首先介绍一下jasypt的使用方法

版本对应的坑

使用的时候还是遇到一个坑，就是jasypt的版本与spring boot版本存在对应情况。可以看到jasypt是区分java7和java8的，也存在依赖spring版本的情况。

自己尝试了一下

在使用jasypt-spring-boot-starter的前提下

jasypt版本	springboot版本
2.1.0	2.1.0
1.5	1.4.2
1.5	1.5.3
1.8	1.4.2

所以如果引入maven之后启动系统报错，那么可以根据版本对应情况这个角度进行排查。

关键技术点

下面说一下jasypt的两个关键的技术实现点

一是如何实现对spring环境中包含的PropertySource对象实现加密感知的

二是其默认的PBEWITHMD5ANDDES算法是如何工作的，并澄清一下在使用jasypt的时候最常遇到的一个疑问：既然你的password也配置在properties文件中，那么我拿到了加密的密文和password，不是可以直接解密吗？

源码解析

总结来说：其通过BeanFactoryPostProcessor#postProcessBeanFactory方法，获取所有的propertySource对象，将所有propertySource都会重新包装成新的EncryptablePropertySourceWrapper

解密的时候，也是使用EncryptablePropertySourceWrapper#getProperty方法，如果通过 prefixes/suffixes 包裹的属性，那么返回解密后的值；如果没有被包裹，那么返回原生的值。从源头开始走起：

将jar包引入到spring boot中

spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.ulisesbocchio.jasyptspringboot.JasyptSpringBootAutoConfiguration

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这里补充一下spring boot @EnableAutoConfiguration的原理。

@EnableAutoConfiguration原理

@EnableAutoConfiguration注解@Import(AutoConfigurationImportSelector.class)

这个配置类实现了ImportSelector接口，重写其selectImports方法

List<String> configurations = getCandidateConfigurations(annotationMetadata,
      attributes);

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getCandidateConfigurations方法，会从classpath中搜索所有META-INF/spring.factories配置文件，然后，将其中org.springframework.boot.autoconfigure.EnableAutoConfiguration key对应的配置项加载到spring容器中。这样就实现了在spring boot中加载外部项目的bean或者第三方jar中的bean。

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
      AnnotationAttributes attributes) {
   List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
         getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
   Assert.notEmpty(configurations,
         "No auto configuration classes found in META-INF/spring.factories. If you "
               + "are using a custom packaging, make sure that file is correct.");
   return configurations;
}

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其内部实现的关键点有：

1. ImportSelector 该接口的方法的返回值都会被纳入到spring容器的管理中

2. SpringFactoriesLoader 该类可以从classpath中搜索所有META-INF/spring.factories配置文件，读取配置

@EnableAutoConfiguration注解中有spring.boot.enableautoconfiguration=true就开启，默认为true，可以在application.properties中设置此开关项

exclude()方法是根据类排除，excludeName是根据类名排除

在spring-boot-autoconfigure jar中，META-INF中有一个spring.factories文件，其中配置了spring-boot所有的自动配置参数，如GsonAutoConfiguration，配合@ConditionalOnClass(Gson.class)，可以实现如果Gson bean存在，就启动自动注入，否则就不启用此注入的灵活配置

好了，有了上面的基础知识，我们就关心JasyptSpringBootAutoConfiguration

JasyptSpringBootAutoConfiguration

其@Import EnableEncryptablePropertySourcesConfiguration

关注两个地方

一是其@Import的StringEncryptorConfiguration.class

如果没有自定义的EncryptorBean，即jasyptStringEncryptor bean，那么就注册默认的jasyptStringEncryptor bean

@Conditional(OnMissingEncryptorBean.class)
@Bean(name = ENCRYPTOR_BEAN_PLACEHOLDER)
public StringEncryptor stringEncryptor(Environment environment) {
    String encryptorBeanName = environment.resolveRequiredPlaceholders(ENCRYPTOR_BEAN_PLACEHOLDER);
    LOG.info("String Encryptor custom Bean not found with name '{}'. Initializing String Encryptor based on properties with name '{}'",
             encryptorBeanName, encryptorBeanName);
    return new LazyStringEncryptor(() -> {
        PooledPBEStringEncryptor encryptor = new PooledPBEStringEncryptor();
        SimpleStringPBEConfig config = new SimpleStringPBEConfig();
        config.setPassword(getRequiredProperty(environment, "jasypt.encryptor.password"));
        config.setAlgorithm(getProperty(environment, "jasypt.encryptor.algorithm", "PBEWithMD5AndDES"));
        config.setKeyObtentionIterations(getProperty(environment, "jasypt.encryptor.keyObtentionIterations", "1000"));
        config.setPoolSize(getProperty(environment, "jasypt.encryptor.poolSize", "1"));
        config.setProviderName(getProperty(environment, "jasypt.encryptor.providerName", "SunJCE"));
        config.setSaltGeneratorClassName(getProperty(environment, "jasypt.encryptor.saltGeneratorClassname", "org.jasypt.salt.RandomSaltGenerator"));
        config.setStringOutputType(getProperty(environment, "jasypt.encryptor.stringOutputType", "base64"));
        encryptor.setConfig(config);
        return encryptor;
    });
}

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StringEncryptor接口提供了加密和解密的方法

我们可以自定义StringEncryptor，如

@Configuration
public class JasyptConfig {

    @Bean(name = "jasypt.encryptor.bean:jasyptStringEncryptor")
    public StringEncryptor stringEncryptor() {
        PooledPBEStringEncryptor encryptor = new PooledPBEStringEncryptor();
        SimpleStringPBEConfig config = new SimpleStringPBEConfig();
        config.setPassword("password");
        config.setAlgorithm("PBEWithMD5AndDES");
        config.setKeyObtentionIterations("1000");
        config.setPoolSize("1");
        config.setProviderName("SunJCE");
        config.setSaltGeneratorClassName("org.jasypt.salt.RandomSaltGenerator");
        config.setStringOutputType("base64");
        encryptor.setConfig(config);
        return encryptor;
    }
}

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二是其对spring环境中包含的PropertySource对象的处理

@Configuration
@Import(StringEncryptorConfiguration.class)
public class EnableEncryptablePropertySourcesConfiguration implements EnvironmentAware {

    private static final Logger LOG = LoggerFactory.getLogger(EnableEncryptablePropertySourcesConfiguration.class);
    private ConfigurableEnvironment environment;

    @Bean
    public EnableEncryptablePropertySourcesPostProcessor enableEncryptablePropertySourcesPostProcessor() {
        boolean proxyPropertySources = environment.getProperty("jasypt.encryptor.proxyPropertySources", Boolean.TYPE, false);
        InterceptionMode interceptionMode = proxyPropertySources ? InterceptionMode.PROXY : InterceptionMode.WRAPPER;
        return new EnableEncryptablePropertySourcesPostProcessor(environment, interceptionMode);
    }

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = (ConfigurableEnvironment) environment;
    }
}

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其提供了两种模式来创建 分别为proxy和wrapper 默认情况下interceptionMode为wrapper

下面就是关键了，new了一个EnableEncryptablePropertySourcesPostProcessor

其implements BeanFactoryPostProcessor

这里又需要两个背景知识

一是AbstractApplicationContext的refresh方法

是启动spring容器的关键方法

// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);

// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);

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来注册我们下面的postProcessors

二是BeanFactoryPostProcessor接口的作用

BeanFactoryPostProcessor接口提供了postProcessBeanFactory方法，在容器初始化之后执行一次

invokeBeanFactoryPostProcessors，获取的手动注册的BeanFactoryPostProcessor

/**
 * Invoke the given BeanFactoryPostProcessor beans.
 */
private static void invokeBeanFactoryPostProcessors(
      Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

   for (BeanFactoryPostProcessor postProcessor : postProcessors) {
      postProcessor.postProcessBeanFactory(beanFactory);
   }
}

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可以看到postProcessors有4个

接下来看关键的EnableEncryptablePropertySourcesPostProcessor

EnableEncryptablePropertySourcesPostProcessor

public class EnableEncryptablePropertySourcesPostProcessor implements BeanFactoryPostProcessor, ApplicationListener<ApplicationEvent>, Ordered {

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其实现了BeanFactoryPostProcessor以及Ordered接口

其中getOrder方法 让这个jasypt定义的BeanFactoryPostProcessor的初始化顺序最低，即最后初始化

我们知道spring中排序分为两种PriorityOrdered 和Ordered接口，一般来说就是PriorityOrdered 优于Ordered 其次都是按照order大小来的排序

我们就知道了接下来就执行EnableEncryptablePropertySourcesPostProcessor的postProcessBeanFactory方法，

@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    LOG.info("Post-processing PropertySource instances");
    MutablePropertySources propSources = environment.getPropertySources();
    StreamSupport.stream(propSources.spliterator(), false)
        .filter(ps -> !(ps instanceof EncryptablePropertySource))
        .map(s -> makeEncryptable(s, beanFactory))
        .collect(toList())
        .forEach(ps -> propSources.replace(ps.getName(), ps));
}

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接下来，获取所有的propertySource对象

然后用stream方式遍历，如果是通过jasypt加密的，那么来执行方法makeEncryptable，使得propertySource对象具备加密解密的能力

private <T> PropertySource<T> makeEncryptable(PropertySource<T> propertySource, ConfigurableListableBeanFactory registry) {
    StringEncryptor encryptor = registry.getBean(environment.resolveRequiredPlaceholders(ENCRYPTOR_BEAN_PLACEHOLDER), StringEncryptor.class);
    PropertySource<T> encryptablePropertySource = interceptionMode == InterceptionMode.PROXY
            ? proxyPropertySource(propertySource, encryptor) : instantiatePropertySource(propertySource, encryptor);
    LOG.info("Converting PropertySource {} [{}] to {}", propertySource.getName(), propertySource.getClass().getName(),
             AopUtils.isAopProxy(encryptablePropertySource) ? "AOP Proxy" : encryptablePropertySource.getClass().getSimpleName());
    return encryptablePropertySource;
}

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首先获取StringEncrypt Bean，然后执行instantiatePropertySource方法。

private <T> PropertySource<T> instantiatePropertySource(PropertySource<T> propertySource, StringEncryptor encryptor) {
    PropertySource<T> encryptablePropertySource;
    if (propertySource instanceof MapPropertySource) {
        encryptablePropertySource = (PropertySource<T>) new EncryptableMapPropertySourceWrapper((MapPropertySource) propertySource, encryptor);
    } else if (propertySource.getClass().getName().equals("org.springframework.boot.context.config.ConfigFileApplicationListener$ConfigurationPropertySources")) {
        //Some Spring Boot code actually casts property sources to this specific type so must be proxied.
        encryptablePropertySource = proxyPropertySource(propertySource, encryptor);
    } else if (propertySource instanceof EnumerablePropertySource) {
        encryptablePropertySource = new EncryptableEnumerablePropertySourceWrapper<>((EnumerablePropertySource) propertySource, encryptor);
    } else {
        encryptablePropertySource = new EncryptablePropertySourceWrapper<>(propertySource, encryptor);
    }
    return encryptablePropertySource;
}

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可以看到将所有propertySource都会重新包装成新的EncryptablePropertySourceWrapper

log日志：将上面的6个对象包装一下

最后的application.properties中的配置项结果

完整的转换完成后的EncryptablePropertySourceWrapper

到这里就注册postProcessor完成了，而且每个PropertySource warpped，具备了加密解密的能力，然后继续回到AbstractApplicationContext的流程

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

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具体的解密过程

当spring boot项目启动的时候，需要用到属性值的时候，就是将原本spring中的propertySource的getProperty()方法委托给其自定义的实现EncryptablePropertySourceWrapper，调用其getProperty()方法，在这个方法的自定义实现中。判断是否是已经加密的value，如果是，则进行解密。如果不是，那就返回原值。

调用EncryptablePropertySourceWrapper的getProperty方法，其extends PropertySource，override了getProperty方法

public class EncryptablePropertySourceWrapper<T> extends PropertySource<T> implements EncryptablePropertySource<T> {
    private final PropertySource<T> delegate;
    private final StringEncryptor encryptor;

    public EncryptablePropertySourceWrapper(PropertySource<T> delegate, StringEncryptor encryptor) {
        super(delegate.getName(), delegate.getSource());
        Assert.notNull(delegate, "PropertySource delegate cannot be null");
        Assert.notNull(encryptor, "StringEncryptor cannot be null");
        this.delegate = delegate;
        this.encryptor = encryptor;
    }

    @Override
    public Object getProperty(String name) {
        return getProperty(encryptor, delegate, name);
    }
}

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其getProperty就去调用其implements的EncryptablePropertySource的getProperty方法，于是执行下面

public interface EncryptablePropertySource<T> {
    public default Object getProperty(StringEncryptor encryptor, PropertySource<T> source, String name) {
        Object value = source.getProperty(name);
        if(value instanceof String) {
            String stringValue = String.valueOf(value);
            if(PropertyValueEncryptionUtils.isEncryptedValue(stringValue)) {
                value = PropertyValueEncryptionUtils.decrypt(stringValue, encryptor);
            }
        }
        return value;
    }
}

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isEncryptedValue方法

private static final String ENCRYPTED_VALUE_PREFIX = "ENC(";
private static final String ENCRYPTED_VALUE_SUFFIX = ")";

public static boolean isEncryptedValue(final String value) {
    if (value == null) {
        return false;
    }
    final String trimmedValue = value.trim();
    return (trimmedValue.startsWith(ENCRYPTED_VALUE_PREFIX) && 
            trimmedValue.endsWith(ENCRYPTED_VALUE_SUFFIX));
}

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如果通过 prefixes/suffixes 包裹的属性，那么返回解密后的值；

如果没有被包裹，那么返回原生的值；

如果是加密的值，那么就去解密

StandardPBEByteEncryptor

public byte[] decrypt(final byte[] encryptedMessage) 
throws EncryptionOperationNotPossibleException {
if (encryptedMessage == null) {
return null;
}
// Check initialization
if (!isInitialized()) {
initialize();
}
if (this.saltGenerator.includePlainSaltInEncryptionResults()) {
// Check that the received message is bigger than the salt
if (encryptedMessage.length <= this.saltSizeBytes) {
throw new EncryptionOperationNotPossibleException();
}
}
try {
// If we are using a salt generator which specifies the salt
// to be included into the encrypted message itself, get it from 
// there. If not, the salt is supposed to be fixed and thus the
// salt generator can be safely asked for it again.
byte[] salt = null; 
byte[] encryptedMessageKernel = null; 
if (this.saltGenerator.includePlainSaltInEncryptionResults()) {
final int saltStart = 0;
final int saltSize = 
(this.saltSizeBytes < encryptedMessage.length? this.saltSizeBytes : encryptedMessage.length);
final int encMesKernelStart =
(this.saltSizeBytes < encryptedMessage.length? this.saltSizeBytes : encryptedMessage.length);
final int encMesKernelSize = 
(this.saltSizeBytes < encryptedMessage.length? (encryptedMessage.length - this.saltSizeBytes) : 0);
salt = new byte[saltSize];
encryptedMessageKernel = new byte[encMesKernelSize];
System.arraycopy(encryptedMessage, saltStart, salt, 0, saltSize);
System.arraycopy(encryptedMessage, encMesKernelStart, encryptedMessageKernel, 0, encMesKernelSize);
} else if (!this.usingFixedSalt){
salt = this.saltGenerator.generateSalt(this.saltSizeBytes);
encryptedMessageKernel = encryptedMessage;
} else {
// this.usingFixedSalt == true
salt = this.fixedSaltInUse;
encryptedMessageKernel = encryptedMessage;
}
final byte[] decryptedMessage;
if (this.usingFixedSalt) {
/*
* Fixed salt is being used, therefore no initialization supposedly needed
*/
synchronized (this.decryptCipher) {
decryptedMessage = 
this.decryptCipher.doFinal(encryptedMessageKernel);
}
} else {
/*
* Perform decryption using the Cipher
*/
final PBEParameterSpec parameterSpec = 
new PBEParameterSpec(salt, this.keyObtentionIterations);
synchronized (this.decryptCipher) {
this.decryptCipher.init(
Cipher.DECRYPT_MODE, this.key, parameterSpec);
decryptedMessage = 
this.decryptCipher.doFinal(encryptedMessageKernel);
}
}
// Return the results
return decryptedMessage;
} catch (final InvalidKeyException e) {
// The problem could be not having the unlimited strength policies
// installed, so better give a usefull error message.
handleInvalidKeyException(e);
throw new EncryptionOperationNotPossibleException();
} catch (final Exception e) {
// If decryption fails, it is more secure not to return any 
// information about the cause in nested exceptions. Simply fail.
throw new EncryptionOperationNotPossibleException();
}
}

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以spring.datasource.username为例：

明文是root

密文是ENC(X4OZ4csEAWqPCEvWf+aRPA==)

可以看到其salt是encryptedMessage的

System.arraycopy(encryptedMessage, saltStart, salt, 0, saltSize);
System.arraycopy(encryptedMessage, encMesKernelStart, encryptedMessageKernel, 0, encMesKernelSize);

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0-7byte解析为salt，8-15byte解析为密文

然后就通过基本的PBE解析方式，来解析出来

ASCII码对应的结果就是root

所以我们就可以知道，如果我获得了jasypt的password，那么由于其salt是放在encryptedMessage中的，那么我是没什么压力就可以解密的。

所以应该java -jar –Djasypt.encryptor.password=xxx abc.jar方式来启动服务。这样只要在运维端不泄露password，那么只拿到配置文件的密文，还是安全的。

补充1：查看JDK提供的Cipher算法

jasypt默认使用的是PBEWITHMD5ANDDES，其实JDK中由SunJCE所提供的。

可以通过下面的代码来查看JDK中提供了哪些Cipher算法

@Test
public void listJdkAlgorithm() {
/*        Provider[] providers = Security.getProviders();
for (Provider provider :
providers) {
LOGGER.info("security provider: {} , version: {}", provider.getName(), provider.getVersion());
LOGGER.info("security provider info: {}", provider.getInfo());
}*/
Set<String> messageDigest = Security.getAlgorithms("Cipher");
for (String s :
messageDigest) {
LOGGER.info("MessageDigest: {}",s);
}
}

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更全面的安全方面的算法，如摘要算法、签名算法等

补充2：PBE的基础算法demo，

而且可以看出来，jasypt中使用了几乎相同的代码来进行加解密的

public class PBECipher {
static final String CIPHER_NAME = "PBEwithMD5AndDES";
public static byte[] encrypt(String password, byte[] salt, byte[] input) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance(CIPHER_NAME);
// 这个secretKey 就是我们将来要使用的加密的密钥
SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
// 传入1000，表示用户输入的口令，会与这个salt进行1000次的循环
PBEParameterSpec pbeParameterSpec = new PBEParameterSpec(salt, 1000);
Cipher cipher = Cipher.getInstance(CIPHER_NAME);
cipher.init(Cipher.ENCRYPT_MODE, secretKey, pbeParameterSpec);
return cipher.doFinal(input);
}
public static byte[] decrypt(String password, byte[] salt, byte[] input) throws NoSuchAlgorithmException,
InvalidKeySpecException, NoSuchPaddingException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance(CIPHER_NAME);
SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
PBEParameterSpec pbeParameterSpec = new PBEParameterSpec(salt, 1000);
Cipher cipher = Cipher.getInstance(CIPHER_NAME);
cipher.init(Cipher.DECRYPT_MODE, secretKey, pbeParameterSpec);
return cipher.doFinal(input);
}
}

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测试

@Test
public void testPBE() throws NoSuchAlgorithmException, UnsupportedEncodingException, NoSuchPaddingException,
InvalidKeyException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException, InvalidKeySpecException {
String message = "constfafa";
String password = "ydbs";
byte[] salt = SecureRandom.getInstanceStrong().generateSeed(8);
System.out.printf("salt: %032x\n", new BigInteger(1, salt));
//加密和解密的salt是一样的
byte[] data = message.getBytes("UTF-8");
byte[] encrypt = PBECipher.encrypt(password, salt, data);
LOGGER.info("encrypted data: {}", Base64.getEncoder().encodeToString(encrypt));
byte[] decrypt = PBECipher.decrypt(password, salt, encrypt);
LOGGER.info("decrypted data: {}", new String(decrypt,"UTF-8"));