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Commit bef47a35 authored by Ryan Mitchell's avatar Ryan Mitchell
Browse files

StringBlock incremental hardening default values 

When a string cannot be retrieved from a StringBlock due to pages of
the StringPool missing, rather than throwing an
IndexOutOfBoundsException, compute a default value rather that
abides by the API contacts of the functions that use the StringBlock.

IndexOutOfBoundsExceptions are not really documented as a possible
exception that can be thrown from APIs that use StringBlock because
it indicates that the binary resource table was built incorrectly.

Returning default values is much less likely to break applications
that fetch the resources of incrementally installed applications than
throwing IndexOutOfBoundsExceptions where they would normally not be
expected.

Bug: 188174746
Test: atest ResourcesHardeningTest
Change-Id: I58fe754fb446fefc031ddba19e290830fdd6d015
parent 72cd5f15

core/java/android/content/res/ApkAssets.java

+2 −1
Original line number Diff line number Diff line
@@ -334,13 +334,14 @@ public final class ApkAssets { 
        }

    }



    @Nullable

    CharSequence getStringFromPool(int idx) {

        if (mStringBlock == null) {

            return null;

        }



        synchronized (this) {

            return mStringBlock.get(idx);

            return mStringBlock.getSequence(idx);

        }

    }

core/java/android/content/res/AssetManager.java

+7 −2
Original line number Diff line number Diff line
@@ -550,7 +550,9 @@ public final class AssetManager implements AutoCloseable { 
                    outValue.changingConfigurations);



            if (outValue.type == TypedValue.TYPE_STRING) {

                outValue.string = getPooledStringForCookie(cookie, outValue.data);

                if ((outValue.string = getPooledStringForCookie(cookie, outValue.data)) == null) {

                    return false;

                }

            }

            return true;

        }
@@ -731,7 +733,9 @@ public final class AssetManager implements AutoCloseable { 
                    outValue.changingConfigurations);



            if (outValue.type == TypedValue.TYPE_STRING) {

                outValue.string = getPooledStringForCookie(cookie, outValue.data);

                if ((outValue.string = getPooledStringForCookie(cookie, outValue.data)) == null) {

                    return false;

                }

            }

            return true;

        }
@@ -833,6 +837,7 @@ public final class AssetManager implements AutoCloseable { 
        }

    }



    @Nullable

    CharSequence getPooledStringForCookie(int cookie, int id) {

        // Cookies map to ApkAssets starting at 1.

        return getApkAssets()[cookie - 1].getStringFromPool(id);

core/java/android/content/res/StringBlock.java

+27 −2
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ 


package android.content.res;



import android.annotation.NonNull;

import android.annotation.Nullable;

import android.compat.annotation.UnsupportedAppUsage;

import android.graphics.Color;

import android.graphics.Paint;
@@ -86,8 +88,19 @@ public final class StringBlock implements Closeable { 
                + ": " + nativeGetSize(mNative));

    }



    /**

     * @deprecated use {@link #getSequence(int)} which can return null when a string cannot be found

     *             due to incremental installation.

     */

    @Deprecated

    @UnsupportedAppUsage

    public CharSequence get(int idx) {

        CharSequence seq = getSequence(idx);

        return seq == null ? "" : seq;

    }



    @Nullable

    public CharSequence getSequence(int idx) {

        synchronized (this) {

            if (mStrings != null) {

                CharSequence res = mStrings[idx];
@@ -108,6 +121,9 @@ public final class StringBlock implements Closeable { 
                }

            }

            String str = nativeGetString(mNative, idx);

            if (str == null) {

                return null;

            }

            CharSequence res = str;

            int[] style = nativeGetStyle(mNative, idx);

            if (localLOGV) Log.v(TAG, "Got string: " + str);
@@ -133,6 +149,9 @@ public final class StringBlock implements Closeable { 
                    }



                    String styleTag = nativeGetString(mNative, styleId);

                    if (styleTag == null) {

                        return null;

                    }



                    if (styleTag.equals("b")) {

                        mStyleIDs.boldId = styleId;
@@ -161,8 +180,10 @@ public final class StringBlock implements Closeable { 


                res = applyStyles(str, style, mStyleIDs);

            }

            if (res != null) {

                if (mStrings != null) mStrings[idx] = res;

                else mSparseStrings.put(idx, res);

            }

            return res;

        }

    }
@@ -203,6 +224,7 @@ public final class StringBlock implements Closeable { 
        private int marqueeId = -1;

    }



    @Nullable

    private CharSequence applyStyles(String str, int[] style, StyleIDs ids) {

        if (style.length == 0)

            return str;
@@ -260,6 +282,9 @@ public final class StringBlock implements Closeable { 
                               Spannable.SPAN_INCLUSIVE_INCLUSIVE);

            } else {

                String tag = nativeGetString(mNative, type);

                if (tag == null) {

                    return null;

                }



                if (tag.startsWith("font;")) {

                    String sub;

core/java/android/content/res/TypedArray.java

+1 −0
Original line number Diff line number Diff line
@@ -1376,6 +1376,7 @@ public class TypedArray implements AutoCloseable { 
        return true;

    }



    @Nullable

    private CharSequence loadStringValueAt(int index) {

        final int[] data = mData;

        final int cookie = data[index + STYLE_ASSET_COOKIE];

core/java/android/content/res/XmlBlock.java

+32 −12
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ package android.content.res; 
import static android.content.res.Resources.ID_NULL;



import android.annotation.AnyRes;

import android.annotation.NonNull;

import android.annotation.Nullable;

import android.compat.annotation.UnsupportedAppUsage;

import android.os.Build;
@@ -161,9 +162,10 @@ public final class XmlBlock implements AutoCloseable { 
        public int getDepth() {

            return mDepth;

        }

        @Nullable

        public String getText() {

            int id = nativeGetText(mParseState);

            return id >= 0 ? mStrings.get(id).toString() : null;

            return id >= 0 ? getSequenceString(mStrings.getSequence(id)) : null;

        }

        public int getLineNumber() {

            return nativeGetLineNumber(mParseState);
@@ -189,25 +191,29 @@ public final class XmlBlock implements AutoCloseable { 
            }

            return chars;

        }

        @Nullable

        public String getNamespace() {

            int id = nativeGetNamespace(mParseState);

            return id >= 0 ? mStrings.get(id).toString() : "";

            return id >= 0 ? getSequenceString(mStrings.getSequence(id)) : "";

        }

        @Nullable

        public String getName() {

            int id = nativeGetName(mParseState);

            return id >= 0 ? mStrings.get(id).toString() : null;

            return id >= 0 ? getSequenceString(mStrings.getSequence(id)) : null;

        }

        @NonNull

        public String getAttributeNamespace(int index) {

            int id = nativeGetAttributeNamespace(mParseState, index);

            if (DEBUG) System.out.println("getAttributeNamespace of " + index + " = " + id);

            if (id >= 0) return mStrings.get(id).toString();

            if (id >= 0) return getSequenceString(mStrings.getSequence(id));

            else if (id == -1) return "";

            throw new IndexOutOfBoundsException(String.valueOf(index));

        }

        @NonNull

        public String getAttributeName(int index) {

            int id = nativeGetAttributeName(mParseState, index);

            if (DEBUG) System.out.println("getAttributeName of " + index + " = " + id);

            if (id >= 0) return mStrings.get(id).toString();

            if (id >= 0) return getSequenceString(mStrings.getSequence(id));

            throw new IndexOutOfBoundsException(String.valueOf(index));

        }

        public String getAttributePrefix(int index) {
@@ -220,10 +226,11 @@ public final class XmlBlock implements AutoCloseable { 
        public int getAttributeCount() {

            return mEventType == START_TAG ? nativeGetAttributeCount(mParseState) : -1;

        }

        @NonNull

        public String getAttributeValue(int index) {

            int id = nativeGetAttributeStringValue(mParseState, index);

            if (DEBUG) System.out.println("getAttributeValue of " + index + " = " + id);

            if (id >= 0) return mStrings.get(id).toString();

            if (id >= 0) return getSequenceString(mStrings.getSequence(id));



            // May be some other type...  check and try to convert if so.

            int t = nativeGetAttributeDataType(mParseState, index);
@@ -390,7 +397,7 @@ public final class XmlBlock implements AutoCloseable { 
            int v = nativeGetAttributeData(mParseState, idx);

            if (t == TypedValue.TYPE_STRING) {

                return XmlUtils.convertValueToList(

                    mStrings.get(v), options, defaultValue);

                    mStrings.getSequence(v), options, defaultValue);

            }

            return v;

        }
@@ -444,14 +451,15 @@ public final class XmlBlock implements AutoCloseable { 
            }

            throw new RuntimeException("not a float!");

        }



        @Nullable

        public String getIdAttribute() {

            int id = nativeGetIdAttribute(mParseState);

            return id >= 0 ? mStrings.get(id).toString() : null;

            return id >= 0 ? getSequenceString(mStrings.getSequence(id)) : null;

        }

        @Nullable

        public String getClassAttribute() {

            int id = nativeGetClassAttribute(mParseState);

            return id >= 0 ? mStrings.get(id).toString() : null;

            return id >= 0 ? getSequenceString(mStrings.getSequence(id)) : null;

        }



        public int getIdAttributeResourceValue(int defaultValue) {
@@ -463,6 +471,17 @@ public final class XmlBlock implements AutoCloseable { 
            return nativeGetStyleAttribute(mParseState);

        }



        private String getSequenceString(@Nullable CharSequence str) {

            if (str == null) {

                // A value of null retrieved from a StringPool indicates that retrieval of the

                // string failed due to incremental installation. The presence of all the XmlBlock

                // data is verified when it is created, so this exception must not be possible.

                throw new IllegalStateException("Retrieving a string from the StringPool of an"

                        + " XmlBlock should never fail");

            }

            return str.toString();

        }



        public void close() {

            synchronized (mBlock) {

                if (mParseState != 0) {
@@ -477,8 +496,9 @@ public final class XmlBlock implements AutoCloseable { 
            close();

        }



        @Nullable

        /*package*/ final CharSequence getPooledString(int id) {

            return mStrings.get(id);

            return mStrings.getSequence(id);

        }



        @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)