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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

  The SSL_do_handshake() function will wait for an SSL/TLS handshake to take
  place. If the connection is in client mode, the handshake will start. The
  handshake routines may have to be explicitly set in advance using either
  the SSL_set_connect_state() or SSL_set_accept_state() functions.


NOTES

  The behavior 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 a -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 done, but select() can be used to
  check for the required condition. When using a buffering BIO, such as a BIO
  pair, data must be written into or retrieved out of the  BIO before
  continuing.


RETURN VALUES

  1	  The TLS/SSL handshake was successfully completed, and 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 learn 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 if action
	  is needed to continue the operation for non-blocking BIOs. Call
	  SSL_get_error() with the return value ret to learn the reason.


SEE ALSO

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

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