NAME
SSL_do_handshake —
perform a TLS/SSL handshake
SYNOPSIS
#include
<openssl/ssl.h>
int
SSL_do_handshake(SSL
*ssl);
DESCRIPTION
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
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 controlled and by the specifications of the TLS/SSL protocol. Call SSL_get_error(3) with the return value ret to find out the reason.
- 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 ALSO
BIO_new(3), ssl(3), SSL_accept(3), SSL_connect(3), SSL_get_error(3), SSL_set_connect_state(3)
HISTORY
SSL_do_handshake() first appeared in
SSLeay 0.8.0 and has been available since OpenBSD
2.4.