Android 如何讀取未安裝的APK 簽名信息

　　　　以前對於APK的簽名信息獲取，是停留在對已安裝的APK進行相關的操做，可是最近因爲工做須要，就整理了一份關於讀取未安裝的APK 簽名信息的資料，下面很少說直接上代碼：

byte[] signature = getSign(context);
String installPublickey = getPublicKey(signature);//已安裝的應用APK簽名信息獲取
//apkFile ：下載的未安裝APK的安裝包路徑，如：
String apkFile = Environment.getExternalStorageDirectory() + "/download/xxxx.apk";
byte[] unstallSignature = getPackageArchiveInfo(apkFile, PackageManager.GET_ACTIVITIES | PackageManager.GET_SIGNATURES);
String unInstallPublickey = getPublicKey(unstallSignature );//未安裝的APK包的簽名信息獲取

　　　　以上是代碼調用，用的方法在下面貼出：

private static byte[] getSign(Context context) {  
        PackageManager pm = context.getPackageManager();  
        List<PackageInfo> apps = pm.getInstalledPackages(PackageManager.GET_SIGNATURES);  
        Iterator<PackageInfo> iter = apps.iterator();  
        while (iter.hasNext()) {  
            PackageInfo info = iter.next();  
            String packageName = info.packageName;  
            //按包名讀取簽名  
            if (packageName.equals("com.XXX.XXX")) { //根據你本身的包名替換
　　　　　　　　　return info.signatures[0].toByteArray(); 
            }
        }
        return null;  
}

@SuppressWarnings({ "unchecked", "rawtypes" })
public static byte[] getPackageArchiveInfo(String apkFile, int flags){
        
        //這個是與顯示有關的, 裏面涉及到一些像素顯示等等, 咱們使用默認的狀況
        DisplayMetrics metrics = new DisplayMetrics();
        metrics.setToDefaults();
        Object pkgParserPkg = null;
        Class[] typeArgs = null;
        Object[] valueArgs = null;
        try {
            Class<?> packageParserClass = Class.forName("android.content.pm.PackageParser");
            Constructor<?> packageParserConstructor = null;
            Object packageParser = null;
            //因爲SDK版本問題，這裏需作適配，來生成不一樣的構造函數
            if (Build.VERSION.SDK_INT > 20) {
                //無參數 constructor
                packageParserConstructor = packageParserClass.getDeclaredConstructor();
                packageParser = packageParserConstructor.newInstance();
                packageParserConstructor.setAccessible(true);//容許訪問
                
                typeArgs = new Class[2];
                typeArgs[0] = File.class;
                typeArgs[1] = int.class;
                Method pkgParser_parsePackageMtd = packageParserClass.getDeclaredMethod("parsePackage", typeArgs);
                pkgParser_parsePackageMtd.setAccessible(true);

                valueArgs = new Object[2];
                valueArgs[0] = new File(apkFile);
                valueArgs[1] = PackageManager.GET_SIGNATURES;
                pkgParserPkg = pkgParser_parsePackageMtd.invoke(packageParser, valueArgs);
            } else {
                //低版本有參數 constructor
                packageParserConstructor = packageParserClass.getDeclaredConstructor(String.class);
                Object[] fileArgs = { apkFile };
                packageParser = packageParserConstructor.newInstance(fileArgs);
                packageParserConstructor.setAccessible(true);//容許訪問
                
                typeArgs = new Class[4];
                typeArgs[0] = File.class;
                typeArgs[1] = String.class;
                typeArgs[2] = DisplayMetrics.class;
                typeArgs[3] = int.class;

                Method pkgParser_parsePackageMtd = packageParserClass.getDeclaredMethod("parsePackage", typeArgs);
                pkgParser_parsePackageMtd.setAccessible(true);

                valueArgs = new Object[4];
                valueArgs[0] = new File(apkFile);
                valueArgs[1] = apkFile;
                valueArgs[2] = metrics;
                valueArgs[3] = PackageManager.GET_SIGNATURES;
                pkgParserPkg = pkgParser_parsePackageMtd.invoke(packageParser, valueArgs);
            }
            
            typeArgs = new Class[2];
            typeArgs[0] = pkgParserPkg.getClass();
            typeArgs[1] = int.class;
            Method pkgParser_collectCertificatesMtd = packageParserClass.getDeclaredMethod("collectCertificates", typeArgs);
            valueArgs = new Object[2];
            valueArgs[0] = pkgParserPkg;
            valueArgs[1] = PackageManager.GET_SIGNATURES;
            pkgParser_collectCertificatesMtd.invoke(packageParser, valueArgs);
            // 應用程序信息包, 這個公開的, 不過有些函數變量沒公開
            Field packageInfoFld = pkgParserPkg.getClass().getDeclaredField("mSignatures");
            Signature[] info = (Signature[]) packageInfoFld.get(pkgParserPkg);
            return info[0].toByteArray();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
}

public static String getPublicKey(byte[] signature) {  
        try {  
            CertificateFactory certFactory = CertificateFactory.getInstance("X.509");  
            X509Certificate cert = (X509Certificate) certFactory.generateCertificate(new ByteArrayInputStream(signature));  
            return cert.getPublicKey().toString();  
        } catch (CertificateException e) {
            e.printStackTrace();
        }  
        return null;
}

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