licence.cpp

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/*
   rdesktop: A Remote Desktop Protocol client.
   RDP licensing negotiation
   Copyright (C) Matthew Chapman 1999-2002
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "rdesktop.h"

#ifdef WITH_OPENSSL
#include <openssl/rc4.h>
#else
#include "crypto/rc4.h"
#endif

extern char username[16];
extern char hostname[16];

static uint8 licence_key[16];
static uint8 licence_sign_key[16];

BOOL licence_issued = False;

/* Generate a session key and RC4 keys, given client and server randoms */
static void
licence_generate_keys(uint8 * client_key, uint8 * server_key, uint8 * client_rsa)
{
        uint8 session_key[48];
        uint8 temp_hash[48];

        /* Generate session key - two rounds of sec_hash_48 */
        sec_hash_48(temp_hash, client_rsa, client_key, server_key, 65);
        sec_hash_48(session_key, temp_hash, server_key, client_key, 65);

        /* Store first 16 bytes of session key, for generating signatures */
        memcpy(licence_sign_key, session_key, 16);

        /* Generate RC4 key */
        sec_hash_16(licence_key, &session_key[16], client_key, server_key);
}

static void
licence_generate_hwid(uint8 * hwid)
{
        buf_out_uint32(hwid, 2);
        strncpy((char *) (hwid + 4), hostname, LICENCE_HWID_SIZE - 4);
}

/* Present an existing licence to the server */
static void
licence_present(uint8 * client_random, uint8 * rsa_data,
                uint8 * licence_data, int licence_size, uint8 * hwid, uint8 * signature)
{
        uint32 sec_flags = SEC_LICENCE_NEG;
        uint16 length =
                16 + SEC_RANDOM_SIZE + SEC_MODULUS_SIZE + SEC_PADDING_SIZE +
                licence_size + LICENCE_HWID_SIZE + LICENCE_SIGNATURE_SIZE;
        STREAM s;

        s = sec_init(sec_flags, length + 4);

        out_uint16_le(s, LICENCE_TAG_PRESENT);
        out_uint16_le(s, length);

        out_uint32_le(s, 1);
        out_uint16(s, 0);
        out_uint16_le(s, 0x0201);

        out_uint8p(s, client_random, SEC_RANDOM_SIZE);
        out_uint16(s, 0);
        out_uint16_le(s, (SEC_MODULUS_SIZE + SEC_PADDING_SIZE));
        out_uint8p(s, rsa_data, SEC_MODULUS_SIZE);
        out_uint8s(s, SEC_PADDING_SIZE);

        out_uint16_le(s, 1);
        out_uint16_le(s, licence_size);
        out_uint8p(s, licence_data, licence_size);

        out_uint16_le(s, 1);
        out_uint16_le(s, LICENCE_HWID_SIZE);
        out_uint8p(s, hwid, LICENCE_HWID_SIZE);

        out_uint8p(s, signature, LICENCE_SIGNATURE_SIZE);

        s_mark_end(s);
        sec_send(s, sec_flags);
}

/* Send a licence request packet */
static void
licence_send_request(uint8 * client_random, uint8 * rsa_data, char *user, char *host)
{
        uint32 sec_flags = SEC_LICENCE_NEG;
        uint16 userlen = strlen(user) + 1;
        uint16 hostlen = strlen(host) + 1;
        uint16 length = 128 + userlen + hostlen;
        STREAM s;

        s = sec_init(sec_flags, length + 2);

        out_uint16_le(s, LICENCE_TAG_REQUEST);
        out_uint16_le(s, length);

        out_uint32_le(s, 1);
        out_uint16(s, 0);
        out_uint16_le(s, 0xff01);

        out_uint8p(s, client_random, SEC_RANDOM_SIZE);
        out_uint16(s, 0);
        out_uint16_le(s, (SEC_MODULUS_SIZE + SEC_PADDING_SIZE));
        out_uint8p(s, rsa_data, SEC_MODULUS_SIZE);
        out_uint8s(s, SEC_PADDING_SIZE);

        out_uint16(s, LICENCE_TAG_USER);
        out_uint16(s, userlen);
        out_uint8p(s, user, userlen);

        out_uint16(s, LICENCE_TAG_HOST);
        out_uint16(s, hostlen);
        out_uint8p(s, host, hostlen);

        s_mark_end(s);
        sec_send(s, sec_flags);
}

/* Process a licence demand packet */
static void
licence_process_demand(STREAM s)
{
        uint8 null_data[SEC_MODULUS_SIZE];
        uint8 *server_random;
        uint8 signature[LICENCE_SIGNATURE_SIZE];
        uint8 hwid[LICENCE_HWID_SIZE];
        uint8 *licence_data;
        int licence_size;
        RC4_KEY crypt_key;

        /* Retrieve the server random from the incoming packet */
        in_uint8p(s, server_random, SEC_RANDOM_SIZE);

        /* We currently use null client keys. This is a bit naughty but, hey,
           the security of licence negotiation isn't exactly paramount. */
        memset(null_data, 0, sizeof(null_data));
        licence_generate_keys(null_data, server_random, null_data);

        licence_size = load_licence(&licence_data);
        if (licence_size != -1)
        {
                /* Generate a signature for the HWID buffer */
                licence_generate_hwid(hwid);
                sec_sign(signature, 16, licence_sign_key, 16, hwid, sizeof(hwid));

                /* Now encrypt the HWID */
                RC4_set_key(&crypt_key, 16, licence_key);
                RC4(&crypt_key, sizeof(hwid), hwid, hwid);

                licence_present(null_data, null_data, licence_data, licence_size, hwid, signature);
                xfree(licence_data);
                return;
        }

        licence_send_request(null_data, null_data, username, hostname);
}

/* Send an authentication response packet */
static void
licence_send_authresp(uint8 * token, uint8 * crypt_hwid, uint8 * signature)
{
        uint32 sec_flags = SEC_LICENCE_NEG;
        uint16 length = 58;
        STREAM s;

        s = sec_init(sec_flags, length + 2);

        out_uint16_le(s, LICENCE_TAG_AUTHRESP);
        out_uint16_le(s, length);

        out_uint16_le(s, 1);
        out_uint16_le(s, LICENCE_TOKEN_SIZE);
        out_uint8p(s, token, LICENCE_TOKEN_SIZE);

        out_uint16_le(s, 1);
        out_uint16_le(s, LICENCE_HWID_SIZE);
        out_uint8p(s, crypt_hwid, LICENCE_HWID_SIZE);

        out_uint8p(s, signature, LICENCE_SIGNATURE_SIZE);

        s_mark_end(s);
        sec_send(s, sec_flags);
}

/* Parse an authentication request packet */
static BOOL
licence_parse_authreq(STREAM s, uint8 ** token, uint8 ** signature)
{
        uint16 tokenlen;

        in_uint8s(s, 6);        /* unknown: f8 3d 15 00 04 f6 */

        in_uint16_le(s, tokenlen);
        if (tokenlen != LICENCE_TOKEN_SIZE)
        {
                error("token len %d\n", tokenlen);
                return False;
        }

        in_uint8p(s, *token, tokenlen);
        in_uint8p(s, *signature, LICENCE_SIGNATURE_SIZE);

        return s_check_end(s);
}

/* Process an authentication request packet */
static void
licence_process_authreq(STREAM s)
{
        uint8 *in_token, *in_sig;
        uint8 out_token[LICENCE_TOKEN_SIZE], decrypt_token[LICENCE_TOKEN_SIZE];
        uint8 hwid[LICENCE_HWID_SIZE], crypt_hwid[LICENCE_HWID_SIZE];
        uint8 sealed_buffer[LICENCE_TOKEN_SIZE + LICENCE_HWID_SIZE];
        uint8 out_sig[LICENCE_SIGNATURE_SIZE];
        RC4_KEY crypt_key;

        /* Parse incoming packet and save the encrypted token */
        licence_parse_authreq(s, &in_token, &in_sig);
        memcpy(out_token, in_token, LICENCE_TOKEN_SIZE);

        /* Decrypt the token. It should read TEST in Unicode. */
        RC4_set_key(&crypt_key, 16, licence_key);
        RC4(&crypt_key, LICENCE_TOKEN_SIZE, in_token, decrypt_token);

        /* Generate a signature for a buffer of token and HWID */
        licence_generate_hwid(hwid);
        memcpy(sealed_buffer, decrypt_token, LICENCE_TOKEN_SIZE);
        memcpy(sealed_buffer + LICENCE_TOKEN_SIZE, hwid, LICENCE_HWID_SIZE);
        sec_sign(out_sig, 16, licence_sign_key, 16, sealed_buffer, sizeof(sealed_buffer));

        /* Now encrypt the HWID */
        RC4_set_key(&crypt_key, 16, licence_key);
        RC4(&crypt_key, LICENCE_HWID_SIZE, hwid, crypt_hwid);

        licence_send_authresp(out_token, crypt_hwid, out_sig);
}

/* Process an licence issue packet */
static void
licence_process_issue(STREAM s)
{
        RC4_KEY crypt_key;
        uint32 length;
        uint16 check;

        in_uint8s(s, 2);        /* 3d 45 - unknown */
        in_uint16_le(s, length);
        if (!s_check_rem(s, length))
                return;

        RC4_set_key(&crypt_key, 16, licence_key);
        RC4(&crypt_key, length, s->p, s->p);

        in_uint16(s, check);
        if (check != 0)
                return;

        licence_issued = True;
        save_licence(s->p, length - 2);
}

/* Process a licence packet */
void
licence_process(STREAM s)
{
        uint16 tag;

        in_uint16_le(s, tag);
        in_uint8s(s, 2);        /* length */

        switch (tag)
        {
                case LICENCE_TAG_DEMAND:
                        licence_process_demand(s);
                        break;

                case LICENCE_TAG_AUTHREQ:
                        licence_process_authreq(s);
                        break;

                case LICENCE_TAG_ISSUE:
                        licence_process_issue(s);
                        break;

                case LICENCE_TAG_REISSUE:
                        break;

                case LICENCE_TAG_RESULT:
                        break;

                default:
                        unimpl("licence tag 0x%x\n", tag);
        }
}

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