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1 | =pod | |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | BIO_do_handshake, | |
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 | |
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 | ||
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 | |
40 | SSL I/O. | |
41 | ||
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. | |
45 | ||
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. | |
48 | ||
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. | |
53 | ||
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(). | |
56 | ||
57 | BIO_set_ssl() sets the internal SSL pointer of BIO B<b> to B<ssl> using | |
58 | the close flag B<c>. | |
59 | ||
60 | BIO_get_ssl() retrieves the SSL pointer of BIO B<b>, it can then be | |
61 | manipulated using the standard SSL library functions. | |
62 | ||
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. | |
65 | ||
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 | |
69 | least 512 bytes. | |
70 | ||
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. | |
74 | ||
75 | BIO_get_num_renegotiates() returns the total number of session | |
76 | renegotiations due to I/O or timeout. | |
77 | ||
78 | BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using | |
79 | client mode if B<client> is non zero. | |
80 | ||
81 | BIO_new_ssl_connect() creates a new BIO chain consisting of an | |
82 | SSL BIO (using B<ctx>) followed by a connect BIO. | |
83 | ||
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 | |
86 | BIO. | |
87 | ||
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. | |
92 | ||
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 | |
96 | pointer. | |
97 | ||
98 | BIO_do_handshake() attempts to complete an SSL handshake on the | |
99 | -supplied BIO and establish the SSL connection. | |
100 | For non-SSL BIOs the connection is done typically at TCP level. | |
101 | If domain name resolution yields multiple IP addresses all of them are tried | |
102 | after connect() failures. | |
103 | The function returns 1 if the connection was established successfully. | |
104 | A zero or negative value is returned if the connection could not be established. | |
105 | The call BIO_should_retry() should be used for nonblocking connect BIOs | |
106 | to determine if the call should be retried. | |
107 | If a connection has already been established this call has no effect. | |
108 | ||
109 | =head1 NOTES | |
110 | ||
111 | SSL BIOs are exceptional in that if the underlying transport | |
112 | is non blocking they can still request a retry in exceptional | |
113 | circumstances. Specifically this will happen if a session | |
114 | renegotiation takes place during a BIO_read_ex() operation, one | |
115 | case where this happens is when step up occurs. | |
116 | ||
117 | The SSL flag SSL_AUTO_RETRY can be | |
118 | set to disable this behaviour. That is when this flag is set | |
119 | an SSL BIO using a blocking transport will never request a | |
120 | retry. | |
121 | ||
122 | Since unknown BIO_ctrl() operations are sent through filter | |
123 | BIOs the servers name and port can be set using BIO_set_host() | |
124 | on the BIO returned by BIO_new_ssl_connect() without having | |
125 | to locate the connect BIO first. | |
126 | ||
127 | Applications do not have to call BIO_do_handshake() but may wish | |
128 | to do so to separate the handshake process from other I/O | |
129 | processing. | |
130 | ||
131 | BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), | |
132 | BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(), | |
133 | BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros. | |
134 | ||
135 | =head1 RETURN VALUES | |
136 | ||
137 | BIO_f_ssl() returns the SSL B<BIO_METHOD> structure. | |
138 | ||
139 | BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(), | |
140 | BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on | |
141 | success or a value which is less than or equal to 0 if an error occurred. | |
142 | ||
143 | BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return | |
144 | a valid B<BIO> structure on success or B<NULL> if an error occurred. | |
145 | ||
146 | BIO_ssl_copy_session_id() returns 1 on success or 0 on error. | |
147 | ||
148 | BIO_do_handshake() returns 1 if the connection was established successfully. | |
149 | A zero or negative value is returned if the connection could not be established. | |
150 | ||
151 | =head1 EXAMPLES | |
152 | ||
153 | This SSL/TLS client example attempts to retrieve a page from an | |
154 | SSL/TLS web server. The I/O routines are identical to those of the | |
155 | unencrypted example in L<BIO_s_connect(3)>. | |
156 | ||
157 | BIO *sbio, *out; | |
158 | int len; | |
159 | char tmpbuf[1024]; | |
160 | SSL_CTX *ctx; | |
161 | SSL *ssl; | |
162 | ||
163 | /* XXX Seed the PRNG if needed. */ | |
164 | ||
165 | ctx = SSL_CTX_new(TLS_client_method()); | |
166 | ||
167 | /* XXX Set verify paths and mode here. */ | |
168 | ||
169 | sbio = BIO_new_ssl_connect(ctx); | |
170 | BIO_get_ssl(sbio, &ssl); | |
171 | if (ssl == NULL) { | |
172 | fprintf(stderr, "Can't locate SSL pointer\n"); | |
173 | ERR_print_errors_fp(stderr); | |
174 | exit(1); | |
175 | } | |
176 | ||
177 | /* XXX We might want to do other things with ssl here */ | |
178 | ||
179 | /* An empty host part means the loopback address */ | |
180 | BIO_set_conn_hostname(sbio, ":https"); | |
181 | ||
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); | |
186 | exit(1); | |
187 | } | |
188 | ||
189 | /* XXX Could examine ssl here to get connection info */ | |
190 | ||
191 | BIO_puts(sbio, "GET / HTTP/1.0\n\n"); | |
192 | for (;;) { | |
193 | len = BIO_read(sbio, tmpbuf, 1024); | |
194 | if (len <= 0) | |
195 | break; | |
196 | BIO_write(out, tmpbuf, len); | |
197 | } | |
198 | BIO_free_all(sbio); | |
199 | BIO_free(out); | |
200 | ||
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. | |
205 | ||
206 | BIO *sbio, *bbio, *acpt, *out; | |
207 | int len; | |
208 | char tmpbuf[1024]; | |
209 | SSL_CTX *ctx; | |
210 | SSL *ssl; | |
211 | ||
212 | /* XXX Seed the PRNG if needed. */ | |
213 | ||
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); | |
220 | exit(1); | |
221 | } | |
222 | ||
223 | /* XXX Other things like set verify locations, EDH temp callbacks. */ | |
224 | ||
225 | /* New SSL BIO setup as server */ | |
226 | sbio = BIO_new_ssl(ctx, 0); | |
227 | BIO_get_ssl(sbio, &ssl); | |
228 | if (ssl == NULL) { | |
229 | fprintf(stderr, "Can't locate SSL pointer\n"); | |
230 | ERR_print_errors_fp(stderr); | |
231 | exit(1); | |
232 | } | |
233 | ||
234 | bbio = BIO_new(BIO_f_buffer()); | |
235 | sbio = BIO_push(bbio, sbio); | |
236 | acpt = BIO_new_accept("4433"); | |
237 | ||
238 | /* | |
239 | * By doing this when a new connection is established | |
240 | * we automatically have sbio inserted into it. The | |
241 | * BIO chain is now 'swallowed' by the accept BIO and | |
242 | * will be freed when the accept BIO is freed. | |
243 | */ | |
244 | BIO_set_accept_bios(acpt, sbio); | |
245 | out = BIO_new_fp(stdout, BIO_NOCLOSE); | |
246 | ||
247 | /* Setup accept BIO */ | |
248 | if (BIO_do_accept(acpt) <= 0) { | |
249 | fprintf(stderr, "Error setting up accept BIO\n"); | |
250 | ERR_print_errors_fp(stderr); | |
251 | exit(1); | |
252 | } | |
253 | ||
254 | /* We only want one connection so remove and free accept BIO */ | |
255 | sbio = BIO_pop(acpt); | |
256 | BIO_free_all(acpt); | |
257 | ||
258 | if (BIO_do_handshake(sbio) <= 0) { | |
259 | fprintf(stderr, "Error in SSL handshake\n"); | |
260 | ERR_print_errors_fp(stderr); | |
261 | exit(1); | |
262 | } | |
263 | ||
264 | BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n"); | |
265 | BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n"); | |
266 | BIO_puts(sbio, "--------------------------------------------------\r\n"); | |
267 | ||
268 | for (;;) { | |
269 | len = BIO_gets(sbio, tmpbuf, 1024); | |
270 | if (len <= 0) | |
271 | break; | |
272 | BIO_write(sbio, tmpbuf, len); | |
273 | BIO_write(out, tmpbuf, len); | |
274 | /* Look for blank line signifying end of headers*/ | |
275 | if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n') | |
276 | break; | |
277 | } | |
278 | ||
279 | BIO_puts(sbio, "--------------------------------------------------\r\n"); | |
280 | BIO_puts(sbio, "\r\n"); | |
281 | BIO_flush(sbio); | |
282 | BIO_free_all(sbio); | |
283 | ||
284 | =head1 HISTORY | |
285 | ||
286 | In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, | |
287 | the I/O BIO reference count was incorrectly incremented (instead of | |
288 | decremented) and dissociated with the SSL BIO even if the SSL BIO was not | |
289 | explicitly being popped (e.g. a pop higher up the chain). Applications which | |
290 | included workarounds for this bug (e.g. freeing BIOs more than once) should | |
291 | be modified to handle this fix or they may free up an already freed BIO. | |
292 | ||
293 | =head1 COPYRIGHT | |
294 | ||
295 | Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. | |
296 | ||
297 | Licensed under the Apache License 2.0 (the "License"). You may not use | |
298 | this file except in compliance with the License. You can obtain a copy | |
299 | in the file LICENSE in the source distribution or at | |
300 | L<https://www.openssl.org/source/license.html>. | |
301 | ||
302 | =cut |