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 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.
100 For non-SSL BIOs the connection is done typically at TCP level.
101 If domain name resolution yields multiple IP addresses all of them are tried
102 after connect() failures.
103 The function returns 1 if the connection was established successfully.
104 A zero or negative value is returned if the connection could not be established.
105 The call BIO_should_retry() should be used for non-blocking connect BIOs
106 to determine if the call should be retried.
107 If a connection has already been established this call has no effect.
111 SSL BIOs are exceptional in that if the underlying transport
112 is non blocking they can still request a retry in exceptional
113 circumstances. Specifically this will happen if a session
114 renegotiation takes place during a BIO_read_ex() operation, one
115 case where this happens is when step up occurs.
117 The SSL flag SSL_AUTO_RETRY can be
118 set to disable this behaviour. That is when this flag is set
119 an SSL BIO using a blocking transport will never request a
122 Since unknown BIO_ctrl() operations are sent through filter
123 BIOs the servers name and port can be set using BIO_set_host()
124 on the BIO returned by BIO_new_ssl_connect() without having
125 to locate the connect BIO first.
127 Applications do not have to call BIO_do_handshake() but may wish
128 to do so to separate the handshake process from other I/O
131 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
132 BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
133 BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.
137 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
139 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
140 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
141 success or a value which is less than or equal to 0 if an error occurred.
143 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
144 a valid B<BIO> structure on success or B<NULL> if an error occurred.
146 BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
148 BIO_do_handshake() returns 1 if the connection was established successfully.
149 A zero or negative value is returned if the connection could not be established.
153 This SSL/TLS client example attempts to retrieve a page from an
154 SSL/TLS web server. The I/O routines are identical to those of the
155 unencrypted example in L<BIO_s_connect(3)>.
163 /* XXX Seed the PRNG if needed. */
165 ctx = SSL_CTX_new(TLS_client_method());
167 /* XXX Set verify paths and mode here. */
169 sbio = BIO_new_ssl_connect(ctx);
170 BIO_get_ssl(sbio, &ssl);
172 fprintf(stderr, "Can't locate SSL pointer\n");
173 ERR_print_errors_fp(stderr);
177 /* Don't want any retries */
178 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
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);
191 if (BIO_do_handshake(sbio) <= 0) {
192 fprintf(stderr, "Error establishing SSL connection\n");
193 ERR_print_errors_fp(stderr);
197 /* XXX Could examine ssl here to get connection info */
199 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
201 len = BIO_read(sbio, tmpbuf, 1024);
204 BIO_write(out, tmpbuf, len);
209 Here is a simple server example. It makes use of a buffering
210 BIO to allow lines to be read from the SSL BIO using BIO_gets.
211 It creates a pseudo web page containing the actual request from
212 a client and also echoes the request to standard output.
214 BIO *sbio, *bbio, *acpt, *out;
220 /* XXX Seed the PRNG if needed. */
222 ctx = SSL_CTX_new(TLS_server_method());
223 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
224 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
225 || !SSL_CTX_check_private_key(ctx)) {
226 fprintf(stderr, "Error setting up SSL_CTX\n");
227 ERR_print_errors_fp(stderr);
231 /* XXX Other things like set verify locations, EDH temp callbacks. */
233 /* New SSL BIO setup as server */
234 sbio = BIO_new_ssl(ctx, 0);
235 BIO_get_ssl(sbio, &ssl);
237 fprintf(stderr, "Can't locate SSL pointer\n");
238 ERR_print_errors_fp(stderr);
242 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
243 bbio = BIO_new(BIO_f_buffer());
244 sbio = BIO_push(bbio, sbio);
245 acpt = BIO_new_accept("4433");
248 * By doing this when a new connection is established
249 * we automatically have sbio inserted into it. The
250 * BIO chain is now 'swallowed' by the accept BIO and
251 * will be freed when the accept BIO is freed.
253 BIO_set_accept_bios(acpt, sbio);
254 out = BIO_new_fp(stdout, BIO_NOCLOSE);
256 /* Setup accept BIO */
257 if (BIO_do_accept(acpt) <= 0) {
258 fprintf(stderr, "Error setting up accept BIO\n");
259 ERR_print_errors_fp(stderr);
263 /* We only want one connection so remove and free accept BIO */
264 sbio = BIO_pop(acpt);
267 if (BIO_do_handshake(sbio) <= 0) {
268 fprintf(stderr, "Error in SSL handshake\n");
269 ERR_print_errors_fp(stderr);
273 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
274 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
275 BIO_puts(sbio, "--------------------------------------------------\r\n");
278 len = BIO_gets(sbio, tmpbuf, 1024);
281 BIO_write(sbio, tmpbuf, len);
282 BIO_write(out, tmpbuf, len);
283 /* Look for blank line signifying end of headers*/
284 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
288 BIO_puts(sbio, "--------------------------------------------------\r\n");
289 BIO_puts(sbio, "\r\n");
295 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
296 the I/O BIO reference count was incorrectly incremented (instead of
297 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
298 explicitly being popped (e.g. a pop higher up the chain). Applications which
299 included workarounds for this bug (e.g. freeing BIOs more than once) should
300 be modified to handle this fix or they may free up an already freed BIO.
304 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
306 Licensed under the Apache License 2.0 (the "License"). You may not use
307 this file except in compliance with the License. You can obtain a copy
308 in the file LICENSE in the source distribution or at
309 L<https://www.openssl.org/source/license.html>.