Function continueClientHandshake

control/controlbase/handshake.go:120–190

(ctx context.Context, conn net.Conn, s *symmetricState, machineKey, machineEphemeral key.MachinePrivate, controlKey key.MachinePublic, protocolVersion uint16)

}

func continueClientHandshake(ctx context.Context, conn net.Conn, s *symmetricState, machineKey, machineEphemeral key.MachinePrivate, controlKey key.MachinePublic, protocolVersion uint16) (*Conn, error) {
	// No matter what, this function can only run once per s. Ensure
	// attempted reuse causes a panic.
	defer func() {
		s.finished = true
	}()

	if deadline, ok := ctx.Deadline(); ok {
		if err := conn.SetDeadline(deadline); err != nil {
			return nil, fmt.Errorf("setting conn deadline: %w", err)
		}
		defer func() {
			conn.SetDeadline(time.Time{})
		}()
	}

	// Read in the payload and look for errors/protocol violations from the server.
	var resp responseMessage
	if _, err := io.ReadFull(conn, resp.Header()); err != nil {
		return nil, fmt.Errorf("reading response header: %w", err)
	}
	if resp.Type() != msgTypeResponse {
		if resp.Type() != msgTypeError {
			return nil, fmt.Errorf("unexpected response message type %d", resp.Type())
		}
		msg := make([]byte, resp.Length())
		if _, err := io.ReadFull(conn, msg); err != nil {
			return nil, err
		}
		return nil, fmt.Errorf("server error: %q", msg)
	}
	if resp.Length() != len(resp.Payload()) {
		return nil, fmt.Errorf("wrong length %d received for handshake response", resp.Length())
	}
	if _, err := io.ReadFull(conn, resp.Payload()); err != nil {
		return nil, err
	}

	// <- e, ee, se
	controlEphemeralPub := key.MachinePublicFromRaw32(mem.B(resp.EphemeralPub()))
	s.MixHash(controlEphemeralPub.UntypedBytes())
	if _, err := s.MixDH(machineEphemeral, controlEphemeralPub); err != nil {
		return nil, fmt.Errorf("computing ee: %w", err)
	}
	cipher, err := s.MixDH(machineKey, controlEphemeralPub)
	if err != nil {
		return nil, fmt.Errorf("computing se: %w", err)
	}
	if err := s.DecryptAndHash(cipher, nil, resp.Tag()); err != nil {
		return nil, fmt.Errorf("decrypting payload: %w", err)
	}

	c1, c2, err := s.Split()
	if err != nil {
		return nil, fmt.Errorf("finalizing handshake: %w", err)
	}

	c := &Conn{