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.\" ======================================================================
.\"
.IX Title "BIO_f_ssl 3"
.TH BIO_f_ssl 3 "0.9.7d" "2004-03-17" "OpenSSL"
.UC
.SH "NAME"
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 \- \s-1SSL\s0 \s-1BIO\s0
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& #include <openssl/bio.h>
\& #include <openssl/ssl.h>
.Ve
.Vb 1
\& BIO_METHOD *BIO_f_ssl(void);
.Ve
.Vb 9
\& #define BIO_set_ssl(b,ssl,c)   BIO_ctrl(b,BIO_C_SET_SSL,c,(char *)ssl)
\& #define BIO_get_ssl(b,sslp)    BIO_ctrl(b,BIO_C_GET_SSL,0,(char *)sslp)
\& #define BIO_set_ssl_mode(b,client)     BIO_ctrl(b,BIO_C_SSL_MODE,client,NULL)
\& #define BIO_set_ssl_renegotiate_bytes(b,num) \e
\&        BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_BYTES,num,NULL);
\& #define BIO_set_ssl_renegotiate_timeout(b,seconds) \e
\&        BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_TIMEOUT,seconds,NULL);
\& #define BIO_get_num_renegotiates(b) \e
\&        BIO_ctrl(b,BIO_C_SET_SSL_NUM_RENEGOTIATES,0,NULL);
.Ve
.Vb 5
\& 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);
.Ve
.Vb 1
\& #define BIO_do_handshake(b)    BIO_ctrl(b,BIO_C_DO_STATE_MACHINE,0,NULL)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIBIO_f_ssl()\fR returns the \s-1SSL\s0 \s-1BIO\s0 method. This is a filter \s-1BIO\s0 which
is a wrapper round the OpenSSL \s-1SSL\s0 routines adding a \s-1BIO\s0 \*(L"flavour\*(R" to
\&\s-1SSL\s0 I/O. 
.PP
I/O performed on an \s-1SSL\s0 \s-1BIO\s0 communicates using the \s-1SSL\s0 protocol with
the SSLs read and write BIOs. If an \s-1SSL\s0 connection is not established
then an attempt is made to establish one on the first I/O call.
.PP
If a \s-1BIO\s0 is appended to an \s-1SSL\s0 \s-1BIO\s0 using \fIBIO_push()\fR it is automatically
used as the \s-1SSL\s0 BIOs read and write BIOs.
.PP
Calling \fIBIO_reset()\fR on an \s-1SSL\s0 \s-1BIO\s0 closes down any current \s-1SSL\s0 connection
by calling \fISSL_shutdown()\fR. \fIBIO_reset()\fR is then sent to the next \s-1BIO\s0 in
the chain: this will typically disconnect the underlying transport.
The \s-1SSL\s0 \s-1BIO\s0 is then reset to the initial accept or connect state.
.PP
If the close flag is set when an \s-1SSL\s0 \s-1BIO\s0 is freed then the internal
\&\s-1SSL\s0 structure is also freed using \fISSL_free()\fR.
.PP
\&\fIBIO_set_ssl()\fR sets the internal \s-1SSL\s0 pointer of \s-1BIO\s0 \fBb\fR to \fBssl\fR using
the close flag \fBc\fR.
.PP
\&\fIBIO_get_ssl()\fR retrieves the \s-1SSL\s0 pointer of \s-1BIO\s0 \fBb\fR, it can then be
manipulated using the standard \s-1SSL\s0 library functions.
.PP
\&\fIBIO_set_ssl_mode()\fR sets the \s-1SSL\s0 \s-1BIO\s0 mode to \fBclient\fR. If \fBclient\fR
is 1 client mode is set. If \fBclient\fR is 0 server mode is set.
.PP
\&\fIBIO_set_ssl_renegotiate_bytes()\fR sets the renegotiate byte count
to \fBnum\fR. When set after every \fBnum\fR bytes of I/O (read and write) 
the \s-1SSL\s0 session is automatically renegotiated. \fBnum\fR must be at
least 512 bytes.
.PP
\&\fIBIO_set_ssl_renegotiate_timeout()\fR sets the renegotiate timeout to
\&\fBseconds\fR. When the renegotiate timeout elapses the session is
automatically renegotiated.
.PP
\&\fIBIO_get_num_renegotiates()\fR returns the total number of session
renegotiations due to I/O or timeout.
.PP
\&\fIBIO_new_ssl()\fR allocates an \s-1SSL\s0 \s-1BIO\s0 using \s-1SSL_CTX\s0 \fBctx\fR and using
client mode if \fBclient\fR is non zero.
.PP
\&\fIBIO_new_ssl_connect()\fR creates a new \s-1BIO\s0 chain consisting of an
\&\s-1SSL\s0 \s-1BIO\s0 (using \fBctx\fR) followed by a connect \s-1BIO\s0.
.PP
\&\fIBIO_new_buffer_ssl_connect()\fR creates a new \s-1BIO\s0 chain consisting
of a buffering \s-1BIO\s0, an \s-1SSL\s0 \s-1BIO\s0 (using \fBctx\fR) and a connect
\&\s-1BIO\s0.
.PP
\&\fIBIO_ssl_copy_session_id()\fR copies an \s-1SSL\s0 session id between 
\&\s-1BIO\s0 chains \fBfrom\fR and \fBto\fR. It does this by locating the
\&\s-1SSL\s0 BIOs in each chain and calling \fISSL_copy_session_id()\fR on
the internal \s-1SSL\s0 pointer.
.PP
\&\fIBIO_ssl_shutdown()\fR closes down an \s-1SSL\s0 connection on \s-1BIO\s0
chain \fBbio\fR. It does this by locating the \s-1SSL\s0 \s-1BIO\s0 in the
chain and calling \fISSL_shutdown()\fR on its internal \s-1SSL\s0
pointer.
.PP
\&\fIBIO_do_handshake()\fR attempts to complete an \s-1SSL\s0 handshake on the
supplied \s-1BIO\s0 and establish the \s-1SSL\s0 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 \fIBIO_should_retry()\fR should be used for non blocking connect BIOs
to determine if the call should be retried. If an \s-1SSL\s0 connection has
already been established this call has no effect.
.SH "NOTES"
.IX Header "NOTES"
\&\s-1SSL\s0 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 \fIBIO_read()\fR operation, one
case where this happens is when \s-1SGC\s0 or step up occurs.
.PP
In OpenSSL 0.9.6 and later the \s-1SSL\s0 flag \s-1SSL_AUTO_RETRY\s0 can be
set to disable this behaviour. That is when this flag is set
an \s-1SSL\s0 \s-1BIO\s0 using a blocking transport will never request a
retry.
.PP
Since unknown \fIBIO_ctrl()\fR operations are sent through filter
BIOs the servers name and port can be set using \fIBIO_set_host()\fR
on the \s-1BIO\s0 returned by \fIBIO_new_ssl_connect()\fR without having
to locate the connect \s-1BIO\s0 first.
.PP
Applications do not have to call \fIBIO_do_handshake()\fR but may wish
to do so to separate the handshake process from other I/O
processing.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\s-1TBA\s0
.SH "EXAMPLE"
.IX Header "EXAMPLE"
This \s-1SSL/TLS\s0 client example, attempts to retrieve a page from an
\&\s-1SSL/TLS\s0 web server. The I/O routines are identical to those of the
unencrypted example in BIO_s_connect(3).
.PP
.Vb 5
\& BIO *sbio, *out;
\& int len;
\& char tmpbuf[1024];
\& SSL_CTX *ctx;
\& SSL *ssl;
.Ve
.Vb 3
\& ERR_load_crypto_strings();
\& ERR_load_SSL_strings();
\& OpenSSL_add_all_algorithms();
.Ve
.Vb 3
\& /* We would seed the PRNG here if the platform didn't
\&  * do it automatically
\&  */
.Ve
.Vb 1
\& ctx = SSL_CTX_new(SSLv23_client_method());
.Ve
.Vb 4
\& /* We'd normally set some stuff like the verify paths and
\&  * mode here because as things stand this will connect to
\&  * any server whose certificate is signed by any CA.
\&  */
.Ve
.Vb 1
\& sbio = BIO_new_ssl_connect(ctx);
.Ve
.Vb 1
\& BIO_get_ssl(sbio, &ssl);
.Ve
.Vb 4
\& if(!ssl) {
\&   fprintf(stderr, "Can't locate SSL pointer\en");
\&   /* whatever ... */
\& }
.Ve
.Vb 2
\& /* Don't want any retries */
\& SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
.Ve
.Vb 1
\& /* We might want to do other things with ssl here */
.Ve
.Vb 1
\& BIO_set_conn_hostname(sbio, "localhost:https");
.Ve
.Vb 6
\& out = BIO_new_fp(stdout, BIO_NOCLOSE);
\& if(BIO_do_connect(sbio) <= 0) {
\&        fprintf(stderr, "Error connecting to server\en");
\&        ERR_print_errors_fp(stderr);
\&        /* whatever ... */
\& }
.Ve
.Vb 5
\& if(BIO_do_handshake(sbio) <= 0) {
\&        fprintf(stderr, "Error establishing SSL connection\en");
\&        ERR_print_errors_fp(stderr);
\&        /* whatever ... */
\& }
.Ve
.Vb 1
\& /* Could examine ssl here to get connection info */
.Ve
.Vb 8
\& BIO_puts(sbio, "GET / HTTP/1.0\en\en");
\& for(;;) {      
\&        len = BIO_read(sbio, tmpbuf, 1024);
\&        if(len <= 0) break;
\&        BIO_write(out, tmpbuf, len);
\& }
\& BIO_free_all(sbio);
\& BIO_free(out);
.Ve
Here is a simple server example. It makes use of a buffering
\&\s-1BIO\s0 to allow lines to be read from the \s-1SSL\s0 \s-1BIO\s0 using BIO_gets.
It creates a pseudo web page containing the actual request from
a client and also echoes the request to standard output.
.PP
.Vb 5
\& BIO *sbio, *bbio, *acpt, *out;
\& int len;
\& char tmpbuf[1024];
\& SSL_CTX *ctx;
\& SSL *ssl;
.Ve
.Vb 3
\& ERR_load_crypto_strings();
\& ERR_load_SSL_strings();
\& OpenSSL_add_all_algorithms();
.Ve
.Vb 1
\& /* Might seed PRNG here */
.Ve
.Vb 1
\& ctx = SSL_CTX_new(SSLv23_server_method());
.Ve
.Vb 3
\& 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)) {
.Ve
.Vb 4
\&        fprintf(stderr, "Error setting up SSL_CTX\en");
\&        ERR_print_errors_fp(stderr);
\&        return 0;
\& }
.Ve
.Vb 3
\& /* Might do other things here like setting verify locations and
\&  * DH and/or RSA temporary key callbacks
\&  */
.Ve
.Vb 2
\& /* New SSL BIO setup as server */
\& sbio=BIO_new_ssl(ctx,0);
.Ve
.Vb 1
\& BIO_get_ssl(sbio, &ssl);
.Ve
.Vb 4
\& if(!ssl) {
\&   fprintf(stderr, "Can't locate SSL pointer\en");
\&   /* whatever ... */
\& }
.Ve
.Vb 2
\& /* Don't want any retries */
\& SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
.Ve
.Vb 1
\& /* Create the buffering BIO */
.Ve
.Vb 1
\& bbio = BIO_new(BIO_f_buffer());
.Ve
.Vb 2
\& /* Add to chain */
\& sbio = BIO_push(bbio, sbio);
.Ve
.Vb 1
\& acpt=BIO_new_accept("4433");
.Ve
.Vb 5
\& /* 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. 
\&  */
.Ve
.Vb 1
\& BIO_set_accept_bios(acpt,sbio);
.Ve
.Vb 1
\& out = BIO_new_fp(stdout, BIO_NOCLOSE);
.Ve
.Vb 6
\& /* Setup accept BIO */
\& if(BIO_do_accept(acpt) <= 0) {
\&        fprintf(stderr, "Error setting up accept BIO\en");
\&        ERR_print_errors_fp(stderr);
\&        return 0;
\& }
.Ve
.Vb 6
\& /* Now wait for incoming connection */
\& if(BIO_do_accept(acpt) <= 0) {
\&        fprintf(stderr, "Error in connection\en");
\&        ERR_print_errors_fp(stderr);
\&        return 0;
\& }
.Ve
.Vb 3
\& /* We only want one connection so remove and free
\&  * accept BIO
\&  */
.Ve
.Vb 1
\& sbio = BIO_pop(acpt);
.Ve
.Vb 1
\& BIO_free_all(acpt);
.Ve
.Vb 5
\& if(BIO_do_handshake(sbio) <= 0) {
\&        fprintf(stderr, "Error in SSL handshake\en");
\&        ERR_print_errors_fp(stderr);
\&        return 0;
\& }
.Ve
.Vb 3
\& BIO_puts(sbio, "HTTP/1.0 200 OK\er\enContent-type: text/plain\er\en\er\en");
\& BIO_puts(sbio, "\er\enConnection Established\er\enRequest headers:\er\en");
\& BIO_puts(sbio, "--------------------------------------------------\er\en");
.Ve
.Vb 8
\& for(;;) {
\&        len = BIO_gets(sbio, tmpbuf, 1024);
\&        if(len <= 0) break;
\&        BIO_write(sbio, tmpbuf, len);
\&        BIO_write(out, tmpbuf, len);
\&        /* Look for blank line signifying end of headers*/
\&        if((tmpbuf[0] == '\er') || (tmpbuf[0] == '\en')) break;
\& }
.Ve
.Vb 2
\& BIO_puts(sbio, "--------------------------------------------------\er\en");
\& BIO_puts(sbio, "\er\en");
.Ve
.Vb 2
\& /* Since there is a buffering BIO present we had better flush it */
\& BIO_flush(sbio);
.Ve
.Vb 1
\& BIO_free_all(sbio);
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1TBA\s0