Android root detection using build tags?

Question

The following method is one of the ways we can programatically detect if an android device is rooted:

public boolean checkRootMethod1(){
    String buildTags = android.os.Build.TAGS;

    if (buildTags != null && buildTags.contains("test-keys")) {
        return true;
    }
    return false;
}

Can someone explain what this is actually doing? What is the "test-keys" build tag, and what does it have to do with root? I couldn't find any relevant information from google.

Answer 1

Release-Keys and Test-Keys has to do with how the kernel is signed when it is compiled. Release-Keys means it was signed with an official Key from an official developer. Test-Keys means it was signed with a custom key generated by a third-party developer. From a security standpoint Release-Keys generally means the kernel is more secure, which is not always the case.

Answer 2

String buildTags = android.os.Build.TAGS;

This code is for getting build.prop located in /system/build.prop. As you can see you are getting android.os.Build.TAGS that means you are getting ro.build.tags value inside build.prop. here is the code of build.java

For your second question I can not make sure it will work because my ro.build.tags string is release-keys in my rooted device.