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Title "BIO_f_ssl 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
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 Header "SYNOPSIS" .Vb 2 #include <openssl/bio.h> #include <openssl/ssl.h> \& 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) \e BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_BYTES,num,NULL); #define BIO_set_ssl_renegotiate_timeout(b,seconds) \e BIO_ctrl(b,BIO_C_SET_SSL_RENEGOTIATE_TIMEOUT,seconds,NULL); #define BIO_get_num_renegotiates(b) \e 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) .Ve Header "DESCRIPTION" \fIBIO_f_ssl() returns the \s-1SSL BIO\s0 method. This is a filter \s-1BIO\s0 which is a wrapper round the OpenSSL \s-1SSL\s0 routines adding a \s-1BIO \s0\*(L"flavour\*(R" to \s-1SSL I/O. \s0

I/O performed on an \s-1SSL BIO\s0 communicates using the \s-1SSL\s0 protocol with the SSLs read and write BIOs. If an \s-1SSL\s0 connection is not established then an attempt is made to establish one on the first I/O call.

If a \s-1BIO\s0 is appended to an \s-1SSL BIO\s0 using BIO_push() it is automatically used as the \s-1SSL\s0 BIOs read and write BIOs.

Calling BIO_reset() on an \s-1SSL BIO\s0 closes down any current \s-1SSL\s0 connection by calling SSL_shutdown(). BIO_reset() is then sent to the next \s-1BIO\s0 in the chain: this will typically disconnect the underlying transport. The \s-1SSL BIO\s0 is then reset to the initial accept or connect state.

If the close flag is set when an \s-1SSL BIO\s0 is freed then the internal \s-1SSL\s0 structure is also freed using SSL_free().

\fIBIO_set_ssl() sets the internal \s-1SSL\s0 pointer of \s-1BIO \s0b to ssl using the close flag c.

\fIBIO_get_ssl() retrieves the \s-1SSL\s0 pointer of \s-1BIO \s0b, it can then be manipulated using the standard \s-1SSL\s0 library functions.

\fIBIO_set_ssl_mode() sets the \s-1SSL BIO\s0 mode to client. If client is 1 client mode is set. If client is 0 server mode is set.

\fIBIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count to num. When set after every num bytes of I/O (read and write) the \s-1SSL\s0 session is automatically renegotiated. num must be at least 512 bytes.

\fIBIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout to \fBseconds. When the renegotiate timeout elapses the session is automatically renegotiated.

\fIBIO_get_num_renegotiates() returns the total number of session renegotiations due to I/O or timeout.

\fIBIO_new_ssl() allocates an \s-1SSL BIO\s0 using \s-1SSL_CTX \s0ctx and using client mode if client is non zero.

\fIBIO_new_ssl_connect() creates a new \s-1BIO\s0 chain consisting of an \s-1SSL BIO \s0(using ctx) followed by a connect \s-1BIO.\s0

\fIBIO_new_buffer_ssl_connect() creates a new \s-1BIO\s0 chain consisting of a buffering \s-1BIO,\s0 an \s-1SSL BIO \s0(using ctx) and a connect \s-1BIO.\s0

\fIBIO_ssl_copy_session_id() copies an \s-1SSL\s0 session id between \s-1BIO\s0 chains from and to. It does this by locating the \s-1SSL\s0 BIOs in each chain and calling SSL_copy_session_id() on the internal \s-1SSL\s0 pointer.

\fIBIO_ssl_shutdown() closes down an \s-1SSL\s0 connection on \s-1BIO\s0 chain bio. It does this by locating the \s-1SSL BIO\s0 in the chain and calling SSL_shutdown() on its internal \s-1SSL\s0 pointer.

\fIBIO_do_handshake() attempts to complete an \s-1SSL\s0 handshake on the supplied \s-1BIO\s0 and establish the \s-1SSL\s0 connection. It returns 1 if the connection was established successfully. A zero or negative value is returned if the connection could not be established, the call BIO_should_retry() should be used for non blocking connect BIOs to determine if the call should be retried. If an \s-1SSL\s0 connection has already been established this call has no effect.

Header "NOTES" \s-1SSL\s0 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 BIO_read() operation, one case where this happens is when \s-1SGC\s0 or step up occurs.

In OpenSSL 0.9.6 and later the \s-1SSL\s0 flag \s-1SSL_AUTO_RETRY\s0 can be set to disable this behaviour. That is when this flag is set an \s-1SSL BIO\s0 using a blocking transport will never request a retry.

Since unknown BIO_ctrl() operations are sent through filter BIOs the servers name and port can be set using BIO_set_host() on the \s-1BIO\s0 returned by BIO_new_ssl_connect() without having to locate the connect \s-1BIO\s0 first.

Applications do not have to call BIO_do_handshake() but may wish to do so to separate the handshake process from other I/O processing.

Header "RETURN VALUES" \s-1TBA\s0 Header "EXAMPLE" This \s-1SSL/TLS\s0 client example, attempts to retrieve a page from an \s-1SSL/TLS\s0 web server. The I/O routines are identical to those of the unencrypted example in BIO_s_connect\|(3).

.Vb 5 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\*(Aqt * do it automatically */ \& ctx = SSL_CTX_new(SSLv23_client_method()); \& /* We\*(Aqd 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\*(Aqt locate SSL pointer\en"); /* whatever ... */ } \& /* Don\*(Aqt 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\en"); ERR_print_errors_fp(stderr); /* whatever ... */ } \& if(BIO_do_handshake(sbio) <= 0) { fprintf(stderr, "Error establishing SSL connection\en"); ERR_print_errors_fp(stderr); /* whatever ... */ } \& /* Could examine ssl here to get connection info */ \& BIO_puts(sbio, "GET / HTTP/1.0\en\en"); for(;;) { len = BIO_read(sbio, tmpbuf, 1024); if(len <= 0) break; BIO_write(out, tmpbuf, len); } BIO_free_all(sbio); BIO_free(out); .Ve

Here is a simple server example. It makes use of a buffering \s-1BIO\s0 to allow lines to be read from the \s-1SSL BIO\s0 using BIO_gets. It creates a pseudo web page containing the actual request from a client and also echoes the request to standard output.

.Vb 5 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\en"); 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\*(Aqt locate SSL pointer\en"); /* whatever ... */ } \& /* Don\*(Aqt 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 \*(Aqswallowed\*(Aq 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\en"); ERR_print_errors_fp(stderr); return 0; } \& /* Now wait for incoming connection */ if(BIO_do_accept(acpt) <= 0) { fprintf(stderr, "Error in connection\en"); 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\en"); ERR_print_errors_fp(stderr); return 0; } \& BIO_puts(sbio, "HTTP/1.0 200 OK\er\enContent-type: text/plain\er\en\er\en"); BIO_puts(sbio, "\er\enConnection Established\er\enRequest headers:\er\en"); BIO_puts(sbio, "--------------------------------------------------\er\en"); \& 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] == \*(Aq\er\*(Aq) || (tmpbuf[0] == \*(Aq\en\*(Aq)) break; } \& BIO_puts(sbio, "--------------------------------------------------\er\en"); BIO_puts(sbio, "\er\en"); \& /* Since there is a buffering BIO present we had better flush it */ BIO_flush(sbio); \& BIO_free_all(sbio); .Ve

Header "SEE ALSO" \s-1TBA\s0