/*
     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;
{
  self = [super init];
  
  if (self)
  {
    // 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:(id)kSecClassGenericPassword forKey:(id)kSecClass];
    [genericPasswordQuery setObject:identifier forKey:(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:(id)kSecAttrAccessGroup];
#endif
		}
		
		// Use the proper search constants, return only the attributes of the first match.
    [genericPasswordQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
    [genericPasswordQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnAttributes];
    
    NSDictionary *tempQuery = [NSDictionary dictionaryWithDictionary:genericPasswordQuery];
    
    NSMutableDictionary *outDictionary = nil;
    
    if (! SecItemCopyMatching((CFDictionaryRef)tempQuery, (CFTypeRef *)&outDictionary) == 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:(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:(id)kSecAttrAccessGroup];
#endif
			}
		}
    else
    {
      // load the saved data from Keychain.
      self.keychainItemData = [self secItemFormatToDictionary:outDictionary];
    }
    
		[outDictionary release];
  }
  
	return self;
}

- (void)dealloc
{
    [keychainItemData release];
    [genericPasswordQuery release];
    
	[super dealloc];
}

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

- (void)writeToKeychain
{
    NSDictionary *attributes = NULL;
    NSMutableDictionary *updateItem = NULL;
	OSStatus result;
    
    if (SecItemCopyMatching((CFDictionaryRef)genericPasswordQuery, (CFTypeRef *)&attributes) == noErr)
    {
      // First we need the attributes from the Keychain.
      updateItem = [NSMutableDictionary dictionaryWithDictionary:attributes];
      // Second we need to add the appropriate search key/values.
      [updateItem setObject:[genericPasswordQuery objectForKey:(id)kSecClass] forKey:(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:(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:(id)kSecAttrAccessGroup];
#endif
      
      // An implicit assumption is that you can only update a single item at a time.
      
      result = SecItemUpdate((CFDictionaryRef)updateItem, (CFDictionaryRef)tempCheck);
      NSAssert( result == noErr, @"Couldn't update the Keychain Item." );
    }
    else
    {
      // No previous item found; add the new one.
      result = SecItemAdd((CFDictionaryRef)[self dictionaryToSecItemFormat:keychainItemData], NULL);
      if (result != noErr) {
        NSString *message = [NSString stringWithFormat:@"Couldn't add the Keychain Item, code=%d", (int)result];
        NSAssert(result == noErr, message);
      }
    }
}

@end
