NAME
SSL_connect —
initiate the TLS/SSL handshake with a
TLS/SSL server
SYNOPSIS
#include
<openssl/ssl.h>
int
SSL_connect(SSL
*ssl);
DESCRIPTION
SSL_connect()
initiates the TLS/SSL handshake with a server. The communication channel
must already have been set and assigned to the ssl by
setting an underlying BIO.
The behaviour of
SSL_connect()
depends on the underlying BIO.
If the underlying BIO is
blocking,
SSL_connect()
will only return once the handshake has been finished or an error
occurred.
If the underlying BIO is
non-blocking,
SSL_connect()
will also return when the underlying BIO could not
satisfy the needs of SSL_connect() to continue the
handshake, indicating the problem with the return value −1. In this
case a call to
SSL_get_error(3) with the return value of
SSL_connect() 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_connect(). 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_CTX_new(3), SSL_do_handshake(3), SSL_get_error(3), SSL_set_connect_state(3), SSL_shutdown(3)
HISTORY
SSL_connect() appeared in SSLeay 0.4 or
earlier and has been available since OpenBSD
2.4.