Re: SSL3_GET_CLIENT_KEY_EXCHANGE

29 Sep 2005

      ...
The protocol specification describes this.  The implementation in
src/modules/rlm_eap/ contains diagrams of the packets it expects to
receive.
Alan DeKok.
Thank you Alan, but now I have a new problem. I have been reading the
src/modules/rlm_eap/ to understand my problem but I don't find the
issue. In TLS establishment, the public key in the server.cert is 128
bytes length. I generate a random string of 46 bytes and the protocol
version (TLS 1.0 (0x03, 0x01)) and I use the SSL function
RSA_public_encrypt() with server's public key to encrypt the
PreMasterSecret. As a result I get a 128 length string. As I send this
data to the server, I get a "tls rsa encrypted length is wrong:
s3_srvr.c: 1450:"

Can anybody please tell me where can be my problem?  Here is my code
for exemple.

void Client_Key_Exchange (SSLData *ClientSSLData, unsigned short
*length, char *HandshakeMessages, unsigned short *length_Hndshk, char
*buff)
{

	char *PreMasterSecret		      = (char*) _MEMORY_Allocate (58 , true);
	char *EncryptedPreMasterSecret	= (char*) _MEMORY_Allocate (128, true);
	char *temp			            = (char*) _MEMORY_Allocate (58 , true);
	unsigned char *tmpCert		      =  _MEMORY_Allocate

(ClientSSLData->certificate_len + 128, true);

	_RANDOM_MakeCharString (temp, 46);

	PreMasterSecret [0] = 0x03;
	PreMasterSecret [1] = 0x01;

	for (register int i = 0; i<46; i++)
	{
		PreMasterSecret[i+2]				= temp [i];
		ClientSSLData->PreMasterSecret[i]	= PreMasterSecret[i];
	}

	for (i = 0; i < ClientSSLData->certificate_len; i++)
		tmpCert[i] =(unsigned char) ClientSSLData->certificate[i];

	//----- OpenSSL Functions -----
	RSA		 *server_public_key;

	X509	 *cert				= X509_new ();

	EVP_PKEY *evp				= EVP_PKEY_new ();

	X509	 *err = d2i_X509 (&cert, (unsigned char**) &tmpCert,
                                            (ClientSSLData->certificate_len) );

	//----- d2i_509 Function retrives tmpCert pointer advanced the number
of bytes read -----
	tmpCert = tmpCert - (ClientSSLData->certificate_len);

	//----- We get the public key from the Server certificate -----
	evp	 = X509_get_pubkey(cert);

	server_public_key = (RSA *) evp->pkey.ptr;

	int rsasize = RSA_size(server_public_key);

	//----- We get the PreMasterSecret encrypted -----
	int Encrypted_len = RSA_public_encrypt(48, (BYTE*) PreMasterSecret,
(unsigned char*)EncryptedPreMasterSecret, server_public_key,
RSA_PKCS1_PADDING);

	ClientSSLData->bufferSSL[(*length)++] = 0x16;		// Handshake Message
	ClientSSLData->bufferSSL[(*length)++] = 0x03;		// Version
	ClientSSLData->bufferSSL[(*length)++] = 0x01;		// Version
	ClientSSLData->bufferSSL[(*length)++] = (Encrypted_len + 6) / 256;	// Length
	ClientSSLData->bufferSSL[(*length)++] = (Encrypted_len + 6) % 256;	// Length
  	ClientSSLData->bufferSSL[(*length)++] = 0x10;		// Client key exchange
	ClientSSLData->bufferSSL[(*length)++] = 0x00;					 // Length
  	ClientSSLData->bufferSSL[(*length)++] = (Encrypted_len ) / 256;		  // Length
	ClientSSLData->bufferSSL[(*length)++] = (Encrypted_len ) % 256;		// Length

	//----- Public key exchange -----
	for (i = 0; i < Encrypted_len; i++)
	{
		buff[i]	 =  EncryptedPreMasterSecret[i];
		HandshakeMessages[(*length_Hndshk)++]	= EncryptedPreMasterSecret[i];
	}

	free (PreMasterSecret);
	free (EncryptedPreMasterSecret);
	free (temp);
	free (tmpCert);

}

Thank you for your help. Juan Daniel MORENO

Re: SSL3_GET_CLIENT_KEY_EXCHANGE

Juan Daniel Moreno