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 /* First call to BIO_do_accept() sets up 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/* Second call to BIO_do_accept() waits for incoming connection */ 254 if (BIO_do_accept(acpt) <= 0) { 255 fprintf(stderr, "Error accepting connection\n"); 256 ERR_print_errors_fp(stderr); 257 exit(1); 258 } 259 260 /* We only want one connection so remove and free accept BIO */ 261 sbio = BIO_pop(acpt); 262 BIO_free_all(acpt); 263 264 if (BIO_do_handshake(sbio) <= 0) { 265 fprintf(stderr, "Error in SSL handshake\n"); 266 ERR_print_errors_fp(stderr); 267 exit(1); 268 } 269 270 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n"); 271 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n"); 272 BIO_puts(sbio, "--------------------------------------------------\r\n"); 273 274 for (;;) { 275 len = BIO_gets(sbio, tmpbuf, 1024); 276 if (len <= 0) 277 break; 278 BIO_write(sbio, tmpbuf, len); 279 BIO_write(out, tmpbuf, len); 280 /* Look for blank line signifying end of headers*/ 281 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n') 282 break; 283 } 284 285 BIO_puts(sbio, "--------------------------------------------------\r\n"); 286 BIO_puts(sbio, "\r\n"); 287 BIO_flush(sbio); 288 BIO_free_all(sbio); 289 290=head1 HISTORY 291 292In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, 293the I/O BIO reference count was incorrectly incremented (instead of 294decremented) and dissociated with the SSL BIO even if the SSL BIO was not 295explicitly being popped (e.g. a pop higher up the chain). Applications which 296included workarounds for this bug (e.g. freeing BIOs more than once) should 297be modified to handle this fix or they may free up an already freed BIO. 298 299=head1 COPYRIGHT 300 301Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved. 302 303Licensed under the Apache License 2.0 (the "License"). You may not use 304this file except in compliance with the License. You can obtain a copy 305in the file LICENSE in the source distribution or at 306L<https://www.openssl.org/source/license.html>. 307 308=cut 309