BIO_f_ssl(3)
BIO_f_ssl(3) 0.9.6h (2000-09-16) 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
BIO_f_ssl() 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 BIO_push() it is
automatically used as the SSL BIOs 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 will typically
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().
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BIO_f_ssl(3) 0.9.6h (2000-09-16) BIO_f_ssl(3)
BIO_set_ssl() sets the internal SSL pointer of BIO b to ssl
using the close flag c.
BIO_get_ssl() retrieves the SSL pointer of BIO b, it can
then be manipulated using the standard SSL library
functions.
BIO_set_ssl_mode() sets the SSL BIO mode to client. If
client is 1 client mode is set. If client is 0 server mode
is set.
BIO_set_ssl_renegotiate_bytes() 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.
num must be at least 512 bytes.
BIO_set_ssl_renegotiate_timeout() sets the renegotiate
timeout to seconds. When the renegotiate timeout elapses the
session is automatically renegotiated.
BIO_get_num_renegotiates() returns the total number of
session renegotiations due to I/O or timeout.
BIO_new_ssl() allocates an SSL BIO using SSL_CTX ctx and
using client mode if client is non zero.
BIO_new_ssl_connect() creates a new BIO chain consisting of
an SSL BIO (using ctx) followed by a connect BIO.
BIO_new_buffer_ssl_connect() creates a new BIO chain
consisting of a buffering BIO, an SSL BIO (using ctx) and a
connect BIO.
BIO_ssl_copy_session_id() 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.
BIO_ssl_shutdown() 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.
BIO_do_handshake() 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 call BIO_should_retry() 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
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BIO_f_ssl(3) 0.9.6h (2000-09-16) BIO_f_ssl(3)
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 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 BIO_ctrl() operations are sent through filter
BIOs the servers name and port can be set using
BIO_set_host() on the BIO returned by BIO_new_ssl_connect()
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);
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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;
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BIO_f_ssl(3) 0.9.6h (2000-09-16) BIO_f_ssl(3)
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);
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/* 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
Page 6 (printed 1/19/103)
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