Changes for bug 1838680

handlers_racing_test.go

@@ -78,7 +78,7 @@ func TestSignaturePass(t *testing.T) {
 			},
 		},
 		{
-			// Sign an APK file
+			// Sign an APK file that has no min-sdk-version so we have to manually force it
 			"/sign/file",
 			[]formats.SignatureRequest{
 				formats.SignatureRequest{
@@ -87,6 +87,28 @@ func TestSignaturePass(t *testing.T) {
 				},
 			},
 		},
+		{
+			// Sign an APK file
+			/*
+				How to create a small-enough APK:
+					1. Create a new Android project with Android Studio, the official Android IDE
+					2. Initialize a git repository, in case you make a mistake with one of the steps above
+					3. Delete all files that seem unnecessary
+					4. Strip out unnecessary metadata in AndroidManifest.xml
+					5. Add <uses-sdk android:minSdkVersion="21"/> to AndroidManifest.xml. 21 matches Android 5.0: https://apilevels.com/
+					6. Remove all dependencies in build.gradle
+					7. `./gradlew clean assemble && ls -lh app/build/outputs/apk/release/app-release-unsigned.apk` says the generated APK is 1.2 kB.
+					8. `unzip -l app-release-unsigned.apk` to show all files contained in the APK. Only AndroidManifest.xml is needed. Purge all others with `zip -d app-release-unsigned.apk $file`
+					9. base64 the APK and paste the content in this file.
+			*/
+			"/sign/file",
+			[]formats.SignatureRequest{
+				formats.SignatureRequest{
+					Input: "UEsDBAAAAAAIACEIIQJ3XNdl0gIAAMwHAAATAAAAQW5kcm9pZE1hbmlmZXN0LnhtbJ2VTU9TQRSGz/QCrZYiFMq3RhMTjQlFkYVxYYJEokllodGFKyoFIbTQ9F5QEmNYu3bpwoV7/QX+AhcuWPhr1GfOndtOr238uM17Z+adc945c+bcaSA5+ZoVMTIvrwdELkjneef1R8AsKIMK2AYn4CP4Ar6DH2DZiNwBa2AbHIG34D04BdMZkSWwBt6Ab+BqwBg8A3XwAZyCQalLVZ7LFq3IgOwzajASYt6SV9KUA2lJRL8GV2BuF5vHjPbkKWxLQpgDOJG8HHUxq7xrqpWeWW+vMop2lZkXjKK+ulWiqzN6KXfpb2JzSGR2JtReEmUoj3jbnYxhdcAaTVTq6PVWnvkLq2QXncwEcoMzuk4vQ++mntxDOZYVjaSO3ya2kfNfYn5Io47a6+ba4yMQ4SuShdtnpRY2u5rt2RRT1txHGkvEyNcsE8GKPCCzIhf/4BdHt0XObdaOYSr4PsF3Ve7LPXIY57zXbmzsaX8baZzHstZMVTNq81mmd9xHyeblyn/52b1WdU8rv2XxmuzQi/C7LYv8Qix2UGzgEWrOujMTr7+oa+3RtrANddx9FoWuHC7wbdqKibRSbE4a6rELb/0jPc+mq9WqVjffpe7G7mRbM9egmg9Vp9an5v7FZ937cg9hbRwLwFY094jJybLYO8iYAIyC4Ywxc2AeNMEJ+BQY0xo0JgSC1bRWuchPnlHaKTuG/+zx9pmhP8Ev6+6yKb1N4vkcn7lx3KDWlo1Rgrzjznh2lxx3Fgw7u2E3b+/GkuNKjptL+dr+vMcVXLwVPZFOvOddvBkv3sDzKzluKKUfuJyktZI18h4/3mONbEevaNupeD9dnNXacP8HidY5pxV4WqJ1Geej4Dib50nHTSbn1UP/MlzR0592+sljbW7Rjns2I87GeDEYvWvj9ca8/KT9Er2Sx0/00Ss6vaKnl/ZL+PQeEj6du4RPn0+QqvGklk2f2v8FUEsBAgAAAAAAAAgAIQghAndc12XSAgAAzAcAABMAAAAAAAAAAAAAAAAAAAAAAEFuZHJvaWRNYW5pZmVzdC54bWxQSwUGAAAAAAEAAQBBAAAAAwMAAAAA",
+					KeyID: "testapp-android",
+				},
+			},
+		},
 		{
 			// Sign MAR data
 			"/sign/data",

signer/apk2/apk2.go

@@ -158,14 +158,27 @@ func (s *APK2Signer) SignFile(file []byte, options interface{}) (signer.SignedFi
 	args = append(args,
 		"--key", keyPath.Name(),
 		"--cert", certPath.Name(),
-		"--min-sdk-version", s.minSdkVersion,
 		tmpAPKFile.Name(),
 	)
 	apkSigCmd := exec.Command("java", args...)
 
 	out, err := apkSigCmd.CombinedOutput()
 	if err != nil {
-		return nil, fmt.Errorf("apk2: failed to sign\n%s: %w", out, err)
+		if !bytes.Contains(out, []byte("com.android.apksig.apk.MinSdkVersionException")) {
+			return nil, fmt.Errorf("apk2: failed to sign\n%s: %w", out, err)
+		} else {
+			log.Printf("apk2: APK does not provide minSdkVersion. Attempting to sign again with: --min-sdk-version %s", s.minSdkVersion)
+
+			args = insertIntoSliceAtIndex(args, "--min-sdk-version", len(args)-1)
+			args = insertIntoSliceAtIndex(args, s.minSdkVersion, len(args)-1)
+
+			apkSigCmd = exec.Command("java", args...)
+			out, err = apkSigCmd.CombinedOutput()
+
+			if err != nil {
+				return nil, fmt.Errorf("apk2: failed to sign even when forcing --min-sdk-version\n%s: %w", out, err)
+			}
+		}
 	}
 	log.Debugf("signed as:\n%s\n", string(out))
 
@@ -176,6 +189,19 @@ func (s *APK2Signer) SignFile(file []byte, options interface{}) (signer.SignedFi
 	return signer.SignedFile(signedApk), nil
 }
 
+// go 1.16 doesn't support generics.
+// TODO: Replace string by T in function signature once we use go 1.18+
+func insertIntoSliceAtIndex(destination []string, element string, index int) []string {
+	if len(destination) == index {
+		return append(destination, element)
+	}
+
+	destination = append(destination[:index+1], destination[index:]...) // index < len(a)
+	destination[index] = element
+
+	return destination
+}
+
 // Options are not implemented for this signer
 type Options struct {
 }