mirror of
https://github.com/openssl/openssl.git
synced 2024-12-27 06:21:43 +08:00
2695f7b19b
Reviewed-by: Neil Horman <nhorman@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/23343)
209 lines
8.6 KiB
Plaintext
209 lines
8.6 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
SSL_write_ex2, SSL_write_ex, SSL_write, SSL_sendfile, SSL_WRITE_FLAG_CONCLUDE -
|
|
write bytes to a TLS/SSL connection
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/ssl.h>
|
|
|
|
#define SSL_WRITE_FLAG_CONCLUDE
|
|
|
|
ossl_ssize_t SSL_sendfile(SSL *s, int fd, off_t offset, size_t size, int flags);
|
|
int SSL_write_ex2(SSL *s, const void *buf, size_t num,
|
|
uint64_t flags,
|
|
size_t *written);
|
|
int SSL_write_ex(SSL *s, const void *buf, size_t num, size_t *written);
|
|
int SSL_write(SSL *ssl, const void *buf, int num);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
SSL_write_ex() and SSL_write() write B<num> bytes from the buffer B<buf> into
|
|
the specified B<ssl> connection. On success SSL_write_ex() will store the number
|
|
of bytes written in B<*written>.
|
|
|
|
SSL_write_ex2() functions similarly to SSL_write_ex() but can also accept
|
|
optional flags which modify its behaviour. Calling SSL_write_ex2() with a
|
|
I<flags> argument of 0 is exactly equivalent to calling SSL_write_ex().
|
|
|
|
SSL_sendfile() writes B<size> bytes from offset B<offset> in the file
|
|
descriptor B<fd> to the specified SSL connection B<s>. This function provides
|
|
efficient zero-copy semantics. SSL_sendfile() is available only when
|
|
Kernel TLS is enabled, which can be checked by calling BIO_get_ktls_send().
|
|
It is provided here to allow users to maintain the same interface.
|
|
The meaning of B<flags> is platform dependent.
|
|
Currently, under Linux it is ignored.
|
|
|
|
The I<flags> argument to SSL_write_ex2() can accept zero or more of the
|
|
following flags. Note that which flags are supported will depend on the kind of
|
|
SSL object and underlying protocol being used:
|
|
|
|
=over 4
|
|
|
|
=item B<SSL_WRITE_FLAG_CONCLUDE>
|
|
|
|
This flag is only supported on QUIC stream SSL objects (or QUIC connection SSL
|
|
objects with a default stream attached).
|
|
|
|
If this flag is set, and the call to SSL_write_ex2() succeeds, and all of the
|
|
data passed to the call is written (meaning that C<*written == num>), the
|
|
relevant QUIC stream's send part is concluded automatically as though
|
|
L<SSL_stream_conclude(3)> was called (causing transmission of a FIN for the
|
|
stream).
|
|
|
|
While using this flag is semantically equivalent to calling
|
|
L<SSL_stream_conclude(3)> after a successful call to this function, using this
|
|
flag enables greater efficiency than making these two API calls separately, as
|
|
it enables the written stream data and the FIN flag indicating the end of the
|
|
stream to be scheduled as part of the same QUIC STREAM frame and QUIC packet.
|
|
|
|
Setting this flag does not cause a stream's send part to be concluded if not all
|
|
of the data passed to the call was consumed.
|
|
|
|
=back
|
|
|
|
A call to SSL_write_ex2() fails if a flag is passed which is not supported or
|
|
understood by the given SSL object. An application should determine if a flag is
|
|
supported (for example, for B<SSL_WRITE_FLAG_CONCLUDE>, that a QUIC stream SSL
|
|
object is being used) before attempting to use it.
|
|
|
|
=head1 NOTES
|
|
|
|
In the paragraphs below a "write function" is defined as one of either
|
|
SSL_write_ex(), or SSL_write().
|
|
|
|
If necessary, a write function will negotiate a TLS/SSL session, if not already
|
|
explicitly performed by L<SSL_connect(3)> or L<SSL_accept(3)>. If the peer
|
|
requests a re-negotiation, it will be performed transparently during
|
|
the write function operation. The behaviour of the write functions depends on the
|
|
underlying BIO.
|
|
|
|
For the transparent negotiation to succeed, the B<ssl> must have been
|
|
initialized to client or server mode. This is being done by calling
|
|
L<SSL_set_connect_state(3)> or SSL_set_accept_state()
|
|
before the first call to a write function.
|
|
|
|
If the underlying BIO is B<blocking>, the write functions will only return, once
|
|
the write operation has been finished or an error occurred.
|
|
|
|
If the underlying BIO is B<nonblocking> the write functions will also return
|
|
when the underlying BIO could not satisfy the needs of the function to continue
|
|
the operation. In this case a call to L<SSL_get_error(3)> with the
|
|
return value of the write function will yield B<SSL_ERROR_WANT_READ>
|
|
or B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
|
|
call to a write function can also cause read operations! The calling process
|
|
then must repeat the call after taking appropriate action to satisfy the needs
|
|
of the write function. The action depends on the underlying BIO. When using a
|
|
nonblocking socket, nothing is to be done, but select() can be used to check
|
|
for the required condition. When using a buffering BIO, like a BIO pair, data
|
|
must be written into or retrieved out of the BIO before being able to continue.
|
|
|
|
The write functions will only return with success when the complete contents of
|
|
B<buf> of length B<num> has been written. This default behaviour can be changed
|
|
with the SSL_MODE_ENABLE_PARTIAL_WRITE option of L<SSL_CTX_set_mode(3)>. When
|
|
this flag is set the write functions will also return with success when a
|
|
partial write has been successfully completed. In this case the write function
|
|
operation is considered completed. The bytes are sent and a new write call with
|
|
a new buffer (with the already sent bytes removed) must be started. A partial
|
|
write is performed with the size of a message block, which is 16kB.
|
|
|
|
When used with a QUIC SSL object, calling an I/O function such as SSL_write()
|
|
allows internal network event processing to be performed. It is important that
|
|
this processing is performed regularly. If an application is not using thread
|
|
assisted mode, an application should ensure that an I/O function such as
|
|
SSL_write() is called regularly, or alternatively ensure that SSL_handle_events()
|
|
is called regularly. See L<openssl-quic(7)> and L<SSL_handle_events(3)> for more
|
|
information.
|
|
|
|
=head1 WARNINGS
|
|
|
|
When a write function call has to be repeated because L<SSL_get_error(3)>
|
|
returned B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
|
|
with the same arguments.
|
|
The data that was passed might have been partially processed.
|
|
When B<SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER> was set using L<SSL_CTX_set_mode(3)>
|
|
the pointer can be different, but the data and length should still be the same.
|
|
|
|
You should not call SSL_write() with num=0, it will return an error.
|
|
SSL_write_ex() can be called with num=0, but will not send application data to
|
|
the peer.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
SSL_write_ex() and SSL_write_ex2() return 1 for success or 0 for failure.
|
|
Success means that all requested application data bytes have been written to the
|
|
SSL connection or, if SSL_MODE_ENABLE_PARTIAL_WRITE is in use, at least 1
|
|
application data byte has been written to the SSL connection. Failure means that
|
|
not all the requested bytes have been written yet (if
|
|
SSL_MODE_ENABLE_PARTIAL_WRITE is not in use) or no bytes could be written to the
|
|
SSL connection (if SSL_MODE_ENABLE_PARTIAL_WRITE is in use). Failures can be
|
|
retryable (e.g. the network write buffer has temporarily filled up) or
|
|
non-retryable (e.g. a fatal network error). In the event of a failure call
|
|
L<SSL_get_error(3)> to find out the reason which indicates whether the call is
|
|
retryable or not.
|
|
|
|
For SSL_write() the following return values can occur:
|
|
|
|
=over 4
|
|
|
|
=item E<gt> 0
|
|
|
|
The write operation was successful, the return value is the number of
|
|
bytes actually written to the TLS/SSL connection.
|
|
|
|
=item Z<><= 0
|
|
|
|
The write operation was not successful, because either the connection was
|
|
closed, an error occurred or action must be taken by the calling process.
|
|
Call SSL_get_error() with the return value B<ret> to find out the reason.
|
|
|
|
Old documentation indicated a difference between 0 and -1, and that -1 was
|
|
retryable.
|
|
You should instead call SSL_get_error() to find out if it's retryable.
|
|
|
|
=back
|
|
|
|
For SSL_sendfile(), the following return values can occur:
|
|
|
|
=over 4
|
|
|
|
=item Z<>>= 0
|
|
|
|
The write operation was successful, the return value is the number
|
|
of bytes of the file written to the TLS/SSL connection. The return
|
|
value can be less than B<size> for a partial write.
|
|
|
|
=item E<lt> 0
|
|
|
|
The write operation was not successful, because either the connection was
|
|
closed, an error occurred or action must be taken by the calling process.
|
|
Call SSL_get_error() with the return value to find out the reason.
|
|
|
|
=back
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<SSL_get_error(3)>, L<SSL_read_ex(3)>, L<SSL_read(3)>
|
|
L<SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)>,
|
|
L<SSL_connect(3)>, L<SSL_accept(3)>
|
|
L<SSL_set_connect_state(3)>, L<BIO_ctrl(3)>,
|
|
L<ssl(7)>, L<bio(7)>
|
|
|
|
=head1 HISTORY
|
|
|
|
The SSL_write_ex() function was added in OpenSSL 1.1.1.
|
|
The SSL_sendfile() function was added in OpenSSL 3.0.
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
|
|
|
|
Licensed under the Apache License 2.0 (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
|