private void PrepareEncryptionDictAES(PdfEncryption encryptionDictionary, PdfName aesVName)
{
var cryptFilterDictionary = new PdfCryptFilterDictionary(encryptionDictionary.File);
cryptFilterDictionary.CryptFilterMethod = aesVName;
cryptFilterDictionary.Length = keyLength;
encryptionDictionary.StdCryptFilterDictionary = cryptFilterDictionary;
encryptionDictionary.StreamFilterName = PdfName.StdCF;
encryptionDictionary.StringFilterName = PdfName.StdCF;
IsAES = true;
}
private void PrepareEncryptionDictAES(PdfEncryption encryptionDictionary, PdfName aesVName, byte[][] recipients)
{
PdfCryptFilterDictionary cryptFilterDictionary = new PdfCryptFilterDictionary(encryptionDictionary.File);
cryptFilterDictionary.CryptFilterMethod = aesVName;
cryptFilterDictionary.Length = keyLength;
PdfArray array = new PdfArray();
foreach (byte[] recipient in recipients)
{
array.Add(new PdfString(recipient));
}
cryptFilterDictionary.BaseDataObject[PdfName.Recipients] = array;
//array.setDirect(true);
encryptionDictionary.DefaultCryptFilterDictionary = cryptFilterDictionary;
encryptionDictionary.StreamFilterName = PdfName.DefaultCryptFilter;
encryptionDictionary.StringFilterName = PdfName.DefaultCryptFilter;
//cryptFilterDictionary.getCOSObject().setDirect(true);
IsAES = true;
}
/**
* Prepares everything to decrypt the document.
*
* @param encryption encryption dictionary, can be retrieved via
* {@link Document#getEncryption()}
* @param documentIDArray document id which is returned via
* {@link org.apache.pdfbox.cos.COSDocument#getDocumentID()} (not used by
* this handler)
* @param decryptionMaterial Information used to decrypt the document.
*
* @throws IOException If there is an error accessing data. If verbose mode
* is enabled, the exception message will provide more details why the
* match wasn't successful.
*/
public override void PrepareForDecryption(PdfEncryption encryption, PdfArray documentIDArray, DecryptionMaterial decryptionMaterial)
{
if (!(decryptionMaterial is PublicKeyDecryptionMaterial))
{
throw new IOException(
"Provided decryption material is not compatible with the document");
}
SetDecryptMetadata(encryption.IsEncryptMetaData);
if (encryption.Length != 0)
{
this.keyLength = encryption.Length;
}
PublicKeyDecryptionMaterial material = (PublicKeyDecryptionMaterial)decryptionMaterial;
try
{
bool foundRecipient = false;
//Org.BouncyCastle.X509.Extension.
X509Certificate certificate = material.Certificate;
X509CertificateEntry materialCert = null;
if (certificate != null)
{
materialCert = new X509CertificateEntry(certificate);
}
// the decrypted content of the enveloped data that match
// the certificate in the decryption material provided
byte[] envelopedData = null;
// the bytes of each recipient in the recipients array
PdfArray array = (PdfArray)encryption.BaseDataObject.Resolve(PdfName.Recipients);
if (array == null)
{
PdfCryptFilterDictionary defaultCryptFilterDictionary = encryption.DefaultCryptFilterDictionary;
array = (PdfArray)defaultCryptFilterDictionary.BaseDataObject.Resolve(PdfName.Recipients);
}
byte[][] recipientFieldsBytes = new byte[array.Count][];
//TODO encryption.getRecipientsLength() and getRecipientStringAt() should be deprecated
int recipientFieldsLength = 0;
StringBuilder extraInfo = new StringBuilder();
for (int i = 0; i < array.Count; i++)
{
PdfString recipientFieldString = (PdfString)array.Resolve(i);
byte[] recipientBytes = recipientFieldString.GetBuffer();
CmsEnvelopedData data = new CmsEnvelopedData(recipientBytes);
var recipCertificatesIt = data.GetRecipientInfos().GetRecipients();
int j = 0;
foreach (RecipientInformation ri in recipCertificatesIt)
{
// Impl: if a matching certificate was previously found it is an error,
// here we just don't care about it
RecipientID rid = ri.RecipientID;
if (!foundRecipient && rid.Match(materialCert))
{
foundRecipient = true;
var privateKey = material.PrivateKey;
// might need to call setContentProvider() if we use PKI token, see
// http://bouncy-castle.1462172.n4.nabble.com/CMSException-exception-unwrapping-key-key-invalid-unknown-key-type-passed-to-RSA-td4658109.html
//DotNetUtilities.GetKeyPair(ri.AlgorithmIdentifier)
envelopedData = ri.GetContent(privateKey.Key);
break;
}
j++;
if (certificate != null)
{
extraInfo.Append('\n');
extraInfo.Append(j);
extraInfo.Append(": ");
if (ri is KeyTransRecipientInformation)
{
appendCertInfo(extraInfo, (KeyTransRecipientInformation)ri, certificate, materialCert);
}
}
}
recipientFieldsBytes[i] = recipientBytes;
recipientFieldsLength += recipientBytes.Length;
}
if (!foundRecipient || envelopedData == null)
{
throw new IOException("The certificate matches none of " + array.Count
+ " recipient entries" + extraInfo.ToString());
}
if (envelopedData.Length != 24)
{
throw new IOException("The enveloped data does not contain 24 bytes");
}
// now envelopedData contains:
// - the 20 bytes seed
// - the 4 bytes of permission for the current user
byte[] accessBytes = new byte[4];
Array.Copy(envelopedData, 20, accessBytes, 0, 4);
AccessPermission currentAccessPermission = new AccessPermission(accessBytes);
currentAccessPermission.IsReadOnly = true;
CurrentAccessPermission = currentAccessPermission;
// what we will put in the SHA1 = the seed + each byte contained in the recipients array
byte[] sha1Input = new byte[recipientFieldsLength + 20];
// put the seed in the sha1 input
Array.Copy(envelopedData, 0, sha1Input, 0, 20);
// put each bytes of the recipients array in the sha1 input
int sha1InputOffset = 20;
foreach (byte[] recipientFieldsByte in recipientFieldsBytes)
{
Array.Copy(recipientFieldsByte, 0, sha1Input, sha1InputOffset, recipientFieldsByte.Length);
sha1InputOffset += recipientFieldsByte.Length;
}
byte[] mdResult;
if (encryption.Version == 4 || encryption.Version == 5)
{
mdResult = SHA256.Create().Digest(sha1Input);
// detect whether AES encryption is used. This assumes that the encryption algo is
// stored in the PDCryptFilterDictionary
// However, crypt filters are used only when V is 4 or 5.
PdfCryptFilterDictionary defaultCryptFilterDictionary = encryption.DefaultCryptFilterDictionary;
if (defaultCryptFilterDictionary != null)
{
PdfName cryptFilterMethod = defaultCryptFilterDictionary.CryptFilterMethod;
IsAES = PdfName.AESV2.Equals(cryptFilterMethod) || PdfName.AESV3.Equals(cryptFilterMethod);
}
}
else
{
mdResult = SHA1.Create().Digest(sha1Input);
}
// we have the encryption key ...
encryptionKey = new byte[this.keyLength / 8];
Array.Copy(mdResult, 0, encryptionKey, 0, this.keyLength / 8);
}
catch (Exception e)
{
throw new IOException("", e);
}
}
