经签名的Jar包内包含了以下内容：
- 原Jar包内的class文件和资源文件
- 签名文件 META-INF/*.SF：这是一个文本文件，包含原Jar包内的class文件和资源文件的Hash
- 签名block文件 META-INF/*.DSA：这是一个数据文件，包含签名者的 certificate 和数字签名。其中 certificate 包含了签名者的有关信息和 public key；数字签名是对 *.SF 文件内的 Hash 值使用 private key 加密得来使用 keytool 和 jarsigner 工具进行 Jar 包签名和验证
1、使用 keytool 和 jarsigner 工具进行 Jar 包签名和验证
JDK 提供了 keytool 和 jarsigner 两个工具用来进行 Jar 包签名和验证。
keytool 用来生成和管理 keystore。keystore 是一个数据文件，存储了 key pair 有关的2种数据：private key 和 certificate，而 certificate 包含了 public key。整个 keystore 用一个密码进行保护，keystore 里面的每一对 key pair 单独用一个密码进行保护。每对 key pair 用一个 alias 进行指定，alias 不区分大小写。
keytool 支持的算法是：
- 如果公钥算法为 DSA，则摘要算法使用 SHA-1。这是默认的
- 如果公钥算法为 RSA，则摘要算法采用 MD5
jarsigner 读取 keystore，为 Jar 包进行数字签名。jarsigner 也可以对签名的 Jar 包进行验证。
下面使用 keytool 和 jarsigner 对它进行签名和验证
第1步：用 keytool 生成 keystore
打开CMD窗口，键入如下命令生成keystore文件，其中jamesKeyStore 为公钥秘钥数据文件，james 是alias 的 key pair，keypass 的值123456是秘钥指令，storepass 的值123456是秘钥库指令
| keytool -genkey -alias james -keypass 123456 -validity 3650 -keystore jamesKeyStore -storepass 123456 |
具体生成过程见下图：
第2步：用 jarsigner 对 Jar 包进行签名
使用如下命令可以在CMD窗口中验证签名JAR包
| jarsigner -verify cd-vsb-protect-control-1.0-1.jar |
2、JAVA验证JAR包签名
（1）、JDK对JAR包数字签名验证逻辑
JDK加载包文件提供了两个类JarFile和JarInputStream，两个类由如下构造方法，参数 boolean verify的作用是限制是否要生成JarVerifier对象，JarVerifier类的功能是提供验证JAR包签名的方法。
/**
* Creates a new <code>JarFile</code> to read from the specified
* <code>File</code> object.
* @param file the jar file to be opened for reading
* @param verify whether or not to verify the jar file if
* it is signed.
* @throws IOException if an I/O error has occurred
* @throws SecurityException if access to the file is denied
* by the SecurityManager.
*/
public JarFile(File file, boolean verify) throws IOException {
this(file, verify, ZipFile.OPEN_READ);
} /**
* Creates a new <code>JarFile</code> to read from the specified
* <code>File</code> object in the specified mode. The mode argument
* must be either <tt>OPEN_READ</tt> or <tt>OPEN_READ | OPEN_DELETE</tt>.
*
* @param file the jar file to be opened for reading
* @param verify whether or not to verify the jar file if
* it is signed.
* @param mode the mode in which the file is to be opened
* @throws IOException if an I/O error has occurred
* @throws IllegalArgumentException
* if the <tt>mode</tt> argument is invalid
* @throws SecurityException if access to the file is denied
* by the SecurityManager
* @since 1.3
*/
public JarFile(File file, boolean verify, int mode) throws IOException {
super(file, mode);
this.verify = verify;
}
/**
* Creates a new <code>JarInputStream</code> and reads the optional
* manifest. If a manifest is present and verify is true, also attempts
* to verify the signatures if the JarInputStream is signed.
*
* @param in the actual input stream
* @param verify whether or not to verify the JarInputStream if
* it is signed.
* @exception IOException if an I/O error has occurred
*/
public JarInputStream(InputStream in, boolean verify) throws IOException {
super(in);
this.doVerify = verify; // This implementation assumes the META-INF/MANIFEST.MF entry
// should be either the first or the second entry (when preceded
// by the dir META-INF/). It skips the META-INF/ and then
// "consumes" the MANIFEST.MF to initialize the Manifest object.
JarEntry e = (JarEntry)super.getNextEntry();
if (e != null && e.getName().equalsIgnoreCase("META-INF/"))
e = (JarEntry)super.getNextEntry();
first = checkManifest(e);
} private JarEntry checkManifest(JarEntry e)
throws IOException
{
if (e != null && JarFile.MANIFEST_NAME.equalsIgnoreCase(e.getName())) {
man = new Manifest();
byte bytes[] = getBytes(new BufferedInputStream(this));
man.read(new ByteArrayInputStream(bytes));
closeEntry();
if (doVerify) {
jv = new JarVerifier(bytes);
mev = new ManifestEntryVerifier(man);
}
return (JarEntry)super.getNextEntry();
}
return e;
}
如下代码所示在JarInputStream类对象调用getNextEntry方法获取JarEntry对象时，如果jv对象不为空时，要调用JarVerifier类的beginEntry方法，而此方法最总调用了ManifestEntryVerifier类的mev.setEntry(null, je)方法，
ManifestEntryVerifier类用来做JAR安全证书验证。
public ZipEntry getNextEntry() throws IOException {
JarEntry e;
if (first == null) {
e = (JarEntry)super.getNextEntry();
if (tryManifest) {
e = checkManifest(e);
tryManifest = false;
}
} else {
e = first;
if (first.getName().equalsIgnoreCase(JarIndex.INDEX_NAME))
tryManifest = true;
first = null;
}
if (jv != null && e != null) {
// At this point, we might have parsed all the meta-inf
// entries and have nothing to verify. If we have
// nothing to verify, get rid of the JarVerifier object.
if (jv.nothingToVerify() == true) {
jv = null;
mev = null;
} else {
jv.beginEntry(e, mev);
}
}
return e;
}
/**
* This method scans to see which entry we're parsing and
* keeps various state information depending on what type of
* file is being parsed.
*/
public void beginEntry(JarEntry je, ManifestEntryVerifier mev)
throws IOException
{
if (je == null)
return; if (debug != null) {
debug.println("beginEntry "+je.getName());
} String name = je.getName(); /*
* Assumptions:
* 1. The manifest should be the first entry in the META-INF directory.
* 2. The .SF/.DSA/.EC files follow the manifest, before any normal entries
* 3. Any of the following will throw a SecurityException:
* a. digest mismatch between a manifest section and
* the SF section.
* b. digest mismatch between the actual jar entry and the manifest
*/ if (parsingMeta) {
String uname = name.toUpperCase(Locale.ENGLISH);
if ((uname.startsWith("META-INF/") ||
uname.startsWith("/META-INF/"))) { if (je.isDirectory()) {
mev.setEntry(null, je);
return;
} if (uname.equals(JarFile.MANIFEST_NAME) ||
uname.equals(JarIndex.INDEX_NAME)) {
return;
} if (SignatureFileVerifier.isBlockOrSF(uname)) {
/* We parse only DSA, RSA or EC PKCS7 blocks. */
parsingBlockOrSF = true;
baos.reset();
mev.setEntry(null, je);
return;
} // If a META-INF entry is not MF or block or SF, they should
// be normal entries. According to 2 above, no more block or
// SF will appear. Let's doneWithMeta.
}
} if (parsingMeta) {
doneWithMeta();
} if (je.isDirectory()) {
mev.setEntry(null, je);
return;
} // be liberal in what you accept. If the name starts with ./, remove
// it as we internally canonicalize it with out the ./.
if (name.startsWith("./"))
name = name.substring(2); // be liberal in what you accept. If the name starts with /, remove
// it as we internally canonicalize it with out the /.
if (name.startsWith("/"))
name = name.substring(1); // only set the jev object for entries that have a signature
// (either verified or not)
if (!name.equals(JarFile.MANIFEST_NAME)) {
if (sigFileSigners.get(name) != null ||
verifiedSigners.get(name) != null) {
mev.setEntry(name, je);
return;
}
} // don't compute the digest for this entry
mev.setEntry(null, je); return;
}
（2）、使用java验证JAR包签名
看了上面JDK提供的JAR相关的工具类，我们可以使用JarInputStream类的逻辑来验证，思想是通过空读取JarEntry对象验证包文件中的每个文件数字签名是否被篡改，在获取JarInputStream类对象时设置verify参数值为true，当声明需要做签名验证时在使用jarIn.getNextJarEntry()获取JarEntry对象如果文件被篡改会跑出异常java.lang.SecurityException: SHA-256 digest error for 文件名，这个时候表明JAR签名验证不通过。
，代码实现如下：
public static void verify(String path) throws IOException{
File file = new File(path);
InputStream in = new FileInputStream(file);
JarInputStream jarIn = new JarInputStream(in,true);
while(jarIn.getNextJarEntry() != null){
continue;
}
}