198 lines
8.2 KiB
Plaintext
198 lines
8.2 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
SSL_CTX_set_alpn_protos, SSL_set_alpn_protos, SSL_CTX_set_alpn_select_cb,
|
|
SSL_CTX_set_next_proto_select_cb, SSL_CTX_set_next_protos_advertised_cb,
|
|
SSL_select_next_proto, SSL_get0_alpn_selected, SSL_get0_next_proto_negotiated
|
|
- handle application layer protocol negotiation (ALPN)
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/ssl.h>
|
|
|
|
int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const unsigned char *protos,
|
|
unsigned int protos_len);
|
|
int SSL_set_alpn_protos(SSL *ssl, const unsigned char *protos,
|
|
unsigned int protos_len);
|
|
void SSL_CTX_set_alpn_select_cb(SSL_CTX *ctx,
|
|
int (*cb) (SSL *ssl,
|
|
const unsigned char **out,
|
|
unsigned char *outlen,
|
|
const unsigned char *in,
|
|
unsigned int inlen,
|
|
void *arg), void *arg);
|
|
void SSL_get0_alpn_selected(const SSL *ssl, const unsigned char **data,
|
|
unsigned int *len);
|
|
|
|
void SSL_CTX_set_next_protos_advertised_cb(SSL_CTX *ctx,
|
|
int (*cb)(SSL *ssl,
|
|
const unsigned char **out,
|
|
unsigned int *outlen,
|
|
void *arg),
|
|
void *arg);
|
|
void SSL_CTX_set_next_proto_select_cb(SSL_CTX *ctx,
|
|
int (*cb)(SSL *s,
|
|
unsigned char **out,
|
|
unsigned char *outlen,
|
|
const unsigned char *in,
|
|
unsigned int inlen,
|
|
void *arg),
|
|
void *arg);
|
|
int SSL_select_next_proto(unsigned char **out, unsigned char *outlen,
|
|
const unsigned char *server,
|
|
unsigned int server_len,
|
|
const unsigned char *client,
|
|
unsigned int client_len)
|
|
void SSL_get0_next_proto_negotiated(const SSL *s, const unsigned char **data,
|
|
unsigned *len);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
SSL_CTX_set_alpn_protos() and SSL_set_alpn_protos() are used by the client to
|
|
set the list of protocols available to be negotiated. The B<protos> must be in
|
|
protocol-list format, described below. The length of B<protos> is specified in
|
|
B<protos_len>.
|
|
|
|
SSL_CTX_set_alpn_select_cb() sets the application callback B<cb> used by a
|
|
server to select which protocol to use for the incoming connection. When B<cb>
|
|
is NULL, ALPN is not used. The B<arg> value is a pointer which is passed to
|
|
the application callback.
|
|
|
|
B<cb> is the application defined callback. The B<in>, B<inlen> parameters are a
|
|
vector in protocol-list format. The value of the B<out>, B<outlen> vector
|
|
should be set to the value of a single protocol selected from the B<in>,
|
|
B<inlen> vector. The B<out> buffer may point directly into B<in>, or to a
|
|
buffer that outlives the handshake. The B<arg> parameter is the pointer set via
|
|
SSL_CTX_set_alpn_select_cb().
|
|
|
|
SSL_select_next_proto() is a helper function used to select protocols. It
|
|
implements the standard protocol selection. It is expected that this function
|
|
is called from the application callback B<cb>. The protocol data in B<server>,
|
|
B<server_len> and B<client>, B<client_len> must be in the protocol-list format
|
|
described below. The first item in the B<server>, B<server_len> list that
|
|
matches an item in the B<client>, B<client_len> list is selected, and returned
|
|
in B<out>, B<outlen>. The B<out> value will point into either B<server> or
|
|
B<client>, so it should be copied immediately. If no match is found, the first
|
|
item in B<client>, B<client_len> is returned in B<out>, B<outlen>. This
|
|
function can also be used in the NPN callback.
|
|
|
|
SSL_CTX_set_next_proto_select_cb() sets a callback B<cb> that is called when a
|
|
client needs to select a protocol from the server's provided list, and a
|
|
user-defined pointer argument B<arg> which will be passed to this callback.
|
|
For the callback itself, B<out>
|
|
must be set to point to the selected protocol (which may be within B<in>).
|
|
The length of the protocol name must be written into B<outlen>. The
|
|
server's advertised protocols are provided in B<in> and B<inlen>. The
|
|
callback can assume that B<in> is syntactically valid. The client must
|
|
select a protocol. It is fatal to the connection if this callback returns
|
|
a value other than B<SSL_TLSEXT_ERR_OK>. The B<arg> parameter is the pointer
|
|
set via SSL_CTX_set_next_proto_select_cb().
|
|
|
|
SSL_CTX_set_next_protos_advertised_cb() sets a callback B<cb> that is called
|
|
when a TLS server needs a list of supported protocols for Next Protocol
|
|
Negotiation. The returned list must be in protocol-list format, described
|
|
below. The list is
|
|
returned by setting B<out> to point to it and B<outlen> to its length. This
|
|
memory will not be modified, but the B<SSL> does keep a
|
|
reference to it. The callback should return B<SSL_TLSEXT_ERR_OK> if it
|
|
wishes to advertise. Otherwise, no such extension will be included in the
|
|
ServerHello.
|
|
|
|
SSL_get0_alpn_selected() returns a pointer to the selected protocol in B<data>
|
|
with length B<len>. It is not NUL-terminated. B<data> is set to NULL and B<len>
|
|
is set to 0 if no protocol has been selected. B<data> must not be freed.
|
|
|
|
SSL_get0_next_proto_negotiated() sets B<data> and B<len> to point to the
|
|
client's requested protocol for this connection. If the client did not
|
|
request any protocol or NPN is not enabled, then B<data> is set to NULL and
|
|
B<len> to 0. Note that
|
|
the client can request any protocol it chooses. The value returned from
|
|
this function need not be a member of the list of supported protocols
|
|
provided by the callback.
|
|
|
|
=head1 NOTES
|
|
|
|
The protocol-lists must be in wire-format, which is defined as a vector of
|
|
nonempty, 8-bit length-prefixed, byte strings. The length-prefix byte is not
|
|
included in the length. Each string is limited to 255 bytes. A byte-string
|
|
length of 0 is invalid. A truncated byte-string is invalid. The length of the
|
|
vector is not in the vector itself, but in a separate variable.
|
|
|
|
Example:
|
|
|
|
unsigned char vector[] = {
|
|
6, 's', 'p', 'd', 'y', '/', '1',
|
|
8, 'h', 't', 't', 'p', '/', '1', '.', '1'
|
|
};
|
|
unsigned int length = sizeof(vector);
|
|
|
|
The ALPN callback is executed after the servername callback; as that servername
|
|
callback may update the SSL_CTX, and subsequently, the ALPN callback.
|
|
|
|
If there is no ALPN proposed in the ClientHello, the ALPN callback is not
|
|
invoked.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
SSL_CTX_set_alpn_protos() and SSL_set_alpn_protos() return 0 on success, and
|
|
non-0 on failure. WARNING: these functions reverse the return value convention.
|
|
|
|
SSL_select_next_proto() returns one of the following:
|
|
|
|
=over 4
|
|
|
|
=item OPENSSL_NPN_NEGOTIATED
|
|
|
|
A match was found and is returned in B<out>, B<outlen>.
|
|
|
|
=item OPENSSL_NPN_NO_OVERLAP
|
|
|
|
No match was found. The first item in B<client>, B<client_len> is returned in
|
|
B<out>, B<outlen>.
|
|
|
|
=back
|
|
|
|
The ALPN select callback B<cb>, must return one of the following:
|
|
|
|
=over 4
|
|
|
|
=item SSL_TLSEXT_ERR_OK
|
|
|
|
ALPN protocol selected.
|
|
|
|
=item SSL_TLSEXT_ERR_ALERT_FATAL
|
|
|
|
There was no overlap between the client's supplied list and the server
|
|
configuration.
|
|
|
|
=item SSL_TLSEXT_ERR_NOACK
|
|
|
|
ALPN protocol not selected, e.g., because no ALPN protocols are configured for
|
|
this connection.
|
|
|
|
=back
|
|
|
|
The callback set using SSL_CTX_set_next_proto_select_cb() should return
|
|
B<SSL_TLSEXT_ERR_OK> if successful. Any other value is fatal to the connection.
|
|
|
|
The callback set using SSL_CTX_set_next_protos_advertised_cb() should return
|
|
B<SSL_TLSEXT_ERR_OK> if it wishes to advertise. Otherwise, no such extension
|
|
will be included in the ServerHello.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<ssl(7)>, L<SSL_CTX_set_tlsext_servername_callback(3)>,
|
|
L<SSL_CTX_set_tlsext_servername_arg(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2016-2020 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
|
|
L<https://www.openssl.org/source/license.html>.
|
|
|
|
=cut
|