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Commit 9c18a2a5 authored by Pedro Loureiro's avatar Pedro Loureiro Committed by satayev
Browse files

Handle install-constraints tag. 

The tag can only be used by allowed packages. The list of the allowed
packages is controlled by configuration on a device, and it gets parsed
in SystemConfig.

A config is expected to have "install-constraints-allowed" tags per
package:

"""
<config>
    <install-constraints-allowed package="foo" />
    <install-constraints-allowed package="bar" />
</config>
"""

Bug: b/232475788
Test: atest AppSecurityTests com.android.server.systemconfig.SystemConfigTest
Change-Id: If3c07ddc1e58a5d16547a50437c939d17b3a4e69
parent b0502bb7

core/java/com/android/server/SystemConfig.java

+20 −0
Original line number Diff line number Diff line
@@ -339,6 +339,8 @@ public class SystemConfig { 
    // A map from package name of vendor APEXes that can be updated to an installer package name

    // allowed to install updates for it.

    private final ArrayMap<String, String> mAllowedVendorApexes = new ArrayMap<>();

    // A set of package names that are allowed to use <install-constraints> manifest tag.

    private final Set<String> mInstallConstraintsAllowlist = new ArraySet<>();



    private String mModulesInstallerPackageName;
@@ -535,6 +537,10 @@ public class SystemConfig { 
        return mAllowedVendorApexes;

    }



    public Set<String> getInstallConstraintsAllowlist() {

        return mInstallConstraintsAllowlist;

    }



    public String getModulesInstallerPackageName() {

        return mModulesInstallerPackageName;

    }
@@ -1455,6 +1461,20 @@ public class SystemConfig { 
                        }

                        XmlUtils.skipCurrentTag(parser);

                    } break;

                    case "install-constraints-allowed": {

                        if (allowAppConfigs) {

                            String packageName = parser.getAttributeValue(null, "package");

                            if (packageName == null) {

                                Slog.w(TAG, "<" + name + "> without package in " + permFile

                                        + " at " + parser.getPositionDescription());

                            } else {

                                mInstallConstraintsAllowlist.add(packageName);

                            }

                        } else {

                            logNotAllowedInPartition(name, permFile, parser);

                        }

                        XmlUtils.skipCurrentTag(parser);

                    } break;

                    default: {

                        Slog.w(TAG, "Tag " + name + " is unknown in "

                                + permFile + " at " + parser.getPositionDescription());

services/core/java/com/android/server/pm/pkg/component/InstallConstraintsTagParser.java

0 → 100644
+131 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2022 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 com.android.server.pm.pkg.component;





import android.content.pm.parsing.result.ParseInput;

import android.content.pm.parsing.result.ParseResult;

import android.content.res.Resources;

import android.content.res.TypedArray;

import android.content.res.XmlResourceParser;

import android.os.Build;

import android.util.ArraySet;



import com.android.internal.R;

import com.android.server.SystemConfig;

import com.android.server.pm.pkg.parsing.ParsingPackage;



import org.xmlpull.v1.XmlPullParser;

import org.xmlpull.v1.XmlPullParserException;



import java.io.IOException;

import java.util.Set;



/**

 * Utility methods for handling the tag {@code <install-constraints/>}

 *

 * @hide

 */

public class InstallConstraintsTagParser {



    private static final String TAG_FINGERPRINT_PREFIX = "fingerprint-prefix";



    /**

     * @hide

     */

    public static ParseResult<ParsingPackage> parseInstallConstraints(

            ParseInput input, ParsingPackage pkg, Resources res, XmlResourceParser parser)

            throws XmlPullParserException, IOException {

        Set<String> allowlist = SystemConfig.getInstance().getInstallConstraintsAllowlist();

        if (!allowlist.contains(pkg.getPackageName())) {

            return input.skip("install-constraints cannot be used by this package");

        }



        ParseResult<Set<String>> prefixes = parseFingerprintPrefixes(input, res, parser);

        if (prefixes.isSuccess()) {

            if (validateFingerprintPrefixes(prefixes.getResult())) {

                return input.success(pkg);

            } else {

                return input.skip(

                        "Install of this package is restricted on this device; device fingerprint"

                                + " does not start with one of the allowed prefixes");

            }

        }

        return input.skip(prefixes.getErrorMessage());

    }



    private static ParseResult<Set<String>> parseFingerprintPrefixes(

            ParseInput input, Resources res, XmlResourceParser parser)

            throws XmlPullParserException, IOException {

        Set<String> prefixes = new ArraySet<>();

        int type;

        while (true) {

            // move to the tag that contains the next prefix

            type = parser.next();

            if (type == XmlPullParser.END_TAG) {

                if (prefixes.size() == 0) {

                    return input.error("install-constraints must contain at least one constraint");

                }

                return input.success(prefixes);

            } else if (type == XmlPullParser.START_TAG) {

                if (parser.getName().equals(TAG_FINGERPRINT_PREFIX)) {

                    ParseResult<String> parsedPrefix =

                            readFingerprintPrefixValue(input, res, parser);

                    if (parsedPrefix.isSuccess()) {

                        prefixes.add(parsedPrefix.getResult());

                    } else {

                        return input.error(parsedPrefix.getErrorMessage());

                    }

                } else {

                    return input.error("Unexpected tag: " + parser.getName());

                }



                // consume the end tag of this attribute

                type = parser.next();

                if (type != XmlPullParser.END_TAG) {

                    return input.error("Expected end tag; instead got " + type);

                }

            }

        }

    }



    private static ParseResult<String> readFingerprintPrefixValue(ParseInput input, Resources res,

            XmlResourceParser parser) {

        TypedArray sa = res.obtainAttributes(parser,

                R.styleable.AndroidManifestInstallConstraintsFingerprintPrefix);

        try {

            String value = sa.getString(

                    R.styleable.AndroidManifestInstallConstraintsFingerprintPrefix_value);

            if (value == null) {

                return input.error("Failed to specify prefix value");

            }

            return input.success(value);

        } finally {

            sa.recycle();

        }

    }



    private static boolean validateFingerprintPrefixes(Set<String> prefixes) {

        String fingerprint = Build.FINGERPRINT;

        for (String prefix : prefixes) {

            if (fingerprint.startsWith(prefix)) {

                return true;

            }

        }

        return false;

    }

}

services/core/java/com/android/server/pm/pkg/parsing/ParsingPackageUtils.java

+2 −8
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ import com.android.server.pm.SharedUidMigration; 
import com.android.server.pm.permission.CompatibilityPermissionInfo;

import com.android.server.pm.pkg.component.ComponentMutateUtils;

import com.android.server.pm.pkg.component.ComponentParseUtils;

import com.android.server.pm.pkg.component.InstallConstraintsTagParser;

import com.android.server.pm.pkg.component.ParsedActivity;

import com.android.server.pm.pkg.component.ParsedActivityUtils;

import com.android.server.pm.pkg.component.ParsedApexSystemService;
@@ -1735,14 +1736,7 @@ public class ParsingPackageUtils { 
    private static ParseResult<ParsingPackage> parseInstallConstraints(

            ParseInput input, ParsingPackage pkg, Resources res, XmlResourceParser parser)

            throws IOException, XmlPullParserException {

        final int depth = parser.getDepth();

        int type;

        while ((type = parser.next()) != XmlPullParser.END_DOCUMENT

                && (type != XmlPullParser.END_TAG

                || parser.getDepth() > depth)) {

            // TODO(b/232475788): call input.skip if constraints check fails

        }

        return input.success(pkg);

        return InstallConstraintsTagParser.parseInstallConstraints(input, pkg, res, parser);

    }



    private static ParseResult<ParsingPackage> parseQueries(ParseInput input, ParsingPackage pkg,

services/tests/servicestests/src/com/android/server/systemconfig/SystemConfigTest.java

+53 −0
Original line number Diff line number Diff line
@@ -336,6 +336,59 @@ public class SystemConfigTest { 
        assertThat(mSysConfig.getAllowedVendorApexes()).isEmpty();

    }



    /**

     * Tests that readPermissions works correctly for the tag: {@code install-constraints-allowed}.

     */

    @Test

    public void readPermissions_installConstraints_successful() throws IOException {

        final String contents =

                "<config>\n"

                        + "    <install-constraints-allowed package=\"com.android.apex1\" />\n"

                        + "</config>";

        final File folder = createTempSubfolder("folder");

        createTempFile(folder, "install-constraints-allowlist.xml", contents);



        readPermissions(folder, /* Grant all permission flags */ ~0);



        assertThat(mSysConfig.getInstallConstraintsAllowlist())

                .containsExactly("com.android.apex1");

    }



    /**

     * Tests that readPermissions works correctly for the tag: {@code install-constraints-allowed}.

     */

    @Test

    public void readPermissions_installConstraints_noPackage() throws IOException {

        final String contents =

                "<config>\n"

                        + "    <install-constraints-allowed/>\n"

                        + "</config>";

        final File folder = createTempSubfolder("folder");

        createTempFile(folder, "install-constraints-allowlist.xml", contents);



        readPermissions(folder, /* Grant all permission flags */ ~0);



        assertThat(mSysConfig.getInstallConstraintsAllowlist()).isEmpty();

    }



    /**

     * Tests that readPermissions works correctly for the tag {@code install-constraints-allowed}

     * without {@link SystemConfig#ALLOW_VENDOR_APEX}.

     */

    @Test

    public void readPermissions_installConstraints_noAppConfigs() throws IOException {

        final String contents =

                "<config>\n"

                        + "    <install-constraints-allowed package=\"com.android.apex1\" />\n"

                        + "</config>";

        final File folder = createTempSubfolder("folder");

        createTempFile(folder, "install-constraints-allowlist.xml", contents);



        readPermissions(folder,  /* Grant all but ALLOW_APP_CONFIGS flag */ ~0x08);



        assertThat(mSysConfig.getInstallConstraintsAllowlist()).isEmpty();

    }



    @Test

    public void readApexPrivAppPermissions_addAllPermissions()

            throws Exception {