SSL_CTX_set_info_callback(3)SSL_CTX_set_info_callback(3)NAME
SSL_CTX_set_info_callback, SSL_CTX_get_info_callback - Handle informa‐
tion 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)(
SSL_CTX *ctx))( ); void SSL_set_info_callback(
SSL *ssl,
void (*callback)() ); void (*SSL_get_info_callback)(
SSL *ssl))( );
DESCRIPTION
The SSL_CTX_set_info_callback() function 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 over‐
ridden from the setting for a specific SSL object, if specified. When
callback is NULL, no callback function is used.
The SSL_set_info_callback() function 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.
The SSL_CTX_get_info_callback() function returns a pointer to the cur‐
rently set information callback function for ctx.
The SSL_get_info_callback() function 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 condi‐
tion occurred. If an alert is handled, SSL_CB_ALERT is set and ret
specifies the alert information.
The where argument 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_CON‐
NECT|SSL_CB_LOOP) SSL_CB_CONNECT_EXIT (SSL_ST_CON‐
NECT|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
The SSL_set_info_callback() function does not provide diagnostic infor‐
mation. The SSL_get_info_callback() function returns the current set‐
ting.
EXAMPLES
The following example callback function prints state strings, informa‐
tion 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=3Dwhere& ~SSL_ST_MASK;
if (w & SSL_ST_CONNECT) str=3D"SSL_connect";
else if (w & SSL_ST_ACCEPT) str=3D"SSL_accept";
else str=3D"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=3D(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 =3D=3D 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
Functions: ssl(3), SSL_get_info_callback(3), SSL_set_info_callback(3),
SSL_state_string(3), SSL_alert_type_string(3)SSL_CTX_set_info_callback(3)
