'To further filter the certificates that are trusted.
If the config option \'trusted_issuer\' is absent or does
not contain the trusted issuer DN, no certificates
will be allowed in tokenless authorization.
:param env: The env contains the client issuer\'s attributes
:type env: dict
:returns: True if client_issuer is trusted; otherwise False'

def _validate_trusted_issuer(self, request):

    if (not CONF.tokenless_auth.trusted_issuer):
        return False
    issuer = request.environ.get(CONF.tokenless_auth.issuer_attribute)
    if (not issuer):
        msg = 'Cannot    find    client    issuer    in    env    by    the    issuer    attribute    -    %s.'
        LOG.info(msg, CONF.tokenless_auth.issuer_attribute)
        return False
    if (issuer in CONF.tokenless_auth.trusted_issuer):
        return True
    msg = 'The    client    issuer    %(client_issuer)s    does    not    match    with    the    trusted    issuer    %(trusted_issuer)s'
    LOG.info(msg, {'client_issuer': issuer, 'trusted_issuer': CONF.tokenless_auth.trusted_issuer})
    return False
