1SSL_CTX_SET_INFO_CALLBACK(3)        OpenSSL       SSL_CTX_SET_INFO_CALLBACK(3)
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NAME

6       SSL_CTX_set_info_callback, SSL_CTX_get_info_callback,
7       SSL_set_info_callback, SSL_get_info_callback - handle information
8       callback for SSL connections
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SYNOPSIS

11        #include <openssl/ssl.h>
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13        void SSL_CTX_set_info_callback(SSL_CTX *ctx, void (*callback)());
14        void (*SSL_CTX_get_info_callback(const SSL_CTX *ctx))();
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16        void SSL_set_info_callback(SSL *ssl, void (*callback)());
17        void (*SSL_get_info_callback(const SSL *ssl))();
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DESCRIPTION

20       SSL_CTX_set_info_callback() sets the callback function, that can be
21       used to obtain state information for SSL objects created from ctx
22       during connection setup and use. The setting for ctx is overridden from
23       the setting for a specific SSL object, if specified.  When callback is
24       NULL, no callback function is used.
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26       SSL_set_info_callback() sets the callback function, that can be used to
27       obtain state information for ssl during connection setup and use.  When
28       callback is NULL, the callback setting currently valid for ctx is used.
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30       SSL_CTX_get_info_callback() returns a pointer to the currently set
31       information callback function for ctx.
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33       SSL_get_info_callback() returns a pointer to the currently set
34       information callback function for ssl.
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NOTES

37       When setting up a connection and during use, it is possible to obtain
38       state information from the SSL/TLS engine. When set, an information
39       callback function is called whenever a significant event occurs such
40       as: the state changes, an alert appears, or an error occurs.
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42       The callback function is called as callback(SSL *ssl, int where, int
43       ret).  The where argument specifies information about where (in which
44       context) the callback function was called. If ret is 0, an error
45       condition occurred.  If an alert is handled, SSL_CB_ALERT is set and
46       ret specifies the alert information.
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48       where is a bit mask made up of the following bits:
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50       SSL_CB_LOOP
51           Callback has been called to indicate state change or some other
52           significant state machine event. This may mean that the callback
53           gets invoked more than once per state in some situations.
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55       SSL_CB_EXIT
56           Callback has been called to indicate exit of a handshake function.
57           This will happen after the end of a handshake, but may happen at
58           other times too such as on error or when IO might otherwise block
59           and nonblocking is being used.
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61       SSL_CB_READ
62           Callback has been called during read operation.
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64       SSL_CB_WRITE
65           Callback has been called during write operation.
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67       SSL_CB_ALERT
68           Callback has been called due to an alert being sent or received.
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70       SSL_CB_READ_ALERT               (SSL_CB_ALERT|SSL_CB_READ)
71       SSL_CB_WRITE_ALERT              (SSL_CB_ALERT|SSL_CB_WRITE)
72       SSL_CB_ACCEPT_LOOP              (SSL_ST_ACCEPT|SSL_CB_LOOP)
73       SSL_CB_ACCEPT_EXIT              (SSL_ST_ACCEPT|SSL_CB_EXIT)
74       SSL_CB_CONNECT_LOOP             (SSL_ST_CONNECT|SSL_CB_LOOP)
75       SSL_CB_CONNECT_EXIT             (SSL_ST_CONNECT|SSL_CB_EXIT)
76       SSL_CB_HANDSHAKE_START
77           Callback has been called because a new handshake is started. It
78           also occurs when resuming a handshake following a pause to handle
79           early data.
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81       SSL_CB_HANDSHAKE_DONE
82           Callback has been called because a handshake is finished.  It also
83           occurs if the handshake is paused to allow the exchange of early
84           data.
85
86       The current state information can be obtained using the
87       SSL_state_string(3) family of functions.
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89       The ret information can be evaluated using the SSL_alert_type_string(3)
90       family of functions.
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RETURN VALUES

93       SSL_set_info_callback() does not provide diagnostic information.
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95       SSL_get_info_callback() returns the current setting.
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EXAMPLES

98       The following example callback function prints state strings,
99       information about alerts being handled and error messages to the
100       bio_err BIO.
101
102        void apps_ssl_info_callback(SSL *s, int where, int ret)
103        {
104            const char *str;
105            int w = where & ~SSL_ST_MASK;
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107            if (w & SSL_ST_CONNECT)
108                str = "SSL_connect";
109            else if (w & SSL_ST_ACCEPT)
110                str = "SSL_accept";
111            else
112                str = "undefined";
113
114            if (where & SSL_CB_LOOP) {
115                BIO_printf(bio_err, "%s:%s\n", str, SSL_state_string_long(s));
116            } else if (where & SSL_CB_ALERT) {
117                str = (where & SSL_CB_READ) ? "read" : "write";
118                BIO_printf(bio_err, "SSL3 alert %s:%s:%s\n", str,
119                           SSL_alert_type_string_long(ret),
120                           SSL_alert_desc_string_long(ret));
121            } else if (where & SSL_CB_EXIT) {
122                if (ret == 0) {
123                    BIO_printf(bio_err, "%s:failed in %s\n",
124                               str, SSL_state_string_long(s));
125                } else if (ret < 0) {
126                    BIO_printf(bio_err, "%s:error in %s\n",
127                               str, SSL_state_string_long(s));
128                }
129            }
130        }
131

SEE ALSO

133       ssl(7), SSL_state_string(3), SSL_alert_type_string(3)
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136       Copyright 2001-2020 The OpenSSL Project Authors. All Rights Reserved.
137
138       Licensed under the OpenSSL license (the "License").  You may not use
139       this file except in compliance with the License.  You can obtain a copy
140       in the file LICENSE in the source distribution or at
141       <https://www.openssl.org/source/license.html>.
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1451.1.1i                            2021-07-22      SSL_CTX_SET_INFO_CALLBACK(3)
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