BIO_f_ssl(3) OpenSSL BIO_f_ssl(3) NNAAMMEE BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode, BIO_set_ssl_renegotiate_bytes, BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl, BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id, BIO_ssl_shutdown - SSL BIO SSYYNNOOPPSSIISS #include #include BIO_METHOD *BIO_f_ssl(void); #define BIO_set_ssl(b,ssl,c) BIO_ctrl(b,BIO_C_SET_SSL,c,(char *)ssl) #define BIO_get_ssl(b,sslp) BIO_ctrl(b,BIO_C_GET_SSL,0,(char *)sslp) #define BIO_set_ssl_mode(b,client) BIO_ctrl(b,BIO_C_SSL_MODE,client,NULL) #define BIO_set_ssl_renegotiate_bytes(b,num) \ BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_BYTES,num,NULL); #define BIO_set_ssl_renegotiate_timeout(b,seconds) \ BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_TIMEOUT,seconds,NULL); #define BIO_get_num_renegotiates(b) \ BIO_ctrl(b,BIO_C_SET_SSL_NUM_RENEGOTIATES,0,NULL); BIO *BIO_new_ssl(SSL_CTX *ctx,int client); BIO *BIO_new_ssl_connect(SSL_CTX *ctx); BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx); int BIO_ssl_copy_session_id(BIO *to,BIO *from); void BIO_ssl_shutdown(BIO *bio); #define BIO_do_handshake(b) BIO_ctrl(b,BIO_C_DO_STATE_MACHINE,0,NULL) DDEESSCCRRIIPPTTIIOONN _B_I_O___f___s_s_l_(_) returns the SSL BIO method. This is a filter BIO which is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to SSL I/O. I/O performed on an SSL BIO communicates using the SSL protocol with the SSLs read and write BIOs. If an SSL connection is not established then an attempt is made to establish one on the first I/O call. If a BIO is appended to an SSL BIO using _B_I_O___p_u_s_h_(_) it is automatically used as the SSL BIOs read and write BIOs. Calling _B_I_O___r_e_s_e_t_(_) on an SSL BIO closes down any current SSL connec- tion by calling _S_S_L___s_h_u_t_d_o_w_n_(_). _B_I_O___r_e_s_e_t_(_) is then sent to the next BIO in the chain: this will typically disconnect the underlying trans- port. The SSL BIO is then reset to the initial accept or connect state. If the close flag is set when an SSL BIO is freed then the internal SSL structure is also freed using _S_S_L___f_r_e_e_(_). _B_I_O___s_e_t___s_s_l_(_) sets the internal SSL pointer of BIO bb to ssssll using the close flag cc. _B_I_O___g_e_t___s_s_l_(_) retrieves the SSL pointer of BIO bb, it can then be manip- ulated using the standard SSL library functions. _B_I_O___s_e_t___s_s_l___m_o_d_e_(_) sets the SSL BIO mode to cclliieenntt. If cclliieenntt is 1 client mode is set. If cclliieenntt is 0 server mode is set. _B_I_O___s_e_t___s_s_l___r_e_n_e_g_o_t_i_a_t_e___b_y_t_e_s_(_) sets the renegotiate byte count to nnuumm. When set after every nnuumm bytes of I/O (read and write) the SSL session is automatically renegotiated. nnuumm must be at least 512 bytes. _B_I_O___s_e_t___s_s_l___r_e_n_e_g_o_t_i_a_t_e___t_i_m_e_o_u_t_(_) sets the renegotiate timeout to sseecc-- oonnddss. When the renegotiate timeout elapses the session is automatically renegotiated. _B_I_O___g_e_t___n_u_m___r_e_n_e_g_o_t_i_a_t_e_s_(_) returns the total number of session renego- tiations due to I/O or timeout. _B_I_O___n_e_w___s_s_l_(_) allocates an SSL BIO using SSL_CTX ccttxx and using client mode if cclliieenntt is non zero. _B_I_O___n_e_w___s_s_l___c_o_n_n_e_c_t_(_) creates a new BIO chain consisting of an SSL BIO (using ccttxx) followed by a connect BIO. _B_I_O___n_e_w___b_u_f_f_e_r___s_s_l___c_o_n_n_e_c_t_(_) creates a new BIO chain consisting of a buffering BIO, an SSL BIO (using ccttxx) and a connect BIO. _B_I_O___s_s_l___c_o_p_y___s_e_s_s_i_o_n___i_d_(_) copies an SSL session id between BIO chains ffrroomm and ttoo. It does this by locating the SSL BIOs in each chain and calling _S_S_L___c_o_p_y___s_e_s_s_i_o_n___i_d_(_) on the internal SSL pointer. _B_I_O___s_s_l___s_h_u_t_d_o_w_n_(_) closes down an SSL connection on BIO chain bbiioo. It does this by locating the SSL BIO in the chain and calling _S_S_L___s_h_u_t_- _d_o_w_n_(_) on its internal SSL pointer. _B_I_O___d_o___h_a_n_d_s_h_a_k_e_(_) attempts to complete an SSL handshake on the sup- plied BIO and establish the SSL connection. It returns 1 if the connec- tion was established successfully. A zero or negative value is returned if the connection could not be established, the call _B_I_O___s_h_o_u_l_d___r_e_t_r_y_(_) should be used for non blocking connect BIOs to determine if the call should be retried. If an SSL connection has already been established this call has no effect. NNOOTTEESS SSL BIOs are exceptional in that if the underlying transport is non blocking they can still request a retry in exceptional circumstances. Specifically this will happen if a session renegotiation takes place during a _B_I_O___r_e_a_d_(_) operation, one case where this happens is when SGC or step up occurs. In OpenSSL 0.9.6 and later the SSL flag SSL_AUTO_RETRY can be set to disable this behaviour. That is when this flag is set an SSL BIO using a blocking transport will never request a retry. Since unknown _B_I_O___c_t_r_l_(_) operations are sent through filter BIOs the servers name and port can be set using _B_I_O___s_e_t___h_o_s_t_(_) on the BIO returned by _B_I_O___n_e_w___s_s_l___c_o_n_n_e_c_t_(_) without having to locate the connect BIO first. Applications do not have to call _B_I_O___d_o___h_a_n_d_s_h_a_k_e_(_) but may wish to do so to separate the handshake process from other I/O processing. RREETTUURRNN VVAALLUUEESS TBA EEXXAAMMPPLLEE This SSL/TLS client example, attempts to retrieve a page from an SSL/TLS web server. The I/O routines are identical to those of the unencrypted example in _B_I_O___s___c_o_n_n_e_c_t(3). BIO *sbio, *out; int len; char tmpbuf[1024]; SSL_CTX *ctx; SSL *ssl; ERR_load_crypto_strings(); ERR_load_SSL_strings(); OpenSSL_add_all_algorithms(); /* We would seed the PRNG here if the platform didn't * do it automatically */ ctx = SSL_CTX_new(SSLv23_client_method()); /* We'd normally set some stuff like the verify paths and * mode here because as things stand this will connect to * any server whose certificate is signed by any CA. */ sbio = BIO_new_ssl_connect(ctx); BIO_get_ssl(sbio, &ssl); if(!ssl) { fprintf(stderr, "Can't locate SSL pointer\n"); /* whatever ... */ } /* Don't want any retries */ SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); /* We might want to do other things with ssl here */ BIO_set_conn_hostname(sbio, "localhost:https"); out = BIO_new_fp(stdout, BIO_NOCLOSE); if(BIO_do_connect(sbio) <= 0) { fprintf(stderr, "Error connecting to server\n"); ERR_print_errors_fp(stderr); /* whatever ... */ } if(BIO_do_handshake(sbio) <= 0) { fprintf(stderr, "Error establishing SSL connection\n"); ERR_print_errors_fp(stderr); /* whatever ... */ } /* Could examine ssl here to get connection info */ BIO_puts(sbio, "GET / HTTP/1.0\n\n"); for(;;) { len = BIO_read(sbio, tmpbuf, 1024); if(len <= 0) break; BIO_write(out, tmpbuf, len); } BIO_free_all(sbio); BIO_free(out); Here is a simple server example. It makes use of a buffering BIO to allow lines to be read from the SSL BIO using BIO_gets. It creates a pseudo web page containing the actual request from a client and also echoes the request to standard output. BIO *sbio, *bbio, *acpt, *out; int len; char tmpbuf[1024]; SSL_CTX *ctx; SSL *ssl; ERR_load_crypto_strings(); ERR_load_SSL_strings(); OpenSSL_add_all_algorithms(); /* Might seed PRNG here */ ctx = SSL_CTX_new(SSLv23_server_method()); if (!SSL_CTX_use_certificate_file(ctx,"server.pem",SSL_FILETYPE_PEM) || !SSL_CTX_use_PrivateKey_file(ctx,"server.pem",SSL_FILETYPE_PEM) || !SSL_CTX_check_private_key(ctx)) { fprintf(stderr, "Error setting up SSL_CTX\n"); ERR_print_errors_fp(stderr); return 0; } /* Might do other things here like setting verify locations and * DH and/or RSA temporary key callbacks */ /* New SSL BIO setup as server */ sbio=BIO_new_ssl(ctx,0); BIO_get_ssl(sbio, &ssl); if(!ssl) { fprintf(stderr, "Can't locate SSL pointer\n"); /* whatever ... */ } /* Don't want any retries */ SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); /* Create the buffering BIO */ bbio = BIO_new(BIO_f_buffer()); /* Add to chain */ sbio = BIO_push(bbio, sbio); acpt=BIO_new_accept("4433"); /* By doing this when a new connection is established * we automatically have sbio inserted into it. The * BIO chain is now 'swallowed' by the accept BIO and * will be freed when the accept BIO is freed. */ BIO_set_accept_bios(acpt,sbio); out = BIO_new_fp(stdout, BIO_NOCLOSE); /* Setup accept BIO */ if(BIO_do_accept(acpt) <= 0) { fprintf(stderr, "Error setting up accept BIO\n"); ERR_print_errors_fp(stderr); return 0; } /* Now wait for incoming connection */ if(BIO_do_accept(acpt) <= 0) { fprintf(stderr, "Error in connection\n"); ERR_print_errors_fp(stderr); return 0; } /* We only want one connection so remove and free * accept BIO */ sbio = BIO_pop(acpt); BIO_free_all(acpt); if(BIO_do_handshake(sbio) <= 0) { fprintf(stderr, "Error in SSL handshake\n"); ERR_print_errors_fp(stderr); return 0; } BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n"); BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n"); BIO_puts(sbio, "--------------------------------------------------\r\n"); for(;;) { len = BIO_gets(sbio, tmpbuf, 1024); if(len <= 0) break; BIO_write(sbio, tmpbuf, len); BIO_write(out, tmpbuf, len); /* Look for blank line signifying end of headers*/ if((tmpbuf[0] == '\r') || (tmpbuf[0] == '\n')) break; } BIO_puts(sbio, "--------------------------------------------------\r\n"); BIO_puts(sbio, "\r\n"); /* Since there is a buffering BIO present we had better flush it */ BIO_flush(sbio); BIO_free_all(sbio); BBUUGGSS In OpenSSL versions before 1.0.0 the _B_I_O___p_o_p_(_) call was handled incor- rectly, the I/O BIO reference count was incorrectly incremented (instead of decremented) and dissociated with the SSL BIO even if the SSL BIO was not explicitly being popped (e.g. a pop higher up the chain). Applications which included workarounds for this bug (e.g. freeing BIOs more than once) should be modified to handle this fix or they may free up an already freed BIO. SSEEEE AALLSSOO TBA 1.0.1u 2016-09-22 BIO_f_ssl(3)