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Subclassing APLConfiguration encrypted NSString

Electric Bolt edited this page Jun 29, 2019 · 6 revisions

  NSString editable list implementation
  ENCRYPTED_STRING macro
  ENCRYPTED_STRING_IOS_WATCHOS macro
  Encryption best practice

The default value of an encrypted NSString is nil. You can change the default value of the property by assigning a new plain text value in an overridden reset method.

@property(strong) NSString propertyName;

This page describes encrypted strings. Appfigurate also supports plain textual strings.

NSString editable list implementation

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(propertyName, regex, description, ...)

StringListEdit

The NSString property can be changed in Appfigurate by allowing the user to select from a predefined list of valid choices. The user can customize the list adding by additional values using a UITextField and a regular expression validating input.

Objective-C example

@interface Configuration : APLConfiguration
@property(nonatomic, strong) NSString url;
@end

@implementation Configuration

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", @{@"Dev": ENCRYPTED_STRING_IOS_WATCHOS(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==",@""JaMa92a122zZs...Mnz23KamnZ0a="), @"Test": ENCRYPTED_STRING_IOS_WATCHOS(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE=",@"Na1MSadBCaDD...KKANZias199Km=="), @"Prod": ENCRYPTED_STRING_IOS_WATCHOS(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==",@"aZSDIMSaasiaM...8SKS1MMahfpIa=")});
...

ENCRYPTED_STRING macro

ENCRYPTED_STRING(plaintext, ciphertext)

For an iOS app where the APLConfiguration subclass has one public key use the ENCRYPTED_STRING macro for each list item in the ENCRYPTED_STRING_PROPERTY_LIST_EDIT.

The first parameter of the ENCRYPTED_STRING macro is the plain text, and will be used by DEBUG builds. The second parameter of the ENCRYPTED_STRING macro is the cipher text, and will be used by RELEASE builds. To generate the cipher text, use the macOS AppfigurateSE String Encryption utility or source editor extension for Xcode.

Objective-C example

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", @{@"Dev":ENCRYPTED_STRING(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ=="), @"Test":ENCRYPTED_STRING(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE="), @"Prod":ENCRYPTED_STRING(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==")});

ENCRYPTED_STRING_IOS_WATCHOS macro

ENCRYPTED_STRING_IOS_WATCHOS(plaintext, ciphertextIOS, ciphertextWatchOS)

For an iOS and watchOS app where the APLConfiguration subclass has two public keys, use the ENCRYPTED_STRING_IOS_WATCHOS macro for each list item in the ENCRYPTED_STRING_PROPERTY_LIST_EDIT macro.

The first parameter of the ENCRYPTED_STRING macro is the plain text, and will be used by DEBUG builds. The second and third parameters of the ENCRYPTED_STRING macro are the cipher text for iOS and watchOS apps, and will be used by RELEASE builds. To generate the cipher text, use the macOS AppfigurateSE String Encryption utility or source editor extension for Xcode.

Objective-C example

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", @{@"Dev": ENCRYPTED_STRING_IOS_WATCHOS(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==",@""JaMa92a122zZs...Mnz23KamnZ0a="), @"Test": ENCRYPTED_STRING_IOS_WATCHOS(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE=",@"Na1MSadBCaDD...KKANZias199Km=="), @"Prod": ENCRYPTED_STRING_IOS_WATCHOS(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==",@"aZSDIMSaasiaM...8SKS1MMahfpIa=")});

Encryption best practice

Using the ENCRYPTED_STRING and ENCRYPTED_STRING_IOS_WATCHOS macros guarantees that the plain text of the list item values will not be included in the resulting application binary, only the cipher text. The cipher text can only be decrypted by Appfigurate using the correct private key.

You can verify that the plain text is not included in the RELEASE application binary using the macOS strings tool as follows:

Terminal

> cd ~/Library/Developer/Xcode/DerivedData/AppfigurateWorkspace-esajjxyazigjunfteipthjfiobut/Build/Products/Release-iphoneos/AppfigurateExample (iOS).app
> strings AppfigurateExample | grep "https://dev.appfigurate.io/list"     // no results
> strings AppfigurateExample | grep "H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ=="     // prints H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==

It is best practice to use the ENCRYPTED_STRING and ENCRYPTED_STRING_IOS_WATCHOS macros to encrypt sensitive information such as server urls (e.g. internal test environments), rather than expose them as plain text.

Documentation

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