/**
* Computes the checksum based on the algorithm stored in the tokenHeader.
*
* @param data the application data
* @param offset the offset where the data begins
* @param len the length of the application data
* @throws GSSException if an error occurs in the checksum calculation.
*/
byte[] getChecksum(byte[] data, int offset, int len) throws GSSException {
// debug("Will do getChecksum:\n");
/*
* For checksum calculation the token header bytes i.e., the first 16
* bytes following the GSSHeader, are logically prepended to the
* application data to bind the data to this particular token.
*
* Note: There is no such requirement wrt adding padding to the
* application data for checksumming, although the cryptographic
* algorithm used might itself apply some padding.
*/
byte[] tokenHeaderBytes = tokenHeader.getBytes();
// check confidentiality
int conf_flag = tokenHeaderBytes[TOKEN_FLAG_POS] & FLAG_WRAP_CONFIDENTIAL;
// clear EC and RRC in token header for checksum calculation
if ((conf_flag == 0) && (tokenId == WRAP_ID_v2)) {
tokenHeaderBytes[4] = 0;
tokenHeaderBytes[5] = 0;
tokenHeaderBytes[6] = 0;
tokenHeaderBytes[7] = 0;
}
return cipherHelper.calculateChecksum(tokenHeaderBytes, data, offset, len, key_usage);
}
/**
* Generates the checksum field and the sequence number field.
*
* @param prop the MessageProp structure
* @param data the application data to checksum
* @param offset the offset where the data starts
* @param len the length of the data
* @throws GSSException if an error occurs in the checksum calculation or sequence number
* calculation.
*/
public void genSignAndSeqNumber(MessageProp prop, byte[] data, int offset, int len)
throws GSSException {
// debug("Inside MessageToken.genSignAndSeqNumber:\n");
int qop = prop.getQOP();
if (qop != 0) {
qop = 0;
prop.setQOP(qop);
}
if (!confState) {
prop.setPrivacy(false);
}
// Create a new gss token header as defined in RFC 4121
tokenHeader = new MessageTokenHeader(tokenId, prop.getPrivacy());
// debug("\n\t Message Header = " +
// getHexBytes(tokenHeader.getBytes(), tokenHeader.getBytes().length));
// set key_usage
if (tokenId == Krb5Token.WRAP_ID_v2) {
key_usage = (initiator ? KG_USAGE_INITIATOR_SEAL : KG_USAGE_ACCEPTOR_SEAL);
} else if (tokenId == Krb5Token.MIC_ID_v2) {
key_usage = (initiator ? KG_USAGE_INITIATOR_SIGN : KG_USAGE_ACCEPTOR_SIGN);
}
// Calculate SGN_CKSUM
if ((tokenId == MIC_ID_v2) || (!prop.getPrivacy() && (tokenId == WRAP_ID_v2))) {
checksum = getChecksum(data, offset, len);
// debug("\n\tCalc checksum=" +
// getHexBytes(checksum, checksum.length));
}
// In Wrap tokens without confidentiality, the EC field SHALL be used
// to encode the number of octets in the trailing checksum
if (!prop.getPrivacy() && (tokenId == WRAP_ID_v2)) {
byte[] tok_header = tokenHeader.getBytes();
tok_header[4] = (byte) (checksum.length >>> 8);
tok_header[5] = (byte) (checksum.length);
}
}
protected final byte[] getTokenHeader() {
return (tokenHeader.getBytes());
}
/**
* Encodes a MessageTokenHeader onto an OutputStream.
*
* @param os the OutputStream to which this should be written
* @throws IOException is an error occurs while writing to the OutputStream
*/
protected void encodeHeader(OutputStream os) throws IOException {
tokenHeader.encode(os);
}
