poi/src/ooxml/testcases/org/apache/poi/poifs/crypt/TestSecureTempZip.java

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   this work for additional information regarding copyright ownership.
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package org.apache.poi.poifs.crypt;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.SecureRandom;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipException;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.spec.SecretKeySpec;

import org.apache.poi.openxml4j.exceptions.OpenXML4JException;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.openxml4j.util.ZipEntrySource;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.util.IOUtils;
import org.apache.poi.util.TempFile;
import org.apache.poi.xssf.XSSFTestDataSamples;
import org.apache.poi.xssf.extractor.XSSFEventBasedExcelExtractor;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.xmlbeans.XmlException;
import org.junit.Test;

public class TestSecureTempZip {
    /**
     * Test case for #59841 - this is an example on how to use encrypted temp files,
     * which are streamed into POI opposed to having everything in memory
     */
    @Test
    public void protectedTempZip() throws IOException, GeneralSecurityException, XmlException, OpenXML4JException {
        final File tmpFile = TempFile.createTempFile("protectedXlsx", ".zip");
        File tikaProt = XSSFTestDataSamples.getSampleFile("protected_passtika.xlsx");
        FileInputStream fis = new FileInputStream(tikaProt);
        POIFSFileSystem poifs = new POIFSFileSystem(fis);
        EncryptionInfo ei = new EncryptionInfo(poifs);
        Decryptor dec = ei.getDecryptor();
        boolean passOk = dec.verifyPassword("tika");
        assertTrue(passOk);

        // generate session key
        SecureRandom sr = new SecureRandom();
        byte[] ivBytes = new byte[16], keyBytes = new byte[16];
        sr.nextBytes(ivBytes);
        sr.nextBytes(keyBytes);
        
        // extract encrypted ooxml file and write to custom encrypted zip file 
        InputStream is = dec.getDataStream(poifs);
        copyToFile(is, tmpFile, CipherAlgorithm.aes128, keyBytes, ivBytes);
        is.close();
        
        // provide ZipEntrySource to poi which decrypts on the fly
        ZipEntrySource source = fileToSource(tmpFile, CipherAlgorithm.aes128, keyBytes, ivBytes);

        // test the source
        OPCPackage opc = OPCPackage.open(source);
        String expected = "This is an Encrypted Excel spreadsheet.";
        
        XSSFEventBasedExcelExtractor extractor = new XSSFEventBasedExcelExtractor(opc);
        extractor.setIncludeSheetNames(false);
        String txt = extractor.getText();
        assertEquals(expected, txt.trim());
        
        XSSFWorkbook wb = new XSSFWorkbook(opc);
        txt = wb.getSheetAt(0).getRow(0).getCell(0).getStringCellValue();
        assertEquals(expected, txt);

        extractor.close();
        
        wb.close();
        opc.close();
        source.close();
        poifs.close();
        fis.close();
        tmpFile.delete();
    }
    
    private void copyToFile(InputStream is, File tmpFile, CipherAlgorithm cipherAlgorithm, byte keyBytes[], byte ivBytes[]) throws IOException, GeneralSecurityException {
        SecretKeySpec skeySpec = new SecretKeySpec(keyBytes, cipherAlgorithm.jceId);
        Cipher ciEnc = CryptoFunctions.getCipher(skeySpec, cipherAlgorithm, ChainingMode.cbc, ivBytes, Cipher.ENCRYPT_MODE, "PKCS5Padding");

        ZipInputStream zis = new ZipInputStream(is);
        FileOutputStream fos = new FileOutputStream(tmpFile);
        ZipOutputStream zos = new ZipOutputStream(fos);

        ZipEntry ze;
        while ((ze = zis.getNextEntry()) != null) {
            // the cipher output stream pads the data, therefore we can't reuse the ZipEntry with set sizes
            // as those will be validated upon close()
            ZipEntry zeNew = new ZipEntry(ze.getName());
            zeNew.setComment(ze.getComment());
            zeNew.setExtra(ze.getExtra());
            zeNew.setTime(ze.getTime());
            // zeNew.setMethod(ze.getMethod());
            zos.putNextEntry(zeNew);
            FilterOutputStream fos2 = new FilterOutputStream(zos){
                // don't close underlying ZipOutputStream
                public void close() {}
            };
            CipherOutputStream cos = new CipherOutputStream(fos2, ciEnc);
            IOUtils.copy(zis, cos);
            cos.close();
            fos2.close();
            zos.closeEntry();
            zis.closeEntry();
        }
        zos.close();
        fos.close();
        zis.close();
    }
    
    private ZipEntrySource fileToSource(File tmpFile, CipherAlgorithm cipherAlgorithm, byte keyBytes[], byte ivBytes[]) throws ZipException, IOException {
        SecretKeySpec skeySpec = new SecretKeySpec(keyBytes, cipherAlgorithm.jceId);
        Cipher ciDec = CryptoFunctions.getCipher(skeySpec, cipherAlgorithm, ChainingMode.cbc, ivBytes, Cipher.DECRYPT_MODE, "PKCS5Padding");
        ZipFile zf = new ZipFile(tmpFile);
        return new AesZipFileZipEntrySource(zf, ciDec);
    }

    static class AesZipFileZipEntrySource implements ZipEntrySource {
        final ZipFile zipFile;
        final Cipher ci;
        boolean closed;

        AesZipFileZipEntrySource(ZipFile zipFile, Cipher ci) {
            this.zipFile = zipFile;
            this.ci = ci;
            this.closed = false;
        }

        /**
         * Note: the file sizes are rounded up to the next cipher block size,
         * so don't rely on file sizes of these custom encrypted zip file entries!
         */
        public Enumeration<? extends ZipEntry> getEntries() {
            return zipFile.entries();
        }

        @SuppressWarnings("resource")
        public InputStream getInputStream(ZipEntry entry) throws IOException {
            InputStream is = zipFile.getInputStream(entry);
            return new CipherInputStream(is, ci);
        }

        @Override
        public void close() throws IOException {
            zipFile.close();
            closed = true;
        }
        
        @Override
        public boolean isClosed() {
            return closed;
        }
    }
}