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 comment 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. It returns 1 99if the connection was established successfully. A zero or negative 100value is returned if the connection could not be established, the 101call BIO_should_retry() should be used for non blocking connect BIOs 102to determine if the call should be retried. If an SSL connection has 103already been established this call has no effect. 104 105=head1 NOTES 106 107SSL BIOs are exceptional in that if the underlying transport 108is non blocking they can still request a retry in exceptional 109circumstances. Specifically this will happen if a session 110renegotiation takes place during a BIO_read_ex() operation, one 111case where this happens is when step up occurs. 112 113The SSL flag SSL_AUTO_RETRY can be 114set to disable this behaviour. That is when this flag is set 115an SSL BIO using a blocking transport will never request a 116retry. 117 118Since unknown BIO_ctrl() operations are sent through filter 119BIOs the servers name and port can be set using BIO_set_host() 120on the BIO returned by BIO_new_ssl_connect() without having 121to locate the connect BIO first. 122 123Applications do not have to call BIO_do_handshake() but may wish 124to do so to separate the handshake process from other I/O 125processing. 126 127BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), 128BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(), 129BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros. 130 131=head1 RETURN VALUES 132 133BIO_f_ssl() returns the SSL B<BIO_METHOD> structure. 134 135BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(), 136BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on 137success or a value which is less than or equal to 0 if an error occurred. 138 139BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return 140a valid B<BIO> structure on success or B<NULL> if an error occurred. 141 142BIO_ssl_copy_session_id() returns 1 on success or 0 on error. 143 144BIO_do_handshake() returns 1 if the connection was established successfully. 145A zero or negative value is returned if the connection could not be established. 146 147=head1 EXAMPLES 148 149This SSL/TLS client example attempts to retrieve a page from an 150SSL/TLS web server. The I/O routines are identical to those of the 151unencrypted example in L<BIO_s_connect(3)>. 152 153 BIO *sbio, *out; 154 int len; 155 char tmpbuf[1024]; 156 SSL_CTX *ctx; 157 SSL *ssl; 158 159 /* XXX Seed the PRNG if needed. */ 160 161 ctx = SSL_CTX_new(TLS_client_method()); 162 163 /* XXX Set verify paths and mode here. */ 164 165 sbio = BIO_new_ssl_connect(ctx); 166 BIO_get_ssl(sbio, &ssl); 167 if (ssl == NULL) { 168 fprintf(stderr, "Can't locate SSL pointer\n"); 169 ERR_print_errors_fp(stderr); 170 exit(1); 171 } 172 173 /* Don't want any retries */ 174 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); 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 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); 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 286In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, 287the I/O BIO reference count was incorrectly incremented (instead of 288decremented) and dissociated with the SSL BIO even if the SSL BIO was not 289explicitly being popped (e.g. a pop higher up the chain). Applications which 290included workarounds for this bug (e.g. freeing BIOs more than once) should 291be modified to handle this fix or they may free up an already freed BIO. 292 293=head1 COPYRIGHT 294 295Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 296 297Licensed under the OpenSSL license (the "License"). You may not use 298this file except in compliance with the License. You can obtain a copy 299in the file LICENSE in the source distribution or at 300L<https://www.openssl.org/source/license.html>. 301 302=cut 303