NAME¶
SSL_CTX_set_info_callback, SSL_CTX_get_info_callback, SSL_set_info_callback,
SSL_get_info_callback - handle information callback for SSL connections
SYNOPSIS¶
#include <openssl/ssl.h>
void SSL_CTX_set_info_callback(SSL_CTX *ctx, void (*callback)());
void (*SSL_CTX_get_info_callback(const SSL_CTX *ctx))();
void SSL_set_info_callback(SSL *ssl, void (*callback)());
void (*SSL_get_info_callback(const SSL *ssl))();
DESCRIPTION¶
SSL_CTX_set_info_callback() sets the
callback function, that can
be used to obtain state information for SSL objects created from
ctx
during connection setup and use. The setting for
ctx is overridden from
the setting for a specific SSL object, if specified. When
callback is
NULL, not callback function is used.
SSL_set_info_callback() sets the
callback function, that can be
used to obtain state information for
ssl during connection setup and
use. When
callback is NULL, the callback setting currently valid for
ctx is used.
SSL_CTX_get_info_callback() returns a pointer to the currently set
information callback function for
ctx.
SSL_get_info_callback() returns a pointer to the currently set
information callback function for
ssl.
NOTES¶
When setting up a connection and during use, it is possible to obtain state
information from the SSL/TLS engine. When set, an information callback
function is called whenever the state changes, an alert appears, or an error
occurs.
The callback function is called as
callback(SSL *ssl, int where, int
ret). The
where argument specifies information about where (in
which context) the callback function was called. If
ret is 0, an error
condition occurred. If an alert is handled, SSL_CB_ALERT is set and
ret
specifies the alert information.
where is a bitmask made up of the following bits:
- SSL_CB_LOOP
- Callback has been called to indicate state change inside a loop.
- SSL_CB_EXIT
- Callback has been called to indicate error exit of a handshake function.
(May be soft error with retry option for non-blocking setups.)
- SSL_CB_READ
- Callback has been called during read operation.
- SSL_CB_WRITE
- Callback has been called during write operation.
- SSL_CB_ALERT
- Callback has been called due to an alert being sent or received.
- SSL_CB_READ_ALERT (SSL_CB_ALERT|SSL_CB_READ)
- SSL_CB_WRITE_ALERT (SSL_CB_ALERT|SSL_CB_WRITE)
- SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT|SSL_CB_LOOP)
- SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT|SSL_CB_EXIT)
- SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT|SSL_CB_LOOP)
- SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT|SSL_CB_EXIT)
- SSL_CB_HANDSHAKE_START
- Callback has been called because a new handshake is started.
- SSL_CB_HANDSHAKE_DONE 0x20
- Callback has been called because a handshake is finished.
The current state information can be obtained using the
SSL_state_string(3) family of functions.
The
ret information can be evaluated using the
SSL_alert_type_string(3) family of functions.
RETURN VALUES¶
SSL_set_info_callback() does not provide diagnostic information.
SSL_get_info_callback() returns the current setting.
EXAMPLES¶
The following example callback function prints state strings, information about
alerts being handled and error messages to the
bio_err BIO.
void apps_ssl_info_callback(SSL *s, int where, int ret)
{
const char *str;
int w;
w=where& ~SSL_ST_MASK;
if (w & SSL_ST_CONNECT) str="SSL_connect";
else if (w & SSL_ST_ACCEPT) str="SSL_accept";
else str="undefined";
if (where & SSL_CB_LOOP)
{
BIO_printf(bio_err,"%s:%s\n",str,SSL_state_string_long(s));
}
else if (where & SSL_CB_ALERT)
{
str=(where & SSL_CB_READ)?"read":"write";
BIO_printf(bio_err,"SSL3 alert %s:%s:%s\n",
str,
SSL_alert_type_string_long(ret),
SSL_alert_desc_string_long(ret));
}
else if (where & SSL_CB_EXIT)
{
if (ret == 0)
BIO_printf(bio_err,"%s:failed in %s\n",
str,SSL_state_string_long(s));
else if (ret < 0)
{
BIO_printf(bio_err,"%s:error in %s\n",
str,SSL_state_string_long(s));
}
}
}
SEE ALSO¶
ssl(3),
SSL_state_string(3),
SSL_alert_type_string(3)