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  man pages->NetBSD man pages -> BIO_f_ssl (3)              



NAME    [Toc]    [Back]

       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

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

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

        BIO_METHOD *BIO_f_ssl(void);

        #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) \
        #define BIO_set_ssl_renegotiate_timeout(b,seconds) \
        #define BIO_get_num_renegotiates(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);

        #define BIO_do_handshake(b)    BIO_ctrl(b,BIO_C_DO_STATE_MACHINE,0,NULL)

DESCRIPTION    [Toc]    [Back]

       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.

       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 state.

       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

       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

       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.

NOTES    [Toc]    [Back]

       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()
       operation, one case where this happens is when SGC or step
       up occurs.

       In OpenSSL 0.9.6 and later 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_con-
       nect() 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.

RETURN VALUES    [Toc]    [Back]


EXAMPLE    [Toc]    [Back]

       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;


        /* We would seed the PRNG here if the platform didn't
         * do it automatically

        ctx = SSL_CTX_new(SSLv23_client_method());

        /* 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.

        sbio = BIO_new_ssl_connect(ctx);

        BIO_get_ssl(sbio, &ssl);

        if(!ssl) {
          fprintf(stderr, "Can't locate SSL pointer\n");
          /* whatever ... */

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

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

        BIO_set_conn_hostname(sbio, "localhost:https");

        out = BIO_new_fp(stdout, BIO_NOCLOSE);
        if(BIO_do_connect(sbio) <= 0) {
               fprintf(stderr, "Error connecting to server\n");
               /* whatever ... */

        if(BIO_do_handshake(sbio) <= 0) {
               fprintf(stderr, "Error establishing SSL connection\n");
               /* whatever ... */

        /* 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) break;
               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;


        /* Might seed PRNG here */

        ctx = SSL_CTX_new(SSLv23_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");
               return 0;

        /* Might do other things here like setting verify locations and
         * DH and/or RSA temporary key callbacks

        /* New SSL BIO setup as server */

        BIO_get_ssl(sbio, &ssl);

        if(!ssl) {
          fprintf(stderr, "Can't locate SSL pointer\n");
          /* whatever ... */

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

        /* Create the buffering BIO */

        bbio = BIO_new(BIO_f_buffer());

        /* Add to chain */
        sbio = BIO_push(bbio, sbio);


        /* 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.


        out = BIO_new_fp(stdout, BIO_NOCLOSE);

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

        /* Now wait for incoming connection */
        if(BIO_do_accept(acpt) <= 0) {
               fprintf(stderr, "Error in connection\n");
               return 0;

        /* 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");
               return 0;

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

        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] == '\r') || (tmpbuf[0] == '\n')) break;

        BIO_puts(sbio, "--------------------------------------------------\r\n");
        BIO_puts(sbio, "</pre>\r\n");

        /* Since there is a buffering BIO present we had better flush it */


SEE ALSO    [Toc]    [Back]


2001-04-12                    0.9.6g                 BIO_f_ssl(3)
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