diff options
Diffstat (limited to 'obfs4.go')
| -rw-r--r-- | obfs4.go | 79 |
1 files changed, 69 insertions, 10 deletions
@@ -25,7 +25,10 @@ * POSSIBILITY OF SUCH DAMAGE. */ -// Package obfs4 implements the obfs4 protocol. +// Package obfs4 implements the obfs4 protocol. For the most part, obfs4 +// connections are exposed via the net.Conn and net.Listener interface, though +// accepting connections as a server requires calling ServerHandshake on the +// conn to finish connection establishment. package obfs4 import ( @@ -46,7 +49,7 @@ const ( connectionTimeout = time.Duration(30) * time.Second maxCloseDelayBytes = framing.MaximumSegmentLength * 5 - maxCloseDelay = 60 + maxCloseDelay = 60 ) type connState int @@ -75,7 +78,7 @@ type Obfs4Conn struct { isServer bool // Server side state. - listener *Obfs4Listener + listener *Obfs4Listener startTime time.Time } @@ -116,7 +119,7 @@ func (c *Obfs4Conn) closeAfterDelay() { // I-it's not like I w-wanna handshake with you or anything. B-b-baka! defer c.conn.Close() - delay := time.Duration(c.listener.closeDelay) * time.Second + connectionTimeout + delay := time.Duration(c.listener.closeDelay)*time.Second + connectionTimeout deadline := c.startTime.Add(delay) if time.Now().After(deadline) { return @@ -302,14 +305,22 @@ func (c *Obfs4Conn) serverHandshake(nodeID *ntor.NodeID, keypair *ntor.Keypair) return } +// CanHandshake queries the connection state to see if it is appropriate to +// call ServerHandshake to complete connection establishment. func (c *Obfs4Conn) CanHandshake() bool { return c.state == stateInit } +// CanReadWrite queries the connection state to see if it is possible to read +// and write data. func (c *Obfs4Conn) CanReadWrite() bool { return c.state == stateEstablished } +// ServerHandshake completes the server side of the obfs4 handshake. Servers +// are required to call this after accepting a connection. ServerHandshake +// will treat errors encountered during the handshake as fatal and drop the +// connection before returning. func (c *Obfs4Conn) ServerHandshake() error { // Handshakes when already established are a no-op. if c.CanReadWrite() { @@ -332,6 +343,7 @@ func (c *Obfs4Conn) ServerHandshake() error { return err } +// Read implements the net.Conn Read method. func (c *Obfs4Conn) Read(b []byte) (n int, err error) { if !c.CanReadWrite() { return 0, syscall.EINVAL @@ -350,6 +362,7 @@ func (c *Obfs4Conn) Read(b []byte) (n int, err error) { return } +// WriteTo implements the io.WriterTo WriteTo method. func (c *Obfs4Conn) WriteTo(w io.Writer) (n int64, err error) { if !c.CanReadWrite() { return 0, syscall.EINVAL @@ -386,6 +399,10 @@ func (c *Obfs4Conn) WriteTo(w io.Writer) (n int64, err error) { return } +// Write implements the net.Conn Write method. The obfs4 lengt obfuscation is +// done based on the amount of data passed to Write (each call to Write results +// in up to 2 frames of padding). Passing excessively short buffers to Write +// will result in significant overhead. func (c *Obfs4Conn) Write(b []byte) (n int, err error) { if !c.CanReadWrite() { return 0, syscall.EINVAL @@ -439,6 +456,7 @@ func (c *Obfs4Conn) Write(b []byte) (n int, err error) { return } +// Close closes the connection. func (c *Obfs4Conn) Close() error { if c.conn == nil { return syscall.EINVAL @@ -449,6 +467,7 @@ func (c *Obfs4Conn) Close() error { return c.conn.Close() } +// LocalAddr returns the local network address. func (c *Obfs4Conn) LocalAddr() net.Addr { if c.state == stateClosed { return nil @@ -457,6 +476,7 @@ func (c *Obfs4Conn) LocalAddr() net.Addr { return c.conn.LocalAddr() } +// RemoteAddr returns the remote network address. func (c *Obfs4Conn) RemoteAddr() net.Addr { if c.state == stateClosed { return nil @@ -465,10 +485,13 @@ func (c *Obfs4Conn) RemoteAddr() net.Addr { return c.conn.RemoteAddr() } +// SetDeadline is a convoluted way to get syscall.ENOTSUP. func (c *Obfs4Conn) SetDeadline(t time.Time) error { return syscall.ENOTSUP } +// SetReadDeadline implements the net.Conn SetReadDeadline method. Connections +// must be in the established state (CanReadWrite). func (c *Obfs4Conn) SetReadDeadline(t time.Time) error { if !c.CanReadWrite() { return syscall.EINVAL @@ -477,11 +500,15 @@ func (c *Obfs4Conn) SetReadDeadline(t time.Time) error { return c.conn.SetReadDeadline(t) } +// SetWriteDeadline is a convoluted way to get syscall.ENOTSUP. func (c *Obfs4Conn) SetWriteDeadline(t time.Time) error { return syscall.ENOTSUP } -func Dial(network, address, nodeID, publicKey string) (net.Conn, error) { +// DialObfs4 connects to the remote address on the network, and handshakes with +// the peer's obfs4 Node ID and Identity Public Key. nodeID and publicKey are +// expected as strings containing the Base64 encoded values. +func DialObfs4(network, address, nodeID, publicKey string) (*Obfs4Conn, error) { // Decode the node_id/public_key. pub, err := ntor.PublicKeyFromBase64(publicKey) if err != nil { @@ -516,21 +543,36 @@ func Dial(network, address, nodeID, publicKey string) (net.Conn, error) { return c, nil } -// Obfs4Listener a obfs4 network listener. Servers should use variables of -// type Listener instead of assuming obfs4. +// Obfs4Listener is the implementation of the net.Listener interface for obfs4 +// connections. type Obfs4Listener struct { listener net.Listener keyPair *ntor.Keypair nodeID *ntor.NodeID - seed *DrbgSeed + seed *DrbgSeed closeDelayBytes int - closeDelay int + closeDelay int } +// Accept implements the Accept method of the net.Listener interface; it waits +// for the next call and returns a generic net.Conn. Callers are responsible +// for completing the handshake by calling Obfs4Conn.ServerHandshake(). func (l *Obfs4Listener) Accept() (net.Conn, error) { + conn, err := l.AcceptObfs4() + if err != nil { + return nil, err + } + + return conn, nil +} + +// AcceptObfs4 accepts the next incoming call and returns a new connection. +// Callers are responsible for completing the handshake by calling +// Obfs4Conn.ServerHandshake(). +func (l *Obfs4Listener) AcceptObfs4() (*Obfs4Conn, error) { // Accept a connection. c, err := l.listener.Accept() if err != nil { @@ -552,14 +594,19 @@ func (l *Obfs4Listener) Accept() (net.Conn, error) { return cObfs, nil } +// Close stops listening on the Obfs4 endpoint. Already Accepted connections +// are not closed. func (l *Obfs4Listener) Close() error { return l.listener.Close() } +// Addr returns the listener's network address. func (l *Obfs4Listener) Addr() net.Addr { return l.listener.Addr() } +// PublicKey returns the listener's Identity Public Key, a Base64 encoded +// obfs4.ntor.PublicKey. func (l *Obfs4Listener) PublicKey() string { if l.keyPair == nil { return "" @@ -568,7 +615,19 @@ func (l *Obfs4Listener) PublicKey() string { return l.keyPair.Public().Base64() } -func Listen(network, laddr, nodeID, privateKey, seed string) (net.Listener, error) { +// NodeID returns the listener's NodeID, a Base64 encoded obfs4.ntor.NodeID. +func (l *Obfs4Listener) NodeID() string { + if l.nodeID == nil { + return "" + } + + return l.nodeID.Base64() +} + +// ListenObfs4 annnounces on the network and address, and returns and +// Obfs4Listener. nodeId, privateKey and seed are expected as strings +// containing the Base64 encoded values. +func ListenObfs4(network, laddr, nodeID, privateKey, seed string) (*Obfs4Listener, error) { var err error // Decode node_id/private_key. |