this.keyLength = encDictionary.getLength();
}
if(!(decryptionMaterial instanceof PublicKeyDecryptionMaterial))
{
throw new CryptographyException(
"Provided decryption material is not compatible with the document");
}
PublicKeyDecryptionMaterial material = (PublicKeyDecryptionMaterial)decryptionMaterial;
try
{
boolean foundRecipient = false;
// 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
byte[][] recipientFieldsBytes = new byte[encDictionary.getRecipientsLength()][];
int recipientFieldsLength = 0;
for(int i=0; i<encDictionary.getRecipientsLength(); i++)
{
COSString recipientFieldString = encDictionary.getRecipientStringAt(i);
byte[] recipientBytes = recipientFieldString.getBytes();
CMSEnvelopedData data = new CMSEnvelopedData(recipientBytes);
Iterator recipCertificatesIt = data.getRecipientInfos().getRecipients().iterator();
while(recipCertificatesIt.hasNext())
{
RecipientInformation ri =
(RecipientInformation)recipCertificatesIt.next();
// Impl: if a matching certificate was previously found it is an error,
// here we just don't care about it
if(ri.getRID().match(material.getCertificate()) && !foundRecipient)
{
foundRecipient = true;
envelopedData = ri.getContent(material.getPrivateKey(), "BC");
}
}
recipientFieldsBytes[i] = recipientBytes;
recipientFieldsLength += recipientBytes.length;
}
if(!foundRecipient || envelopedData == null)
{
throw new CryptographyException("The certificate matches no recipient entry");
}
if(envelopedData.length != 24)
{
throw new CryptographyException("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];
System.arraycopy(envelopedData, 20, accessBytes, 0, 4);
currentAccessPermission = new AccessPermission(accessBytes);
currentAccessPermission.setReadOnly();
// 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
System.arraycopy(envelopedData, 0, sha1Input, 0, 20);
// put each bytes of the recipients array in the sha1 input
int sha1InputOffset = 20;
for(int i=0; i<recipientFieldsBytes.length; i++)
{
System.arraycopy(
recipientFieldsBytes[i], 0,
sha1Input, sha1InputOffset, recipientFieldsBytes[i].length);
sha1InputOffset += recipientFieldsBytes[i].length;
}
MessageDigest md = MessageDigest.getInstance("SHA-1");
byte[] mdResult = md.digest(sha1Input);
// we have the encryption key ...
encryptionKey = new byte[this.keyLength/8];
System.arraycopy(mdResult, 0, encryptionKey, 0, this.keyLength/8);
}
catch(CMSException e)
{
throw new CryptographyException(e);
}
catch(KeyStoreException e)
{
throw new CryptographyException(e);
}
catch(NoSuchProviderException e)
{
throw new CryptographyException(e);
}
catch(NoSuchAlgorithmException e)
{
throw new CryptographyException(e);
}
}