In modern applications, data security is a top priority, especially when sensitive information may be copied or transferred to external applications. By preventing certain actions like "cut," "copy," and "paste" on text fields within iOS apps, we can safeguard text data, ensuring it remains within a trusted group of applications. This article demonstrates how to achieve this protection using Swift, while maintaining full control over text-related operations.
Our approach centers around the TextActionInterceptor class, which "swizzles" standard text-related methods, replacing them with secure alternatives. This class intercepts and overrides the "copy," "paste," and "cut" methods, with an option to enable or disable swizzling dynamically.
Let’s go through key code segments that bring this functionality to life.
class TextActionInterceptor {
enum TextAction: String {
case cut
case copy
case paste
case define
case translate
case modify
case update
case previewItem
}
struct SavedTextAction {
var methodRef: Method
var originalImplementation: IMP
var selector: Selector
}
private var isSwizzled = false
var savedActions: [TextAction: SavedTextAction] = [:]
// Method to intercept the "copy" action
func interceptCopy(_ sender: Any?) {
guard
let inputField = retrieveTextInput(sender),
let range = inputField.selectedTextRange,
let text = inputField.text(in: range)
else { return }
SecureClipboard.shared.contents = text
}
// Similar methods for "cut" and "paste"
func interceptPaste(_ sender: Any?) {
guard
let inputField = retrieveTextInput(sender),
let range = inputField.selectedTextRange,
let text = SecureClipboard.shared.contents
else { return }
inputField.replace(range, withText: text)
}
func interceptCut(_ sender: Any?) {
guard
let inputField = retrieveTextInput(sender),
let range = inputField.selectedTextRange,
let cutText = inputField.text(in: range)
else { return }
SecureClipboard.shared.contents = cutText
inputField.replace(range, withText: "")
}
// Method to enable or disable swizzling
func toggleSwizzling(_ enable: Bool) {
guard enable != isSwizzled else { return }
isSwizzled = enable
savedActions.forEach { (_, action) in
let swizzledMethod = class_getInstanceMethod(
object_getClass(self),
action.selector
)
guard enable else {
method_setImplementation(action.methodRef, action.originalImplementation)
return
}
method_exchangeImplementations(action.methodRef, swizzledMethod!)
}
}
}
The SecureClipboard class is responsible for managing text stored in the clipboard. It blocks any attempt to share text data externally, ensuring it stays within the app's defined ecosystem.
final class SecureClipboard {
static let restrictedTextPlaceholder = "Access Restricted"
static var shared = SecureClipboard()
private let placeholderItem: [String: String]
private var clipboard: UIPasteboard
private(set) var internalBuffer: String?
init() {
placeholderItem = ["public.utf8-plain-text": SecureClipboard.restrictedTextPlaceholder]
clipboard = UIPasteboard.general
}
var contents: String? {
get {
guard
let clipboardText = clipboard.string,
clipboardText != SecureClipboard.restrictedTextPlaceholder
else { return internalBuffer }
return clipboardText
}
set {
guard let newText = newValue else {
internalBuffer = nil
return
}
clipboard.items = [placeholderItem]
internalBuffer = newText.isEmpty ? nil : newText
}
}
}
Applying this approach achieves multiple levels of data security:
Access Control: All text operations are managed within the application, preventing potential data leaks.
Safe Data Storage: Text data is accessible only within a controlled application group.
Flexible configuration: The ability to enable and disable swizzling allows flexible control of data security based on conditions.
By using swizzling and an internal clipboard, we ensure a high level of data protection in iOS applications. This approach offers a robust solution for maintaining text security across applications in a defined environment.