SSL_do_handshake(3)SSL_do_handshake(3)NAMESSL_do_handshake - Perform a TLS/SSL handshake
SYNOPSIS
#include <openssl/ssl.h>
int SSL_do_handshake(
SSL *ssl );
DESCRIPTION
The SSL_do_handshake() function will wait for an SSL/TLS handshake to
take place. If the connection is in client mode, the handshake will
start. The handshake routines may have to be explicitly set in advance
using either the SSL_set_connect_state() or SSL_set_accept_state()
functions.
NOTES
The behavior 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, except for SGC
(Server Gated Cryptography). For SGC, SSL_do_handshake() may return a
-1, but SSL_get_error() will yield SSL_ERROR_WANT_READ/WRITE and
SSL_do_handshake() should be called again. If the underlying BIO is
non-blocking, 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_hand‐
shake(). The action depends on the underlying BIO. When using a non-
blocking socket, nothing is done, but select() can be used to check for
the required condition. When using a buffering BIO, such as a BIO pair,
data must be written into or retrieved out of the BIO before continu‐
ing.
RETURN VALUES
The TLS/SSL handshake was successfully completed, and a TLS/SSL connec‐
tion has been established. 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 learn the
reason. 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 non-blocking BIOs. Call SSL_get_error() with
the return value ret to learn the reason.
SEE ALSOSSL_get_error(3), SSL_connect(3), SSL_accept(3), ssl(3), SSL_set_con‐
nect_state(3), bio(3)SSL_do_handshake(3)
