trusty (3) SSL_get_error.3ssl.gz

NAME

       SSL_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);

DESCRIPTION

       SSL_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 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 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.

           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 particular, 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 protocol error.  The OpenSSL error queue contains
           more information on the error.

SEE ALSO

       ssl(3), err(3)

HISTORY

       SSL_get_error() was added in SSLeay 0.8.