/**
* 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);
}
/**
* Constructs a MessageToken from an InputStream. Bytes will be read on demand and the thread
* might block if there are not enough bytes to complete the token. Please note there is no
* accurate way to find out the size of a token, but we try our best to make sure there is enough
* bytes to construct one.
*
* @param tokenId the token id that should be contained in this token as it is read.
* @param context the Kerberos context associated with this token
* @param is the InputStream from which to read
* @param prop the MessageProp structure in which the properties of the token should be stored.
* @throws GSSException if there is a problem reading from the InputStream or parsing the token
*/
MessageToken_v2(int tokenId, Krb5Context context, InputStream is, MessageProp prop)
throws GSSException {
init(tokenId, context);
try {
if (!confState) {
prop.setPrivacy(false);
}
tokenHeader = new MessageTokenHeader(is, prop, tokenId);
// 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);
}
int minSize = 0; // minimal size for token data
if (tokenId == Krb5Token.WRAP_ID_v2 && prop.getPrivacy()) {
minSize = CONFOUNDER_SIZE + TOKEN_HEADER_SIZE + cipherHelper.getChecksumLength();
} else {
minSize = cipherHelper.getChecksumLength();
}
// Read token data
if (tokenId == Krb5Token.MIC_ID_v2) {
// The only case we can precisely predict the token data length
tokenDataLen = minSize;
tokenData = new byte[minSize];
readFully(is, tokenData);
} else {
tokenDataLen = is.available();
if (tokenDataLen >= minSize) { // read in one shot
tokenData = new byte[tokenDataLen];
readFully(is, tokenData);
} else {
byte[] tmp = new byte[minSize];
readFully(is, tmp);
// Hope while blocked in the read above, more data would
// come and is.available() below contains the whole token.
int more = is.available();
tokenDataLen = minSize + more;
tokenData = Arrays.copyOf(tmp, tokenDataLen);
readFully(is, tokenData, minSize, more);
}
}
if (tokenId == Krb5Token.WRAP_ID_v2) {
rotate();
}
if (tokenId == Krb5Token.MIC_ID_v2
|| (tokenId == Krb5Token.WRAP_ID_v2 && !prop.getPrivacy())) {
// Read checksum
int chkLen = cipherHelper.getChecksumLength();
checksum = new byte[chkLen];
System.arraycopy(tokenData, tokenDataLen - chkLen, checksum, 0, chkLen);
// validate EC for Wrap tokens without confidentiality
if (tokenId == Krb5Token.WRAP_ID_v2 && !prop.getPrivacy()) {
if (chkLen != ec) {
throw new GSSException(
GSSException.DEFECTIVE_TOKEN, -1, getTokenName(tokenId) + ":" + "EC incorrect!");
}
}
}
} catch (IOException e) {
throw new GSSException(
GSSException.DEFECTIVE_TOKEN, -1, getTokenName(tokenId) + ":" + e.getMessage());
}
}