Fix CHISEL_KEY environment variable ignored when --keyfile not set (#571)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jpillora <633843+jpillora@users.noreply.github.com>

main.go

@@ -237,7 +237,8 @@ func server(args []string) {
 	}
 	if config.KeyFile == "" {
 		config.KeyFile = settings.Env("KEY_FILE")
-	} else if config.KeySeed == "" {
+	}
+	if config.KeySeed == "" {
 		config.KeySeed = settings.Env("KEY")
 	}
 	if config.Auth == "" {

test/e2e/env_key_test.go

@@ -0,0 +1,65 @@
+package e2e_test
+
+import (
+	"os"
+	"testing"
+
+	chclient "github.com/jpillora/chisel/client"
+	chserver "github.com/jpillora/chisel/server"
+)
+
+func TestChiselKeyEnvironmentVariable(t *testing.T) {
+	// Set the CHISEL_KEY environment variable
+	os.Setenv("CHISEL_KEY", "test-key-value")
+	defer os.Unsetenv("CHISEL_KEY")
+
+	tmpPort := availablePort()
+	
+	// Create server with empty config - should pick up CHISEL_KEY env var
+	serverConfig := &chserver.Config{}
+	
+	// Setup server and client
+	teardown := simpleSetup(t,
+		serverConfig,
+		&chclient.Config{
+			Remotes: []string{tmpPort + ":$FILEPORT"},
+		})
+	defer teardown()
+
+	// Test that the connection works - if the key is properly set,
+	// the server should start successfully and connections should work
+	result, err := post("http://localhost:"+tmpPort, "env-key-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result != "env-key-test!" {
+		t.Fatalf("expected exclamation mark added, got: %s", result)
+	}
+}
+
+func TestChiselKeyEnvironmentVariableConsistency(t *testing.T) {
+	// This test verifies that the same CHISEL_KEY value produces
+	// consistent behavior (same fingerprint) by manually setting KeySeed
+	keyValue := "consistency-test-key"
+
+	// Create two server instances with the same KeySeed (simulating what main.go does)
+	server1, err := chserver.NewServer(&chserver.Config{
+		KeySeed: keyValue,
+	})
+	if err != nil {
+		t.Fatalf("Failed to create first server: %v", err)
+	}
+
+	server2, err := chserver.NewServer(&chserver.Config{
+		KeySeed: keyValue,
+	})
+	if err != nil {
+		t.Fatalf("Failed to create second server: %v", err)
+	}
+
+	// Both servers should have the same fingerprint since they use the same key
+	if server1.GetFingerprint() != server2.GetFingerprint() {
+		t.Fatalf("Expected same fingerprint for same key, got %s and %s",
+			server1.GetFingerprint(), server2.GetFingerprint())
+	}
+}