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Better description of the behaviour of SSL_shutdown() as it is now, broken

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or not.
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Lutz Jänicke 2001-08-16 14:27:55 +00:00
parent 45a2f93906
commit 9e09eebf94
1 changed files with 38 additions and 7 deletions
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45
doc/ssl/SSL_shutdown.pod
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@ -22,10 +22,38 @@ Whether the operation succeeds or not, the SSL_SENT_SHUTDOWN flag is set and
a currently open session is considered closed and good and will be kept in the
session cache for further reuse.
The behaviour of SSL_shutdown() depends on the underlying BIO.
The shutdown procedure consists of 2 steps: the sending of the "close notify"
shutdown alert and the receipt ion of the peer's "close notify" shutdown
alert:
=over 4
=item When the application is the first party to send the "close notify"
alert, SSL_shutdown() will only send the alert and the set the
SSL_SENT_SHUTDOWN flag (so that the session is considered good and will
be kept in cache). SSL_shutdown() will then return with 0. In order to
complete the shutdown handshake, SSL_shutdown() must be called again.
The second call will make SSL_shutdown() wait for the peer's "close notify"
shutdown alert. On success, the second call to SSL_shutdown() will return
with 1.
=item If the peer already sent the "close notify" alert B<and> it was
already processed implicitly inside another call of e.g.
B<SSL_read(3)|SSL_read(3)>, SSL_shutdown() will send the "close notify"
alert and will immediately return with 1.
=back
It is therefore recommended, to check the return value of SSL_shutdown()
and call SSL_shutdown() again, if the bidirectional shutdown is not yet
complete (return value of the first call is 0). As the shutdown is not
specially handled in the SSLv2 protocol, SSL_shutdown() will succeed on
the first call.
The behaviour of SSL_shutdown() additionally depends on the underlying BIO.
If the underlying BIO is B<blocking>, SSL_shutdown() will only return once the
handshake has been finished or an error occurred.
handshake step has been finished or an error occurred.
If the underlying BIO is B<non-blocking>, SSL_shutdown() will also return
when the underlying BIO could not satisfy the needs of SSL_shutdown()
@ -46,19 +74,22 @@ The following return values can occur:
=item 1
The shutdown was successfully completed.
The shutdown was successfully completed. The "close notify" alert was sent
and the peer's "close notify" alert was received.
=item 0
The shutdown was not successful. Call SSL_get_error() with the return
value B<ret> to find out the reason.
The shutdown is not yet finished. Call SSL_shutdown() for a second time.
The output of L<SSL_get_error(3)|SSL_get_error(3)> may be misleading, as an
erroneous SSL_ERROR_SYSCALL may be flagged even though no error occurred.
=item -1
The shutdown was not successful because a fatal error occurred either
at the protocol level or a connection failure occurred. It can also occur of
at the protocol level or a connection failure occurred. It can also occur if
action is need to continue the operation for non-blocking BIOs.
Call SSL_get_error() with the return value B<ret> to find out the reason.
Call L<SSL_get_error(3)|SSL_get_error(3)> with the return value B<ret>
to find out the reason.
=back