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android / platform / tools / apksig / 45343b234b5c563e424177c66e6c6021edc7a013
commit45343b234b5c563e424177c66e6c6021edc7a013[log] [tgz]
authorMichael Groover <mpgroover@google.com>Tue Nov 30 16:54:37 2021 -0800
committerMichael Groover <mpgroover@google.com>Tue Nov 30 16:54:37 2021 -0800
tree5864c893b2b02fa673b514335c5d6e166f61f55b
parent45f34cf07116cf9b13809bd0d24f37670558c0b9 [diff]
Resolve verification errors for v3.1 sigs and min-sdk-version 33

apksig is designed to behave as the platform would based on the min /
max SDK versions; when a min-sdk-version is not explicitly provided,
apksig will use the minSdkVersion from the APK's manifest. A device
running Android T or later will only verify the v3.1 signature if it
exists; apksig will behave the same for an APK signed with a v3.1
signature and a min-sdk-version of 33 or later. This commit resolves
the verification errors that were reported when apksig only verified
the v3.1 signature with a min-sdk-version of 33 by properly
recognizing the v3.1 signature as an extension of v3 and also
sufficient to meet the min v2 signature requirement for apps targeting
SDK version 30.

Bug: 208504694
Test: gradlew test
Change-Id: I28eadf4103358eb23cbc10880ac90c394e54e333
4 files changed
tree: 5864c893b2b02fa673b514335c5d6e166f61f55b
  1. etc/
  2. src/
  3. Android.bp
  4. android_plugin_for_gradle.gradle
  5. build.gradle
  6. LICENSE
  7. OWNERS
  8. README.md
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.