Users' Data Security in iOS Applications

U S E R S ’ D ATA S E C U R I T YI N I O S A P P L I C A T I O N S

Odessa Innovation Week, WebCamp 2015

W H AT I S U S E R D ATA

User data is being generated during interactions with user

I T I S A D E V E L O P E R ’ S R E S P O N S I B I L I T Y T O P R O T E C T

S E N S I T I V E D ATA

U S E R D ATA S TAT E S

• Runtime data

• Stored data

• Transmitted data

W H AT C O U L D P O S S I B LY G O W R O N G ?

• Runtime data

• Stored data

C O U L D B E S T O L E N ,

M O D I F I E D O R D E L E T E D

W H AT S H O U L D W E D O ?

• Runtime data

• Stored data

encrypt storage

encrypt transport

use secure design

R U N T I M E D ATA

U I PA S T E B O A R D

• general Pasteboard is open for everyone

[[UIPasteboard generalPasteboard] setValue:@"1234 5689 3455 6604" forPasteboardType:@"card"];

• custom Pasteboards are open for current app and apps with same team ID

UIPasteboard * pasteboard = [UIPasteboard pasteboardWithName:@"my.app" create:YES];pasteboard.persistent = YES; [pasteboard setValue:@"1234 5689 3455 6604”forPasteboardType:@"card"];

U I PA S T E B O A R D

• prevent copying sensitive data

@implementation UITextView (DisableCopyPaste)- (BOOL)canPerformAction:(SEL)action withSender:(id)sender { [UIMenuController sharedMenuController].menuVisible = NO;

return NO; } @end

S N A P S H O T T I N G & S C R E E N S H O T T I N G

- (void)applicationWillResignActive:(UIApplication *)application { UIImageView * imageView = [[UIImageView alloc]initWithFrame:[self.window frame]]; [imageView setImage:[UIImage imageNamed:@"mySplash"]]; [self.window addSubview:imageView]; }

• hide any sensitive data before snapshotting

• or set your picture as snapshot

- (void)applicationWillResignActive:(UIApplication *)application { self.window.rootViewController.view.cardLabel.hidden = YES;

PA S S W O R D - P R O T E C T I O N

• ask password on app launching (if it’s really needed)

• ask password on entering ‘sensitive’ areas

• ask password to confirm some actions

• ask password on configuration screen

T O U C H I D

LocalAuthentication Framework

use as alternative to your application’s password

T O U C H I D

#import <LocalAuthentication/LocalAuthentication.h>

LAContext * myContext = [LAContext new];NSError * authError = nil;NSString * myLocalizedReasonString = @"Authenticate using your finger";if ([myContext canEvaluatePolicy:LAPolicyDevice OwnerAuthenticationWithBiometrics error:&authError]) { ...} else { NSLog(@"Authentication error %@", authError); }

T O U C H I D

[myContext evaluatePolicy: LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:myLocalizedReasonString reply:^(BOOL success, NSError * error) { if (success) { NSLog(@"User is authenticated successfully”); } else { NSLog(@"Authentication failed with error %@", error); } }];

T O U C H I Dswitch (error.code) { case LAErrorAuthenticationFailed: NSLog(@"Authentication Failed"); break; case LAErrorUserCancel: NSLog(@"User pressed Cancel button"); break; case LAErrorUserFallback: NSLog(@"User pressed \"Enter Password\""); [self showPassword]; break; default: NSLog(@"Touch ID is not configured"); [self showPassword]; break;}

S T O R E D D ATA

D O N O T S T O R E

• passwords

• keys

• any financial data

• logs!

P L A I N T E X T K E Y S A R E B A D

[Parse setApplicationId:@"GpvoqI7Ut29H...2JL1dyceOv0hV1" clientKey:@“sv8wcfIf0neo...y2m9YIwu0OxQr”];

static NSString *kMyAPIKey = @"mySecretApiKey";

strings MyApp.app/MyApp > myapp.txt

GpvoqI7Ut29...2JL1dyceOv0hV1 sv8wcfIf0neo...y2m9YIwu0OxQr application did finish launching window T@"UIWindow",&,N T@"UIWindow",&,N,V_window

[Parse setApplicationId:@"GpvoqI7Ut29H...2JL1dyceOv0hV1" clientKey:@“sv8wcfIf0neo...y2m9YIwu0OxQr”];

AV O I D P L A I N T E X T K E Y S

• store like hex strings

unsigned char myApiKey[] = { 0xAB, 0xAA, 0xBE, 0xDE, 0xEF };

• obfuscateNSString * key = [NSString stringWithFormat:@"%@%@%@%@", @"my", @"secret", @"Api", @“Key"]; NSString * key = [NSString stringWithFormat:@"%3$@%2$@%1$@%4$@", @"Api", @"secret", @"my", @"Key"];

NSString * format = [[[@"x3$yx2$z%1$yx4$@" stringByReplacingOccurrencesOfString:@"x" withString:@"%"] stringByReplacingOccurrencesOfString:@"y" withString:@"@"] stringByReplacingOccurrencesOfString:@"z" withString:@"@"];NSString * key = [NSString stringWithFormat:format, @"Api", @"secret", @"my", @"Key"];

"mySecretApiKey"

U S E E N C R Y P T E D K E Y S

1. take key in plain text

NSData * encryptedData = [RNEncryptor encryptData:kMyAPIKey withSettings:kRNCryptorAES256Settings password:[self calculatePassword] error:&error]; NSString * resultString = [[NSString alloc] initWithData:encryptedData

encoding:NSUTF8StringEncoding];

2. encrypt it

3. hardcode encrypted key

static NSString *kMyAPIKeyEncrypted = @“789fae43c3e66113e48cebfafeef6806542c0c9062b78b686f515acb09b2c0a6";

NSData *decryptedData = [RNDecryptor decryptData:encryptedData withPassword:[self calculatePassword] error:&error];

NSString * resultString = [[NSString alloc] initWithData:encryptedData encoding:NSUTF8StringEncoding];

4. decrypt it before using

5. use generated password, not static string

- (NSString * )calculatePassword { CGFloat result = (CGFloat) (1.0/23.0); return [NSString stringWithFormat:@"%.10f", result];}

@“0.0434782609” this password is calculated each time;

is not stored as string

W H E R E T O S T O R E S E N S I T I V E D ATA ?

• NSUserDefaults

• plist

• files

• database

• keychain

• NSUserDefaults

• plist

• files

• database

• keychain

U S E K E Y C H A I N

• NSUserDefaults

• plist

• files

• database

• keychain

O R U S E E N C R Y P T I O N !

E N C R Y P T A L L D ATA

C O M M O N C R Y P T O F R A M E W O R K

E N C R Y P T A L L D ATA#import <CommonCrypto/CommonCryptor.h> - (NSData *)AES256EncryptWithKey:(NSString*)key { char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesEncrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, NULL [self bytes], dataLength, /* input */ buffer, bufferSize, /* output */ &numBytesEncrypted); if (cryptStatus == kCCSuccess) { //the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; } free(buffer); return nil; }

C O M M O N C R Y P T O

E N C R Y P T A L L D ATA#import <CommonCrypto/CommonCryptor.h> - (NSData *)AES256EncryptWithKey:(NSString*)key { char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesEncrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, NULL [self bytes], dataLength, /* input */ buffer, bufferSize, /* output */ &numBytesEncrypted); if (cryptStatus == kCCSuccess) { //the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; } free(buffer); return nil; }

C O M M O N C R Y P T O

#import <RNCryptor/RNCryptor.h>NSData *data = [@"Data" dataUsingEncoding:NSUTF8StringEncoding];NSError *error;NSData *encryptedData = [RNEncryptor encryptData:data withSettings:kRNCryptorAES256Settings password:aPassword error:&error];

NSData *decryptedData = [RNDecryptor decryptData:encryptedData withPassword:aPassword error:&error];

https://github.com/RNCryptor/RNCryptor

U S E W R A P P E R S

#import "scell_seal.h"

NSData *data = [@"Data" dataUsingEncoding:NSUTF8StringEncoding];

TSCellSeal * cellSeal = [[TSCellSeal alloc] initWithKey:masterKeyData];NSData * encryptedMessage = [cellSeal wrapData:data context:nil error:&error];NSData * decryptedMessage = [cellSeal unwrapData:encryptedMessage context:nil error:&error];

https://github.com/cossacklabs/themis

U S E C O O L L I B R A R I E S

E N C R Y P T D ATA B A S E

SQLCipher (+FMDB)

https://github.com/sqlcipher/sqlcipher

CoreData

https://github.com/project-imas/encrypted-core-data

F I L E S P R O T E C T I O N

allows to encrypt NSFiles

* NSFileProtectionNone

* NSFileProtectionComplete Cannot be accessed while device locked.

* NSFileProtectionCompleteUnlessOpen Opens only when device is unlocked; can be accessed whenever

* NSFileProtectionCompleteUntilFirstUserAuthentication Opens only after device is booted; can be accessed whenever.

NSFileManager * fileManager = [NSFileManager defaultManager]; NSDictionary * attributes = @{ NSFileProtectionKey : NSFileProtectionComplete };[fileManager createFileAtPath:path contents:data attributes:attributes];[fileManager setAttributes:attributes ofItemAtPath:path error:&errorFolderProtect];

[SSKeychain setPassword:password forService:@"com.my.app" account:@"MyAppUserPasswordKey"];

S E C U R E K E Y C H A I N

https://github.com/soffes/sskeychain

S E C U R I T Y F R A M E W O R K O R U S E W R A P P E R S

D I S A B L E D E B U G G I N G Y O U R A P P S

typedef int (*ptrace_ptr_t)(int _request, pid_t _pid, caddr_t _addr, int _data); #if !defined(PT_DENY_ATTACH) #define PT_DENY_ATTACH 31#endif

void disable_gdb() { void* handle = dlopen(0, RTLD_GLOBAL | RTLD_NOW); ptrace_ptr_t ptrace_ptr = dlsym(handle, "ptrace"); ptrace_ptr(PT_DENY_ATTACH, 0, 0, 0); dlclose(handle); }

int main(int argc, char * argv[]) { #if !(DEBUG) // Don't interfere with Xcode debugging sessions. disable_gdb();#endif @autoreleasepool { return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class])); } } https://www.theiphonewiki.com/wiki/Bugging_Debuggers

T R A N S M I T T E D D ATA

S E N D I N G P L A I N T E X T D ATA

• plain text could be easily stolen or modified

• sending passwords as plain text is bad idea

S E N D I N G P L A I N T E X T D ATA

• plain text could be easily stolen or modified

• sending passwords as plain text is bad idea

U S E H T T P S !

U S I N G H T T P S

HTTPs protects only POST requests (do not use GET*)

* https://blog.httpwatch.com/2009/02/20/how-secure-are-query-strings-over-https/

U S I N G H T T P S : B A D P R A C T I C E S

• allowing self-signed certificates

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge { [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge]; }

[AFSecurityPolicy setAllowInvalidCertificates:YES]; [AFSecurityPolicy setValidatesDomainName:NO];

• allowing invalid certificates

• allowing self-signed certificates

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge { [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge]; }

[AFSecurityPolicy setAllowInvalidCertificates:YES]; [AFSecurityPolicy setValidatesDomainName:NO];

• allowing invalid certificates

A F N E T W O R K I N G B U G S 2 . 5 . 1 - 2 . 5 . 2

H T T P S

O N I O S 9 H T T P I S T U R N E D O F F !

(as required by App Transport Security)

H T T P S

you should disable ATS to use HTTP

H T T P S

you should disable ATS to use HTTP

H T T P S D O E S N ’ T M E A N T O U S E P L A I N T E X T

anyone can generate fake SSL certificate and your app will trust him

MitM attacks lead to stolen or modified data

H T T P S I S N O T S O S E C U R E

A L L D ATA S H O U L D B E E N C R Y P T E D

For messaging you should use special crypto, not just encrypting data like for storage.

E N C R Y P T I N G C O M M U N I C AT I O N

Communication is sequence of messages

When sequence get’s recorded, it is easier to crack the key based on captured data

Your keys should be ephemeral, your exchange should be sequence aware, authenticated and content-

validating

E N D T O E N D

P E R F E C T F O R WA R D S E C R E C Y

P R O N E T O T I M I N G AT TA C K S

AUTHENT ICATE MESSAGES

U S E K E Y A G R E E M E N T P R O T O C O L

validating

E N D T O E N D

P E R F E C T F O R WA R D S E C R E C Y

P R O N E T O T I M I N G AT TA C K S

AUTHENT ICATE MESSAGES

U S E K E Y A G R E E M E N T P R O T O C O L

Themis (Secure Message / Secure Session) (https://github.com/cossacklabs/themis)

OTRKit (https://github.com/ChatSecure/OTRKit)

libsodium / NaCL (https://github.com/mochtu/libsodium-ios)

T H E R E ’ S A L I B F O R T H AT !

M O R E T O R E A D

• The Mobile Application Hacker's Handbook • https://books.google.com.ua/books?

id=UgVhBgAAQBAJ

• Secure Developing on iOS • https://www.isecpartners.com/media/11221/

secure_development_on_ios.pdf

M O R E T O R E A D

• Security Coding Guide • https://developer.apple.com/library/ios/

documentation/Security/Conceptual/SecureCodingGuide/Introduction.html#//apple_ref/doc/uid/TP40002477-SW1

M O R E T O R E A D

• Designing Secure User Interfaces • https://developer.apple.com/library/ios/

documentation/Security/Conceptual/SecureCodingGuide/Articles/AppInterfaces.html#//apple_ref/doc/uid/TP40002862-SW1

M O R E T O R E A D

• https://www.theiphonewiki.com/wiki/Bugging_Debuggers

• http://www.splinter.com.au/2014/09/16/storing-secret-keys/

• http://priyaaank.tumblr.com/post/81172916565/validating-ssl-certificates-in-mobile-apps

• https://www.venafi.com/blog/post/ssl-vulnerabilities-in-your-mobile-apps-what-could-possibly-go-wrong

L A S T S L I D E

@vixentael

Anastasi, iOS dev @ Stanfy

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