SSL_DO_HANDSHAKE(3) BSD Library Functions Manual SSL_DO_HANDSHAKE(3)NAMESSL_do_handshake — perform a TLS/SSL handshake
SYNOPSIS
#include <openssl/ssl.h>
int
SSL_do_handshake(SSL *ssl);
DESCRIPTIONSSL_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).
NOTES
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 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(3) 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 non-blocking socket, nothing is to be done, but select(2) 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.
RETURN VALUES
The following return values can occur:
0 The TLS/SSL handshake was not successful but was shut down con‐
trolled and by the specifications of the TLS/SSL protocol. Call
SSL_get_error(3) with the return value ret to find out the rea‐
son.
1 The TLS/SSL handshake was successfully completed, and a TLS/SSL
connection has been established.
<0 The TLS/SSL handshake was not successful because either a fatal
error occurred 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(3) with the return value ret to find out the
reason.
SEE ALSObio(3), ssl(3), SSL_accept(3), SSL_connect(3), SSL_get_error(3),
SSL_set_connect_state(3)BSD April 26, 2024 BSD
