.\" $OpenBSD: SSL_get_error.3,v 1.5 2018/04/29 07:37:01 guenther Exp $ .\" OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400 .\" .\" This file was written by Bodo Moeller . .\" Copyright (c) 2000, 2001, 2002, 2005 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: April 29 2018 $ .Dt SSL_GET_ERROR 3 .Os .Sh NAME .Nm SSL_get_error .Nd obtain result code for TLS/SSL I/O operation .Sh SYNOPSIS .In openssl/ssl.h .Ft int .Fn SSL_get_error "const SSL *ssl" "int ret" .Sh DESCRIPTION .Fn SSL_get_error returns a result code (suitable for the C .Dq switch statement) for a preceding call to .Xr SSL_connect 3 , .Xr SSL_accept 3 , .Xr SSL_do_handshake 3 , .Xr SSL_read 3 , .Xr SSL_peek 3 , or .Xr SSL_write 3 on .Fa ssl . The value returned by that TLS/SSL I/O function must be passed to .Fn SSL_get_error in parameter .Fa ret . .Pp In addition to .Fa ssl and .Fa ret , .Fn SSL_get_error inspects the current thread's OpenSSL error queue. Thus, .Fn 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 .Fn SSL_get_error will not work reliably. .Sh RETURN VALUES The following return values can currently occur: .Bl -tag -width Ds .It Dv SSL_ERROR_NONE The TLS/SSL I/O operation completed. This result code is returned if and only if .Fa ret > 0. .It Dv SSL_ERROR_ZERO_RETURN The TLS/SSL connection has been closed. If the protocol version is SSL 3.0 or TLS 1.0, this result code is returned only if a closure alert has occurred in the protocol, i.e., if the connection has been closed cleanly. Note that in this case .Dv SSL_ERROR_ZERO_RETURN does not necessarily indicate that the underlying transport has been closed. .It Dv SSL_ERROR_WANT_READ , Dv SSL_ERROR_WANT_WRITE The operation did not complete; the same TLS/SSL I/O function should be called again later. If, by then, the underlying .Vt BIO has data available for reading (if the result code is .Dv SSL_ERROR_WANT_READ ) or allows writing data .Pq Dv SSL_ERROR_WANT_WRITE , then some TLS/SSL protocol progress will take place, i.e., at least part of a TLS/SSL record will be read or written. Note that the retry may again lead to a .Dv SSL_ERROR_WANT_READ or .Dv 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. .Pp For socket .Fa BIO Ns s (e.g., when .Fn SSL_set_fd was used), .Xr select 2 or .Xr poll 2 on the underlying socket can be used to find out when the TLS/SSL I/O function should be retried. .Pp Caveat: Any TLS/SSL I/O function can lead to either of .Dv SSL_ERROR_WANT_READ and .Dv SSL_ERROR_WANT_WRITE . In particular, .Xr SSL_read 3 or .Xr SSL_peek 3 may want to write data and .Xr SSL_write 3 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); .Xr SSL_read 3 , .Xr SSL_peek 3 , and .Xr SSL_write 3 will handle any pending handshakes. .It Dv SSL_ERROR_WANT_CONNECT , Dv 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 .Xr connect 2 Ns / Ns .Xr accept 2 . The SSL function should be called again when the connection is established. These messages can only appear with a .Xr BIO_s_connect 3 or .Xr BIO_s_accept 3 .Vt BIO , respectively. In order to find out when the connection has been successfully established, on many platforms .Xr select 2 or .Xr poll 2 for writing on the socket file descriptor can be used. .It Dv SSL_ERROR_WANT_X509_LOOKUP The operation did not complete because an application callback set by .Xr SSL_CTX_set_client_cert_cb 3 has asked to be called again. The TLS/SSL I/O function should be called again later. Details depend on the application. .It Dv SSL_ERROR_SYSCALL Some I/O error occurred. The OpenSSL error queue may contain more information on the error. If the error queue is empty (i.e., .Fn ERR_get_error returns 0), .Fa ret can be used to find out more about the error: If .Fa ret == 0, an .Dv EOF was observed that violates the protocol. If .Fa ret == \(mi1, the underlying .Vt BIO reported an I/O error (for socket I/O on Unix systems, consult .Dv errno for details). .It Dv SSL_ERROR_SSL A failure in the SSL library occurred, usually a protocol error. The OpenSSL error queue contains more information on the error. .El .Sh SEE ALSO .Xr err 3 , .Xr ssl 3 .Sh HISTORY .Fn SSL_get_error first appeared in SSLeay 0.8.0 and have been available since .Ox 2.4 .