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:
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 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)1.0.0k 2013-02-19 SSL_do_handshake(3)
