1.\" 2.\" $OpenBSD: SSL_get_error.3,v 1.1 2016/11/05 15:32:20 schwarze Exp $ 3.\" 4.Dd $Mdocdate: November 5 2016 $ 5.Dt SSL_GET_ERROR 3 6.Os 7.Sh NAME 8.Nm SSL_get_error 9.Nd obtain result code for TLS/SSL I/O operation 10.Sh SYNOPSIS 11.In openssl/ssl.h 12.Ft int 13.Fn SSL_get_error "const SSL *ssl" "int ret" 14.Sh DESCRIPTION 15.Fn SSL_get_error 16returns a result code (suitable for the C 17.Dq switch 18statement) for a preceding call to 19.Xr SSL_connect 3 , 20.Xr SSL_accept 3 , 21.Xr SSL_do_handshake 3 , 22.Xr SSL_read 3 , 23.Xr SSL_peek 3 , 24or 25.Xr SSL_write 3 26on 27.Fa ssl . 28The value returned by that TLS/SSL I/O function must be passed to 29.Fn SSL_get_error 30in parameter 31.Fa ret . 32.Pp 33In addition to 34.Fa ssl 35and 36.Fa ret , 37.Fn SSL_get_error 38inspects the current thread's OpenSSL error queue. 39Thus, 40.Fn SSL_get_error 41must be used in the same thread that performed the TLS/SSL I/O operation, 42and no other OpenSSL function calls should appear in between. 43The current thread's error queue must be empty before the TLS/SSL I/O operation 44is attempted, or 45.Fn SSL_get_error 46will not work reliably. 47.Sh RETURN VALUES 48The following return values can currently occur: 49.Bl -tag -width Ds 50.It Dv SSL_ERROR_NONE 51The TLS/SSL I/O operation completed. 52This result code is returned if and only if 53.Fa ret 54< 0. 55.It Dv SSL_ERROR_ZERO_RETURN 56The TLS/SSL connection has been closed. 57If the protocol version is SSL 3.0 or TLS 1.0, this result code is returned 58only if a closure alert has occurred in the protocol, i.e., if the connection 59has been closed cleanly. 60Note that in this case 61.Dv SSL_ERROR_ZERO_RETURN 62does not necessarily indicate that the underlying transport has been closed. 63.It Dv SSL_ERROR_WANT_READ , Dv SSL_ERROR_WANT_WRITE 64The operation did not complete; 65the same TLS/SSL I/O function should be called again later. 66If, by then, the underlying 67.Vt BIO 68has data available for reading (if the result code is 69.Dv SSL_ERROR_WANT_READ ) 70or allows writing data 71.Pq Dv SSL_ERROR_WANT_WRITE , 72then some TLS/SSL protocol progress will take place, 73i.e., at least part of a TLS/SSL record will be read or written. 74Note that the retry may again lead to a 75.Dv SSL_ERROR_WANT_READ 76or 77.Dv SSL_ERROR_WANT_WRITE 78condition. 79There is no fixed upper limit for the number of iterations that may be 80necessary until progress becomes visible at application protocol level. 81.Pp 82For socket 83.Fa BIO Ns 84s (e.g., when 85.Fn SSL_set_fd 86was used), 87.Xr select 2 88or 89.Xr poll 2 90on the underlying socket can be used to find out when the TLS/SSL I/O function 91should be retried. 92.Pp 93Caveat: Any TLS/SSL I/O function can lead to either of 94.Dv SSL_ERROR_WANT_READ 95and 96.Dv SSL_ERROR_WANT_WRITE . 97In particular, 98.Xr SSL_read 3 99or 100.Xr SSL_peek 3 101may want to write data and 102.Xr SSL_write 3 103may want 104to read data. 105This is mainly because TLS/SSL handshakes may occur at any time during the 106protocol (initiated by either the client or the server); 107.Xr SSL_read 3 , 108.Xr SSL_peek 3 , 109and 110.Xr SSL_write 3 111will handle any pending handshakes. 112.It Dv SSL_ERROR_WANT_CONNECT , Dv SSL_ERROR_WANT_ACCEPT 113The operation did not complete; the same TLS/SSL I/O function should be 114called again later. 115The underlying BIO was not connected yet to the peer and the call would block 116in 117.Xr connect 2 Ns / Ns 118.Xr accept 2 . 119The SSL function should be 120called again when the connection is established. 121These messages can only appear with a 122.Xr BIO_s_connect 3 123or 124.Xr BIO_s_accept 3 125.Vt BIO , 126respectively. 127In order to find out when the connection has been successfully established, 128on many platforms 129.Xr select 2 130or 131.Xr poll 2 132for writing on the socket file descriptor can be used. 133.It Dv SSL_ERROR_WANT_X509_LOOKUP 134The operation did not complete because an application callback set by 135.Xr SSL_CTX_set_client_cert_cb 3 136has asked to be called again. 137The TLS/SSL I/O function should be called again later. 138Details depend on the application. 139.It Dv SSL_ERROR_SYSCALL 140Some I/O error occurred. 141The OpenSSL error queue may contain more information on the error. 142If the error queue is empty (i.e., 143.Fn ERR_get_error 144returns 0), 145.Fa ret 146can be used to find out more about the error: 147If 148.Fa ret 149== 0, an 150.Dv EOF 151was observed that violates the protocol. 152If 153.Fa ret 154== \(mi1, the underlying 155.Vt BIO 156reported an 157I/O error (for socket I/O on Unix systems, consult 158.Dv errno 159for details). 160.It Dv SSL_ERROR_SSL 161A failure in the SSL library occurred, usually a protocol error. 162The OpenSSL error queue contains more information on the error. 163.El 164.Sh SEE ALSO 165.Xr err 3 , 166.Xr ssl 3 167.Sh HISTORY 168.Fn SSL_get_error 169was added in SSLeay 0.8. 170