234 lines
8.8 KiB
Groff
234 lines
8.8 KiB
Groff
.\" $NetBSD: SSL_get_error.3,v 1.16 2005/11/25 21:09:34 christos Exp $
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.\" ========================================================================
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.\"
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.IX Title "SSL_get_error 3"
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.TH SSL_get_error 3 "2005-04-23" "0.9.8a" "OpenSSL"
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.SH "NAME"
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SSL_get_error \- obtain result code for TLS/SSL I/O operation
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.SH "LIBRARY"
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libcrypto, -lcrypto
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/ssl.h>
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.Ve
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.PP
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.Vb 1
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\& int SSL_get_error(const SSL *ssl, int ret);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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\&\fISSL_get_error()\fR returns a result code (suitable for the C \*(L"switch\*(R"
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statement) for a preceding call to \fISSL_connect()\fR, \fISSL_accept()\fR, \fISSL_do_handshake()\fR,
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\&\fISSL_read()\fR, \fISSL_peek()\fR, or \fISSL_write()\fR on \fBssl\fR. The value returned by
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that \s-1TLS/SSL\s0 I/O function must be passed to \fISSL_get_error()\fR in parameter
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\&\fBret\fR.
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.PP
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In addition to \fBssl\fR and \fBret\fR, \fISSL_get_error()\fR inspects the
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current thread's OpenSSL error queue. Thus, \fISSL_get_error()\fR must be
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used in the same thread that performed the \s-1TLS/SSL\s0 I/O operation, and no
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other OpenSSL function calls should appear in between. The current
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thread's error queue must be empty before the \s-1TLS/SSL\s0 I/O operation is
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attempted, or \fISSL_get_error()\fR will not work reliably.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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The following return values can currently occur:
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.IP "\s-1SSL_ERROR_NONE\s0" 4
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.IX Item "SSL_ERROR_NONE"
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The \s-1TLS/SSL\s0 I/O operation completed. This result code is returned
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if and only if \fBret > 0\fR.
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.IP "\s-1SSL_ERROR_ZERO_RETURN\s0" 4
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.IX Item "SSL_ERROR_ZERO_RETURN"
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The \s-1TLS/SSL\s0 connection has been closed. If the protocol version is \s-1SSL\s0 3.0
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or \s-1TLS\s0 1.0, this result code is returned only if a closure
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alert has occurred in the protocol, i.e. if the connection has been
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closed cleanly. Note that in this case \fB\s-1SSL_ERROR_ZERO_RETURN\s0\fR
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does not necessarily indicate that the underlying transport
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has been closed.
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.IP "\s-1SSL_ERROR_WANT_READ\s0, \s-1SSL_ERROR_WANT_WRITE\s0" 4
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.IX Item "SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE"
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The operation did not complete; the same \s-1TLS/SSL\s0 I/O function should be
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called again later. If, by then, the underlying \fB\s-1BIO\s0\fR has data
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available for reading (if the result code is \fB\s-1SSL_ERROR_WANT_READ\s0\fR)
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or allows writing data (\fB\s-1SSL_ERROR_WANT_WRITE\s0\fR), then some \s-1TLS/SSL\s0
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protocol progress will take place, i.e. at least part of an \s-1TLS/SSL\s0
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record will be read or written. Note that the retry may again lead to
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a \fB\s-1SSL_ERROR_WANT_READ\s0\fR or \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR condition.
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There is no fixed upper limit for the number of iterations that
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may be necessary until progress becomes visible at application
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protocol level.
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.Sp
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For socket \fB\s-1BIO\s0\fRs (e.g. when \fISSL_set_fd()\fR was used), \fIselect()\fR or
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\&\fIpoll()\fR on the underlying socket can be used to find out when the
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\&\s-1TLS/SSL\s0 I/O function should be retried.
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.Sp
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Caveat: Any \s-1TLS/SSL\s0 I/O function can lead to either of
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\&\fB\s-1SSL_ERROR_WANT_READ\s0\fR and \fB\s-1SSL_ERROR_WANT_WRITE\s0\fR. In particular,
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\&\fISSL_read()\fR or \fISSL_peek()\fR may want to write data and \fISSL_write()\fR may want
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to read data. This is mainly because \s-1TLS/SSL\s0 handshakes may occur at any
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time during the protocol (initiated by either the client or the server);
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\&\fISSL_read()\fR, \fISSL_peek()\fR, and \fISSL_write()\fR will handle any pending handshakes.
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.IP "\s-1SSL_ERROR_WANT_CONNECT\s0, \s-1SSL_ERROR_WANT_ACCEPT\s0" 4
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.IX Item "SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT"
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The operation did not complete; the same \s-1TLS/SSL\s0 I/O function should be
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called again later. The underlying \s-1BIO\s0 was not connected yet to the peer
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and the call would block in \fIconnect()\fR/\fIaccept()\fR. The \s-1SSL\s0 function should be
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called again when the connection is established. These messages can only
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appear with a \fIBIO_s_connect()\fR or \fIBIO_s_accept()\fR \s-1BIO\s0, respectively.
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In order to find out, when the connection has been successfully established,
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on many platforms \fIselect()\fR or \fIpoll()\fR for writing on the socket file descriptor
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can be used.
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.IP "\s-1SSL_ERROR_WANT_X509_LOOKUP\s0" 4
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.IX Item "SSL_ERROR_WANT_X509_LOOKUP"
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The operation did not complete because an application callback set by
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\&\fISSL_CTX_set_client_cert_cb()\fR has asked to be called again.
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The \s-1TLS/SSL\s0 I/O function should be called again later.
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Details depend on the application.
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.IP "\s-1SSL_ERROR_SYSCALL\s0" 4
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.IX Item "SSL_ERROR_SYSCALL"
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Some I/O error occurred. The OpenSSL error queue may contain more
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information on the error. If the error queue is empty
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(i.e. \fIERR_get_error()\fR returns 0), \fBret\fR can be used to find out more
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about the error: If \fBret == 0\fR, an \s-1EOF\s0 was observed that violates
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the protocol. If \fBret == \-1\fR, the underlying \fB\s-1BIO\s0\fR reported an
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I/O error (for socket I/O on Unix systems, consult \fBerrno\fR for details).
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.IP "\s-1SSL_ERROR_SSL\s0" 4
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.IX Item "SSL_ERROR_SSL"
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A failure in the \s-1SSL\s0 library occurred, usually a protocol error. The
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OpenSSL error queue contains more information on the error.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fIssl\fR\|(3), \fIerr\fR\|(3)
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.SH "HISTORY"
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.IX Header "HISTORY"
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\&\fISSL_get_error()\fR was added in SSLeay 0.8.
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