1BIO_F_SSL(3)                        OpenSSL                       BIO_F_SSL(3)
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4

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. It returns 1 if the
94       connection was established successfully. A zero or negative value is
95       returned if the connection could not be established, the call
96       BIO_should_retry() should be used for non blocking connect BIOs to
97       determine if the call should be retried. If an SSL connection has
98       already been established this call has no effect.
99

NOTES

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

RETURN VALUES

125       BIO_f_ssl() returns the SSL BIO_METHOD structure.
126
127       BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
128       BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout() and
129       BIO_get_num_renegotiates() return 1 on success or a value which is less
130       than or equal to 0 if an error occurred.
131
132       BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect()
133       return a valid BIO structure on success or NULL if an error occurred.
134
135       BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
136
137       BIO_do_handshake() returns 1 if the connection was established
138       successfully.  A zero or negative value is returned if the connection
139       could not be established.
140

EXAMPLES

142       This SSL/TLS client example attempts to retrieve a page from an SSL/TLS
143       web server. The I/O routines are identical to those of the unencrypted
144       example in BIO_s_connect(3).
145
146        BIO *sbio, *out;
147        int len;
148        char tmpbuf[1024];
149        SSL_CTX *ctx;
150        SSL *ssl;
151
152        /* XXX Seed the PRNG if needed. */
153
154        ctx = SSL_CTX_new(TLS_client_method());
155
156        /* XXX Set verify paths and mode here. */
157
158        sbio = BIO_new_ssl_connect(ctx);
159        BIO_get_ssl(sbio, &ssl);
160        if (ssl == NULL) {
161            fprintf(stderr, "Can't locate SSL pointer\n");
162            ERR_print_errors_fp(stderr);
163            exit(1);
164        }
165
166        /* Don't want any retries */
167        SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
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        SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
227        bbio = BIO_new(BIO_f_buffer());
228        sbio = BIO_push(bbio, sbio);
229        acpt = BIO_new_accept("4433");
230
231        /*
232         * By doing this when a new connection is established
233         * we automatically have sbio inserted into it. The
234         * BIO chain is now 'swallowed' by the accept BIO and
235         * will be freed when the accept BIO is freed.
236         */
237        BIO_set_accept_bios(acpt, sbio);
238        out = BIO_new_fp(stdout, BIO_NOCLOSE);
239
240        /* Setup accept BIO */
241        if (BIO_do_accept(acpt) <= 0) {
242            fprintf(stderr, "Error setting up accept BIO\n");
243            ERR_print_errors_fp(stderr);
244            exit(1);
245        }
246
247        /* We only want one connection so remove and free accept BIO */
248        sbio = BIO_pop(acpt);
249        BIO_free_all(acpt);
250
251        if (BIO_do_handshake(sbio) <= 0) {
252            fprintf(stderr, "Error in SSL handshake\n");
253            ERR_print_errors_fp(stderr);
254            exit(1);
255        }
256
257        BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
258        BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
259        BIO_puts(sbio, "--------------------------------------------------\r\n");
260
261        for (;;) {
262            len = BIO_gets(sbio, tmpbuf, 1024);
263            if (len <= 0)
264                break;
265            BIO_write(sbio, tmpbuf, len);
266            BIO_write(out, tmpbuf, len);
267            /* Look for blank line signifying end of headers*/
268            if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
269                break;
270        }
271
272        BIO_puts(sbio, "--------------------------------------------------\r\n");
273        BIO_puts(sbio, "\r\n");
274        BIO_flush(sbio);
275        BIO_free_all(sbio);
276

HISTORY

278       In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, the
279       I/O BIO reference count was incorrectly incremented (instead of
280       decremented) and dissociated with the SSL BIO even if the SSL BIO was
281       not explicitly being popped (e.g. a pop higher up the chain).
282       Applications which included workarounds for this bug (e.g. freeing BIOs
283       more than once) should be modified to handle this fix or they may free
284       up an already freed BIO.
285
287       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
288
289       Licensed under the OpenSSL license (the "License").  You may not use
290       this file except in compliance with the License.  You can obtain a copy
291       in the file LICENSE in the source distribution or at
292       <https://www.openssl.org/source/license.html>.
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2961.1.1q                            2023-07-20                      BIO_F_SSL(3)
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