Hello,
I was trying MITM on a windows application (which talks to a M$ server).
Stunnel was running on my windows xp machine.
windows-client-app -> stunnel server ---> stunnel client --> M$ Server
What I found is that stunnel server sends close notify alert to the
windows client app which causes the client to suspend all further
communication (busted windows-client of course!). I tried setting the
TimeoutClose option to high values but I always saw the server sending
close notify alert (is the timeout close only a client-side parameter?)
Is there a way to configure server to not send close notify?
stullen logs:
2012.11.28 18:32:12 LOG7[3908:5904]: SSL socket closed on SSL_read
2012.11.28 18:32:12 LOG7[3908:5904]: Sent socket write shutdown
2012.11.28 18:32:12 LOG7[3908:4232]: Socket closed on read
2012.11.28 18:32:12 LOG5[3908:5904]: Connection closed: 901 byte(s) sent
to SSL, 38020 byte(s) sent to socket
2012.11.28 18:32:12 LOG7[3908:4232]: Sending close_notify alert
2012.11.28 18:32:12 LOG7[3908:4232]: SSL alert (write): warning: close
notify
2012.11.28 18:32:12 LOG6[3908:4232]: SSL_shutdown successfully sent
close_notify alert
2012.11.28 18:32:12 LOG7[3908:5904]: Remote socket (FD=356) closed
<mailto:stunnel-users@stunnel.org>
I finally ended up making this one line code-change to stop server from
sending close alert that helped my MITM progress.
src/client.c:
if(!(SSL_get_shutdown(c->ssl)&SSL_SENT_SHUTDOWN) &&
!sock_open_rd && !c->sock_ptr) {
s_log(LOG_DEBUG, "BHAKTA - HACK -> Skip Sending
close_notify alert");
*! if(0 && SSL_version(c->ssl)!=SSL2_VERSION) { /* SSLv3,
TLSv1 */*
s_log(LOG_DEBUG, "Sending close_notify alert");
shutdown_wants_write=1;
} else { /* no alerts in SSLv2, including the close_notify
alert */
s_log(LOG_DEBUG, "Closing SSLv2 socket");
if(c->ssl_rfd->is_socket)
shutdown(c->ssl_rfd->fd, SHUT_RD); /* notify the
kernel */
if(c->ssl_wfd->is_socket)
shutdown(c->ssl_wfd->fd, SHUT_WR); /* send TCP FIN */
/* notify the OpenSSL library */
SSL_set_shutdown(c->ssl,
SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN);
}
}
Is there a way to prevent server from sending close notify alert by
means of stunel.conf parameters?
stunnel.conf:
debug = 7
output = stunnel.log
cert = fakecert.pem
key = fakecert.key
options = DONT_INSERT_EMPTY_FRAGMENTS
socket = l:TCP_NODELAY=1
socket = r:TCP_NODELAY=1
[https]
sslVersion = TLSv1
accept = 0.0.0.0:443
connect = 127.0.0.1:446
[https-client]
client = yes
sslVersion = TLSv1
accept = 127.0.0.1:446
connect = 172.24.244.11:443
TIMEOUTclose = 300