Updated: 2021/Apr/14


SSL_get_error(3)                    OpenSSL                   SSL_get_error(3)



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

LIBRARY
       libcrypto, -lcrypto

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_ex(), SSL_read(), SSL_peek_ex(),
       SSL_peek(), SSL_shutdown(), SSL_write_ex() 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 peer has closed the connection for writing by sending
           the close_notify alert.  No more data can be read.  Note that
           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 and can be retried later.

           SSL_ERROR_WANT_READ is returned when the last operation was a read
           operation from a nonblocking BIO.  It means that not enough data
           was available at this time to complete the operation.  If at a
           later time the underlying BIO has data available for reading the
           same function can be called again.

           SSL_read() and SSL_read_ex() can also set SSL_ERROR_WANT_READ when
           there is still unprocessed data available at either the SSL or the
           BIO layer, even for a blocking BIO.  See SSL_read(3) for more
           information.

           SSL_ERROR_WANT_WRITE is returned when the last operation was a
           write to a nonblocking BIO and it was unable to sent all data to
           the BIO.  When the BIO is writable again, the same function can be
           called again.

           Note that the retry may again lead to an 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.

           It is safe to call SSL_read() or SSL_read_ex() when more data is
           available even when the call that set this error was an SSL_write()
           or SSL_write_ex().  However, if the call was an SSL_write() or
           SSL_write_ex(), it should be called again to continue sending the
           application data.

           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_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to
           write data and SSL_write() or SSL_write_ex() 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_ex(), SSL_read(), SSL_peek_ex(), SSL_peek(),
           SSL_write_ex(), 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
           established. 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_WANT_ASYNC
           The operation did not complete because an asynchronous engine is
           still processing data. This will only occur if the mode has been
           set to SSL_MODE_ASYNC using SSL_CTX_set_mode(3) or SSL_set_mode(3)
           and an asynchronous capable engine is being used. An application
           can determine whether the engine has completed its processing using
           select() or poll() on the asynchronous wait file descriptor. This
           file descriptor is available by calling SSL_get_all_async_fds(3) or
           SSL_get_changed_async_fds(3). The TLS/SSL I/O function should be
           called again later. The function must be called from the same
           thread that the original call was made from.

       SSL_ERROR_WANT_ASYNC_JOB
           The asynchronous job could not be started because there were no
           async jobs available in the pool (see ASYNC_init_thread(3)). This
           will only occur if the mode has been set to SSL_MODE_ASYNC using
           SSL_CTX_set_mode(3) or SSL_set_mode(3) and a maximum limit has been
           set on the async job pool through a call to ASYNC_init_thread(3).
           The application should retry the operation after a currently
           executing asynchronous operation for the current thread has
           completed.

       SSL_ERROR_WANT_CLIENT_HELLO_CB
           The operation did not complete because an application callback set
           by SSL_CTX_set_client_hello_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.

           This value can also be returned for other errors, check the error
           queue for details.

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

BUGS
       The SSL_ERROR_SYSCALL with errno value of 0 indicates unexpected EOF
       from the peer. This will be properly reported as SSL_ERROR_SSL with
       reason code SSL_R_UNEXPECTED_EOF_WHILE_READING in the OpenSSL 3.0
       release because it is truly a TLS protocol error to terminate the
       connection without a SSL_shutdown().

       The issue is kept unfixed in OpenSSL 1.1.1 releases because many
       applications which choose to ignore this protocol error depend on the
       existing way of reporting the error.

SEE ALSO
       ssl(7)

HISTORY
       The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0.  The
       SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1.

COPYRIGHT
       Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2020-12-10                  SSL_get_error(3)