xrdp/common/xrdp_tls.c

/**
 * xrdp: A Remote Desktop Protocol server.
 *
 * 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.
 *
 * transport layer security
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/ssl.h>

#include "os_calls.h"
#include "trans.h"
#include "ssl_calls.h"


/*****************************************************************************/
struct xrdp_tls *
APP_CC
xrdp_tls_create(struct trans *trans, const char *key, const char *cert)
{
    struct xrdp_tls *self;
    self = (struct xrdp_tls *) g_malloc(sizeof(struct xrdp_tls), 1);

    if (self != NULL)
    {
        self->trans = trans;
        self->cert = (char *) cert;
        self->key = (char *) key;
    }

    return self;
}

/*****************************************************************************/
int APP_CC
xrdp_tls_print_error(char *func, SSL *connection, int value)
{
    switch (SSL_get_error(connection, value))
    {
        case SSL_ERROR_ZERO_RETURN:
            g_writeln("xrdp_tls_print_error: %s: Server closed TLS connection",
                      func);
            return 1;

        case SSL_ERROR_WANT_READ:
            g_writeln("xrdp_tls_print_error: SSL_ERROR_WANT_READ");
            return 0;

        case SSL_ERROR_WANT_WRITE:
            g_writeln("xrdp_tls_print_error: SSL_ERROR_WANT_WRITE");
            return 0;

        case SSL_ERROR_SYSCALL:
            g_writeln("xrdp_tls_print_error: %s: I/O error", func);
            return 1;

        case SSL_ERROR_SSL:
            g_writeln("xrdp_tls_print_error: %s: Failure in SSL library (protocol error?)",
                      func);
            return 1;

        default:
            g_writeln("xrdp_tls_print_error: %s: Unknown error", func);
            return 1;
    }
}

/*****************************************************************************/
int APP_CC
xrdp_tls_accept(struct xrdp_tls *self)
{
    int connection_status;
    long options = 0;

    /**
     * SSL_OP_NO_SSLv2:
     *
     * We only want SSLv3 and TLSv1, so disable SSLv2.
     * SSLv3 is used by, eg. Microsoft RDC for Mac OS X.
     */
    options |= SSL_OP_NO_SSLv2;

#if defined(SSL_OP_NO_COMPRESSION)
    /**
     * SSL_OP_NO_COMPRESSION:
     *
     * The Microsoft RDP server does not advertise support
     * for TLS compression, but alternative servers may support it.
     * This was observed between early versions of the FreeRDP server
     * and the FreeRDP client, and caused major performance issues,
     * which is why we're disabling it.
     */
    options |= SSL_OP_NO_COMPRESSION;
#endif

    /**
     * SSL_OP_TLS_BLOCK_PADDING_BUG:
     *
     * The Microsoft RDP server does *not* support TLS padding.
     * It absolutely needs to be disabled otherwise it won't work.
     */
    options |= SSL_OP_TLS_BLOCK_PADDING_BUG;

    /**
     * SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS:
     *
     * Just like TLS padding, the Microsoft RDP server does not
     * support empty fragments. This needs to be disabled.
     */
    options |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;

    self->ctx = SSL_CTX_new(SSLv23_server_method());
    /* set context options */
    SSL_CTX_set_mode(self->ctx,
                     SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER |
                     SSL_MODE_ENABLE_PARTIAL_WRITE);
    SSL_CTX_set_options(self->ctx, options);
    SSL_CTX_set_read_ahead(self->ctx, 1);

    if (self->ctx == NULL)
    {
        g_writeln("xrdp_tls_accept: SSL_CTX_new failed");
        return 1;
    }

    if (SSL_CTX_use_RSAPrivateKey_file(self->ctx, self->key, SSL_FILETYPE_PEM)
            <= 0)
    {
        g_writeln("xrdp_tls_accept: SSL_CTX_use_RSAPrivateKey_file failed");
        return 1;
    }

    self->ssl = SSL_new(self->ctx);

    if (self->ssl == NULL)
    {
        g_writeln("xrdp_tls_accept: SSL_new failed");
        return 1;
    }

    if (SSL_use_certificate_file(self->ssl, self->cert, SSL_FILETYPE_PEM) <= 0)
    {
        g_writeln("xrdp_tls_accept: SSL_use_certificate_file failed");
        return 1;
    }

    if (SSL_set_fd(self->ssl, self->trans->sck) < 1)
    {
        g_writeln("xrdp_tls_accept: SSL_set_fd failed");
        return 1;
    }

    connection_status = SSL_accept(self->ssl);

    if (connection_status <= 0)
    {
        if (xrdp_tls_print_error("SSL_accept", self->ssl, connection_status))
        {
            return 1;
        }
    }

    g_writeln("xrdp_tls_accept: TLS connection accepted");

    return 0;
}
/*****************************************************************************/
int APP_CC
xrdp_tls_disconnect(struct xrdp_tls *self)
{
    int status = SSL_shutdown(self->ssl);
    while (status != 1)
    {
        status = SSL_shutdown(self->ssl);

        if (status <= 0)
        {
            if (xrdp_tls_print_error("SSL_shutdown", self->ssl, status))
            {
                return 1;
            }
        }
    }
    return 0;
}
/*****************************************************************************/
void APP_CC
xrdp_tls_delete(struct xrdp_tls *self)
{
    if (self != NULL)
    {
        if (self->ssl)
            SSL_free(self->ssl);

        if (self->ctx)
            SSL_CTX_free(self->ctx);

        g_free(self);
    }
}
/*****************************************************************************/
int APP_CC
xrdp_tls_read(struct xrdp_tls *tls, char *data, int length)
{
    int status;

    status = SSL_read(tls->ssl, data, length);

    switch (SSL_get_error(tls->ssl, status))
    {
        case SSL_ERROR_NONE:
            break;

        case SSL_ERROR_WANT_READ:
        case SSL_ERROR_WANT_WRITE:
            status = 0;
            break;

        default:
            xrdp_tls_print_error("SSL_read", tls->ssl, status);
            status = -1;
            break;
    }

    return status;
}
/*****************************************************************************/
int APP_CC
xrdp_tls_write(struct xrdp_tls *tls, char *data, int length)
{
    int status;

    status = SSL_write(tls->ssl, data, length);

    switch (SSL_get_error(tls->ssl, status))
    {
        case SSL_ERROR_NONE:
            break;

        case SSL_ERROR_WANT_READ:
        case SSL_ERROR_WANT_WRITE:
            status = 0;
            break;

        default:
            xrdp_tls_print_error("SSL_write", tls->ssl, status);
            status = -1;
            break;
    }

    return status;
}