an over kill. Instead you could use a simple String split:

String dn = ((X509Certificate) certificate).getIssuerDN().getName();
String CN = getValByAttributeTypeFromIssuerDN(dn,"CN=");

private String getValByAttributeTypeFromIssuerDN(String dn, String attributeType)
{
    String[] dnSplits = dn.split(","); 
    for (String dnSplit : dnSplits) 
    {
        if (dnSplit.contains(attributeType)) 
        {
            String[] cnSplits = dnSplit.trim().split("=");
            if(cnSplits[1]!= null)
            {
                return cnSplits[1].trim();
            }
        }
    }
    return "";
}

Answer 3

I parse a DN like this. You get all attributes as properties:

Principal principal = cert.getSubjectDN();
Properties prop = new Properties();
prop.load(new StringReader(principal.getName().replaceAll(",", "\n")));
prop.list(System.out);
String CN= props.get("CN");

It does not work for duplicate elements like ou or dc though.