iOS開發中keychain的使用

通常情況下，我們用NSUserDefaults儲存資料資訊，但是對於一些私密資訊，比如密碼、認證等等，就需要使用更為安全的keychain了。keychain裡儲存的資訊不會因App被刪除而丟失，在使用者重新安裝App後依然有效，資料還在。

使用蘋果官方發布的KeychainItemWrapper或者SFHFKeychainUtils很方便，後來看到 iphone使用keychain來存取使用者名稱和密碼 一文，覺得對瞭解keychain有很大的協助，於是ARC控也嘗試了一把。

需要匯入Security.framework

@implementation WQKeyChain    + (NSMutableDictionary *)getKeychainQuery:(NSString *)service {    return [NSMutableDictionary dictionaryWithObjectsAndKeys:            (__bridge_transfer id)kSecClassGenericPassword,(__bridge_transfer id)kSecClass,            service, (__bridge_transfer id)kSecAttrService,            service, (__bridge_transfer id)kSecAttrAccount,            (__bridge_transfer id)kSecAttrAccessibleAfterFirstUnlock,(__bridge_transfer id)kSecAttrAccessible,            nil];    }            + (void)save:(NSString *)service data:(id)data {        //Get search dictionary        NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];        //Delete old item before add new item        SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);        //Add new object to search dictionary(Attention:the data format)        [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(__bridge_transfer id)kSecValueData];        //Add item to keychain with the search dictionary        SecItemAdd((__bridge_retained CFDictionaryRef)keychainQuery, NULL);    }            + (id)load:(NSString *)service {        id ret = nil;        NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];        //Configure the search setting        [keychainQuery setObject:(id)kCFBooleanTrue forKey:(__bridge_transfer id)kSecReturnData];        [keychainQuery setObject:(__bridge_transfer id)kSecMatchLimitOne forKey:(__bridge_transfer id)kSecMatchLimit];        CFDataRef keyData = NULL;        if (SecItemCopyMatching((__bridge_retained CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {            @try {                ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge_transfer NSData *)keyData];            } @catch (NSException *e) {                NSLog(@"Unarchive of %@ failed: %@", service, e);            } @finally {            }        }        return ret;    }            + (void)delete:(NSString *)service {        NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];        SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);    }    @end