IOS keychain saves or loads failing - ios

Question

I am using this class to load and save a userid and password to the ios keychain.
Every once in a while either the load or save is failing on a real device. I can't tell which.
Am I doing anything wrong in this code?
Is there a better way I should be doing this?
This code is based on code at https://gist.github.com/mlapointe/6e88a9f059f1cc0dabec
#import <Foundation/Foundation.h>
#interface KeychainHelper : NSObject
#property (strong, nonatomic) NSMutableDictionary * keychainItem;
- (void)saveKeychainWithUserId:(NSString *)userId andPassword: (NSString *)password;
- (NSString *)getPassword;
- (NSString *)getUserId;
#end
#import <Security/Security.h>
#interface KeychainHelper ()
#end
#implementation KeychainHelper
- (NSMutableDictionary *)createEmptyKeychainItem {
//Let's create an empty mutable dictionary:
_keychainItem = [NSMutableDictionary dictionary];
//Populate it with the data and the attributes we want to use.
_keychainItem[(__bridge id)kSecClass] = (__bridge id)kSecClassInternetPassword;
_keychainItem[(__bridge id)kSecAttrAccessible] = (__bridge id)kSecAttrAccessibleAfterFirstUnlock;
_keychainItem[(__bridge id)kSecAttrServer] = #"myapp.com";
_keychainItem[(__bridge id)kSecReturnData] = (__bridge id)kCFBooleanTrue;
_keychainItem[(__bridge id)kSecReturnAttributes] = (__bridge id)kCFBooleanTrue;
return nil;
}
- (void)saveKeychainWithUserId: (NSString *) userId andPassword: (NSString *)password {
[self createEmptyKeychainItem];
// Check if this keychain item already exists.
if(SecItemCopyMatching((__bridge CFDictionaryRef)_keychainItem, NULL) == noErr) {
// Item Already Exists == Update instead
[self updateKeychainWithUserId:userId andPassword:password];
} else {
//Item does not exist -- create new
_keychainItem[(__bridge id)kSecValueData] = [password dataUsingEncoding:NSUTF8StringEncoding];
_keychainItem[(__bridge id)kSecAttrAccount] = userId;
OSStatus sts = SecItemAdd((__bridge CFDictionaryRef)_keychainItem, NULL);
if (sts != noErr) {
NSLog(#"Error Code while inserting keychain: %d", (int)sts);
}
}
}
- (void)updateKeychainWithUserId:(NSString *)userId andPassword:(NSString *)password {
NSMutableDictionary *attributesToUpdate = [NSMutableDictionary dictionary];
attributesToUpdate[(__bridge id)kSecValueData] = [password dataUsingEncoding:NSUTF8StringEncoding];
attributesToUpdate[(__bridge id)kSecAttrAccount] = userId;
// Must set these back to false for SecItemUpdate to work
_keychainItem[(__bridge id)kSecReturnData] = (__bridge id)kCFBooleanFalse;
_keychainItem[(__bridge id)kSecReturnAttributes] = (__bridge id)kCFBooleanFalse;
OSStatus sts = SecItemUpdate((__bridge CFDictionaryRef)_keychainItem, (__bridge CFDictionaryRef)attributesToUpdate);
if (sts != noErr) {
NSLog(#"Error Code while updating keychain: %d", (int)sts);
}
}
- (NSString *)getPassword {
CFDictionaryRef result = nil;
[self createEmptyKeychainItem];
OSStatus sts = SecItemCopyMatching((__bridge CFDictionaryRef)_keychainItem, (CFTypeRef *)&result);
if (sts == noErr) {
NSDictionary *resultDict = (__bridge_transfer NSDictionary *)result;
NSData *passwordData = resultDict[(__bridge id)kSecValueData];
NSString *password = [[NSString alloc] initWithData:passwordData encoding:NSUTF8StringEncoding];
return password;
} else {
NSLog(#"No Keychain found while getting password, Error Code: %d", (int)sts);
return nil;
}
}
- (NSString *)getUserId {
CFDictionaryRef result = nil;
[self createEmptyKeychainItem];
OSStatus sts = SecItemCopyMatching((__bridge CFDictionaryRef)_keychainItem, (CFTypeRef *)&result);
if (sts == noErr) {
NSDictionary *resultDict = (__bridge_transfer NSDictionary *)result;
return resultDict[(__bridge id)kSecAttrAccount];
} else {
NSLog(#"No Keychain found while getting userId, Error Code: %d", (int)sts);
return nil;
}
}
#end