1=pod 2 3=head1 NAME 4 5SSL_get_error - obtain result code for TLS/SSL I/O operation 6 7=head1 SYNOPSIS 8 9 #include <openssl/ssl.h> 10 11 int SSL_get_error(const SSL *ssl, int ret); 12 13=head1 DESCRIPTION 14 15SSL_get_error() returns a result code (suitable for the C "switch" 16statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(), 17SSL_read_ex(), SSL_read(), SSL_peek_ex(), SSL_peek(), SSL_shutdown(), 18SSL_write_ex() or SSL_write() on B<ssl>. The value returned by that TLS/SSL I/O 19function must be passed to SSL_get_error() in parameter B<ret>. 20 21In addition to B<ssl> and B<ret>, SSL_get_error() inspects the 22current thread's OpenSSL error queue. Thus, SSL_get_error() must be 23used in the same thread that performed the TLS/SSL I/O operation, and no 24other OpenSSL function calls should appear in between. The current 25thread's error queue must be empty before the TLS/SSL I/O operation is 26attempted, or SSL_get_error() will not work reliably. 27 28=head1 RETURN VALUES 29 30The following return values can currently occur: 31 32=over 4 33 34=item SSL_ERROR_NONE 35 36The TLS/SSL I/O operation completed. This result code is returned 37if and only if B<ret E<gt> 0>. 38 39=item SSL_ERROR_ZERO_RETURN 40 41The TLS/SSL peer has closed the connection for writing by sending the 42close_notify alert. 43No more data can be read. 44Note that B<SSL_ERROR_ZERO_RETURN> does not necessarily 45indicate that the underlying transport has been closed. 46 47=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE 48 49The operation did not complete and can be retried later. 50 51B<SSL_ERROR_WANT_READ> is returned when the last operation was a read 52operation from a nonblocking B<BIO>. 53It means that not enough data was available at this time to complete the 54operation. 55If at a later time the underlying B<BIO> has data available for reading the same 56function can be called again. 57 58SSL_read() and SSL_read_ex() can also set B<SSL_ERROR_WANT_READ> when there is 59still unprocessed data available at either the B<SSL> or the B<BIO> layer, even 60for a blocking B<BIO>. 61See L<SSL_read(3)> for more information. 62 63B<SSL_ERROR_WANT_WRITE> is returned when the last operation was a write 64to a nonblocking B<BIO> and it was unable to sent all data to the B<BIO>. 65When the B<BIO> is writable again, the same function can be called again. 66 67Note that the retry may again lead to an B<SSL_ERROR_WANT_READ> or 68B<SSL_ERROR_WANT_WRITE> condition. 69There is no fixed upper limit for the number of iterations that 70may be necessary until progress becomes visible at application 71protocol level. 72 73It is safe to call SSL_read() or SSL_read_ex() when more data is available 74even when the call that set this error was an SSL_write() or SSL_write_ex(). 75However, if the call was an SSL_write() or SSL_write_ex(), it should be called 76again to continue sending the application data. 77 78For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or 79poll() on the underlying socket can be used to find out when the 80TLS/SSL I/O function should be retried. 81 82Caveat: Any TLS/SSL I/O function can lead to either of 83B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. 84In particular, 85SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to write data 86and SSL_write() or SSL_write_ex() may want to read data. 87This is mainly because 88TLS/SSL handshakes may occur at any time during the protocol (initiated by 89either the client or the server); SSL_read_ex(), SSL_read(), SSL_peek_ex(), 90SSL_peek(), SSL_write_ex(), and SSL_write() will handle any pending handshakes. 91 92=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT 93 94The operation did not complete; the same TLS/SSL I/O function should be 95called again later. The underlying BIO was not connected yet to the peer 96and the call would block in connect()/accept(). The SSL function should be 97called again when the connection is established. These messages can only 98appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively. 99In order to find out, when the connection has been successfully established, 100on many platforms select() or poll() for writing on the socket file descriptor 101can be used. 102 103=item SSL_ERROR_WANT_X509_LOOKUP 104 105The operation did not complete because an application callback set by 106SSL_CTX_set_client_cert_cb() has asked to be called again. 107The TLS/SSL I/O function should be called again later. 108Details depend on the application. 109 110=item SSL_ERROR_WANT_ASYNC 111 112The operation did not complete because an asynchronous engine is still 113processing data. This will only occur if the mode has been set to SSL_MODE_ASYNC 114using L<SSL_CTX_set_mode(3)> or L<SSL_set_mode(3)> and an asynchronous capable 115engine is being used. An application can determine whether the engine has 116completed its processing using select() or poll() on the asynchronous wait file 117descriptor. This file descriptor is available by calling 118L<SSL_get_all_async_fds(3)> or L<SSL_get_changed_async_fds(3)>. The TLS/SSL I/O 119function should be called again later. The function B<must> be called from the 120same thread that the original call was made from. 121 122=item SSL_ERROR_WANT_ASYNC_JOB 123 124The asynchronous job could not be started because there were no async jobs 125available in the pool (see ASYNC_init_thread(3)). This will only occur if the 126mode has been set to SSL_MODE_ASYNC using L<SSL_CTX_set_mode(3)> or 127L<SSL_set_mode(3)> and a maximum limit has been set on the async job pool 128through a call to L<ASYNC_init_thread(3)>. The application should retry the 129operation after a currently executing asynchronous operation for the current 130thread has completed. 131 132=item SSL_ERROR_WANT_CLIENT_HELLO_CB 133 134The operation did not complete because an application callback set by 135SSL_CTX_set_client_hello_cb() has asked to be called again. 136The TLS/SSL I/O function should be called again later. 137Details depend on the application. 138 139=item SSL_ERROR_SYSCALL 140 141Some non-recoverable, fatal I/O error occurred. The OpenSSL error queue may 142contain more information on the error. For socket I/O on Unix systems, consult 143B<errno> for details. If this error occurs then no further I/O operations should 144be performed on the connection and SSL_shutdown() must not be called. 145 146This value can also be returned for other errors, check the error queue for 147details. 148 149=item SSL_ERROR_SSL 150 151A non-recoverable, fatal error in the SSL library occurred, usually a protocol 152error. The OpenSSL error queue contains more information on the error. If this 153error occurs then no further I/O operations should be performed on the 154connection and SSL_shutdown() must not be called. 155 156=back 157 158=head1 BUGS 159 160The B<SSL_ERROR_SYSCALL> with B<errno> value of 0 indicates unexpected EOF from 161the peer. This will be properly reported as B<SSL_ERROR_SSL> with reason 162code B<SSL_R_UNEXPECTED_EOF_WHILE_READING> in the OpenSSL 3.0 release because 163it is truly a TLS protocol error to terminate the connection without 164a SSL_shutdown(). 165 166The issue is kept unfixed in OpenSSL 1.1.1 releases because many applications 167which choose to ignore this protocol error depend on the existing way of 168reporting the error. 169 170=head1 SEE ALSO 171 172L<ssl(7)> 173 174=head1 HISTORY 175 176The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0. 177The SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1. 178 179=head1 COPYRIGHT 180 181Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved. 182 183Licensed under the OpenSSL license (the "License"). You may not use 184this file except in compliance with the License. You can obtain a copy 185in the file LICENSE in the source distribution or at 186L<https://www.openssl.org/source/license.html>. 187 188=cut 189