rustls-platform-verifier

A Rust library to verify the validity of TLS certificates based on the operating system's certificate facilities. On operating systems that don't have these, webpki and/or rustls-native-certs is used instead.

This crate is advantageous over rustls-native-certs on its own for a few reasons:

• Improved correctness and security, as the OSes CA constraints will be taken into account.
• Better integration with OS certificate stores and enterprise CA deployments.
• Revocation support via verifying validity via OCSP and CRLs.
• Less I/O and memory overhead because all the platform CAs don't need to be loaded and parsed.

This library supports the following platforms and flows:

Installation and setup

On most platforms, no setup should be required beyond adding the dependency via cargo:

rustls-platform-verifier = "0.1"

Android

Some manual setup is required, outside of cargo, to use this crate on Android. In order to use Android's certificate verifier, the crate needs to call into the JVM. A small Kotlin component must be included in your app's build to support rustls-platform-verifier.

Gradle Setup

rustls-platform-verifier bundles the required native components in the crate, but the project must be setup to locate them automatically and correctly.

Firstly, create an init script in your Android Gradle project, with a filename of init.gradle. This is generally placed in your project's root. In your project's settings.gradle, add these lines:

apply from: file("./init.gradle");
configurePlatformVerifierProject()

// includeFlat is not deprecated, see https://github.com/gradle/gradle/issues/18644#issuecomment-980037131 for more details.
//noinspection GrDeprecatedAPIUsage
includeFlat("rustls-platform-verifier")

// Note: This path is dependent on where your workspace's target path.
project(":rustls-platform-verifier").projectDir = file("$rootDir/../target/rustls-platform-verifier/android/")

Next, the rustls-platform-verifier external dependency needs to be setup. Open the init.gradle file and add the following, where $PATH_TO_ROOT is replaced with a directory navigation to where your project's Cargo.toml is located (ie; "../"):

ext.configurePlatformVerifierProject = {
    def cmdProcessBuilder = new ProcessBuilder(new String[] { "cargo", "check", "-p", "rustls-platform-verifier" })
    cmdProcessBuilder.directory(File("$PATH_TO_ROOT"))
    cmdProcessBuilder.environment().put("RUSTLS_PLATFORM_VERIFIER_GEN_ANDROID_SRC", "1")

    def cmdProcess = cmdProcessBuilder.start()

    cmdProcess.waitFor()
}

This script can be tweaked as best suits your project, but the cargo check invocation must be included.

Finally, sync your gradle project changes. It should pick up on the rustls-platform-verifier Gradle project and, if you look in ./target/rustls-platform-verifier, there should be an android folder containing the required Kotlin sources. After this, everything should be ready to use.Future updates of rustls-platform-verifier shouldn't need anything beyond the usual cargo update either.

Crate initialization

In order for the crate to call into the JVM, it needs handles from Android. These are provided either the init_external or init_hosted function. These give rustls-platform-verifier the resources it needs to make calls into the Android certificate verifier.

As an example, if your Rust Android component which the "native" Android part of your app calls at startup has an initialization, like this:

#[export_name = "Java_com_orgname_android_rust_init"]
extern "C" fn java_init(
    env: JNIEnv,
    _class: JClass,
    context: JObject,
) -> jboolean {
    // ... initialize your app's other parts here.
}

In the simplest case, you should to insert a call to rustls_platform_verifier::android::init_hosted() here, before any networking has a chance to run. This only needs to be called once and the verifier will be valid for the lifetime of your app's process.

extern "C" fn java_init(
    env: JNIEnv,
    _class: JClass,
    context: JObject,
) -> jboolean {
    // ... initialize your app's other parts here.

    // Then, initialize the certificate verifier for future use.
    rustls_platform_verifier::android::init_hosted(&env, context);
}

In more advanced cases, such as where your code already stores long-lived handles into the Android environment, you can alternatively use init_external. This function takes a &'static reference to something that implements the android::Runtime trait, which the crate then uses to obtain the access when required to the JVM.

Credits

Made with ❤️ by the 1Password team. Portions of the Android and Windows implementation were adapted and referenced from Chromium's verifier implementation as well.

License