114 lines
4.2 KiB
Text
114 lines
4.2 KiB
Text
=pod
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=head1 NAME
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SSL_get_error - obtain result code for TLS/SSL I/O operation
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_get_error(const SSL *ssl, int ret);
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=head1 DESCRIPTION
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SSL_get_error() returns a result code (suitable for the C "switch"
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statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
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SSL_read(), SSL_peek(), or SSL_write() on B<ssl>. The value returned by
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that TLS/SSL I/O function must be passed to SSL_get_error() in parameter
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B<ret>.
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In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
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current thread's OpenSSL error queue. Thus, SSL_get_error() must be
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used in the same thread that performed the TLS/SSL I/O operation, and no
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other OpenSSL function calls should appear in between. The current
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thread's error queue must be empty before the TLS/SSL I/O operation is
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attempted, or SSL_get_error() will not work reliably.
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=head1 RETURN VALUES
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The following return values can currently occur:
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=over 4
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=item SSL_ERROR_NONE
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The TLS/SSL I/O operation completed. This result code is returned
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if and only if B<ret E<gt> 0>.
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=item SSL_ERROR_ZERO_RETURN
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The TLS/SSL connection has been closed. If the protocol version is SSL 3.0
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or TLS 1.0, this result code is returned only if a closure
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alert has occurred in the protocol, i.e. if the connection has been
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closed cleanly. Note that in this case B<SSL_ERROR_ZERO_RETURN>
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does not necessarily indicate that the underlying transport
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has been closed.
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=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
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The operation did not complete; the same TLS/SSL I/O function should be
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called again later. If, by then, the underlying B<BIO> has data
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available for reading (if the result code is B<SSL_ERROR_WANT_READ>)
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or allows writing data (B<SSL_ERROR_WANT_WRITE>), then some TLS/SSL
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protocol progress will take place, i.e. at least part of an TLS/SSL
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record will be read or written. Note that the retry may again lead to
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a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition.
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There is no fixed upper limit for the number of iterations that
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may be necessary until progress becomes visible at application
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protocol level.
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For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
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poll() on the underlying socket can be used to find out when the
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TLS/SSL I/O function should be retried.
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Caveat: Any TLS/SSL I/O function can lead to either of
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B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. In particular,
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SSL_read() or SSL_peek() may want to write data and SSL_write() may want
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to read data. This is mainly because TLS/SSL handshakes may occur at any
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time during the protocol (initiated by either the client or the server);
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SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes.
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=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
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The operation did not complete; the same TLS/SSL I/O function should be
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called again later. The underlying BIO was not connected yet to the peer
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and the call would block in connect()/accept(). The SSL function should be
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called again when the connection is established. These messages can only
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appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
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In order to find out, when the connection has been successfully established,
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on many platforms select() or poll() for writing on the socket file descriptor
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can be used.
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=item SSL_ERROR_WANT_X509_LOOKUP
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The operation did not complete because an application callback set by
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SSL_CTX_set_client_cert_cb() has asked to be called again.
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The TLS/SSL I/O function should be called again later.
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Details depend on the application.
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=item SSL_ERROR_SYSCALL
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Some I/O error occurred. The OpenSSL error queue may contain more
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information on the error. If the error queue is empty
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(i.e. ERR_get_error() returns 0), B<ret> can be used to find out more
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about the error: If B<ret == 0>, an EOF was observed that violates
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the protocol. If B<ret == -1>, the underlying B<BIO> reported an
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I/O error (for socket I/O on Unix systems, consult B<errno> for details).
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=item SSL_ERROR_SSL
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A failure in the SSL library occurred, usually a protocol error. The
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OpenSSL error queue contains more information on the error.
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=back
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=head1 SEE ALSO
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L<ssl(3)|ssl(3)>, L<err(3)|err(3)>
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=head1 HISTORY
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SSL_get_error() was added in SSLeay 0.8.
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=cut
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