Native App Security

Full Title and Meme

An app or application that is installed by the user to their device, as distinct from a Web App that runs in the browser context only. Apps implemented using web-based technology but distributed as a native app, so-called "hybrid apps", are considered equivalent to native apps by RFC 8252.

Context

• This is a companion document to Native App Privacy
• The day when a personal computer was for running applications for the user is long gone, never to return.
• Today a personal computer depends on cloud based service for nearly all of its functionality.
• Some of those sites are willing to use a trusted User Agent, typically a web browser from a well-known and trusted vendor for rendering its content.
• The first of the Laws of Security tell us that when an attacker gets to run their code on your computer, it is no longer just your computer any longer.
• But now many Web Sites encourage to run their applications on the user device to improve their control of the User Experience.
• When these apps exchange user data with other locations, they are considered by OAuth 2.0 to be operating a clients of the user.
• But the security of these apps is questionable, a IETF standard OAuth 2.0 for Native Apps seeks to address some of the issues.
• For the case where the user is not forced to allow an application to run on their personal device, see the page Web Site Security.
• NIST Special Publication (SP) 800-53 Rev. 5 defines a mobile device as

  A portable computing device that has a small form factor such that it can easily be carried by a single individual; is designed to operate without a physical connection (e.g., wirelessly transmit or receive information); possesses local, non-removable data storage; and is powered on for extended periods of time with a self-contained power source. Mobile devices may also include voice communication capabilities, on-board sensors that allow the device to capture (e.g., photograph, video, record, or determine location) information, and/or built-in features for synchronizing local data with remote locations. Examples include smart phones, tablets, and e-readers.

Problems

• One of the worst case scenarios for Native App security is that of payments made directly from a user's bank account without the user selected user agent (browser) assuring that the user consents to the payment.
• In Open Banking it is proposed that a payment initiator and a bank can both have Native Apps running where the payment initiator app asks the banking app on the same device for permission to remove money from the user's account.
• The article Watch Out for a Clever Touch ID Scam Hitting the App Store shows how unscrupulous apps can fool the user in to granting access to their bank accounts.
• A Web View is a display of information from a Web Site. There is no trustworthy indication that the Native App has correctly displayed the information that it obtained from the Web Site.

Solutions

• The Native App exposes its name and the web site that backs it in a manner that allows the user to make a meaningful trust decision.
  • Android play store requires any app that uses a brand name service to be securely bound to a URL that properly exposes that brand.
  • Apple has not released any plans to improve app naming security as of 2018-09-21.
• Joint use Native Apps are provide to some industries for all to use. It makes the trust decision by the user much more difficult.
• Same Site was designed to help, but as of (2018-09-21) is not consistently applied. In 2020 a process of tightening the same site requirements was under way at blink.
• RFC 8258 OAuth 2.0 for Native Apps is a best practice document that requires all requests from native apps should only be made through external user-agents. This document assumes that those are browsers supplied by the o/s vendor or otherwise vetted as secure for the user. It includes details for each of the major platforms, iOS, Android and Windows. In particular it mentions the app's security identifier for Windows, but all os's give the apps some sort of identifier that survives update and should be the primary source of app identity as the os app store will assure uniqueness.

App Vetting Process

• Native Apps have been shown to be vulnerable by the public announcement of many breaches; see the discussion of Patient Choice.
• The FirstNet process of app vetting is already well tested for apps that are targeted to first responders. See their Developer Portal,
• NIST Special Publication 800-163 Revision 1 Vetting the Security of Mobile Applications 2019-04 describes a process to ensure that mobile applications conform to an organizations's security requirements and are reasonably free from vulnerabilities. The following are extracted from that document.
• NIST SP 800-218 draft (2021-09-30) Secure Software Development Framework (SSDF) Version 1.1: Recommendations for Mitigating the Risk of Software Vulnerabilities

NIST NCCoE Support

• Mobile Device Security Community of Interest from the National Cybersecurity Center of Excellence, author Gema Howell (2019-08)
• Referenced NIST SP 800-30 Rev. 1: Guide for Conducting Risk Assessments
• Identified Threats Events (TE) using the NIST Mobile Threat Catalogue (MTC)

NIST Threat Assessment

These treat events were taken from the Mobile Device Security Community of Interest 2019-08

• Their Mobile Threat Catalogue is based on Draft NISTIR 8144: Assessing Threats to Mobile Devices & Infrastructure.
• Additional reading material is at Guidelines for Managing the Security of Mobile Devices in the Enterprise which is focused on Corporate-owned devices.

Threat Event	Closest STRIDE Threat	Desired property
TE-1: Unauthorized access to sensitive information via a malicious or privacy-intrusive application	Information disclosure	Confidentiality
TE-2: Theft of credentials through an SMS or email phishing campaign	Elevation of Privilege	Authorization
TE-3: Malicious applications installed via URLs in SMS or email messages	Denial of Service	Availability.
TE-4: Confidentiality and integrity loss due to exploitation of known vulnerability in the OS or firmware	Repudiation	Non-repudiability.
TE-5: Violation of privacy via misuse of device sensors	Spoofing	Authenticate
TE-6: Compromise of the integrity of the device or its network communications via installation of malicious EMM/MDM, network, VPN profiles, or certificates	Tampering	Integrit

• The STRIDE model is described in the wiki page Threat Model

Android Support

• Rules for apps installed on Android devices
• Adding Server-Side License Verification to Your App
• App Licensing
• Pre Oauth Entity Trust describes a means to represent third-party application endorsement for health care applications. POET’s goal is to help consumers distinguish between applications that have an endorsement versus applications that have no pedigree (i.e untrusted and could be malicious).
• Android App list of Data Categories that require User Consent. https://support.google.com/googleplay/answer/6270602?hl=en

Apple iPhone Support

• Rules for apps installed on Apple devices are (not clear)
• Apple iPhone App Requesting Permission: https://developer.apple.com/design/human-interface-guidelines/ios/app-architecture/requesting-permission/
• Apple iPhone app Requesting Authorization to use System Features: https://developer.apple.com/documentation/uikit/core_app/protecting_the_user_s_privacy
• Apple CKContainer manages all attempts to access user data on the device or in iCloud. https://developer.apple.com/documentation/cloudkit/ckcontainer

Windows Support

• Windows (UWP) settings are on all Windows 10 computer, but do not seem to be shown anywhere on the web. Just navigate start -> settings -> privacy -> app settings.
• Rules for apps installed on Windows devices are of two types (UWP and traditional), but it is not clear how the user could possibly distinguish, so the concept has not been helpful.

References

Other References

• SMS is easy to hijack and should not be used for security purposes.
• The Open Web Application Security Project (OWASP) is a 501(c)(3) worldwide not-for-profit charitable organization focused on improving the security of web site software.
• ISACs are member-driven organizations, delivering all-hazards threat and mitigation information to asset owners and operators.
• Native App wiki page.
• Native App Privacy wiki page.