plucky (3) SSL_CTX_set_info_callback.3ssl.gz

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) (const SSL *ssl, int type, int val));

        void (*SSL_CTX_get_info_callback(SSL_CTX *ctx)) (const SSL *ssl, int type, int val);

        void SSL_set_info_callback(SSL *ssl,
                                   void (*callback) (const SSL *ssl, int type, int val));

        void (*SSL_get_info_callback(const SSL *ssl)) (const SSL *ssl, int type, int val);

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, no 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 a significant event occurs such as:
       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 bit-mask made up of the following bits:

       SSL_CB_LOOP
           Callback has been called to indicate state change or some other significant state machine event. This
           may mean that the callback gets invoked more than once per state in some situations.

       SSL_CB_EXIT
           Callback has been called to indicate exit of a handshake function. This will happen after the end of
           a handshake, but may happen at other times too such as on error or when IO might otherwise block and
           nonblocking is being used.

       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. It also occurs when resuming a handshake
           following a pause to handle early data.

       SSL_CB_HANDSHAKE_DONE
           Callback has been called because a handshake is finished.  It also occurs if the handshake is paused
           to allow the exchange of early data.

       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(const SSL *s, int where, int ret)
        {
            const char *str;
            int 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(7), SSL_state_string(3), SSL_alert_type_string(3)

COPYRIGHT

       Copyright 2001-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance
       with the License.  You can obtain a copy in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.