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 (SSL_R_UNEXPECTED_EOF_WHILE_READING). This error reason code may be used for
       control flow decisions (see the man page for ERR_GET_REASON(3) for further details on this).

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 2000-2024 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>.

3.0.13                                             2025-02-05                                SSL_GET_ERROR(3SSL)