[Svn] [roundcube/roundcubemail] 4920f3: krb_authentication fixes (#6471)

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/roundcube/roundcubemail
  Commit: 4920f3ef2326fa0b1c72da7f8f7b325782a46fe4
      https://github.com/roundcube/roundcubemail/commit/4920f3ef2326fa0b1c72da7f8f7b325782a46fe4
  Author: urusha <urusha.v1.0 at gmail.com>
  Date:   2018-10-03 (Wed, 03 Oct 2018)

  Changed paths:
    M plugins/krb_authentication/config.inc.php.dist
    M plugins/krb_authentication/krb_authentication.php

  Log Message:
  -----------
  krb_authentication fixes (#6471)

* krb_authentication: remove default principal

krb_authentication_context must be set to the right value to make GSSAPI work, we should not have any default for it outside config files, it could confuse users. We already handle empty/bad context in rcube_imap_generic.php, Net_Sieve, Net_SMTP.

* krb_authentication: config.php.dist fix

GSSAPI is better for searching, since GSS API is not used widely.
host.fqdn at REALM.NAME is actually never used without service-prefix, on the other side it may be valid to use 'computername$' or 'username' with Samba/Active Directory, the common name for all these - 'principal'.

* krb_authentication: raise error on empty context



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