EncryptionController.m

/*
 Password Encryption Controller
 
 Copyright 2013 Thincast Technologies GmbH, Author: Dorian Johnson
 
 This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
 If a copy of the MPL was not distributed with this file, You can obtain one at
 http://mozilla.org/MPL/2.0/.
 */
 
#import "EncryptionController.h"
#import "SFHFKeychainUtils.h"
#import "TSXAdditions.h"
 
@interface EncryptionController (Private)
 
- (BOOL)verifyPassword:(Encryptor *)decryptor;
- (NSData *)encryptedVerificationData;
- (void)setEncryptedVerificationData:(Encryptor *)encryptor;
 
- (NSString *)keychainServerName;
- (NSString *)keychainUsername;
- (void)setKeychainPassword:(NSString *)password;
- (NSString *)keychainPassword;
- (NSString *)keychainDefaultPassword;
 
@end
 
static EncryptionController *_shared_encryption_controller = nil;
 
#pragma mark -
 
@implementation EncryptionController
 
+ (EncryptionController *)sharedEncryptionController
{
  @synchronized(self)
  {
    if (_shared_encryption_controller == nil)
      _shared_encryption_controller = [[EncryptionController alloc] init];
  }
 
  return _shared_encryption_controller;
}
 
#pragma mark Getting an encryptor or decryptor
 
- (Encryptor *)encryptor
{
  if (_shared_encryptor)
    return _shared_encryptor;
 
  NSString *saved_password = [self keychainPassword];
  if (saved_password == nil)
  {
    saved_password = [self keychainDefaultPassword];
    Encryptor *encryptor = [[[Encryptor alloc] initWithPassword:saved_password] autorelease];
    [self setEncryptedVerificationData:encryptor];
    _shared_encryptor = [encryptor retain];
  }
  else
  {
    Encryptor *encryptor = [[[Encryptor alloc] initWithPassword:saved_password] autorelease];
    if ([self verifyPassword:encryptor])
      _shared_encryptor = [encryptor retain];
  }
 
  return _shared_encryptor;
}
 
// For the current implementation, decryptors and encryptors are equivilant.
- (Encryptor *)decryptor
{
  return [self encryptor];
}
 
@end
 
#pragma mark -
 
@implementation EncryptionController (Private)
 
#pragma mark -
#pragma mark Keychain password storage
 
- (NSString *)keychainServerName
{
  return [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleName"];
}
 
- (NSString *)keychainUsername
{
  return @"master.password";
}
 
- (void)setKeychainPassword:(NSString *)password
{
  NSError *error;
  if (password == nil)
  {
    [SFHFKeychainUtils deleteItemForUsername:[self keychainUsername]
                               andServerName:[self keychainServerName]
                                       error:&error];
    return;
  }
 
  [SFHFKeychainUtils storeUsername:[self keychainUsername]
                       andPassword:password
                     forServerName:[self keychainServerName]
                    updateExisting:YES
                             error:&error];
}
 
- (NSString *)keychainPassword
{
  NSError *error;
  return [SFHFKeychainUtils getPasswordForUsername:[self keychainUsername]
                                     andServerName:[self keychainServerName]
                                             error:&error];
}
 
- (NSString *)keychainDefaultPassword
{
  NSString *password = [[NSUserDefaults standardUserDefaults] stringForKey:@"UUID"];
  if ([password length] == 0)
  {
    password = [NSString stringWithUUID];
    [[NSUserDefaults standardUserDefaults] setObject:password forKey:@"UUID"];
    [[NSUserDefaults standardUserDefaults] removeObjectForKey:@"TSXMasterPasswordVerification"];
  }
  return password;
}
 
#pragma mark -
#pragma mark Verification of encryption key against verification data
 
- (BOOL)verifyPassword:(Encryptor *)decryptor
{
  return [[decryptor plaintextPassword]
      isEqualToString:[decryptor decryptString:[self encryptedVerificationData]]];
}
 
- (NSData *)encryptedVerificationData
{
  return [[NSUserDefaults standardUserDefaults] dataForKey:@"TSXMasterPasswordVerification"];
}
 
- (void)setEncryptedVerificationData:(Encryptor *)encryptor
{
  [[NSUserDefaults standardUserDefaults]
      setObject:[encryptor encryptString:[encryptor plaintextPassword]]
         forKey:@"TSXMasterPasswordVerification"];
}
 
@end