/**
* Read in a public key from a provided Secure layer PDU, and store in this.exponent and
* this.modulus
*
* @param data Secure layer PDU containing key data
* @return True if key successfully read
* @throws RdesktopException
*/
public boolean parsePublicKey(RdpPacket_Localised data) throws RdesktopException {
int magic = 0, modulus_length = 0;
magic = data.getLittleEndian32();
if (magic != SEC_RSA_MAGIC) {
throw new RdesktopException("Wrong magic! Expected" + SEC_RSA_MAGIC + "got:" + magic);
}
modulus_length = data.getLittleEndian32() - SEC_PADDING_SIZE;
if (modulus_length < 64 || modulus_length > SEC_MAX_MODULUS_SIZE) {
throw new RdesktopException(
"Bad server public key size (" + (modulus_length * 8) + " bites)");
}
data.incrementPosition(8); // unknown modulus bits
this.exponent = new byte[SEC_EXPONENT_SIZE];
data.copyToByteArray(this.exponent, 0, data.getPosition(), SEC_EXPONENT_SIZE);
data.incrementPosition(SEC_EXPONENT_SIZE);
this.modulus = new byte[modulus_length];
data.copyToByteArray(this.modulus, 0, data.getPosition(), modulus_length);
data.incrementPosition(modulus_length);
data.incrementPosition(SEC_PADDING_SIZE);
this.server_public_key_len = modulus_length;
if (data.getPosition() <= data.getEnd()) {
return true;
} else {
return false;
}
}
/**
* Receive a Secure layer PDU from the MCS layer
*
* @return Packet representing received Secure PDU
* @throws RdesktopException
* @throws IOException
* @throws CryptoException
* @throws OrderException
*/
public RdpPacket_Localised receive()
throws RdesktopException, IOException, CryptoException, OrderException {
int sec_flags = 0;
RdpPacket_Localised buffer = null;
while (true) {
int[] channel = new int[1];
buffer = McsLayer.receive(channel);
if (buffer == null) return null;
buffer.setHeader(RdpPacket.SECURE_HEADER);
if (Constants.encryption || (!this.licenceIssued)) {
sec_flags = buffer.getLittleEndian32();
if ((sec_flags & SEC_LICENCE_NEG) != 0) {
licence.process(buffer);
continue;
}
if ((sec_flags & SEC_ENCRYPT) != 0) {
buffer.incrementPosition(8); // signature
byte[] data = new byte[buffer.size() - buffer.getPosition()];
buffer.copyToByteArray(data, 0, buffer.getPosition(), data.length);
byte[] packet = this.decrypt(data);
buffer.copyFromByteArray(packet, 0, buffer.getPosition(), packet.length);
// buffer.setStart(buffer.getPosition());
// return buffer;
}
}
if (channel[0] != MCS.MCS_GLOBAL_CHANNEL) {
channels.channel_process(buffer, channel[0]);
continue;
}
buffer.setStart(buffer.getPosition());
return buffer;
}
}
/**
* Read encryption information from a Secure layer PDU, obtaining and storing level of encryption
* and any keys received
*
* @param data Packet to read encryption information from
* @return Size of RC4 key
* @throws RdesktopException
*/
public int parseCryptInfo(RdpPacket_Localised data) throws RdesktopException {
logger.debug("Secure.parseCryptInfo");
int encryption_level = 0, random_length = 0, RSA_info_length = 0;
int tag = 0, length = 0;
int next_tag = 0, end = 0;
int rc4_key_size = 0;
rc4_key_size = data.getLittleEndian32(); // 1 = 40-Bit 2 = 128 Bit
encryption_level = data.getLittleEndian32(); // 1 = low, 2 = medium,
// 3 = high
if (encryption_level == 0) { // no encryption
return 0;
}
random_length = data.getLittleEndian32();
RSA_info_length = data.getLittleEndian32();
if (random_length != SEC_RANDOM_SIZE) {
throw new RdesktopException(
"Wrong Size of Random! Got" + random_length + "expected" + SEC_RANDOM_SIZE);
}
this.server_random = new byte[random_length];
data.copyToByteArray(this.server_random, 0, data.getPosition(), random_length);
data.incrementPosition(random_length);
end = data.getPosition() + RSA_info_length;
if (end > data.getEnd()) {
logger.debug("Reached end of crypt info prematurely ");
return 0;
}
// data.incrementPosition(12); // unknown bytes
int flags = data.getLittleEndian32(); // in_uint32_le(s, flags); // 1
// = RDP4-style, 0x80000002 =
// X.509
logger.debug("Flags = 0x" + Integer.toHexString(flags));
if ((flags & 1) != 0) {
logger.debug(("We're going for the RDP4-style encryption"));
data.incrementPosition(8); // in_uint8s(s, 8); // unknown
while (data.getPosition() < data.getEnd()) {
tag = data.getLittleEndian16();
length = data.getLittleEndian16();
next_tag = data.getPosition() + length;
switch (tag) {
case (Secure.SEC_TAG_PUBKEY):
if (!parsePublicKey(data)) {
return 0;
}
break;
case (Secure.SEC_TAG_KEYSIG):
// Microsoft issued a key but we don't care
break;
default:
throw new RdesktopException("Unimplemented decrypt tag " + tag);
}
data.setPosition(next_tag);
}
if (data.getPosition() == data.getEnd()) {
return rc4_key_size;
} else {
logger.warn("End not reached!");
return 0;
}
} else {
logger.debug(("We're going for the RDP5-style encryption"));
// data.incrementPosition(4); // number of certificates
int num_certs = data.getLittleEndian32();
int cacert_len = data.getLittleEndian32();
data.incrementPosition(cacert_len);
int cert_len = data.getLittleEndian32();
data.incrementPosition(cert_len);
readCert = true;
return rc4_key_size;
}
}