This means it implements the required delegate method. The first thing to note is that CertificatePinner implements ChallengeHandler. Since we need to be able to override a delegate method, we are required to use at least version 1.3.2 of Ktor. I set out to write this certificate pinning functionality into a succinct class for KMP. Ultimately checking the certificate matches your expectations. Within this function, you need to check various aspects of the challenge. Represented in Kotlin: fun invoke( session: NSURLSession, challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential?) -> Unit ) You have to override a function on NSURLSessionDataDelegateProtocol and configure an NSURLSession with it. Implementation is simple, and I love their approach to this problem. OkHttp has long supported certificate pinning against public keys. Built into Ktor there is an iOS engine that uses the NSURLSession classes. In common code, you can make HTTP requests which go through the engines.įor Android, you can use an OkHttp engine. These engines conform to a common interface. Ktor provides engines that perform the platform-specific requests. Ktor client supports JVM, Android, iOS, Javascript, macOS, Linux, and Windows. Ktor’s client libraries enable you to author multiplatform code which connects to remote APIs. Ktor is a KMP framework for building asynchronous servers and clients. KMP provides mechanisms for writing platform-specific implementations for a common API. It is not about compiling all code for all platforms, and it doesn’t limit you to a subset of common APIs. Kotlin Multiplatform (KMP) is a way of writing cross-platform code in Kotlin. There is a multitude of information available about certificate pinning.

It also helps combat man-in-the-middle attacks. This helps to defend against attacks on certificate authorities. It is the act of constraining which certificates you trust. Pinning certificates is a common practice when interacting with remote APIs. How to implement certificate pinning in Kotlin Multiplatform using Ktor Certificate Pinning

Kotlin on ios