SSL_do_handshake.pod revision 279264 
1=pod
2
3=head1 NAME
4
5SSL_do_handshake - perform a TLS/SSL handshake
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 int SSL_do_handshake(SSL *ssl);
12
13=head1 DESCRIPTION
14
15SSL_do_handshake() will wait for a SSL/TLS handshake to take place. If the
16connection is in client mode, the handshake will be started. The handshake
17routines may have to be explicitly set in advance using either
18L<SSL_set_connect_state(3)|SSL_set_connect_state(3)> or
19L<SSL_set_accept_state(3)|SSL_set_accept_state(3)>.
20
21=head1 NOTES
22
23The behaviour of SSL_do_handshake() depends on the underlying BIO.
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25If the underlying BIO is B<blocking>, SSL_do_handshake() will only return
26once the handshake has been finished or an error occurred, except for SGC
27(Server Gated Cryptography). For SGC, SSL_do_handshake() may return with -1,
28but SSL_get_error() will yield B<SSL_ERROR_WANT_READ/WRITE> and
29SSL_do_handshake() should be called again.
30
31If the underlying BIO is B<non-blocking>, SSL_do_handshake() will also return
32when the underlying BIO could not satisfy the needs of SSL_do_handshake()
33to continue the handshake. In this case a call to SSL_get_error() with the
34return value of SSL_do_handshake() will yield B<SSL_ERROR_WANT_READ> or
35B<SSL_ERROR_WANT_WRITE>. The calling process then must repeat the call after
36taking appropriate action to satisfy the needs of SSL_do_handshake().
37The action depends on the underlying BIO. When using a non-blocking socket,
38nothing is to be done, but select() can be used to check for the required
39condition. When using a buffering BIO, like a BIO pair, data must be written
40into or retrieved out of the BIO before being able to continue.
41
42=head1 RETURN VALUES
43
44The following return values can occur:
45
46=over 4
47
48=item Z<>0
49
50The TLS/SSL handshake was not successful but was shut down controlled and
51by the specifications of the TLS/SSL protocol. Call SSL_get_error() with the
52return value B<ret> to find out the reason.
53
54=item Z<>1
55
56The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been
57established.
58
59=item E<lt>0
60
61The TLS/SSL handshake was not successful because a fatal error occurred either
62at the protocol level or a connection failure occurred. The shutdown was
63not clean. It can also occur of action is need to continue the operation
64for non-blocking BIOs. Call SSL_get_error() with the return value B<ret>
65to find out the reason.
66
67=back
68
69=head1 SEE ALSO
70
71L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_connect(3)|SSL_connect(3)>,
72L<SSL_accept(3)|SSL_accept(3)>, L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>,
73L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>
74
75=cut
76