fixing panic when root is symlink (#1429)

* fixing panic when root is symlink
checking root path is a symlink before os.Stat which panics

* fixing formatting

* adding test to verify symlink root path check

* fixing typo

caddyhttp/root/root.go

@@ -28,16 +28,23 @@ func setupRoot(c *caddy.Controller) error {
 			return c.ArgErr()
 		}
 	}
-
-	// Check if root path exists
-	_, err := os.Stat(config.Root)
-	if err != nil {
-		if os.IsNotExist(err) {
-			// Allow this, because the folder might appear later.
-			// But make sure the user knows!
-			log.Printf("[WARNING] Root path does not exist: %s", config.Root)
-		} else {
-			return c.Errf("Unable to access root path '%s': %v", config.Root, err)
+	//first check that the path is not a symlink, os.Stat panics when this is true
+	info, _ := os.Lstat(config.Root)
+	if info != nil && info.Mode()&os.ModeSymlink == os.ModeSymlink {
+		//just print out info, delegate responsibility for symlink validity to
+		//underlying Go framework, no need to test / verify twice
+		log.Printf("[INFO] Root path is symlink: %s", config.Root)
+	} else {
+		// Check if root path exists
+		_, err := os.Stat(config.Root)
+		if err != nil {
+			if os.IsNotExist(err) {
+				// Allow this, because the folder might appear later.
+				// But make sure the user knows!
+				log.Printf("[WARNING] Root path does not exist: %s", config.Root)
+			} else {
+				return c.Errf("Unable to access root path '%s': %v", config.Root, err)
+			}
 		}
 	}
 

caddyhttp/root/root_test.go

@@ -91,7 +91,7 @@ func TestRoot(t *testing.T) {
 	}
 }
 
-// getTempDirPath returnes the path to the system temp directory. If it does not exists - an error is returned.
+// getTempDirPath returns the path to the system temp directory. If it does not exists - an error is returned.
 func getTempDirPath() (string, error) {
 	tempDir := os.TempDir()
 	_, err := os.Stat(tempDir)
@@ -104,3 +104,39 @@ func getTempDirPath() (string, error) {
 func getInaccessiblePath(file string) string {
 	return filepath.Join("C:", "file\x00name") // null byte in filename is not allowed on Windows AND unix
 }
+
+func TestSymlinkRoot(t *testing.T) {
+	origDir, err := ioutil.TempDir("", "root_test")
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to create temp dir for testing! Error was: %v", err)
+	}
+	defer func() {
+		os.Remove(origDir)
+	}()
+
+	tempDir, err := getTempDirPath()
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to find an existing directory for testing! Error was: %v", err)
+	}
+	symlinkDir := filepath.Join(tempDir, "symlink")
+
+	err = os.Symlink(origDir, symlinkDir)
+	if err != nil {
+		if strings.Contains(err.Error(), "A required privilege is not held by the client") {
+			t.Skip("BeforeTest:  A required privilege is not held by the client and is required to create a symlink to run this test.")
+		}
+		t.Fatalf("BeforeTest: Cannot create symlink! Error was: %v", err)
+	}
+	defer func() {
+		os.Remove(symlinkDir)
+	}()
+
+	input := fmt.Sprintf(`root %s`, symlinkDir)
+	c := caddy.NewTestController("http", input)
+	err = setupRoot(c)
+	_ = httpserver.GetConfig(c)
+
+	if err != nil {
+		t.Errorf("Test Symlink Root: Expected no error but found one for input %s. Error was: %v", input, err)
+	}
+}