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 NOTES 29 30Some TLS implementations do not send a close_notify alert on shutdown. 31 32On an unexpected EOF, versions before OpenSSL 3.0 returned 33B<SSL_ERROR_SYSCALL>, nothing was added to the error stack, and errno was 0. 34Since OpenSSL 3.0 the returned error is B<SSL_ERROR_SSL> with a meaningful 35error on the error stack. 36 37=head1 RETURN VALUES 38 39The following return values can currently occur: 40 41=over 4 42 43=item SSL_ERROR_NONE 44 45The TLS/SSL I/O operation completed. This result code is returned 46if and only if B<ret E<gt> 0>. 47 48=item SSL_ERROR_ZERO_RETURN 49 50The TLS/SSL peer has closed the connection for writing by sending the 51close_notify alert. 52No more data can be read. 53Note that B<SSL_ERROR_ZERO_RETURN> does not necessarily 54indicate that the underlying transport has been closed. 55 56This error can also appear when the option B<SSL_OP_IGNORE_UNEXPECTED_EOF> 57is set. See L<SSL_CTX_set_options(3)> for more details. 58 59=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE 60 61The operation did not complete and can be retried later. 62 63B<SSL_ERROR_WANT_READ> is returned when the last operation was a read 64operation from a nonblocking B<BIO>. 65It means that not enough data was available at this time to complete the 66operation. 67If at a later time the underlying B<BIO> has data available for reading the same 68function can be called again. 69 70SSL_read() and SSL_read_ex() can also set B<SSL_ERROR_WANT_READ> when there is 71still unprocessed data available at either the B<SSL> or the B<BIO> layer, even 72for a blocking B<BIO>. 73See L<SSL_read(3)> for more information. 74 75B<SSL_ERROR_WANT_WRITE> is returned when the last operation was a write 76to a nonblocking B<BIO> and it was unable to sent all data to the B<BIO>. 77When the B<BIO> is writable again, the same function can be called again. 78 79Note that the retry may again lead to an B<SSL_ERROR_WANT_READ> or 80B<SSL_ERROR_WANT_WRITE> condition. 81There is no fixed upper limit for the number of iterations that 82may be necessary until progress becomes visible at application 83protocol level. 84 85It is safe to call SSL_read() or SSL_read_ex() when more data is available 86even when the call that set this error was an SSL_write() or SSL_write_ex(). 87However, if the call was an SSL_write() or SSL_write_ex(), it should be called 88again to continue sending the application data. If you get B<SSL_ERROR_WANT_WRITE> 89from SSL_write() or SSL_write_ex() then you should not do any other operation 90that could trigger B<IO> other than to repeat the previous SSL_write() call. 91 92For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or 93poll() on the underlying socket can be used to find out when the 94TLS/SSL I/O function should be retried. 95 96Caveat: Any TLS/SSL I/O function can lead to either of 97B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. 98In particular, 99SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to write data 100and SSL_write() or SSL_write_ex() may want to read data. 101This is mainly because 102TLS/SSL handshakes may occur at any time during the protocol (initiated by 103either the client or the server); SSL_read_ex(), SSL_read(), SSL_peek_ex(), 104SSL_peek(), SSL_write_ex(), and SSL_write() will handle any pending handshakes. 105 106=item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT 107 108The operation did not complete; the same TLS/SSL I/O function should be 109called again later. The underlying BIO was not connected yet to the peer 110and the call would block in connect()/accept(). The SSL function should be 111called again when the connection is established. These messages can only 112appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively. 113In order to find out, when the connection has been successfully established, 114on many platforms select() or poll() for writing on the socket file descriptor 115can be used. 116 117=item SSL_ERROR_WANT_X509_LOOKUP 118 119The operation did not complete because an application callback set by 120SSL_CTX_set_client_cert_cb() has asked to be called again. 121The TLS/SSL I/O function should be called again later. 122Details depend on the application. 123 124=item SSL_ERROR_WANT_ASYNC 125 126The operation did not complete because an asynchronous engine is still 127processing data. This will only occur if the mode has been set to SSL_MODE_ASYNC 128using L<SSL_CTX_set_mode(3)> or L<SSL_set_mode(3)> and an asynchronous capable 129engine is being used. An application can determine whether the engine has 130completed its processing using select() or poll() on the asynchronous wait file 131descriptor. This file descriptor is available by calling 132L<SSL_get_all_async_fds(3)> or L<SSL_get_changed_async_fds(3)>. The TLS/SSL I/O 133function should be called again later. The function B<must> be called from the 134same thread that the original call was made from. 135 136=item SSL_ERROR_WANT_ASYNC_JOB 137 138The asynchronous job could not be started because there were no async jobs 139available in the pool (see ASYNC_init_thread(3)). This will only occur if the 140mode has been set to SSL_MODE_ASYNC using L<SSL_CTX_set_mode(3)> or 141L<SSL_set_mode(3)> and a maximum limit has been set on the async job pool 142through a call to L<ASYNC_init_thread(3)>. The application should retry the 143operation after a currently executing asynchronous operation for the current 144thread has completed. 145 146=item SSL_ERROR_WANT_CLIENT_HELLO_CB 147 148The operation did not complete because an application callback set by 149SSL_CTX_set_client_hello_cb() has asked to be called again. 150The TLS/SSL I/O function should be called again later. 151Details depend on the application. 152 153=item SSL_ERROR_SYSCALL 154 155Some non-recoverable, fatal I/O error occurred. The OpenSSL error queue may 156contain more information on the error. For socket I/O on Unix systems, consult 157B<errno> for details. If this error occurs then no further I/O operations should 158be performed on the connection and SSL_shutdown() must not be called. 159 160This value can also be returned for other errors, check the error queue for 161details. 162 163=item SSL_ERROR_SSL 164 165A non-recoverable, fatal error in the SSL library occurred, usually a protocol 166error. The OpenSSL error queue contains more information on the error. If this 167error occurs then no further I/O operations should be performed on the 168connection and SSL_shutdown() must not be called. 169 170=back 171 172=head1 SEE ALSO 173 174L<ssl(7)> 175 176=head1 HISTORY 177 178The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0. 179The SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1. 180 181=head1 COPYRIGHT 182 183Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 184 185Licensed under the Apache License 2.0 (the "License"). You may not use 186this file except in compliance with the License. You can obtain a copy 187in the file LICENSE in the source distribution or at 188L<https://www.openssl.org/source/license.html>. 189 190=cut 191