com.itextpdf.kernel.crypto.securityhandler.StandardHandlerUsingAes256 Maven / Gradle / Ivy
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Authors: Bruno Lowagie, Paulo Soares, et al.
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package com.itextpdf.kernel.crypto.securityhandler;
import com.itextpdf.io.util.StreamUtil;
import com.itextpdf.kernel.PdfException;
import com.itextpdf.kernel.crypto.AESCipherCBCnoPad;
import com.itextpdf.kernel.crypto.AesDecryptor;
import com.itextpdf.kernel.crypto.BadPasswordException;
import com.itextpdf.kernel.crypto.IDecryptor;
import com.itextpdf.kernel.crypto.IVGenerator;
import com.itextpdf.kernel.crypto.OutputStreamAesEncryption;
import com.itextpdf.kernel.crypto.OutputStreamEncryption;
import com.itextpdf.kernel.pdf.PdfBoolean;
import com.itextpdf.kernel.pdf.PdfDictionary;
import com.itextpdf.kernel.pdf.PdfLiteral;
import com.itextpdf.kernel.pdf.PdfName;
import com.itextpdf.kernel.pdf.PdfNumber;
import java.io.OutputStream;
import java.security.MessageDigest;
public class StandardHandlerUsingAes256 extends StandardSecurityHandler {
private static final int VALIDATION_SALT_OFFSET = 32;
private static final int KEY_SALT_OFFSET = 40;
private static final int SALT_LENGTH = 8;
private static final int OU_LENGTH = 48;
private static final long serialVersionUID = -8365943606887257386L;
protected boolean encryptMetadata;
public StandardHandlerUsingAes256(PdfDictionary encryptionDictionary, byte[] userPassword, byte[] ownerPassword,
int permissions, boolean encryptMetadata, boolean embeddedFilesOnly) {
initKeyAndFillDictionary(encryptionDictionary, userPassword, ownerPassword, permissions, encryptMetadata, embeddedFilesOnly);
}
public StandardHandlerUsingAes256(PdfDictionary encryptionDictionary, byte[] password) {
initKeyAndReadDictionary(encryptionDictionary, password);
}
public boolean isEncryptMetadata() {
return encryptMetadata;
}
@Override
public void setHashKeyForNextObject(int objNumber, int objGeneration) {
// in AES256 we don't recalculate nextObjectKey
}
@Override
public OutputStreamEncryption getEncryptionStream(OutputStream os) {
return new OutputStreamAesEncryption(os, nextObjectKey, 0, nextObjectKeySize);
}
@Override
public IDecryptor getDecryptor() {
return new AesDecryptor(nextObjectKey, 0, nextObjectKeySize);
}
private void initKeyAndFillDictionary(PdfDictionary encryptionDictionary, byte[] userPassword, byte[] ownerPassword,
int permissions, boolean encryptMetadata, boolean embeddedFilesOnly) {
ownerPassword = generateOwnerPasswordIfNullOrEmpty(ownerPassword);
permissions |= PERMS_MASK_1_FOR_REVISION_3_OR_GREATER;
permissions &= PERMS_MASK_2;
try {
byte[] userKey;
byte[] ownerKey;
byte[] ueKey;
byte[] oeKey;
byte[] aes256Perms;
if (userPassword == null) {
userPassword = new byte[0];
}
byte[] uvs = IVGenerator.getIV(8);
byte[] uks = IVGenerator.getIV(8);
nextObjectKey = IVGenerator.getIV(32);
nextObjectKeySize = 32;
// Algorithm 3.8.1
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(userPassword, 0, Math.min(userPassword.length, 127));
md.update(uvs);
userKey = new byte[48];
md.digest(userKey, 0, 32);
System.arraycopy(uvs, 0, userKey, 32, 8);
System.arraycopy(uks, 0, userKey, 40, 8);
// Algorithm 3.8.2
md.update(userPassword, 0, Math.min(userPassword.length, 127));
md.update(uks);
AESCipherCBCnoPad ac = new AESCipherCBCnoPad(true, md.digest());
ueKey = ac.processBlock(nextObjectKey, 0, nextObjectKey.length);
// Algorithm 3.9.1
byte[] ovs = IVGenerator.getIV(8);
byte[] oks = IVGenerator.getIV(8);
md.update(ownerPassword, 0, Math.min(ownerPassword.length, 127));
md.update(ovs);
md.update(userKey);
ownerKey = new byte[48];
md.digest(ownerKey, 0, 32);
System.arraycopy(ovs, 0, ownerKey, 32, 8);
System.arraycopy(oks, 0, ownerKey, 40, 8);
// Algorithm 3.9.2
md.update(ownerPassword, 0, Math.min(ownerPassword.length, 127));
md.update(oks);
md.update(userKey);
ac = new AESCipherCBCnoPad(true, md.digest());
oeKey = ac.processBlock(nextObjectKey, 0, nextObjectKey.length);
// Algorithm 3.10
byte[] permsp = IVGenerator.getIV(16);
permsp[0] = (byte) permissions;
permsp[1] = (byte) (permissions >> 8);
permsp[2] = (byte) (permissions >> 16);
permsp[3] = (byte) (permissions >> 24);
permsp[4] = (byte) (255);
permsp[5] = (byte) (255);
permsp[6] = (byte) (255);
permsp[7] = (byte) (255);
permsp[8] = encryptMetadata ? (byte) 'T' : (byte) 'F';
permsp[9] = (byte) 'a';
permsp[10] = (byte) 'd';
permsp[11] = (byte) 'b';
ac = new AESCipherCBCnoPad(true, nextObjectKey);
aes256Perms = ac.processBlock(permsp, 0, permsp.length);
this.permissions = permissions;
this.encryptMetadata = encryptMetadata;
setStandardHandlerDicEntries(encryptionDictionary, userKey, ownerKey);
setAES256DicEntries(encryptionDictionary, oeKey, ueKey, aes256Perms, encryptMetadata, embeddedFilesOnly);
} catch (Exception ex) {
throw new PdfException(PdfException.PdfEncryption, ex);
}
}
private void setAES256DicEntries(PdfDictionary encryptionDictionary, byte[] oeKey, byte[] ueKey, byte[] aes256Perms,
boolean encryptMetadata, boolean embeddedFilesOnly) {
int aes256Revision = 5;
encryptionDictionary.put(PdfName.OE, new PdfLiteral(StreamUtil.createEscapedString(oeKey)));
encryptionDictionary.put(PdfName.UE, new PdfLiteral(StreamUtil.createEscapedString(ueKey)));
encryptionDictionary.put(PdfName.Perms, new PdfLiteral(StreamUtil.createEscapedString(aes256Perms)));
encryptionDictionary.put(PdfName.R, new PdfNumber(aes256Revision));
encryptionDictionary.put(PdfName.V, new PdfNumber(aes256Revision));
PdfDictionary stdcf = new PdfDictionary();
stdcf.put(PdfName.Length, new PdfNumber(32));
if (!encryptMetadata) {
encryptionDictionary.put(PdfName.EncryptMetadata, PdfBoolean.FALSE);
}
if (embeddedFilesOnly) {
stdcf.put(PdfName.AuthEvent, PdfName.EFOpen);
encryptionDictionary.put(PdfName.EFF, PdfName.StdCF);
encryptionDictionary.put(PdfName.StrF, PdfName.Identity);
encryptionDictionary.put(PdfName.StmF, PdfName.Identity);
} else {
stdcf.put(PdfName.AuthEvent, PdfName.DocOpen);
encryptionDictionary.put(PdfName.StrF, PdfName.StdCF);
encryptionDictionary.put(PdfName.StmF, PdfName.StdCF);
}
stdcf.put(PdfName.CFM, PdfName.AESV3);
PdfDictionary cf = new PdfDictionary();
cf.put(PdfName.StdCF, stdcf);
encryptionDictionary.put(PdfName.CF, cf);
}
private void initKeyAndReadDictionary(PdfDictionary encryptionDictionary, byte[] password) {
try {
if (password == null)
password = new byte[0];
byte[] oValue = getIsoBytes(encryptionDictionary.getAsString(PdfName.O));
byte[] uValue = getIsoBytes(encryptionDictionary.getAsString(PdfName.U));
byte[] oeValue = getIsoBytes(encryptionDictionary.getAsString(PdfName.OE));
byte[] ueValue = getIsoBytes(encryptionDictionary.getAsString(PdfName.UE));
byte[] perms = getIsoBytes(encryptionDictionary.getAsString(PdfName.Perms));
PdfNumber pValue = (PdfNumber) encryptionDictionary.get(PdfName.P);
this.permissions = pValue.longValue();
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(password, 0, Math.min(password.length, 127));
md.update(oValue, VALIDATION_SALT_OFFSET, SALT_LENGTH);
md.update(uValue, 0, OU_LENGTH);
byte[] hash = md.digest();
usedOwnerPassword = compareArray(hash, oValue, 32);
if (usedOwnerPassword) {
md.update(password, 0, Math.min(password.length, 127));
md.update(oValue, KEY_SALT_OFFSET, SALT_LENGTH);
md.update(uValue, 0, OU_LENGTH);
hash = md.digest();
AESCipherCBCnoPad ac = new AESCipherCBCnoPad(false, hash);
nextObjectKey = ac.processBlock(oeValue, 0, oeValue.length);
} else {
md.update(password, 0, Math.min(password.length, 127));
md.update(uValue, VALIDATION_SALT_OFFSET, SALT_LENGTH);
hash = md.digest();
if (!compareArray(hash, uValue, 32))
throw new BadPasswordException(PdfException.BadUserPassword);
md.update(password, 0, Math.min(password.length, 127));
md.update(uValue, KEY_SALT_OFFSET, SALT_LENGTH);
hash = md.digest();
AESCipherCBCnoPad ac = new AESCipherCBCnoPad(false, hash);
nextObjectKey = ac.processBlock(ueValue, 0, ueValue.length);
}
nextObjectKeySize = 32;
AESCipherCBCnoPad ac = new AESCipherCBCnoPad(false, nextObjectKey);
byte[] decPerms = ac.processBlock(perms, 0, perms.length);
if (decPerms[9] != (byte) 'a' || decPerms[10] != (byte) 'd' || decPerms[11] != (byte) 'b')
throw new BadPasswordException(PdfException.BadUserPassword);
permissions = (decPerms[0] & 0xff) | ((decPerms[1] & 0xff) << 8)
| ((decPerms[2] & 0xff) << 16) | ((decPerms[2] & 0xff) << 24);
encryptMetadata = decPerms[8] == (byte) 'T';
} catch (BadPasswordException ex) {
throw ex;
} catch (Exception ex) {
throw new PdfException(PdfException.PdfEncryption, ex);
}
}
private static boolean compareArray(byte[] a, byte[] b, int len) {
for (int k = 0; k < len; ++k) {
if (a[k] != b[k]) {
return false;
}
}
return true;
}
}
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