commit	5be82c38d60ef3c1d9fc42bdbca8495434c88f0d	[log] [tgz]
author	Michael Groover <mpgroover@google.com>	Mon Aug 23 20:06:44 2021 -0700
committer	Michael Groover <mpgroover@google.com>	Tue Aug 31 07:03:08 2021 -0700
tree	6ba6a385d4d008db886da33bf8386438622d7310
parent	49d1a7fcbcfa4bf59d7981250b5f9c0773049ae1 [diff]

Add support for APK Signature Scheme v3.1 for rotation targeting

This commit adds support for a new v3.1 APK signature scheme that
allows APK signing key rotation to target T+. This version will still
default to using the v3.0 signing block for rotation, but once the
build system is updated to support the new rotation-min-sdk-version
option v3.1 will be enabled by default for all key rotations.

This commit also updates all of the golden APKs that use key rotation
because the minSdkVersion of the v3 signer is updated from 24 (the
first API level that supports the signature algorithm) to 28 (the
first API level that supports v3).

Bug: 192301300
Test: gradlew test
Change-Id: I49cc98ea803d18d53131a78be668921d58ac5f4b

30 files changed

tree: 6ba6a385d4d008db886da33bf8386438622d7310

README.md

apksig

apksig is a project which aims to simplify APK signing and checking whether APK signatures are expected to verify on Android. apksig supports JAR signing (used by Android since day one) and APK Signature Scheme v2 (supported since Android Nougat, API Level 24). apksig is meant to be used outside of Android devices.

The key feature of apksig is that it knows about differences in APK signature verification logic between different versions of the Android platform. apksig thus thoroughly checks whether an APK's signature is expected to verify on all Android platform versions supported by the APK. When signing an APK, apksig chooses the most appropriate cryptographic algorithms based on the Android platform versions supported by the APK being signed.

The project consists of two subprojects:

apksig -- a pure Java library, and
apksigner -- a pure Java command-line tool based on the apksig library.

apksig library

apksig library offers three primitives:

ApkSigner which signs the provided APK so that it verifies on all Android platform versions supported by the APK. The range of platform versions can be customized.
ApkVerifier which checks whether the provided APK is expected to verify on all Android platform versions supported by the APK. The range of platform versions can be customized.
(Default)ApkSignerEngine which abstracts away signing APKs from parsing and building APKs. This is useful in optimized APK building pipelines, such as in Android Plugin for Gradle, which need to perform signing while building an APK, instead of after. For simpler use cases where the APK to be signed is available upfront, the ApkSigner above is easier to use.

NOTE: Some public classes of the library are in packages having the word “internal” in their name. These are not public API of the library. Do not use *.internal.* classes directly because these classes may change any time without regard to existing clients outside of apksig and apksigner.

apksigner command-line tool

apksigner command-line tool offers two operations:

sign the provided APK so that it verifies on all Android platforms supported by the APK. Run apksigner sign for usage information.
check whether the provided APK's signatures are expected to verify on all Android platforms supported by the APK. Run apksigner verify for usage information.

The tool determines the range of Android platform versions (API Levels) supported by the APK by inspecting the APK's AndroidManifest.xml. This behavior can be overridden by specifying the range of platform versions on the command-line.