com.github.isaichkindanila.crypt.lib.stream.DecryptedInputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of crypt-lib Show documentation
Simple Java library for stream ciphers based encryption
The newest version!
package com.github.isaichkindanila.crypt.lib.stream;

import com.github.isaichkindanila.crypt.lib.cipher.StreamCipher;

import java.io.IOException;
import java.io.InputStream;

/**
 * {@code InputStream} wrapper used to decrypt data as it's being read.
 *
 * @see EncryptedOutputStream
 */
public class DecryptedInputStream extends InputStream {
    private final InputStream in;
    private final StreamCipher cipher;

    /**
     * Creates new instance of {@code DecryptedInputStream}.
     * 
     * {@code DecryptedInputStream} automatically detects which cipher was used to encrypt it.
     *
     * @param in       wrapped {@code InputStream}
     * @param password password to be used as cipher key
     * @throws IOException                    if {@code IOException} occurs while stream header is being read
     * @throws MalformedStreamHeaderException if stream header is malformed
     * @throws UnsupportedCipherException     if the stream was encrypted with cipher which is not supported by this version of Crypt Lib
     * @throws IncorrectPasswordException     if the stream was encrypted with different password
     */
    public DecryptedInputStream(InputStream in, String password) throws IOException {
        CryptStream stream = new CryptStream(in, null);
        stream.checkStreamSignature();

        byte[] key = stream.hash(password);
        byte[] iv = stream.readIV();

        this.cipher = stream.readCipher().newInstance(key, iv);
        this.in = in;

        byte[] passHash = stream.hash(key, iv);
        byte[] streamPassHash = new byte[passHash.length];

        if (this.read(streamPassHash) != streamPassHash.length) {
            throw new IncorrectPasswordException();
        }

        for (int i = 0; i < passHash.length; i++) {
            if (streamPassHash[i] != passHash[i]) {
                throw new IncorrectPasswordException();
            }
        }
    }

    /**
     * Reads and decrypts a byte from wrapped stream.
     *
     * @return decrypted byte from wrapped stream
     * @throws IOException if IOException occurs
     */
    @Override
    public int read() throws IOException {
        int c = in.read();
        return c == -1 ? -1 : cipher.apply((byte) c) & 0xff;
    }

    @Override
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int result = in.read(b, off, len);
        cipher.apply(b, off, result);

        return result;
    }

    @Override
    public void close() throws IOException {
        in.close();
    }
}