iOS Code Signing Tutorials
This is Part-1 of the iOS Code Signing tutorial series. This series covers fundamentals of the iOS code signing process. You can find all the posts in the series linked below
- iOS Code Signing: 1. Getting Started
- iOS Code Signing: 2. Certificate Signing Requests
- iOS Code Signing: 3. Certificates
- iOS Code Signing: 4. Provisioning Profiles
- iOS Code Signing: 5. Signing iOS App
iOS Code Signing: Getting Started
Genuinely, iOS devices only run apps that have been signed by trusted developers unless you have jailbroken iOS devices. If you are an iOS engineer, you must have battled with code signing at some point. As code signing is one of the painful and cumbersome tasks for iOS developers but they can not run away from code signing activities. Code signing and provisioning profiles have been an ongoing annoyance and will continue to be there until developers completely understand the basics of the code signing. This is an introductory post explaining the code signing process with its benefits and limitations.
About this Series
Code signing of the iOS apps is one of the hot topics for every iOS developer. Although there are multiple resources available online as well as Apple has clean documentation on code signing process, it’s still a mystery. In this series, we will try to understand the code signing process from scratch including what’s needed to code signing to actual code signing process itself. We will also explore the GUI as well as command line ways of doing things whenever applicable. We will start from Certificate Signing Requests to get iOS Development certificate, then we will cover certificate and it’s internal parts. After understanding the certificates, we will do deep dive into the provisioning profiles and finally, we will understand the code signing process.
These series is written in my own words or language by doing some research on web and Apple’s documentation. I have covered all these reference material in the final post. I have also attached some screenshots from Apple Developer portal and Xcode so that readers can understand the concepts. I tried to hide all the sensitive content but if there is something exposed by mistake, please don’t hack me 🙂
Before we jump into Apple’s way of code signing iOS apps, let’s explore what is code signing in general. In real life, we sign different contracts, agreements for various things. Why we sign those contracts? what does signature means to us and why it’s important? It’s simple because signing contracts protect us legally and we have trust that whatever terms and conditions in the contracts cannot be altered whilst contract is in place. The signature also ensures security that contract comes from trusted authorities and not from scammers. It means signing contracts gives us security, safety and trust.
Similarly, code signing is the process of digitally signing any form of the code to confirm that who wrote the code and guarantee that code has not been changed or corrupted when it was signed. The code signing uses a cryptographic hash to verify authenticity and integrity of the software code. In the software world, code signing ensures the identity of the author, integrity of the code, build system and versioning so that users of the software feel secure and safe while using them. Code signing uses various security terms like a public key, private key, certificates, digital signatures etc. There are different approaches to code signing used on the different platforms e.g Linux, Windows, macOS.
iOS Code Signing
Apple supposedly has very powerful security mechanism apart from few recent glitches that you might have read in the news. It’s very hard for black-hat hackers to break this mechanism. Apple also uses strong code signing mechanism to provide security, integrity and safety of the iOS apps downloaded from Apple App Store. Most of the time, iOS code signing seems to be magic that happens under the hood. If it works everyone happy and if it doesn’t everyone became panic. Most of the iOS engineers have no clue what happens under the hood when apps they wrote is being singed. In recent days, Apple tried to make code signing less painful by introducing Automatic Signing feature in Xcode so that code signing activity doesn’t interrupt main development flow. Code signing on Apple platform relies on public-key cryptography on X.509 standard. We will discuss all these tools and techniques later in this series.
Why Learn About iOS Code Signing
As most of the code signing tasks are being handled by Xcode these days, then why we should care about the code signing and why we should invest our time to learn about it?
Here are some of the reasons to learn about the code signing internals:
- Gone are the days when iOS engineers used to deploy iOS apps from Xcode installed on the local machine. Companies are adopting DevOps and CI/CD to deploy software as soon as built so all the builds need to be automated without any human or GUI interactions.
- There are thousands of developer hours wasted because Xcode’s code signing failed and developer tries to fix the code signing issues by regenerating and repairing certificates and provisioning profiles.
- The third party tools like Fastlane has made build scripting much easier for the iOS developers. However, when Apple made changes in underlying technologies, Fastlane keeps breaking and developer spend hours, days and weeks fixing the broken deployment scripts. In some cases, engineers have to wait until new changes being implemented in the Fastlane.
- If you are iOS developer/engineer and want to be an iOS engineer for all your life then you don’t have to learn about these things. However, if you want to grow up in your career then you must know the underlying tools, technologies and entire iOS ecosystem in details. You won’t get to iOS Tech Lead or iOS Tech Architect or similar roles if you don’t know about these underlying technologies regardless of how good you are in your iOS development skills. As a tech architect, you should be able to fix code signing or similar infrastructure related issues quickly and without relying on Xcode or other third party tools.
Hope that is enough to convince the important of code signing. It’s up to you whether to learn it or leave it.
Let’s dive into the world of iOS code signing. We will cover everything from scratch in terms of whats needed and what it does under the hood. In order to get started, we need following things which I believe everyone already has if you reading this post.
- Apple Developer Membership
- Xcode 9+
Once you have all these, you are ready to dig into the iOS code signing stuff.
Benefits of Code Signing
Apple wants us to go through the complex code signing process because it has some benefits to real users. The users of iOS apps feel secure when they download the apps from Apple app store. The code signing ensures that
- The legitimate developer has written this code and it has an identity of the signer or author of the apps.
- Code signing ensures that code hasn’t been altered by someone since written by the author. It guarantees that code produced by the author is original and there is nothing injected into the code since its signed by the author.
- Users can download the apps from the developers that they trust without worrying too much about security.
Code signing is for safety and security of the iOS users so that they feel safe using the apps they downloaded from app store.
Limitations of the Code Signing
Although code signing is for the security of the users, there are some aspects that do not address security issues all the time.
- Code signing ensures that code has been coming from a legitimate developer who is the member of Apple Developer programme but doesn’t guarantee that code itself is free from security vulnerabilities.
- Code signing doesn’t guarantee that app plugins that load dynamically during the execution of apps are secure.
- There is no digital rights management or copy protection technology for the signed code.
Now that, we have covered the importance of learning about code signing and benefits and limitation. In the next post, we will go through the important concept where code signing process starts i.e Certificate Signing Requests.