Keychain Add Update Remove and Find operations using one file.

#import <Foundation/Foundation.h>
typedef void (^KeychainOperationBlock)(BOOL successfulOperation, NSData *data, OSStatus status);

@interface Keychain : NSObject

-(id) initWithService:(NSString *) service_ withGroup:(NSString*)group_;

-(void)insertKey:(NSString *)key withData:(NSData *)data withCompletion:(KeychainOperationBlock)completionBlock;
-(void)updateKey:(NSString*)key withData:(NSData*) data withCompletion:(KeychainOperationBlock)completionBlock;
-(void)removeDataForKey:(NSString*)key withCompletionBlock:(KeychainOperationBlock)completionBlock;
-(void)findDataForKey:(NSString*)key withCompletionBlock:(KeychainOperationBlock)completionBlock;

@end

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

@implementation Keychain

{
   NSString * keychainService;
   NSString * keychainGroup;
}

-(id) initWithService:(NSString *)service withGroup:(NSString*)group
{
   self =[super init];
   if(self) {
       keychainService = [NSString stringWithString:service];
       if(group) {
           keychainGroup = [NSString stringWithString:group];
       }
   }
   
   return  self;
}

-(void)insertKey:(NSString *)key
       withData:(NSData *)data
 withCompletion:(KeychainOperationBlock)completionBlock
{
   NSMutableDictionary * dict =[self prepareDict:key];
   [dict setObject:data forKey:(__bridge id)kSecValueData];
   [dict setObject:keychainService forKey:(id)kSecAttrService];
   
   OSStatus status = SecItemAdd((__bridge CFDictionaryRef)dict, NULL);
   if(errSecSuccess != status) {
       DLog(@"Unable add item with key =%@ error:%d",key,(int)status);
       if (completionBlock) {
           completionBlock(errSecSuccess == status, nil, status);
       }
   }
   if (status == errSecDuplicateItem) {
       [self updateKey:key withData:data withCompletion:^(BOOL successfulOperation, NSData *updateData, OSStatus updateStatus) {
           if (completionBlock) {
               completionBlock(successfulOperation, updateData, updateStatus);
           }
           DLog(@"Found duplication item -- updating key with data");
       }];
   }
}

-(void)findDataForKey:(NSString *)key
 withCompletionBlock:(KeychainOperationBlock)completionBlock
{
   NSMutableDictionary *dict = [self prepareDict:key];
   [dict setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];
   [dict setObject:keychainService forKey:(id)kSecAttrService];
   [dict setObject:(id)kCFBooleanTrue forKey:(__bridge id)kSecReturnData];
   CFTypeRef result = NULL;
   OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)dict,&result);
   
   if( status != errSecSuccess) {
       DLog(@"Unable to fetch item for key %@ with error:%d",key,(int)status);
       if (completionBlock) {
           completionBlock(errSecSuccess == status, nil, status);
       }
   } else {
       if (completionBlock) {
           completionBlock(errSecSuccess == status, (__bridge NSData *)result, status);
       }
   }
}

-(void)updateKey:(NSString *)key
       withData:(NSData *)data
 withCompletion:(KeychainOperationBlock)completionBlock
{
   NSMutableDictionary * dictKey =[self prepareDict:key];
   
   NSMutableDictionary * dictUpdate =[[NSMutableDictionary alloc] init];
   [dictUpdate setObject:data forKey:(__bridge id)kSecValueData];
   [dictUpdate setObject:keychainService forKey:(id)kSecAttrService];
   OSStatus status = SecItemUpdate((__bridge CFDictionaryRef)dictKey, (__bridge CFDictionaryRef)dictUpdate);
   if( status != errSecSuccess) {
       DLog(@"Unable to remove item for key %@ with error:%d",key,(int)status);
   }
   if (completionBlock) {
       completionBlock(errSecSuccess == status, nil, status);
   }
}

-(void)removeDataForKey:(NSString *)key
   withCompletionBlock:(KeychainOperationBlock)completionBlock {
   NSMutableDictionary *dict = [self prepareDict:key];
   OSStatus status = SecItemDelete((__bridge CFDictionaryRef)dict);
   if( status != errSecSuccess) {
       DLog(@"Unable to remove item for key %@ with error:%d",key,(int)status);
   }
   if (completionBlock) {
       completionBlock(errSecSuccess == status, nil, status);
   }
}

#pragma mark Internal methods

-(NSMutableDictionary*) prepareDict:(NSString *) key {
   
   NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
   [dict setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
   
   NSData *encodedKey = [key dataUsingEncoding:NSUTF8StringEncoding];
   [dict setObject:encodedKey forKey:(__bridge id)kSecAttrGeneric];
   [dict setObject:encodedKey forKey:(__bridge id)kSecAttrAccount];
   [dict setObject:keychainService forKey:(__bridge id)kSecAttrService];
   [dict setObject:(__bridge id)kSecAttrAccessibleAlwaysThisDeviceOnly forKey:(__bridge id)kSecAttrAccessible];
   
   //This is for sharing data across apps
   if(keychainGroup != nil) {
       [dict setObject:keychainGroup forKey:(__bridge id)kSecAttrAccessGroup];
   }
   
   return  dict;
}

@end