1=pod
2
3=head1 NAME
4
5BIO_do_handshake,
6BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode,
7BIO_set_ssl_renegotiate_bytes,
8BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
9BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id,
10BIO_ssl_shutdown - SSL BIO
11
12=head1 SYNOPSIS
13
14=for openssl multiple includes
15
16 #include <openssl/bio.h>
17 #include <openssl/ssl.h>
18
19 const BIO_METHOD *BIO_f_ssl(void);
20
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);
27
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);
33
34 long BIO_do_handshake(BIO *b);
35
36=head1 DESCRIPTION
37
38BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which
39is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to
40SSL I/O.
41
42I/O performed on an SSL BIO communicates using the SSL protocol with
43the SSLs read and write BIOs. If an SSL connection is not established
44then an attempt is made to establish one on the first I/O call.
45
46If a BIO is appended to an SSL BIO using BIO_push() it is automatically
47used as the SSL BIOs read and write BIOs.
48
49Calling BIO_reset() on an SSL BIO closes down any current SSL connection
50by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in
51the chain: this will typically disconnect the underlying transport.
52The SSL BIO is then reset to the initial accept or connect state.
53
54If the close flag is set when an SSL BIO is freed then the internal
55SSL structure is also freed using SSL_free().
56
57BIO_set_ssl() sets the internal SSL pointer of SSL BIO B<b> to B<ssl> using
58the close flag B<c>.
59
60BIO_get_ssl() retrieves the SSL pointer of SSL BIO B<b>, it can then be
61manipulated using the standard SSL library functions.
62
63BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client>
64is 1 client mode is set. If B<client> is 0 server mode is set.
65
66BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count of SSL BIO B<b>
67to B<num>. When set after every B<num> bytes of I/O (read and write)
68the SSL session is automatically renegotiated. B<num> must be at
69least 512 bytes.
70
71BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout of SSL BIO B<b>
72to B<seconds>.
73When the renegotiate timeout elapses the session is automatically renegotiated.
74
75BIO_get_num_renegotiates() returns the total number of session
76renegotiations due to I/O or timeout of SSL BIO B<b>.
77
78BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using
79client mode if B<client> is non zero.
80
81BIO_new_ssl_connect() creates a new BIO chain consisting of an
82SSL BIO (using B<ctx>) followed by a connect BIO.
83
84BIO_new_buffer_ssl_connect() creates a new BIO chain consisting
85of a buffering BIO, an SSL BIO (using B<ctx>), and a connect BIO.
86
87BIO_ssl_copy_session_id() copies an SSL session id between
88BIO chains B<from> and B<to>. It does this by locating the
89SSL BIOs in each chain and calling SSL_copy_session_id() on
90the internal SSL pointer.
91
92BIO_ssl_shutdown() closes down an SSL connection on BIO
93chain B<bio>. It does this by locating the SSL BIO in the
94chain and calling SSL_shutdown() on its internal SSL
95pointer.
96
97BIO_do_handshake() attempts to complete an SSL handshake on the
98supplied BIO and establish the SSL connection.
99For non-SSL BIOs the connection is done typically at TCP level.
100If domain name resolution yields multiple IP addresses all of them are tried
101after connect() failures.
102The function returns 1 if the connection was established successfully.
103A zero or negative value is returned if the connection could not be established.
104The call BIO_should_retry() should be used for nonblocking connect BIOs
105to determine if the call should be retried.
106If a connection has already been established this call has no effect.
107
108=head1 NOTES
109
110SSL BIOs are exceptional in that if the underlying transport
111is non blocking they can still request a retry in exceptional
112circumstances. Specifically this will happen if a session
113renegotiation takes place during a BIO_read_ex() operation, one
114case where this happens is when step up occurs.
115
116The SSL flag SSL_AUTO_RETRY can be
117set to disable this behaviour. That is when this flag is set
118an SSL BIO using a blocking transport will never request a
119retry.
120
121Since unknown BIO_ctrl() operations are sent through filter
122BIOs the servers name and port can be set using BIO_set_host()
123on the BIO returned by BIO_new_ssl_connect() without having
124to locate the connect BIO first.
125
126Applications do not have to call BIO_do_handshake() but may wish
127to do so to separate the handshake process from other I/O
128processing.
129
130BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
131BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
132BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.
133
134=head1 RETURN VALUES
135
136BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
137
138BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
139BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
140success or a value which is less than or equal to 0 if an error occurred.
141
142BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
143a valid B<BIO> structure on success or B<NULL> if an error occurred.
144
145BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
146
147BIO_do_handshake() returns 1 if the connection was established successfully.
148A zero or negative value is returned if the connection could not be established.
149
150=head1 EXAMPLES
151
152This SSL/TLS client example attempts to retrieve a page from an
153SSL/TLS web server. The I/O routines are identical to those of the
154unencrypted example in L<BIO_s_connect(3)>.
155
156 BIO *sbio, *out;
157 int len;
158 char tmpbuf[1024];
159 SSL_CTX *ctx;
160 SSL *ssl;
161
162 /* XXX Seed the PRNG if needed. */
163
164 ctx = SSL_CTX_new(TLS_client_method());
165
166 /* XXX Set verify paths and mode here. */
167
168 sbio = BIO_new_ssl_connect(ctx);
169 BIO_get_ssl(sbio, &ssl);
170 if (ssl == NULL) {
171     fprintf(stderr, "Can't locate SSL pointer\n");
172     ERR_print_errors_fp(stderr);
173     exit(1);
174 }
175
176 /* XXX We might want to do other things with ssl here */
177
178 /* An empty host part means the loopback address */
179 BIO_set_conn_hostname(sbio, ":https");
180
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);
185     exit(1);
186 }
187
188 /* XXX Could examine ssl here to get connection info */
189
190 BIO_puts(sbio, "GET / HTTP/1.0\n\n");
191 for (;;) {
192     len = BIO_read(sbio, tmpbuf, 1024);
193     if (len <= 0)
194         break;
195     BIO_write(out, tmpbuf, len);
196 }
197 BIO_free_all(sbio);
198 BIO_free(out);
199
200Here is a simple server example. It makes use of a buffering
201BIO to allow lines to be read from the SSL BIO using BIO_gets.
202It creates a pseudo web page containing the actual request from
203a client and also echoes the request to standard output.
204
205 BIO *sbio, *bbio, *acpt, *out;
206 int len;
207 char tmpbuf[1024];
208 SSL_CTX *ctx;
209 SSL *ssl;
210
211 /* XXX Seed the PRNG if needed. */
212
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);
219     exit(1);
220 }
221
222 /* XXX Other things like set verify locations, EDH temp callbacks. */
223
224 /* New SSL BIO setup as server */
225 sbio = BIO_new_ssl(ctx, 0);
226 BIO_get_ssl(sbio, &ssl);
227 if (ssl == NULL) {
228     fprintf(stderr, "Can't locate SSL pointer\n");
229     ERR_print_errors_fp(stderr);
230     exit(1);
231 }
232
233 bbio = BIO_new(BIO_f_buffer());
234 sbio = BIO_push(bbio, sbio);
235 acpt = BIO_new_accept("4433");
236
237 /*
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.
242  */
243 BIO_set_accept_bios(acpt, sbio);
244 out = BIO_new_fp(stdout, BIO_NOCLOSE);
245
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);
250     exit(1);
251 }
252
253 /* We only want one connection so remove and free accept BIO */
254 sbio = BIO_pop(acpt);
255 BIO_free_all(acpt);
256
257 if (BIO_do_handshake(sbio) <= 0) {
258     fprintf(stderr, "Error in SSL handshake\n");
259     ERR_print_errors_fp(stderr);
260     exit(1);
261 }
262
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");
266
267 for (;;) {
268     len = BIO_gets(sbio, tmpbuf, 1024);
269     if (len <= 0)
270         break;
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')
275         break;
276 }
277
278 BIO_puts(sbio, "--------------------------------------------------\r\n");
279 BIO_puts(sbio, "\r\n");
280 BIO_flush(sbio);
281 BIO_free_all(sbio);
282
283=head1 HISTORY
284
285In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
286the I/O BIO reference count was incorrectly incremented (instead of
287decremented) and dissociated with the SSL BIO even if the SSL BIO was not
288explicitly being popped (e.g. a pop higher up the chain). Applications which
289included workarounds for this bug (e.g. freeing BIOs more than once) should
290be modified to handle this fix or they may free up an already freed BIO.
291
292=head1 COPYRIGHT
293
294Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
295
296Licensed under the Apache License 2.0 (the "License").  You may not use
297this file except in compliance with the License.  You can obtain a copy
298in the file LICENSE in the source distribution or at
299L<https://www.openssl.org/source/license.html>.
300
301=cut
302