[openssl-users] Session Ticket Support in Openssl TLS 1.2

Wed Jun 14 17:36:55 UTC 2017

On Wed, Jun 14, 2017 at 3:43 AM, Matt Caswell <matt at openssl.org> wrote:

>
>
> On 14/06/17 01:38, Salz, Rich via openssl-users wrote:
> > It’s disabled by default.  Servers that want to use server-side session
> > caching have to call an API to turn it on
>
> Err, no, that's not correct. Server side caching is on by default.
> Client side caching is off by default.
>

I am quoting a line from Network Security with OpenSSL book (O'Reilly Media)

"All sessions must have a session ID context. For the server, session
caching is disabled by default unless a call to SSL_CTX_set_session_id_context
is made."

That's why I thought server side session caching is disabled by default.

>
>
> On 14/06/17 02:03, Neetish Pathak wrote:
> > Thanks for your reply Salz. However, I want to know should the session
> > caching be enabled on server side for TLS 1.3 for session resumption.
>
> It should just work by default for TLSv1.3. You don't need to enable
> anything.
>

Yea it worked for previous TLS versions, so everything was inline. But
since with TLS 1.3, I was not observing the same behavior, that's why my
question was for TLS 1.3.

>
> > Also, I need a clarification on how does resumption work in case of
> > session identifiers if server side caching is not enabled
>
> As noted above server side caching is on by default.
>

>
> On 14/06/17 02:33, Neetish Pathak wrote:
> > I need some suggestions on how I can implement session resumption in TLS
> > 1.3. I have implemented the resumption on the client side using a
> > callback as recommended on the TLS 1.3
> > blog https://www.openssl.org/blog/blog/2017/05/04/tlsv1.3/
> > <https://www.openssl.org/blog/blog/2017/05/04/tlsv1.3/> . Still, the
> > session resumption is not working. I know this because my new_session_cb
> > which I have set using SSL_CTX_sess_set_new_cb is never getting invoked
> > and also I don't see any improvement in connection time.
> >
> > The same implementation when I change the max TLS version to TLS1.2
> > works and session resumption works as desired.
> > I am not sure how I can resolve this.
> >
> > As mentioned on the blog post
> >
> > "In TLSv1.3 sessions are not established until after the main handshake
> > has completed. The server sends a separate post-handshake message to the
> > client containing the session details. Typically this will happen soon
> > after the handshake has completed, but it could be sometime later (or
> > not at all)."
> >
> > I think the server is not informing the session details to client at all
> > in my case and hence the resumption is not working. Can someone please
> > suggest how to resolve this
>
> Just to be clear: you are using OpenSSL on both the server and client
> sides right? If you are using something other than OpenSSL on the server
> then the policy might be different around when the session information
> is sent to the client (i.e. it could happen sometime later, or not at
> all). If you are using OpenSSL on the server then it sends its session
> information immediately after the main handshake has completed, so that
> should not be a problem.
>
> So if I understand you correctly the client is successfully creating a
> TLSv1.3 connection, but the client side new session callback is never
> being invoked? Did you call SSL_CTX_sess_set_new_cb() before or after
> the SSL object itself was created? Are you able to share any code for
> how you have done this?
>

Yes, I am using OpenSSl on both the server and client sides and my
implementation works for TLS 1.2.
Yea you understood correctly, the client is creating a connection but new
session callback is not getting invoked.
I have called SSL_CTX_sess_set_new_cb before SSL object is created

Yea, sure following is a snippet from my client side implementation. I have
highlighted the relevant section for new session callback registration

*static* *int* *new_session_cb*(SSL* ssl, SSL_SESSION * sess){

BIO *stmp = BIO_new_file(SESS_OUT,"w");

*if*(stmp == NULL){

BIO_printf(bio_err,"Error writing session file %s\n",SESS_OUT);

}*else*{

fprintf(stderr,"Session getting set\n");

PEM_write_bio_SSL_SESSION(stmp,sess);

BIO_free(stmp);

resumeInput = TRUE;

}

*return* 0;

}

*int* *SocketClient::connectToServer*(){

/*Initialization

** (1)Register SSL/TLS ciphers and digests

** (2)Load Opessl error Strings*/

init_OpenSSL();

/*Creating a new SSL context object*/

ssl_ctx = SSL_CTX_new(TLS_client_method());

SSL_CTX_set_max_proto_version(ssl_ctx, MAX_TLS_VERSION);

SSL_CTX_set_min_proto_version(ssl_ctx, MIN_TLS_VERSION);

*if*(NULL == ssl_ctx){

fail("SocketClient.cpp : ssl_ctx object creation failed"); perror("");

}*else*{

pass("SocketClient.cpp : ssl Context created successfully");

}

*if(ssl_ctx){*

* SSL_CTX_set_session_cache_mode(ssl_ctx, SSL_SESS_CACHE_CLIENT*

* | SSL_SESS_CACHE_NO_INTERNAL_STORE);*

* SSL_CTX_sess_set_new_cb(ssl_ctx, new_session_cb);*

* }*

*return* 0;

}

int *SocketClient::sslTcpConnect*(){

/*Attaching the SSL connection to the Socket*/

*if*((*this*->conn = SSL_new(ssl_ctx)) == NULL){

perror("SocketClient.cpp : create new SSL failed ");

exit(1);

}

/*Try to resume session*/

*#if* SESS_RESUME

*if*(resumeInput){

SSL_SESSION *sess;

BIO *stmp = BIO_new_file(SESS_OUT, "r");

*if* (!stmp) {

BIO_printf(bio_err, "Can't open session file %s\n", SESS_OUT);

ERR_print_errors(bio_err);

}

sess = PEM_read_bio_SSL_SESSION(stmp, NULL, 0, NULL);

BIO_free(stmp);

*if* (!sess) {

BIO_printf(bio_err, "Can't open session file %s\n", SESS_OUT);

ERR_print_errors(bio_err);

}

*if* (!SSL_set_session(*this*->conn, sess)) {

BIO_printf(bio_err, "Can't set session\n");

ERR_print_errors(bio_err);

}

SSL_SESSION_free(sess);

/*if(FALSE == TLSv1_3){

if(this->sessionId != NULL){

SSL_set_session(this->conn, this->sessionId);

SSL_SESSION_free(this->sessionId);

}

}*/

}

/*Another way of resumption*/

/*

if(this->sessionId != NULL){

SSL_set_session(this->conn, this->sessionId);

SSL_SESSION_free(this->sessionId);

}

*/

*#endif*

/****Establish TCP connection****/

/*Setting up BIO*/

bio = BIO_new_connect((*this*->serverName + ":" + *this*->portNumber
).c_str());

*if*(!bio)

int_error("Error creating connection BIO");

*if*(BIO_do_connect(bio) <= 0){

fail("SocketClient.cpp : TCP connection failed");

}*else*{

pass("SocketClient.cpp : TCP connection successful");

}

/*set the file descriptor socket-fd as the input/output facility for the
TLS/SSL*/

SSL_set_bio(conn, bio, bio);

/*Perform the SSL handshake*/

*if*(SSL_connect(conn) != 1){

fail("SocketClient.cpp : SSL connect failed"); perror("");

ERR_print_errors_fp(stderr);

SSL_clear(conn);

exit(1);

}*else*{

*this*->isConnected = *true*;

pass("SocketClient.cpp : SSL_connect successful");

}

*return* 0;

}

*int* *SocketClient::sslTcpClosure*(){

*if* (*this*->conn){

SSL_shutdown(*this*->conn);

}

*if*(*this*->bio)

BIO_free(*this*->bio);

*return* 0;

}

My calling sequence is :

client.connectToServer();

client.sslTcpConnect();

client.sslTcpClosure();

> Matt
>
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>

Thanks
BR,
Neetish
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