SSL_set_info_callback, SSL_get_info_callback - handle information call-
back for SSL connections
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))();
SSL_CTX_set_info_callback() sets the callback function, that can be
used to obtain state information for SSL objects created from ctx dur-
ing 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 informa-
tion callback function for ssl.
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.
where is a bitmask made up of the following bits:
Callback has been called to indicate state change inside a loop.
Callback has been called to indicate error exit of a handshake
function. (May be soft error with retry option for non-blocking
Callback has been called during read operation.
Callback has been called during write operation.
Callback has been called due to an alert being sent or received.
Callback has been called because a new handshake is started.
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.
SSL_set_info_callback() does not provide diagnostic information.
SSL_get_info_callback() returns the current setting.
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;
if (w & SSL_ST_CONNECT) str="SSL_connect";
else if (w & SSL_ST_ACCEPT) str="SSL_accept";
if (where & SSL_CB_LOOP)
else if (where & SSL_CB_ALERT)
str=(where & SSL_CB_READ)?"read":"write";
BIO_printf(bio_err,"SSL3 alert %s:%s:%s\n",
else if (where & SSL_CB_EXIT)
if (ret == 0)
BIO_printf(bio_err,"%s:failed in %s\n",
else if (ret < 0)
BIO_printf(bio_err,"%s:error in %s\n",
ssl(3), SSL_state_string(3), SSL_alert_type_string(3)
1.0.2t 2019-09-10 SSL_CTX_set_info_callback(3)
See also SSL_CTX_get_info_callback(3)
See also SSL_CTX_set_info_callback(3)
See also SSL_get_info_callback(3)
Man(1) output converted with