SSL_get_error(3)

NAME

       SSL_get_error - obtain result code for TLS/SSL I/O operation

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_get_error(const SSL *ssl, int ret);

DESCRIPTION

       SSL_get_error() returns a result code (suitable for the C "switch"
       statement) for a preceding call to SSL_connect(), SSL_accept(),
       SSL_do_handshake(), SSL_read(), SSL_peek(), or SSL_write() on ssl.  The
       value returned by that TLS/SSL I/O function must be passed to
       SSL_get_error() in parameter ret.

       In addition to ssl and ret, SSL_get_error() inspects the current
       thread's OpenSSL error queue.  Thus, SSL_get_error() must be used in
       the same thread that performed the TLS/SSL I/O operation, and no other
       OpenSSL function calls should appear in between.  The current thread's
       error queue must be empty before the TLS/SSL I/O operation is
       attempted, or SSL_get_error() will not work reliably.

RETURN VALUES

       The following return values can currently occur:

       SSL_ERROR_NONE
           The TLS/SSL I/O operation completed.  This result code is returned
           if and only if ret > 0.

       SSL_ERROR_ZERO_RETURN
           The TLS/SSL connection has been closed.  If the protocol version is
           SSL 3.0 or higher, this result code is returned only if a closure
           alert has occurred in the protocol, i.e. if the connection has been
           closed cleanly.  Note that in this case SSL_ERROR_ZERO_RETURN does
           not necessarily indicate that the underlying transport has been
           closed.

       SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
           The operation did not complete; the same TLS/SSL I/O function
           should be called again later.  If, by then, the underlying BIO has
           data available for reading (if the result code is
           SSL_ERROR_WANT_READ) or allows writing data (SSL_ERROR_WANT_WRITE),
           then some TLS/SSL protocol progress will take place, i.e. at least
           part of an TLS/SSL record will be read or written.  Note that the
           retry may again lead to a SSL_ERROR_WANT_READ or
           SSL_ERROR_WANT_WRITE condition.  There is no fixed upper limit for
           the number of iterations that may be necessary until progress
           becomes visible at application protocol level.

           For socket BIOs (e.g. when SSL_set_fd() was used), select() or
           poll() on the underlying socket can be used to find out when the
           TLS/SSL I/O function should be retried.

           Caveat: Any TLS/SSL I/O function can lead to either of
           SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE.  In particular,
           SSL_read() or SSL_peek() may want to write data and SSL_write() may
           want to read data.  This is mainly because TLS/SSL handshakes may
           occur at any time during the protocol (initiated by either the
           client or the server); SSL_read(), SSL_peek(), and SSL_write() will
           handle any pending handshakes.

       SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
           The operation did not complete; the same TLS/SSL I/O function
           should be called again later. The underlying BIO was not connected
           yet to the peer and the call would block in connect()/accept(). The
           SSL function should be called again when the connection is estab-
           lished. These messages can only appear with a BIO_s_connect() or
           BIO_s_accept() BIO, respectively.  In order to find out, when the
           connection has been successfully established, on many platforms
           select() or poll() for writing on the socket file descriptor can be
           used.

       SSL_ERROR_WANT_X509_LOOKUP
           The operation did not complete because an application callback set
           by SSL_CTX_set_client_cert_cb() has asked to be called again.  The
           TLS/SSL I/O function should be called again later.  Details depend
           on the application.

       SSL_ERROR_SYSCALL
           Some non-recoverable, fatal I/O error occurred. The OpenSSL error
           queue may contain more information on the error. For socket I/O on
           Unix systems, consult errno for details. If this error occurs then
           no further I/O operations should be performed on the connection and
           SSL_shutdown() must not be called.

       SSL_ERROR_SSL
           A non-recoverable, fatal error in the SSL library occurred, usually
           a protocol error.  The OpenSSL error queue contains more informa-
           tion on the error. If this error occurs then no further I/O opera-
           tions should be performed on the connection and SSL_shutdown() must
           not be called.

SEE ALSO

       ssl(3), err(3)

HISTORY

       SSL_get_error() was added in SSLeay 0.8.

1.0.2t                            2019-09-10                  SSL_get_error(3)