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
#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)
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.
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.
TBA
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);
TBA
BIO_f_ssl(3)
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