Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
BIO_F_SSL(3)			    OpenSSL			  BIO_F_SSL(3)

       BIO_do_handshake, BIO_f_ssl, BIO_set_ssl, BIO_get_ssl,
       BIO_set_ssl_mode, BIO_set_ssl_renegotiate_bytes,
       BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
       BIO_new_ssl_connect, BIO_new_buffer_ssl_connect,
       BIO_ssl_copy_session_id,	BIO_ssl_shutdown - SSL BIO

	#include <openssl/bio.h>
	#include <openssl/ssl.h>

	const BIO_METHOD *BIO_f_ssl(void);

	long BIO_set_ssl(BIO *b, SSL *ssl, long	c);
	long BIO_get_ssl(BIO *b, SSL **sslp);
	long BIO_set_ssl_mode(BIO *b, long client);
	long BIO_set_ssl_renegotiate_bytes(BIO *b, long	num);
	long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
	long BIO_get_num_renegotiates(BIO *b);

	BIO *BIO_new_ssl(SSL_CTX *ctx, int client);
	BIO *BIO_new_ssl_connect(SSL_CTX *ctx);
	BIO *BIO_new_buffer_ssl_connect(SSL_CTX	*ctx);
	int BIO_ssl_copy_session_id(BIO	*to, BIO *from);
	void BIO_ssl_shutdown(BIO *bio);

	long BIO_do_handshake(BIO *b);

       BIO_f_ssl() returns the SSL BIO method. This is a filter	BIO which is a
       wrapper round the OpenSSL SSL routines adding a BIO "flavour" to	SSL

       I/O performed on	an SSL BIO communicates	using the SSL protocol with
       the SSLs	read and write BIOs. If	an SSL connection is not established
       then an attempt is made to establish one	on the first I/O call.

       If a BIO	is appended to an SSL BIO using	BIO_push() it is automatically
       used as the SSL BIOs read and write BIOs.

       Calling BIO_reset() on an SSL BIO closes	down any current SSL
       connection by calling SSL_shutdown(). BIO_reset() is then sent to the
       next BIO	in the chain: this will	typically disconnect the underlying
       transport.  The SSL BIO is then reset to	the initial accept or connect

       If the close flag is set	when an	SSL BIO	is freed then the internal SSL
       structure is also freed using SSL_free().

       BIO_set_ssl() sets the internal SSL pointer of BIO b to ssl using the
       close flag c.

       BIO_get_ssl() retrieves the SSL pointer of BIO b, it can	then be
       manipulated using the standard SSL library functions.

       BIO_set_ssl_mode() sets the SSL BIO mode	to client. If client is	1
       client mode is set. If client is	0 server mode is set.

       BIO_set_ssl_renegotiate_bytes() sets the	renegotiate byte count to num.
       When set	after every num	bytes of I/O (read and write) the SSL session
       is automatically	renegotiated. num must be at least 512 bytes.

       BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout to
       seconds.	When the renegotiate timeout elapses the session is
       automatically renegotiated.

       BIO_get_num_renegotiates() returns the total number of session
       renegotiations due to I/O or timeout.

       BIO_new_ssl() allocates an SSL BIO using	SSL_CTX	ctx and	using client
       mode if client is non zero.

       BIO_new_ssl_connect() creates a new BIO chain consisting	of an SSL BIO
       (using ctx) followed by a connect BIO.

       BIO_new_buffer_ssl_connect() creates a new BIO chain consisting of a
       buffering BIO, an SSL BIO (using	ctx) and a connect BIO.

       BIO_ssl_copy_session_id() copies	an SSL session id between BIO chains
       from and	to. It does this by locating the SSL BIOs in each chain	and
       calling SSL_copy_session_id() on	the internal SSL pointer.

       BIO_ssl_shutdown() closes down an SSL connection	on BIO chain bio. It
       does this by locating the SSL BIO in the	chain and calling
       SSL_shutdown() on its internal SSL pointer.

       BIO_do_handshake() attempts to complete an SSL handshake	on the
       supplied	BIO and	establish the SSL connection. It returns 1 if the
       connection was established successfully.	A zero or negative value is
       returned	if the connection could	not be established, the	call
       BIO_should_retry() should be used for non blocking connect BIOs to
       determine if the	call should be retried.	If an SSL connection has
       already been established	this call has no effect.

       SSL BIOs	are exceptional	in that	if the underlying transport is non
       blocking	they can still request a retry in exceptional circumstances.
       Specifically this will happen if	a session renegotiation	takes place
       during a	BIO_read_ex() operation, one case where	this happens is	when
       step up occurs.

       The SSL flag SSL_AUTO_RETRY can be set to disable this behaviour. That
       is when this flag is set	an SSL BIO using a blocking transport will
       never request a retry.

       Since unknown BIO_ctrl()	operations are sent through filter BIOs	the
       servers name and	port can be set	using BIO_set_host() on	the BIO
       returned	by BIO_new_ssl_connect() without having	to locate the connect
       BIO first.

       Applications do not have	to call	BIO_do_handshake() but may wish	to do
       so to separate the handshake process from other I/O processing.

       BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
       BIO_set_ssl_renegotiate_bytes(),	BIO_set_ssl_renegotiate_timeout(),
       BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as

       BIO_f_ssl() returns the SSL BIO_METHOD structure.

       BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
       BIO_set_ssl_renegotiate_bytes(),	BIO_set_ssl_renegotiate_timeout() and
       BIO_get_num_renegotiates() return 1 on success or a value which is less
       than or equal to	0 if an	error occurred.

       BIO_new_ssl(), BIO_new_ssl_connect() and	BIO_new_buffer_ssl_connect()
       return a	valid BIO structure on success or NULL if an error occurred.

       BIO_ssl_copy_session_id() returns 1 on success or 0 on error.

       BIO_do_handshake() returns 1 if the connection was established
       successfully.  A	zero or	negative value is returned if the connection
       could not be established.

       This SSL/TLS client example attempts to retrieve	a page from an SSL/TLS
       web server. The I/O routines are	identical to those of the unencrypted
       example in BIO_s_connect(3).

	BIO *sbio, *out;
	int len;
	char tmpbuf[1024];
	SSL_CTX	*ctx;
	SSL *ssl;

	/* XXX Seed the	PRNG if	needed.	*/

	ctx = SSL_CTX_new(TLS_client_method());

	/* XXX Set verify paths	and mode here. */

	sbio = BIO_new_ssl_connect(ctx);
	BIO_get_ssl(sbio, &ssl);
	if (ssl	== NULL) {
	    fprintf(stderr, "Can't locate SSL pointer\n");

	/* Don't want any retries */
	SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);

	/* XXX We might	want to	do other things	with ssl here */

	/* An empty host part means the	loopback address */
	BIO_set_conn_hostname(sbio, ":https");

	out = BIO_new_fp(stdout, BIO_NOCLOSE);
	if (BIO_do_connect(sbio) <= 0) {
	    fprintf(stderr, "Error connecting to server\n");
	if (BIO_do_handshake(sbio) <= 0) {
	    fprintf(stderr, "Error establishing	SSL connection\n");

	/* XXX Could examine ssl here to get connection	info */

	BIO_puts(sbio, "GET / HTTP/1.0\n\n");
	for (;;) {
	    len	= BIO_read(sbio, tmpbuf, 1024);
	    if (len <= 0)
	    BIO_write(out, tmpbuf, len);

       Here is a simple	server example.	It makes use of	a buffering BIO	to
       allow lines to be read from the SSL BIO using BIO_gets.	It creates a
       pseudo web page containing the actual request from a client and also
       echoes the request to standard output.

	BIO *sbio, *bbio, *acpt, *out;
	int len;
	char tmpbuf[1024];
	SSL_CTX	*ctx;
	SSL *ssl;

	/* XXX Seed the	PRNG if	needed.	*/

	ctx = SSL_CTX_new(TLS_server_method());
	if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
		|| !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
		|| !SSL_CTX_check_private_key(ctx)) {
	    fprintf(stderr, "Error setting up SSL_CTX\n");

	/* XXX Other things like set verify locations, EDH temp	callbacks. */

	/* New SSL BIO setup as	server */
	sbio = BIO_new_ssl(ctx,	0);
	BIO_get_ssl(sbio, &ssl);
	if (ssl	== NULL) {
	    fprintf(stderr, "Can't locate SSL pointer\n");

	SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
	bbio = BIO_new(BIO_f_buffer());
	sbio = BIO_push(bbio, sbio);
	acpt = BIO_new_accept("4433");

	 * By doing this when a	new connection is established
	 * we automatically have sbio inserted into it.	The
	 * BIO chain is	now 'swallowed'	by the accept BIO and
	 * will	be freed when the accept BIO is	freed.
	BIO_set_accept_bios(acpt, sbio);
	out = BIO_new_fp(stdout, BIO_NOCLOSE);

	/* Setup accept	BIO */
	if (BIO_do_accept(acpt)	<= 0) {
	    fprintf(stderr, "Error setting up accept BIO\n");

	/* We only want	one connection so remove and free accept BIO */
	sbio = BIO_pop(acpt);

	if (BIO_do_handshake(sbio) <= 0) {
	    fprintf(stderr, "Error in SSL handshake\n");

	BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
	BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
	BIO_puts(sbio, "--------------------------------------------------\r\n");

	for (;;) {
	    len	= BIO_gets(sbio, tmpbuf, 1024);
	    if (len <= 0)
	    BIO_write(sbio, tmpbuf, len);
	    BIO_write(out, tmpbuf, len);
	    /* Look for	blank line signifying end of headers*/
	    if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')

	BIO_puts(sbio, "--------------------------------------------------\r\n");
	BIO_puts(sbio, "\r\n");

       In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, the
       I/O BIO reference count was incorrectly incremented (instead of
       decremented) and	dissociated with the SSL BIO even if the SSL BIO was
       not explicitly being popped (e.g. a pop higher up the chain).
       Applications which included workarounds for this	bug (e.g. freeing BIOs
       more than once) should be modified to handle this fix or	they may free
       up an already freed BIO.

       Copyright 2000-2019 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at

1.1.1h				  2020-09-22			  BIO_F_SSL(3)


Want to link to this manual page? Use this URL:

home | help