iOS開發時一般使用UserDefaults來存取App的配置資訊，但是如果需要儲存一些敏感資訊的話，這時可以考慮使用Keychain來存取。開發時需要注意的是，App卸載後UserDefaults的內容會被刪除，而Keychain裡面的則不會，如果首次將內容寫入Keychain，需要判斷Keychain中是否包含之前沒有刪除乾淨的內容。
Keychain(鑰匙串)是蘋果公司Mac OS中的密碼管理系統，iOS出現後也被引入到iOS中，作為使用者密碼管理的重要工具。使用Keychain對開發人員來說，可以省略掉敏感資訊的加密和解密的過程，交由系統管理。
使用蘋果官方發布的KeychainItemWrapper或者SFHFKeychainUtils很方便。
蘋果已經有現成的類封裝好了keychain,KeychainItemWrapper.h和KeychainItemWrapper.m檔案,可以在GenericKeychain執行個體裡找到。
Keychain的用法也很簡單，蘋果提供了一段範例程式碼裡麵包含了KeychainItemWrapper這個對Keychain操作的封裝工具包。使對Keychain的操作如同NSDictionary一樣簡單
| 代碼如下 |
複製代碼 |
KeychainItemWrapper *keychainItem = [[[KeychainItemWrapper alloc]
initWithIdentifier:@"Identifier"
accessGroup:@"cn.limc.app.boundle"]autorelease];
//擷取keychain中的內容
NSString *value = [keychainItem objectForKey:keyForValue];
//寫入內容到keychain
NSString *valueToWrite = @"value to store";
[keychainItem setObject:valueToWrite forKey:keyForValue]; |
下面就使用keychain來實現存取使用者名稱和密碼。
| 代碼如下 |
複製代碼 |
CHKeychain.h
#import <Foundation/Foundation.h>
#import <Security/Security.h>
@interface CHKeychain : NSObject
+ (void)save:(NSString *)service data:(id)data;
+ (id)load:(NSString *)service;
+ (void)delete:(NSString *)service;
@end
CHKeychain.m
#import "CHKeychain.h"
@implementation CHKeychain
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
return [NSMutableDictionary dictionaryWithObjectsAndKeys:
(id)kSecClassGenericPassword,(id)kSecClass,
service, (id)kSecAttrService,
service, (id)kSecAttrAccount,
(id)kSecAttrAccessibleAfterFirstUnlock,(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((CFDictionaryRef)keychainQuery);
//Add new object to search dictionary(Attention:the data format)
[keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];
//Add item to keychain with the search dictionary
SecItemAdd((CFDictionaryRef)keychainQuery, NULL);
} + (id)load:(NSString *)service {
id ret = nil;
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Configure the search setting
//Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue
[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: %@", service, e);
} @finally {
}
}
if (keyData)
CFRelease(keyData);
return ret;
} + (void)delete:(NSString *)service {
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
SecItemDelete((CFDictionaryRef)keychainQuery);
}
@end
|
首先需要定義幾個字串用來做key：
| 代碼如下 |
複製代碼 |
NSString * const KEY_USERNAME_PASSWORD = @"com.company.app.usernamepassword";
NSString * const KEY_USERNAME = @"com.company.app.username";
NSString * const KEY_PASSWORD = @"com.company.app.password"; |
把使用者名稱和密碼存入keychain：
| 代碼如下 |
複製代碼 |
NSMutableDictionary *usernamepasswordKVPairs = [NSMutableDictionary dictionary];
[usernamepasswordKVPairs setObject:txtfldUsername.text forKey:KEY_USERNAME];
[usernamepasswordKVPairs setObject:txtfldPassword.text forKey:KEY_PASSWORD];
[CHKeychain save:KEY_USERNAME_PASSWORD data:usernamepasswordKVPairs];
|
從keychain中取出使用者名稱和密碼：
| 代碼如下 |
複製代碼 |
NSMutableDictionary *usernamepasswordKVPairs = (NSMutableDictionary *)[CHKeychain load:KEY_USERNAME_PASSWORD];
txtfldUsername.text = [usernamepasswordKVPairs objectForKey:KEY_USERNAME];
txtfldPassword.text = [usernamepasswordKVPairs objectForKey:KEY_PASSWORD]; |
刪除一個keychain item:
| 代碼如下 |
複製代碼 |
[cpp] view plaincopyprint?
01.[CHKeychain delete:KEY_USERNAME_PASSWORD];
[CHKeychain delete:KEY_USERNAME_PASSWORD];
|
這樣一個簡單的使用keychain存取使用者名稱密碼的功能就做好了。
