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本文主要研究一下Jasypt的StandardPBEByteEncryptor

Jasypt

Jasypt即Java Simplified Encryption，它主要是简化项目加解密的工作，内置提供了很多组件的集成，比如hibernate、spring、spring-security等

示例

示例1

StrongPasswordEncryptor passwordEncryptor = new StrongPasswordEncryptor();
String encryptedPassword = passwordEncryptor.encryptPassword(userPassword);
...
if (passwordEncryptor.checkPassword(inputPassword, encryptedPassword)) {
  // correct!
} else {
  // bad login!
}

示例2

AES256TextEncryptor textEncryptor = new AES256TextEncryptor();
textEncryptor.setPassword(myEncryptionPassword);
String myEncryptedText = textEncryptor.encrypt(myText);
...
String plainText = textEncryptor.decrypt(myEncryptedText);

StandardPBEByteEncryptor

org/jasypt/encryption/pbe/StandardPBEByteEncryptor.java

public final class StandardPBEByteEncryptor implements PBEByteCleanablePasswordEncryptor {

    /**
     * The default algorithm to be used if none specified: PBEWithMD5AndDES.
     */
    public static final String DEFAULT_ALGORITHM = "PBEWithMD5AndDES";

    /**
     * The default number of hashing iterations applied for obtaining the encryption key from the specified password,
     * set to 1000.
     */
    public static final int DEFAULT_KEY_OBTENTION_ITERATIONS = 1000;

    /**
     * The default salt size, only used if the chosen encryption algorithm is not a block algorithm and thus block size
     * cannot be used as salt size.
     */
    public static final int DEFAULT_SALT_SIZE_BYTES = 8;

    /**
     * The default IV size
     */
    public static final int IV_SIZE_IN_BITS = 128;

    // Algorithm (and provider-related info) for Password Based Encoding.
    private String algorithm = DEFAULT_ALGORITHM;
    private String providerName = null;
    private Provider provider = null;

    // Password to be applied. This will NOT have a default value. If none
    // is set during configuration, an exception will be thrown.
    private char[] password = null;

    // Number of hashing iterations to be applied for obtaining the encryption
    // key from the specified password.
    private int keyObtentionIterations = DEFAULT_KEY_OBTENTION_ITERATIONS;

    // SaltGenerator to be used. Initialization of a salt generator is costly,
    // and so default value will be applied only in initialize(), if it finally
    // becomes necessary.
    private SaltGenerator saltGenerator = null;

    // IVGenerator to initialise IV
    private IVGenerator ivGenerator = null;

    // Size in bytes of the IV to be used
    private final int IVSizeBytes = IV_SIZE_IN_BITS;

    // Size in bytes of the salt to be used for obtaining the
    // encryption key. This size will depend on the PBE algorithm being used,
    // and it will be set to the size of the block for the specific
    // chosen algorithm (if the algorithm is not a block algorithm, the
    // default value will be used).
    private int saltSizeBytes = DEFAULT_SALT_SIZE_BYTES;

    //......
}    

StandardPBEByteEncryptor实现了PBEByteCleanablePasswordEncryptor接口，而该则集成了PBEByteEncryptor和CleanablePasswordBased接口，PBEByteEncryptor继承了ByteEncryptor、PasswordBased

ByteEncryptor

org/jasypt/encryption/ByteEncryptor.java

public interface ByteEncryptor {
    
    
    /**
     * Encrypt the input message
     * 
     * @param message the message to be encrypted
     * @return the result of encryption
     */
    public byte[] encrypt(byte[] message);

    /**
     * Decrypt an encrypted message
     * 
     * @param encryptedMessage the encrypted message to be decrypted
     * @return the result of decryption
     */
    public byte[] decrypt(byte[] encryptedMessage);
    
}

ByteEncryptor定义了encrypt和decrypt方法

StandardPBEByteEncryptor.encrypt

    public byte[] encrypt(final byte[] message) throws EncryptionOperationNotPossibleException {

        if (message == null) {
            return null;
        }

        // Check initialization
        if (!isInitialized()) {
            initialize();
        }

        try {

            final byte[] salt;
            byte[] iv = null;
            final byte[] encryptedMessage;
            if (usingFixedSalt) {

                salt = fixedSaltInUse;

                synchronized (encryptCipher) {
                    encryptedMessage = encryptCipher.doFinal(message);
                }

            }
            else {

                // Create salt
                salt = saltGenerator.generateSalt(saltSizeBytes);

                // Create the IV
                iv = ivGenerator.generateIV(IVSizeBytes);

                IvParameterSpec ivParameterSpec = null;
                if (iv != null) {
                    ivParameterSpec = new IvParameterSpec(iv);
                }

                /*
                 * Perform encryption using the Cipher
                 */
                final PBEParameterSpec parameterSpec = new PBEParameterSpec(salt, keyObtentionIterations,
                            ivParameterSpec);

                synchronized (encryptCipher) {
                    encryptCipher.init(Cipher.ENCRYPT_MODE, key, parameterSpec);
                    encryptedMessage = encryptCipher.doFinal(message);

                }

            }

            byte[] encryptedMessageWithIV = encryptedMessage;

            if (ivGenerator.includePlainIVInEncryptionResults()) {
                encryptedMessageWithIV = CommonUtils.appendArrays(iv, encryptedMessage);
            }

            // Finally we build an array containing both the unencrypted salt
            // and the result of the encryption. This is done only
            // if the salt generator we are using specifies to do so.
            if (saltGenerator.includePlainSaltInEncryptionResults()) {

                // Insert unhashed salt before the encryption result
                final byte[] encryptedMessageWithIVAndSalt = CommonUtils.appendArrays(salt, encryptedMessageWithIV);
                return encryptedMessageWithIVAndSalt;

            }

            return encryptedMessageWithIV;

        }
        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 encryption fails, it is more secure not to return any
            // information about the cause in nested exceptions. Simply fail.
            throw new EncryptionOperationNotPossibleException();
        }

    }

StandardPBEByteEncryptor的encrypt方法，该方法首先判断salt值是固定的和动态的，固定的则是初始化的时候就设置好的，直接从实例属性取，然后直接调用cipher加密
而动态的话，则通过saltGenerator和generateIV来生成salt和iv，之后根据salt、iv和keyObtentionIterations来创建PBEParameterSpec，然后初始化cipher再进行加密
最后通过ivGenerator判断是否需要把iv包含到加密结果中，是则append到前面进去，再通过saltGenerator判断是否应该把slat包含到加密结果中，是则append到前面进去，最后返回解密结果

StandardPBEByteEncryptor.decrypt

    public byte[] decrypt(final byte[] encryptedMessage) throws EncryptionOperationNotPossibleException {

        if (encryptedMessage == null) {
            return null;
        }

        // Check initialization
        if (!isInitialized()) {
            initialize();
        }

        if (saltGenerator.includePlainSaltInEncryptionResults()) {
            // Check that the received message is bigger than the salt
            if (encryptedMessage.length <= saltSizeBytes) {
                throw new EncryptionOperationNotPossibleException();
            }
        }

        // if (this.ivGenerator.includePlainIVInEncryptionResults()) {
        // // Check that the received message is bigger than the IV
        // if (encryptedMessage.length <= this.IVSizeBytes) {
        // 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 (saltGenerator.includePlainSaltInEncryptionResults()) {

                final int saltStart = 0;
                final int saltSize = saltSizeBytes < encryptedMessage.length ? saltSizeBytes : encryptedMessage.length;
                final int encMesKernelStart = saltSizeBytes < encryptedMessage.length ? saltSizeBytes
                            : encryptedMessage.length;
                final int encMesKernelSize = saltSizeBytes < encryptedMessage.length
                            ? encryptedMessage.length - 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 (!usingFixedSalt) {

                salt = saltGenerator.generateSalt(saltSizeBytes);
                encryptedMessageKernel = encryptedMessage;

            }
            else {
                // this.usingFixedSalt == true

                salt = fixedSaltInUse;
                encryptedMessageKernel = encryptedMessage;
            }

            // Logic for IV
            byte[] finalEncryptedMessage;
            byte[] iv;

            if (ivGenerator.includePlainIVInEncryptionResults()) {

                // Extracting the IV
                iv = Arrays.copyOfRange(encryptedMessageKernel, 0, IVSizeBytes / 8);
                finalEncryptedMessage = Arrays.copyOfRange(encryptedMessageKernel, iv.length,
                            encryptedMessageKernel.length);

            }
            else {
                // Fixed IV
                finalEncryptedMessage = encryptedMessageKernel;
                iv = ivGenerator.generateIV(IVSizeBytes);
            }

            final byte[] decryptedMessage;
            if (usingFixedSalt) {

                /*
                 * Fixed salt is being used, therefore no initialization supposedly needed
                 */

                synchronized (decryptCipher) {
                    decryptedMessage = decryptCipher.doFinal(encryptedMessageKernel);
                }

            }
            else {

                /*
                 * Perform decryption using the Cipher
                 */
                IvParameterSpec ivParameterSpec = null;
                if (iv != null) {
                    ivParameterSpec = new IvParameterSpec(iv);
                }

                final PBEParameterSpec parameterSpec = new PBEParameterSpec(salt, keyObtentionIterations,
                            ivParameterSpec);

                synchronized (decryptCipher) {
                    decryptCipher.init(Cipher.DECRYPT_MODE, key, parameterSpec);
                    decryptedMessage = decryptCipher.doFinal(finalEncryptedMessage);

                }

            }

            // 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();
        }

    }

StandardPBEByteEncryptor的decrypt方法先通过saltGenerator判断salt是否包含在密文中，是则根据配置的salt的长度从密文取出来salt，之后通过ivGenerator判断iv是否包含在密文中，是则从剩下的密文取出来iv，得到slat和iv之后，对剩下的密文进行解密

小结

StandardPBEByteEncryptor实现了ByteEncryptor的encrypt和decrypt方法，其主要思路就是判断slat、iv是否包含在密文，然后做对应的处理。

doc

• Jasypt