SSL_GET_ERROR(3) BSD Library Functions Manual 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” state‐
ment) for a preceding call to SSL_connect(3), SSL_accept(3),
SSL_do_handshake(3), SSL_read(3), SSL_peek(3), or SSL_write(3) 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 connec‐
tion has been closed cleanly. Note that in this case
SSL_ERROR_ZERO_RETURN does not necessarily indicate that the
underlying transport 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 a 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.
For socket BIOs (e.g., when SSL_set_fd() was used), select(2) or
poll(2) 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 particular,
SSL_read(3) or SSL_peek(3) may want to write data and
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); SSL_read(3),
SSL_peek(3), and SSL_write(3) 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 con‐
nected yet to the peer and the call would block in
connect(2)/accept(2). The SSL function should be called again
when the connection is established. These messages can only
appear with a BIO_s_connect(3) or BIO_s_accept(3) BIO, respec‐
tively. In order to find out when the connection has been suc‐
cessfully established, on many platforms select(2) or poll(2) 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(3) 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 vio‐
lates 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 protocol error.
The OpenSSL error queue contains more information on the error.
SEE ALSOerr(3), ssl(3)HISTORYSSL_get_error() was added in SSLeay 0.8.
BSD April 27, 2024 BSD
