SSL_do_handshake(3)

SSL_do_handshake(3)          OpenSSL          SSL_do_handshake(3)

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).

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() 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

1.0.2t               Last change: 2019-09-10                    1

SSL_do_handshake(3)          OpenSSL          SSL_do_handshake(3)

         operation for non-blocking BIOs. Call SSL_get_error()
         with the return value ret to find out the reason.

SEE ALSO

     SSL_get_error(3), SSL_connect(3), SSL_accept(3), ssl(3),
     bio(3), SSL_set_connect_state(3)

1.0.2t               Last change: 2019-09-10                    2