Android Security Lints

This repository contains custom lint checks for Android development. These lint checks are by nature more security-focused and experimental than the built-in lint checks within Android Studio, and are intended for more security-conscious developers.

These lint checks are based on guidance from the Android Application Security Knowledge Base that the Android Vulnerability Research team has developed, and common recurring vulnerabilities that the team spots in the wild.

Visit the official Android Lint Github Repo for guidance on writing your own custom lint checks.

This library uses the Apache license, as is Google's default.

How to use this library

1. Clone it from GitHub.
2. Add the checks module to your app's build.gradle file:

dependencies {
  lintChecks project(':checks')
}

3. Add lintVersion to the overall project's build.gradle file in the ext section. See here for an example:

ext {
  ...
  lintVersion = '31.0.2'
}

Lint checks included in this library

MASVS-STORAGE

Lint Issue ID	Detector	Risk
ExposedRootPath	MisconfiguredFileProviderDetector	Allowing the root directory of the device in the configuration provides arbitrary access to files and folders for attackers
SensitiveExternalPath	MisconfiguredFileProviderDetector	Sensitive info like PII should not be stored outside of the application container or system credential storage facilities

MASVS-CRYPTO

Lint Issue ID	Detector	Risk
VulnerableCryptoAlgorithm	BadCryptographyUsageDetector	Using weak or broken cryptographic hash functions may allow an attacker to reasonably determine the original input
UnsafeCryptoAlgorithmUsage	BadCryptographyUsageDetector	Using insecure modes and paddings with cryptographic algorithms is unsafe and vulnerable to attacks
WeakPrng	WeakPrngDetector	Using non-cryptographically secure PRNGs in security contexts like authentication allows attackers to guess the randomly-generated numbers

MASVS-NETWORK

Lint Issue ID	Detector	Risk
DefaultCleartextTraffic	MissingNetworkSecurityConfigDetector	On API level 27 and below, the default network security config trusts cleartext traffic and needs to be explicitly opted out by the application to only use secure connections
DefaultTrustedUserCerts	MissingNetworkSecurityConfigDetector	On API level 23 and below, the default network security config trusts user-added CA certificates. In practice, it is better to limit the set of trusted CAs so only trusted CAs are used for an app's secure connections
DisableAllSafeBrowsing	SafeBrowsingDetector	Safe Browsing is a service to help applications check URLs against a known list of unsafe web resources. We recommend keeping Safe Browsing enabled at all times and designing your app around any constraints this causes.
InsecureDnsSdkLevel	DnsConfigDetector	Custom DNS configurations can be insecure, making an application susceptible to DNS spoofing attacks. We recommend instead making use of Android OS's built-in transport security on SDK levels 28 and above.

MASVS-PLATFORM

Lint Issue ID	Detector	Risk
TapjackingVulnerable	TapjackingDetector	Views without the filterTouchesWhenObscured attribute are susceptible to tapjacking attacks by other apps obscuring the UI to trick the user into performing certain actions
StrandhoggVulnerable	StrandhoggDetector	Android previously had a bug in task reparenting in earlier versions, allowing malicious applications to hijack legitimate user actions and trick users into providing credentials to malicious apps
MissingAutoVerifyAttribute	CustomSchemeDetector	Exporting sensitive functionality via custom URL schemes should be properly protected by making use of app link verification

MASVS-CODE

Lint Issue ID	Detector	Risk
InsecurePermissionProtectionLevel	PermissionDetector	Custom permissions should have a signature protectionLevel or higher.
UnintendedExposedUrl	UnintendedExposedUrlDetector	URLs that look intended for debugging and development purposes only are exposed in the application, allowing attackers to gain access to parts of the application and server that should be kept secure
UnintendedPrivateIpAddress	UnintendedExposedUrlDetector	Private IP addresses are referenced that may have been intended only for debugging and development, and should not be exposed publicly

Contact

For questions, comments or feature requests, please file an issue or start a discussion on Github. We would love to hear from you.