iOS之数据安全

一、数据安全

术语-----

密钥:密钥是一种参数, 它是在明文转换为密文, 或将密文转换为明文的算法中输入的参数. 密钥分为对称密钥和非对称密钥(也可以根据用途来分为加密密钥和解密密钥)

明文:没有进行加密, 能够直接代表原文含义的信息

密文:经过加密处理之后, 隐藏原文含义的信息

加密:将明文转换成密文的实施过程

解密:将密文转换成明文的实施过程

数据安全-----

数据安全: 是一种主动的包含措施, 数据本身的安全必须基于可靠的加密算法与安全体系,主要是有对称算法与公开密钥密码体系两种(非对称算法), 都包含了数据的加密和解密过程

二、MD5

哈希算法-----

哈希算法:哈希算法将任意长度的二进制值映射为较短的固定长度的二进制值, 这个小的二进制值成为哈希值

哈希值是一段数据唯一且及其紧凑的数值表示形式. 数据的哈希值可以检验数据的完整性. 一般用于快速查找和加密算法

典型的哈希算法就有MD5

MD5-----

MD5:Message Digest Alogorithm MD5 (消息摘要算法第五版) 为计算机安全领域广泛使用的一种散列函数, 用以提供小米的完整性保护MD5算法具有以下特点:

1、压缩性: 任意长度的数据, 算出的MD5值长度都是固定的 (16进制, 32位)

2、容易计算: 从原数据计算出MD5值很容易

3、抗修改性: 对原数据进行任何改动, 哪怕只修改1个字节, 所得到的MD5值都有很大区别

4、强抗碰撞: 已知原数据和其MD5值, 想找到一个具有相同MD5值的数据(伪造数据)是非常困难的

获取字符串MD5值-----引入头文件

#import <CommonCrypto/CommonCrypto.h>

//1.准备一个字符串用于加密
    NSString *str = @"go ahead";//同一个字符串进行MD5加密出来的内容相同
#pragma mark - ??????????????一个内容加了const有什么含义
    //2.因为MD5基于C语言, 所以需要将字符串转为C语言的字符串进行编码
    const char *data = [str UTF8String];
    
    //3.使用字符串数组去存取加密后相关的内容(16进制, 32位)
    //CC_MD5_DIGEST_LENGTH表示长度
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    
    //4.进行MD5加密
    //参数1: 要加密的内容
    //参数2: 要加密的data的一个长度
    //参数3: MD5
    CC_MD5(data, (CC_LONG)strlen(data), result);
    
    //5.创建可变字符串, 保存结果
    NSMutableString *mutableString = [NSMutableString string];
    
    //6.遍历结果数组, 然后添加到可变字符串中
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        
        //16进制                     //%x 16进制, 02不足两位时补0.
        [mutableString appendFormat:@"%02x", result[i]];
    }
    NSLog(@"%@", mutableString);

 获取其他对象MD5的值-----

 加密NSData

#pragma mark - 加密NSData
    
    //需求: 创建一个数组, 数组中存储元素, 将这个数组写入到沙盒里
    
    //1.创建一个数组
    NSArray *array = @[@"go", @"rose"];
    //2.找沙盒路径
    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    
    //3.拼接路径
    NSString *arrayPath = [documentPath stringByAppendingPathComponent:@"array.plist"];
    
    //4.写入
    [array writeToFile:arrayPath atomically:YES];
    
    //从沙盒中取出NSData类型的数据
    NSData *data = [NSData dataWithContentsOfFile:arrayPath];
    
    NSLog(@"%@", data);
    
    //NSData类型数据加密过程
    
    //1.创建MD5对象
    CC_MD5_CTX md5;
    
    //2.初始化MD5对象
    CC_MD5_Init(&md5);
    
    //3.准备开始进行数据的加密
    CC_MD5_Update(&md5, data.bytes, (CC_LONG)data.length);
    
    //4.准备一个字符串数组用来存储结果
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    
    //5.创建一个可变字符串保存结果
    NSMutableString *string = [NSMutableString string];
    //结束加密
    CC_MD5_Final(result, &md5);
    //6.遍历数组给可变字符串赋值
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        [string appendFormat:@"%02x", result[i]];
    }
    NSLog(@"%@", string);

 钥匙串加密-----

 苹果iOS和Mac OS X系统自带了一套敏感信息保存方案: "钥匙串"(Keychain)

 保存在钥匙串的内容相当于系统对其做了保护, 在设备锁定时进行了加密处理

 钥匙串中的条目成为SecItem, 但它是存储在CFDictionary中的 SecItemRef类型并不存在, SecItem有五类:通用密码、互联网密码、证书、密钥、和身份, 在大多数情况下, 我们用到的都是通用密码

 钥匙串的使用和字典非常相似

 用原生的 Security.framework就可以实现钥匙串的访问、续写, 但是只能在真机上进行, 通常我们使用KeychainItemWrapper来完成钥匙串的加密

引入头文件 

#import "KeychainItemWrapper.h"

/*
     File: KeychainItemWrapper.h
 Abstract: 
 Objective-C wrapper for accessing a single keychain item.
 
  Version: 1.2
 
 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple
 Inc. ("Apple") in consideration of your agreement to the following
 terms, and your use, installation, modification or redistribution of
 this Apple software constitutes acceptance of these terms.  If you do
 not agree with these terms, please do not use, install, modify or
 redistribute this Apple software.
 
 In consideration of your agreement to abide by the following terms, and
 subject to these terms, Apple grants you a personal, non-exclusive
 license, under Apple's copyrights in this original Apple software (the
 "Apple Software"), to use, reproduce, modify and redistribute the Apple
 Software, with or without modifications, in source and/or binary forms;
 provided that if you redistribute the Apple Software in its entirety and
 without modifications, you must retain this notice and the following
 text and disclaimers in all such redistributions of the Apple Software.
 Neither the name, trademarks, service marks or logos of Apple Inc. may
 be used to endorse or promote products derived from the Apple Software
 without specific prior written permission from Apple.  Except as
 expressly stated in this notice, no other rights or licenses, express or
 implied, are granted by Apple herein, including but not limited to any
 patent rights that may be infringed by your derivative works or by other
 works in which the Apple Software may be incorporated.
 
 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
 
 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL
 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,
 MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED
 AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),
 STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 
 Copyright (C) 2010 Apple Inc. All Rights Reserved.
 
*/

#import <UIKit/UIKit.h>

/*
    The KeychainItemWrapper class is an abstraction layer for the iPhone Keychain communication. It is merely a 
    simple wrapper to provide a distinct barrier between all the idiosyncracies involved with the Keychain
    CF/NS container objects.
*/
@interface KeychainItemWrapper : NSObject
{
    NSMutableDictionary *keychainItemData;        // The actual keychain item data backing store.
    NSMutableDictionary *genericPasswordQuery;    // A placeholder for the generic keychain item query used to locate the item.
}

@property (nonatomic, retain) NSMutableDictionary *keychainItemData;
@property (nonatomic, retain) NSMutableDictionary *genericPasswordQuery;

// Designated initializer.
- (id)initWithIdentifier: (NSString *)identifier accessGroup:(NSString *) accessGroup;
- (void)setObject:(id)inObject forKey:(id)key;
- (id)objectForKey:(id)key;

// Initializes and resets the default generic keychain item data.
- (void)resetKeychainItem;

@end

/*
     File: KeychainItemWrapper.m 
 Abstract: 
 Objective-C wrapper for accessing a single keychain item.
  
  Version: 1.2 
  
 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple 
 Inc. ("Apple") in consideration of your agreement to the following 
 terms, and your use, installation, modification or redistribution of 
 this Apple software constitutes acceptance of these terms.  If you do 
 not agree with these terms, please do not use, install, modify or 
 redistribute this Apple software. 
  
 In consideration of your agreement to abide by the following terms, and 
 subject to these terms, Apple grants you a personal, non-exclusive 
 license, under Apple's copyrights in this original Apple software (the 
 "Apple Software"), to use, reproduce, modify and redistribute the Apple 
 Software, with or without modifications, in source and/or binary forms; 
 provided that if you redistribute the Apple Software in its entirety and 
 without modifications, you must retain this notice and the following 
 text and disclaimers in all such redistributions of the Apple Software. 
 Neither the name, trademarks, service marks or logos of Apple Inc. may 
 be used to endorse or promote products derived from the Apple Software 
 without specific prior written permission from Apple.  Except as 
 expressly stated in this notice, no other rights or licenses, express or 
 implied, are granted by Apple herein, including but not limited to any 
 patent rights that may be infringed by your derivative works or by other 
 works in which the Apple Software may be incorporated. 
  
 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE 
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION 
 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS 
 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND 
 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS. 
  
 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL 
 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, 
 MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED 
 AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE), 
 STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE 
 POSSIBILITY OF SUCH DAMAGE. 
  
 Copyright (C) 2010 Apple Inc. All Rights Reserved. 
  
*/ 

#import "KeychainItemWrapper.h"
#import <Security/Security.h>

/*

These are the default constants and their respective types,
available for the kSecClassGenericPassword Keychain Item class:

kSecAttrAccessGroup            -        CFStringRef
kSecAttrCreationDate        -        CFDateRef
kSecAttrModificationDate    -        CFDateRef
kSecAttrDescription            -        CFStringRef
kSecAttrComment                -        CFStringRef
kSecAttrCreator                -        CFNumberRef
kSecAttrType                -        CFNumberRef
kSecAttrLabel                -        CFStringRef
kSecAttrIsInvisible            -        CFBooleanRef
kSecAttrIsNegative            -        CFBooleanRef
kSecAttrAccount                -        CFStringRef
kSecAttrService                -        CFStringRef
kSecAttrGeneric                -        CFDataRef
 
See the header file Security/SecItem.h for more details.

*/

@interface KeychainItemWrapper (PrivateMethods)
/*
The decision behind the following two methods (secItemFormatToDictionary and dictionaryToSecItemFormat) was
to encapsulate the transition between what the detail view controller was expecting (NSString *) and what the
Keychain API expects as a validly constructed container class.
*/
- (NSMutableDictionary *)secItemFormatToDictionary:(NSDictionary *)dictionaryToConvert;
- (NSMutableDictionary *)dictionaryToSecItemFormat:(NSDictionary *)dictionaryToConvert;

// Updates the item in the keychain, or adds it if it doesn't exist.
- (void)writeToKeychain;

@end

@implementation KeychainItemWrapper

@synthesize keychainItemData, genericPasswordQuery;

- (id)initWithIdentifier: (NSString *)identifier accessGroup:(NSString *) accessGroup;
{
    if (self = [super init])
    {
        // Begin Keychain search setup. The genericPasswordQuery leverages the special user
        // defined attribute kSecAttrGeneric to distinguish itself between other generic Keychain
        // items which may be included by the same application.
        genericPasswordQuery = [[NSMutableDictionary alloc] init];
        
        [genericPasswordQuery setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
        [genericPasswordQuery setObject:identifier forKey:(id)kSecAttrGeneric];
        
        // The keychain access group attribute determines if this item can be shared
        // amongst multiple apps whose code signing entitlements contain the same keychain access group.
        if (accessGroup != nil)
        {
#if TARGET_IPHONE_SIMULATOR
            // Ignore the access group if running on the iPhone simulator.
            // 
            // Apps that are built for the simulator aren't signed, so there's no keychain access group
            // for the simulator to check. This means that all apps can see all keychain items when run
            // on the simulator.
            //
            // If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
            // simulator will return -25243 (errSecNoAccessForItem).
#else            
            [genericPasswordQuery setObject:accessGroup forKey:(id)kSecAttrAccessGroup];
#endif
        }
        
        // Use the proper search constants, return only the attributes of the first match.
        [genericPasswordQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
        [genericPasswordQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnAttributes];
        
        NSDictionary *tempQuery = [NSDictionary dictionaryWithDictionary:genericPasswordQuery];
        
        NSMutableDictionary *outDictionary = nil;
        
        if (! SecItemCopyMatching((CFDictionaryRef)tempQuery, (CFTypeRef *)&outDictionary) == noErr)
        {
            // Stick these default values into keychain item if nothing found.
            [self resetKeychainItem];
            
            // Add the generic attribute and the keychain access group.
            [keychainItemData setObject:identifier forKey:(id)kSecAttrGeneric];
            if (accessGroup != nil)
            {
#if TARGET_IPHONE_SIMULATOR
                // Ignore the access group if running on the iPhone simulator.
                // 
                // Apps that are built for the simulator aren't signed, so there's no keychain access group
                // for the simulator to check. This means that all apps can see all keychain items when run
                // on the simulator.
                //
                // If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
                // simulator will return -25243 (errSecNoAccessForItem).
#else            
                [keychainItemData setObject:accessGroup forKey:(id)kSecAttrAccessGroup];
#endif
            }
        }
        else
        {
            // load the saved data from Keychain.
            self.keychainItemData = [self secItemFormatToDictionary:outDictionary];
        }
       
        [outDictionary release];
    }
    
    return self;
}

- (void)dealloc
{
    [keychainItemData release];
    [genericPasswordQuery release];
    
    [super dealloc];
}

- (void)setObject:(id)inObject forKey:(id)key 
{
    if (inObject == nil) return;
    id currentObject = [keychainItemData objectForKey:key];
    if (![currentObject isEqual:inObject])
    {
        [keychainItemData setObject:inObject forKey:key];
        [self writeToKeychain];
    }
}

- (id)objectForKey:(id)key
{
    return [keychainItemData objectForKey:key];
}

- (void)resetKeychainItem
{
    OSStatus junk = noErr;
    if (!keychainItemData) 
    {
        self.keychainItemData = [[NSMutableDictionary alloc] init];
    }
    else if (keychainItemData)
    {
        NSMutableDictionary *tempDictionary = [self dictionaryToSecItemFormat:keychainItemData];
        junk = SecItemDelete((CFDictionaryRef)tempDictionary);
        NSAssert( junk == noErr || junk == errSecItemNotFound, @"Problem deleting current dictionary." );
    }
    
    // Default attributes for keychain item.
    [keychainItemData setObject:@"" forKey:(id)kSecAttrAccount];
    [keychainItemData setObject:@"" forKey:(id)kSecAttrLabel];
    [keychainItemData setObject:@"" forKey:(id)kSecAttrDescription];
    
    // Default data for keychain item.
    [keychainItemData setObject:@"" forKey:(id)kSecValueData];
}

- (NSMutableDictionary *)dictionaryToSecItemFormat:(NSDictionary *)dictionaryToConvert
{
    // The assumption is that this method will be called with a properly populated dictionary
    // containing all the right key/value pairs for a SecItem.
    
    // Create a dictionary to return populated with the attributes and data.
    NSMutableDictionary *returnDictionary = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
    
    // Add the Generic Password keychain item class attribute.
    [returnDictionary setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
    
    // Convert the NSString to NSData to meet the requirements for the value type kSecValueData.
    // This is where to store sensitive data that should be encrypted.
    NSString *passwordString = [dictionaryToConvert objectForKey:(id)kSecValueData];
    [returnDictionary setObject:[passwordString dataUsingEncoding:NSUTF8StringEncoding] forKey:(id)kSecValueData];
    
    return returnDictionary;
}

- (NSMutableDictionary *)secItemFormatToDictionary:(NSDictionary *)dictionaryToConvert
{
    // The assumption is that this method will be called with a properly populated dictionary
    // containing all the right key/value pairs for the UI element.
    
    // Create a dictionary to return populated with the attributes and data.
    NSMutableDictionary *returnDictionary = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
    
    // Add the proper search key and class attribute.
    [returnDictionary setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
    [returnDictionary setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
    
    // Acquire the password data from the attributes.
    NSData *passwordData = NULL;
    if (SecItemCopyMatching((CFDictionaryRef)returnDictionary, (CFTypeRef *)&passwordData) == noErr)
    {
        // Remove the search, class, and identifier key/value, we don't need them anymore.
        [returnDictionary removeObjectForKey:(id)kSecReturnData];
        
        // Add the password to the dictionary, converting from NSData to NSString.
        NSString *password = [[[NSString alloc] initWithBytes:[passwordData bytes] length:[passwordData length] 
                                                     encoding:NSUTF8StringEncoding] autorelease];
        [returnDictionary setObject:password forKey:(id)kSecValueData];
    }
    else
    {
        // Don't do anything if nothing is found.
        NSAssert(NO, @"Serious error, no matching item found in the keychain.
");
    }
    
    [passwordData release];
   
    return returnDictionary;
}

- (void)writeToKeychain
{
    NSDictionary *attributes = NULL;
    NSMutableDictionary *updateItem = NULL;
    OSStatus result;
    
    if (SecItemCopyMatching((CFDictionaryRef)genericPasswordQuery, (CFTypeRef *)&attributes) == noErr)
    {
        // First we need the attributes from the Keychain.
        updateItem = [NSMutableDictionary dictionaryWithDictionary:attributes];
        // Second we need to add the appropriate search key/values.
        [updateItem setObject:[genericPasswordQuery objectForKey:(id)kSecClass] forKey:(id)kSecClass];
        
        // Lastly, we need to set up the updated attribute list being careful to remove the class.
        NSMutableDictionary *tempCheck = [self dictionaryToSecItemFormat:keychainItemData];
        [tempCheck removeObjectForKey:(id)kSecClass];
        
#if TARGET_IPHONE_SIMULATOR
        // Remove the access group if running on the iPhone simulator.
        // 
        // Apps that are built for the simulator aren't signed, so there's no keychain access group
        // for the simulator to check. This means that all apps can see all keychain items when run
        // on the simulator.
        //
        // If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
        // simulator will return -25243 (errSecNoAccessForItem).
        //
        // The access group attribute will be included in items returned by SecItemCopyMatching,
        // which is why we need to remove it before updating the item.
        [tempCheck removeObjectForKey:(id)kSecAttrAccessGroup];
#endif
        
        // An implicit assumption is that you can only update a single item at a time.
        
        result = SecItemUpdate((CFDictionaryRef)updateItem, (CFDictionaryRef)tempCheck);
        NSAssert( result == noErr, @"Couldn't update the Keychain Item." );
    }
    else
    {
        // No previous item found; add the new one.
        result = SecItemAdd((CFDictionaryRef)[self dictionaryToSecItemFormat:keychainItemData], NULL);
        NSAssert( result == noErr, @"Couldn't add the Keychain Item." );
    }
}

@end

//1.创建钥匙串对象
    //参数1: 标识, 用于识别将要加密的内容(回传标识符)
    //参数2: 分组 一般为nil
    KeychainItemWrapper *keychainItem = [[KeychainItemWrapper alloc]initWithIdentifier:@"myItemWrapper" accessGroup:nil];
    
    //常用于加密用户名和密码
    //系统提供键值对中的两个键, 非系统的键是没法添加到字典中的
    
    id kUserName = (__bridge id)kSecAttrAccount;
    id kUserPassword = (__bridge id)kSecValueData;
    
    [keychainItem setObject:@"MBBoy" forKey:kUserName];
    [keychainItem setObject:@"123456" forKey:kUserPassword];
    
    //从keychain中获取存储的数据
    //用户名
    NSString *userName = [keychainItem objectForKey:kUserName];
    //密码
    NSString *password = [keychainItem objectForKey:kUserPassword];

 KVO加密-----

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //初始化
    self.array = [NSMutableArray array];
    
    //第一步: 注册观察者
    //参数1: 添加的观察者对象
    //参数2: 字符串标识的key
    //参数3: 什么时候会触发观察者对象
    //参数4: 文本内容 一般为nil
    
    
    
    [self addObserver:self forKeyPath:@"array" options:NSKeyValueObservingOptionNew context:nil];
    
}

//第二步: 实现回调方法
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {
    
    NSLog(@"keyPath = %@", keyPath);
    NSLog(@"object = %@", object);
    NSLog(@"change = %@", change);
    
    //可以进行刷新UI的操作
    
}

//视图将要消失的时候
- (void)viewWillDisappear:(BOOL)animated {
    
    //在不要需要观察者的时候需要把它给干掉
    [self removeObserver:self forKeyPath:@"array"];
    
}

//第三步: 触发可变数组进行改变
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    
    NSArray *subArray = @[@"1", @"2", @"3"];
    
    //根据keyPath获取到可变数组对象设置数据
    [[self mutableArrayValueForKeyPath:@"array"] setArray:subArray];
}