Rename SSL_CTX_set_early_cb to SSL_CTX_set_client_hello_cb.

SSL_CIPHER_find() returns a B<SSL_CIPHER> structure which has the cipher ID stored

in B<ptr>. The B<ptr> parameter is a two element array of B<char>, which stores the

two-byte TLS cipher ID (as allocated by IANA) in network byte order. This parameter

is usually retrieved from a TLS packet by using functions like L<SSL_early_get0_ciphers(3)>.

SSL_CIPHER_find() returns NULL if an error occurs or the indicated cipher is not found.

is usually retrieved from a TLS packet by using functions like

L<SSL_client_hello_get0_ciphers(3)>.  SSL_CIPHER_find() returns NULL if an

error occurs or the indicated cipher is not found.

SSL_CIPHER_get_id() returns the OpenSSL-specific ID of the given cipher B<c>. That ID is

not the same as the IANA-specific ID.

=head1 NAME

SSL_CTX_set_early_cb, SSL_early_cb_fn, SSL_early_isv2, SSL_early_get0_legacy_version, SSL_early_get0_random, SSL_early_get0_session_id, SSL_early_get0_ciphers, SSL_early_get0_compression_methods, SSL_early_get1_extensions_present, SSL_early_get0_ext - callback functions for early server-side ClientHello processing

SSL_CTX_set_client_hello_cb, SSL_client_hello_cb_fn, SSL_client_hello_isv2, SSL_client_hello_get0_legacy_version, SSL_client_hello_get0_random, SSL_client_hello_get0_session_id, SSL_client_hello_get0_ciphers, SSL_client_hello_get0_compression_methods, SSL_client_hello_get1_extensions_present, SSL_client_hello_get0_ext - callback functions for early server-side ClientHello processing

=head1 SYNOPSIS

 typedef int (*SSL_early_cb_fn)(SSL *s, int *al, void *arg);

 void SSL_CTX_set_early_cb(SSL_CTX *c, SSL_early_cb_fn *f, void *arg);

 int SSL_early_isv2(SSL *s);

 unsigned int SSL_early_get0_legacy_version(SSL *s);

 size_t SSL_early_get0_random(SSL *s, const unsigned char **out);

 size_t SSL_early_get0_session_id(SSL *s, const unsigned char **out);

 size_t SSL_early_get0_ciphers(SSL *s, const unsigned char **out);

 size_t SSL_early_get0_compression_methods(SSL *s, const unsigned char **out);

 int SSL_early_get1_extensions_present(SSL *s, int **out, size_t *outlen);

 int SSL_early_get0_ext(SSL *s, int type, const unsigned char **out,

 typedef int (*SSL_client_hello_cb_fn)(SSL *s, int *al, void *arg);

 void SSL_CTX_set_client_hello_cb(SSL_CTX *c, SSL_client_hello_cb_fn *f,

                                  void *arg);

 int SSL_client_hello_isv2(SSL *s);

 unsigned int SSL_client_hello_get0_legacy_version(SSL *s);

 size_t SSL_client_hello_get0_random(SSL *s, const unsigned char **out);

 size_t SSL_client_hello_get0_session_id(SSL *s, const unsigned char **out);

 size_t SSL_client_hello_get0_ciphers(SSL *s, const unsigned char **out);

 size_t SSL_client_hello_get0_compression_methods(SSL *s,

                                                  const unsigned char **out);

 int SSL_client_hello_get1_extensions_present(SSL *s, int **out,

                                              size_t *outlen);

 int SSL_client_hello_get0_ext(SSL *s, int type, const unsigned char **out,

                               size_t *outlen);

=head1 DESCRIPTION

SSL_CTX_set_early_cb() sets the callback function, which is automatically

SSL_CTX_set_client_hello_cb() sets the callback function, which is automatically

called during the early stages of ClientHello processing on the server.

The argument supplied when setting the callback is passed back to the

callback at runtime.  A callback that returns failure (0) will cause the

what alert value is to be sent in the B<al> parameter.  A callback may

also return a negative value to suspend the handshake, and the handshake

function will return immediately.  L<SSL_get_error(3)> will return

SSL_ERROR_WANT_EARLY to indicate that the handshake was suspended.

It is the job of the early callback to store information about the state

SSL_ERROR_WANT_CLIENT_HELLO_CB to indicate that the handshake was suspended.

It is the job of the ClientHello callback to store information about the state

of the last call if needed to continue.  On the next call into the handshake

function, the early callback will be called again, and, if it returns

function, the ClientHello callback will be called again, and, if it returns

success, normal handshake processing will continue from that point.

SSL_early_isv2() indicates whether the ClientHello was carried in a

SSL_client_hello_isv2() indicates whether the ClientHello was carried in a

SSLv2 record and is in the SSLv2 format.  The SSLv2 format has substantial

differences from the normal SSLv3 format, including using three bytes per

cipher suite, and not allowing extensions.  Additionally, the SSLv2 format

'challenge' field is exposed via SSL_early_get0_random(), padded to

'challenge' field is exposed via SSL_client_hello_get0_random(), padded to

SSL3_RANDOM_SIZE bytes with zeros if needed.  For SSLv2 format ClientHellos,

SSL_early_get0_compression_methods() returns a dummy list that only includes

SSL_client_hello_get0_compression_methods() returns a dummy list that only includes

the null compression method, since the SSLv2 format does not include a

mechanism by which to negotiate compression.

SSL_early_get0_random(), SSL_early_get0_session_id(), SSL_early_get0_ciphers(),

and SSL_early_get0_compression_methods() provide access to the corresponding

ClientHello fields, returning the field length and optionally setting an

out pointer to the octets of that field.

SSL_client_hello_get0_random(), SSL_client_hello_get0_session_id(),

SSL_client_hello_get0_ciphers(), and

SSL_client_hello_get0_compression_methods() provide access to the corresponding

ClientHello fields, returning the field length and optionally setting an out

pointer to the octets of that field.

Similarly, SSL_early_get0_ext() provides access to individual extensions

Similarly, SSL_client_hello_get0_ext() provides access to individual extensions

from the ClientHello on a per-extension basis.  For the provided wire

protocol extension type value, the extension value and length are returned

in the output parameters (if present).

SSL_early_get1_extensions_present() can be used prior to SSL_early_get0_ext(),

to determine which extensions are present in the ClientHello before querying

for them.  The B<out> and B<outlen> parameters are both required, and on

success the caller must release the storage allocated for B<*out> using

OPENSSL_free().  The contents of B<*out> is an array of integers holding the

numerical value of the TLS extension types in the order they appear in the

ClientHello.  B<*outlen> contains the number of elements in the array.

SSL_client_hello_get1_extensions_present() can be used prior to

SSL_client_hello_get0_ext(), to determine which extensions are present in the

ClientHello before querying for them.  The B<out> and B<outlen> parameters are

both required, and on success the caller must release the storage allocated for

B<*out> using OPENSSL_free().  The contents of B<*out> is an array of integers

holding the numerical value of the TLS extension types in the order they appear

in the ClientHello.  B<*outlen> contains the number of elements in the array.

=head1 NOTES

The early callback provides a vast window of possibilities for application

The ClientHello callback provides a vast window of possibilities for application

code to affect the TLS handshake.  A primary use of the callback is to

allow the server to examine the server name indication extension provided

by the client in order to select an appropriate certificate to present,

versions, changing the server's cipher list in response to the client's

cipher list, etc.

It is also recommended that applications utilize an early callback and

It is also recommended that applications utilize a ClientHello callback and

not use a servername callback, in order to avoid unexpected behavior that

occurs due to the relative order of processing between things like session

resumption and the historical servername callback.

The SSL_early_* family of functions may only be called from code executing

within an early callback.

The SSL_client_hello_* family of functions may only be called from code executing

within a ClientHello callback.

=head1 RETURN VALUES

The application's supplied early callback returns 1 on success, 0 on failure,

The application's supplied ClientHello callback returns 1 on success, 0 on failure,

and a negative value to suspend processing.

SSL_early_isv2() returns 1 for SSLv2-format ClientHellos and 0 otherwise.

SSL_client_hello_isv2() returns 1 for SSLv2-format ClientHellos and 0 otherwise.

SSL_early_get0_random(), SSL_early_get0_session_id(), SSL_early_get0_ciphers(),

and SSL_early_get0_compression_methods() return the length of the corresponding

ClientHello fields.  If zero is returned, the output pointer should not be

assumed to be valid.

SSL_client_hello_get0_random(), SSL_client_hello_get0_session_id(),

SSL_client_hello_get0_ciphers(), and

SSL_client_hello_get0_compression_methods() return the length of the

corresponding ClientHello fields.  If zero is returned, the output pointer

should not be assumed to be valid.

SSL_early_get0_ext() returns 1 if the extension of type 'type' is present, and

SSL_client_hello_get0_ext() returns 1 if the extension of type 'type' is present, and

0 otherwise.

SSL_early_get1_extensions_present() returns 1 on success and 0 on failure.

SSL_client_hello_get1_extensions_present() returns 1 on success and 0 on failure.

=head1 SEE ALSO

=head1 HISTORY

The SSL early callback, SSL_early_isv2(), SSL_early_get0_random(),

SSL_early_get0_session_id(), SSL_early_get0_ciphers(),

SSL_early_get0_compression_methods(), SSL_early_get0_ext(), and

SSL_early_get1_extensions_present() were added in OpenSSL 1.1.1.

The SSL ClientHello callback, SSL_client_hello_isv2(),

SSL_client_hello_get0_random(), SSL_client_hello_get0_session_id(),

SSL_client_hello_get0_ciphers(), SSL_client_hello_get0_compression_methods(),

SSL_client_hello_get0_ext(), and SSL_client_hello_get1_extensions_present()

were added in OpenSSL 1.1.1.

=head1 COPYRIGHT

=head1 DESCRIPTION

The functionality provided by the servername callback is superseded by

the early callback, which can be set using SSL_CTX_set_early_cb().

The functionality provided by the servername callback is superseded by the

ClientHello callback, which can be set using SSL_CTX_set_client_hello_cb().

The servername callback is retained for historical compatibility.

SSL_CTX_set_tlsext_servername_callback() sets the application callback B<cb>

=head1 NOTES

Several callbacks are executed during ClientHello processing, including

the early, ALPN, and servername callbacks.  The early callback is executed

first, then the servername callback, followed by the ALPN callback.

the ClientHello, ALPN, and servername callbacks.  The ClientHello callback is

executed first, then the servername callback, followed by the ALPN callback.

The SSL_set_tlsext_host_name() function should only be called on SSL objects

that will act as clients; otherwise the configured B<name> will be ignored.

=head1 SEE ALSO

L<ssl(7)>, L<SSL_CTX_set_alpn_select_cb(3)>,

L<SSL_get0_alpn_selected(3)>, L<SSL_CTX_set_early_cb(3)>

L<SSL_get0_alpn_selected(3)>, L<SSL_CTX_set_client_hello_cb(3)>

=head1 COPYRIGHT

operation after a currently executing asynchronous operation for the current

thread has completed.

=item SSL_ERROR_WANT_EARLY

=item SSL_ERROR_WANT_CLIENT_HELLO_CB

The operation did not complete because an application callback set by

SSL_CTX_set_early_cb() has asked to be called again.

SSL_CTX_set_client_hello_cb() has asked to be called again.

The TLS/SSL I/O function should be called again later.

Details depend on the application.

=head1 HISTORY

SSL_ERROR_WANT_ASYNC was added in OpenSSL 1.1.0.

SSL_ERROR_WANT_EARLY was added in OpenSSL 1.1.1.

SSL_ERROR_WANT_CLIENT_HELLO_CB was added in OpenSSL 1.1.1.

=head1 COPYRIGHT

=head1 NAME

SSL_want, SSL_want_nothing, SSL_want_read, SSL_want_write, SSL_want_x509_lookup,

SSL_want_async, SSL_want_async_job, SSL_want_early - obtain state information

TLS/SSL I/O operation

SSL_want_async, SSL_want_async_job, SSL_want_client_hello_cb - obtain state

information TLS/SSL I/O operation

=head1 SYNOPSIS

 int SSL_want_x509_lookup(const SSL *ssl);

 int SSL_want_async(const SSL *ssl);

 int SSL_want_async_job(const SSL *ssl);

 int SSL_want_early(const SSL *ssl);

 int SSL_want_client_hello_cb(const SSL *ssl);

=head1 DESCRIPTION

available in the pool (see ASYNC_init_thread(3)). A call to L<SSL_get_error(3)>

should return SSL_ERROR_WANT_ASYNC_JOB.

=item SSL_EARLY_WORK

=item SSL_CLIENT_HELLO_CB

The operation did not complete because an application callback set by

SSL_CTX_set_early_cb() has asked to be called again.

SSL_CTX_set_client_hello_cb() has asked to be called again.

A call to L<SSL_get_error(3)> should return

SSL_ERROR_WANT_EARLY.

SSL_ERROR_WANT_CLIENT_HELLO_CB.

=back

SSL_want_nothing(), SSL_want_read(), SSL_want_write(), SSL_want_x509_lookup(),

SSL_want_async(), SSL_want_async_job(), and SSL_want_early() return 1, when

the corresponding condition is true or 0 otherwise.

SSL_want_async(), SSL_want_async_job(), and SSL_want_client_hello_cb() return

1, when the corresponding condition is true or 0 otherwise.

=head1 SEE ALSO

=head1 HISTORY

SSL_want_early() and SSL_EARLY_WORK were added in OpenSSL 1.1.1.

SSL_want_client_hello_cb() and SSL_CLIENT_HELLO_CB were added in OpenSSL 1.1.1.

=head1 COPYRIGHT