source: protocols/jabber/sasl.c @ fd213fe

/***************************************************************************\
*                                                                           *
*  BitlBee - An IRC to IM gateway                                           *
*  Jabber module - SASL authentication                                      *
*                                                                           *
*  Copyright 2006-2012 Wilmer van der Gaast <wilmer@gaast.net>              *
*                                                                           *
*  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.              *
*                                                                           *
\***************************************************************************/

#include <ctype.h>

#include "jabber.h"
#include "base64.h"
#include "oauth2.h"
#include "oauth.h"

const struct oauth2_service oauth2_service_google =
{
        "https://accounts.google.com/o/oauth2/auth",
        "https://accounts.google.com/o/oauth2/token",
        "urn:ietf:wg:oauth:2.0:oob",
        "https://www.googleapis.com/auth/googletalk",
        "783993391592.apps.googleusercontent.com",
        "6C-Zgf7Tr7gEQTPlBhMUgo7R",
};
const struct oauth2_service oauth2_service_facebook =
{
        "https://www.facebook.com/dialog/oauth",
        "https://graph.facebook.com/oauth/access_token",
        "http://www.bitlbee.org/main.php/Facebook/oauth2.html",
        "offline_access,xmpp_login",
        "126828914005625",
        "4b100f0f244d620bf3f15f8b217d4c32",
};

xt_status sasl_pkt_mechanisms( struct xt_node *node, gpointer data )
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        struct xt_node *c, *reply;
        char *s;
        int sup_plain = 0, sup_digest = 0, sup_gtalk = 0, sup_fb = 0;
        int want_oauth = FALSE;
        GString *mechs;
        
        if( !sasl_supported( ic ) )
        {
                /* Should abort this now, since we should already be doing
                   IQ authentication. Strange things happen when you try
                   to do both... */
                imcb_log( ic, "XMPP 1.0 non-compliant server seems to support SASL, please report this as a BitlBee bug!" );
                return XT_HANDLED;
        }
        
        s = xt_find_attr( node, "xmlns" );
        if( !s || strcmp( s, XMLNS_SASL ) != 0 )
        {
                imcb_log( ic, "Stream error while authenticating" );
                imc_logout( ic, FALSE );
                return XT_ABORT;
        }
        
        want_oauth = set_getbool( &ic->acc->set, "oauth" );
        
        mechs = g_string_new( "" );
        c = node->children;
        while( ( c = xt_find_node( c, "mechanism" ) ) )
        {
                if( c->text && g_strcasecmp( c->text, "PLAIN" ) == 0 )
                        sup_plain = 1;
                else if( c->text && g_strcasecmp( c->text, "DIGEST-MD5" ) == 0 )
                        sup_digest = 1;
                else if( c->text && g_strcasecmp( c->text, "X-OAUTH2" ) == 0 )
                        sup_gtalk = 1;
                else if( c->text && g_strcasecmp( c->text, "X-FACEBOOK-PLATFORM" ) == 0 )
                        sup_fb = 1;
                
                if( c->text )
                        g_string_append_printf( mechs, " %s", c->text );
                
                c = c->next;
        }
        
        if( !want_oauth && !sup_plain && !sup_digest )
        {
                if( !sup_gtalk && !sup_fb )
                        imcb_error( ic, "This server requires OAuth "
                                        "(supported schemes:%s)", mechs->str );
                else
                        imcb_error( ic, "BitlBee does not support any of the offered SASL "
                                        "authentication schemes:%s", mechs->str );
                imc_logout( ic, FALSE );
                g_string_free( mechs, TRUE );
                return XT_ABORT;
        }
        g_string_free( mechs, TRUE );
        
        reply = xt_new_node( "auth", NULL, NULL );
        xt_add_attr( reply, "xmlns", XMLNS_SASL );
        
        if( sup_gtalk && want_oauth )
        {
                int len;
                
                /* X-OAUTH2 is, not *the* standard OAuth2 SASL/XMPP implementation.
                   It's currently used by GTalk and vaguely documented on
                   http://code.google.com/apis/cloudprint/docs/rawxmpp.html . */
                xt_add_attr( reply, "mechanism", "X-OAUTH2" );
                
                len = strlen( jd->username ) + strlen( jd->oauth2_access_token ) + 2;
                s = g_malloc( len + 1 );
                s[0] = 0;
                strcpy( s + 1, jd->username );
                strcpy( s + 2 + strlen( jd->username ), jd->oauth2_access_token );
                reply->text = base64_encode( (unsigned char *)s, len );
                reply->text_len = strlen( reply->text );
                g_free( s );
        }
        else if( sup_fb && want_oauth )
        {
                xt_add_attr( reply, "mechanism", "X-FACEBOOK-PLATFORM" );
                jd->flags |= JFLAG_SASL_FB;
        }
        else if( want_oauth )
        {
                imcb_error( ic, "OAuth requested, but not supported by server" );
                imc_logout( ic, FALSE );
                xt_free_node( reply );
                return XT_ABORT;
        }
        else if( sup_digest )
        {
                xt_add_attr( reply, "mechanism", "DIGEST-MD5" );
                
                /* The rest will be done later, when we receive a <challenge/>. */
        }
        else if( sup_plain )
        {
                int len;
                
                xt_add_attr( reply, "mechanism", "PLAIN" );
                
                /* With SASL PLAIN in XMPP, the text should be b64(\0user\0pass) */
                len = strlen( jd->username ) + strlen( ic->acc->pass ) + 2;
                s = g_malloc( len + 1 );
                s[0] = 0;
                strcpy( s + 1, jd->username );
                strcpy( s + 2 + strlen( jd->username ), ic->acc->pass );
                reply->text = base64_encode( (unsigned char *)s, len );
                reply->text_len = strlen( reply->text );
                g_free( s );
        }
        
        if( reply && !jabber_write_packet( ic, reply ) )
        {
                xt_free_node( reply );
                return XT_ABORT;
        }
        xt_free_node( reply );
        
        /* To prevent classic authentication from happening. */
        jd->flags |= JFLAG_STREAM_STARTED;
        
        return XT_HANDLED;
}

/* Non-static function, but not mentioned in jabber.h because it's for internal
   use, just that the unittest should be able to reach it... */
char *sasl_get_part( char *data, char *field )
{
        int i, len;
        
        len = strlen( field );
        
        while( g_ascii_isspace( *data ) || *data == ',' )
                data ++;
        
        if( g_strncasecmp( data, field, len ) == 0 && data[len] == '=' )
        {
                i = strlen( field ) + 1;
        }
        else
        {
                for( i = 0; data[i]; i ++ )
                {
                        /* If we have a ", skip until it's closed again. */
                        if( data[i] == '"' )
                        {
                                i ++;
                                while( data[i] != '"' || data[i-1] == '\\' )
                                        i ++;
                        }
                        
                        /* If we got a comma, we got a new field. Check it,
                           find the next key after it. */
                        if( data[i] == ',' )
                        {
                                while( g_ascii_isspace( data[i] ) || data[i] == ',' )
                                        i ++;
                                
                                if( g_strncasecmp( data + i, field, len ) == 0 &&
                                    data[i+len] == '=' )
                                {
                                        i += len + 1;
                                        break;
                                }
                        }
                }
        }
        
        if( data[i] == '"' )
        {
                int j;
                char *ret;
                
                i ++;
                len = 0;
                while( data[i+len] != '"' || data[i+len-1] == '\\' )
                        len ++;
                
                ret = g_strndup( data + i, len );
                for( i = j = 0; ret[i]; i ++ )
                {
                        if( ret[i] == '\\' )
                        {
                                ret[j++] = ret[++i];
                        }
                        else
                        {
                                ret[j++] = ret[i];
                        }
                }
                ret[j] = 0;
                
                return ret;
        }
        else if( data[i] )
        {
                len = 0;
                while( data[i+len] && data[i+len] != ',' )
                        len ++;
                
                return g_strndup( data + i, len );
        }
        else
        {
                return NULL;
        }
}

xt_status sasl_pkt_challenge( struct xt_node *node, gpointer data )
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        struct xt_node *reply_pkt = NULL;
        char *nonce = NULL, *realm = NULL, *cnonce = NULL;
        unsigned char cnonce_bin[30];
        char *digest_uri = NULL;
        char *dec = NULL;
        char *s = NULL, *reply = NULL;
        xt_status ret = XT_ABORT;
        
        if( node->text_len == 0 )
                goto error;
        
        dec = frombase64( node->text );
        
        if( jd->flags & JFLAG_SASL_FB )
        {
                /* New-style Facebook OAauth2 support. Instead of sending a refresh
                   token, they just send an access token that should never expire. */
                GSList *p_in = NULL, *p_out = NULL;
                char time[33];
                
                oauth_params_parse( &p_in, dec );
                oauth_params_add( &p_out, "nonce", oauth_params_get( &p_in, "nonce" ) );
                oauth_params_add( &p_out, "method", oauth_params_get( &p_in, "method" ) );
                oauth_params_free( &p_in );
                
                g_snprintf( time, sizeof( time ), "%lld", (long long) ( gettime() * 1000 ) );
                oauth_params_add( &p_out, "call_id", time );
                oauth_params_add( &p_out, "api_key", oauth2_service_facebook.consumer_key );
                oauth_params_add( &p_out, "v", "1.0" );
                oauth_params_add( &p_out, "format", "XML" );
                oauth_params_add( &p_out, "access_token", jd->oauth2_access_token );
                
                reply = oauth_params_string( p_out );
                oauth_params_free( &p_out );
        }
        else if( !( s = sasl_get_part( dec, "rspauth" ) ) )
        {
                /* See RFC 2831 for for information. */
                md5_state_t A1, A2, H;
                md5_byte_t A1r[16], A2r[16], Hr[16];
                char A1h[33], A2h[33], Hh[33];
                int i;
                
                nonce = sasl_get_part( dec, "nonce" );
                realm = sasl_get_part( dec, "realm" );
                
                if( !nonce )
                        goto error;
                
                /* Jabber.Org considers the realm part optional and doesn't
                   specify one. Oh well, actually they're right, but still,
                   don't know if this is right... */
                if( !realm )
                        realm = g_strdup( jd->server );
                
                random_bytes( cnonce_bin, sizeof( cnonce_bin ) );
                cnonce = base64_encode( cnonce_bin, sizeof( cnonce_bin ) );
                digest_uri = g_strdup_printf( "%s/%s", "xmpp", jd->server );
                
                /* Generate the MD5 hash of username:realm:password,
                   I decided to call it H. */
                md5_init( &H );
                s = g_strdup_printf( "%s:%s:%s", jd->username, realm, ic->acc->pass );
                md5_append( &H, (unsigned char *) s, strlen( s ) );
                g_free( s );
                md5_finish( &H, Hr );
                
                /* Now generate the hex. MD5 hash of H:nonce:cnonce, called A1. */
                md5_init( &A1 );
                s = g_strdup_printf( ":%s:%s", nonce, cnonce );
                md5_append( &A1, Hr, 16 );
                md5_append( &A1, (unsigned char *) s, strlen( s ) );
                g_free( s );
                md5_finish( &A1, A1r );
                for( i = 0; i < 16; i ++ )
                        sprintf( A1h + i * 2, "%02x", A1r[i] );
                
                /* A2... */
                md5_init( &A2 );
                s = g_strdup_printf( "%s:%s", "AUTHENTICATE", digest_uri );
                md5_append( &A2, (unsigned char *) s, strlen( s ) );
                g_free( s );
                md5_finish( &A2, A2r );
                for( i = 0; i < 16; i ++ )
                        sprintf( A2h + i * 2, "%02x", A2r[i] );
                
                /* Final result: A1:nonce:00000001:cnonce:auth:A2. Let's reuse H for it. */
                md5_init( &H );
                s = g_strdup_printf( "%s:%s:%s:%s:%s:%s", A1h, nonce, "00000001", cnonce, "auth", A2h );
                md5_append( &H, (unsigned char *) s, strlen( s ) );
                g_free( s );
                md5_finish( &H, Hr );
                for( i = 0; i < 16; i ++ )
                        sprintf( Hh + i * 2, "%02x", Hr[i] );
                
                /* Now build the SASL response string: */
                reply = g_strdup_printf( "username=\"%s\",realm=\"%s\",nonce=\"%s\",cnonce=\"%s\","
                                         "nc=%08x,qop=auth,digest-uri=\"%s\",response=%s,charset=%s",
                                         jd->username, realm, nonce, cnonce, 1, digest_uri, Hh, "utf-8" );
        }
        else
        {
                /* We found rspauth, but don't really care... */
                g_free( s );
        }
        
        s = reply ? tobase64( reply ) : NULL;
        reply_pkt = xt_new_node( "response", s, NULL );
        xt_add_attr( reply_pkt, "xmlns", XMLNS_SASL );
        
        if( !jabber_write_packet( ic, reply_pkt ) )
                goto silent_error;
        
        ret = XT_HANDLED;
        goto silent_error;

error:
        imcb_error( ic, "Incorrect SASL challenge received" );
        imc_logout( ic, FALSE );

silent_error:
        g_free( digest_uri );
        g_free( cnonce );
        g_free( nonce );
        g_free( reply );
        g_free( realm );
        g_free( dec );
        g_free( s );
        xt_free_node( reply_pkt );
        
        return ret;
}

xt_status sasl_pkt_result( struct xt_node *node, gpointer data )
{
        struct im_connection *ic = data;
        struct jabber_data *jd = ic->proto_data;
        char *s;
        
        s = xt_find_attr( node, "xmlns" );
        if( !s || strcmp( s, XMLNS_SASL ) != 0 )
        {
                imcb_log( ic, "Stream error while authenticating" );
                imc_logout( ic, FALSE );
                return XT_ABORT;
        }
        
        if( strcmp( node->name, "success" ) == 0 )
        {
                imcb_log( ic, "Authentication finished" );
                jd->flags |= JFLAG_AUTHENTICATED | JFLAG_STREAM_RESTART;
        }
        else if( strcmp( node->name, "failure" ) == 0 )
        {
                imcb_error( ic, "Authentication failure" );
                imc_logout( ic, FALSE );
                return XT_ABORT;
        }
        
        return XT_HANDLED;
}

/* This one is needed to judge if we'll do authentication using IQ or SASL.
   It's done by checking if the <stream:stream> from the server has a
   version attribute. I don't know if this is the right way though... */
gboolean sasl_supported( struct im_connection *ic )
{
        struct jabber_data *jd = ic->proto_data;
        
        return ( jd->xt && jd->xt->root && xt_find_attr( jd->xt->root, "version" ) ) != 0;
}

void sasl_oauth2_init( struct im_connection *ic )
{
        struct jabber_data *jd = ic->proto_data;
        char *msg, *url;
        
        imcb_log( ic, "Starting OAuth authentication" );
        
        /* Temporary contact, just used to receive the OAuth response. */
        imcb_add_buddy( ic, JABBER_OAUTH_HANDLE, NULL );
        url = oauth2_url( jd->oauth2_service );
        msg = g_strdup_printf( "Open this URL in your browser to authenticate: %s", url );
        imcb_buddy_msg( ic, JABBER_OAUTH_HANDLE, msg, 0, 0 );
        imcb_buddy_msg( ic, JABBER_OAUTH_HANDLE, "Respond to this message with the returned "
                                                 "authorization token.", 0, 0 );
        
        g_free( msg );
        g_free( url );
}

static gboolean sasl_oauth2_remove_contact( gpointer data, gint fd, b_input_condition cond )
{
        struct im_connection *ic = data;
        if( g_slist_find( jabber_connections, ic ) )
                imcb_remove_buddy( ic, JABBER_OAUTH_HANDLE, NULL );
        return FALSE;
}

static void sasl_oauth2_got_token( gpointer data, const char *access_token, const char *refresh_token, const char *error );

int sasl_oauth2_get_refresh_token( struct im_connection *ic, const char *msg )
{
        struct jabber_data *jd = ic->proto_data;
        char *code;
        int ret;
        
        imcb_log( ic, "Requesting OAuth access token" );
        
        /* Don't do it here because the caller may get confused if the contact
           we're currently sending a message to is deleted. */
        b_timeout_add( 1, sasl_oauth2_remove_contact, ic );
        
        code = g_strdup( msg );
        g_strstrip( code );
        ret = oauth2_access_token( jd->oauth2_service, OAUTH2_AUTH_CODE,
                                   code, sasl_oauth2_got_token, ic );
        
        g_free( code );
        return ret;
}

int sasl_oauth2_refresh( struct im_connection *ic, const char *refresh_token )
{
        struct jabber_data *jd = ic->proto_data;
        
        return oauth2_access_token( jd->oauth2_service, OAUTH2_AUTH_REFRESH,
                                    refresh_token, sasl_oauth2_got_token, ic );
}

static void sasl_oauth2_got_token( gpointer data, const char *access_token, const char *refresh_token, const char *error )
{
        struct im_connection *ic = data;
        struct jabber_data *jd;
        GSList *auth = NULL;
        
        if( g_slist_find( jabber_connections, ic ) == NULL )
                return;
        
        jd = ic->proto_data;
        
        if( access_token == NULL )
        {
                imcb_error( ic, "OAuth failure (%s)", error );
                imc_logout( ic, TRUE );
                return;
        }
        
        oauth_params_parse( &auth, ic->acc->pass );
        if( refresh_token )
                oauth_params_set( &auth, "refresh_token", refresh_token );
        if( access_token )
                oauth_params_set( &auth, "access_token", access_token );
        
        g_free( ic->acc->pass );
        ic->acc->pass = oauth_params_string( auth );
        oauth_params_free( &auth );
        
        g_free( jd->oauth2_access_token );
        jd->oauth2_access_token = g_strdup( access_token );
        
        jabber_connect( ic );
}