鍵盤緩存與安全鍵盤

大部分中文應(yīng)用彈出的默認(rèn)鍵盤是簡體中文輸入法鍵盤，在輸入用戶名和密碼的時(shí)候，如果使用簡體中文輸入法鍵盤，輸入英文字符和數(shù)字字符的用戶名和密碼時(shí)，會自動啟動系統(tǒng)輸入法自動更正提示，然后用戶的輸入記錄會被緩存下來。

系統(tǒng)鍵盤緩存最方便拿到的就是利用系統(tǒng)輸入法自動更正的字符串輸入記錄。 緩存文件的地址是：
/private/var/mobile/Library/Keyboard/dynamic-text.dat

導(dǎo)出該緩存文件，查看內(nèi)容，欣喜的發(fā)現(xiàn)一切輸入記錄都是明文存儲的。因?yàn)橄到y(tǒng)不會把所有的用戶輸入記錄都當(dāng)作密碼等敏感信息來處理。 一般情況下，一個(gè)常規(guī) iPhone 用戶的 dynamic-text.dat 文件，高頻率出現(xiàn)的字符串就是用戶名和密碼。

所以，一般銀行客戶端 app 輸入密碼時(shí)都不使用系統(tǒng)鍵盤，而使用自己定制的鍵盤，原因主要有 2 個(gè)：

1）避免第三方讀取系統(tǒng)鍵盤緩存

2）防止屏幕錄制 （自己定制的鍵盤按鍵不加按下效果）

那么，如何實(shí)現(xiàn)自定義安全鍵盤呢？大致思路如下：

1）首先捕獲系統(tǒng)鍵盤的彈出、收回通知
2）創(chuàng)建一個(gè)更高級別的 window 擋住系統(tǒng)鍵盤
3）需要拋出一個(gè) idtextInput 的弱引用切換焦點(diǎn)

下面給出一個(gè)簡單的安全鍵盤模型：

@interface WQSafeKeyboard : UIWindow  

@property (nonatomic, weak, setter = focusOnTextFiled:) UITextField *textFiled;  
+ (WQSafeKeyboard *)deploySafeKeyboard;  
@end  

@interface WQSafeKeyboard()  

@property (nonatomic, strong)WQInterKeyboard *keyboard;  
@end  

@implementation WQSafeKeyboard  

+ (WQSafeKeyboard *)deploySafeKeyboard  
{  
    WQSafeKeyboard *kb = [[WQSafeKeyboard alloc]init];  
    [kb addObserver];  
    return kb;  
}  

- (instancetype)init  
{  
    if (self = [super init]) {  
        self.windowLevel = UIWindowLevelAlert;  
        self.frame = CGRectZero;  
        self.rootViewController = self.keyboard;  
    }  
    return self;  
}  

- (void)dealloc  
{  
    [[NSNotificationCenter defaultCenter] removeObserver:self];  
}  

- (WQInterKeyboard *)keyboard  
{  
    if (!_keyboard) {  
        _keyboard = [[WQInterKeyboard alloc]init];  
    }  
    return _keyboard;  
}  

- (void)focusOnTextFiled:(UITextField *)textFiled  
{  
    _textFiled = textFiled;  
    self.keyboard.textField = _textFiled;  
}  

- (void)addObserver  
{  
    [[NSNotificationCenter defaultCenter]addObserver:self  
                                            selector:@selector(keyboardWillShow:)  
                                                name:UIKeyboardWillShowNotification  
                                              object:nil];  
    [[NSNotificationCenter defaultCenter]addObserver:self  
                                            selector:@selector(keyboardWillHide:)  
                                                name:UIKeyboardWillHideNotification  
                                              object:nil];  
}  

- (void)keyboardWillShow:(NSNotification *)notification  
{  
    if (![self.textFiled isFirstResponder]) {  
        return;  
    }  
    [self keyboardAnimationWithNotification:notification];  
}  

- (void)keyboardWillHide:(NSNotification *)notification  
{  
    if (![self.textFiled isFirstResponder]) {  
        return;  
    }  
    [self keyboardAnimationWithNotification:notification];  
}  

- (void)keyboardAnimationWithNotification:(NSNotification *)notification  
{  
    [self makeKeyAndVisible];  
    NSDictionary *userInfo = [notification userInfo];  
    CGRect kbFrame_end,kbFrame_begin;  
    NSTimeInterval animationDuration;  
    UIViewAnimationCurve animationCurve;  
    [userInfo[UIKeyboardFrameEndUserInfoKey] getValue:&kbFrame_end];  
    [userInfo[UIKeyboardFrameBeginUserInfoKey] getValue:&kbFrame_begin];  
    [userInfo[UIKeyboardAnimationCurveUserInfoKey] getValue:&animationCurve];  
    [userInfo[UIKeyboardAnimationDurationUserInfoKey] getValue:&animationDuration];  

    self.frame = [self resizeFrameToAdjust:kbFrame_begin];  
    [UIView animateWithDuration:animationDuration  
                          delay:0  
                        options:(animationCurve<<16)  
                     animations:^{  
                         self.frame = [self resizeFrameToAdjust:kbFrame_end];  
                     }completion:^(BOOL finished) {  

                     }];  
    if ([notification.name isEqualToString:UIKeyboardWillHideNotification]) {  
        [self resignKeyWindow];  
    }  
}  

- (CGRect)resizeFrameToAdjust:(CGRect)frame  
{  
    if ([[UIApplication sharedApplication] isStatusBarHidden] )  
        return frame;  

    if (SYSTEM_VERSION_LESS_THAN(@"7.0")) {  
        frame = CGRectMake(frame.origin.x,  
                           frame.origin.y - STATUSBAR_HEIGHT,  
                           frame.size.width,  
                           frame.size.height);  
    }  
    return frame;  
}  

@end