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 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_ex() 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 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
136 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
137 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
138 success or a value which is less than or equal to 0 if an error occurred.
140 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
141 a valid B<BIO> structure on success or B<NULL> if an error occurred.
143 BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
145 BIO_do_handshake() returns 1 if the connection was established successfully.
146 A zero or negative value is returned if the connection could not be established.
150 This SSL/TLS client example attempts to retrieve a page from an
151 SSL/TLS web server. The I/O routines are identical to those of the
152 unencrypted example in L<BIO_s_connect(3)>.
160 /* XXX Seed the PRNG if needed. */
162 ctx = SSL_CTX_new(TLS_client_method());
164 /* XXX Set verify paths and mode here. */
166 sbio = BIO_new_ssl_connect(ctx);
167 BIO_get_ssl(sbio, &ssl);
169 fprintf(stderr, "Can't locate SSL pointer\n");
170 ERR_print_errors_fp(stderr);
174 /* Don't want any retries */
175 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
177 /* XXX We might want to do other things with ssl here */
179 /* An empty host part means the loopback address */
180 BIO_set_conn_hostname(sbio, ":https");
182 out = BIO_new_fp(stdout, BIO_NOCLOSE);
183 if (BIO_do_connect(sbio) <= 0) {
184 fprintf(stderr, "Error connecting to server\n");
185 ERR_print_errors_fp(stderr);
189 /* XXX Could examine ssl here to get connection info */
191 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
193 len = BIO_read(sbio, tmpbuf, 1024);
196 BIO_write(out, tmpbuf, len);
201 Here is a simple server example. It makes use of a buffering
202 BIO to allow lines to be read from the SSL BIO using BIO_gets.
203 It creates a pseudo web page containing the actual request from
204 a client and also echoes the request to standard output.
206 BIO *sbio, *bbio, *acpt, *out;
212 /* XXX Seed the PRNG if needed. */
214 ctx = SSL_CTX_new(TLS_server_method());
215 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
216 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
217 || !SSL_CTX_check_private_key(ctx)) {
218 fprintf(stderr, "Error setting up SSL_CTX\n");
219 ERR_print_errors_fp(stderr);
223 /* XXX Other things like set verify locations, EDH temp callbacks. */
225 /* New SSL BIO setup as server */
226 sbio = BIO_new_ssl(ctx, 0);
227 BIO_get_ssl(sbio, &ssl);
229 fprintf(stderr, "Can't locate SSL pointer\n");
230 ERR_print_errors_fp(stderr);
234 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
235 bbio = BIO_new(BIO_f_buffer());
236 sbio = BIO_push(bbio, sbio);
237 acpt = BIO_new_accept("4433");
240 * By doing this when a new connection is established
241 * we automatically have sbio inserted into it. The
242 * BIO chain is now 'swallowed' by the accept BIO and
243 * will be freed when the accept BIO is freed.
245 BIO_set_accept_bios(acpt, sbio);
246 out = BIO_new_fp(stdout, BIO_NOCLOSE);
248 /* Setup accept BIO */
249 if (BIO_do_accept(acpt) <= 0) {
250 fprintf(stderr, "Error setting up accept BIO\n");
251 ERR_print_errors_fp(stderr);
255 /* We only want one connection so remove and free accept BIO */
256 sbio = BIO_pop(acpt);
259 if (BIO_do_handshake(sbio) <= 0) {
260 fprintf(stderr, "Error in SSL handshake\n");
261 ERR_print_errors_fp(stderr);
265 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
266 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
267 BIO_puts(sbio, "--------------------------------------------------\r\n");
270 len = BIO_gets(sbio, tmpbuf, 1024);
273 BIO_write(sbio, tmpbuf, len);
274 BIO_write(out, tmpbuf, len);
275 /* Look for blank line signifying end of headers*/
276 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
280 BIO_puts(sbio, "--------------------------------------------------\r\n");
281 BIO_puts(sbio, "\r\n");
287 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
288 the I/O BIO reference count was incorrectly incremented (instead of
289 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
290 explicitly being popped (e.g. a pop higher up the chain). Applications which
291 included workarounds for this bug (e.g. freeing BIOs more than once) should
292 be modified to handle this fix or they may free up an already freed BIO.
296 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
298 Licensed under the OpenSSL license (the "License"). You may not use
299 this file except in compliance with the License. You can obtain a copy
300 in the file LICENSE in the source distribution or at
301 L<https://www.openssl.org/source/license.html>.