private void InitR4(string password)
{
// didn't want to copy code and also didn't want to inherit from RC4Encryptor, so use this kinda "hackish" way... TODO: cleanup
var rce = new RC4Encryptor(doc, EncryptionMode.Decrypt);
rce.ValidatePassword(password);
computedOwnerValue = rce.computedOwnerValue;
computedUserValue = rce.computedUserValue;
encryptionKey = rce.encryptionKey;
HaveOwnerPermission = rce.HaveOwnerPermission;
PasswordValid = rce.PasswordValid;
}
/// <summary>
/// Prepares decryption of a loaded document
/// </summary>
/// <param name="doc"></param>
/// <param name="dict"></param>
/// <param name="stringEncryptor"></param>
/// <param name="streamEncryptor"></param>
public static void InitDecryption(PdfDocument doc, PdfDictionary dict, out IEncryptor stringEncryptor, out IEncryptor streamEncryptor)
{
stringEncryptor = streamEncryptor = null;
var filter = dict.Elements.GetName(PdfSecurityHandler.Keys.Filter);
var v = dict.Elements.GetInteger(PdfSecurityHandler.Keys.V);
if (filter != "/Standard" || !(v >= 1 && v <= 5))
{
throw new PdfReaderException(PSSR.UnknownEncryption);
}
foreach (var keyName in new[] { PdfSecurityHandler.Keys.StrF, PdfSecurityHandler.Keys.StmF })
{
IEncryptor encryptor = null;
if (v >= 4)
{
var cf = dict.Elements.GetDictionary(PdfSecurityHandler.Keys.CF);
if (cf != null)
{
var filterName = dict.Elements.GetName(keyName);
if (!String.IsNullOrEmpty(filterName))
{
/*
* Pdf Reference 1.7 Chapter 7.6.5 (Crypt Filters)
*
* None: The application shall not decrypt data but shall direct the input stream to the security handler for decryption.
* V2: The application shall ask the security handler for the encryption key and shall implicitly decrypt data with
* "Algorithm 1: Encryption of data using the RC4 or AES algorithms", using the RC4 algorithm.
* AESV2: (PDF 1.6)The application shall ask the security handler for the encryption key and shall implicitly decrypt data with
* "Algorithm 1: Encryption of data using the RC4 or AES algorithms", using the AES algorithm in Cipher Block
* Chaining (CBC) mode with a 16-byte block size and an initialization vector that shall be randomly generated and
* placed as the first 16 bytes in the stream or string.
* AESV3: (PDF 1.7, ExtensionLevel 3) The application asks the security handler for the encryption key and implicitly decrypts data with
* Algorithm 3.1a, using the AES-256 algorithm in Cipher Block Chaining (CBC) with padding mode with a 16-byte block size and an
* initialization vector that is randomly generated and placed as the first 16 bytes in the stream or string.
* The key size (Length) shall be 256 bits.
*/
var filterDict = cf.Elements.GetDictionary(filterName);
if (filterDict != null)
{
var cfm = filterDict.Elements.GetName(PdfSecurityHandler.Keys.CFM);
if (!String.IsNullOrEmpty(cfm) && cfm.StartsWith("/AESV")) // AESV2(PDF 1.6), AESV3(PDF 1.7, ExtensionLevel 3)
{
encryptor = new AESEncryptor(doc, EncryptionMode.Decrypt);
}
}
}
}
}
// If CFM is "V2", use RC4 encryption
if (encryptor == null)
{
encryptor = new RC4Encryptor(doc, EncryptionMode.Decrypt);
}
if (keyName == PdfSecurityHandler.Keys.StrF)
{
stringEncryptor = encryptor;
}
else
{
streamEncryptor = encryptor;
}
}
}
