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android / platform / tools / apksig / 3030f0111e5d100765efbdb7c7689e8f5b18e499
commit3030f0111e5d100765efbdb7c7689e8f5b18e499[log] [tgz]
authorMichael Groover <mpgroover@google.com>Wed May 24 14:14:57 2023 -0500
committerMichael Groover <mpgroover@google.com>Wed May 24 16:10:28 2023 -0500
treeb4339eaa7d663bde5a206eff5565489030439658
parentf75783e8a3f782f102f6e692c69e7c43eebc9721 [diff]
Use V3.1 content digest in V4.1 signature

The content digest algorithm is determined by the number of bits in
the signing key to ensure the digest is not weaker than the key.
When the V3.1 scheme is used to sign an APK, it is possible for the
key from the V3.0 signature to meet the requirements for the
CHUNKED_SHA256 digest algorithm while the key from the V3.1
signature meets the requirements for the CHUNKED_SHA512 digest
algorithm. This commit ensure that the V4.1 signature uses the
content digest from the V3.1 signing block since this is the
digest that will be used to verify the V4.1 signature on all
platform versions that support the V3.1 signature.

Bug: 282777109
Test: gradlew test
Change-Id: I622fda1dafb2ff625224a19f36bbdf1a0877ffc7
7 files changed
tree: b4339eaa7d663bde5a206eff5565489030439658
  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.