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
14 =for openssl 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 SSL BIO B<b> to B<ssl> using
60 BIO_get_ssl() retrieves the SSL pointer of SSL 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 of SSL BIO B<b>
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 of SSL BIO B<b>
73 When the renegotiate timeout elapses the session is automatically renegotiated.
75 BIO_get_num_renegotiates() returns the total number of session
76 renegotiations due to I/O or timeout of SSL BIO B<b>.
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 BIO.
87 BIO_ssl_copy_session_id() copies an SSL session id between
88 BIO chains B<from> and B<to>. It does this by locating the
89 SSL BIOs in each chain and calling SSL_copy_session_id() on
90 the internal SSL pointer.
92 BIO_ssl_shutdown() closes down an SSL connection on BIO
93 chain B<bio>. It does this by locating the SSL BIO in the
94 chain and calling SSL_shutdown() on its internal SSL
97 BIO_do_handshake() attempts to complete an SSL handshake on the
98 supplied BIO and establish the SSL connection.
99 For non-SSL BIOs the connection is done typically at TCP level.
100 If domain name resolution yields multiple IP addresses all of them are tried
101 after connect() failures.
102 The function returns 1 if the connection was established successfully.
103 A zero or negative value is returned if the connection could not be established.
104 The call BIO_should_retry() should be used for nonblocking connect BIOs
105 to determine if the call should be retried.
106 If a connection has already been established this call has no effect.
110 SSL BIOs are exceptional in that if the underlying transport
111 is non blocking they can still request a retry in exceptional
112 circumstances. Specifically this will happen if a session
113 renegotiation takes place during a BIO_read_ex() operation, one
114 case where this happens is when step up occurs.
116 The SSL flag SSL_AUTO_RETRY can be
117 set to disable this behaviour. That is when this flag is set
118 an SSL BIO using a blocking transport will never request a
121 Since unknown BIO_ctrl() operations are sent through filter
122 BIOs the servers name and port can be set using BIO_set_host()
123 on the BIO returned by BIO_new_ssl_connect() without having
124 to locate the connect BIO first.
126 Applications do not have to call BIO_do_handshake() but may wish
127 to do so to separate the handshake process from other I/O
130 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
131 BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
132 BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.
134 BIO_ssl_copy_session_id() is not currently supported on QUIC SSL objects and
135 fails if called on such an object.
139 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
141 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
142 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
143 success or a value which is less than or equal to 0 if an error occurred.
145 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
146 a valid B<BIO> structure on success or B<NULL> if an error occurred.
148 BIO_ssl_copy_session_id() returns 1 on success or 0 on error, or if called
149 on a QUIC SSL object.
151 BIO_do_handshake() returns 1 if the connection was established successfully.
152 A zero or negative value is returned if the connection could not be established.
156 This SSL/TLS client example attempts to retrieve a page from an
157 SSL/TLS web server. The I/O routines are identical to those of the
158 unencrypted example in L<BIO_s_connect(3)>.
166 /* XXX Seed the PRNG if needed. */
168 ctx = SSL_CTX_new(TLS_client_method());
170 /* XXX Set verify paths and mode here. */
172 sbio = BIO_new_ssl_connect(ctx);
173 BIO_get_ssl(sbio, &ssl);
175 fprintf(stderr, "Can't locate SSL pointer\n");
176 ERR_print_errors_fp(stderr);
180 /* XXX We might want to do other things with ssl here */
182 /* An empty host part means the loopback address */
183 BIO_set_conn_hostname(sbio, ":https");
185 out = BIO_new_fp(stdout, BIO_NOCLOSE);
186 if (BIO_do_connect(sbio) <= 0) {
187 fprintf(stderr, "Error connecting to server\n");
188 ERR_print_errors_fp(stderr);
192 /* XXX Could examine ssl here to get connection info */
194 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
196 len = BIO_read(sbio, tmpbuf, 1024);
199 BIO_write(out, tmpbuf, len);
204 Here is a simple server example. It makes use of a buffering
205 BIO to allow lines to be read from the SSL BIO using BIO_gets.
206 It creates a pseudo web page containing the actual request from
207 a client and also echoes the request to standard output.
209 BIO *sbio, *bbio, *acpt, *out;
215 /* XXX Seed the PRNG if needed. */
217 ctx = SSL_CTX_new(TLS_server_method());
218 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
219 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
220 || !SSL_CTX_check_private_key(ctx)) {
221 fprintf(stderr, "Error setting up SSL_CTX\n");
222 ERR_print_errors_fp(stderr);
226 /* XXX Other things like set verify locations, EDH temp callbacks. */
228 /* New SSL BIO setup as server */
229 sbio = BIO_new_ssl(ctx, 0);
230 BIO_get_ssl(sbio, &ssl);
232 fprintf(stderr, "Can't locate SSL pointer\n");
233 ERR_print_errors_fp(stderr);
237 bbio = BIO_new(BIO_f_buffer());
238 sbio = BIO_push(bbio, sbio);
239 acpt = BIO_new_accept("4433");
242 * By doing this when a new connection is established
243 * we automatically have sbio inserted into it. The
244 * BIO chain is now 'swallowed' by the accept BIO and
245 * will be freed when the accept BIO is freed.
247 BIO_set_accept_bios(acpt, sbio);
248 out = BIO_new_fp(stdout, BIO_NOCLOSE);
250 /* First call to BIO_do_accept() sets up accept BIO */
251 if (BIO_do_accept(acpt) <= 0) {
252 fprintf(stderr, "Error setting up accept BIO\n");
253 ERR_print_errors_fp(stderr);
257 /* Second call to BIO_do_accept() waits for incoming connection */
258 if (BIO_do_accept(acpt) <= 0) {
259 fprintf(stderr, "Error accepting connection\n");
260 ERR_print_errors_fp(stderr);
264 /* We only want one connection so remove and free accept BIO */
265 sbio = BIO_pop(acpt);
268 if (BIO_do_handshake(sbio) <= 0) {
269 fprintf(stderr, "Error in SSL handshake\n");
270 ERR_print_errors_fp(stderr);
274 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
275 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
276 BIO_puts(sbio, "--------------------------------------------------\r\n");
279 len = BIO_gets(sbio, tmpbuf, 1024);
282 BIO_write(sbio, tmpbuf, len);
283 BIO_write(out, tmpbuf, len);
284 /* Look for blank line signifying end of headers*/
285 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
289 BIO_puts(sbio, "--------------------------------------------------\r\n");
290 BIO_puts(sbio, "\r\n");
296 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
297 the I/O BIO reference count was incorrectly incremented (instead of
298 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
299 explicitly being popped (e.g. a pop higher up the chain). Applications which
300 included workarounds for this bug (e.g. freeing BIOs more than once) should
301 be modified to handle this fix or they may free up an already freed BIO.
305 Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
307 Licensed under the Apache License 2.0 (the "License"). You may not use
308 this file except in compliance with the License. You can obtain a copy
309 in the file LICENSE in the source distribution or at
310 L<https://www.openssl.org/source/license.html>.