From b71e39893596a7aa6a8733b9add83452c57b7df9 Mon Sep 17 00:00:00 2001
From: Michael Groover <mpgroover@google.com>
Date: Tue, 16 Jun 2020 13:17:34 -0700
Subject: [PATCH] Relax minimum signature scheme version for apps on system
 partition

Android 11 requires a minimum V2 APK signature for apps targeting SDK
version 30+; however some apps on a system partition can only be signed
with the V1 signature scheme. This commit relaxes the minimum signature
scheme version to allow for these apps on a system partition.

Bug: 158728035
Test: atest PackageManagerTest
Test: atest PackageManagerTests
Test: atest PkgInstallSignatureVerificationTest
Change-Id: I1a95fd6894cc937e00ad1ac54d1846b51b48e9cd
---
 .../android/content/pm/PackageParser.java     |  6 ++++--
 .../pm/parsing/ParsingPackageUtils.java       |  6 ++++--
 .../server/pm/PackageManagerService.java      | 20 ++++++++++---------
 3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/core/java/android/content/pm/PackageParser.java b/core/java/android/content/pm/PackageParser.java
index c8dd4d9d9d51d..6dc74976a0c12 100644
--- a/core/java/android/content/pm/PackageParser.java
+++ b/core/java/android/content/pm/PackageParser.java
@@ -1374,9 +1374,11 @@ public class PackageParser {
         }
         SigningDetails verified;
         if (skipVerify) {
-            // systemDir APKs are already trusted, save time by not verifying
+            // systemDir APKs are already trusted, save time by not verifying; since the signature
+            // is not verified and some system apps can have their V2+ signatures stripped allow
+            // pulling the certs from the jar signature.
             verified = ApkSignatureVerifier.unsafeGetCertsWithoutVerification(
-                        apkPath, minSignatureScheme);
+                        apkPath, SigningDetails.SignatureSchemeVersion.JAR);
         } else {
             verified = ApkSignatureVerifier.verify(apkPath, minSignatureScheme);
         }
diff --git a/core/java/android/content/pm/parsing/ParsingPackageUtils.java b/core/java/android/content/pm/parsing/ParsingPackageUtils.java
index 317107829623e..bc9c71e7a68e9 100644
--- a/core/java/android/content/pm/parsing/ParsingPackageUtils.java
+++ b/core/java/android/content/pm/parsing/ParsingPackageUtils.java
@@ -2748,9 +2748,11 @@ public class ParsingPackageUtils {
         SigningDetails verified;
         try {
             if (skipVerify) {
-                // systemDir APKs are already trusted, save time by not verifying
+                // systemDir APKs are already trusted, save time by not verifying; since the
+                // signature is not verified and some system apps can have their V2+ signatures
+                // stripped allow pulling the certs from the jar signature.
                 verified = ApkSignatureVerifier.unsafeGetCertsWithoutVerification(
-                        baseCodePath, minSignatureScheme);
+                        baseCodePath, SigningDetails.SignatureSchemeVersion.JAR);
             } else {
                 verified = ApkSignatureVerifier.verify(baseCodePath, minSignatureScheme);
             }
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index 5e5274849fcd6..6cddc9eb674bb 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -12144,15 +12144,17 @@ public class PackageManagerService extends IPackageManager.Stub
                 }
             }
 
-            // Ensure the package is signed with at least the minimum signature scheme version
-            // required for its target SDK.
-            int minSignatureSchemeVersion =
-                    ApkSignatureVerifier.getMinimumSignatureSchemeVersionForTargetSdk(
-                            pkg.getTargetSdkVersion());
-            if (pkg.getSigningDetails().signatureSchemeVersion < minSignatureSchemeVersion) {
-                throw new PackageManagerException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
-                        "No signature found in package of version " + minSignatureSchemeVersion
-                                + " or newer for package " + pkg.getPackageName());
+            // If the package is not on a system partition ensure it is signed with at least the
+            // minimum signature scheme version required for its target SDK.
+            if ((parseFlags & PackageParser.PARSE_IS_SYSTEM_DIR) == 0) {
+                int minSignatureSchemeVersion =
+                        ApkSignatureVerifier.getMinimumSignatureSchemeVersionForTargetSdk(
+                                pkg.getTargetSdkVersion());
+                if (pkg.getSigningDetails().signatureSchemeVersion < minSignatureSchemeVersion) {
+                    throw new PackageManagerException(INSTALL_PARSE_FAILED_NO_CERTIFICATES,
+                            "No signature found in package of version " + minSignatureSchemeVersion
+                                    + " or newer for package " + pkg.getPackageName());
+                }
             }
         }
     }