Upstream proxy dialer API with psiphon.Dialer signature

psiphon/upstreamproxy/upstreamProxy.go

@@ -0,0 +1,76 @@
+package upstreamproxy
+
+import (
+	"errors"
+	"fmt"
+	"golang.org/x/net/proxy"
+	"net"
+	"net/url"
+)
+
+type DialFunc func(string, string) (net.Conn, error)
+
+type proxyType int
+
+const (
+	HTTP proxyType = iota
+	SOCKS4A
+	SOCKS5
+)
+
+type UpstreamProxyConfig struct {
+	ForwardDialFunc DialFunc
+	ProxyAddress    string
+	ProxyType       proxyType
+	Username        string
+	Password        string
+}
+
+// UpstreamProxyConfig proxy.Dialer interface
+// so we can pass it to proxy.FromURL
+func (u *UpstreamProxyConfig) Dial(network, addr string) (net.Conn, error) {
+	return u.ForwardDialFunc(network, addr)
+}
+
+func NewProxyDialer(config *UpstreamProxyConfig) DialFunc {
+	proxyURI, err := makeProxyUri(config)
+	if err != nil {
+		return func(network, addr string) (net.Conn, error) {
+			return nil, err
+		}
+	}
+	dialer, err := proxy.FromURL(proxyURI, config)
+	return dialer.Dial
+}
+
+func proxySchemeFromType(ptype proxyType) (string, error) {
+	proxySchemeDict := map[proxyType]string{
+		HTTP:    "http",
+		SOCKS4A: "socks4a",
+		SOCKS5:  "socks5",
+	}
+	if val, ok := proxySchemeDict[ptype]; ok {
+		return val, nil
+	}
+	return "", errors.New("Unsupported proxy type")
+}
+
+func makeProxyUri(config *UpstreamProxyConfig) (*url.URL, error) {
+	scheme, err := proxySchemeFromType(config.ProxyType)
+	if err != nil {
+		return nil, err
+	}
+	var uriUserInfo string
+	if config.Username != "" {
+		uriUserInfo = config.Username
+	}
+	if config.Password != "" {
+		uriUserInfo = fmt.Sprint(uriUserInfo, ":", config.Password)
+	}
+	if uriUserInfo != "" {
+		uriUserInfo = fmt.Sprint(uriUserInfo, "@")
+	}
+	proxyUriStr := fmt.Sprint(scheme, "://", uriUserInfo, config.ProxyAddress)
+
+	return url.Parse(proxyUriStr)
+}