gnutls.c

VLC Player Source Code

/*****************************************************************************
 * gnutls.c
 *****************************************************************************
 * Copyright (C) 2004-2006 Rémi Denis-Courmont
 * $Id$
 *
 * Authors: Rémi Denis-Courmont <rem # videolan.org>
 *
 * 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.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <vlc_common.h>
#include <vlc_plugin.h>
#include <errno.h>
#include <time.h>

#include <sys/types.h>
#include <errno.h>
#ifdef HAVE_DIRENT_H
# include <dirent.h>
#endif
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef WIN32
# include <io.h>
#else
# include <unistd.h>
#endif
# include <fcntl.h>


#include <vlc_tls.h>
#include <vlc_charset.h>
#include <vlc_block.h>

#include <gcrypt.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#include <vlc_gcrypt.h>

#define CACHE_TIMEOUT     3600
#define CACHE_SIZE          64

#include "dhparams.h"

#include <assert.h>

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
static int  OpenClient  (vlc_object_t *);
static void CloseClient (vlc_object_t *);
static int  OpenServer  (vlc_object_t *);
static void CloseServer (vlc_object_t *);

#define CACHE_TIMEOUT_TEXT N_("Expiration time for resumed TLS sessions")
#define CACHE_TIMEOUT_LONGTEXT N_( \
    "It is possible to cache the resumed TLS sessions. This is the expiration "\
    "time of the sessions stored in this cache, in seconds." )

#define CACHE_SIZE_TEXT N_("Number of resumed TLS sessions")
#define CACHE_SIZE_LONGTEXT N_( \
    "This is the maximum number of resumed TLS sessions that " \
    "the cache will hold." )

vlc_module_begin();
    set_shortname( "GnuTLS" );
    set_description( N_("GnuTLS transport layer security") );
    set_capability( "tls client", 1 );
    set_callbacks( OpenClient, CloseClient );
    set_category( CAT_ADVANCED );
    set_subcategory( SUBCAT_ADVANCED_MISC );

    add_obsolete_bool( "tls-check-cert" );
    add_obsolete_bool( "tls-check-hostname" );

    add_submodule();
        set_description( N_("GnuTLS server") );
        set_capability( "tls server", 1 );
        set_category( CAT_ADVANCED );
        set_subcategory( SUBCAT_ADVANCED_MISC );
        set_callbacks( OpenServer, CloseServer );

        add_obsolete_integer( "gnutls-dh-bits" );
        add_integer( "gnutls-cache-timeout", CACHE_TIMEOUT, NULL,
                    CACHE_TIMEOUT_TEXT, CACHE_TIMEOUT_LONGTEXT, true );
        add_integer( "gnutls-cache-size", CACHE_SIZE, NULL, CACHE_SIZE_TEXT,
                    CACHE_SIZE_LONGTEXT, true );
vlc_module_end();

/**
 * Initializes GnuTLS with proper locking.
 * @return VLC_SUCCESS on success, a VLC error code otherwise.
 */
static int gnutls_Init (vlc_object_t *p_this)
{
    int ret = VLC_EGENERIC;

    vlc_gcrypt_init (); /* GnuTLS depends on gcrypt */

    vlc_mutex_t *lock = var_AcquireMutex ("gnutls_mutex");
    if (gnutls_global_init ())
    {
        msg_Err (p_this, "cannot initialize GnuTLS");
        goto error;
    }

    const char *psz_version = gnutls_check_version ("1.3.3");
    if (psz_version == NULL)
    {
        msg_Err (p_this, "unsupported GnuTLS version");
        gnutls_global_deinit ();
        goto error;
    }

    msg_Dbg (p_this, "GnuTLS v%s initialized", psz_version);
    ret = VLC_SUCCESS;

error:
    vlc_mutex_unlock (lock);
    return ret;
}


/**
 * Deinitializes GnuTLS.
 */
static void gnutls_Deinit (vlc_object_t *p_this)
{
    vlc_mutex_t *lock = var_AcquireMutex( "gnutls_mutex" );

    gnutls_global_deinit ();
    msg_Dbg (p_this, "GnuTLS deinitialized");
    vlc_mutex_unlock (lock);
}


static int gnutls_Error (vlc_object_t *obj, int val)
{
    switch (val)
    {
        case GNUTLS_E_AGAIN:
#ifndef WIN32
            errno = EAGAIN;
            break;
#endif
            /* WinSock does not return EAGAIN, return EINTR instead */

        case GNUTLS_E_INTERRUPTED:
#ifdef WIN32
            WSASetLastError (WSAEINTR);
#else
            errno = EINTR;
#endif
            break;

        default:
            msg_Err (obj, "%s", gnutls_strerror (val));
#ifndef NDEBUG
            if (!gnutls_error_is_fatal (val))
                msg_Err (obj, "Error above should be handled");
#endif
#ifdef WIN32
            WSASetLastError (WSAECONNRESET);
#else
            errno = ECONNRESET;
#endif
    }
    return -1;
}


struct tls_session_sys_t
{
    gnutls_session_t session;
    char            *psz_hostname;
    bool       b_handshaked;
};


/**
 * Sends data through a TLS session.
 */
static int
gnutls_Send( void *p_session, const void *buf, int i_length )
{
    int val;
    tls_session_sys_t *p_sys;

    p_sys = (tls_session_sys_t *)(((tls_session_t *)p_session)->p_sys);

    val = gnutls_record_send( p_sys->session, buf, i_length );
    return (val < 0) ? gnutls_Error ((vlc_object_t *)p_session, val) : val;
}


/**
 * Receives data through a TLS session.
 */
static int
gnutls_Recv( void *p_session, void *buf, int i_length )
{
    int val;
    tls_session_sys_t *p_sys;

    p_sys = (tls_session_sys_t *)(((tls_session_t *)p_session)->p_sys);

    val = gnutls_record_recv( p_sys->session, buf, i_length );
    return (val < 0) ? gnutls_Error ((vlc_object_t *)p_session, val) : val;
}


/**
 * Starts or continues the TLS handshake.
 *
 * @return -1 on fatal error, 0 on succesful handshake completion,
 * 1 if more would-be blocking recv is needed,
 * 2 if more would-be blocking send is required.
 */
static int
gnutls_ContinueHandshake (tls_session_t *p_session)
{
    tls_session_sys_t *p_sys = p_session->p_sys;
    int val;

#ifdef WIN32
    WSASetLastError( 0 );
#endif
    val = gnutls_handshake( p_sys->session );
    if( ( val == GNUTLS_E_AGAIN ) || ( val == GNUTLS_E_INTERRUPTED ) )
        return 1 + gnutls_record_get_direction( p_sys->session );

    if( val < 0 )
    {
#ifdef WIN32
        msg_Dbg( p_session, "Winsock error %d", WSAGetLastError( ) );
#endif
        msg_Err( p_session, "TLS handshake error: %s",
                 gnutls_strerror( val ) );
        return -1;
    }

    p_sys->b_handshaked = true;
    return 0;
}


typedef struct
{
    int flag;
    const char *msg;
} error_msg_t;

static const error_msg_t cert_errors[] =
{
    { GNUTLS_CERT_INVALID,
        "Certificate could not be verified" },
    { GNUTLS_CERT_REVOKED,
        "Certificate was revoked" },
    { GNUTLS_CERT_SIGNER_NOT_FOUND,
        "Certificate's signer was not found" },
    { GNUTLS_CERT_SIGNER_NOT_CA,
        "Certificate's signer is not a CA" },
    { GNUTLS_CERT_INSECURE_ALGORITHM,
        "Insecure certificate signature algorithm" },
    { 0, NULL }
};


static int
gnutls_HandshakeAndValidate( tls_session_t *session )
{
    int val = gnutls_ContinueHandshake( session );
    if( val )
        return val;

    tls_session_sys_t *p_sys = (tls_session_sys_t *)(session->p_sys);

    /* certificates chain verification */
    unsigned status;
    val = gnutls_certificate_verify_peers2( p_sys->session, &status );

    if( val )
    {
        msg_Err( session, "Certificate verification failed: %s",
                 gnutls_strerror( val ) );
        return -1;
    }

    if( status )
    {
        msg_Err( session, "TLS session: access denied" );
        for( const error_msg_t *e = cert_errors; e->flag; e++ )
        {
            if( status & e->flag )
            {
                msg_Err( session, "%s", e->msg );
                status &= ~e->flag;
            }
        }

        if( status )
            msg_Err( session,
                     "unknown certificate error (you found a bug in VLC)" );

        return -1;
    }

    /* certificate (host)name verification */
    const gnutls_datum_t *data;
    data = gnutls_certificate_get_peers (p_sys->session, &(unsigned){0});
    if( data == NULL )
    {
        msg_Err( session, "Peer certificate not available" );
        return -1;
    }

    gnutls_x509_crt_t cert;
    val = gnutls_x509_crt_init( &cert );
    if( val )
    {
        msg_Err( session, "x509 fatal error: %s", gnutls_strerror( val ) );
        return -1;
    }

    val = gnutls_x509_crt_import( cert, data, GNUTLS_X509_FMT_DER );
    if( val )
    {
        msg_Err( session, "Certificate import error: %s",
                 gnutls_strerror( val ) );
        goto error;
    }

    assert( p_sys->psz_hostname != NULL );
    if ( !gnutls_x509_crt_check_hostname( cert, p_sys->psz_hostname ) )
    {
        msg_Err( session, "Certificate does not match \"%s\"",
                 p_sys->psz_hostname );
        goto error;
    }

    if( gnutls_x509_crt_get_expiration_time( cert ) < time( NULL ) )
    {
        msg_Err( session, "Certificate expired" );
        goto error;
    }

    if( gnutls_x509_crt_get_activation_time( cert ) > time ( NULL ) )
    {
        msg_Err( session, "Certificate not yet valid" );
        goto error;
    }

    gnutls_x509_crt_deinit( cert );
    msg_Dbg( session, "TLS/x509 certificate verified" );
    return 0;

error:
    gnutls_x509_crt_deinit( cert );
    return -1;
}

/**
 * Sets the operating system file descriptor backend for the TLS sesison.
 *
 * @param fd stream socket already connected with the peer.
 */