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.
136 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
138 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
139 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
140 success or a value which is less than or equal to 0 if an error occurred.
142 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
143 a valid B<BIO> structure on success or B<NULL> if an error occurred.
145 BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
147 BIO_do_handshake() returns 1 if the connection was established successfully.
148 A zero or negative value is returned if the connection could not be established.
152 This SSL/TLS client example attempts to retrieve a page from an
153 SSL/TLS web server. The I/O routines are identical to those of the
154 unencrypted example in L<BIO_s_connect(3)>.
162 /* XXX Seed the PRNG if needed. */
164 ctx = SSL_CTX_new(TLS_client_method());
166 /* XXX Set verify paths and mode here. */
168 sbio = BIO_new_ssl_connect(ctx);
169 BIO_get_ssl(sbio, &ssl);
171 fprintf(stderr, "Can't locate SSL pointer\n");
172 ERR_print_errors_fp(stderr);
176 /* XXX We might want to do other things with ssl here */
178 /* An empty host part means the loopback address */
179 BIO_set_conn_hostname(sbio, ":https");
181 out = BIO_new_fp(stdout, BIO_NOCLOSE);
182 if (BIO_do_connect(sbio) <= 0) {
183 fprintf(stderr, "Error connecting to server\n");
184 ERR_print_errors_fp(stderr);
188 /* XXX Could examine ssl here to get connection info */
190 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
192 len = BIO_read(sbio, tmpbuf, 1024);
195 BIO_write(out, tmpbuf, len);
200 Here is a simple server example. It makes use of a buffering
201 BIO to allow lines to be read from the SSL BIO using BIO_gets.
202 It creates a pseudo web page containing the actual request from
203 a client and also echoes the request to standard output.
205 BIO *sbio, *bbio, *acpt, *out;
211 /* XXX Seed the PRNG if needed. */
213 ctx = SSL_CTX_new(TLS_server_method());
214 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
215 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
216 || !SSL_CTX_check_private_key(ctx)) {
217 fprintf(stderr, "Error setting up SSL_CTX\n");
218 ERR_print_errors_fp(stderr);
222 /* XXX Other things like set verify locations, EDH temp callbacks. */
224 /* New SSL BIO setup as server */
225 sbio = BIO_new_ssl(ctx, 0);
226 BIO_get_ssl(sbio, &ssl);
228 fprintf(stderr, "Can't locate SSL pointer\n");
229 ERR_print_errors_fp(stderr);
233 bbio = BIO_new(BIO_f_buffer());
234 sbio = BIO_push(bbio, sbio);
235 acpt = BIO_new_accept("4433");
238 * By doing this when a new connection is established
239 * we automatically have sbio inserted into it. The
240 * BIO chain is now 'swallowed' by the accept BIO and
241 * will be freed when the accept BIO is freed.
243 BIO_set_accept_bios(acpt, sbio);
244 out = BIO_new_fp(stdout, BIO_NOCLOSE);
246 /* Setup accept BIO */
247 if (BIO_do_accept(acpt) <= 0) {
248 fprintf(stderr, "Error setting up accept BIO\n");
249 ERR_print_errors_fp(stderr);
253 /* We only want one connection so remove and free accept BIO */
254 sbio = BIO_pop(acpt);
257 if (BIO_do_handshake(sbio) <= 0) {
258 fprintf(stderr, "Error in SSL handshake\n");
259 ERR_print_errors_fp(stderr);
263 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
264 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
265 BIO_puts(sbio, "--------------------------------------------------\r\n");
268 len = BIO_gets(sbio, tmpbuf, 1024);
271 BIO_write(sbio, tmpbuf, len);
272 BIO_write(out, tmpbuf, len);
273 /* Look for blank line signifying end of headers*/
274 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
278 BIO_puts(sbio, "--------------------------------------------------\r\n");
279 BIO_puts(sbio, "\r\n");
285 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
286 the I/O BIO reference count was incorrectly incremented (instead of
287 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
288 explicitly being popped (e.g. a pop higher up the chain). Applications which
289 included workarounds for this bug (e.g. freeing BIOs more than once) should
290 be modified to handle this fix or they may free up an already freed BIO.
294 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
296 Licensed under the Apache License 2.0 (the "License"). You may not use
297 this file except in compliance with the License. You can obtain a copy
298 in the file LICENSE in the source distribution or at
299 L<https://www.openssl.org/source/license.html>.