|author||Michael Groover <firstname.lastname@example.org>||Mon May 24 19:30:35 2021 -0700|
|committer||Michael Groover <email@example.com>||Wed Jun 09 16:42:59 2021 -0700|
Add initial support for appending signatures to an APK The V1 and V2 signature schemes support multiple signers, but currently apksig does not support appending a V1 or V2 signature to an already signed APK. This commit adds the initial support to append a V1 / V2 signature to an already signed APK through one of the following options: - The --append-signature option when signing via apksigner - ApkSigner.Builder#setOtherSignersSignaturePreserved(true) when using the apksig Java API These options can also be used when an APK has additional key / value attribute blocks within the APK signing block; using the same signing config will overwrite the existing signatures while preserving these additional blocks. Note, when an APK has multiple V1 and V2 signatures one signer must sign the APK multiple times since another signer appending their V1 signature will invalidate an existing V2 signature. The following process will allow two signers, A and B, to sign an APK with V1 and V2 signatures: 1. A signs the APK with a V1 and V2 signature; this will add the stripping protection attribute to A's V1 signature. 2. B uses one of the append options listed above to sign the APK with a V1 and V2 signature. This will invalidate A's V2 signature since V2 is a whole APK signature scheme and B's V1 signature will modify the APK, but A's V1 signature will still be valid. 3. A uses one of the append options listed above to sign the APK with a V2 signature. This will overwrite A's previous V2 signature using the updated contents of the APK and append this signature to B's existing signature in the V2 signature block. Bug: 186395570 Test: gradlew build Change-Id: I8ad2f21e111dcdc5e2c41695439794afba9cc1de Merged-In: I8ad2f21e111dcdc5e2c41695439794afba9cc1de
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 library offers three primitives:
ApkSignerwhich 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.
ApkVerifierwhich 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)ApkSignerEnginewhich 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
ApkSignerabove 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
apksigner command-line tool offers two operations:
apksigner signfor usage information.
apksigner verifyfor 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.