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.\" ========================================================================
.\"
.IX Title "SSL_CTX_set_info_callback 3"
.TH SSL_CTX_set_info_callback 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "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
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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))();
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBSSL_CTX_set_info_callback()\fR sets the \fBcallback\fR function, that can be used to
obtain state information for \s-1SSL\s0 objects created from \fBctx\fR during connection
setup and use. The setting for \fBctx\fR is overridden from the setting for
a specific \s-1SSL\s0 object, if specified.
When \fBcallback\fR is \s-1NULL,\s0 not callback function is used.
.PP
\&\fBSSL_set_info_callback()\fR sets the \fBcallback\fR function, that can be used to
obtain state information for \fBssl\fR during connection setup and use.
When \fBcallback\fR is \s-1NULL,\s0 the callback setting currently valid for
\&\fBctx\fR is used.
.PP
\&\fBSSL_CTX_get_info_callback()\fR returns a pointer to the currently set information
callback function for \fBctx\fR.
.PP
\&\fBSSL_get_info_callback()\fR returns a pointer to the currently set information
callback function for \fBssl\fR.
.SH "NOTES"
.IX Header "NOTES"
When setting up a connection and during use, it is possible to obtain state
information from the \s-1SSL/TLS\s0 engine. When set, an information callback function
is called whenever the state changes, an alert appears, or an error occurs.
.PP
The callback function is called as \fBcallback(\s-1SSL\s0 *ssl, int where, int ret)\fR.
The \fBwhere\fR argument specifies information about where (in which context)
the callback function was called. If \fBret\fR is 0, an error condition occurred.
If an alert is handled, \s-1SSL_CB_ALERT\s0 is set and \fBret\fR specifies the alert
information.
.PP
\&\fBwhere\fR is a bitmask made up of the following bits:
.IP "\s-1SSL_CB_LOOP\s0" 4
.IX Item "SSL_CB_LOOP"
Callback has been called to indicate state change inside a loop.
.IP "\s-1SSL_CB_EXIT\s0" 4
.IX Item "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.)
.IP "\s-1SSL_CB_READ\s0" 4
.IX Item "SSL_CB_READ"
Callback has been called during read operation.
.IP "\s-1SSL_CB_WRITE\s0" 4
.IX Item "SSL_CB_WRITE"
Callback has been called during write operation.
.IP "\s-1SSL_CB_ALERT\s0" 4
.IX Item "SSL_CB_ALERT"
Callback has been called due to an alert being sent or received.
.IP "\s-1SSL_CB_READ_ALERT\s0               (SSL_CB_ALERT|SSL_CB_READ)" 4
.IX Item "SSL_CB_READ_ALERT (SSL_CB_ALERT|SSL_CB_READ)"
.PD 0
.IP "\s-1SSL_CB_WRITE_ALERT\s0              (SSL_CB_ALERT|SSL_CB_WRITE)" 4
.IX Item "SSL_CB_WRITE_ALERT (SSL_CB_ALERT|SSL_CB_WRITE)"
.IP "\s-1SSL_CB_ACCEPT_LOOP\s0              (SSL_ST_ACCEPT|SSL_CB_LOOP)" 4
.IX Item "SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT|SSL_CB_LOOP)"
.IP "\s-1SSL_CB_ACCEPT_EXIT\s0              (SSL_ST_ACCEPT|SSL_CB_EXIT)" 4
.IX Item "SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT|SSL_CB_EXIT)"
.IP "\s-1SSL_CB_CONNECT_LOOP\s0             (SSL_ST_CONNECT|SSL_CB_LOOP)" 4
.IX Item "SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT|SSL_CB_LOOP)"
.IP "\s-1SSL_CB_CONNECT_EXIT\s0             (SSL_ST_CONNECT|SSL_CB_EXIT)" 4
.IX Item "SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT|SSL_CB_EXIT)"
.IP "\s-1SSL_CB_HANDSHAKE_START\s0" 4
.IX Item "SSL_CB_HANDSHAKE_START"
.PD
Callback has been called because a new handshake is started.
.IP "\s-1SSL_CB_HANDSHAKE_DONE\s0           0x20" 4
.IX Item "SSL_CB_HANDSHAKE_DONE 0x20"
Callback has been called because a handshake is finished.
.PP
The current state information can be obtained using the
\&\fBSSL_state_string\fR\|(3) family of functions.
.PP
The \fBret\fR information can be evaluated using the
\&\fBSSL_alert_type_string\fR\|(3) family of functions.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBSSL_set_info_callback()\fR does not provide diagnostic information.
.PP
\&\fBSSL_get_info_callback()\fR returns the current setting.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
The following example callback function prints state strings, information
about alerts being handled and error messages to the \fBbio_err\fR \s-1BIO.\s0
.PP
.Vb 4
\& 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\en",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\en",
\&                        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\en",
\&                                str,SSL_state_string_long(s));
\&                else if (ret < 0)
\&                        {
\&                        BIO_printf(bio_err,"%s:error in %s\en",
\&                                str,SSL_state_string_long(s));
\&                        }
\&                }
\&        }
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBssl\fR\|(3), \fBSSL_state_string\fR\|(3),
\&\fBSSL_alert_type_string\fR\|(3)

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