certigo/starttls/dialer.go

package starttls

import (
	"crypto/tls"
	"net"
	"time"
)

type timeoutError struct{}

func (timeoutError) Error() string   { return "tls: DialWithDialer timed out" }
func (timeoutError) Timeout() bool   { return true }
func (timeoutError) Temporary() bool { return true }

// Dialer is an interface for dialers (either net.Dialer, or http_dialer.HttpTunnel)
type Dialer interface {
	Dial(network, address string) (net.Conn, error)
}

// Internal copy of tls.DialWithDialer, adapter so it can work with HTTP CONNECT dialers.
// See: https://golang.org/pkg/crypto/tls/#DialWithDialer
func dialWithDialer(dialer Dialer, timeout time.Duration, network, addr string, config *tls.Config) (*tls.Conn, error) {
	var errChannel chan error
	if timeout != 0 {
		errChannel = make(chan error, 2)
		time.AfterFunc(timeout, func() {
			errChannel <- timeoutError{}
		})
	}

	rawConn, err := dialer.Dial(network, addr)
	if err != nil {
		return nil, err
	}

	conn := tls.Client(rawConn, config)
	if timeout == 0 {
		err = conn.Handshake()
	} else {
		go func() {
			errChannel <- conn.Handshake()
		}()

		err = <-errChannel
	}

	if err != nil {
		rawConn.Close()
		return nil, err
	}

	return conn, nil
}