5 SSL_get_error - obtain result code for TLS/SSL I/O operation
9 #include <openssl/ssl.h>
11 int SSL_get_error(const SSL *ssl, int ret);
15 SSL_get_error() returns a result code (suitable for the C "switch"
16 statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
17 SSL_read_ex(), SSL_read(), SSL_peek_ex(), SSL_peek(), SSL_write_ex() or
18 SSL_write() on B<ssl>. The value returned by that TLS/SSL I/O function must be
19 passed to SSL_get_error() in parameter B<ret>.
21 In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
22 current thread's OpenSSL error queue. Thus, SSL_get_error() must be
23 used in the same thread that performed the TLS/SSL I/O operation, and no
24 other OpenSSL function calls should appear in between. The current
25 thread's error queue must be empty before the TLS/SSL I/O operation is
26 attempted, or SSL_get_error() will not work reliably.
30 The following return values can currently occur:
36 The TLS/SSL I/O operation completed. This result code is returned
37 if and only if B<ret E<gt> 0>.
39 =item SSL_ERROR_ZERO_RETURN
41 The TLS/SSL peer has closed the connection for writing by sending the
43 No more data can be read.
44 Note that B<SSL_ERROR_ZERO_RETURN> does not necessarily
45 indicate that the underlying transport has been closed.
47 =item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
49 The operation did not complete and can be retried later.
51 B<SSL_ERROR_WANT_READ> is returned when the last operation was a read
52 operation from a non-blocking B<BIO>.
53 It means that not enough data was available at this time to complete the
55 If at a later time the underlying B<BIO> has data available for reading the same
56 function can be called again.
58 SSL_read() and SSL_read_ex() can also set B<SSL_ERROR_WANT_READ> when there is
59 still unprocessed data available at either the B<SSL> or the B<BIO> layer, even
60 for a blocking B<BIO>.
61 See L<SSL_read(3)> for more information.
63 B<SSL_ERROR_WANT_WRITE> is returned when the last operation was a write
64 to a non-blocking B<BIO> and it was unable to sent all data to the B<BIO>.
65 When the B<BIO> is writeable again, the same function can be called again.
67 Note that the retry may again lead to an B<SSL_ERROR_WANT_READ> or
68 B<SSL_ERROR_WANT_WRITE> condition.
69 There is no fixed upper limit for the number of iterations that
70 may be necessary until progress becomes visible at application
73 It is safe to call SSL_read() or SSL_read_ex() when more data is available
74 even when the call that set this error was an SSL_write() or SSL_write_ex().
75 However if the call was an SSL_write() or SSL_write_ex(), it should be called
76 again to continue sending the application data.
78 For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
79 poll() on the underlying socket can be used to find out when the
80 TLS/SSL I/O function should be retried.
82 Caveat: Any TLS/SSL I/O function can lead to either of
83 B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>.
85 SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to write data
86 and SSL_write() or SSL_write_ex() may want to read data.
87 This is mainly because
88 TLS/SSL handshakes may occur at any time during the protocol (initiated by
89 either the client or the server); SSL_read_ex(), SSL_read(), SSL_peek_ex(),
90 SSL_peek(), SSL_write_ex(), and SSL_write() will handle any pending handshakes.
92 =item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
94 The operation did not complete; the same TLS/SSL I/O function should be
95 called again later. The underlying BIO was not connected yet to the peer
96 and the call would block in connect()/accept(). The SSL function should be
97 called again when the connection is established. These messages can only
98 appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
99 In order to find out, when the connection has been successfully established,
100 on many platforms select() or poll() for writing on the socket file descriptor
103 =item SSL_ERROR_WANT_X509_LOOKUP
105 The operation did not complete because an application callback set by
106 SSL_CTX_set_client_cert_cb() has asked to be called again.
107 The TLS/SSL I/O function should be called again later.
108 Details depend on the application.
110 =item SSL_ERROR_WANT_ASYNC
112 The operation did not complete because an asynchronous engine is still
113 processing data. This will only occur if the mode has been set to SSL_MODE_ASYNC
114 using L<SSL_CTX_set_mode(3)> or L<SSL_set_mode(3)> and an asynchronous capable
115 engine is being used. An application can determine whether the engine has
116 completed its processing using select() or poll() on the asynchronous wait file
117 descriptor. This file descriptor is available by calling
118 L<SSL_get_all_async_fds(3)> or L<SSL_get_changed_async_fds(3)>. The TLS/SSL I/O
119 function should be called again later. The function B<must> be called from the
120 same thread that the original call was made from.
122 =item SSL_ERROR_WANT_ASYNC_JOB
124 The asynchronous job could not be started because there were no async jobs
125 available in the pool (see ASYNC_init_thread(3)). This will only occur if the
126 mode has been set to SSL_MODE_ASYNC using L<SSL_CTX_set_mode(3)> or
127 L<SSL_set_mode(3)> and a maximum limit has been set on the async job pool
128 through a call to L<ASYNC_init_thread(3)>. The application should retry the
129 operation after a currently executing asynchronous operation for the current
130 thread has completed.
132 =item SSL_ERROR_WANT_CLIENT_HELLO_CB
134 The operation did not complete because an application callback set by
135 SSL_CTX_set_client_hello_cb() has asked to be called again.
136 The TLS/SSL I/O function should be called again later.
137 Details depend on the application.
139 =item SSL_ERROR_SYSCALL
141 Some non-recoverable I/O error occurred.
142 The OpenSSL error queue may contain more information on the error.
143 For socket I/O on Unix systems, consult B<errno> for details.
145 This value can also be returned for other errors, check the error queue for
150 A failure in the SSL library occurred, usually a protocol error. The
151 OpenSSL error queue contains more information on the error.
161 The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0.
162 The SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1.
166 Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
168 Licensed under the Apache License 2.0 (the "License"). You may not use
169 this file except in compliance with the License. You can obtain a copy
170 in the file LICENSE in the source distribution or at
171 L<https://www.openssl.org/source/license.html>.