}
                return ssn.acquire();
            }
            else if ( log.isTraceEnabled() ) {
                log.trace("Existing session " + ssn + " does not match " + tf.getCredentials());
            }
        }

        /* logoff old sessions */
        if ( tf.getConfig().getSessionTimeout() > 0 && this.sessionExpiration < ( now = System.currentTimeMillis() ) ) {

            log.debug("Secure negotiation does not apply");
            return;
        }

        Smb2NegotiateResponse nego = (Smb2NegotiateResponse) trans.getNegotiateResponse();
        if ( nego.getSelectedDialect().atLeast(DialectVersion.SMB311) ) {
            // have preauth integrity instead
            log.debug("Secure negotiation does not apply, is SMB3.1");
            return;
        }

    }

/**
 * The CIFS protocol provides for DOS "wildcards" to be used as
 * a performance enhancement. The client does not have to filter
 * the names and the server does not have to return all directory
 * entries.
 * <p>
 * The wildcard expression may consist of two special meta
 * characters in addition to the normal filename characters. The '*'

                        // request digest
                        // Ignore a missing signature for SMB < 3.0, as
                        // - the specification does not clearly require that (it does for SMB3+)
                        // - there seem to be server implementations (known: EMC Isilon) that do not sign the final
                        // response

        }
        catch ( UnsupportedEncodingException uee ) {
            throw new CIFSException(
                "The default OEM encoding " + SmbConstants.DEFAULT_OEM_ENCODING + " does not appear to be supported by this JRE.");
        }

        this.localPid = (int) ( Math.random() * 65536d );
        this.localTimeZone = TimeZone.getDefault();
        this.random = new SecureRandom();

    boolean isUseSMB2OnlyNegotiation ();


    /**
     * Enforce secure negotiation
     * 
     * Property <tt>jcifs.smb.client.requireSecureNegotiate</tt> (boolean, default true)
     * 
     * This does not provide any actual downgrade protection if SMB1 is allowed.
     * 
     * It will also break connections with SMB2 servers that do not properly sign error responses.
     * 

    }


    /**
     * The CIFS protocol provides for DOS "wildcards" to be used as
     * a performance enhancement. The client does not have to filter
     * the names and the server does not have to return all directory
     * entries.
     * <p>
     * The wildcard expression may consist of two special meta

    // against this issue
    public void testEnumBufferSize () throws IOException {
        CIFSContext ctx = getContext();
        int origBufferSize = ctx.getConfig().getMaximumBufferSize();
        // odd buffer size that does match the alignment
        int tryBufferSize = 1023;
        final int bufSize[] = new int[] {
            origBufferSize
        };
        ctx = withConfig(ctx, new DelegatingConfiguration(ctx.getConfig()) {