109 lines
4.1 KiB
Text
109 lines
4.1 KiB
Text
=pod
|
|
|
|
=head1 NAME
|
|
|
|
SSL_write - write bytes to a TLS/SSL connection.
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/ssl.h>
|
|
|
|
int SSL_write(SSL *ssl, const void *buf, int num);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
SSL_write() writes B<num> bytes from the buffer B<buf> into the specified
|
|
B<ssl> connection.
|
|
|
|
=head1 NOTES
|
|
|
|
If necessary, SSL_write() will negotiate a TLS/SSL session, if
|
|
not already explicitly performed by L<SSL_connect(3)|SSL_connect(3)> or
|
|
L<SSL_accept(3)|SSL_accept(3)>. If the
|
|
peer requests a re-negotiation, it will be performed transparently during
|
|
the SSL_write() operation. The behaviour of SSL_write() 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)|SSL_set_connect_state(3)> or SSL_set_accept_state()
|
|
before the first call to an L<SSL_read(3)|SSL_read(3)> or SSL_write() function.
|
|
|
|
If the underlying BIO is B<blocking>, SSL_write() will only return, once the
|
|
write operation has been finished or an error occurred, except when a
|
|
renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
|
|
This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
|
|
L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
|
|
|
|
If the underlying BIO is B<non-blocking>, SSL_write() will also return,
|
|
when the underlying BIO could not satisfy the needs of SSL_write()
|
|
to continue the operation. In this case a call to
|
|
L<SSL_get_error(3)|SSL_get_error(3)> with the
|
|
return value of SSL_write() 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 SSL_write() can also cause read operations! The calling process
|
|
then must repeat the call after taking appropriate action to satisfy the
|
|
needs of SSL_write(). The action depends on the underlying BIO. When using a
|
|
non-blocking 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.
|
|
|
|
SSL_write() 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)|SSL_CTX_set_mode(3)>. When this flag is set,
|
|
SSL_write() will also return with success, when a partial write has been
|
|
successfully completed. In this case the SSL_write() operation is considered
|
|
completed. The bytes are sent and a new SSL_write() operation 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 for SSLv3/TLSv1.
|
|
|
|
=head1 WARNING
|
|
|
|
When an SSL_write() operation has to be repeated because of
|
|
B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
|
|
with the same arguments.
|
|
|
|
When calling SSL_write() with num=0 bytes to be sent the behaviour is
|
|
undefined.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
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 0
|
|
|
|
The write operation was not successful. Probably the underlying connection
|
|
was closed. Call SSL_get_error() with the return value B<ret> to find out,
|
|
whether an error occurred or the connection was shut down cleanly
|
|
(SSL_ERROR_ZERO_RETURN).
|
|
|
|
SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
|
|
only be detected, whether the underlying connection was closed. It cannot
|
|
be checked, why the closure happened.
|
|
|
|
=item E<lt>0
|
|
|
|
The write operation was not successful, because either 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.
|
|
|
|
=back
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
|
|
L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)|SSL_CTX_new(3)>,
|
|
L<SSL_connect(3)|SSL_connect(3)>, L<SSL_accept(3)|SSL_accept(3)>
|
|
L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>,
|
|
L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>
|
|
|
|
=cut
|