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BIO_f_ssl(3)
NAME
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
SYNOPSIS
#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) \
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)
DESCRIPTION
The BIO_f_ssl() function returns the SSL BIO method. This is a filter BIO
which is a wrapper round the OpenSSL SSL routines adding a BIO "flavor" to
SSL I/O.
I/O performed on an SSL BIO communicates using the SSL protocol with the
SSL's 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 the BIO_push() function, it is
automatically used as the SSL BIO's read and write BIOs.
Calling BIO_reset() on an SSL BIO closes down any current SSL connection by
calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in the
chain. This typically will disconnect the underlying transport. 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 SSL_free().
The BIO_set_ssl() function sets the internal SSL pointer of BIO b to ssl
using the close (c) option .
The BIO_get_ssl() function retrieves the SSL pointer of BIO b. It then can
be manipulated using the standard SSL library functions.
The BIO_set_ssl_mode() function sets the SSL BIO mode to client. If client
is 1, client mode is set. If client is 0, server mode is set.
The BIO_set_ssl_renegotiate_bytes() function sets the renegotiate byte
count to num. When set after every num bytes of I/O (read and write) the
SSL session is automatically renegotiated. The num value must be at least
512 bytes.
The BIO_set_ssl_renegotiate_timeout() function sets the renegotiate timeout
to seconds. When the renegotiate timeout elapses the session is
automatically renegotiated.
The BIO_get_num_renegotiates() function returns the total number of session
renegotiations due to I/O or timeout.
The BIO_new_ssl() function allocates an SSL BIO using SSL_CTX ctx and using
client mode if client is not zero.
The BIO_new_ssl_connect() funciton creates a new BIO chain consisting of an
SSL BIO (using ctx) followed by a connect BIO.
The BIO_new_buffer_ssl_connect() function creates a new BIO chain
consisting of a buffering BIO, an SSL BIO (using ctx), and a connect BIO.
The BIO_ssl_copy_session_id() function copies an SSL session id between
BIO chains from and to. It does this by locating the SSL BIOs in each chain
and calling SSL_copy_session_id() on the internal SSL pointer.
The BIO_ssl_shutdown() function closes down an SSL connection on BIO chain
bio. It does this by locating the SSL BIO in the chain and calling
SSL_shutdown() on its internal SSL pointer.
The BIO_do_handshake() function attempts to complete an SSL handshake on
the supplied BIO and establish the SSL 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 BIO_should_retry()
function 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.
NOTES
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 BIO_read() operation, one case where this happens is when SGC or step up
occurs.
In OpenSSL 0.9.6 and later the SSL_AUTO_RETRY option can be set to disable
this behavior. That is, when this flag is set, an SSL BIO 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 the BIO_set_host() function on the
BIO returned by the BIO_new_ssl_connect() function without having to locate
the connect BIO 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.
RETURN VALUES
TBA
EXAMPLE
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 BIO_s_connect(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);
This server example 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/html\r\n\r\n");
BIO_puts(sbio, "<pre>\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, "</pre>\r\n");
/* Since there is a buffering BIO present we had better flush it */
BIO_flush(sbio);
BIO_free_all(sbio);
SEE ALSO
TBA
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