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 BIO B<b> to B<ssl> using 58the close flag B<c>. 59 60BIO_get_ssl() retrieves the SSL pointer of 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 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 to 72B<seconds>. When the renegotiate timeout elapses the session is 73automatically renegotiated. 74 75BIO_get_num_renegotiates() returns the total number of session 76renegotiations due to I/O or timeout. 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 86BIO. 87 88BIO_ssl_copy_session_id() copies an SSL session id between 89BIO chains B<from> and B<to>. It does this by locating the 90SSL BIOs in each chain and calling SSL_copy_session_id() on 91the internal SSL pointer. 92 93BIO_ssl_shutdown() closes down an SSL connection on BIO 94chain B<bio>. It does this by locating the SSL BIO in the 95chain and calling SSL_shutdown() on its internal SSL 96pointer. 97 98BIO_do_handshake() attempts to complete an SSL handshake on the 99-supplied BIO and establish the SSL connection. 100For non-SSL BIOs the connection is done typically at TCP level. 101If domain name resolution yields multiple IP addresses all of them are tried 102after connect() failures. 103The function returns 1 if the connection was established successfully. 104A zero or negative value is returned if the connection could not be established. 105The call BIO_should_retry() should be used for nonblocking connect BIOs 106to determine if the call should be retried. 107If a connection has already been established this call has no effect. 108 109=head1 NOTES 110 111SSL BIOs are exceptional in that if the underlying transport 112is non blocking they can still request a retry in exceptional 113circumstances. Specifically this will happen if a session 114renegotiation takes place during a BIO_read_ex() operation, one 115case where this happens is when step up occurs. 116 117The SSL flag SSL_AUTO_RETRY can be 118set to disable this behaviour. That is when this flag is set 119an SSL BIO using a blocking transport will never request a 120retry. 121 122Since unknown BIO_ctrl() operations are sent through filter 123BIOs the servers name and port can be set using BIO_set_host() 124on the BIO returned by BIO_new_ssl_connect() without having 125to locate the connect BIO first. 126 127Applications do not have to call BIO_do_handshake() but may wish 128to do so to separate the handshake process from other I/O 129processing. 130 131BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), 132BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(), 133BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros. 134 135=head1 RETURN VALUES 136 137BIO_f_ssl() returns the SSL B<BIO_METHOD> structure. 138 139BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(), 140BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on 141success or a value which is less than or equal to 0 if an error occurred. 142 143BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return 144a valid B<BIO> structure on success or B<NULL> if an error occurred. 145 146BIO_ssl_copy_session_id() returns 1 on success or 0 on error. 147 148BIO_do_handshake() returns 1 if the connection was established successfully. 149A zero or negative value is returned if the connection could not be established. 150 151=head1 EXAMPLES 152 153This SSL/TLS client example attempts to retrieve a page from an 154SSL/TLS web server. The I/O routines are identical to those of the 155unencrypted 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 201Here is a simple server example. It makes use of a buffering 202BIO to allow lines to be read from the SSL BIO using BIO_gets. 203It creates a pseudo web page containing the actual request from 204a 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 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 Apache License 2.0 (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