bug: fasthttpproxy dialers return nil DialFunc on error, causing panic (#2248) (#2279)

fasthttpproxy/dialer.go

@@ -21,6 +21,15 @@ var (
 	tmpURL       = &url.URL{Scheme: httpsScheme, Host: "example.com"}
 )
 
+func dialFuncOrError(dialFunc fasthttp.DialFunc, err error) fasthttp.DialFunc {
+	if err == nil {
+		return dialFunc
+	}
+	return func(addr string) (net.Conn, error) {
+		return nil, err
+	}
+}
+
 // Dialer embeds both fasthttp.TCPDialer and httpproxy.Config, allowing it
 // to take advantage of the optimizations provided by fasthttp for dialing while also
 // utilizing the finer-grained configuration options offered by httpproxy.

fasthttpproxy/dialer_test.go

@@ -261,6 +261,65 @@ func TestHTTPProxyDialRejectsTargetAddrContainingNewlines(t *testing.T) {
 	}
 }
 
+func TestProxyDialerConstructorsReturnErroringDialFunc(t *testing.T) {
+	t.Setenv("HTTP_PROXY", "socket6://127.0.0.1:8080")
+	t.Setenv("HTTPS_PROXY", "socket6://127.0.0.1:8080")
+	t.Setenv("NO_PROXY", "")
+
+	tests := []struct {
+		name string
+		fn   func() fasthttp.DialFunc
+	}{
+		{
+			name: "http",
+			fn: func() fasthttp.DialFunc {
+				return FasthttpHTTPDialer("socket6://127.0.0.1:8080")
+			},
+		},
+		{
+			name: "http dual stack",
+			fn: func() fasthttp.DialFunc {
+				return FasthttpHTTPDialerDualStack("socket6://127.0.0.1:8080")
+			},
+		},
+		{
+			name: "socks",
+			fn: func() fasthttp.DialFunc {
+				return FasthttpSocksDialer("socket6://127.0.0.1:8080")
+			},
+		},
+		{
+			name: "socks dual stack",
+			fn: func() fasthttp.DialFunc {
+				return FasthttpSocksDialerDualStack("socket6://127.0.0.1:8080")
+			},
+		},
+		{
+			name: "env",
+			fn:   FasthttpProxyHTTPDialer,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dialFunc := tt.fn()
+			if dialFunc == nil {
+				t.Fatalf("unexpected nil dial func")
+			}
+			conn, err := dialFunc("example.com:80")
+			if conn != nil {
+				conn.Close()
+			}
+			if err == nil {
+				t.Fatalf("expected error")
+			}
+			if err.Error() != "proxy: unknown scheme: socket6" {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		})
+	}
+}
+
 func startProxyServer(t *testing.T, ports []string, counts []atomic.Int64) (lns []net.Listener) {
 	for i, port := range ports {
 		ln, err := net.Listen("tcp", ":"+port)

fasthttpproxy/http.go

@@ -30,8 +30,8 @@ func FasthttpHTTPDialer(proxy string) fasthttp.DialFunc {
 //	}
 func FasthttpHTTPDialerTimeout(proxy string, timeout time.Duration) fasthttp.DialFunc {
 	d := Dialer{Config: httpproxy.Config{HTTPProxy: proxy, HTTPSProxy: proxy}, Timeout: timeout, ConnectTimeout: timeout}
-	dialFunc, _ := d.GetDialFunc(false)
+	dialFunc, err := d.GetDialFunc(false)
-	return dialFunc
+	return dialFuncOrError(dialFunc, err)
 }
 
 // FasthttpHTTPDialerDualStack returns a fasthttp.DialFunc that dials using
@@ -60,6 +60,6 @@ func FasthttpHTTPDialerDualStackTimeout(proxy string, timeout time.Duration) fas
 		Config: httpproxy.Config{HTTPProxy: proxy, HTTPSProxy: proxy}, Timeout: timeout, ConnectTimeout: timeout,
 		DialDualStack: true,
 	}
-	dialFunc, _ := d.GetDialFunc(false)
+	dialFunc, err := d.GetDialFunc(false)
-	return dialFunc
+	return dialFuncOrError(dialFunc, err)
 }

fasthttpproxy/proxy_env.go

@@ -34,6 +34,6 @@ func FasthttpProxyHTTPDialer() fasthttp.DialFunc {
 //	}
 func FasthttpProxyHTTPDialerTimeout(timeout time.Duration) fasthttp.DialFunc {
 	d := Dialer{Timeout: timeout, ConnectTimeout: timeout}
-	dialFunc, _ := d.GetDialFunc(true)
+	dialFunc, err := d.GetDialFunc(true)
-	return dialFunc
+	return dialFuncOrError(dialFunc, err)
 }

fasthttpproxy/socks5.go

@@ -15,8 +15,8 @@ import (
 //	}
 func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {
 	d := Dialer{Config: httpproxy.Config{HTTPProxy: proxyAddr, HTTPSProxy: proxyAddr}}
-	dialFunc, _ := d.GetDialFunc(false)
+	dialFunc, err := d.GetDialFunc(false)
-	return dialFunc
+	return dialFuncOrError(dialFunc, err)
 }
 
 // FasthttpSocksDialerDualStack returns a fasthttp.DialFunc that dials using
@@ -29,6 +29,6 @@ func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {
 //	}
 func FasthttpSocksDialerDualStack(proxyAddr string) fasthttp.DialFunc {
 	d := Dialer{Config: httpproxy.Config{HTTPProxy: proxyAddr, HTTPSProxy: proxyAddr}, DialDualStack: true}
-	dialFunc, _ := d.GetDialFunc(false)
+	dialFunc, err := d.GetDialFunc(false)
-	return dialFunc
+	return dialFuncOrError(dialFunc, err)
 }