SSL_GET_ERROR(3) OpenSSL SSL_GET_ERROR(3)NAMESSL_get_error - obtain result code for TLS/SSL I/O operation
SYNOPSIS
#include <openssl/ssl.h>
int SSL_get_error(const SSL *ssl, int ret);
DESCRIPTIONSSL_get_error() returns a result code (suitable for the C
"switch" statement) for a preceding call to SSL_connect(),
SSL_accept(), SSL_do_handshake(), SSL_read(), SSL_peek(), or
SSL_write() on ssl. The value returned by that TLS/SSL I/O
function must be passed to SSL_get_error() in parameter ret.
In addition to ssl and ret, SSL_get_error() inspects the
current thread's OpenSSL error queue. Thus, 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
SSL_get_error() will not work reliably.
RETURN VALUES
The following return values can currently occur:
SSL_ERROR_NONE
The TLS/SSL I/O operation completed. This result code
is returned if and only if ret > 0.
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 SSL_ERROR_ZERO_RETURN
does not necessarily indicate that the underlying tran-
sport has been closed.
SSL_ERROR_WANT_READ, 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 BIO has data available for reading (if the
result code is SSL_ERROR_WANT_READ) or allows writing
data (SSL_ERROR_WANT_WRITE), then some TLS/SSL protocol
progress will take place, i.e. at least part of an
TLS/SSL record will be read or written. Note that the
retry may again lead to a SSL_ERROR_WANT_READ or
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.
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SSL_GET_ERROR(3) OpenSSL SSL_GET_ERROR(3)
For socket BIOs (e.g. when SSL_set_fd() was used),
select() or poll() on the underlying socket can be used
to find out when the TLS/SSL I/O function should be
retried.
Caveat: Any TLS/SSL I/O function can lead to either of
SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE. In par-
ticular, SSL_read() or SSL_peek() may want to write data
and SSL_write() 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); SSL_read(), SSL_peek(), and SSL_write() will
handle any pending handshakes.
SSL_ERROR_WANT_CONNECT, 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 connect()/accept(). The SSL function should be
called again when the connection is established. These
messages can only appear with a BIO_s_connect() or
BIO_s_accept() BIO, respectively. In order to find out,
when the connection has been successfully established,
on many platforms select() or poll() for writing on the
socket file descriptor can be used.
SSL_ERROR_WANT_X509_LOOKUP
The operation did not complete because an application
callback set by SSL_CTX_set_client_cert_cb() has asked
to be called again. The TLS/SSL I/O function should be
called again later. Details depend on the application.
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. ERR_get_error() returns 0), ret can
be used to find out more about the error: If ret == 0,
an EOF was observed that violates the protocol. If ret
== -1, the underlying BIO reported an I/O error (for
socket I/O on Unix systems, consult errno for details).
SSL_ERROR_SSL
A failure in the SSL library occurred, usually a proto-
col error. The OpenSSL error queue contains more infor-
mation on the error.
SEE ALSOssl(3), err(3)HISTORYSSL_get_error() was added in SSLeay 0.8.
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