iOS密码保存（keychain简单使用）

iOS中保存密码，如果要追求安全性，那么使用苹果自带的Keychain Services无疑是最佳选择。如果要在程序中使用Keychain Services，首先要添加Security.framework。

Keychain Services提供了一系列api用以存取和更新keychain item：

SecItemAdd（添加）

SecItemUpdate（更新）

SecItemCopyMatching（查找）

SecItemDelete（删除）

这些方法直接使用有点麻烦，需要进行面向对象的封装。我写了一个简单的例子，只是用来保存用户名和密码，以实现记住密码这项功能。

下面贴一部分代码，完整项目下载：https://github.com/tenric/KeyChainDemo

MyKeyChainHelper.h

#import <Foundation/Foundation.h>

@interface MyKeyChainHelper : NSObject

+ (void) saveUserName:(NSString*)userName 
      userNameService:(NSString*)userNameService 
             psaaword:(NSString*)pwd 
      psaawordService:(NSString*)pwdService;

+ (void) deleteWithUserNameService:(NSString*)userNameService 
                   psaawordService:(NSString*)pwdService;

+ (NSString*) getUserNameWithService:(NSString*)userNameService;

+ (NSString*) getPasswordWithService:(NSString*)pwdService;

@end

MyKeyChainHelper.m

#import "MyKeyChainHelper.h"

@implementation MyKeyChainHelper

+ (NSMutableDictionary *)getKeyChainQuery:(NSString *)service {  
    return [NSMutableDictionary dictionaryWithObjectsAndKeys:  
            (id)kSecClassGenericPassword,(id)kSecClass,  
            service, (id)kSecAttrService,  
            service, (id)kSecAttrAccount,  
            (id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible,  
            nil];  
}  

+ (void) saveUserName:(NSString*)userName 
      userNameService:(NSString*)userNameService 
             psaaword:(NSString*)pwd 
      psaawordService:(NSString*)pwdService
{
    NSMutableDictionary *keychainQuery = [self getKeyChainQuery:userNameService];  
    SecItemDelete((CFDictionaryRef)keychainQuery);  
    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:userName] forKey:(id)kSecValueData];  
    SecItemAdd((CFDictionaryRef)keychainQuery, NULL); 
    
    keychainQuery = [self getKeyChainQuery:pwdService];  
    SecItemDelete((CFDictionaryRef)keychainQuery);  
    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:pwd] forKey:(id)kSecValueData];  
    SecItemAdd((CFDictionaryRef)keychainQuery, NULL); 
}

+ (void) deleteWithUserNameService:(NSString*)userNameService 
                   psaawordService:(NSString*)pwdService
{
    NSMutableDictionary *keychainQuery = [self getKeyChainQuery:userNameService];  
    SecItemDelete((CFDictionaryRef)keychainQuery); 
    
    keychainQuery = [self getKeyChainQuery:pwdService];  
    SecItemDelete((CFDictionaryRef)keychainQuery); 
}

+ (NSString*) getUserNameWithService:(NSString*)userNameService
{
    NSString* ret = nil;  
    NSMutableDictionary *keychainQuery = [self getKeyChainQuery:userNameService];  
    [keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];  
    [keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];  
    CFDataRef keyData = NULL;  
    if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) 
    {  
        @try 
        {  
            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(NSData *)keyData];  
        } 
        @catch (NSException *e) 
        {  
            NSLog(@"Unarchive of %@ failed: %@", userNameService, e);  
        }
        @finally 
        {  
        }  
    }  
    if (keyData)   
        CFRelease(keyData);  
    return ret; 
}

+ (NSString*) getPasswordWithService:(NSString*)pwdService
{
    NSString* ret = nil;  
    NSMutableDictionary *keychainQuery = [self getKeyChainQuery:pwdService];  
    [keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];  
    [keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];  
    CFDataRef keyData = NULL;  
    if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) 
    {  
        @try 
        {  
            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(NSData *)keyData];  
        } 
        @catch (NSException *e) 
        {  
            NSLog(@"Unarchive of %@ failed: %@", pwdService, e);  
        }
        @finally 
        {  
        }  
    }  
    if (keyData)   
        CFRelease(keyData);  
    return ret;
}
@end