SSL_do_handshake - perform a TLS/SSL handshake
#include <openssl/ssl.h>
int SSL_do_handshake(SSL *ssl);
SSL_do_handshake() will wait for a SSL/TLS handshake to take place. If
the connection is in client mode, the handshake will be started. The handshake
routines may have to be explicitly set in advance using either
SSL_set_connect_state(3) or
SSL_set_accept_state(3).
The behaviour of
SSL_do_handshake() depends on the underlying BIO.
If the underlying BIO is
blocking,
SSL_do_handshake() will only
return once the handshake has been finished or an error occurred.
If the underlying BIO is
nonblocking,
SSL_do_handshake() will also
return when the underlying BIO could not satisfy the needs of
SSL_do_handshake() to continue the handshake. In this case a call to
SSL_get_error() with the return value of
SSL_do_handshake() will
yield
SSL_ERROR_WANT_READ or
SSL_ERROR_WANT_WRITE. The calling
process then must repeat the call after taking appropriate action to satisfy
the needs of
SSL_do_handshake(). 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 following return values can occur:
- 0
- The TLS/SSL handshake was not successful but was shut down
controlled and by the specifications of the TLS/SSL protocol. Call
SSL_get_error() with the return value ret to find out the
reason.
- 1
- The TLS/SSL handshake was successfully completed, a TLS/SSL
connection has been established.
- <0
- The TLS/SSL handshake was not successful because a fatal
error occurred either at the protocol level or a connection failure
occurred. The shutdown was not clean. It can also occur if action is
needed to continue the operation for nonblocking BIOs. Call
SSL_get_error() with the return value ret to find out the
reason.
SSL_get_error(3),
SSL_connect(3),
SSL_accept(3),
ssl(7),
bio(7),
SSL_set_connect_state(3)
Copyright 2002-2020 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
<
https://www.openssl.org/source/license.html>.