【发布时间】：2021-02-04 02:22:44
【问题描述】：
我参考了this 并尝试使用 base64 解码进行文件解密
我的要求是加密时用base64编码数据，解密时用base64解码数据。
但我面临以下错误：
javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
at java.base/com.sun.crypto.provider.CipherCore.doFinal(Unknown Source)
at java.base/com.sun.crypto.provider.CipherCore.doFinal(Unknown Source)
at java.base/com.sun.crypto.provider.AESCipher.engineDoFinal(Unknown Source)
at java.base/javax.crypto.Cipher.doFinal(Unknown Source)
at aes.DecryptNew.decryptNew(DecryptNew.java:124)
at aes.DecryptNew.main(DecryptNew.java:32)
我也对如何分块执行解密感到困惑。 请在此代码中向我提出问题。
import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.*;
import java.util.Arrays;
import java.util.Base64;
public class DecryptNew {
public static void main(String[] args) {
String plaintextFilename = "D:\\\\plaintext.txt";
String ciphertextFilename = "D:\\\\plaintext.txt.crypt";
String decryptedtextFilename = "D:\\\\plaintextDecrypted.txt";
String password = "testpass";
writeToFile();
String ciphertext = encryptfile(plaintextFilename, password);
System.out.println("ciphertext: " + ciphertext);
decryptNew(ciphertextFilename, password, decryptedtextFilename);
}
static void writeToFile() {
BufferedWriter writer = null;
try
{
writer = new BufferedWriter( new FileWriter("D:\\\\plaintext.txt"));
byte[] data = Base64.getEncoder().encode("hello\r\nhello".getBytes(StandardCharsets.UTF_8));
writer.write(new String(data));
}
catch ( IOException e)
{
}
finally
{
try
{
if ( writer != null)
writer.close( );
}
catch ( IOException e)
{
}
}
}
public static String encryptfile(String path, String password) {
try {
FileInputStream fis = new FileInputStream(path);
FileOutputStream fos = new FileOutputStream(path.concat(".crypt"));
final byte[] pass = Base64.getEncoder().encode(password.getBytes());
final byte[] salt = (new SecureRandom()).generateSeed(8);
fos.write(Base64.getEncoder().encode("Salted__".getBytes()));
fos.write(salt);
final byte[] passAndSalt = concatenateByteArrays(pass, salt);
byte[] hash = new byte[0];
byte[] keyAndIv = new byte[0];
for (int i = 0; i < 3 && keyAndIv.length < 48; i++) {
final byte[] hashData = concatenateByteArrays(hash, passAndSalt);
final MessageDigest md = MessageDigest.getInstance("SHA-1");
hash = md.digest(hashData);
keyAndIv = concatenateByteArrays(keyAndIv, hash);
}
final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, 32);
final byte[] iv = Arrays.copyOfRange(keyAndIv, 32, 48);
final SecretKeySpec key = new SecretKeySpec(keyValue, "AES");
final Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
CipherOutputStream cos = new CipherOutputStream(fos, cipher);
int b;
byte[] d = new byte[8];
while ((b = fis.read(d)) != -1) {
cos.write(d, 0, b);
}
cos.flush();
cos.close();
fis.close();
System.out.println("encrypt done " + path);
} catch (IOException | NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | InvalidAlgorithmParameterException e) {
e.printStackTrace();
}
return path;
}
static void decryptNew(String path,String password, String outPath) {
byte[] SALTED_MAGIC = Base64.getEncoder().encode("Salted__".getBytes());
try{
FileInputStream fis = new FileInputStream(path);
FileOutputStream fos = new FileOutputStream(outPath);
final byte[] pass = password.getBytes(StandardCharsets.US_ASCII);
final byte[] inBytes = Files.readAllBytes(Paths.get(path));
final byte[] shouldBeMagic = Arrays.copyOfRange(inBytes, 0, SALTED_MAGIC.length);
if (!Arrays.equals(shouldBeMagic, SALTED_MAGIC)) {
throw new IllegalArgumentException("Initial bytes from input do not match OpenSSL SALTED_MAGIC salt value.");
}
final byte[] salt = Arrays.copyOfRange(inBytes, SALTED_MAGIC.length, SALTED_MAGIC.length + 8);
final byte[] passAndSalt = concatenateByteArrays(pass, salt);
byte[] hash = new byte[0];
byte[] keyAndIv = new byte[0];
for (int i = 0; i < 3 && keyAndIv.length < 48; i++) {
final byte[] hashData = concatenateByteArrays(hash, passAndSalt);
MessageDigest md = null;
md = MessageDigest.getInstance("SHA-1");
hash = md.digest(hashData);
keyAndIv = concatenateByteArrays(keyAndIv, hash);
}
final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, 32);
final SecretKeySpec key = new SecretKeySpec(keyValue, "AES");
final byte[] iv = Arrays.copyOfRange(keyAndIv, 32, 48);
final Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
final byte[] clear = cipher.doFinal(inBytes, 16, inBytes.length - 16);
String contentDecoded = new String(Base64.getDecoder().decode(clear));
fos.write(contentDecoded.getBytes());
fos.close();
System.out.println("Decrypt is completed");
}catch(Exception e){
e.printStackTrace();
}
}
public static byte[] concatenateByteArrays(byte[] a, byte[] b) {
return ByteBuffer
.allocate(a.length + b.length)
.put(a).put(b)
.array();
}
}
【问题讨论】：
-
对于密码，不同的编码用于加密和解密（Base64 vs ASCII）。两者必须相同。加密和解密都使用了Base64编码前缀
Salted__，所以前缀加盐大于一个块（16字节），这与解密时密文的长度确定不一致。一个解决方案是例如一个 ASCII 编码的前缀。 -
我不清楚您真正想要实现什么。加密仅对前缀执行 Base64 编码。 Base64 编码的明文并不意味着加密本身执行 Base64 编码，而是仅对 Base64 编码的明文进行加密。不应该像 OpenSSL 使用 -base64 选项一样对所有内容进行 Base64 编码（即前缀、盐和密文）吗？
-
我这边的两件事 - 使用块加密最好使用 CipherInput-/Outputstream 完成。仅当您使用大文件（超过几兆字节）以避免遇到“内存不足错误”时，才需要这样做。其次，您应该考虑使用 Apache 公共编解码器库中的 Base64Input-/Outputstream（将其放在 FileInput/FileOutputStream 之间）。
标签： java encryption openssl base64 sha1