xrdp/libxrdp/xrdp_iso.c

/**
 * xrdp: A Remote Desktop Protocol server.
 *
 * Copyright (C) Jay Sorg 2004-2014
 * Copyright (C) Idan Freiberg 2013-2014
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * iso layer
 */

#if defined(HAVE_CONFIG_H)
#include <config_ac.h>
#endif

#include "libxrdp.h"
#include "ms-rdpbcgr.h"
#include "log.h"

#define LOG_LEVEL 1
#define LLOG(_level, _args) \
    do { if (_level < LOG_LEVEL) { g_write _args ; } } while (0)
#define LLOGLN(_level, _args) \
    do { if (_level < LOG_LEVEL) { g_writeln _args ; } } while (0)
#define LHEXDUMP(_level, _args) \
    do { if (_level < LOG_LEVEL) { g_hexdump _args ; } } while (0)


/*****************************************************************************/
struct xrdp_iso *
xrdp_iso_create(struct xrdp_mcs *owner, struct trans *trans)
{
    struct xrdp_iso *self;

    LLOGLN(10, ("   in xrdp_iso_create"));
    self = (struct xrdp_iso *) g_malloc(sizeof(struct xrdp_iso), 1);
    self->mcs_layer = owner;
    self->trans = trans;
    LLOGLN(10, ("   out xrdp_iso_create"));
    return self;
}

/*****************************************************************************/
void
xrdp_iso_delete(struct xrdp_iso *self)
{
    if (self == 0)
    {
        return;
    }

    g_free(self);
}

/*****************************************************************************/
/* returns error */
static int
xrdp_iso_negotiate_security(struct xrdp_iso *self)
{
    int rv = 0;
    struct xrdp_client_info *client_info = &(self->mcs_layer->sec_layer->rdp_layer->client_info);

    self->selectedProtocol = client_info->security_layer;

    switch (client_info->security_layer)
    {
        case PROTOCOL_RDP:
            break;
        case PROTOCOL_SSL:
            if (self->requestedProtocol & PROTOCOL_SSL)
            {
                if (!g_file_readable(client_info->certificate) ||
                    !g_file_readable(client_info->key_file))
                {
                    /* certificate or privkey is not readable */
                    log_message(LOG_LEVEL_DEBUG, "No readable certificates or "
                                "private keys, cannot accept TLS connections");
                    self->failureCode = SSL_CERT_NOT_ON_SERVER;
                    rv = 1; /* error */
                }
                else
                {
                    self->selectedProtocol = PROTOCOL_SSL;
                }
            }
            else
            {
                self->failureCode = SSL_REQUIRED_BY_SERVER;
                rv = 1; /* error */
            }
            break;
        case PROTOCOL_HYBRID:
        case PROTOCOL_HYBRID_EX:
        default:
            if ((self->requestedProtocol & PROTOCOL_SSL) &&
                g_file_readable(client_info->certificate) &&
                g_file_readable(client_info->key_file))
            {
                /* that's a patch since we don't support CredSSP for now */
                self->selectedProtocol = PROTOCOL_SSL;
            }
            else
            {
                self->selectedProtocol = PROTOCOL_RDP;
            }
            break;
    }

    log_message(LOG_LEVEL_DEBUG, "Security layer: requested %d, selected %d",
                self->requestedProtocol, self->selectedProtocol);
    return rv;
}

/*****************************************************************************/
/* returns error */
static int
xrdp_iso_process_rdp_neg_req(struct xrdp_iso *self, struct stream *s)
{
    int flags;
    int len;

    if (!s_check_rem(s, 7))
    {
        LLOGLN(10, ("xrdp_iso_process_rdpNegReq: unexpected end-of-record"));
        return 1;
    }

    in_uint8(s, flags);
    if (flags != 0x0 && flags != 0x8 && flags != 0x1)
    {
        LLOGLN(10, ("xrdp_iso_process_rdpNegReq: error, flags: %x",flags));
        return 1;
    }

    in_uint16_le(s, len);
    if (len != 8)
    {
        LLOGLN(10, ("xrdp_iso_process_rdpNegReq: error, length: %x",len));
        return 1;
    }

    in_uint32_le(s, self->requestedProtocol);
    if (self->requestedProtocol > 0xb)
    {
        LLOGLN(10, ("xrdp_iso_process_rdpNegReq: error, requestedProtocol: %x",
                self->requestedProtocol));
        return 1;
    }

    return 0;
}
/*****************************************************************************
 * Reads an X.224 PDU (X.224 section 13) preceded by a T.123 TPKT
 * header (T.123 section 8)
 *
 * On entry, the TPKT header length field will have been inspected and used to
 * set up the input stream.
 *
 * On exit, the TPKT header and the fixed part of the PDU header will have been
 * removed from the stream.
 *
 * Returns error
 *****************************************************************************/
static int
xrdp_iso_recv_msg(struct xrdp_iso *self, struct stream *s, int *code, int *len)
{
    int ver;

    *code = 0;
    *len = 0;

    if (s != self->trans->in_s)
    {
        LLOGLN(10, ("xrdp_iso_recv_msg error logic"));
    }

    /* TPKT header is 4 bytes, then first 2 bytes of the X.224 CR-TPDU */
    if (!s_check_rem(s, 6))
    {
        return 1;
    }

    in_uint8(s, ver);
    in_uint8s(s, 3); /* Skip reserved field, plus length */
    in_uint8(s, *len);
    in_uint8(s, *code);

    if (ver != 3)
    {
        LLOGLN(10, ("xrdp_iso_recv_msg: bad ver"));
        LHEXDUMP(10, (s->data, 4));
        return 1;
    }

    if (*len == 255)
    {
        /* X.224 13.2.1 - reserved value */
        LLOGLN(10, ("xrdp_iso_recv_msg: reserved length encountered"));
        LHEXDUMP(10, (s->data, 4));
        return 1;
    }

    if (*code == ISO_PDU_DT)
    {
        /* Data PDU : X.224 13.7 */
        if (!s_check_rem(s, 1))
        {
            return 1;
        }
        in_uint8s(s, 1);
    }
    else
    {
        /* Other supported PDUs : X.224 13.x */
        if (!s_check_rem(s, 5))
        {
            return 1;
        }
        in_uint8s(s, 5);
    }

    return 0;
}

/*****************************************************************************/
/* returns error */
int
xrdp_iso_recv(struct xrdp_iso *self, struct stream *s)
{
    int code;
    int len;

    LLOGLN(10, ("   in xrdp_iso_recv"));

    if (xrdp_iso_recv_msg(self, s, &code, &len) != 0)
    {
        LLOGLN(10, ("   out xrdp_iso_recv xrdp_iso_recv_msg return non zero"));
        return 1;
    }

    if (code != ISO_PDU_DT || len != 2)
    {
        LLOGLN(10, ("   out xrdp_iso_recv code != ISO_PDU_DT or length != 2"));
        return 1;
    }

    LLOGLN(10, ("   out xrdp_iso_recv"));
    return 0;
}
/*****************************************************************************/
static int
xrdp_iso_send_cc(struct xrdp_iso *self)
{
    struct stream *s;
    char *holdp;
    char *len_ptr;
    char *len_indicator_ptr;
    int len;
    int len_indicator;

    make_stream(s);
    init_stream(s, 8192);

    holdp = s->p;
    /* tpkt */
    out_uint8(s, 3); /* version */
    out_uint8(s, 0); /* pad */
    len_ptr = s->p;
    out_uint16_be(s, 0); /* length, set later */
    /* iso */
    len_indicator_ptr = s->p;
    out_uint8(s, 0); /* length indicator, set later */
    out_uint8(s, ISO_PDU_CC); /* Connection Confirm PDU */
    out_uint16_be(s, 0);
    out_uint16_be(s, 0x1234);
    out_uint8(s, 0);
    /* rdpNegData */
    if (self->rdpNegData)
    {
        if (self->failureCode)
        {
            out_uint8(s, RDP_NEG_FAILURE);
            out_uint8(s, 0); /* no flags */
            out_uint16_le(s, 8); /* must be 8 */
            out_uint32_le(s, self->failureCode); /* failure code */
        }
        else
        {
            out_uint8(s, RDP_NEG_RSP);
            //TODO: hardcoded flags
            out_uint8(s, EXTENDED_CLIENT_DATA_SUPPORTED); /* flags */
            out_uint16_le(s, 8); /* must be 8 */
            out_uint32_le(s, self->selectedProtocol); /* selected protocol */
        }
    }
    s_mark_end(s);

    len = (int) (s->end - holdp);
    len_indicator = (int) (s->end - len_indicator_ptr) - 1;
    len_ptr[0] = len >> 8;
    len_ptr[1] = len;
    len_indicator_ptr[0] = len_indicator;

    if (trans_write_copy_s(self->trans, s) != 0)
    {
        free_stream(s);
        return 1;
    }

    free_stream(s);
    return 0;
}
/*****************************************************************************
 * Process an X.224 connection request PDU
 *
 * See MS-RDPCGR v20190923 sections 2.2.1.1 and 3.3.5.3.1.
 *
 * From the latter, in particular:-
 * - The length embedded in the TPKT header MUST be examined for
 *   consistency with the received data. If there is a discrepancy, the
 *   connection SHOULD be dropped
 * - If the optional routingToken field exists it MUST be ignored.
 * - If the optional cookie field is present it MUST be ignored.
 * - If both the routingToken and cookie fields are present, the server
 *   SHOULD continue with the connection.
 *****************************************************************************/
/* returns error */
int
xrdp_iso_incoming(struct xrdp_iso *self)
{
    int rv = 0;
    int code;
    int len;
    int cc_type;
    struct stream *s;
    int expected_pdu_len;

    LLOGLN(10, ("   in xrdp_iso_incoming"));

    s = libxrdp_force_read(self->trans);
    if (s == NULL)
    {
        return 1;
    }

    if (xrdp_iso_recv_msg(self, s, &code, &len) != 0)
    {
        LLOGLN(0, ("xrdp_iso_incoming: xrdp_iso_recv_msg returned non zero"));
        return 1;
    }

    if (code != ISO_PDU_CR)
    {
        return 1;
    }

    /*
     * Make sure the length indicator field extracted from the X.224
     * connection request TPDU corresponds to the length in the TPKT header.
     *
     * We do this by seeing how the indicator field minus the counted
     * octets in the TPDU header (6) compares with the space left in
     * the stream.
     */
    expected_pdu_len = (s->end - s->p) + 6;
    if (len != expected_pdu_len)
    {
        LLOGLN(0, ("xrdp_iso_incoming: X.224 CR-TPDU length exp %d got %d",
                   expected_pdu_len, len));
        return 1;
    }

    /* process connection request */
    while (s_check_rem(s, 1))
    {
        in_uint8(s, cc_type);
        switch (cc_type)
        {
            default:
                break;
            case RDP_NEG_REQ: /* rdpNegReq 1 */
                self->rdpNegData = 1;
                if (xrdp_iso_process_rdp_neg_req(self, s) != 0)
                {
                    LLOGLN(0, ("xrdp_iso_incoming: xrdp_iso_process_rdpNegReq returned non zero"));
                    return 1;
                }
                break;
            case RDP_CORRELATION_INFO: /* rdpCorrelationInfo 6 */
                // TODO
                if (!s_check_rem(s, 1 + 2 + 16 + 16))
                {
                    LLOGLN(0, ("xrdp_iso_incoming: short correlation info"));
                    return 1;
                }

                in_uint8s(s, 1 + 2 + 16 + 16);
                break;
            case 'C': /* Cookie */
                 /* The routingToken and cookie fields are both ASCII
                  * strings starting with the word 'Cookie: ' and
                  * ending with CR+LF. We ignore both, so we do
                  * not need to distinguish them  */
                while (s_check_rem(s, 1))
                {
                    in_uint8(s, cc_type);
                    if (cc_type == 0x0D && s_check_rem(s, 1))
                    {
                        in_uint8(s, cc_type);
                        if (cc_type == 0x0A)
                        {
                            break;
                        }
                    }
                }
                break;
        }
    }

    /* negotiate client-server security layer */
    rv = xrdp_iso_negotiate_security(self);

    /* send connection confirm back to client */
    if (xrdp_iso_send_cc(self) != 0)
    {
        LLOGLN(0, ("xrdp_iso_incoming: xrdp_iso_send_cc returned non zero"));
        return 1;
    }

    LLOGLN(10, ("   out xrdp_iso_incoming"));
    return rv;
}

/*****************************************************************************/
/* returns error */
int
xrdp_iso_init(struct xrdp_iso *self, struct stream *s)
{
    init_stream(s, 8192 * 4); /* 32 KB */
    s_push_layer(s, iso_hdr, 7);
    return 0;
}

/*****************************************************************************/
/* returns error */
int
xrdp_iso_send(struct xrdp_iso *self, struct stream *s)
{
    int len;

    LLOGLN(10, ("   in xrdp_iso_send"));
    s_pop_layer(s, iso_hdr);
    len = (int) (s->end - s->p);
    out_uint8(s, 3);
    out_uint8(s, 0);
    out_uint16_be(s, len);
    out_uint8(s, 2);
    out_uint8(s, ISO_PDU_DT);
    out_uint8(s, 0x80);

    if (trans_write_copy_s(self->trans, s) != 0)
    {
        return 1;
    }

    LLOGLN(10, ("   out xrdp_iso_send"));
    return 0;
}