KeychainItemWrapper.m

/*
     File: KeychainItemWrapper.m 
 Abstract: 
 Objective-C wrapper for accessing a single keychain item.
  
  Version: 1.2 
  
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*/ 

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

/*

These are the default constants and their respective types,
available for the kSecClassGenericPassword Keychain Item class:

kSecAttrAccessGroup			-		CFStringRef
kSecAttrCreationDate		-		CFDateRef
kSecAttrModificationDate    -		CFDateRef
kSecAttrDescription			-		CFStringRef
kSecAttrComment				-		CFStringRef
kSecAttrCreator				-		CFNumberRef
kSecAttrType                -		CFNumberRef
kSecAttrLabel				-		CFStringRef
kSecAttrIsInvisible			-		CFBooleanRef
kSecAttrIsNegative			-		CFBooleanRef
kSecAttrAccount				-		CFStringRef
kSecAttrService				-		CFStringRef
kSecAttrGeneric				-		CFDataRef
 
See the header file Security/SecItem.h for more details.

*/

@interface KeychainItemWrapper (PrivateMethods)
/*
The decision behind the following two methods (secItemFormatToDictionary and dictionaryToSecItemFormat) was
to encapsulate the transition between what the detail view controller was expecting (NSString *) and what the
Keychain API expects as a validly constructed container class.
*/
- (NSMutableDictionary *)secItemFormatToDictionary:(NSDictionary *)dictionaryToConvert;
- (NSMutableDictionary *)dictionaryToSecItemFormat:(NSDictionary *)dictionaryToConvert;

// Updates the item in the keychain, or adds it if it doesn't exist.
- (void)writeToKeychain;

@end

@implementation KeychainItemWrapper

@synthesize keychainItemData, genericPasswordQuery;

- (id)initWithIdentifier: (NSString *)identifier accessGroup:(NSString *) accessGroup;
{
    if (self = [super init])
    {
        // Begin Keychain search setup. The genericPasswordQuery leverages the special user
        // defined attribute kSecAttrGeneric to distinguish itself between other generic Keychain
        // items which may be included by the same application.
        genericPasswordQuery = [[NSMutableDictionary alloc] init];
        
		[genericPasswordQuery setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
        _identifier = identifier;
        [genericPasswordQuery setObject:identifier forKey:(__bridge id)kSecAttrGeneric];
		
		// The keychain access group attribute determines if this item can be shared
		// amongst multiple apps whose code signing entitlements contain the same keychain access group.
		if (accessGroup != nil)
		{
#if TARGET_IPHONE_SIMULATOR
			// Ignore the access group if running on the iPhone simulator.
			// 
			// Apps that are built for the simulator aren't signed, so there's no keychain access group
			// for the simulator to check. This means that all apps can see all keychain items when run
			// on the simulator.
			//
			// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
			// simulator will return -25243 (errSecNoAccessForItem).
#else			
			[genericPasswordQuery setObject:accessGroup forKey:(__bridge id)kSecAttrAccessGroup];
#endif
		}
		
		// Use the proper search constants, return only the attributes of the first match.
        [genericPasswordQuery setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];
        [genericPasswordQuery setObject:(id)kCFBooleanTrue forKey:(__bridge id)kSecReturnAttributes];
        
        NSDictionary *tempQuery = [NSDictionary dictionaryWithDictionary:genericPasswordQuery];
        
        CFTypeRef cfDictionary = NULL;
        if (SecItemCopyMatching((__bridge CFDictionaryRef)tempQuery, &cfDictionary) != noErr)
        {
            // Stick these default values into keychain item if nothing found.
            [self resetKeychainItem];
			
			// Add the generic attribute and the keychain access group.
			[keychainItemData setObject:identifier forKey:(__bridge id)kSecAttrGeneric];
			if (accessGroup != nil)
			{
#if TARGET_IPHONE_SIMULATOR
				// Ignore the access group if running on the iPhone simulator.
				// 
				// Apps that are built for the simulator aren't signed, so there's no keychain access group
				// for the simulator to check. This means that all apps can see all keychain items when run
				// on the simulator.
				//
				// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
				// simulator will return -25243 (errSecNoAccessForItem).
#else			
				[keychainItemData setObject:accessGroup forKey:(__bridge id)kSecAttrAccessGroup];
#endif
			}
		}
        else
        {
            // load the saved data from Keychain.
            NSMutableDictionary *outDictionary = (__bridge_transfer NSMutableDictionary *)cfDictionary;
            self.keychainItemData = [self secItemFormatToDictionary:outDictionary];
        }
    }
    
	return self;
}


- (void)setObject:(id)inObject forKey:(id)key 
{
    if (inObject == nil) return;
    id currentObject = [keychainItemData objectForKey:key];
    if (![currentObject isEqual:inObject])
    {
        [keychainItemData setObject:inObject forKey:key];
        [self writeToKeychain];
    }
}

- (id)objectForKey:(id)key
{
    return [keychainItemData objectForKey:key];
}

- (void)resetKeychainItem
{
	OSStatus junk = noErr;
    if (!keychainItemData) 
    {
        self.keychainItemData = [[NSMutableDictionary alloc] init];
    }
    else if (keychainItemData)
    {
        NSMutableDictionary *tempDictionary = [self dictionaryToSecItemFormat:keychainItemData];
		junk = SecItemDelete((__bridge CFDictionaryRef)tempDictionary);
        NSAssert( junk == noErr || junk == errSecItemNotFound, @"Problem deleting current dictionary." );
    }
    
    // Default attributes for keychain item.
    [keychainItemData setObject:@"" forKey:(__bridge id)kSecAttrAccount];
    [keychainItemData setObject:@"" forKey:(__bridge id)kSecAttrService];
    [keychainItemData setObject:@"" forKey:(__bridge id)kSecAttrLabel];
    [keychainItemData setObject:@"" forKey:(__bridge id)kSecAttrDescription];
    
	// Default data for keychain item.
    [keychainItemData setObject:[NSDictionary dictionary] forKey:(__bridge id)kSecValueData];
}

- (NSMutableDictionary *)dictionaryToSecItemFormat:(NSDictionary *)dictionaryToConvert
{
    /*// The assumption is that this method will be called with a properly populated dictionary
    // containing all the right key/value pairs for a SecItem.
    
    // Create a dictionary to return populated with the attributes and data.
    NSMutableDictionary *returnDictionary = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
    
    // Add the Generic Password keychain item class attribute.
    [returnDictionary setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
    
    // Convert the NSString to NSData to meet the requirements for the value type kSecValueData.
	// This is where to store sensitive data that should be encrypted.
    NSString *passwordString = [dictionaryToConvert objectForKey:(id)kSecValueData];
    [returnDictionary setObject:[passwordString dataUsingEncoding:NSUTF8StringEncoding] forKey:(id)kSecValueData];
    
    return returnDictionary;*/
    
    NSMutableDictionary * returnDict = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
	//[returnDict setObject:_identifier forKey:(id)kSecAttrGeneric];
	[returnDict setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
	
	// convert the dictionary to an info list for serialization
	// could contain multiple result sets to be handled
	NSDictionary * resultsInfo = [dictionaryToConvert objectForKey:(__bridge id)kSecValueData];
	
	NSString * error;
	NSData * xmlData = [NSPropertyListSerialization dataFromPropertyList:resultsInfo 
                                                                  format:NSPropertyListXMLFormat_v1_0 
                                                        errorDescription:&error];
	
	if (error != nil) 
    { 
		NSLog(@"dictionaryToSecItemFormat: Error! %@", error);
	}
	
    if (xmlData)
        [returnDict setObject:xmlData forKey:(__bridge id)kSecValueData];
	
	return returnDict;
}

- (NSMutableDictionary *)secItemFormatToDictionary:(NSDictionary *)dictionaryToConvert
{
    /*// The assumption is that this method will be called with a properly populated dictionary
    // containing all the right key/value pairs for the UI element.
    
    // Create a dictionary to return populated with the attributes and data.
    NSMutableDictionary *returnDictionary = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
    
    // Add the proper search key and class attribute.
    [returnDictionary setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
    [returnDictionary setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
    
    // Acquire the password data from the attributes.
    NSData *passwordData = NULL;
    if (SecItemCopyMatching((CFDictionaryRef)returnDictionary, (CFTypeRef *)&passwordData) == noErr)
    {
        // Remove the search, class, and identifier key/value, we don't need them anymore.
        [returnDictionary removeObjectForKey:(id)kSecReturnData];
        
        // Add the password to the dictionary, converting from NSData to NSString.
        NSString *password = [[[NSString alloc] initWithBytes:[passwordData bytes] length:[passwordData length] 
                                                     encoding:NSUTF8StringEncoding] autorelease];
        [returnDictionary setObject:password forKey:(id)kSecValueData];
    }
    else
    {
        // Don't do anything if nothing is found.
        NSAssert(NO, @"Serious error, no matching item found in the keychain.\n");
    }
    
    [passwordData release];
   
	return returnDictionary;*/
    
    
    NSMutableDictionary * returnDict = [NSMutableDictionary dictionaryWithDictionary:dictionaryToConvert];
	
	// to get the password data from the keychain item, add the search key and class attr required to obtain the password
	[returnDict setObject:(id)kCFBooleanTrue forKey:(__bridge id)kSecReturnData];
	[returnDict setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
	
	// call the keychain services to get the password
	OSStatus keychainErr = noErr;
	
    CFTypeRef cfXmlData = NULL;
	keychainErr = SecItemCopyMatching((__bridge CFDictionaryRef)returnDict, &cfXmlData);
	
	if (keychainErr == noErr)
    { 
		NSData * xmlData = (__bridge_transfer NSData *) cfXmlData;
		[returnDict removeObjectForKey:(__bridge id)kSecReturnData];
		
		NSString * errorDesc = nil;
		NSPropertyListFormat fmt;
		NSDictionary * resultsInfo = (NSDictionary *) [NSPropertyListSerialization propertyListFromData:xmlData
                                                                                       mutabilityOption:NSPropertyListMutableContainersAndLeaves
                                                                                                 format:&fmt
                                                                                       errorDescription: &errorDesc];
		
        if (resultsInfo)
            [returnDict setObject:resultsInfo forKey:(__bridge id)kSecValueData];
		
	} else { 
		NSLog(@"secItemFormatToDictionary: format error.");
	}
	
	return returnDict;
}

- (void)writeToKeychain
{
	OSStatus result; 
    CFTypeRef cfAttributes = NULL;
    if (SecItemCopyMatching((__bridge CFDictionaryRef)genericPasswordQuery, &cfAttributes) == noErr)
    {
        NSDictionary *attributes = (__bridge_transfer NSDictionary *) cfAttributes;
        
        // First we need the attributes from the Keychain.
        NSMutableDictionary *updateItem = [NSMutableDictionary dictionaryWithDictionary:attributes];
        // Second we need to add the appropriate search key/values. 
        [updateItem setObject:[genericPasswordQuery objectForKey:(__bridge id)kSecClass] forKey:(__bridge id)kSecClass];
        
        // Lastly, we need to set up the updated attribute list being careful to remove the class.
        NSMutableDictionary *tempCheck = [self dictionaryToSecItemFormat:keychainItemData];
        [tempCheck removeObjectForKey:(__bridge id)kSecClass];
		
#if TARGET_IPHONE_SIMULATOR
		// Remove the access group if running on the iPhone simulator.
		// 
		// Apps that are built for the simulator aren't signed, so there's no keychain access group
		// for the simulator to check. This means that all apps can see all keychain items when run
		// on the simulator.
		//
		// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
		// simulator will return -25243 (errSecNoAccessForItem).
		//
		// The access group attribute will be included in items returned by SecItemCopyMatching,
		// which is why we need to remove it before updating the item.
		[tempCheck removeObjectForKey:(__bridge id)kSecAttrAccessGroup];
#endif
        
        // An implicit assumption is that you can only update a single item at a time.
		
        result = SecItemUpdate((__bridge CFDictionaryRef)updateItem, (__bridge CFDictionaryRef)tempCheck);
		NSAssert( result == noErr || result == errSecDuplicateItem, @"Couldn't update the Keychain Item." );
    }
    else
    {
        // No previous item found; add the new one.
        /*NSMutableDictionary* query = [[NSMutableDictionary alloc] init];
		[query setObject:(id)kSecClassGenericPassword forKey:(id)kSecClass];
        [query setObject:_identifier forKey:(id)kSecAttrGeneric];
        [query setObject:@"Account" forKey:(id)kSecAttrAccount];
        [query setObject:@"Service" forKey:(id)kSecAttrService];
        result = SecItemDelete((CFDictionaryRef)query);*/
        
        result = SecItemAdd((__bridge CFDictionaryRef)[self dictionaryToSecItemFormat:keychainItemData], NULL);
		NSAssert( result == noErr || result == errSecDuplicateItem, @"Couldn't add the Keychain Item." );
    }
}

@end