trunk/rdesktop/secure.c

/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   Protocol services - RDP encryption and licensing
   Copyright (C) Matthew Chapman 1999-2007

   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"
#include "ssl.h"

extern char g_hostname[16];
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 RD_BOOL g_encryption;
extern RD_BOOL g_licence_issued;
extern RD_BOOL g_use_rdp5;
extern RD_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 SSL_RC4 rc4_decrypt_key;
static SSL_RC4 rc4_encrypt_key;
static uint32 server_public_key_len;

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_MAX_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];
        SSL_SHA1 sha1;
        SSL_MD5 md5;
        int i;

        for (i = 0; i < 3; i++)
        {
                memset(pad, salt + i, i + 1);

                ssl_sha1_init(&sha1);
                ssl_sha1_update(&sha1, pad, i + 1);
                ssl_sha1_update(&sha1, in, 48);
                ssl_sha1_update(&sha1, salt1, 32);
                ssl_sha1_update(&sha1, salt2, 32);
                ssl_sha1_final(&sha1, shasig);

                ssl_md5_init(&md5);
                ssl_md5_update(&md5, in, 48);
                ssl_md5_update(&md5, shasig, 20);
                ssl_md5_final(&md5, &out[i * 16]);
        }
}

/*
 * 16-byte transformation used to generate export keys (6.2.2).
 */
void
sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2)
{
        SSL_MD5 md5;

        ssl_md5_init(&md5);
        ssl_md5_update(&md5, in, 16);
        ssl_md5_update(&md5, salt1, 32);
        ssl_md5_update(&md5, salt2, 32);
        ssl_md5_final(&md5, out);
}

/* 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_set_key(&rc4_decrypt_key, sec_decrypt_key, rc4_key_len);
        ssl_rc4_set_key(&rc4_encrypt_key, 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];
        SSL_SHA1 sha1;
        SSL_MD5 md5;

        buf_out_uint32(lenhdr, datalen);

        ssl_sha1_init(&sha1);
        ssl_sha1_update(&sha1, session_key, keylen);
        ssl_sha1_update(&sha1, pad_54, 40);
        ssl_sha1_update(&sha1, lenhdr, 4);
        ssl_sha1_update(&sha1, data, datalen);
        ssl_sha1_final(&sha1, shasig);

        ssl_md5_init(&md5);
        ssl_md5_update(&md5, session_key, keylen);
        ssl_md5_update(&md5, pad_92, 48);
        ssl_md5_update(&md5, shasig, 20);
        ssl_md5_final(&md5, md5sig);

        memcpy(signature, md5sig, siglen);
}

/* Update an encryption key */
static void
sec_update(uint8 * key, uint8 * update_key)
{
        uint8 shasig[20];
        SSL_SHA1 sha1;
        SSL_MD5 md5;
        SSL_RC4 update;

        ssl_sha1_init(&sha1);
        ssl_sha1_update(&sha1, update_key, rc4_key_len);
        ssl_sha1_update(&sha1, pad_54, 40);
        ssl_sha1_update(&sha1, key, rc4_key_len);
        ssl_sha1_final(&sha1, shasig);

        ssl_md5_init(&md5);
        ssl_md5_update(&md5, update_key, rc4_key_len);
        ssl_md5_update(&md5, pad_92, 48);
        ssl_md5_update(&md5, shasig, 20);
        ssl_md5_final(&md5, key);

        ssl_rc4_set_key(&update, key, rc4_key_len);
        ssl_rc4_crypt(&update, key, key, rc4_key_len);

        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, sec_encrypt_key, rc4_key_len);
                sec_encrypt_use_count = 0;
        }

        ssl_rc4_crypt(&rc4_encrypt_key, data, 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, sec_decrypt_key, rc4_key_len);
                sec_decrypt_use_count = 0;
        }

        ssl_rc4_crypt(&rc4_decrypt_key, data, data, length);
        sec_decrypt_use_count++;
}

/* Perform an RSA public key encryption operation */
static void
sec_rsa_encrypt(uint8 * out, uint8 * in, int len, uint32 modulus_size, uint8 * modulus,
                uint8 * exponent)
{
        ssl_rsa_encrypt(out, in, len, modulus_size, modulus, exponent);
}

/* 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;

#ifdef WITH_SCARD
        scard_lock(SCARD_LOCK_SEC);
#endif

        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;

#if 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);

#ifdef WITH_SCARD
        scard_unlock(SCARD_LOCK_SEC);
#endif
}

/* 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 = server_public_key_len + SEC_PADDING_SIZE;
        uint32 flags = SEC_CLIENT_RANDOM;
        STREAM s;

        s = sec_init(flags, length + 4);

        out_uint32_le(s, length);
        out_uint8p(s, sec_crypted_random, server_public_key_len);
        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 RD_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);
        modulus_len -= SEC_PADDING_SIZE;
        if ((modulus_len < SEC_MODULUS_SIZE) || (modulus_len > SEC_MAX_MODULUS_SIZE))
        {
                error("Bad server public key size (%u bits)\n", modulus_len * 8);
                return False;
        }

        in_uint8s(s, 8);        /* modulus_bits, unknown */
        in_uint8a(s, exponent, SEC_EXPONENT_SIZE);
        in_uint8a(s, modulus, modulus_len);
        in_uint8s(s, SEC_PADDING_SIZE);
        server_public_key_len = modulus_len;

        return s_check(s);
}

/* Parse a public signature structure */
static RD_BOOL
sec_parse_public_sig(STREAM s, uint32 len, uint8 * modulus, uint8 * exponent)
{
        uint8 signature[SEC_MAX_MODULUS_SIZE];
        uint32 sig_len;

        if (len != 72)
        {
                return True;
        }
        memset(signature, 0, sizeof(signature));
        sig_len = len - 8;
        in_uint8a(s, signature, sig_len);
        return ssl_sig_ok(exponent, SEC_EXPONENT_SIZE, modulus, server_public_key_len,
                          signature, sig_len);
}

/* Parse a crypto information structure */
static RD_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;
        SSL_CERT *cacert, *server_cert;
        SSL_RKEY *server_public_key;
        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:
                                        if (!sec_parse_public_sig(s, length, modulus, exponent))
                                                return False;
                                        break;

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

                        s->p = next_tag;
                }
        }
        else
        {
                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;
                        SSL_CERT *ignorecert;

                        DEBUG_RDP5(("Ignored certs left: %d\n", certcount));
                        in_uint32_le(s, ignorelen);
                        DEBUG_RDP5(("Ignored Certificate length is %d\n", ignorelen));
                        ignorecert = ssl_cert_read(s->p, ignorelen);
                        in_uint8s(s, 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));
                        ssl_cert_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 = ssl_cert_read(s->p, cacert_len);
                in_uint8s(s, cacert_len);
                if (NULL == cacert)
                {
                        error("Couldn't load CA Certificate from server\n");
                        return False;
                }
                in_uint32_le(s, cert_len);
                DEBUG_RDP5(("Certificate length is %d\n", cert_len));
                server_cert = ssl_cert_read(s->p, cert_len);
                in_uint8s(s, cert_len);
                if (NULL == server_cert)
                {
                        ssl_cert_free(cacert);
                        error("Couldn't load Certificate from server\n");
                        return False;
                }
                if (!ssl_certs_ok(server_cert, cacert))
                {
                        ssl_cert_free(server_cert);
                        ssl_cert_free(cacert);
                        error("Security error CA Certificate invalid\n");
                        return False;
                }
                ssl_cert_free(cacert);
                in_uint8s(s, 16);       /* Padding */
                server_public_key = ssl_cert_to_rkey(server_cert, &server_public_key_len);
                if (NULL == server_public_key)
                {
                        DEBUG_RDP5(("Didn't parse X509 correctly\n"));
                        ssl_cert_free(server_cert);
                        return False;
                }
                ssl_cert_free(server_cert);
                if ((server_public_key_len < SEC_MODULUS_SIZE) ||
                    (server_public_key_len > SEC_MAX_MODULUS_SIZE))
                {
                        error("Bad server public key size (%u bits)\n", server_public_key_len * 8);
                        ssl_rkey_free(server_public_key);
                        return False;
                }
                if (ssl_rkey_get_exp_mod(server_public_key, exponent, SEC_EXPONENT_SIZE,
                                         modulus, SEC_MAX_MODULUS_SIZE) != 0)
                {
                        error("Problem extracting RSA exponent, modulus");
                        ssl_rkey_free(server_public_key);
                        return False;
                }
                ssl_rkey_free(server_public_key);
                return True;    /* There's some garbage here we don't care about */
        }
        return s_check_end(s);
}

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

        memset(modulus, 0, sizeof(modulus));
        memset(exponent, 0, sizeof(exponent));
        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_random(client_random);
        sec_rsa_encrypt(sec_crypted_random, client_random, SEC_RANDOM_SIZE,
                        server_public_key_len, 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 */
RD_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 */
RD_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();
}