secure.c

Go to the documentation of this file.

/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   Protocol services - RDP encryption and licensing
   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 <precomp.h>

//#include <openssl/rc4.h>
//#include <openssl/md5.h>
//#include <openssl/sha.h>
//#include <openssl/bn.h>
//#include <openssl/x509v3.h>

void *
ssl_sha1_info_create(void);
void
ssl_sha1_info_delete(void * sha1_info);
void
ssl_sha1_clear(void * sha1_info);
void
ssl_sha1_transform(void * sha1_info, char * data, int len);
void
ssl_sha1_complete(void * sha1_info, char * data);
void *
ssl_md5_info_create(void);
void
ssl_md5_info_delete(void * md5_info);
void *
ssl_md5_info_create(void);
void
ssl_md5_info_delete(void * md5_info);
void
ssl_md5_clear(void * md5_info);
void
ssl_md5_transform(void * md5_info, char * data, int len);
void
ssl_md5_complete(void * md5_info, char * data);
void *
ssl_rc4_info_create(void);
void
ssl_rc4_info_delete(void * rc4_info);
void
ssl_rc4_set_key(void * rc4_info, char * key, int len);
void
ssl_rc4_crypt(void * rc4_info, char * in_data, char * out_data, int len);
int
ssl_mod_exp(char* out, int out_len, char* in, int in_len,
            char* mod, int mod_len, char* exp, int exp_len);

extern char g_hostname[];
extern int g_width;
extern int g_height;
extern unsigned int g_keylayout;
extern int g_keyboard_type;
extern int g_keyboard_subtype;
extern int g_keyboard_functionkeys;
extern BOOL g_encryption;
extern BOOL g_licence_issued;
extern BOOL g_use_rdp5;
extern BOOL g_console_session;
extern int g_server_depth;
extern uint16 mcs_userid;
extern VCHANNEL g_channels[];
extern unsigned int g_num_channels;

static int rc4_key_len;
static void * rc4_decrypt_key = 0;
static void * rc4_encrypt_key = 0;
//static RSA *server_public_key;
static void * server_public_key;

static uint8 sec_sign_key[16];
static uint8 sec_decrypt_key[16];
static uint8 sec_encrypt_key[16];
static uint8 sec_decrypt_update_key[16];
static uint8 sec_encrypt_update_key[16];
static uint8 sec_crypted_random[SEC_MODULUS_SIZE];

uint16 g_server_rdp_version = 0;

/* These values must be available to reset state - Session Directory */
static int sec_encrypt_use_count = 0;
static int sec_decrypt_use_count = 0;

/*
 * I believe this is based on SSLv3 with the following differences:
 *  MAC algorithm (5.2.3.1) uses only 32-bit length in place of seq_num/type/length fields
 *  MAC algorithm uses SHA1 and MD5 for the two hash functions instead of one or other
 *  key_block algorithm (6.2.2) uses 'X', 'YY', 'ZZZ' instead of 'A', 'BB', 'CCC'
 *  key_block partitioning is different (16 bytes each: MAC secret, decrypt key, encrypt key)
 *  encryption/decryption keys updated every 4096 packets
 * See http://wp.netscape.com/eng/ssl3/draft302.txt
 */

/*
 * 48-byte transformation used to generate master secret (6.1) and key material (6.2.2).
 * Both SHA1 and MD5 algorithms are used.
 */
void
sec_hash_48(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2, uint8 salt)
{
    uint8 shasig[20];
    uint8 pad[4];
    void * sha;
    void * md5;
    int i;

    for (i = 0; i < 3; i++)
    {
        memset(pad, salt + i, i + 1);
        sha = ssl_sha1_info_create();
        ssl_sha1_clear(sha);
        ssl_sha1_transform(sha, (char *)pad, i + 1);
        ssl_sha1_transform(sha, (char *)in, 48);
        ssl_sha1_transform(sha, (char *)salt1, 32);
        ssl_sha1_transform(sha, (char *)salt2, 32);
        ssl_sha1_complete(sha, (char *)shasig);
        ssl_sha1_info_delete(sha);
        md5 = ssl_md5_info_create();
        ssl_md5_clear(md5);
        ssl_md5_transform(md5, (char *)in, 48);
        ssl_md5_transform(md5, (char *)shasig, 20);
        ssl_md5_complete(md5, (char *)out + i * 16);
        ssl_md5_info_delete(md5);
    }
}

/*
 * 16-byte transformation used to generate export keys (6.2.2).
 */
void
sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2)
{
    void * md5;
    
    md5 = ssl_md5_info_create();
    ssl_md5_clear(md5);
    ssl_md5_transform(md5, (char *)in, 16);
    ssl_md5_transform(md5, (char *)salt1, 32);
    ssl_md5_transform(md5, (char *)salt2, 32);
    ssl_md5_complete(md5, (char *)out);
    ssl_md5_info_delete(md5);
}

/* Reduce key entropy from 64 to 40 bits */
static void
sec_make_40bit(uint8 * key)
{
    key[0] = 0xd1;
    key[1] = 0x26;
    key[2] = 0x9e;
}

/* Generate encryption keys given client and server randoms */
static void
sec_generate_keys(uint8 * client_random, uint8 * server_random, int rc4_key_size)
{
    uint8 pre_master_secret[48];
    uint8 master_secret[48];
    uint8 key_block[48];

    /* Construct pre-master secret */
    memcpy(pre_master_secret, client_random, 24);
    memcpy(pre_master_secret + 24, server_random, 24);

    /* 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, client_random, server_random, 'X');

    /* First 16 bytes of key material is MAC secret */
    memcpy(sec_sign_key, key_block, 16);

    /* Generate export keys from next two blocks of 16 bytes */
    sec_hash_16(sec_decrypt_key, &key_block[16], client_random, server_random);
    sec_hash_16(sec_encrypt_key, &key_block[32], client_random, server_random);

    if (rc4_key_size == 1)
    {
        DEBUG(("40-bit encryption enabled\n"));
        sec_make_40bit(sec_sign_key);
        sec_make_40bit(sec_decrypt_key);
        sec_make_40bit(sec_encrypt_key);
        rc4_key_len = 8;
    }
    else
    {
        DEBUG(("rc_4_key_size == %d, 128-bit encryption enabled\n", rc4_key_size));
        rc4_key_len = 16;
    }

    /* Save initial RC4 keys as update keys */
    memcpy(sec_decrypt_update_key, sec_decrypt_key, 16);
    memcpy(sec_encrypt_update_key, sec_encrypt_key, 16);

    /* Initialise RC4 state arrays */

    ssl_rc4_info_delete(rc4_decrypt_key);
    rc4_decrypt_key = ssl_rc4_info_create(); 
    ssl_rc4_set_key(rc4_decrypt_key, (char *)sec_decrypt_key, rc4_key_len); 

    ssl_rc4_info_delete(rc4_encrypt_key);
    rc4_encrypt_key = ssl_rc4_info_create(); 
    ssl_rc4_set_key(rc4_encrypt_key, (char *)sec_encrypt_key, rc4_key_len); 
}

static uint8 pad_54[40] = {
    54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
    54, 54, 54,
    54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
    54, 54, 54
};

static uint8 pad_92[48] = {
    92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
    92, 92, 92, 92, 92, 92, 92,
    92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
    92, 92, 92, 92, 92, 92, 92
};

/* Output a uint32 into a buffer (little-endian) */
void
buf_out_uint32(uint8 * buffer, uint32 value)
{
    buffer[0] = (value) & 0xff;
    buffer[1] = (value >> 8) & 0xff;
    buffer[2] = (value >> 16) & 0xff;
    buffer[3] = (value >> 24) & 0xff;
}

/* Generate a MAC hash (5.2.3.1), using a combination of SHA1 and MD5 */
void
sec_sign(uint8 * signature, int siglen, uint8 * session_key, int keylen, uint8 * data, int datalen)
{
    uint8 shasig[20];
    uint8 md5sig[16];
    uint8 lenhdr[4];
    void * sha;
    void * md5;

    buf_out_uint32(lenhdr, datalen);

    sha = ssl_sha1_info_create();
    ssl_sha1_clear(sha);
    ssl_sha1_transform(sha, (char *)session_key, keylen);
    ssl_sha1_transform(sha, (char *)pad_54, 40);
    ssl_sha1_transform(sha, (char *)lenhdr, 4);
    ssl_sha1_transform(sha, (char *)data, datalen);
    ssl_sha1_complete(sha, (char *)shasig);
    ssl_sha1_info_delete(sha);

    md5 = ssl_md5_info_create();
    ssl_md5_clear(md5);
    ssl_md5_transform(md5, (char *)session_key, keylen);
    ssl_md5_transform(md5, (char *)pad_92, 48);
    ssl_md5_transform(md5, (char *)shasig, 20);
    ssl_md5_complete(md5, (char *)md5sig);
    ssl_md5_info_delete(md5);

    memcpy(signature, md5sig, siglen);
}

/* Update an encryption key */
static void
sec_update(uint8 * key, uint8 * update_key)
{
    uint8 shasig[20];
    void * sha;
    void * md5;
    void * update;

    sha = ssl_sha1_info_create();
    ssl_sha1_clear(sha);
    ssl_sha1_transform(sha, (char *)update_key, rc4_key_len);
    ssl_sha1_transform(sha, (char *)pad_54, 40);
    ssl_sha1_transform(sha, (char *)key, rc4_key_len);
    ssl_sha1_complete(sha, (char *)shasig);
    ssl_sha1_info_delete(sha);

    md5 = ssl_md5_info_create();
    ssl_md5_clear(md5);
    ssl_md5_transform(md5, (char *)update_key, rc4_key_len);
    ssl_md5_transform(md5, (char *)pad_92, 48);
    ssl_md5_transform(md5, (char *)shasig, 20);
    ssl_md5_complete(md5, (char *)key);
    ssl_md5_info_delete(md5);


    update = ssl_rc4_info_create();
    ssl_rc4_set_key(update, (char *)key, rc4_key_len);
    ssl_rc4_crypt(update, (char *)key, (char *)key, rc4_key_len);
    ssl_rc4_info_delete(update);
    
    if (rc4_key_len == 8)
        sec_make_40bit(key);
}

/* Encrypt data using RC4 */
static void
sec_encrypt(uint8 * data, int length)
{
    if (sec_encrypt_use_count == 4096)
    {
        sec_update(sec_encrypt_key, sec_encrypt_update_key);
        ssl_rc4_set_key(rc4_encrypt_key, (char *)sec_encrypt_key, rc4_key_len);
        sec_encrypt_use_count = 0;
    }
    ssl_rc4_crypt(rc4_encrypt_key, (char *)data, (char *)data, length);
    sec_encrypt_use_count++;
}

/* Decrypt data using RC4 */
void
sec_decrypt(uint8 * data, int length)
{
    if (sec_decrypt_use_count == 4096)
    {
        sec_update(sec_decrypt_key, sec_decrypt_update_key);
        ssl_rc4_set_key(rc4_decrypt_key, (char *)sec_decrypt_key, rc4_key_len);
        sec_decrypt_use_count = 0;
    }
    ssl_rc4_crypt(rc4_decrypt_key, (char *)data, (char *)data, length);
    sec_decrypt_use_count++;
}

/*static void
reverse(uint8 * p, int len)
{
    int i, j;
    uint8 temp;

    for (i = 0, j = len - 1; i < j; i++, j--)
    {
        temp = p[i];
        p[i] = p[j];
        p[j] = temp;
    }
}*/

/* Perform an RSA public key encryption operation */
static void
sec_rsa_encrypt(uint8 * out, uint8 * in, int len, uint8 * modulus, uint8 * exponent)
{
    ssl_mod_exp((char *)out, 64, (char *)in, 32, (char *)modulus, 64, (char *)exponent, 4);
/*
    BN_CTX *ctx;
    BIGNUM mod, exp, x, y;
    uint8 inr[SEC_MODULUS_SIZE];
    int outlen;

    reverse(modulus, SEC_MODULUS_SIZE);
    reverse(exponent, SEC_EXPONENT_SIZE);
    memcpy(inr, in, len);
    reverse(inr, len);

    ctx = BN_CTX_new();
    BN_init(&mod);
    BN_init(&exp);
    BN_init(&x);
    BN_init(&y);

    BN_bin2bn(modulus, SEC_MODULUS_SIZE, &mod);
    BN_bin2bn(exponent, SEC_EXPONENT_SIZE, &exp);
    BN_bin2bn(inr, len, &x);
    BN_mod_exp(&y, &x, &exp, &mod, ctx);
    outlen = BN_bn2bin(&y, out);
    reverse(out, outlen);
    if (outlen < SEC_MODULUS_SIZE)
        memset(out + outlen, 0, SEC_MODULUS_SIZE - outlen);

    BN_free(&y);
    BN_clear_free(&x);
    BN_free(&exp);
    BN_free(&mod);
    BN_CTX_free(ctx);*/
}

/* Initialise secure transport packet */
STREAM
sec_init(uint32 flags, int maxlen)
{
    int hdrlen;
    STREAM s;

    if (!g_licence_issued)
        hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4;
    else
        hdrlen = (flags & SEC_ENCRYPT) ? 12 : 0;
    s = mcs_init(maxlen + hdrlen);
    s_push_layer(s, sec_hdr, hdrlen);

    return s;
}

/* Transmit secure transport packet over specified channel */
void
sec_send_to_channel(STREAM s, uint32 flags, uint16 channel)
{
    int datalen;

    s_pop_layer(s, sec_hdr);
    if (!g_licence_issued || (flags & SEC_ENCRYPT))
        out_uint32_le(s, flags);

    if (flags & SEC_ENCRYPT)
    {
        flags &= ~SEC_ENCRYPT;
        datalen = s->end - s->p - 8;

#ifdef WITH_DEBUG
        DEBUG(("Sending encrypted packet:\n"));
        hexdump(s->p + 8, datalen);
#endif

        sec_sign(s->p, 8, sec_sign_key, rc4_key_len, s->p + 8, datalen);
        sec_encrypt(s->p + 8, datalen);
    }

    mcs_send_to_channel(s, channel);
}

/* Transmit secure transport packet */

void
sec_send(STREAM s, uint32 flags)
{
    sec_send_to_channel(s, flags, MCS_GLOBAL_CHANNEL);
}


/* Transfer the client random to the server */
static void
sec_establish_key(void)
{
    uint32 length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE;
    uint32 flags = SEC_CLIENT_RANDOM;
    STREAM s;

    s = sec_init(flags, 76);

    out_uint32_le(s, length);
    out_uint8p(s, sec_crypted_random, SEC_MODULUS_SIZE);
    out_uint8s(s, SEC_PADDING_SIZE);

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

/* Output connect initial data blob */
static void
sec_out_mcs_data(STREAM s)
{
    int hostlen = 2 * strlen(g_hostname);
    int length = 158 + 76 + 12 + 4;
    unsigned int i;

    if (g_num_channels > 0)
        length += g_num_channels * 12 + 8;

    if (hostlen > 30)
        hostlen = 30;

    /* Generic Conference Control (T.124) ConferenceCreateRequest */
    out_uint16_be(s, 5);
    out_uint16_be(s, 0x14);
    out_uint8(s, 0x7c);
    out_uint16_be(s, 1);

    out_uint16_be(s, (length | 0x8000));    /* remaining length */

    out_uint16_be(s, 8);    /* length? */
    out_uint16_be(s, 16);
    out_uint8(s, 0);
    out_uint16_le(s, 0xc001);
    out_uint8(s, 0);

    out_uint32_le(s, 0x61637544);   /* OEM ID: "Duca", as in Ducati. */
    out_uint16_be(s, ((length - 14) | 0x8000)); /* remaining length */

    /* Client information */
    out_uint16_le(s, SEC_TAG_CLI_INFO);
    out_uint16_le(s, 212);  /* length */
    out_uint16_le(s, g_use_rdp5 ? 4 : 1);   /* RDP version. 1 == RDP4, 4 == RDP5. */
    out_uint16_le(s, 8);
    out_uint16_le(s, g_width);
    out_uint16_le(s, g_height);
    out_uint16_le(s, 0xca01);
    out_uint16_le(s, 0xaa03);
    out_uint32_le(s, g_keylayout);
    out_uint32_le(s, 2600); /* Client build. We are now 2600 compatible :-) */

    /* Unicode name of client, padded to 32 bytes */
    rdp_out_unistr(s, g_hostname, hostlen);
    out_uint8s(s, 30 - hostlen);

    /* See
       http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wceddk40/html/cxtsksupportingremotedesktopprotocol.asp */
    out_uint32_le(s, g_keyboard_type);
    out_uint32_le(s, g_keyboard_subtype);
    out_uint32_le(s, g_keyboard_functionkeys);
    out_uint8s(s, 64);  /* reserved? 4 + 12 doublewords */
    out_uint16_le(s, 0xca01);   /* colour depth? */
    out_uint16_le(s, 1);

    out_uint32(s, 0);
    out_uint8(s, g_server_depth);
    out_uint16_le(s, 0x0700);
    out_uint8(s, 0);
    out_uint32_le(s, 1);
    out_uint8s(s, 64);  /* End of client info */

    out_uint16_le(s, SEC_TAG_CLI_4);
    out_uint16_le(s, 12);
    out_uint32_le(s, g_console_session ? 0xb : 9);
    out_uint32(s, 0);

    /* Client encryption settings */
    out_uint16_le(s, SEC_TAG_CLI_CRYPT);
    out_uint16_le(s, 12);   /* length */
    out_uint32_le(s, g_encryption ? 0x3 : 0);   /* encryption supported, 128-bit supported */
    out_uint32(s, 0);   /* Unknown */

    DEBUG_RDP5(("g_num_channels is %d\n", g_num_channels));
    if (g_num_channels > 0)
    {
        out_uint16_le(s, SEC_TAG_CLI_CHANNELS);
        out_uint16_le(s, g_num_channels * 12 + 8);  /* length */
        out_uint32_le(s, g_num_channels);   /* number of virtual channels */
        for (i = 0; i < g_num_channels; i++)
        {
            DEBUG_RDP5(("Requesting channel %s\n", g_channels[i].name));
            out_uint8a(s, g_channels[i].name, 8);
            out_uint32_be(s, g_channels[i].flags);
        }
    }

    s_mark_end(s);
}

/* Parse a public key structure */
static BOOL
sec_parse_public_key(STREAM s, uint8 ** modulus, uint8 ** exponent)
{
    uint32 magic, modulus_len;

    in_uint32_le(s, magic);
    if (magic != SEC_RSA_MAGIC)
    {
        error("RSA magic 0x%x\n", magic);
        return False;
    }

    in_uint32_le(s, modulus_len);
    if (modulus_len != SEC_MODULUS_SIZE + SEC_PADDING_SIZE)
    {
        error("modulus len 0x%x\n", modulus_len);
        return False;
    }

    in_uint8s(s, 8);    /* modulus_bits, unknown */
    in_uint8p(s, *exponent, SEC_EXPONENT_SIZE);
    in_uint8p(s, *modulus, SEC_MODULUS_SIZE);
    in_uint8s(s, SEC_PADDING_SIZE);

    return s_check(s);
}

/* Parse a crypto information structure */
static BOOL
sec_parse_crypt_info(STREAM s, uint32 * rc4_key_size,
             uint8 ** server_random, uint8 ** modulus, uint8 ** exponent)
{
    uint32 crypt_level, random_len, rsa_info_len;
    uint32 /*cacert_len, cert_len,*/ flags;
    //X509 *cacert, *server_cert;
    uint16 tag, length;
    uint8 *next_tag, *end;

    in_uint32_le(s, *rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */
    in_uint32_le(s, crypt_level);   /* 1 = low, 2 = medium, 3 = high */
    if (crypt_level == 0)   /* no encryption */
        return False;
    in_uint32_le(s, random_len);
    in_uint32_le(s, rsa_info_len);

    if (random_len != SEC_RANDOM_SIZE)
    {
        error("random len %d, expected %d\n", random_len, SEC_RANDOM_SIZE);
        return False;
    }

    in_uint8p(s, *server_random, random_len);

    /* RSA info */
    end = s->p + rsa_info_len;
    if (end > s->end)
        return False;

    in_uint32_le(s, flags); /* 1 = RDP4-style, 0x80000002 = X.509 */
    if (flags & 1)
    {
        DEBUG_RDP5(("We're going for the RDP4-style encryption\n"));
        in_uint8s(s, 8);    /* unknown */

        while (s->p < end)
        {
            in_uint16_le(s, tag);
            in_uint16_le(s, length);

            next_tag = s->p + length;

            switch (tag)
            {
                case SEC_TAG_PUBKEY:
                    if (!sec_parse_public_key(s, modulus, exponent))
                        return False;
                    DEBUG_RDP5(("Got Public key, RDP4-style\n"));

                    break;

                case SEC_TAG_KEYSIG:
                    /* Is this a Microsoft key that we just got? */
                    /* Care factor: zero! */
                    /* Actually, it would probably be a good idea to check if the public key is signed with this key, and then store this 
                       key as a known key of the hostname. This would prevent some MITM-attacks. */
                    break;

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

            s->p = next_tag;
        }
    }
    else
    { 
#if 0
        uint32 certcount;

        DEBUG_RDP5(("We're going for the RDP5-style encryption\n"));
        in_uint32_le(s, certcount); /* Number of certificates */

        if (certcount < 2)
        {
            error("Server didn't send enough X509 certificates\n");
            return False;
        }

        for (; certcount > 2; certcount--)
        {       /* ignore all the certificates between the root and the signing CA */
            uint32 ignorelen;
            X509 *ignorecert;

            DEBUG_RDP5(("Ignored certs left: %d\n", certcount));

            in_uint32_le(s, ignorelen);
            DEBUG_RDP5(("Ignored Certificate length is %d\n", ignorelen));
            ignorecert = d2i_X509(NULL, &(s->p), ignorelen);

            if (ignorecert == NULL)
            {   /* XXX: error out? */
                DEBUG_RDP5(("got a bad cert: this will probably screw up the rest of the communication\n"));
            }

#ifdef WITH_DEBUG_RDP5
            DEBUG_RDP5(("cert #%d (ignored):\n", certcount));
            X509_print_fp(stdout, ignorecert);
#endif
        }

        /* Do da funky X.509 stuffy 

           "How did I find out about this?  I looked up and saw a
           bright light and when I came to I had a scar on my forehead
           and knew about X.500"
           - Peter Gutman in a early version of 
           http://www.cs.auckland.ac.nz/~pgut001/pubs/x509guide.txt
         */

        in_uint32_le(s, cacert_len);
        DEBUG_RDP5(("CA Certificate length is %d\n", cacert_len));
        cacert = d2i_X509(NULL, &(s->p), cacert_len);
        /* Note: We don't need to move s->p here - d2i_X509 is
           "kind" enough to do it for us */
        if (NULL == cacert)
        {
            error("Couldn't load CA Certificate from server\n");
            return False;
        }

        /* Currently, we don't use the CA Certificate. 
           FIXME: 
           *) Verify the server certificate (server_cert) with the 
           CA certificate.
           *) Store the CA Certificate with the hostname of the 
           server we are connecting to as key, and compare it
           when we connect the next time, in order to prevent
           MITM-attacks.
         */

        X509_free(cacert);

        in_uint32_le(s, cert_len);
        DEBUG_RDP5(("Certificate length is %d\n", cert_len));
        server_cert = d2i_X509(NULL, &(s->p), cert_len);
        if (NULL == server_cert)
        {
            error("Couldn't load Certificate from server\n");
            return False;
        }

        in_uint8s(s, 16);   /* Padding */

        /* Note: Verifying the server certificate must be done here, 
           before sec_parse_public_key since we'll have to apply
           serious violence to the key after this */

        if (!sec_parse_x509_key(server_cert))
        {
            DEBUG_RDP5(("Didn't parse X509 correctly\n"));
            X509_free(server_cert);
            return False;
        }
        X509_free(server_cert);
        return True;    /* There's some garbage here we don't care about */
#endif
    }
    return s_check_end(s);
}

/* Process crypto information blob */
static void
sec_process_crypt_info(STREAM s)
{
    uint8 *server_random, *modulus = NULL, *exponent = NULL;
    uint8 client_random[SEC_RANDOM_SIZE];
    uint32 rc4_key_size;
    uint8 inr[SEC_MODULUS_SIZE];

    if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random, &modulus, &exponent))
    {
        DEBUG(("Failed to parse crypt info\n"));
        return;
    }

    DEBUG(("Generating client random\n"));
    /* Generate a client random, and hence determine encryption keys */
    /* This is what the MS client do: */
    memset(inr, 0, SEC_RANDOM_SIZE);
    /*  *ARIGL!* Plaintext attack, anyone?
       I tried doing:
       generate_random(inr);
       ..but that generates connection errors now and then (yes, 
       "now and then". Something like 0 to 3 attempts needed before a 
       successful connection. Nice. Not! 
     */

    generate_random(client_random);
    if (NULL != server_public_key)
    {           /* Which means we should use 
                   RDP5-style encryption */
#if 0
        memcpy(inr + SEC_RANDOM_SIZE, client_random, SEC_RANDOM_SIZE);
        reverse(inr + SEC_RANDOM_SIZE, SEC_RANDOM_SIZE);

        RSA_public_encrypt(SEC_MODULUS_SIZE,
                   inr, sec_crypted_random, server_public_key, RSA_NO_PADDING);

        reverse(sec_crypted_random, SEC_MODULUS_SIZE);

        RSA_free(server_public_key);
        server_public_key = NULL;
#endif
    }
    else
    {           /* RDP4-style encryption */
        sec_rsa_encrypt(sec_crypted_random,
                client_random, SEC_RANDOM_SIZE, modulus, exponent);
    }
    sec_generate_keys(client_random, server_random, rc4_key_size);
}


/* Process SRV_INFO, find RDP version supported by server */
static void
sec_process_srv_info(STREAM s)
{
    in_uint16_le(s, g_server_rdp_version);
    DEBUG_RDP5(("Server RDP version is %d\n", g_server_rdp_version));
    if (1 == g_server_rdp_version)
    {
        g_use_rdp5 = 0;
        g_server_depth = 8;
    }
}


/* Process connect response data blob */
void
sec_process_mcs_data(STREAM s)
{
    uint16 tag, length;
    uint8 *next_tag;
    uint8 len;

    in_uint8s(s, 21);   /* header (T.124 ConferenceCreateResponse) */
    in_uint8(s, len);
    if (len & 0x80)
        in_uint8(s, len);

    while (s->p < s->end)
    {
        in_uint16_le(s, tag);
        in_uint16_le(s, length);

        if (length <= 4)
            return;

        next_tag = s->p + length - 4;

        switch (tag)
        {
            case SEC_TAG_SRV_INFO:
                sec_process_srv_info(s);
                break;

            case SEC_TAG_SRV_CRYPT:
                sec_process_crypt_info(s);
                break;

            case SEC_TAG_SRV_CHANNELS:
                /* FIXME: We should parse this information and
                   use it to map RDP5 channels to MCS 
                   channels */
                break;

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

        s->p = next_tag;
    }
}

/* Receive secure transport packet */
STREAM
sec_recv(uint8 * rdpver)
{
    uint32 sec_flags;
    uint16 channel;
    STREAM s;

    while ((s = mcs_recv(&channel, rdpver)) != NULL)
    {
        if (rdpver != NULL)
        {
            if (*rdpver != 3)
            {
                if (*rdpver & 0x80)
                {
                    in_uint8s(s, 8);    /* signature */
                    sec_decrypt(s->p, s->end - s->p);
                }
                return s;
            }
        }
        if (g_encryption || !g_licence_issued)
        {
            in_uint32_le(s, sec_flags);

            if (sec_flags & SEC_ENCRYPT)
            {
                in_uint8s(s, 8);    /* signature */
                sec_decrypt(s->p, s->end - s->p);
            }

            if (sec_flags & SEC_LICENCE_NEG)
            {
                licence_process(s);
                continue;
            }

            if (sec_flags & 0x0400) /* SEC_REDIRECT_ENCRYPT */
            {
                uint8 swapbyte;

                in_uint8s(s, 8);    /* signature */
                sec_decrypt(s->p, s->end - s->p);

                /* Check for a redirect packet, starts with 00 04 */
                if (s->p[0] == 0 && s->p[1] == 4)
                {
                    /* for some reason the PDU and the length seem to be swapped.
                       This isn't good, but we're going to do a byte for byte
                       swap.  So the first foure value appear as: 00 04 XX YY,
                       where XX YY is the little endian length. We're going to
                       use 04 00 as the PDU type, so after our swap this will look
                       like: XX YY 04 00 */
                    swapbyte = s->p[0];
                    s->p[0] = s->p[2];
                    s->p[2] = swapbyte;

                    swapbyte = s->p[1];
                    s->p[1] = s->p[3];
                    s->p[3] = swapbyte;

                    swapbyte = s->p[2];
                    s->p[2] = s->p[3];
                    s->p[3] = swapbyte;
                }
#ifdef WITH_DEBUG
                /* warning!  this debug statement will show passwords in the clear! */
                hexdump(s->p, s->end - s->p);
#endif
            }

        }

        if (channel != MCS_GLOBAL_CHANNEL)
        {
            channel_process(s, channel);
            *rdpver = 0xff;
            return s;
        }

        return s;
    }

    return NULL;
}

/* Establish a secure connection */
BOOL
sec_connect(char *server, char *username)
{
    struct stream mcs_data;

    /* We exchange some RDP data during the MCS-Connect */
    mcs_data.size = 512;
    mcs_data.p = mcs_data.data = (uint8 *) xmalloc(mcs_data.size);
    sec_out_mcs_data(&mcs_data);

    if (!mcs_connect(server, &mcs_data, username))
        return False;

    /*      sec_process_mcs_data(&mcs_data); */
    if (g_encryption)
        sec_establish_key();
    xfree(mcs_data.data);
    return True;
}

/* Establish a secure connection */
BOOL
sec_reconnect(char *server)
{
    struct stream mcs_data;

    /* We exchange some RDP data during the MCS-Connect */
    mcs_data.size = 512;
    mcs_data.p = mcs_data.data = (uint8 *) xmalloc(mcs_data.size);
    sec_out_mcs_data(&mcs_data);

    if (!mcs_reconnect(server, &mcs_data))
        return False;

    /*      sec_process_mcs_data(&mcs_data); */
    if (g_encryption)
        sec_establish_key();
    xfree(mcs_data.data);
    return True;
}

/* Disconnect a connection */
void
sec_disconnect(void)
{
    mcs_disconnect();
}

/* reset the state of the sec layer */
void
sec_reset_state(void)
{
    g_server_rdp_version = 0;
    sec_encrypt_use_count = 0;
    sec_decrypt_use_count = 0;
    mcs_reset_state();
}