1BIO_F_SSL(3ossl)                    OpenSSL                   BIO_F_SSL(3ossl)
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NAME

6       BIO_do_handshake, BIO_f_ssl, BIO_set_ssl, BIO_get_ssl,
7       BIO_set_ssl_mode, 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,
10       BIO_ssl_copy_session_id, BIO_ssl_shutdown - SSL BIO
11

SYNOPSIS

13        #include <openssl/bio.h>
14        #include <openssl/ssl.h>
15
16        const BIO_METHOD *BIO_f_ssl(void);
17
18        long BIO_set_ssl(BIO *b, SSL *ssl, long c);
19        long BIO_get_ssl(BIO *b, SSL **sslp);
20        long BIO_set_ssl_mode(BIO *b, long client);
21        long BIO_set_ssl_renegotiate_bytes(BIO *b, long num);
22        long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
23        long BIO_get_num_renegotiates(BIO *b);
24
25        BIO *BIO_new_ssl(SSL_CTX *ctx, int client);
26        BIO *BIO_new_ssl_connect(SSL_CTX *ctx);
27        BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx);
28        int BIO_ssl_copy_session_id(BIO *to, BIO *from);
29        void BIO_ssl_shutdown(BIO *bio);
30
31        long BIO_do_handshake(BIO *b);
32

DESCRIPTION

34       BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which is a
35       wrapper round the OpenSSL SSL routines adding a BIO "flavour" to SSL
36       I/O.
37
38       I/O performed on an SSL BIO communicates using the SSL protocol with
39       the SSLs read and write BIOs. If an SSL connection is not established
40       then an attempt is made to establish one on the first I/O call.
41
42       If a BIO is appended to an SSL BIO using BIO_push() it is automatically
43       used as the SSL BIOs read and write BIOs.
44
45       Calling BIO_reset() on an SSL BIO closes down any current SSL
46       connection by calling SSL_shutdown(). BIO_reset() is then sent to the
47       next BIO in the chain: this will typically disconnect the underlying
48       transport.  The SSL BIO is then reset to the initial accept or connect
49       state.
50
51       If the close flag is set when an SSL BIO is freed then the internal SSL
52       structure is also freed using SSL_free().
53
54       BIO_set_ssl() sets the internal SSL pointer of SSL BIO b to ssl using
55       the close flag c.
56
57       BIO_get_ssl() retrieves the SSL pointer of SSL BIO b, it can then be
58       manipulated using the standard SSL library functions.
59
60       BIO_set_ssl_mode() sets the SSL BIO mode to client. If client is 1
61       client mode is set. If client is 0 server mode is set.
62
63       BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count of SSL
64       BIO b to num. When set after every num bytes of I/O (read and write)
65       the SSL session is automatically renegotiated. num must be at least 512
66       bytes.
67
68       BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout of SSL
69       BIO b to seconds.  When the renegotiate timeout elapses the session is
70       automatically renegotiated.
71
72       BIO_get_num_renegotiates() returns the total number of session
73       renegotiations due to I/O or timeout of SSL BIO b.
74
75       BIO_new_ssl() allocates an SSL BIO using SSL_CTX ctx and using client
76       mode if client is non zero.
77
78       BIO_new_ssl_connect() creates a new BIO chain consisting of an SSL BIO
79       (using ctx) followed by a connect BIO.
80
81       BIO_new_buffer_ssl_connect() creates a new BIO chain consisting of a
82       buffering BIO, an SSL BIO (using ctx), and a connect BIO.
83
84       BIO_ssl_copy_session_id() copies an SSL session id between BIO chains
85       from and to. It does this by locating the SSL BIOs in each chain and
86       calling SSL_copy_session_id() on the internal SSL pointer.
87
88       BIO_ssl_shutdown() closes down an SSL connection on BIO chain bio. It
89       does this by locating the SSL BIO in the chain and calling
90       SSL_shutdown() on its internal SSL pointer.
91
92       BIO_do_handshake() attempts to complete an SSL handshake on the
93       supplied BIO and establish the SSL connection.  For non-SSL BIOs the
94       connection is done typically at TCP level.  If domain name resolution
95       yields multiple IP addresses all of them are tried after connect()
96       failures.  The function returns 1 if the connection was established
97       successfully.  A zero or negative value is returned if the connection
98       could not be established.  The call BIO_should_retry() should be used
99       for nonblocking connect BIOs to determine if the call should be
100       retried.  If a connection has already been established this call has no
101       effect.
102

NOTES

104       SSL BIOs are exceptional in that if the underlying transport is non
105       blocking they can still request a retry in exceptional circumstances.
106       Specifically this will happen if a session renegotiation takes place
107       during a BIO_read_ex() operation, one case where this happens is when
108       step up occurs.
109
110       The SSL flag SSL_AUTO_RETRY can be set to disable this behaviour. That
111       is when this flag is set an SSL BIO using a blocking transport will
112       never request a retry.
113
114       Since unknown BIO_ctrl() operations are sent through filter BIOs the
115       servers name and port can be set using BIO_set_host() on the BIO
116       returned by BIO_new_ssl_connect() without having to locate the connect
117       BIO first.
118
119       Applications do not have to call BIO_do_handshake() but may wish to do
120       so to separate the handshake process from other I/O processing.
121
122       BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
123       BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
124       BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as
125       macros.
126

RETURN VALUES

128       BIO_f_ssl() returns the SSL BIO_METHOD structure.
129
130       BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
131       BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout() and
132       BIO_get_num_renegotiates() return 1 on success or a value which is less
133       than or equal to 0 if an error occurred.
134
135       BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect()
136       return a valid BIO structure on success or NULL if an error occurred.
137
138       BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
139
140       BIO_do_handshake() returns 1 if the connection was established
141       successfully.  A zero or negative value is returned if the connection
142       could not be established.
143

EXAMPLES

145       This SSL/TLS client example attempts to retrieve a page from an SSL/TLS
146       web server. The I/O routines are identical to those of the unencrypted
147       example in BIO_s_connect(3).
148
149        BIO *sbio, *out;
150        int len;
151        char tmpbuf[1024];
152        SSL_CTX *ctx;
153        SSL *ssl;
154
155        /* XXX Seed the PRNG if needed. */
156
157        ctx = SSL_CTX_new(TLS_client_method());
158
159        /* XXX Set verify paths and mode here. */
160
161        sbio = BIO_new_ssl_connect(ctx);
162        BIO_get_ssl(sbio, &ssl);
163        if (ssl == NULL) {
164            fprintf(stderr, "Can't locate SSL pointer\n");
165            ERR_print_errors_fp(stderr);
166            exit(1);
167        }
168
169        /* XXX We might want to do other things with ssl here */
170
171        /* An empty host part means the loopback address */
172        BIO_set_conn_hostname(sbio, ":https");
173
174        out = BIO_new_fp(stdout, BIO_NOCLOSE);
175        if (BIO_do_connect(sbio) <= 0) {
176            fprintf(stderr, "Error connecting to server\n");
177            ERR_print_errors_fp(stderr);
178            exit(1);
179        }
180
181        /* XXX Could examine ssl here to get connection info */
182
183        BIO_puts(sbio, "GET / HTTP/1.0\n\n");
184        for (;;) {
185            len = BIO_read(sbio, tmpbuf, 1024);
186            if (len <= 0)
187                break;
188            BIO_write(out, tmpbuf, len);
189        }
190        BIO_free_all(sbio);
191        BIO_free(out);
192
193       Here is a simple server example. It makes use of a buffering BIO to
194       allow lines to be read from the SSL BIO using BIO_gets.  It creates a
195       pseudo web page containing the actual request from a client and also
196       echoes the request to standard output.
197
198        BIO *sbio, *bbio, *acpt, *out;
199        int len;
200        char tmpbuf[1024];
201        SSL_CTX *ctx;
202        SSL *ssl;
203
204        /* XXX Seed the PRNG if needed. */
205
206        ctx = SSL_CTX_new(TLS_server_method());
207        if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
208                || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
209                || !SSL_CTX_check_private_key(ctx)) {
210            fprintf(stderr, "Error setting up SSL_CTX\n");
211            ERR_print_errors_fp(stderr);
212            exit(1);
213        }
214
215        /* XXX Other things like set verify locations, EDH temp callbacks. */
216
217        /* New SSL BIO setup as server */
218        sbio = BIO_new_ssl(ctx, 0);
219        BIO_get_ssl(sbio, &ssl);
220        if (ssl == NULL) {
221            fprintf(stderr, "Can't locate SSL pointer\n");
222            ERR_print_errors_fp(stderr);
223            exit(1);
224        }
225
226        bbio = BIO_new(BIO_f_buffer());
227        sbio = BIO_push(bbio, sbio);
228        acpt = BIO_new_accept("4433");
229
230        /*
231         * By doing this when a new connection is established
232         * we automatically have sbio inserted into it. The
233         * BIO chain is now 'swallowed' by the accept BIO and
234         * will be freed when the accept BIO is freed.
235         */
236        BIO_set_accept_bios(acpt, sbio);
237        out = BIO_new_fp(stdout, BIO_NOCLOSE);
238
239        /* First call to BIO_do_accept() sets up accept BIO */
240        if (BIO_do_accept(acpt) <= 0) {
241            fprintf(stderr, "Error setting up accept BIO\n");
242            ERR_print_errors_fp(stderr);
243            exit(1);
244        }
245
246       /* Second call to BIO_do_accept() waits for incoming connection */
247        if (BIO_do_accept(acpt) <= 0) {
248           fprintf(stderr, "Error accepting connection\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

HISTORY

284       In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, the
285       I/O BIO reference count was incorrectly incremented (instead of
286       decremented) and dissociated with the SSL BIO even if the SSL BIO was
287       not explicitly being popped (e.g. a pop higher up the chain).
288       Applications which included workarounds for this bug (e.g. freeing BIOs
289       more than once) should be modified to handle this fix or they may free
290       up an already freed BIO.
291
293       Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
294
295       Licensed under the Apache License 2.0 (the "License").  You may not use
296       this file except in compliance with the License.  You can obtain a copy
297       in the file LICENSE in the source distribution or at
298       <https://www.openssl.org/source/license.html>.
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3023.1.1                             2023-08-31                  BIO_F_SSL(3ossl)
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