fix: switch port when falling back between HTTP/HTTPS protocols

- When falling back from HTTPS to HTTP on port 443, now switches to port 80
- When falling back from HTTP to HTTPS on port 80, now switches to port 443
- Prevents 'plain HTTP request sent to HTTPS port' errors during fallback
- Added test cases for determineMostLikelySchemeOrder and port fallback logic

Author: ehsandeep

runner/ports_optimization_test.go

@@ -0,0 +1,115 @@
+package runner
+
+import (
+	"testing"
+
+	"github.com/projectdiscovery/httpx/common/httpx"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDetermineMostLikelySchemeOrder(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "port 80 should return HTTP",
+			input:    "example.com:80",
+			expected: httpx.HTTP,
+		},
+		{
+			name:     "port 8080 should return HTTP",
+			input:    "example.com:8080",
+			expected: httpx.HTTP,
+		},
+		{
+			name:     "port 443 should return HTTPS",
+			input:    "example.com:443",
+			expected: httpx.HTTPS,
+		},
+		{
+			name:     "port 8443 should return HTTP (port > 1024)",
+			input:    "example.com:8443",
+			expected: httpx.HTTP,
+		},
+		{
+			name:     "no port should return HTTPS",
+			input:    "example.com",
+			expected: httpx.HTTPS,
+		},
+		{
+			name:     "port 443 with IP should return HTTPS",
+			input:    "1.2.3.4:443",
+			expected: httpx.HTTPS,
+		},
+		{
+			name:     "port 80 with IP should return HTTP",
+			input:    "1.2.3.4:80",
+			expected: httpx.HTTP,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			result := determineMostLikelySchemeOrder(tc.input)
+			require.Equal(t, tc.expected, result, "unexpected scheme for input %s", tc.input)
+		})
+	}
+}
+
+func TestSwitchPortForFallback(t *testing.T) {
+	// Test that when switching from HTTPS to HTTP on port 443, port should become 80
+	// And when switching from HTTP to HTTPS on port 80, port should become 443
+	tests := []struct {
+		name            string
+		inputPort       string
+		inputProtocol   string
+		expectedNewPort string
+	}{
+		{
+			name:            "HTTPS:443 fallback should switch to port 80",
+			inputPort:       "443",
+			inputProtocol:   httpx.HTTPS,
+			expectedNewPort: "80",
+		},
+		{
+			name:            "HTTP:80 fallback should switch to port 443",
+			inputPort:       "80",
+			inputProtocol:   httpx.HTTP,
+			expectedNewPort: "443",
+		},
+		{
+			name:            "HTTPS:8443 fallback should keep port 8443",
+			inputPort:       "8443",
+			inputProtocol:   httpx.HTTPS,
+			expectedNewPort: "8443", // non-default port stays the same
+		},
+		{
+			name:            "HTTP:8080 fallback should keep port 8080",
+			inputPort:       "8080",
+			inputProtocol:   httpx.HTTP,
+			expectedNewPort: "8080", // non-default port stays the same
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			newPort := getPortForFallback(tc.inputPort, tc.inputProtocol)
+			require.Equal(t, tc.expectedNewPort, newPort, "unexpected port for fallback")
+		})
+	}
+}
+
+// getPortForFallback returns the port to use when falling back to the other protocol
+// This is the logic used in runner.go analyze function
+func getPortForFallback(currentPort, currentProtocol string) string {
+	if currentProtocol == httpx.HTTPS && currentPort == "443" {
+		return "80"
+	}
+	if currentProtocol == httpx.HTTP && currentPort == "80" {
+		return "443"
+	}
+	return currentPort
+}
+

runner/runner.go

@@ -1754,10 +1754,21 @@ retry:
 		errString = strings.TrimSpace(splitErr[len(splitErr)-1])
 
 		if !retried && origProtocol == httpx.HTTPorHTTPS {
+			// switch protocol and adjust port accordingly
 			if protocol == httpx.HTTPS {
 				protocol = httpx.HTTP
+				// if port is 443 (default HTTPS), switch to 80 (default HTTP)
+				if URL.Port() == "443" {
+					URL.UpdatePort("80")
+					target.Host = URL.Hostname() + ":80"
+				}
 			} else {
 				protocol = httpx.HTTPS
+				// if port is 80 (default HTTP), switch to 443 (default HTTPS)
+				if URL.Port() == "80" {
+					URL.UpdatePort("443")
+					target.Host = URL.Hostname() + ":443"
+				}
 			}
 			retried = true
 			goto retry