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.IX Title "nbdkit_peer_tls_dn 3"
.TH nbdkit_peer_tls_dn 3 2026-10-17 nbdkit-1.49.4 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
nbdkit_peer_tls_dn,
nbdkit_peer_tls_issuer_dn \- read the client TLS X.509 Distinguished Name
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <nbdkit\-plugin.h>
\&
\& char *nbdkit_peer_tls_dn (void);
\& char *nbdkit_peer_tls_issuer_dn (void);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
If all of these conditions are met:
.IP \(bu 4
the client connects over TLS (see \fBnbdkit\-tls\fR\|(1))
.IP \(bu 4
the TLS connection is using X.509 certificates
.IP \(bu 4
the client presents a client certificate
.IP \(bu 4
the nbdkit \fI\-\-tls\-verify\-peer\fR option is used
.PP
then these APIs can be used to get the Distinguished Name (DN) of the
certificate or the certificate\*(Aqs issuer.  The issuer is the
Certificate Authority (CA) that issued the client certificate.
.PP
The DN is returned as a string of the form \f(CW"CN=xx,O=yy,[...]C=zz"\fR
(see RFC\ 4514 for the exact format).
.PP
If the DN is not available, \f(CW""\fR is returned (this is not an error).
.PP
\&\fBnbdkit\-ip\-filter\fR\|(1) can be used to filter client connections by the
DN.
.SS "EXAMPLE CERTIFICATE AND DISTINGUISHED NAME"
.IX Subsection "EXAMPLE CERTIFICATE AND DISTINGUISHED NAME"
Please see \fBnbdkit\-tls\fR\|(1) for details of how to generate client
certificates.  Following those instructions, if you were to generate a
client certificate from this \fIclient.info\fR input:
.PP
.Vb 8
\& country = US
\& state = New York
\& locality = New York
\& organization = BigCo
\& cn = client.example.com
\& tls_www_client
\& encryption_key
\& signing_key
.Ve
.PP
and sign it with this Certificate Authority \fIca.info\fR:
.PP
.Vb 3
\& cn = BigCo
\& ca
\& cert_signing_key
.Ve
.PP
then the client certificate DN would be:
.PP
.Vb 1
\& CN=client.example.com,O=BigCo,L=New York,ST=New York,C=US
.Ve
.PP
and the issuer DN would be:
.PP
.Vb 1
\& CN=BigCo
.Ve
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
On success both of these functions return a TLS Distinguished Name as
a string, or \f(CW""\fR.  The caller must free this string.
.PP
If there is an error they call \fBnbdkit_error\fR\|(3) and return \f(CW\*(C`NULL\*(C'\fR.
.SH "LANGUAGE BINDINGS"
.IX Header "LANGUAGE BINDINGS"
In \fBnbdkit\-ocaml\-plugin\fR\|(3):
.PP
.Vb 2
\& NBDKit.peer_tls_dn : unit \-> string
\& NBDKit.peer_tls_issuer_dn : unit \-> string
.Ve
.PP
In \fBnbdkit\-python\-plugin\fR\|(3):
.PP
.Vb 3
\& import nbdkit
\& dn = nbdkit.peer_tls_dn()
\& dn = nbdkit.peer_tls_issuer_dn()
.Ve
.SH HISTORY
.IX Header "HISTORY"
\&\f(CW\*(C`nbdkit_peer_tls_dn\*(C'\fR and \f(CW\*(C`nbdkit_peer_tls_issuer_dn\*(C'\fR were added in
nbdkit\ 1.40.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-plugin\fR\|(3),
\&\fBnbdkit\-filter\fR\|(3),
\&\fBnbdkit\-tls\fR\|(1),
\&\fBnbdkit\-ip\-filter\fR\|(1),
\&\fBnbdkit_is_tls\fR\|(3),
\&\fBnbdkit_peer_name\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS \*(Aq\*(AqAS IS\*(Aq\*(Aq AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.