android/content/integrity/InstallerAllowedByManifestFormula.java

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.content.integrity;

import android.annotation.NonNull;
import android.os.Parcel;
import android.os.Parcelable;

import java.util.Map;

/**
 * An atomic formula that evaluates to true if the installer of the current install is specified in
 * the "allowed installer" field in the android manifest. Note that an empty "allowed installer" by
 * default means containing all possible installers.
 *
 * @hide
 */
public class InstallerAllowedByManifestFormula extends IntegrityFormula implements Parcelable {

    public static final String INSTALLER_CERTIFICATE_NOT_EVALUATED = "";

    public InstallerAllowedByManifestFormula() {
    }

    private InstallerAllowedByManifestFormula(Parcel in) {
    }

    @NonNull
    public static final Creator<InstallerAllowedByManifestFormula> CREATOR =
            new Creator<InstallerAllowedByManifestFormula>() {
                @Override
                public InstallerAllowedByManifestFormula createFromParcel(Parcel in) {
                    return new InstallerAllowedByManifestFormula(in);
                }

                @Override
                public InstallerAllowedByManifestFormula[] newArray(int size) {
                    return new InstallerAllowedByManifestFormula[size];
                }
            };

    @Override
    public int getTag() {
        return IntegrityFormula.INSTALLER_ALLOWED_BY_MANIFEST_FORMULA_TAG;
    }

    @Override
    public boolean matches(AppInstallMetadata appInstallMetadata) {
        Map<String, String> allowedInstallersAndCertificates =
                appInstallMetadata.getAllowedInstallersAndCertificates();
        return allowedInstallersAndCertificates.isEmpty()
                || installerInAllowedInstallersFromManifest(
                appInstallMetadata, allowedInstallersAndCertificates);
    }

    @Override
    public boolean isAppCertificateFormula() {
        return false;
    }

    @Override
    public boolean isInstallerFormula() {
        return true;
    }

    private static boolean installerInAllowedInstallersFromManifest(
            AppInstallMetadata appInstallMetadata,
            Map<String, String> allowedInstallersAndCertificates) {
        String installerPackage = appInstallMetadata.getInstallerName();

        if (!allowedInstallersAndCertificates.containsKey(installerPackage)) {
            return false;
        }

        // If certificate is not specified in the manifest, we do not check it.
        if (!allowedInstallersAndCertificates.get(installerPackage)
                .equals(INSTALLER_CERTIFICATE_NOT_EVALUATED)) {
            return appInstallMetadata.getInstallerCertificates()
                    .contains(
                            allowedInstallersAndCertificates
                                    .get(appInstallMetadata.getInstallerName()));
        }

        return true;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
    }
}