Apktool源码解析——第一篇

著名的apktool是android逆向界用的最普遍的一个工具,这个项目的原始地址在这里http://code.google.com/p/android-apktool/,但是你们都懂的在天朝谷歌是无法访问的,所以直接上github的 https://github.com/brutall/brut.apktool。

在brut.apktool路径是主要代码所在,当然还有brut.apktool.smali是反编译smali的目录,目测还有brut.j.common,brut.j.dir,brut.j.utils是用到java的一些类。

brut.apktool路径下的apktool-cli还不知道是干嘛的,总之下面的apktool-lib正是我们最需要了解的。

 

android目录是利用XmlPullParser实现的专门用于android当中xml的解码工具包。

brut/androlib目录正是我们研究的主题。

com/mindprod/ledatastream目录是le数据支持库。

org/xmlpull/mxp1_serializer目录是XmlPullParser的Xml解析库。

androlib目录一览。

先看一下ApkDecoder这个类。

    public ApkDecoder(File apkFile, Androlib androlib) {
        mAndrolib = androlib;
        setApkFile(apkFile);
    }

    public void setApkFile(File apkFile) {
        mApkFile = new ExtFile(apkFile);
        mResTable = null;
    }
mResTable这个一直很迷惑,很多地方用到了它,但是目前还不住到具体是干嘛的,先不研究这个,继续往下看。
   public void setOutDir(File outDir) throws AndrolibException {
        mOutDir = outDir;
    }

    public void setApi(int api) {
        mApi = api;
    }

这两个方法一看名字就不言而喻,这里就不啰嗦了。多看了几行代码发现,这代码质量相当高,简直不要太优质,比起什么AxmlPrinter2的代码好看多了,呵呵!

下面就是反编译的核心方法了,客观请往下看。

 public void decode() throws AndrolibException, IOException,DirectoryException {
        File outDir = getOutDir();

        if (!mForceDelete && outDir.exists()) {//如果输出目录不是因为删除而不存在就抛出异常
            throw new OutDirExistsException();
        }

        if (!mApkFile.isFile() || !mApkFile.canRead()) {//如果apk文件不是文件类型或者不能读也抛出异常
            throw new InFileNotFoundException();
        }

        try {
            OS.rmdir(outDir);//暂不明
        } catch (BrutException ex) {
            throw new AndrolibException(ex);
        }
        outDir.mkdirs();

        LOGGER.info("Using Apktool " + Androlib.getVersion() + " on " + mApkFile.getName());

        if (hasResources()) {//判断依据mApkFile.getDir().contraincontainsFile("resources.arsc")
            setTargetSdkVersion();
            setAnalysisMode(mAnalysisMode, true);//如果后面的参数为true,将会影响mResTable的取值
            setCompressionMode();//mCompressResources赋值,res.arsc是个zip获取它的压缩模式是否是ZipEntry.DEFLATED默认

            switch (mDecodeResources) {//这里默认是FULL
                case DECODE_RESOURCES_NONE://不解码直接解压到指定res目录
                    mAndrolib.decodeResourcesRaw(mApkFile, outDir);
                    break;
                case DECODE_RESOURCES_FULL://调用androilib.decodearesources方法,其实本质还是调AndrolibResources.decode()方法
                    mAndrolib.decodeResourcesFull(mApkFile, outDir, getResTable());
                    break;
            }
        } else {//没有资源文件
            // if there's no resources.asrc, decode the manifest without looking
            // up attribute references
            if (hasManifest()) {//如果没有res.asrc就不需要查找manifest中的引用属性了
                switch (mDecodeResources) {
                    case DECODE_RESOURCES_NONE:
                        mAndrolib.decodeManifestRaw(mApkFile, outDir);
                        break;
                    case DECODE_RESOURCES_FULL://调mAndRes.decodeManifest(resTable, apkFile, outDir)
                        mAndrolib.decodeManifestFull(mApkFile, outDir,
                                getResTable());
                        break;
                }
            }
        }

        if (hasSources()) {//如果有源文件
            switch (mDecodeSources) {
                case DECODE_SOURCES_NONE://直接复制classes.dex
                    mAndrolib.decodeSourcesRaw(mApkFile, outDir, "classes.dex");
                    break;
                case DECODE_SOURCES_SMALI://反编译成smali,SmaliDecoder.decode()
                    mAndrolib.decodeSourcesSmali(mApkFile, outDir, "classes.dex", mDebug, mDebugLinePrefix, mBakDeb, mApi);
                    break;
                case DECODE_SOURCES_JAVA://反编译jarnew AndrolibJava().decode()
                    mAndrolib.decodeSourcesJava(mApkFile, outDir, mDebug);
                    break;
            }
        }

        if (hasMultipleSources()) {//如果有多个dex
            // foreach unknown dex file in root, lets disassemble it
            Set<String> files = mApkFile.getDirectory().getFiles(true);
            for (String file : files) {//反编译多个dex
                if (file.endsWith(".dex")) {
                    if (! file.equalsIgnoreCase("classes.dex")) {
                        switch(mDecodeSources) {
                            case DECODE_SOURCES_NONE:
                                mAndrolib.decodeSourcesRaw(mApkFile, outDir, file);
                                break;
                            case DECODE_SOURCES_SMALI:
                                mAndrolib.decodeSourcesSmali(mApkFile, outDir, file, mDebug, mDebugLinePrefix, mBakDeb, mApi);
                                break;
                            case DECODE_SOURCES_JAVA:
                                mAndrolib.decodeSourcesJava(mApkFile, outDir, mDebug);
                                break;
                        }
                    }
                }
            }
        }

        mAndrolib.decodeRawFiles(mApkFile, outDir);//复制libs和assets
        mAndrolib.decodeUnknownFiles(mApkFile, outDir, mResTable);//发现一个问题,brutall的代码没有更新,新的在这里https://github.com/iBotPeaches/Apktool
        mAndrolib.writeOriginalFiles(mApkFile, outDir);//输出原始文件,包括AndroidManifest.xml和签名证书
        writeMetaFile();//写如描述文件apktool.yml
    }
下面几个方法不解释咯
   public void setAnalysisMode(boolean mode, boolean pass) throws AndrolibException{
        mAnalysisMode = mode;

        // only set mResTable, once it exists
        if (pass) {
            if (mResTable == null) {
                mResTable = getResTable();
            }
            mResTable.setAnalysisMode(mode);
        }
    }

    public void setCompressionMode() throws AndrolibException, IOException {
        // read the resources.arsc checking for STORED vs DEFLATE
        // this will determine whether we compress on rebuild or not.
        ZipExtFile zef = new ZipExtFile(mApkFile.getAbsolutePath());
        ZipArchiveEntry ze = zef.getEntry("resources.arsc");
        if (ze != null) {
            int compression = ze.getMethod();
            mCompressResources = (compression == ZipEntry.DEFLATED);
        }
        zef.close();
    }

    public void setTargetSdkVersion() throws AndrolibException, IOException {
        if (mResTable == null) {
            mResTable = mAndrolib.getResTable(mApkFile);
        }

        Map<String, String> sdkInfo = mResTable.getSdkInfo();
        if (sdkInfo.get("targetSdkVersion") != null) {
            mApi = Integer.parseInt(sdkInfo.get("targetSdkVersion"));
        }
    }
public ResTable getResTable() throws AndrolibException {
        if (mResTable == null) {
            boolean hasResources = hasResources();
            boolean hasManifest = hasManifest();
            if (! (hasManifest || hasResources)) {//一个apk文件不能没有AndroidManifest.xml和resource.arsc,否则就不是合法的apk文件
                throw new AndrolibException(
                        "Apk doesn't contain either AndroidManifest.xml file or resources.arsc file");
            }
            AndrolibResources.sKeepBroken = mKeepBrokenResources;
            mResTable = mAndrolib.getResTable(mApkFile, hasResources);
        }
        return mResTable;
    }

 

End!
 补充:
在decode()中有个writeMetaFile()方法没讲到,这里再看看。
   private void writeMetaFile() throws AndrolibException {
        Map<String, Object> meta = new LinkedHashMap<String, Object>();
        meta.put("version", Androlib.getVersion());//静态方法?
        meta.put("apkFileName", mApkFile.getName());//apk名称

        if (mDecodeResources != DECODE_RESOURCES_NONE && (hasManifest() || hasResources())) {//如果要反编译资源并且有资源文件或者manifest文件
            meta.put("isFrameworkApk", mAndrolib.isFrameworkApk(getResTable()));
            putUsesFramework(meta);
            putSdkInfo(meta);
            putPackageInfo(meta);
            putVersionInfo(meta);
            putCompressionInfo(meta);
        }
        putUnknownInfo(meta);//加入Unknown文件目录说明
     mAndrolib.writeMetaFile(mOutDir, meta); //将meta数据写入apktool.yml写入到输出目录
  }
  private void putUsesFramework(Map<String, Object> meta) throws AndrolibException {
        Set<ResPackage> pkgs = getResTable().listFramePackages();
        if (pkgs.isEmpty()) {
            return;
        }

        Integer[] ids = new Integer[pkgs.size()];
        int i = 0;
        for (ResPackage pkg : pkgs) {
            ids[i++] = pkg.getId();
        }
        Arrays.sort(ids);

        Map<String, Object> uses = new LinkedHashMap<String, Object>();
        uses.put("ids", ids);//ids

        if (mAndrolib.apkOptions.frameworkTag != null) {//tag
            uses.put("tag", mAndrolib.apkOptions.frameworkTag);
        }

        meta.put("usesFramework", uses);
    }

    private void putSdkInfo(Map<String, Object> meta) throws AndrolibException {
        Map<String, String> info = getResTable().getSdkInfo();//ResTable可以获取sdk信息?
        if (info.size() > 0) {
            meta.put("sdkInfo", info);
        }
    }

    private void putPackageInfo(Map<String, Object> meta) throws AndrolibException {
        String renamed = getResTable().getPackageRenamed();//还可以获取package信息?
        String original = getResTable().getPackageOriginal();
        int id = getResTable().getPackageId();

        HashMap<String, String> packages = new HashMap<String, String>();

        // only put rename-manifest-package into apktool.yml, if the change will be required
        if (!renamed.equalsIgnoreCase(original)) {
            packages.put("rename-manifest-package", renamed);
        }
        packages.put("forced-package-id", String.valueOf(id));
        meta.put("packageInfo", packages);
    }

    private void putVersionInfo(Map<String, Object> meta) throws AndrolibException {
        Map<String, String> info = getResTable().getVersionInfo();//获取版本信息
        if (info.size() > 0) {
            meta.put("versionInfo", info);
        }
    }

    private void putUnknownInfo(Map<String, Object> meta) throws AndrolibException {
        Map<String,String> info = mAndrolib.mResUnknownFiles.getUnknownFiles();//Androlib会收集Unknwn文件
        if (info.size() > 0) {
            meta.put("unknownFiles", info);
        }
    }

    private void putCompressionInfo(Map<String, Object> meta) throws AndrolibException {
        meta.put("compressionType", getCompressionType());//压缩方式
    }

 

 

 

posted @ 2014-12-10 23:40  bvin  阅读(5681)  评论(0编辑  收藏