6 BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode,
7 BIO_set_ssl_renegotiate_bytes,
8 BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
9 BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id,
10 BIO_ssl_shutdown - SSL BIO
12 =for comment multiple includes
16 #include <openssl/bio.h>
17 #include <openssl/ssl.h>
19 const BIO_METHOD *BIO_f_ssl(void);
21 long BIO_set_ssl(BIO *b, SSL *ssl, long c);
22 long BIO_get_ssl(BIO *b, SSL **sslp);
23 long BIO_set_ssl_mode(BIO *b, long client);
24 long BIO_set_ssl_renegotiate_bytes(BIO *b, long num);
25 long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
26 long BIO_get_num_renegotiates(BIO *b);
28 BIO *BIO_new_ssl(SSL_CTX *ctx, int client);
29 BIO *BIO_new_ssl_connect(SSL_CTX *ctx);
30 BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx);
31 int BIO_ssl_copy_session_id(BIO *to, BIO *from);
32 void BIO_ssl_shutdown(BIO *bio);
34 long BIO_do_handshake(BIO *b);
38 BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which
39 is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to
42 I/O performed on an SSL BIO communicates using the SSL protocol with
43 the SSLs read and write BIOs. If an SSL connection is not established
44 then an attempt is made to establish one on the first I/O call.
46 If a BIO is appended to an SSL BIO using BIO_push() it is automatically
47 used as the SSL BIOs read and write BIOs.
49 Calling BIO_reset() on an SSL BIO closes down any current SSL connection
50 by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in
51 the chain: this will typically disconnect the underlying transport.
52 The SSL BIO is then reset to the initial accept or connect state.
54 If the close flag is set when an SSL BIO is freed then the internal
55 SSL structure is also freed using SSL_free().
57 BIO_set_ssl() sets the internal SSL pointer of BIO B<b> to B<ssl> using
60 BIO_get_ssl() retrieves the SSL pointer of BIO B<b>, it can then be
61 manipulated using the standard SSL library functions.
63 BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client>
64 is 1 client mode is set. If B<client> is 0 server mode is set.
66 BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count
67 to B<num>. When set after every B<num> bytes of I/O (read and write)
68 the SSL session is automatically renegotiated. B<num> must be at
71 BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout to
72 B<seconds>. When the renegotiate timeout elapses the session is
73 automatically renegotiated.
75 BIO_get_num_renegotiates() returns the total number of session
76 renegotiations due to I/O or timeout.
78 BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using
79 client mode if B<client> is non zero.
81 BIO_new_ssl_connect() creates a new BIO chain consisting of an
82 SSL BIO (using B<ctx>) followed by a connect BIO.
84 BIO_new_buffer_ssl_connect() creates a new BIO chain consisting
85 of a buffering BIO, an SSL BIO (using B<ctx>) and a connect
88 BIO_ssl_copy_session_id() copies an SSL session id between
89 BIO chains B<from> and B<to>. It does this by locating the
90 SSL BIOs in each chain and calling SSL_copy_session_id() on
91 the internal SSL pointer.
93 BIO_ssl_shutdown() closes down an SSL connection on BIO
94 chain B<bio>. It does this by locating the SSL BIO in the
95 chain and calling SSL_shutdown() on its internal SSL
98 BIO_do_handshake() attempts to complete an SSL handshake on the
99 supplied BIO and establish the SSL connection. It returns 1
100 if the connection was established successfully. A zero or negative
101 value is returned if the connection could not be established, the
102 call BIO_should_retry() should be used for non blocking connect BIOs
103 to determine if the call should be retried. If an SSL connection has
104 already been established this call has no effect.
108 SSL BIOs are exceptional in that if the underlying transport
109 is non blocking they can still request a retry in exceptional
110 circumstances. Specifically this will happen if a session
111 renegotiation takes place during a BIO_read() operation, one
112 case where this happens is when step up occurs.
114 The SSL flag SSL_AUTO_RETRY can be
115 set to disable this behaviour. That is when this flag is set
116 an SSL BIO using a blocking transport will never request a
119 Since unknown BIO_ctrl() operations are sent through filter
120 BIOs the servers name and port can be set using BIO_set_host()
121 on the BIO returned by BIO_new_ssl_connect() without having
122 to locate the connect BIO first.
124 Applications do not have to call BIO_do_handshake() but may wish
125 to do so to separate the handshake process from other I/O
128 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
129 BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
130 BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.
134 This SSL/TLS client example, attempts to retrieve a page from an
135 SSL/TLS web server. The I/O routines are identical to those of the
136 unencrypted example in L<BIO_s_connect(3)>.
144 /* XXX Seed the PRNG if needed. */
146 ctx = SSL_CTX_new(TLS_client_method());
148 /* XXX Set verify paths and mode here. */
150 sbio = BIO_new_ssl_connect(ctx);
151 BIO_get_ssl(sbio, &ssl);
153 fprintf(stderr, "Can't locate SSL pointer\n");
154 ERR_print_errors_fp(stderr);
158 /* Don't want any retries */
159 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
161 /* XXX We might want to do other things with ssl here */
163 /* An empty host part means the loopback address */
164 BIO_set_conn_hostname(sbio, ":https");
166 out = BIO_new_fp(stdout, BIO_NOCLOSE);
167 if (BIO_do_connect(sbio) <= 0) {
168 fprintf(stderr, "Error connecting to server\n");
169 ERR_print_errors_fp(stderr);
172 if (BIO_do_handshake(sbio) <= 0) {
173 fprintf(stderr, "Error establishing SSL connection\n");
174 ERR_print_errors_fp(stderr);
178 /* XXX Could examine ssl here to get connection info */
180 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
182 len = BIO_read(sbio, tmpbuf, 1024);
185 BIO_write(out, tmpbuf, len);
190 Here is a simple server example. It makes use of a buffering
191 BIO to allow lines to be read from the SSL BIO using BIO_gets.
192 It creates a pseudo web page containing the actual request from
193 a client and also echoes the request to standard output.
195 BIO *sbio, *bbio, *acpt, *out;
201 /* XXX Seed the PRNG if needed. */
203 ctx = SSL_CTX_new(TLS_server_method());
204 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
205 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
206 || !SSL_CTX_check_private_key(ctx)) {
207 fprintf(stderr, "Error setting up SSL_CTX\n");
208 ERR_print_errors_fp(stderr);
212 /* XXX Other things like set verify locations, EDH temp callbacks. */
214 /* New SSL BIO setup as server */
215 sbio = BIO_new_ssl(ctx, 0);
216 BIO_get_ssl(sbio, &ssl);
218 fprintf(stderr, "Can't locate SSL pointer\n");
219 ERR_print_errors_fp(stderr);
223 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
224 bbio = BIO_new(BIO_f_buffer());
225 sbio = BIO_push(bbio, sbio);
226 acpt = BIO_new_accept("4433");
229 * By doing this when a new connection is established
230 * we automatically have sbio inserted into it. The
231 * BIO chain is now 'swallowed' by the accept BIO and
232 * will be freed when the accept BIO is freed.
234 BIO_set_accept_bios(acpt, sbio);
235 out = BIO_new_fp(stdout, BIO_NOCLOSE);
237 /* Setup accept BIO */
238 if (BIO_do_accept(acpt) <= 0) {
239 fprintf(stderr, "Error setting up accept BIO\n");
240 ERR_print_errors_fp(stderr);
244 if (BIO_do_accept(acpt) <= 0) {
245 fprintf(stderr, "Error in connection\n");
246 ERR_print_errors_fp(stderr);
250 /* We only want one connection so remove and free accept BIO */
251 sbio = BIO_pop(acpt);
254 if (BIO_do_handshake(sbio) <= 0) {
255 fprintf(stderr, "Error in SSL handshake\n");
256 ERR_print_errors_fp(stderr);
260 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
261 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
262 BIO_puts(sbio, "--------------------------------------------------\r\n");
265 len = BIO_gets(sbio, tmpbuf, 1024);
268 BIO_write(sbio, tmpbuf, len);
269 BIO_write(out, tmpbuf, len);
270 /* Look for blank line signifying end of headers*/
271 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
275 BIO_puts(sbio, "--------------------------------------------------\r\n");
276 BIO_puts(sbio, "\r\n");
282 In OpenSSL versions before 1.0.0 the BIO_pop() call was handled incorrectly,
283 the I/O BIO reference count was incorrectly incremented (instead of
284 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
285 explicitly being popped (e.g. a pop higher up the chain). Applications which
286 included workarounds for this bug (e.g. freeing BIOs more than once) should
287 be modified to handle this fix or they may free up an already freed BIO.
291 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
293 Licensed under the OpenSSL license (the "License"). You may not use
294 this file except in compliance with the License. You can obtain a copy
295 in the file LICENSE in the source distribution or at
296 L<https://www.openssl.org/source/license.html>.