/**
* instead of a password, it's also possible to decrypt via certificate.
* Warning: this code is experimental and hasn't been validated
*
* @see <a href="http://social.msdn.microsoft.com/Forums/en-US/cc9092bb-0c82-4b5b-ae21-abf643bdb37c/agile-encryption-with-certificates">Agile encryption with certificates</a>
*
* @param keyPair
* @param x509
* @return true, when the data can be successfully decrypted with the given private key
* @throws GeneralSecurityException
*/
public bool VerifyPassword(KeyPair keyPair, X509Certificate x509)
{
AgileEncryptionVerifier ver = (AgileEncryptionVerifier)builder.GetVerifier();
AgileEncryptionHeader header = (AgileEncryptionHeader)builder.GetHeader();
HashAlgorithm hashAlgo = header.HashAlgorithm;
CipherAlgorithm cipherAlgo = header.CipherAlgorithm;
int blockSize = header.BlockSize;
AgileCertificateEntry ace = null;
foreach (AgileCertificateEntry aceEntry in ver.GetCertificates())
{
if (x509.Equals(aceEntry.x509))
{
ace = aceEntry;
break;
}
}
if (ace == null)
{
return(false);
}
Cipher cipher = Cipher.GetInstance("RSA");
cipher.Init(Cipher.DECRYPT_MODE, keyPair.getPrivate());
byte[] keyspec = cipher.DoFinal(ace.encryptedKey);
SecretKeySpec secretKey = new SecretKeySpec(keyspec, ver.CipherAlgorithm.jceId);
Mac x509Hmac = CryptoFunctions.GetMac(hashAlgo);
x509Hmac.Init(secretKey);
byte[] certVerifier = x509Hmac.DoFinal(ace.x509.GetEncoded());
byte[] vec = CryptoFunctions.GenerateIv(hashAlgo, header.KeySalt, kIntegrityKeyBlock, blockSize);
cipher = GetCipher(secretKey, cipherAlgo, ver.ChainingMode, vec, Cipher.DECRYPT_MODE);
byte[] hmacKey = cipher.DoFinal(header.GetEncryptedHmacKey());
hmacKey = GetBlock0(hmacKey, hashAlgo.hashSize);
vec = CryptoFunctions.GenerateIv(hashAlgo, header.KeySalt, kIntegrityValueBlock, blockSize);
cipher = GetCipher(secretKey, cipherAlgo, ver.ChainingMode, vec, Cipher.DECRYPT_MODE);
byte[] hmacValue = cipher.DoFinal(header.GetEncryptedHmacValue());
hmacValue = GetBlock0(hmacValue, hashAlgo.hashSize);
if (Arrays.Equals(ace.certVerifier, certVerifier))
{
SetSecretKey(secretKey);
SetIntegrityHmacKey(hmacKey);
SetIntegrityHmacValue(hmacValue);
return(true);
}
else
{
return(false);
}
}
/**
* Generate an HMAC, as specified in [RFC2104], of the encrypted form of the data (message),
* which the DataIntegrity element will verify by using the Salt generated in step 2 as the key.
* Note that the entire EncryptedPackage stream (1), including the StreamSize field, MUST be
* used as the message.
*
* Encrypt the HMAC as in step 3 by using a blockKey byte array consisting of the following bytes:
* 0xa0, 0x67, 0x7f, 0x02, 0xb2, 0x2c, 0x84, and 0x33.
**/
protected void UpdateIntegrityHMAC(FileInfo tmpFile, int oleStreamSize)
{
// as the integrity hmac needs to contain the StreamSize,
// it's not possible to calculate it on-the-fly while buffering
// TODO: add stream size parameter to GetDataStream()
AgileEncryptionVerifier ver = builder.GetVerifier();
HashAlgorithm hashAlgo = ver.HashAlgorithm;
Mac integrityMD = CryptoFunctions.GetMac(hashAlgo);
integrityMD.Init(new SecretKeySpec(integritySalt, hashAlgo.jceHmacId));
byte[] buf = new byte[1024];
LittleEndian.PutLong(buf, 0, oleStreamSize);
integrityMD.Update(buf, 0, LittleEndian.LONG_SIZE);
FileStream fis = tmpFile.Create();
try {
int readBytes;
while ((readBytes = fis.Read(buf, 0, buf.Length)) > 0)
{
integrityMD.Update(buf, 0, readBytes);
}
} finally {
fis.Close();
}
byte[] hmacValue = integrityMD.DoFinal();
AgileEncryptionHeader header = builder.GetHeader();
int blockSize = header.BlockSize;
byte[] iv = CryptoFunctions.GenerateIv(header.HashAlgorithm, header.KeySalt, AgileDecryptor.kIntegrityValueBlock, blockSize);
Cipher cipher = CryptoFunctions.GetCipher(GetSecretKey(), header.CipherAlgorithm, header.ChainingMode, iv, Cipher.ENCRYPT_MODE);
byte[] hmacValueFilled = GetBlock0(hmacValue, AgileDecryptor.GetNextBlockSize(hmacValue.Length, blockSize));
byte[] encryptedHmacValue = cipher.DoFinal(hmacValueFilled);
header.SetEncryptedHmacValue(encryptedHmacValue);
}
public override void ConfirmPassword(String password, byte[] keySpec, byte[] keySalt, byte[] verifier, byte[] verifierSalt, byte[] integritySalt)
{
AgileEncryptionVerifier ver = builder.GetVerifier();
ver.Salt = (/*setter*/ verifierSalt);
AgileEncryptionHeader header = builder.GetHeader();
header.KeySalt = (/*setter*/ keySalt);
HashAlgorithm hashAlgo = ver.HashAlgorithm;
int blockSize = header.BlockSize;
pwHash = HashPassword(password, hashAlgo, verifierSalt, ver.SpinCount);
/**
* encryptedVerifierHashInput: This attribute MUST be generated by using the following steps:
* 1. Generate a random array of bytes with the number of bytes used specified by the saltSize
* attribute.
* 2. Generate an encryption key as specified in section 2.3.4.11 by using the user-supplied password,
* the binary byte array used to create the saltValue attribute, and a blockKey byte array
* consisting of the following bytes: 0xfe, 0xa7, 0xd2, 0x76, 0x3b, 0x4b, 0x9e, and 0x79.
* 3. Encrypt the random array of bytes generated in step 1 by using the binary form of the saltValue
* attribute as an Initialization vector as specified in section 2.3.4.12. If the array of bytes is not an
* integral multiple of blockSize bytes, pad the array with 0x00 to the next integral multiple of
* blockSize bytes.
* 4. Use base64 to encode the result of step 3.
*/
byte[] encryptedVerifier = AgileDecryptor.hashInput(builder, pwHash, AgileDecryptor.kVerifierInputBlock, verifier, Cipher.ENCRYPT_MODE);
ver.EncryptedVerifier = (/*setter*/ encryptedVerifier);
/**
* encryptedVerifierHashValue: This attribute MUST be generated by using the following steps:
* 1. Obtain the hash value of the random array of bytes generated in step 1 of the steps for
* encryptedVerifierHashInput.
* 2. Generate an encryption key as specified in section 2.3.4.11 by using the user-supplied password,
* the binary byte array used to create the saltValue attribute, and a blockKey byte array
* consisting of the following bytes: 0xd7, 0xaa, 0x0f, 0x6d, 0x30, 0x61, 0x34, and 0x4e.
* 3. Encrypt the hash value obtained in step 1 by using the binary form of the saltValue attribute as
* an Initialization vector as specified in section 2.3.4.12. If hashSize is not an integral multiple of
* blockSize bytes, pad the hash value with 0x00 to an integral multiple of blockSize bytes.
* 4. Use base64 to encode the result of step 3.
*/
MessageDigest hashMD = GetMessageDigest(hashAlgo);
byte[] hashedVerifier = hashMD.Digest(verifier);
byte[] encryptedVerifierHash = AgileDecryptor.hashInput(builder, pwHash, AgileDecryptor.kHashedVerifierBlock, hashedVerifier, Cipher.ENCRYPT_MODE);
ver.EncryptedVerifierHash = (/*setter*/ encryptedVerifierHash);
/**
* encryptedKeyValue: This attribute MUST be generated by using the following steps:
* 1. Generate a random array of bytes that is the same size as specified by the
* Encryptor.KeyData.keyBits attribute of the parent element.
* 2. Generate an encryption key as specified in section 2.3.4.11, using the user-supplied password,
* the binary byte array used to create the saltValue attribute, and a blockKey byte array
* consisting of the following bytes: 0x14, 0x6e, 0x0b, 0xe7, 0xab, 0xac, 0xd0, and 0xd6.
* 3. Encrypt the random array of bytes generated in step 1 by using the binary form of the saltValue
* attribute as an Initialization vector as specified in section 2.3.4.12. If the array of bytes is not an
* integral multiple of blockSize bytes, pad the array with 0x00 to an integral multiple of
* blockSize bytes.
* 4. Use base64 to encode the result of step 3.
*/
byte[] encryptedKey = AgileDecryptor.hashInput(builder, pwHash, AgileDecryptor.kCryptoKeyBlock, keySpec, Cipher.ENCRYPT_MODE);
ver.EncryptedKey = (/*setter*/ encryptedKey);
ISecretKey secretKey = new SecretKeySpec(keySpec, ver.CipherAlgorithm.jceId);
SetSecretKey(secretKey);
/*
* 2.3.4.14 DataIntegrity Generation (Agile Encryption)
*
* The DataIntegrity element Contained within an Encryption element MUST be generated by using
* the following steps:
* 1. Obtain the intermediate key by decrypting the encryptedKeyValue from a KeyEncryptor
* Contained within the KeyEncryptors sequence. Use this key for encryption operations in the
* remaining steps of this section.
* 2. Generate a random array of bytes, known as Salt, of the same length as the value of the
* KeyData.HashSize attribute.
* 3. Encrypt the random array of bytes generated in step 2 by using the binary form of the
* KeyData.saltValue attribute and a blockKey byte array consisting of the following bytes:
* 0x5f, 0xb2, 0xad, 0x01, 0x0c, 0xb9, 0xe1, and 0xf6 used to form an Initialization vector as
* specified in section 2.3.4.12. If the array of bytes is not an integral multiple of blockSize
* bytes, pad the array with 0x00 to the next integral multiple of blockSize bytes.
* 4. Assign the encryptedHmacKey attribute to the base64-encoded form of the result of step 3.
* 5. Generate an HMAC, as specified in [RFC2104], of the encrypted form of the data (message),
* which the DataIntegrity element will verify by using the Salt generated in step 2 as the key.
* Note that the entire EncryptedPackage stream (1), including the StreamSize field, MUST be
* used as the message.
* 6. Encrypt the HMAC as in step 3 by using a blockKey byte array consisting of the following bytes:
* 0xa0, 0x67, 0x7f, 0x02, 0xb2, 0x2c, 0x84, and 0x33.
* 7. Assign the encryptedHmacValue attribute to the base64-encoded form of the result of step 6.
*/
this.integritySalt = integritySalt;
try {
byte[] vec = CryptoFunctions.GenerateIv(hashAlgo, header.KeySalt, AgileDecryptor.kIntegrityKeyBlock, header.BlockSize);
Cipher cipher = GetCipher(secretKey, ver.CipherAlgorithm, ver.ChainingMode, vec, Cipher.ENCRYPT_MODE);
byte[] FilledSalt = GetBlock0(integritySalt, AgileDecryptor.GetNextBlockSize(integritySalt.Length, blockSize));
byte[] encryptedHmacKey = cipher.DoFinal(FilledSalt);
header.SetEncryptedHmacKey(encryptedHmacKey);
cipher = Cipher.GetInstance("RSA");
foreach (AgileCertificateEntry ace in ver.GetCertificates())
{
cipher.Init(Cipher.ENCRYPT_MODE, ace.x509.GetPublicKey());
ace.encryptedKey = cipher.DoFinal(GetSecretKey().GetEncoded());
Mac x509Hmac = CryptoFunctions.GetMac(hashAlgo);
x509Hmac.Init(GetSecretKey());
ace.certVerifier = x509Hmac.DoFinal(ace.x509.GetEncoded());
}
} catch (Exception e) {
throw new EncryptedDocumentException(e);
}
}