Keychain returns different values in each call - ios

Question

I have a class which saves an NSDictionary into KeyChain. It worked fine but suddenly, when I try to load the NSDictionary I get nil value.
This is the class:
//
// KeyChainHandler.m
//
//
#import "KeyChainHandler.h"
#define IDENTIFIER #"Identifier"
#interface KeyChainHandler ()
#property (strong, nonatomic, readwrite) NSDictionary *applicationData;
#end
#implementation KeyChainHandler
// Make this class a singleton
static KeyChainHandler *instance = nil;
+ (KeyChainHandler*)sharedKeyChain
{
#synchronized(self)
{
if (!instance) {
instance = [[self alloc] init];
}
}
return instance;
}
- (id)init
{
self = [super init];
if (self)
{
[self load];
}
return self;
}
- (void)saveObject:(NSDictionary*)data
{
self.applicationData = data;
[self storeDictionary:data toKeychainWithKey:IDENTIFIER];
}
- (NSDictionary*)load
{
NSDictionary *data = [KeyChainHandler dictionaryFromKeychainWithKey:IDENTIFIER];
self.applicationData = data;
return data;
}
- (void)remove
{
[self deleteDictionaryFromKeychainWithKey:IDENTIFIER];
}
- (void)storeDictionary:(NSDictionary*)data toKeychainWithKey:(NSString*)aKey
{
// serialize dict
NSData *serializedDictionary = [NSKeyedArchiver archivedDataWithRootObject:data];
// encrypt in keychain
// first, delete potential existing entries with this key (it won't auto update)
[self remove];
// setup keychain storage properties
NSDictionary *storageQuery = #{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecValueData: serializedDictionary,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecAttrAccessible: (__bridge id)kSecAttrAccessibleWhenUnlocked
};
OSStatus osStatus = SecItemAdd((__bridge CFDictionaryRef)storageQuery, nil);
if(osStatus != noErr) {
// do someting with error
}
}
+ (NSDictionary*)dictionaryFromKeychainWithKey:(NSString *)aKey
{
// setup keychain query properties
NSDictionary *readQuery = #{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecReturnData: (id)kCFBooleanTrue,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword
};
CFDataRef serializedDictionary = NULL;
OSStatus osStatus = SecItemCopyMatching((__bridge CFDictionaryRef)readQuery, (CFTypeRef *)&serializedDictionary);
if(osStatus == noErr) {
// deserialize dictionary
NSData *data = (__bridge NSData *)serializedDictionary;
NSDictionary *storedDictionary = [NSKeyedUnarchiver unarchiveObjectWithData:data];
return storedDictionary;
}
else {
// do something with error
return nil;
}
}
- (void)deleteDictionaryFromKeychainWithKey:(NSString*)aKey
{
// setup keychain query properties
NSDictionary *deletableItemsQuery = #{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecMatchLimit: (__bridge id)kSecMatchLimitAll,
(__bridge id)kSecReturnAttributes: (id)kCFBooleanTrue
};
CFArrayRef itemList = nil;
OSStatus osStatus = SecItemCopyMatching((__bridge CFDictionaryRef)deletableItemsQuery, (CFTypeRef *)&itemList);
// each item in the array is a dictionary
NSArray *itemListArray = (__bridge NSArray *)itemList;
for (NSDictionary *item in itemListArray) {
NSMutableDictionary *deleteQuery = [item mutableCopy];
[deleteQuery setValue:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
// do delete
osStatus = SecItemDelete((__bridge CFDictionaryRef)deleteQuery);
if(osStatus != noErr) {
// do something with error
}
}
}
#end
At AppDelegate when I print [[KeyChainHandler sharedHandler] load]; I get the correct data, then on login screen I try to do it again and I get nil. Then when I restart (just with CMD + R) the app, I don't get nil, I get the correct data again..
What seems to be the problem? maybe it's some kind of Apple's bug?

Answer 1

Why: call [[KeyChainHandler sharedHandler] load];, the property is already loaded at singleton creation and if changed the property would also be updated.
You do need to set the property to nil in remove.
Instead just use:
NSDictionary *dict = [KeyChainHandler sharedKeyChain].applicationData;
Note: the code is: sharedKeyChain, the example call is: sharedHandler.