licence.c

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/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   RDP licensing negotiation
   Copyright (C) Matthew Chapman 1999-2005
 
   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.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
 
#include "rdesktop.h"
#include <openssl/rc4.h> // TODO: remove dependency on OpenSSL
 
/* Generate a session key and RC4 keys, given client and server randoms */
static void
licence_generate_keys(RDPCLIENT * This, uint8 * client_random, uint8 * server_random, uint8 * pre_master_secret)
{
    uint8 master_secret[48];
    uint8 key_block[48];
 
    /* Generate master secret and then key material */
    sec_hash_48(master_secret, pre_master_secret, client_random, server_random, 'A');
    sec_hash_48(key_block, master_secret, server_random, client_random, 'A');
 
    /* Store first 16 bytes of session key as MAC secret */
    memcpy(This->licence.sign_key, key_block, 16);
 
    /* Generate RC4 key from next 16 bytes */
    sec_hash_16(This->licence.key, &key_block[16], client_random, server_random);
}
 
static void
licence_generate_hwid(RDPCLIENT * This, uint8 * hwid)
{
    buf_out_uint32(hwid, 2);
    strncpy((char *) (hwid + 4), This->licence_hostname, LICENCE_HWID_SIZE - 4);
}
 
/* Present an existing licence to the server */
static BOOL
licence_present(RDPCLIENT * This, 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(This, sec_flags, length + 4);
 
    if(s == NULL)
        return False;
 
    out_uint8(s, LICENCE_TAG_PRESENT);
    out_uint8(s, 2);    /* version */
    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);
    return sec_send(This, s, sec_flags);
}
 
/* Send a licence request packet */
static BOOL
licence_send_request(RDPCLIENT * This, uint8 * client_random, uint8 * rsa_data, char *user, char *host)
{
    uint32 sec_flags = SEC_LICENCE_NEG;
    uint16 userlen = (uint16)strlen(user) + 1;
    uint16 hostlen = (uint16)strlen(host) + 1;
    uint16 length = 128 + userlen + hostlen;
    STREAM s;
 
    s = sec_init(This, sec_flags, length + 2);
 
    if(s == NULL)
        return False;
 
    out_uint8(s, LICENCE_TAG_REQUEST);
    out_uint8(s, 2);    /* version */
    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_le(s, LICENCE_TAG_USER);
    out_uint16_le(s, userlen);
    out_uint8p(s, user, userlen);
 
    out_uint16_le(s, LICENCE_TAG_HOST);
    out_uint16_le(s, hostlen);
    out_uint8p(s, host, hostlen);
 
    s_mark_end(s);
    return sec_send(This, s, sec_flags);
}
 
/* Process a licence demand packet */
static BOOL
licence_process_demand(RDPCLIENT * This, 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(This, null_data, server_random, null_data);
 
    licence_size = load_licence(This, &licence_data);
    if (licence_size > 0)
    {
        /* Generate a signature for the HWID buffer */
        licence_generate_hwid(This, hwid);
        sec_sign(signature, 16, This->licence.sign_key, 16, hwid, sizeof(hwid));
 
        /* Now encrypt the HWID */
        RC4_set_key(&crypt_key, 16, This->licence.key);
        RC4(&crypt_key, sizeof(hwid), hwid, hwid);
 
        if(!licence_present(This, null_data, null_data, licence_data, licence_size, hwid, signature))
            return False;
 
        free(licence_data);
        return True;
    }
 
    return licence_send_request(This, null_data, null_data, This->licence_username, This->licence_hostname);
}
 
/* Send an authentication response packet */
static BOOL
licence_send_authresp(RDPCLIENT * This, uint8 * token, uint8 * crypt_hwid, uint8 * signature)
{
    uint32 sec_flags = SEC_LICENCE_NEG;
    uint16 length = 58;
    STREAM s;
 
    s = sec_init(This, sec_flags, length + 2);
 
    if(s == NULL)
        return False;
 
    out_uint8(s, LICENCE_TAG_AUTHRESP);
    out_uint8(s, 2);    /* version */
    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);
    return sec_send(This, 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(RDPCLIENT * This, 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, This->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(This, hwid);
    memcpy(sealed_buffer, decrypt_token, LICENCE_TOKEN_SIZE);
    memcpy(sealed_buffer + LICENCE_TOKEN_SIZE, hwid, LICENCE_HWID_SIZE);
    sec_sign(out_sig, 16, This->licence.sign_key, 16, sealed_buffer, sizeof(sealed_buffer));
 
    /* Now encrypt the HWID */
    RC4_set_key(&crypt_key, 16, This->licence.key);
    RC4(&crypt_key, LICENCE_HWID_SIZE, hwid, crypt_hwid);
 
    licence_send_authresp(This, out_token, crypt_hwid, out_sig);
}
 
/* Process an licence issue packet */
static void
licence_process_issue(RDPCLIENT * This, STREAM s)
{
    RC4_KEY crypt_key;
    uint32 length;
    uint16 check;
    int i;
 
    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, This->licence.key);
    RC4(&crypt_key, length, s->p, s->p);
 
    in_uint16(s, check);
    if (check != 0)
        return;
 
    This->licence_issued = True;
 
    in_uint8s(s, 2);    /* pad */
 
    /* advance to fourth string */
    length = 0;
    for (i = 0; i < 4; i++)
    {
        in_uint8s(s, length);
        in_uint32_le(s, length);
        if (!s_check_rem(s, length))
            return;
    }
 
    This->licence_issued = True;
    save_licence(This, s->p, length);
}
 
/* Process a licence packet */
void
licence_process(RDPCLIENT * This, STREAM s)
{
    uint8 tag;
 
    in_uint8(s, tag);
    in_uint8s(s, 3);    /* version, length */
 
    switch (tag)
    {
        case LICENCE_TAG_DEMAND:
            licence_process_demand(This, s);
            break;
 
        case LICENCE_TAG_AUTHREQ:
            licence_process_authreq(This, s);
            break;
 
        case LICENCE_TAG_ISSUE:
            licence_process_issue(This, s);
            break;
 
        case LICENCE_TAG_REISSUE:
        case LICENCE_TAG_RESULT:
            break;
 
        default:
            unimpl("licence tag 0x%x\n", tag);
    }
}