SSL_do_handshake(3) OpenSSL 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, except for SGC (Server Gated
Cryptography). For SGC, SSL_do_handshake() may return with
-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_handshake(). The action depends on
the underlying BIO. When using a non-blocking 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.
RETURN VALUES
The following return values can occur:
1 The TLS/SSL handshake was successfully completed, a
TLS/SSL connection has been established.
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.
<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 of action is need to continue
the operation for non-blocking BIOs. Call
SSL_get_error() with the return value ret to find out
the reason.
SEE ALSOSSL_get_error(3), SSL_connect(3), SSL_accept(3), ssl(3),
bio(3), SSL_set_connect_state(3)19/Jul/2002 0.9.6j SSL_do_handshake(3)
