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.
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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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791.1.1i                            2021-07-22            SSL_CTX_SET_CERT_CB(3)
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