最近项目有需求: 只有使用特定签名签的apk才可以安装,其他任何apk都不能安装(root版,使用adb push进去的除外),以供以后参考。
我们已经知道的是:Android对每一个Apk文件都会进行签名,在Apk文件安装时,系统会对其签名信息进行比对,判断程序的完整性,从而决定该Apk文件是否可以安装,在一定程度上达到安全的目的。
给定一个Apk文件,解压,可以看到一个META-INFO文件夹,在该文件夹下有三个文件:分别为MANIFEST.MF、CERT.SF和CERT.RSA。这三个文件分别表征以下含义:
(1)MANIFEST.MF:这是摘要文件。程序遍历Apk包中的所有文件(entry),对非文件夹非签名文件的文件,逐个用SHA1生成摘要信息,再用Base64进行编码。如果你改变了apk包中的文件,那么在apk安装校验时,改变后的文件摘要信息与MANIFEST.MF的检验信息不同,于是程序就不能成功安装。
说明:如果攻击者修改了程序的内容,有重新生成了新的摘要,那么就可以通过验证,所以这是一个非常简单的验证。
(2)CERT.SF:这是对摘要的签名文件。对前一步生成的MANIFEST.MF,使用SHA1-RSA算法,用开发者的私钥进行签名。在安装时只能使用公钥才能解密它。解密之后,将它与未加密的摘要信息(即,MANIFEST.MF文件)进行对比,如果相符,则表明内容没有被异常修改。
说明:在这一步,即使开发者修改了程序内容,并生成了新的摘要文件,但是攻击者没有开发者的私钥,所以不能生成正确的签名文件(CERT.SF)。系统在对程序进行验证的时候,用开发者公钥对不正确的签名文件进行解密,得到的结果和摘要文件(MANIFEST.MF)对应不起来,所以不能通过检验,不能成功安装文件。
(3)CERT.RSA文件中保存了公钥、所采用的加密算法等信息。
说明:系统对签名文件进行解密,所需要的公钥就是从这个文件里取出来的。
结论:从上面的总结可以看出,META-INFO里面的说那个文件环环相扣,从而保证Android程序的安全性。(只是防止开发者的程序不被攻击者修改,如果开发者的公私钥对对攻击者得到或者开发者开发出攻击程序,Android系统都无法检测出来。)
我们将apk包解包,然后使用命令 keytool -printcert -file CERT.RSA 查看CERT.RSA,如图所示:
答案很明显,CERT.RSA文件中存放了关于签名的信息。
android 6.0
不多说,上修改代码:
frameworks/base/services/java/com/android/server/pm/PackageManagerService.java
import java.security.cert.Certificate;
import java.security.MessageDigest;
import java.util.Locale;
// longroey++ start
/**
* Returns the {@link Certificate} fingerprint as returned by keytool
.
*
* @param certificate
* @param hashAlgorithm
*/
public static String getFingerprint(Signature signature, String hashAlgorithm) {
if (signature == null) {
return null;
}
try {
MessageDigest digest = MessageDigest.getInstance(hashAlgorithm);
return toHexadecimalString(digest.digest(signature.toByteArray()));
} catch(NoSuchAlgorithmException e) {
// ignore
}
return null;
}
private static String toHexadecimalString(byte[] value) {
StringBuffer sb = new StringBuffer();
int len = value.length;
for (int i = 0; i
if (num <0x10) {
sb.append('0');
}
sb.append(Integer.toHexString(num));
if (i
}
}
return sb.toString().toUpperCase(Locale.US);
}
// longroey++ end
private void installPackageLI(InstallArgs args, PackageInstalledInfo res) {
......
try {
pp.collectCertificates(pkg, parseFlags);
pp.collectManifestDigest(pkg);
} catch (PackageParserException e) {
res.setError("Failed collect during installPackageLI", e);
return;
}
// longroey++ start
final String CUSTOMIZED_SIGNATURE = "CF:23:86:90:CB:82:73:F1:B1:F8:F0:44:9E:7A:11:47:67:C3:D5:A2";
final Signature[] mSignatures = pkg.mSignatures;
Slog.d(TAG, "signature fingerprint"
+ getFingerprint(mSignatures[0], "SHA-1"));
if (!getFingerprint(mSignatures[0], "SHA-1").equals(CUSTOMIZED_SIGNATURE)) {
res.setError(PackageManager.INSTALL_FAILED_VERIFICATION_FAILURE,
"Signature verification failed");
return;
}
// longroey++ end
/* If the installer passed in a manifest digest, compare it now. */
if (args.manifestDigest != null) {
if (DEBUG_INSTALL) {
final String parsedManifest = pkg.manifestDigest == null ? "null"
: pkg.manifestDigest.toString();
Slog.d(TAG, "Comparing manifests: " + args.manifestDigest.toString() + " vs. "
+ parsedManifest);
}
if (!args.manifestDigest.equals(pkg.manifestDigest)) {
res.setError(INSTALL_FAILED_PACKAGE_CHANGED, "Manifest digest changed");
return;
}
} else if (DEBUG_INSTALL) {
final String parsedManifest = pkg.manifestDigest == null
? "null" : pkg.manifestDigest.toString();
Slog.d(TAG, "manifestDigest was not present, but parser got: " + parsedManifest);
}
......
}
android 7.1
:~/work/source/rsa$ keytool -printcert -file book_MXYF/CERT.RSA
Owner: EMAILADDRESS=android@android.com, CN=Android, OU=Android, O=Android, L=Mountain View, ST=California, C=US
Issuer: EMAILADDRESS=android@android.com, CN=Android, OU=Android, O=Android, L=Mountain View, ST=California, C=US
Serial number: ff0641323cf95512
Valid from: Tue Dec 23 14:43:41 CST 2014 until: Sat May 10 14:43:41 CST 2042
Certificate fingerprints:
MD5: 0E:BA:50:A4:5C:15:B3:5D:97:7D:04:D8:43:79:B3:55
SHA1: 41:79:1C:9B:8F:AF:15:E1:AC:D5:AA:F5:92:10:FD:42:46:7D:82:77
SHA256: 2D:37:0C:21:F5:DF:D5:53:D2:A7:96:31:4B:70:92:5F:B3:8A:DE:EF:90:86:4C:92:0B:BB:BB:12:88:7D:35:22
Signature algorithm name: SHA256withRSA
Version: 3
Extensions:
#1: ObjectId: 2.5.29.35 Criticality=false
AuthorityKeyIdentifier [
KeyIdentifier [
0000: 22 F8 B8 1B C8 57 D6 4A 85 82 6D 0F 8D 54 31 78 "....W.J..m..T1x
0010: 64 A4 CF 0A d...
]
]
#2: ObjectId: 2.5.29.19 Criticality=false
BasicConstraints:[
CA:true
PathLen:2147483647
]
#3: ObjectId: 2.5.29.14 Criticality=false
SubjectKeyIdentifier [
KeyIdentifier [
0000: 22 F8 B8 1B C8 57 D6 4A 85 82 6D 0F 8D 54 31 78 "....W.J..m..T1x
0010: 64 A4 CF 0A d...
]
]
diff --git a/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java b/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java
index 5c4c77e53b..77cdcc784b 100755
--- a/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -318,6 +318,9 @@ import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
+import java.security.cert.Certificate;
+import java.security.MessageDigest;
+import java.util.Locale;
/**
* Keep track of all those APKs everywhere.
@@ -15112,6 +15115,43 @@ public class PackageManagerService extends IPackageManager.Stub {
}
}
+ //xiezx adds start
+ /**
+ * Returns the {@link Certificate} fingerprint as returned by keytool
.
+ *
+ * @param certificate
+ * @param hashAlgorithm
+ */
+ public static String getFingerprint(Signature signature, String hashAlgorithm) {
+ if (signature == null) {
+ return null;
+ }
+ try {
+ MessageDigest digest = MessageDigest.getInstance(hashAlgorithm);
+ return toHexadecimalString(digest.digest(signature.toByteArray()));
+ } catch(NoSuchAlgorithmException e) {
+ // ignore
+ }
+ return null;
+ }
+ private static String toHexadecimalString(byte[] value) {
+ StringBuffer sb = new StringBuffer();
+ int len = value.length;
+ for (int i = 0; i
+ int num = ((int) value[i]) & 0xff;
+ if (num <0x10) {
+ sb.append('0');
+ }
+ sb.append(Integer.toHexString(num));
+ if (i
+ sb.append(':');
+ }
+ }
+ return sb.toString().toUpperCase(Locale.US);
+ }
+ //xiezx adds end
+
+
private void installPackageLI(InstallArgs args, PackageInstalledInfo res) {
final int installFlags = args.installFlags;
final String installerPackageName = args.installerPackageName;
@@ -15207,7 +15247,6 @@ public class PackageManagerService extends IPackageManager.Stub {
return;
}
}
-
try {
// either use what we've been given or parse directly from the APK
if (args.certificates != null) {
@@ -15226,6 +15265,19 @@ public class PackageManagerService extends IPackageManager.Stub {
return;
}
+ //xiezx adds start
+ final String CUSTOMIZED_SIGNATURE = "41:79:1C:9B:8F:AF:15:E1:AC:D5:AA:F5:92:10:FD:42:46:7D:82:77";//"CF:23:86:90:CB:82:73:F1:B1:F8:F0:44:9E:7A:11:47:67:C3:D5:A2";
+
+ final Signature[] mSignatures = pkg.mSignatures;
+ Slog.d(TAG, "xiezx adds signature fingerprint :"
+ + getFingerprint(mSignatures[0], "SHA-1"));
+ if (!getFingerprint(mSignatures[0], "SHA-1").equals(CUSTOMIZED_SIGNATURE)) {
+ res.setError(PackageManager.INSTALL_FAILED_VERIFICATION_FAILURE,
+ "xiezx adds Signature verification failed");
+ return;
+ }
+ //xiezx adds end
+
// Get rid of all references to package scan path via parser.
pp = null;
String oldCodePath = null;
android签名的应用-- 禁止未经授权签名的apk安装
最近项目有需求: 只有使用特定签名签的apk才可以安装,其他任何apk都不能安装(root版,使用adb push进去的除外)。n多度娘、google之后最终实现,把实现代码罗列一下,以供以后参考.
1、使用工具自己制作签名文件,这个签名就是需要提供给apk制作者签名使用的。
可以参考源码路径 build/target/product/security/README 文件
development/tools/make_key testkey ‘/C=CN/ST=ShangHai/L=ShangHai/O=xxx/OU=MTK/CN=China/emailAddress=xxx@qq.com'
2、使用制作好的签名文件签名一个内置的apk,本例采用使用 com.mediatek.factorymode 作为以后签名的对比对象
mediatek/packages/apps/FactoryMode/Android.mk
增加
[java] view plain copy
ifeq ($(XHW_SIGNATURE_CONFIG),yes)
LOCAL_CERTIFICATE := testkey
endif
3、在安装过程中对比签名,如果签名相同的话就继续安装,否则给出一个错误号,弹一个消息框
frameworks/base/services/java/com/android/server/pm/PackageManagerService.java
[java] view plain copy
private PackageParser.Package scanPackageLI(PackageParser.Package pkg,
int parseFlags, int scanMode, long currentTime, UserHandle user) {
...
if (!verifySignaturesLP(pkgSetting, pkg)) {
...
}
//add start
if(com.mediatek.common.featureoption.FeatureOption.XHW_SIGNATURE_CONFIG) {
// is xhw signatures
Signature[] xhwSignatures = getXWHSignatures();
if (xhwSignatures != null) {
if (compareSignatures(xhwSignatures, pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
mLastScanError = PackageManager.INSTALL_FAILED_INVALID_SIGNATURES;
return null;
}
}
}
//add end
// Verify that this new package doesn't have any content providers
// that conflict with existing packages. Only do this if the
// package isn't already installed, since we don't want to break
// things that are installed.
if ((scanMode&SCAN_NEW_INSTALL) != 0) {
...
}
因为在启动是也要走 scanPackageLI 函数,故增加一个变量 mIsInstallApkFlag 判断是否是安装过程
[java] view plain copy
private void installPackageLI(InstallArgs args,
boolean newInstall, PackageInstalledInfo res) {
...
Log.i(TAG, "Start installation for package: " + pkg.packageName);
//add start
if(com.mediatek.common.featureoption.FeatureOption.XHW_SIGNATURE_CONFIG) {
Log.i(TAG, "installPackageLI-111- mIsInstallApkFlag="+mIsInstallApkFlag);
mIsInstallApkFlag = true;
Log.i(TAG, "installPackageLI-222- mIsInstallApkFlag="+mIsInstallApkFlag);
}
//add end
if (replace) {
replacePackageLI(pkg, parseFlags, scanMode, args.user,
installerPackageName, res);
} else {
installNewPackageLI(pkg, parseFlags, scanMode, args.user,
installerPackageName, res);
}
Log.i(TAG, "Installation done for package: " + pkg.packageName);
...
}
增加的函数为:
[java] view plain copy
//add start
private boolean mIsInstallApkFlag = false;
private Signature[] getXWHSignatures(){
if(!mIsInstallApkFlag) return null;
// 取得xhw签名
Signature[] xhwSigns = null;
String packageName = "com.mediatek.factorymode";
/* try {
//PackageInfo xhwPackageInfo = mContext.getPackageManager().getPackageInfo("com.mediatek.factorymode", PackageManager.GET_SIGNATURES); //-- 只能取得已安装的apk 签名
PackageInfo xhwPackageInfo = getPackageInfo("com.mediatek.factorymode", PackageManager.GET_SIGNATURES, Process.SYSTEM_UID);
if(xhwPackageInfo != null){
xhwSigns = xhwPackageInfo.signatures;
}
} catch (Exception e) {
e.printStackTrace();
}
if(xhwSigns != null) Log.e(TAG, "....----getXWHSignatures--xhw_Signs[0]="+xhwSigns[0].toCharsString());
*/
//another method
PackageSetting ps = mSettings.mPackages.get(packageName);
if (ps != null) {
PackageParser.Package pkg = ps.pkg;
if (pkg == null) {
pkg = new PackageParser.Package(packageName);
pkg.applicationInfo.packageName = packageName;
pkg.applicationInfo.flags = ps.pkgFlags | ApplicationInfo.FLAG_IS_DATA_ONLY;
pkg.applicationInfo.publicSourceDir = ps.resourcePathString;
pkg.applicationInfo.sourceDir = ps.codePathString;
pkg.applicationInfo.dataDir = getDataPathForPackage(packageName, 0).getPath();
pkg.applicationInfo.nativeLibraryDir = ps.nativeLibraryPathString;
}
PackageInfo xhwPackageInfo2 = generatePackageInfo(pkg, PackageManager.GET_SIGNATURES, UserHandle.getCallingUserId());
if(xhwPackageInfo2 != null){
xhwSigns = xhwPackageInfo2.signatures;
}
}
// reset flag
mIsInstallApkFlag = false;
return xhwSigns;
}
//add end
上面代码中 PackageManager.INSTALL_FAILED_INVALID_SIGNATURES 是自己增加的错误代码,以供弹出消息使用
[java] view plain copy
+++ frameworks/base/core/java/android/content/pm/PackageManager.java (revision 471)
@@ -553,7 +553,17 @@
*/
public static final int INSTALL_FAILED_VERSION_DOWNGRADE = -25;
+
/**
+ * Installation return code: this is passed to the {@link IPackageInstallObserver} by
+ * {@link #installPackage(android.net.Uri, IPackageInstallObserver, int)} if
+ * the installed package hasn't the expected signature
+ * @hide
+ */
+ public static final int INSTALL_FAILED_INVALID_SIGNATURES = -26; //jimbo add
+
+
+ /**
* Installation parse return code: this is passed to the {@link IPackageInstallObserver} by
* {@link #installPackage(android.net.Uri, IPackageInstallObserver, int)}
* if the parser was given a path that is not a file, or does not end with the expected
4、 弹出错误提示
packages/apps/PackageInstaller/src/com/android/packageinstaller/InstallAppProgress.java
[java] view plain copy
private Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
...
//add start
} else if (msg.arg1 == PackageManager.INSTALL_FAILED_INVALID_SIGNATURES){
// Generic error handling for all other error codes.
centerTextDrawable.setLevel(1);
centerExplanationLabel = getExplanationFromErrorCode(msg.arg1);
centerTextLabel = R.string.install_failed_invalid_signature;
mLaunchButton.setVisibility(View.INVISIBLE);
//add end
} else {
// Generic error handling for all other error codes.
centerTextDrawable.setLevel(1);
centerExplanationLabel = getExplanationFromErrorCode(msg.arg1);
centerTextLabel = R.string.install_failed;
mLaunchButton.setVisibility(View.INVISIBLE);
}
...
其中字串 install_failed_invalid_signature 是新增的字串 例如 “禁止安装,签名不符” 等
windows下给apk签名的方法:
制作一个批处理文件 Auto_Sign.bat 内容:
[java] view plain copy
@echo off
:menu
cls
color 0b
echo.
echo *****************************************************
echo Android platform auto-sign tool V0.2 by imchange
echo Please select your choice then press ENTER
echo *****************************************************
echo.
echo 1. Sign ROM files (*.zip)
echo.
echo 2. Sign program files (*.apk)
echo.
echo 3. Sign ALL (*.zip/*.apk)
echo.
echo 4. Exit
echo.
set /p choice=Please select:
if /i "%choice%"=="1" goto rom
if /i "%choice%"=="2" goto apk
if /i "%choice%"=="3" goto all
if /i "%choice%"=="4" exit
goto menu
:rom
set filename=*.zip
goto sign
:apk
set filename=*.apk
goto sign
:all
set filename=*.zip *.apk
goto sign
:sign
echo.
echo Please wait while signing...
echo The signed files will be placed into subfolder 'Signed'...
echo.
if not exist .\Signed mkdir .\Signed
for /f "delims=" %%i in ('dir/b %filename%') do (
java -jar signapk.jar testkey.x509.pem testkey.pk8 "%%i" ".\Signed\%%~ni_signed%%~xi")
echo.
echo Completed. Press any key to exit.
pause >nul
exit
readme.txt
[java] view plain copy
Android platform ROM/program files auto-sign batch tool
Created by imchange
Usage:
Place your ROM files (*.zip) or program files (*.apk) to this folder, execute Auto_Sign.bat by double click, then select the type of files you want to sign. The signed files are placed into subfolder 'Signed'.
用法:
将ROM文件(*.zip)或程序(*.apk)放到本文件夹,双击执行Auto_Sign.bat,选择要签名的文件类型。签名后的文件放置在Signed文件夹内。
Changelog:
V0.2
-All functions merge into one batch file
-Add select menu
V0.1
-The first version
signapk.jar
[java] view plain copy
package com.android.signapk;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.security.DigestOutputStream;
import java.security.GeneralSecurityException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.MessageDigest;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Enumeration;
import java.util.Map;
import java.util.Map.Entry;
import java.util.jar.Attributes;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.JarOutputStream;
import java.util.jar.Manifest;
import javax.crypto.Cipher;
import javax.crypto.EncryptedPrivateKeyInfo;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.security.auth.x500.X500Principal;
import sun.misc.BASE64Encoder;
import sun.security.pkcs.ContentInfo;
import sun.security.pkcs.PKCS7;
import sun.security.pkcs.SignerInfo;
import sun.security.x509.AlgorithmId;
import sun.security.x509.X500Name;
class SignApk
{
private static X509Certificate readPublicKey(File file)
throws IOException, GeneralSecurityException
{
FileInputStream input = new FileInputStream(file);
try {
CertificateFactory cf = CertificateFactory.getInstance("X.509");
return (X509Certificate)cf.generateCertificate(input);
} finally {
input.close();
}
}
private static String readPassword(File keyFile)
{
System.out.print("Enter password for " + keyFile + " (password will not be hidden): ");
System.out.flush();
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
try {
return stdin.readLine(); } catch (IOException ex) {
}
return null;
}
private static KeySpec decryptPrivateKey(byte[] encryptedPrivateKey, File keyFile)
throws GeneralSecurityException
{
EncryptedPrivateKeyInfo epkInfo;
try
{
epkInfo = new EncryptedPrivateKeyInfo(encryptedPrivateKey);
}
catch (IOException ex) {
return null;
}
char[] password = readPassword(keyFile).toCharArray();
SecretKeyFactory skFactory = SecretKeyFactory.getInstance(epkInfo.getAlgName());
Key key = skFactory.generateSecret(new PBEKeySpec(password));
Cipher cipher = Cipher.getInstance(epkInfo.getAlgName());
cipher.init(2, key, epkInfo.getAlgParameters());
try
{
return epkInfo.getKeySpec(cipher);
} catch (InvalidKeySpecException ex) {
System.err.println("signapk: Password for " + keyFile + " may be bad.");
throw ex;
}
}
private static PrivateKey readPrivateKey(File file)
throws IOException, GeneralSecurityException
{
DataInputStream input = new DataInputStream(new FileInputStream(file));
try {
byte[] bytes = new byte[(int)file.length()];
input.read(bytes);
KeySpec spec = decryptPrivateKey(bytes, file);
if (spec == null) {
spec = new PKCS8EncodedKeySpec(bytes);
}
try
{
return KeyFactory.getInstance("RSA").generatePrivate(spec);
} catch (InvalidKeySpecException ex) {
return KeyFactory.getInstance("DSA").generatePrivate(spec);
}
} finally {
input.close();
}
}
private static Manifest addDigestsToManifest(JarFile jar)
throws IOException, GeneralSecurityException
{
Manifest input = jar.getManifest();
Manifest output = new Manifest();
Attributes main = output.getMainAttributes();
if (input != null) {
main.putAll(input.getMainAttributes());
} else {
main.putValue("Manifest-Version", "1.0");
main.putValue("Created-By", "1.0 (Android SignApk)");
}
BASE64Encoder base64 = new BASE64Encoder();
MessageDigest md = MessageDigest.getInstance("SHA1");
byte[] buffer = new byte[4096];
for (Enumeration e = jar.entries(); e.hasMoreElements(); ) {
JarEntry entry = (JarEntry)e.nextElement();
String name = entry.getName();
if ((!entry.isDirectory()) && (!name.equals("META-INF/MANIFEST.MF"))) {
InputStream data = jar.getInputStream(entry);
int num;
while ((num = data.read(buffer)) > 0) {
md.update(buffer, 0, num);
}
Attributes attr = null;
if (input != null) attr = input.getAttributes(name);
attr = attr != null ? new Attributes(attr) : new Attributes();
attr.putValue("SHA1-Digest", base64.encode(md.digest()));
output.getEntries().put(name, attr);
}
}
return output;
}
private static void writeSignatureFile(Manifest manifest, OutputStream out)
throws IOException, GeneralSecurityException
{
Manifest sf = new Manifest();
Attributes main = sf.getMainAttributes();
main.putValue("Signature-Version", "1.0");
main.putValue("Created-By", "1.0 (Android SignApk)");
BASE64Encoder base64 = new BASE64Encoder();
MessageDigest md = MessageDigest.getInstance("SHA1");
PrintStream print = new PrintStream(new DigestOutputStream(new ByteArrayOutputStream(), md), true, "UTF-8");
manifest.write(print);
print.flush();
main.putValue("SHA1-Digest-Manifest", base64.encode(md.digest()));
Map entries = manifest.getEntries();
for (Map.Entry entry : entries.entrySet())
{
print.print("Name: " + (String)entry.getKey() + "\r\n");
for (Map.Entry att : ((Attributes)entry.getValue()).entrySet()) {
print.print(att.getKey() + ": " + att.getValue() + "\r\n");
}
print.print("\r\n");
print.flush();
Attributes sfAttr = new Attributes();
sfAttr.putValue("SHA1-Digest", base64.encode(md.digest()));
sf.getEntries().put(entry.getKey(), sfAttr);
}
sf.write(out);
}
private static void writeSignatureBlock(Signature signature, X509Certificate publicKey, OutputStream out)
throws IOException, GeneralSecurityException
{
SignerInfo signerInfo = new SignerInfo(new X500Name(publicKey.getIssuerX500Principal().getName()), publicKey.getSerialNumber(), AlgorithmId.get("SHA1"), AlgorithmId.get("RSA"), signature.sign());
PKCS7 pkcs7 = new PKCS7(new AlgorithmId[] { AlgorithmId.get("SHA1") }, new ContentInfo(ContentInfo.DATA_OID, null), new X509Certificate[] { publicKey }, new SignerInfo[] { signerInfo });
pkcs7.encodeSignedData(out);
}
private static void copyFiles(Manifest manifest, JarFile in, JarOutputStream out)
throws IOException
{
byte[] buffer = new byte[4096];
Map entries = manifest.getEntries();
for (String name : entries.keySet()) {
JarEntry inEntry = in.getJarEntry(name);
if (inEntry.getMethod() == 0)
{
out.putNextEntry(new JarEntry(inEntry));
}
else {
out.putNextEntry(new JarEntry(name));
}
InputStream data = in.getInputStream(inEntry);
int num;
while ((num = data.read(buffer)) > 0) {
out.write(buffer, 0, num);
}
out.flush();
}
}
public static void main(String[] args) {
if (args.length != 4) {
System.err.println("Usage: signapk publickey.x509[.pem] privatekey.pk8 input.jar output.jar");
System.exit(2);
}
JarFile inputJar = null;
JarOutputStream outputJar = null;
try
{
X509Certificate publicKey = readPublicKey(new File(args[0]));
PrivateKey privateKey = readPrivateKey(new File(args[1]));
inputJar = new JarFile(new File(args[2]), false);
outputJar = new JarOutputStream(new FileOutputStream(args[3]));
outputJar.setLevel(9);
Manifest manifest = addDigestsToManifest(inputJar);
manifest.getEntries().remove("META-INF/CERT.SF");
manifest.getEntries().remove("META-INF/CERT.RSA");
outputJar.putNextEntry(new JarEntry("META-INF/MANIFEST.MF"));
manifest.write(outputJar);
Signature signature = Signature.getInstance("SHA1withRSA");
signature.initSign(privateKey);
outputJar.putNextEntry(new JarEntry("META-INF/CERT.SF"));
writeSignatureFile(manifest, new SignatureOutputStream(outputJar, signature));
outputJar.putNextEntry(new JarEntry("META-INF/CERT.RSA"));
writeSignatureBlock(signature, publicKey, outputJar);
copyFiles(manifest, inputJar, outputJar);
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
} finally {
try {
if (inputJar != null) inputJar.close();
if (outputJar != null) outputJar.close();
}
catch (IOException e) { e.printStackTrace();
System.exit(1);
}
}
}
private static class SignatureOutputStream extends FilterOutputStream
{
private Signature mSignature;
public SignatureOutputStream(OutputStream out, Signature sig)
{
super();
this.mSignature = sig;
}
public void write(int b) throws IOException
{
try {
this.mSignature.update((byte)b);
} catch (SignatureException e) {
throw new IOException("SignatureException: " + e);
}
super.write(b);
}
public void write(byte[] b, int off, int len) throws IOException
{
try {
this.mSignature.update(b, off, len);
} catch (SignatureException e) {
throw new IOException("SignatureException: " + e);
}
super.write(b, off, len);
}
}
}
附:参考文章
http://www.blogjava.net/zh-weir/archive/2011/07/19/354663.html
Android APK 签名比对
发布过Android应用的朋友们应该都知道,Android APK的发布是需要签名的。签名机制在Android应用和框架中有着十分重要的作用。
例如,Android系统禁止更新安装签名不一致的APK;如果应用需要使用system权限,必须保证APK签名与Framework签名一致,等等。在《APK Crack》一文中,我们了解到,要破解一个APK,必然需要重新对APK进行签名。而这个签名,一般情况无法再与APK原先的签名保持一致。(除非APK原作者的私钥泄漏,那已经是另一个层次的软件安全问题了。)
简单地说,签名机制标明了APK的发行机构。因此,站在软件安全的角度,我们就可以通过比对APK的签名情况,判断此APK是否由“官方”发行,而不是被破解篡改过重新签名打包的“盗版软件”。
Android签名机制
为了说明APK签名比对对软件安全的有效性,我们有必要了解一下Android APK的签名机制。为了更易于大家理解,我们从Auto-Sign工具的一条批处理命令说起。
在《APK Crack》一文中,我们了解到,要签名一个没有签名过的APK,可以使用一个叫作Auto-sign的工具。Auto-sign工具实际运行的是一个叫做Sign.bat的批处理命令。用文本编辑器打开这个批处理文件,我们可以发现,实现签名功能的命令主要是这一行命令:
java -jar signapk.jar testkey.x509.pem testkey.pk8 update.apk update_signed.apk
这条命令的意义是:通过signapk.jar这个可执行jar包,以“testkey.x509.pem”这个公钥文件和“testkey.pk8”这个私钥文件对“update.apk”进行签名,签名后的文件保存为“update_signed.apk”。
对于此处所使用的私钥和公钥的生成方式,这里就不做进一步介绍了。这方面的资料大家可以找到很多。我们这里要讲的是signapk.jar到底做了什么。
signapk.jar是Android源码包中的一个签名工具。由于Android是个开源项目,所以,很高兴地,我们可以直接找到signapk.jar的源码!路径为/build/tools/signapk/SignApk.java。
对比一个没有签名的APK和一个签名好的APK,我们会发现,签名好的APK包中多了一个叫做META-INF的文件夹。里面有三个文件,分别名为MANIFEST.MF、CERT.SF和CERT.RSA。signapk.jar就是生成了这几个文件(其他文件没有任何改变。因此我们可以很容易去掉原有签名信息)。
通过阅读signapk源码,我们可以理清签名APK包的整个过程。
1、 生成MANIFEST.MF文件:
程序遍历update.apk包中的所有文件(entry),对非文件夹非签名文件的文件,逐个生成SHA1的数字签名信息,再用Base64进行编码。具体代码见这个方法:
private static Manifest addDigestsToManifest(JarFile jar)
关键代码如下:
1 for (JarEntry entry: byName.values()) {
2 String name = entry.getName();
3 if (!entry.isDirectory() && !name.equals(JarFile.MANIFEST_NAME) &&
4 !name.equals(CERT_SF_NAME) && !name.equals(CERT_RSA_NAME) &&
5 (stripPattern == null ||!stripPattern.matcher(name).matches())) {
6 InputStream data = jar.getInputStream(entry);
7 while ((num = data.read(buffer)) > 0) {
8 md.update(buffer, 0, num);
9 }
10 Attributes attr = null;
11 if (input != null) attr = input.getAttributes(name);
12 attr = attr != null ? new Attributes(attr) : new Attributes();
13 attr.putValue("SHA1-Digest", base64.encode(md.digest()));
14 output.getEntries().put(name, attr);
15 }
16 }
之后将生成的签名写入MANIFEST.MF文件。关键代码如下:
1 Manifest manifest = addDigestsToManifest(inputJar);
2 je = new JarEntry(JarFile.MANIFEST_NAME);
3 je.setTime(timestamp);
4 outputJar.putNextEntry(je);
5 manifest.write(outputJar);
这里简单介绍下SHA1数字签名。简单地说,它就是一种安全哈希算法,类似于MD5算法。它把任意长度的输入,通过散列算法变成固定长度的输出(这里我们称作“摘要信息”)。你不能仅通过这个摘要信息复原原来的信息。另外,它保证不同信息的摘要信息彼此不同。因此,如果你改变了apk包中的文件,那么在apk安装校验时,改变后的文件摘要信息与MANIFEST.MF的检验信息不同,于是程序就不能成功安装。
2、 生成CERT.SF文件:
对前一步生成的Manifest,使用SHA1-RSA算法,用私钥进行签名。关键代码如下:
1 Signature signature = Signature.getInstance("SHA1withRSA");
2 signature.initSign(privateKey);
3 je = new JarEntry(CERT_SF_NAME);
4 je.setTime(timestamp);
5 outputJar.putNextEntry(je);
6 writeSignatureFile(manifest,
7 new SignatureOutputStream(outputJar, signature));
RSA是一种非对称加密算法。用私钥通过RSA算法对摘要信息进行加密。在安装时只能使用公钥才能解密它。解密之后,将它与未加密的摘要信息进行对比,如果相符,则表明内容没有被异常修改。
3、 生成CERT.RSA文件:
生成MANIFEST.MF没有使用密钥信息,生成CERT.SF文件使用了私钥文件。那么我们可以很容易猜测到,CERT.RSA文件的生成肯定和公钥相关。
CERT.RSA文件中保存了公钥、所采用的加密算法等信息。核心代码如下:
1 je = new JarEntry(CERT_RSA_NAME);
2 je.setTime(timestamp);
3 outputJar.putNextEntry(je);
4 writeSignatureBlock(signature, publicKey, outputJar);
其中writeSignatureBlock的代码如下:
1 private static void writeSignatureBlock(
2 Signature signature, X509Certificate publicKey, OutputStream out)
3 throws IOException, GeneralSecurityException {
4 SignerInfo signerInfo = new SignerInfo(
5 new X500Name(publicKey.getIssuerX500Principal().getName()),
6 publicKey.getSerialNumber(),
7 AlgorithmId.get("SHA1"),
8 AlgorithmId.get("RSA"),
9 signature.sign());
10
11 PKCS7 pkcs7 = new PKCS7(
12 new AlgorithmId[] { AlgorithmId.get("SHA1") },
13 new ContentInfo(ContentInfo.DATA_OID, null),
14 new X509Certificate[] { publicKey },
15 new SignerInfo[] { signerInfo });
16
17 pkcs7.encodeSignedData(out);
18 }
好了,分析完APK包的签名流程,我们可以清楚地意识到:
1、 Android签名机制其实是对APK包完整性和发布机构唯一性的一种校验机制。
2、 Android签名机制不能阻止APK包被修改,但修改后的再签名无法与原先的签名保持一致。(拥有私钥的情况除外)。
3、 APK包加密的公钥就打包在APK包内,且不同的私钥对应不同的公钥。换句话言之,不同的私钥签名的APK公钥也必不相同。所以我们可以根据公钥的对比,来判断私钥是否一致。
APK签名比对的实现方式
好了,通过Android签名机制的分析,我们从理论上证明了通过APK公钥的比对能判断一个APK的发布机构。并且这个发布机构是很难伪装的,我们暂时可以认为是不可伪装的。
有了理论基础后,我们就可以开始实践了。那么如何获取到APK文件的公钥信息呢?因为Android系统安装程序肯定会获取APK信息进行比对,所以我们可以通过Android源码获得一些思路和帮助。
源码中有一个隐藏的类用于APK包的解析。这个类叫PackageParser,路径为frameworks\base\core\java\android\content\pm\PackageParser.java。当我们需要获取APK包的相关信息时,可以直接使用这个类,下面代码就是一个例子函数:
1 private PackageInfo parsePackage(String archiveFilePath, int flags){
2
3 PackageParser packageParser = new PackageParser(archiveFilePath);
4 DisplayMetrics metrics = new DisplayMetrics();
5 metrics.setToDefaults();
6 final File sourceFile = new File(archiveFilePath);
7 PackageParser.Package pkg = packageParser.parsePackage(
8 sourceFile, archiveFilePath, metrics, 0);
9 if (pkg == null) {
10 return null;
11 }
12
13 packageParser.collectCertificates(pkg, 0);
14
15 return PackageParser.generatePackageInfo(pkg, null, flags, 0, 0);
16 }
其中参数archiveFilePath指定APK文件路径;flags需设置PackageManager.GET_SIGNATURES位,以保证返回证书签名信息。
具体如何通过PackageParser获取签名信息在此处不做详述,具体代码请参考PackageParser中的public boolean collectCertificates(Package pkg, int flags)和private Certificate[] loadCertificates(JarFile jarFile, JarEntry je, byte[] readBuffer)方法。至于如何在Android应用开发中使用隐藏的类及方法,可以参看我的这篇文章:《Android应用开发中如何使用隐藏API》。
紧接着,我们就可以通过packageInfo.signatures来访问到APK的签名信息。还需要说明的是 Android中Signature和Java中Certificate的对应关系。它们的关系如下面代码所示:
1 pkg.mSignatures = new Signature[certs.length];
2 for (int i=0; i
3 pkg.mSignatures[i] = new Signature(
4 certs[i].getEncoded());
5 }
也就是说signature = new Signature(certificate.getEncoded()); certificate证书中包含了公钥和证书的其他基本信息。公钥不同,证书肯定互不相同。我们可以通过certificate的getPublicKey方法获取公钥信息。所以比对签名证书本质上就是比对公钥信息。
OK,获取到APK签名证书之后,就剩下比对了。这个简单,功能函数如下所示:
1 private boolean IsSignaturesSame(Signature[] s1, Signature[] s2) {
2 if (s1 == null) {
3 return false;
4 }
5 if (s2 == null) {
6 return false;
7 }
8 HashSet
9 for (Signature sig : s1) {
10 set1.add(sig);
11 }
12 HashSet
13 for (Signature sig : s2) {
14 set2.add(sig);
15 }
16 // Make sure s2 contains all signatures in s1.
17 if (set1.equals(set2)) {
18 return true;
19 }
20 return false;
21 }
APK签名比对的应用场景
经过以上的论述,想必大家已经明白签名比对的原理和我的实现方式了。那么什么时候什么情况适合使用签名对比来保障Android APK的软件安全呢?
个人认为主要有以下三种场景:
1、 程序自检测。在程序运行时,自我进行签名比对。比对样本可以存放在APK包内,也可存放于云端。缺点是程序被破解时,自检测功能同样可能遭到破坏,使其失效。
2、 可信赖的第三方检测。由可信赖的第三方程序负责APK的软件安全问题。对比样本由第三方收集,放在云端。这种方式适用于杀毒安全软件或者APP Market之类的软件下载市场。缺点是需要联网检测,在无网络情况下无法实现功能。(不可能把大量的签名数据放在移动设备本地)。
3、 系统限定安装。这就涉及到改Android系统了。限定仅能安装某些证书的APK。软件发布商需要向系统发布上申请证书。如果发现问题,能追踪到是哪个软件发布商的责任。适用于系统提供商或者终端产品生产商。缺点是过于封闭,不利于系统的开放性。
以上三种场景,虽然各有缺点,但缺点并不是不能克服的。例如,我们可以考虑程序自检测的功能用native method的方法实现等等。软件安全是一个复杂的课题,往往需要多种技术联合使用,才能更好的保障软件不被恶意破