gnutls.c

video linux conference

/*****************************************************************************
 * tls.c
 *****************************************************************************
 * Copyright (C) 2004-2005 VideoLAN
 * $Id: gnutls.c 10620 2005-04-09 14:54:44Z courmisch $
 *
 * Authors: Remi 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., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*
 * TODO:
 * - fix FIXMEs
 */


/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include <stdlib.h>
#include <errno.h>
#include <vlc/vlc.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>
# ifdef HAVE_UNISTD_H
#  include <unistd.h>
# endif
#endif


#include "vlc_tls.h"

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

#define DH_BITS             1024
#define CACHE_EXPIRATION    3600
#define CACHE_SIZE          64

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
static int  Open ( vlc_object_t * );
static void Close( vlc_object_t * );

#define DH_BITS_TEXT N_("Diffie-Hellman prime bits")
#define DH_BITS_LONGTEXT N_( \
    "Allows you to modify the Diffie-Hellman prime's number of bits " \
    "(used for TLS or SSL-based server-side encryption)." )

#define CACHE_EXPIRATION_TEXT N_("Expiration time for resumed TLS sessions")
#define CACHE_EXPIRATION_LONGTEXT N_( \
    "Defines the delay before resumed TLS sessions will be expired " \
    "(in seconds)." )

#define CACHE_SIZE_TEXT N_("Number of resumed TLS sessions")
#define CACHE_SIZE_LONGTEXT N_( \
    "Allows you to modify the maximum number of resumed TLS sessions that " \
    "the cache will hold." )

#define CHECK_CERT_TEXT N_("Check TLS/SSL server certificate validity")
#define CHECK_CERT_LONGTEXT N_( \
    "Ensures that server certificate is valid " \
    "(ie. signed by an approved Certificate Authority)." )

#define CHECK_HOSTNAME_TEXT N_("Check TLS/SSL server hostname in certificate")
#define CHECK_HOSTNAME_LONGTEXT N_( \
    "Ensures that server hostname in certificate match requested host name." )

vlc_module_begin();
    set_shortname( "GnuTLS" );
    set_description( _("GnuTLS TLS encryption layer") );
    set_capability( "tls", 1 );
    set_callbacks( Open, Close );
    set_category( CAT_ADVANCED );
    set_subcategory( SUBCAT_ADVANCED_MISC );

    add_bool( "tls-check-cert", VLC_FALSE, NULL, CHECK_CERT_TEXT,
              CHECK_CERT_LONGTEXT, VLC_FALSE );
    add_bool( "tls-check-hostname", VLC_FALSE, NULL, CHECK_HOSTNAME_TEXT,
              CHECK_HOSTNAME_LONGTEXT, VLC_FALSE );

    add_integer( "dh-bits", DH_BITS, NULL, DH_BITS_TEXT,
                 DH_BITS_LONGTEXT, VLC_TRUE );
    add_integer( "tls-cache-expiration", CACHE_EXPIRATION, NULL,
                 CACHE_EXPIRATION_TEXT, CACHE_EXPIRATION_LONGTEXT, VLC_TRUE );
    add_integer( "tls-cache-size", CACHE_SIZE, NULL, CACHE_SIZE_TEXT,
                 CACHE_SIZE_LONGTEXT, VLC_TRUE );
vlc_module_end();


#define MAX_SESSION_ID    32
#define MAX_SESSION_DATA  1024

typedef struct saved_session_t
{
    char id[MAX_SESSION_ID];
    char data[MAX_SESSION_DATA];

    unsigned i_idlen;
    unsigned i_datalen;
} saved_session_t;


typedef struct tls_server_sys_t
{
    gnutls_certificate_credentials  x509_cred;
    gnutls_dh_params                dh_params;

    struct saved_session_t          *p_cache;
    struct saved_session_t          *p_store;
    int                             i_cache_size;
    vlc_mutex_t                     cache_lock;

    int                             (*pf_handshake2)( tls_session_t * );
} tls_server_sys_t;


typedef struct tls_session_sys_t
{
    gnutls_session  session;
    char            *psz_hostname;
    vlc_bool_t      b_handshaked;
} tls_session_sys_t;


typedef struct tls_client_sys_t
{
    struct tls_session_sys_t       session;
    gnutls_certificate_credentials x509_cred;
} tls_client_sys_t;


static int
_get_Int( vlc_object_t *p_this, const char *var )
{
    vlc_value_t value;

    if( var_Get( p_this, var, &value ) != VLC_SUCCESS )
    {
        var_Create( p_this, var, VLC_VAR_INTEGER | VLC_VAR_DOINHERIT );
        var_Get( p_this, var, &value );
    }

    return value.i_int;
}

static int
_get_Bool( vlc_object_t *p_this, const char *var )
{
    vlc_value_t value;

    if( var_Get( p_this, var, &value ) != VLC_SUCCESS )
    {
        var_Create( p_this, var, VLC_VAR_BOOL | VLC_VAR_DOINHERIT );
        var_Get( p_this, var, &value );
    }

    return value.b_bool;
}

#define get_Int( a, b ) _get_Int( (vlc_object_t *)(a), (b) )
#define get_Bool( a, b ) _get_Bool( (vlc_object_t *)(a), (b) )


/*****************************************************************************
 * tls_Send:
 *****************************************************************************
 * 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 );
    /* TODO: handle fatal error */
    return val < 0 ? -1 : val;
}


/*****************************************************************************
 * tls_Recv:
 *****************************************************************************
 * 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 );
    /* TODO: handle fatal error */
    return val < 0 ? -1 : val;
}


/*****************************************************************************
 * tls_Session(Continue)?Handshake:
 *****************************************************************************
 * Establishes TLS session with a peer through socket <fd>.
 * Returns -1 on error (you need not and must not call tls_SessionClose)
 * 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;
    int val;

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

     /* TODO: handle fatal error */
    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 )
    {
        msg_Err( p_session, "TLS handshake failed : %s",
                 gnutls_strerror( val ) );
        p_session->pf_close( p_session );
        return -1;
    }

    p_sys->b_handshaked = VLC_TRUE;
    return 0;
}

static int
gnutls_HandshakeAndValidate( tls_session_t *p_session )
{
    int val;

    val = gnutls_ContinueHandshake( p_session );
    if( val == 0 )
    {
        int status;
        gnutls_x509_crt cert;
        const gnutls_datum *p_data;
        tls_session_sys_t *p_sys;

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

        if( val )
        {
            msg_Err( p_session, "TLS certificate verification failed : %s",
                     gnutls_strerror( val ) );
            p_session->pf_close( p_session );
            return -1;
        }

        if( status )
        {
            msg_Warn( p_session, "TLS session : access denied" );
            if( status & GNUTLS_CERT_INVALID )
                msg_Dbg( p_session, "certificate could not be verified" );
            if( status & GNUTLS_CERT_REVOKED )
                msg_Dbg( p_session, "certificate was revoked" );
            if( status & GNUTLS_CERT_SIGNER_NOT_FOUND )
                msg_Dbg( p_session, "certificate's signer was not found" );
            if( status & GNUTLS_CERT_SIGNER_NOT_CA )
                msg_Dbg( p_session, "certificate's signer is not a CA" );
            p_session->pf_close( p_session );
            return -1;
        }

        msg_Dbg( p_session, "TLS certificate verified" );
        if( p_sys->psz_hostname == NULL )
            return 0;

        /* certificate (host)name verification */
        p_data = gnutls_certificate_get_peers( p_sys->session, &val );
        if( p_data == NULL )
        {
            msg_Err( p_session, "TLS peer certificate not available" );
            p_session->pf_close( p_session );
            return -1;
        }

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

        val = gnutls_x509_crt_import( cert, p_data, GNUTLS_X509_FMT_DER );
        if( val )
        {
            msg_Err( p_session, "x509 certificate import error : %s",
                     gnutls_strerror( val ) );
            gnutls_x509_crt_deinit( cert );
            p_session->pf_close( p_session );
            return -1;
        }

        if( gnutls_x509_crt_check_hostname( cert, p_sys->psz_hostname ) == 0 )
        {
            msg_Err( p_session, "x509 certificate does not match \"%s\"",
                     p_sys->psz_hostname );
            gnutls_x509_crt_deinit( cert );
            p_session->pf_close( p_session );
            return -1;
        }

        gnutls_x509_crt_deinit( cert );
        
        msg_Dbg( p_session, "x509 hostname verified" );
        return 0;
    }

    return val;
}

static int
gnutls_BeginHandshake( tls_session_t *p_session, int fd,
                         const char *psz_hostname )
{
    tls_session_sys_t *p_sys;

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

    gnutls_transport_set_ptr (p_sys->session, (gnutls_transport_ptr)fd);

    if( psz_hostname != NULL )
    {
        gnutls_server_name_set( p_sys->session, GNUTLS_NAME_DNS, psz_hostname,
                                strlen( psz_hostname ) );
        if( get_Bool( p_session, "tls-check-hostname" ) )
        {
            p_sys->psz_hostname = strdup( psz_hostname );
            if( p_sys->psz_hostname == NULL )
            {
                p_session->pf_close( p_session );
                return -1;
            }
        }
    }

    return p_session->pf_handshake2( p_session );
}

/*****************************************************************************
 * tls_SessionClose:
 *****************************************************************************
 * Terminates TLS session and releases session data.
 *****************************************************************************/
static void
gnutls_SessionClose( tls_session_t *p_session )