iOS 钥匙串keychain的应用

问题

目前需要保存一些用户配置，在app删掉后依然能正常读取，那么就用到【钥匙串】

钥匙串简介

项目中有时会需要存储敏感信息（如密码、密钥等），苹果官方提供了一种存储机制--钥匙串（keychain）。
keychain是一种存储在硬盘上的加密的数据库。这个可能是卸载App后，keychain信息还在的原因。
keychain适合存储 较小的数据量（不超过上千字节或上兆字节）的内容。

解决方案

JJKeychain.h

@interface JJKeychain : NSObject

//保存是先删掉之前的key，没有使用update，感觉这样简单；然后保存的value转换为NSData，如果value为自定义object，则需遵循NSSecureCoding协议
+ (BOOL)setValue:(id)value forKey:(NSString *)key;

+ (BOOL)setValue:(id)value forKey:(NSString *)key forAccessGroup:(nullable NSString *)group;


+ (id)valueForKey:(NSString *)key;

+ (id)valueForKey:(NSString *)key forAccessGroup:(nullable NSString *)group;

+ (BOOL)deleteValueForKey:(NSString *)key;

+ (BOOL)deleteValueForKey:(NSString *)key forAccessGroup:(nullable NSString *)group;

+ (NSString *)getBundleSeedIdentifier;

@end

JJKeychain.m

@implementation JJKeychain

+ (NSMutableDictionary *)getKeychainQuery:(NSString *)key forAccessGroup:(NSString *)group{
    NSMutableDictionary *query = @{(__bridge id)kSecClass                   : (__bridge id)kSecClassGenericPassword,
                                          (__bridge id)kSecAttrService      : key,
                                          (__bridge id)kSecAttrAccount      : key,
                                          (__bridge id)kSecAttrAccessible   : (__bridge id)kSecAttrAccessibleAfterFirstUnlock
                                          }.mutableCopy;
    if (group != nil) {
        [query setObject:[self getFullAccessGroup:group] forKey:(__bridge id)kSecAttrAccessGroup];
    }
    
    return query;
}

+ (NSString *)getFullAccessGroup:(NSString *)group
{
    NSString *accessGroup = nil;
    NSString *bundleSeedIdentifier = [self getBundleSeedIdentifier];
    if (bundleSeedIdentifier != nil && [group rangeOfString:bundleSeedIdentifier].location == NSNotFound) {
        accessGroup = [NSString stringWithFormat:@"%@.%@", bundleSeedIdentifier, group];
    }
    return accessGroup;
}

+ (NSString *)getBundleSeedIdentifier
{
    static __strong NSString *bundleSeedIdentifier = nil;
    
    if (bundleSeedIdentifier == nil) {
        @synchronized(self) {
            if (bundleSeedIdentifier == nil) {
                NSString *_bundleSeedIdentifier = nil;
                NSDictionary *query = @{
                                        (__bridge id)kSecClass: (__bridge NSString *)kSecClassGenericPassword,
                                        (__bridge id)kSecAttrAccount: @"bundleSeedID",
                                        (__bridge id)kSecAttrService: @"",
                                        (__bridge id)kSecReturnAttributes: (__bridge id)kCFBooleanTrue
                                        };
                CFDictionaryRef result = nil;
                OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef *)&result);
                if (status == errSecItemNotFound) {
                    status = SecItemAdd((__bridge CFDictionaryRef)query, (CFTypeRef *)&result);
                }
                if (status == errSecSuccess) {
                    NSString *accessGroup = [(__bridge NSDictionary *)result objectForKey:(__bridge NSString *)kSecAttrAccessGroup];
                    NSArray *components = [accessGroup componentsSeparatedByString:@"."];
//                    NSLog(@"components %@",components);
                    _bundleSeedIdentifier = [[components objectEnumerator] nextObject];
                    CFRelease(result);
                }
                if (_bundleSeedIdentifier != nil) {
                    bundleSeedIdentifier = [_bundleSeedIdentifier copy];
                }
            }
        }
    }
    
    return bundleSeedIdentifier;
}

+ (BOOL)setValue:(id)value forKey:(NSString *)key{
    return [self setValue:value forKey:key forAccessGroup:nil];
}

+ (BOOL)setValue:(id)value forKey:(NSString *)key forAccessGroup:(NSString *)group{
    NSMutableDictionary *query = [self getKeychainQuery:key forAccessGroup:group];
    [self deleteValueForKey:key forAccessGroup:group];
    NSData *data = nil;
    @try {
        data = [NSKeyedArchiver archivedDataWithRootObject:value];
    } @catch (NSException *exception) {
        NSLog(@"archived failure value %@  %@",value,exception);
        return NO;
    }
    
    [query setObject:data forKey:(__bridge id)kSecValueData];
    OSStatus result = SecItemAdd((__bridge CFDictionaryRef)query, NULL);
    return result == errSecSuccess;
}

+ (BOOL)deleteValueForKey:(NSString *)key{
    return [self deleteValueForKey:key forAccessGroup:nil];
}

+ (BOOL)deleteValueForKey:(NSString *)key forAccessGroup:(NSString *)group{
    NSMutableDictionary *query = [self getKeychainQuery:key forAccessGroup:group];
    OSStatus result = SecItemDelete((__bridge CFDictionaryRef)query);
    return result == errSecSuccess;
}

+ (id)valueForKey:(NSString *)key{
    return [self valueForKey:key forAccessGroup:nil];
}

+ (id)valueForKey:(NSString *)key forAccessGroup:(NSString *)group{
    id value = nil;
    NSMutableDictionary *query = [self getKeychainQuery:key forAccessGroup:group];
    CFDataRef keyData = NULL;
    [query setObject:(__bridge id)kCFBooleanTrue forKey:(__bridge id)kSecReturnData];
    [query setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];
    if (SecItemCopyMatching((__bridge CFDictionaryRef)query, (CFTypeRef *)&keyData) == errSecSuccess) {
        @try {
            value = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge NSData *)keyData];
        }
        @catch (NSException *e) {
            NSLog(@"Unarchive of %@ failed: %@", key, e);
            value = nil;
        }
        
    }
    
    if (keyData) {
        CFRelease(keyData);
    }
    return value;
}

@end

参考：https://www.jianshu.com/p/354ea1279e68