1SSL_CTX_SET_CERT_CB(3)              OpenSSL             SSL_CTX_SET_CERT_CB(3)
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NAME

6       SSL_CTX_set_cert_cb, SSL_set_cert_cb - handle certificate callback
7       function
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SYNOPSIS

10        #include <openssl/ssl.h>
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12        void SSL_CTX_set_cert_cb(SSL_CTX *c, int (*cert_cb)(SSL *ssl, void *arg),
13                                 void *arg);
14        void SSL_set_cert_cb(SSL *s, int (*cert_cb)(SSL *ssl, void *arg), void *arg);
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16        int (*cert_cb)(SSL *ssl, void *arg);
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DESCRIPTION

19       SSL_CTX_set_cert_cb() and SSL_set_cert_cb() sets the cert_cb()
20       callback, arg value is pointer which is passed to the application
21       callback.
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23       When cert_cb() is NULL, no callback function is used.
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25       cert_cb() is the application defined callback. It is called before a
26       certificate will be used by a client or server. The callback can then
27       inspect the passed ssl structure and set or clear any appropriate
28       certificates. If the callback is successful it MUST return 1 even if no
29       certificates have been set. A zero is returned on error which will
30       abort the handshake with a fatal internal error alert. A negative
31       return value will suspend the handshake and the handshake function will
32       return immediately.  SSL_get_error(3) will return
33       SSL_ERROR_WANT_X509_LOOKUP to indicate, that the handshake was
34       suspended. The next call to the handshake function will again lead to
35       the call of cert_cb(). It is the job of the cert_cb() to store
36       information about the state of the last call, if required to continue.
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NOTES

39       An application will typically call SSL_use_certificate() and
40       SSL_use_PrivateKey() to set the end entity certificate and private key.
41       It can add intermediate and optionally the root CA certificates using
42       SSL_add1_chain_cert().
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44       It might also call SSL_certs_clear() to delete any certificates
45       associated with the SSL object.
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47       The certificate callback functionality supersedes the (largely broken)
48       functionality provided by the old client certificate callback
49       interface.  It is always called even is a certificate is already set so
50       the callback can modify or delete the existing certificate.
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52       A more advanced callback might examine the handshake parameters and set
53       whatever chain is appropriate. For example a legacy client supporting
54       only TLSv1.0 might receive a certificate chain signed using SHA1
55       whereas a TLSv1.2 or later client which advertises support for SHA256
56       could receive a chain using SHA256.
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58       Normal server sanity checks are performed on any certificates set by
59       the callback. So if an EC chain is set for a curve the client does not
60       support it will not be used.
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RETURN VALUES

63       SSL_CTX_set_cert_cb() and SSL_set_cert_cb() do not return values.
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SEE ALSO

66       ssl(7), SSL_use_certificate(3), SSL_add1_chain_cert(3),
67       SSL_get_client_CA_list(3), SSL_clear(3), SSL_free(3)
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70       Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved.
71
72       Licensed under the OpenSSL license (the "License").  You may not use
73       this file except in compliance with the License.  You can obtain a copy
74       in the file LICENSE in the source distribution or at
75       <https://www.openssl.org/source/license.html>.
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791.1.1q                            2022-07-21            SSL_CTX_SET_CERT_CB(3)
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