1=pod 2 3=head1 NAME 4 5BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode, BIO_set_ssl_renegotiate_bytes, 6BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl, 7BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id, 8BIO_ssl_shutdown - SSL BIO 9 10=head1 SYNOPSIS 11 12 #include <openssl/bio.h> 13 #include <openssl/ssl.h> 14 15 BIO_METHOD *BIO_f_ssl(void); 16 17 #define BIO_set_ssl(b,ssl,c) BIO_ctrl(b,BIO_C_SET_SSL,c,(char *)ssl) 18 #define BIO_get_ssl(b,sslp) BIO_ctrl(b,BIO_C_GET_SSL,0,(char *)sslp) 19 #define BIO_set_ssl_mode(b,client) BIO_ctrl(b,BIO_C_SSL_MODE,client,NULL) 20 #define BIO_set_ssl_renegotiate_bytes(b,num) \ 21 BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_BYTES,num,NULL); 22 #define BIO_set_ssl_renegotiate_timeout(b,seconds) \ 23 BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_TIMEOUT,seconds,NULL); 24 #define BIO_get_num_renegotiates(b) \ 25 BIO_ctrl(b,BIO_C_SET_SSL_NUM_RENEGOTIATES,0,NULL); 26 27 BIO *BIO_new_ssl(SSL_CTX *ctx,int client); 28 BIO *BIO_new_ssl_connect(SSL_CTX *ctx); 29 BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx); 30 int BIO_ssl_copy_session_id(BIO *to,BIO *from); 31 void BIO_ssl_shutdown(BIO *bio); 32 33 #define BIO_do_handshake(b) BIO_ctrl(b,BIO_C_DO_STATE_MACHINE,0,NULL) 34 35=head1 DESCRIPTION 36 37BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which 38is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to 39SSL I/O. 40 41I/O performed on an SSL BIO communicates using the SSL protocol with 42the SSLs read and write BIOs. If an SSL connection is not established 43then an attempt is made to establish one on the first I/O call. 44 45If a BIO is appended to an SSL BIO using BIO_push() it is automatically 46used as the SSL BIOs read and write BIOs. 47 48Calling BIO_reset() on an SSL BIO closes down any current SSL connection 49by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in 50the chain: this will typically disconnect the underlying transport. 51The SSL BIO is then reset to the initial accept or connect state. 52 53If the close flag is set when an SSL BIO is freed then the internal 54SSL structure is also freed using SSL_free(). 55 56BIO_set_ssl() sets the internal SSL pointer of BIO B<b> to B<ssl> using 57the close flag B<c>. 58 59BIO_get_ssl() retrieves the SSL pointer of BIO B<b>, it can then be 60manipulated using the standard SSL library functions. 61 62BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client> 63is 1 client mode is set. If B<client> is 0 server mode is set. 64 65BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count 66to B<num>. When set after every B<num> bytes of I/O (read and write) 67the SSL session is automatically renegotiated. B<num> must be at 68least 512 bytes. 69 70BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout to 71B<seconds>. When the renegotiate timeout elapses the session is 72automatically renegotiated. 73 74BIO_get_num_renegotiates() returns the total number of session 75renegotiations due to I/O or timeout. 76 77BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using 78client mode if B<client> is non zero. 79 80BIO_new_ssl_connect() creates a new BIO chain consisting of an 81SSL BIO (using B<ctx>) followed by a connect BIO. 82 83BIO_new_buffer_ssl_connect() creates a new BIO chain consisting 84of a buffering BIO, an SSL BIO (using B<ctx>) and a connect 85BIO. 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() operation, one 111case where this happens is when step up occurs. 112 113In OpenSSL 0.9.6 and later the 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. 126 127=head1 RETURN VALUES 128 129TBA 130 131=head1 EXAMPLE 132 133This SSL/TLS client example, attempts to retrieve a page from an 134SSL/TLS web server. The I/O routines are identical to those of the 135unencrypted example in L<BIO_s_connect(3)|BIO_s_connect(3)>. 136 137 BIO *sbio, *out; 138 int len; 139 char tmpbuf[1024]; 140 SSL_CTX *ctx; 141 SSL *ssl; 142 143 ERR_load_crypto_strings(); 144 ERR_load_SSL_strings(); 145 OpenSSL_add_all_algorithms(); 146 147 /* We would seed the PRNG here if the platform didn't 148 * do it automatically 149 */ 150 151 ctx = SSL_CTX_new(SSLv23_client_method()); 152 153 /* We'd normally set some stuff like the verify paths and 154 * mode here because as things stand this will connect to 155 * any server whose certificate is signed by any CA. 156 */ 157 158 sbio = BIO_new_ssl_connect(ctx); 159 160 BIO_get_ssl(sbio, &ssl); 161 162 if(!ssl) { 163 fprintf(stderr, "Can't locate SSL pointer\n"); 164 /* whatever ... */ 165 } 166 167 /* Don't want any retries */ 168 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); 169 170 /* We might want to do other things with ssl here */ 171 172 BIO_set_conn_hostname(sbio, "localhost: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 /* whatever ... */ 179 } 180 181 if(BIO_do_handshake(sbio) <= 0) { 182 fprintf(stderr, "Error establishing SSL connection\n"); 183 ERR_print_errors_fp(stderr); 184 /* whatever ... */ 185 } 186 187 /* Could examine ssl here to get connection info */ 188 189 BIO_puts(sbio, "GET / HTTP/1.0\n\n"); 190 for(;;) { 191 len = BIO_read(sbio, tmpbuf, 1024); 192 if(len <= 0) break; 193 BIO_write(out, tmpbuf, len); 194 } 195 BIO_free_all(sbio); 196 BIO_free(out); 197 198Here is a simple server example. It makes use of a buffering 199BIO to allow lines to be read from the SSL BIO using BIO_gets. 200It creates a pseudo web page containing the actual request from 201a client and also echoes the request to standard output. 202 203 BIO *sbio, *bbio, *acpt, *out; 204 int len; 205 char tmpbuf[1024]; 206 SSL_CTX *ctx; 207 SSL *ssl; 208 209 ERR_load_crypto_strings(); 210 ERR_load_SSL_strings(); 211 OpenSSL_add_all_algorithms(); 212 213 /* Might seed PRNG here */ 214 215 ctx = SSL_CTX_new(SSLv23_server_method()); 216 217 if (!SSL_CTX_use_certificate_file(ctx,"server.pem",SSL_FILETYPE_PEM) 218 || !SSL_CTX_use_PrivateKey_file(ctx,"server.pem",SSL_FILETYPE_PEM) 219 || !SSL_CTX_check_private_key(ctx)) { 220 221 fprintf(stderr, "Error setting up SSL_CTX\n"); 222 ERR_print_errors_fp(stderr); 223 return 0; 224 } 225 226 /* Might do other things here like setting verify locations and 227 * DH and/or RSA temporary key callbacks 228 */ 229 230 /* New SSL BIO setup as server */ 231 sbio=BIO_new_ssl(ctx,0); 232 233 BIO_get_ssl(sbio, &ssl); 234 235 if(!ssl) { 236 fprintf(stderr, "Can't locate SSL pointer\n"); 237 /* whatever ... */ 238 } 239 240 /* Don't want any retries */ 241 SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); 242 243 /* Create the buffering BIO */ 244 245 bbio = BIO_new(BIO_f_buffer()); 246 247 /* Add to chain */ 248 sbio = BIO_push(bbio, sbio); 249 250 acpt=BIO_new_accept("4433"); 251 252 /* By doing this when a new connection is established 253 * we automatically have sbio inserted into it. The 254 * BIO chain is now 'swallowed' by the accept BIO and 255 * will be freed when the accept BIO is freed. 256 */ 257 258 BIO_set_accept_bios(acpt,sbio); 259 260 out = BIO_new_fp(stdout, BIO_NOCLOSE); 261 262 /* Setup accept BIO */ 263 if(BIO_do_accept(acpt) <= 0) { 264 fprintf(stderr, "Error setting up accept BIO\n"); 265 ERR_print_errors_fp(stderr); 266 return 0; 267 } 268 269 /* Now wait for incoming connection */ 270 if(BIO_do_accept(acpt) <= 0) { 271 fprintf(stderr, "Error in connection\n"); 272 ERR_print_errors_fp(stderr); 273 return 0; 274 } 275 276 /* We only want one connection so remove and free 277 * accept BIO 278 */ 279 280 sbio = BIO_pop(acpt); 281 282 BIO_free_all(acpt); 283 284 if(BIO_do_handshake(sbio) <= 0) { 285 fprintf(stderr, "Error in SSL handshake\n"); 286 ERR_print_errors_fp(stderr); 287 return 0; 288 } 289 290 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n"); 291 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n"); 292 BIO_puts(sbio, "--------------------------------------------------\r\n"); 293 294 for(;;) { 295 len = BIO_gets(sbio, tmpbuf, 1024); 296 if(len <= 0) break; 297 BIO_write(sbio, tmpbuf, len); 298 BIO_write(out, tmpbuf, len); 299 /* Look for blank line signifying end of headers*/ 300 if((tmpbuf[0] == '\r') || (tmpbuf[0] == '\n')) break; 301 } 302 303 BIO_puts(sbio, "--------------------------------------------------\r\n"); 304 BIO_puts(sbio, "\r\n"); 305 306 /* Since there is a buffering BIO present we had better flush it */ 307 BIO_flush(sbio); 308 309 BIO_free_all(sbio); 310 311=head1 BUGS 312 313In OpenSSL versions before 1.0.0 the BIO_pop() call was handled incorrectly, 314the I/O BIO reference count was incorrectly incremented (instead of 315decremented) and dissociated with the SSL BIO even if the SSL BIO was not 316explicitly being popped (e.g. a pop higher up the chain). Applications which 317included workarounds for this bug (e.g. freeing BIOs more than once) should 318be modified to handle this fix or they may free up an already freed BIO. 319 320=head1 SEE ALSO 321 322TBA 323