Document session caching, first step.

doc/ssl/SSL_CTX_sess_set_get_cb.pod

+=pod
+
+=head1 NAME
+
+SSL_CTX_sess_set_new_cb, SSL_CTX_sess_set_remove_cb, SSL_CTX_sess_set_get_cb, SSL_CTX_sess_get_new_cb, SSL_CTX_sess_get_remove_cb, SSL_CTX_sess_get_get_cb - provide callback functions for server side external session caching
+
+=head1 SYNOPSIS
+
+ #include <openssl/ssl.h>
+
+ void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
+			      int (*new_session_cb)(SSL *, SSL_SESSION *));
+ void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
+	   void (*remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *));
+ void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
+	   SSL_SESSION (*get_session-cb)(SSL *, unsigned char *, int, int *));
+
+ int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl, SSL_SESSION *sess);
+ void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
+ SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl, unsigned char *data, int len, int *copy);
+
+ int (*new_session_cb)(struct ssl_st *ssl, SSL_SESSION *sess);
+ void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
+ SSL_SESSION *(*get_session_cb)(struct ssl_st *ssl, unsigned char *data,
+	       int len, int *copy);
+
+=head1 DESCRIPTION
+
+SSL_CTX_sess_set_new_cb() sets the callback function, which is automatically
+called whenever a new session was negotiated.
+
+SSL_CTX_sess_set_remove_cb() sets the callback function, which is
+automatically called whenever a session is removed by the SSL engine,
+because it is considered faulty or the session has become obsolete because
+of exceeding the timeout value.
+
+SSL_CTX_sess_set_get_cb() sets the callback function which is called,
+whenever a SSL/TLS client proposed to resume a session but the session
+could not be found in the internal session cache (see
+L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>).
+(SSL/TLS server only.)
+
+SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb(), and
+SSL_CTX_sess_get_get_cb() allow to retrieve the funtion pointers of the
+provided callback functions. If a callback function has not been set,
+the NULL pointer is returned.
+
+=head1 NOTES
+
+In order to allow external session caching, synchronization with the internal
+session cache is realized via callback functions. Inside these callback
+functions, session can be saved to disk or put into a database using the
+L<d2i_SSL_SESSION(3)|d2i_SSL_SESSION(3)> interface.
+
+The new_session_cb() is called, whenever a new session has been negotiated
+and session caching is enabled (see
+L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>).
+The new_session_cb() is passed the B<ssl> connection and the ssl session
+B<sess>. If the callback returns B<0>, the session will be immediatly
+removed again.
+
+The remove_session_cb() is called, whenever the SSL engine removes a session
+from the internal cache. This happens if the session is removed because
+it is expired or when a connection was not shutdown cleanly. The
+remove_session_cb() is passed the B<ctx> and the ssl session B<sess>.
+It does not provide any feedback.
+
+The get_session_cb() is only called on SSL/TLS servers with the session id
+proposed by the client. The get_session_cb() is always called, also when
+session caching was disabled. The get_session_cb() is passed the
+B<ssl> connection, the session id of length B<length> at the memory location
+B<data>. With the parameter B<copy> the callback can require the
+SSL engine to increment the reference count of the SSL_SESSION object.
+
+=head1 SEE ALSO
+
+L<ssl(3)|ssl(3)>, L<d2i_SSL_SESSION(3)|d2i_SSL_SESSION(3)>,
+L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>
+
+=cut

doc/ssl/SSL_CTX_set_session_cache_mode.pod

+=pod
+
+=head1 NAME
+
+SSL_CTX_set_session_cache_mode - enable/disable session caching
+
+=head1 SYNOPSIS
+
+ #include <openssl/ssl.h>
+
+ long SSL_CTX_set_session_cache_mode(SSL_CTX ctx, long mode);
+ long SSL_CTX_get_session_cache_mode(SSL_CTX ctx);
+
+=head1 DESCRIPTION
+
+SSL_CTX_set_session_cache_mode() enables/disables session caching
+by setting the operational mode for B<ctx> to <mode>.
+
+SSL_CTX_get_session_cache_mode() returns the currently used cache mode.
+
+=head1 NOTES
+
+The OpenSSL library can store/retrieve SSL/TLS sessions for later reuse.
+The sessions can be held in memory for each B<ctx>, if more than one
+SSL_CTX object is being maintained, the sessions are unique for each SSL_CTX
+object.
+
+In order to reuse a session, a client must send the session's id to the
+server. It can only send exactly one id.  The server then decides whether it
+agrees in reusing the session or starts the handshake for a new session.
+
+A server will lookup up the session in its internal session storage. If
+the session is not found in internal storage or internal storage is
+deactivated, the server will try the external storage if available.
+
+Since a client may try to reuse a session intended for use in a different
+context, the session id context must be set by the server (see
+L<SSL_CTX_set_session_id_context(3)|SSL_CTX_set_session_id_context(3)>).
+
+The following session cache modes and modifiers are available:
+
+=over 4
+
+=item SSL_SESS_CACHE_OFF
+
+No session caching for client or server takes place.
+
+=item SSL_SESS_CACHE_CLIENT
+
+Client sessions are added to the session cache. As there is no reliable way
+for the OpenSSL library to know whether a session should be reused or which
+session to choose (due to the abstract BIO layer the SSL engine does not
+have details about the connection), the application must select the session
+to be reused by using the L<SSL_set_session(3)|SSL_set_session(3)>
+function. This option is not activated by default.
+
+=item SSL_SESS_CACHE_SERVER
+
+Server sessions are added to the session cache. When a client proposes a
+session to be reused, the session is looked up in the internal session cache.
+If the session is found, the server will try to reuse the session.
+This is the default.
+
+=item SSL_SESS_CACHE_BOTH
+
+Enable both SSL_SESS_CACHE_CLIENT and SSL_SESS_CACHE_SERVER at the same time.
+
+=item SSL_SESS_CACHE_NO_AUTO_CLEAR
+
+Normally the session cache is checked for expired sessions every
+255 connections using the SSL_CTX_flush_sessions() function. Since
+this may lead to a delay which cannot be controlled, the automatic
+flushing may be disabled and SSL_CTX_flush_sessions() can be called
+explicitly by the application.
+
+=item SSL_SESS_CACHE_NO_INTERNAL_LOOKUP
+
+By setting this flag sessions are cached in the internal storage but
+they are not looked up automatically. If an external session cache
+is enabled, sessions are looked up in the external cache. As automatic
+lookup only applies for SSL/TLS servers, the flag has no effect on
+clients.
+
+=back
+
+The default mode is SSL_SESS_CACHE_SERVER.
+
+=head1 RETURN VALUES
+
+SSL_CTX_set_session_cache_mode() returns the previously set cache mode.
+
+SSL_CTX_get_session_cache_mode() returns the currently set cache mode.
+
+
+=head1 SEE ALSO
+
+L<ssl(3)|ssl(3)>, L<SSL_set_session(3)|SSL_set_session(3)>,
+L<SSL_CTX_sess_set_get_cb(3)|SSL_CTX_sess_set_get_cb(3)>,
+L<SSL_CTX_set_session_id_context(3)|SSL_CTX_set_session_id_context(3)>
+
+=cut

doc/ssl/SSL_set_session.pod

@@ -40,6 +40,7 @@ The operation succeeded.
 
 =head1 SEE ALSO
 
-L<ssl(3)|ssl(3)>, L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>
+L<ssl(3)|ssl(3)>, L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>,
+L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>
 
 =cut

doc/ssl/d2i_SSL_SESSION.pod

+=pod
+
+=head1 NAME
+d2i_SSL_SESSION, i2d_SSL_SESSION - convert SSL_SESSION object from/to ASN1 representation
+
+=head1 SYNOPSIS
+
+ #include <openssl/ssl.h>
+
+ SSL_SESSION *d2i_SSL_SESSION(SSL_SESSION **a, unsigned char **pp, long length); int i2d_SSL_SESSION(SSL_SESSION *in, unsigned char **pp);
+
+=head1 DESCRIPTION
+
+d2i_SSL_SESSION() transforms the external ASN1 representation of an SSL/TLS
+session, stored as binary data at location B<pp> with length B<length>, into
+an SSL_SESSION object.
+
+i2d_SSL_SESSION() transforms the SSL_SESSION object B<in> into the ASN1
+representation and stores it into the memory location pointed to by B<pp>.
+The length of the resulting ASN1 representation is returned. If B<pp> is
+the NULL pointer, only the length is calculated and returned.
+
+=head1 NOTES
+
+The SSL_SESSION object is built from several malloc()ed parts, it can
+therefore not be moved, copied or stored directly. In order to store
+session data on disk or into a database, it must be transformed into
+a binary ASN1 representation.
+
+When using d2i_SSL_SESSION(), the SSL_SESSION object is automatically
+allocated.
+
+When using i2d_SSL_SESSION(), the memory location pointed to by B<pp> must be
+large enough to hold the binary representation of the session. There is no
+known limit on the size of the created ASN1 representation, so the necessary
+amount of space should be obtained by first calling i2d_SSL_SESSION() with
+B<pp=NULL>, and obtain the size needed, then allocate the memory and
+call i2d_SSL_SESSION() again.
+
+=head1 RETURN VALUES
+
+d2i_SSL_SESSION() returns a pointer to the newly allocated SSL_SESSION
+object. In case of failure the NULL-pointer is returned and the error message
+can be retrieved from the error stack.
+
+i2d_SSL_SESSION() returns the size of the ASN1 representation in bytes.
+When the session is not valid, B<0> is returned and no operation is performed.
+
+=head1 SEE ALSO
+
+L<ssl(3)|ssl(3)>,
+L<SSL_CTX_sess_set_get_cb(3)|SSL_CTX_sess_set_get_cb(3)>
+
+=cut

doc/ssl/ssl.pod

@@ -655,8 +655,10 @@ L<SSL_CTX_get_ex_new_index(3)|SSL_CTX_get_ex_new_index(3)>,
 L<SSL_CTX_get_verify_mode(3)|SSL_CTX_get_verify_mode(3)>,
 L<SSL_CTX_load_verify_locations(3)|SSL_CTX_load_verify_locations(3)>
 L<SSL_CTX_new(3)|SSL_CTX_new(3)>,
+L<SSL_CTX_sess_set_get_cb(3)|SSL_CTX_sess_set_get_cb(3)>,
 L<SSL_CTX_set_client_CA_list(3)|SSL_CTX_set_client_CA_list(3)>,
 L<SSL_CTX_set_default_passwd_cb(3)|SSL_CTX_set_default_passwd_cb(3)>,
+L<SSL_CTX_set_session_cache_mode(3)|SSL_CTX_set_session_cache_mode(3)>,
 L<SSL_CTX_set_session_id_context(3)|SSL_CTX_set_session_id_context(3)>,
 L<SSL_CTX_set_ssl_version(3)|SSL_CTX_set_ssl_version(3)>,
 L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>,
@@ -679,7 +681,8 @@ L<SSL_set_fd(3)|SSL_set_fd(3)>, L<SSL_pending(3)|SSL_pending(3)>,
 L<SSL_set_session(3)|SSL_set_session(3)>,
 L<SSL_shutdown(3)|SSL_shutdown(3)>, L<SSL_write(3)|SSL_write(3)>,
 L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>,
-L<SSL_SESSION_get_ex_new_index(3)|SSL_SESSION_get_ex_new_index(3)>
+L<SSL_SESSION_get_ex_new_index(3)|SSL_SESSION_get_ex_new_index(3)>,
+L<d2i_SSL_SESSION(3)|d2i_SSL_SESSION(3)>
 
 =head1 HISTORY