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_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.

NOTES

       Some TLS implementations do not send a close_notify alert on shutdown.

       On an unexpected EOF, versions before OpenSSL 3.0 returned SSL_ERROR_SYSCALL, nothing was
       added to the error stack, and errno was 0.  Since OpenSSL 3.0 the returned error is
       SSL_ERROR_SSL with a meaningful error on the error stack.

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.

           This error can also appear when the option SSL_OP_IGNORE_UNEXPECTED_EOF is set. See
           SSL_CTX_set_options(3) for more details.

       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. If you get SSL_ERROR_WANT_WRITE from SSL_write() or
           SSL_write_ex() then you should not do any other operation that could trigger IO other
           than to repeat the previous SSL_write() call.

           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.

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 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.