1=pod 2 3=head1 NAME 4 5SSL_CTX_set_info_callback, 6SSL_CTX_get_info_callback, 7SSL_set_info_callback, 8SSL_get_info_callback 9- handle information callback for SSL connections 10 11=head1 SYNOPSIS 12 13 #include <openssl/ssl.h> 14 15 void SSL_CTX_set_info_callback(SSL_CTX *ctx, void (*callback)()); 16 void (*SSL_CTX_get_info_callback(const SSL_CTX *ctx))(); 17 18 void SSL_set_info_callback(SSL *ssl, void (*callback)()); 19 void (*SSL_get_info_callback(const SSL *ssl))(); 20 21=head1 DESCRIPTION 22 23SSL_CTX_set_info_callback() sets the B<callback> function, that can be used to 24obtain state information for SSL objects created from B<ctx> during connection 25setup and use. The setting for B<ctx> is overridden from the setting for 26a specific SSL object, if specified. 27When B<callback> is NULL, no callback function is used. 28 29SSL_set_info_callback() sets the B<callback> function, that can be used to 30obtain state information for B<ssl> during connection setup and use. 31When B<callback> is NULL, the callback setting currently valid for 32B<ctx> is used. 33 34SSL_CTX_get_info_callback() returns a pointer to the currently set information 35callback function for B<ctx>. 36 37SSL_get_info_callback() returns a pointer to the currently set information 38callback function for B<ssl>. 39 40=head1 NOTES 41 42When setting up a connection and during use, it is possible to obtain state 43information from the SSL/TLS engine. When set, an information callback function 44is called whenever a significant event occurs such as: the state changes, 45an alert appears, or an error occurs. 46 47The callback function is called as B<callback(SSL *ssl, int where, int ret)>. 48The B<where> argument specifies information about where (in which context) 49the callback function was called. If B<ret> is 0, an error condition occurred. 50If an alert is handled, SSL_CB_ALERT is set and B<ret> specifies the alert 51information. 52 53B<where> is a bitmask made up of the following bits: 54 55=over 4 56 57=item SSL_CB_LOOP 58 59Callback has been called to indicate state change or some other significant 60state machine event. This may mean that the callback gets invoked more than once 61per state in some situations. 62 63=item SSL_CB_EXIT 64 65Callback has been called to indicate exit of a handshake function. This will 66happen after the end of a handshake, but may happen at other times too such as 67on error or when IO might otherwise block and non-blocking is being used. 68 69=item SSL_CB_READ 70 71Callback has been called during read operation. 72 73=item SSL_CB_WRITE 74 75Callback has been called during write operation. 76 77=item SSL_CB_ALERT 78 79Callback has been called due to an alert being sent or received. 80 81=item SSL_CB_READ_ALERT (SSL_CB_ALERT|SSL_CB_READ) 82 83=item SSL_CB_WRITE_ALERT (SSL_CB_ALERT|SSL_CB_WRITE) 84 85=item SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT|SSL_CB_LOOP) 86 87=item SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT|SSL_CB_EXIT) 88 89=item SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT|SSL_CB_LOOP) 90 91=item SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT|SSL_CB_EXIT) 92 93=item SSL_CB_HANDSHAKE_START 94 95Callback has been called because a new handshake is started. In TLSv1.3 this is 96also used for the start of post-handshake message exchanges such as for the 97exchange of session tickets, or for key updates. It also occurs when resuming a 98handshake following a pause to handle early data. 99 100=item SSL_CB_HANDSHAKE_DONE 0x20 101 102Callback has been called because a handshake is finished. In TLSv1.3 this is 103also used at the end of an exchange of post-handshake messages such as for 104session tickets or key updates. It also occurs if the handshake is paused to 105allow the exchange of early data. 106 107=back 108 109The current state information can be obtained using the 110L<SSL_state_string(3)> family of functions. 111 112The B<ret> information can be evaluated using the 113L<SSL_alert_type_string(3)> family of functions. 114 115=head1 RETURN VALUES 116 117SSL_set_info_callback() does not provide diagnostic information. 118 119SSL_get_info_callback() returns the current setting. 120 121=head1 EXAMPLES 122 123The following example callback function prints state strings, information 124about alerts being handled and error messages to the B<bio_err> BIO. 125 126 void apps_ssl_info_callback(SSL *s, int where, int ret) 127 { 128 const char *str; 129 int w = where & ~SSL_ST_MASK; 130 131 if (w & SSL_ST_CONNECT) 132 str = "SSL_connect"; 133 else if (w & SSL_ST_ACCEPT) 134 str = "SSL_accept"; 135 else 136 str = "undefined"; 137 138 if (where & SSL_CB_LOOP) { 139 BIO_printf(bio_err, "%s:%s\n", str, SSL_state_string_long(s)); 140 } else if (where & SSL_CB_ALERT) { 141 str = (where & SSL_CB_READ) ? "read" : "write"; 142 BIO_printf(bio_err, "SSL3 alert %s:%s:%s\n", str, 143 SSL_alert_type_string_long(ret), 144 SSL_alert_desc_string_long(ret)); 145 } else if (where & SSL_CB_EXIT) { 146 if (ret == 0) { 147 BIO_printf(bio_err, "%s:failed in %s\n", 148 str, SSL_state_string_long(s)); 149 } else if (ret < 0) { 150 BIO_printf(bio_err, "%s:error in %s\n", 151 str, SSL_state_string_long(s)); 152 } 153 } 154 } 155 156=head1 SEE ALSO 157 158L<ssl(7)>, L<SSL_state_string(3)>, 159L<SSL_alert_type_string(3)> 160 161=head1 COPYRIGHT 162 163Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved. 164 165Licensed under the OpenSSL license (the "License"). You may not use 166this file except in compliance with the License. You can obtain a copy 167in the file LICENSE in the source distribution or at 168L<https://www.openssl.org/source/license.html>. 169 170=cut 171