[Dovecot] Username from rfc822Name subject alternative name

[Timo Sirainen]

On 9.4.2012, at 16.51, Бранко Мајић wrote:

> I'm looking into adding support for extracting the username from client certificate's rfc822Name (from the subjectAltName extension).
> 
> The question I have is what would be the best approach to do this? Current implementation has a kind of clean code since it just goes through the subject name, extracting the values with X509_NAME_get_text_by_NID (while NID is obtained with OBJ_txt2nid). If I were to add this, it's bound to make the code a little bit more complicated since SAN's can't be retrieved in the same way.
> 
> So far in terms of options I have, I can see the following:
> 
> 1. Create a distinct configuration option for the ssl_cert_username_field (i.e. specify something like "sanrfc822Name" to have Dovecot extract the username from the designated alternative name).

I'm not sure if this is a good idea, but what about:

ssl_cert_username_field = subjectAltName:rfc822Name

> 2. Make the current code fail-over to rfc822Name SAN if emailAddress is provided for ssl_cert_username (less invasion in code, but less flexibility as well).

Automatic failover seems dangerous.