- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- BUGS
- SEE ALSO
- COPYRIGHT

# NAME

SSL_CTX_set_client_cert_cb, SSL_CTX_get_client_cert_cb - handle client certificate callback function

# SYNOPSIS

     #include <openssl/ssl.h>

     void SSL_CTX_set_client_cert_cb(SSL_CTX *ctx, int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey));
     int (*SSL_CTX_get_client_cert_cb(SSL_CTX *ctx))(SSL *ssl, X509 **x509, EVP_PKEY **pkey);
     int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey);

# DESCRIPTION

SSL_CTX_set_client_cert_cb() sets the client_cert_cb() callback, that is called when a client certificate is requested by a server and no certificate was yet set for the SSL object.

When client_cert_cb() is NULL, no callback function is used.

SSL_CTX_get_client_cert_cb() returns a pointer to the currently set callback function.

client_cert_cb() is the application defined callback. If it wants to set a certificate, a certificate/private key combination must be set using the x509 and pkey arguments and "1" must be returned. The certificate will be installed into ssl, see the NOTES and BUGS sections. If no certificate should be set, "0" has to be returned and no certificate will be sent. A negative return value will suspend the handshake and the handshake function will return immediately. NOTES

During a handshake (or renegotiation) a server may request a certificate from the client. A client certificate must only be sent, when the server did send the request.

When a certificate was set using the SSL_clear(3). If the callback returns no certificate, the OpenSSL library will not send a certificate.

# BUGS

The client_cert_cb() cannot return a complete certificate chain, it can only return one client certificate. If the chain only has a length of 2, the root CA certificate may be omitted according to the TLS standard and thus a standard conforming answer can be sent to the server. For a longer chain, the client must send the complete chain (with the option to leave out the root CA certificate). This can only be accomplished by either adding the intermediate CA certificates into the trusted certificate store for the SSL_CTX object (resulting in having to add CA certificates that otherwise maybe would not be trusted), or by adding the chain certificates using the SSL_clear(3) is being called. It is therefore mandatory to destroy the SSL object using SEE ALSO

SSL_CTX_use_certificate(3), SSL_get_client_CA_list(3), SSL_free(3)

# COPYRIGHT

Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.