1SSL_GET_ERROR(3) OpenSSL SSL_GET_ERROR(3)
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6 SSL_get_error - obtain result code for TLS/SSL I/O operation
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9 #include <openssl/ssl.h>
10 int SSL_get_error(const SSL *ssl, int ret);
12
14 SSL_get_error() returns a result code (suitable for the C "switch"
15 statement) for a preceding call to SSL_connect(), SSL_accept(),
16 SSL_do_handshake(), SSL_read_ex(), SSL_read(), SSL_peek_ex(),
17 SSL_peek(), SSL_shutdown(), SSL_write_ex() or SSL_write() on ssl. The
18 value returned by that TLS/SSL I/O function must be passed to
19 SSL_get_error() in parameter ret.
20 In addition to ssl and ret, SSL_get_error() inspects the current
22 thread's OpenSSL error queue. Thus, SSL_get_error() must be used in
23 the same thread that performed the TLS/SSL I/O operation, and no other
24 OpenSSL function calls should appear in between. The current thread's
25 error queue must be empty before the TLS/SSL I/O operation is
26 attempted, or SSL_get_error() will not work reliably.
27
29 The following return values can currently occur:
30 SSL_ERROR_NONE
32 The TLS/SSL I/O operation completed. This result code is returned
33 if and only if ret > 0.
34 SSL_ERROR_ZERO_RETURN
36 The TLS/SSL peer has closed the connection for writing by sending
37 the close_notify alert. No more data can be read. Note that
38 SSL_ERROR_ZERO_RETURN does not necessarily indicate that the
39 underlying transport has been closed.
40 SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
42 The operation did not complete and can be retried later.
43 SSL_ERROR_WANT_READ is returned when the last operation was a read
45 operation from a nonblocking BIO. It means that not enough data
46 was available at this time to complete the operation. If at a
47 later time the underlying BIO has data available for reading the
48 same function can be called again.
49 SSL_read() and SSL_read_ex() can also set SSL_ERROR_WANT_READ when
51 there is still unprocessed data available at either the SSL or the
52 BIO layer, even for a blocking BIO. See SSL_read(3) for more
53 information.
54 SSL_ERROR_WANT_WRITE is returned when the last operation was a
56 write to a nonblocking BIO and it was unable to sent all data to
57 the BIO. When the BIO is writable again, the same function can be
58 called again.
59 Note that the retry may again lead to an SSL_ERROR_WANT_READ or
61 SSL_ERROR_WANT_WRITE condition. There is no fixed upper limit for
62 the number of iterations that may be necessary until progress
63 becomes visible at application protocol level.
64 It is safe to call SSL_read() or SSL_read_ex() when more data is
66 available even when the call that set this error was an SSL_write()
67 or SSL_write_ex(). However, if the call was an SSL_write() or
68 SSL_write_ex(), it should be called again to continue sending the
69 application data.
70 For socket BIOs (e.g. when SSL_set_fd() was used), select() or
72 poll() on the underlying socket can be used to find out when the
73 TLS/SSL I/O function should be retried.
74 Caveat: Any TLS/SSL I/O function can lead to either of
76 SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE. In particular,
77 SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to
78 write data and SSL_write() or SSL_write_ex() may want to read data.
79 This is mainly because TLS/SSL handshakes may occur at any time
80 during the protocol (initiated by either the client or the server);
81 SSL_read_ex(), SSL_read(), SSL_peek_ex(), SSL_peek(),
82 SSL_write_ex(), and SSL_write() will handle any pending handshakes.
83 SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
85 The operation did not complete; the same TLS/SSL I/O function
86 should be called again later. The underlying BIO was not connected
87 yet to the peer and the call would block in connect()/accept(). The
88 SSL function should be called again when the connection is
89 established. These messages can only appear with a BIO_s_connect()
90 or BIO_s_accept() BIO, respectively. In order to find out, when
91 the connection has been successfully established, on many platforms
92 select() or poll() for writing on the socket file descriptor can be
93 used.
94 SSL_ERROR_WANT_X509_LOOKUP
96 The operation did not complete because an application callback set
97 by SSL_CTX_set_client_cert_cb() has asked to be called again. The
98 TLS/SSL I/O function should be called again later. Details depend
99 on the application.
100 SSL_ERROR_WANT_ASYNC
102 The operation did not complete because an asynchronous engine is
103 still processing data. This will only occur if the mode has been
104 set to SSL_MODE_ASYNC using SSL_CTX_set_mode(3) or SSL_set_mode(3)
105 and an asynchronous capable engine is being used. An application
106 can determine whether the engine has completed its processing using
107 select() or poll() on the asynchronous wait file descriptor. This
108 file descriptor is available by calling SSL_get_all_async_fds(3) or
109 SSL_get_changed_async_fds(3). The TLS/SSL I/O function should be
110 called again later. The function must be called from the same
111 thread that the original call was made from.
112 SSL_ERROR_WANT_ASYNC_JOB
114 The asynchronous job could not be started because there were no
115 async jobs available in the pool (see ASYNC_init_thread(3)). This
116 will only occur if the mode has been set to SSL_MODE_ASYNC using
117 SSL_CTX_set_mode(3) or SSL_set_mode(3) and a maximum limit has been
118 set on the async job pool through a call to ASYNC_init_thread(3).
119 The application should retry the operation after a currently
120 executing asynchronous operation for the current thread has
121 completed.
122 SSL_ERROR_WANT_CLIENT_HELLO_CB
124 The operation did not complete because an application callback set
125 by SSL_CTX_set_client_hello_cb() has asked to be called again. The
126 TLS/SSL I/O function should be called again later. Details depend
127 on the application.
128 SSL_ERROR_SYSCALL
130 Some non-recoverable, fatal I/O error occurred. The OpenSSL error
131 queue may contain more information on the error. For socket I/O on
132 Unix systems, consult errno for details. If this error occurs then
133 no further I/O operations should be performed on the connection and
134 SSL_shutdown() must not be called.
135 This value can also be returned for other errors, check the error
137 queue for details.
138 SSL_ERROR_SSL
140 A non-recoverable, fatal error in the SSL library occurred, usually
141 a protocol error. The OpenSSL error queue contains more
142 information on the error. If this error occurs then no further I/O
143 operations should be performed on the connection and SSL_shutdown()
144 must not be called.
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147 The SSL_ERROR_SYSCALL with errno value of 0 indicates unexpected EOF
148 from the peer. This will be properly reported as SSL_ERROR_SSL with
149 reason code SSL_R_UNEXPECTED_EOF_WHILE_READING in the OpenSSL 3.0
150 release because it is truly a TLS protocol error to terminate the
151 connection without a SSL_shutdown().
152 The issue is kept unfixed in OpenSSL 1.1.1 releases because many
154 applications which choose to ignore this protocol error depend on the
155 existing way of reporting the error.
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158 ssl(7)
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161 The SSL_ERROR_WANT_ASYNC error code was added in OpenSSL 1.1.0. The
162 SSL_ERROR_WANT_CLIENT_HELLO_CB error code was added in OpenSSL 1.1.1.
163
165 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
166 Licensed under the OpenSSL license (the "License"). You may not use
168 this file except in compliance with the License. You can obtain a copy
169 in the file LICENSE in the source distribution or at
170 <https://www.openssl.org/source/license.html>.
1711.1.1i 2021-07-22 SSL_GET_ERROR(3)