1=pod
2
3=head1 NAME
4
5SSL_CTX_set_client_cert_cb, SSL_CTX_get_client_cert_cb - handle client certificate callback function
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 void SSL_CTX_set_client_cert_cb(SSL_CTX *ctx, int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey));
12 int (*SSL_CTX_get_client_cert_cb(SSL_CTX *ctx))(SSL *ssl, X509 **x509, EVP_PKEY **pkey);
13 int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey);
14
15=head1 DESCRIPTION
16
17SSL_CTX_set_client_cert_cb() sets the B<client_cert_cb()> callback, that is
| 1=pod
2
3=head1 NAME
4
5SSL_CTX_set_client_cert_cb, SSL_CTX_get_client_cert_cb - handle client certificate callback function
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 void SSL_CTX_set_client_cert_cb(SSL_CTX *ctx, int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey));
12 int (*SSL_CTX_get_client_cert_cb(SSL_CTX *ctx))(SSL *ssl, X509 **x509, EVP_PKEY **pkey);
13 int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey);
14
15=head1 DESCRIPTION
16
17SSL_CTX_set_client_cert_cb() sets the B<client_cert_cb()> callback, that is
|
18called when a client certificate is requested by a server.
19When B<client_cert_cb()> is NULL, not callback function is used.
| 18called when a client certificate is requested by a server and no certificate
19was yet set for the SSL object.
|
20
| 20
|
| 21When B<client_cert_cb()> is NULL, no callback function is used.
22
|
21SSL_CTX_get_client_cert_cb() returns a pointer to the currently set callback
22function.
23
24client_cert_cb() is the application defined callback. If it wants to
25set a certificate, a certificate/private key combination must be set
26using the B<x509> and B<pkey> arguments and "1" must be returned. The
27certificate will be installed into B<ssl>, see the NOTES and BUGS sections.
| 23SSL_CTX_get_client_cert_cb() returns a pointer to the currently set callback
24function.
25
26client_cert_cb() is the application defined callback. If it wants to
27set a certificate, a certificate/private key combination must be set
28using the B<x509> and B<pkey> arguments and "1" must be returned. The
29certificate will be installed into B<ssl>, see the NOTES and BUGS sections.
|
28If no certificate should be set, "0" has to be returned and the default
29certificate will be sent. A fatal error can be indicated by returning
30a negative value, in which case the handshake will be canceled.
| 30If no certificate should be set, "0" has to be returned and no certificate
31will be sent. A negative return value will suspend the handshake and the
32handshake function will return immediatly. L<SSL_get_error(3)|SSL_get_error(3)>
33will return SSL_ERROR_WANT_X509_LOOKUP to indicate, that the handshake was
34suspended. The next call to the handshake function will again lead to the call
35of client_cert_cb(). It is the job of the client_cert_cb() to store information
36about the state of the last call, if required to continue.
|
31
32=head1 NOTES
33
34During a handshake (or renegotiation) a server may request a certificate
35from the client. A client certificate must only be sent, when the server
36did send the request.
37
| 37
38=head1 NOTES
39
40During a handshake (or renegotiation) a server may request a certificate
41from the client. A client certificate must only be sent, when the server
42did send the request.
43
|
38When no callback function is set, an OpenSSL client will send the certificate
39that was set using the
40L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)> family of functions.
41The TLS standard requires that only a certificate is sent, if it matches
42the list of acceptable CAs sent by the server. This constraint is
43violated by the default behavior of the OpenSSL library. Using the
44callback function it is possible to implement a proper selection routine
45or to allow a user interaction to choose the certificate to be sent.
46The callback function can obtain the list of acceptable CAs using the
47L<SSL_get_client_CA_list(3)|SSL_get_client_CA_list(3)> function.
| 44When a certificate was set using the
45L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)> family of functions,
46it will be sent to the server. The TLS standard requires that only a
47certificate is sent, if it matches the list of acceptable CAs sent by the
48server. This constraint is violated by the default behavior of the OpenSSL
49library. Using the callback function it is possible to implement a proper
50selection routine or to allow a user interaction to choose the certificate to
51be sent.
|
48
| 52
|
49If a callback function is defined, the callback function will be called.
| 53If a callback function is defined and no certificate was yet defined for the
54SSL object, the callback function will be called.
|
50If the callback function returns a certificate, the OpenSSL library
51will try to load the private key and certificate data into the SSL
| 55If the callback function returns a certificate, the OpenSSL library
56will try to load the private key and certificate data into the SSL
|
52object using SSL_use_certificate() and SSL_use_private_key() functions.
53Thus it will permanently override the certificate and key previously
54installed and will not be reset by calling L<SSL_clear(3)|SSL_clear(3)>.
55If the callback returns no certificate, the OpenSSL library will send
56the certificate previously installed for the SSL_CTX object or the specific
57certificate of the SSL object, if available.
| 57object using the SSL_use_certificate() and SSL_use_private_key() functions.
58Thus it will permanently install the certificate and key for this SSL
59object. It will not be reset by calling L<SSL_clear(3)|SSL_clear(3)>.
60If the callback returns no certificate, the OpenSSL library will not send
61a certificate.
|
58
59=head1 BUGS
60
61The client_cert_cb() cannot return a complete certificate chain, it can
62only return one client certificate. If the chain only has a length of 2,
63the root CA certificate may be omitted according to the TLS standard and
64thus a standard conforming answer can be sent to the server. For a
65longer chain, the client must send the complete chain (with the option
--- 25 unchanged lines hidden --- | 62
63=head1 BUGS
64
65The client_cert_cb() cannot return a complete certificate chain, it can
66only return one client certificate. If the chain only has a length of 2,
67the root CA certificate may be omitted according to the TLS standard and
68thus a standard conforming answer can be sent to the server. For a
69longer chain, the client must send the complete chain (with the option
--- 25 unchanged lines hidden --- |