.\"=============================================================================
.\" Header
.\"
.\" Copyright (c) 2018-2021 Michael Baeuerle
.\"
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.TH libcanlock 3 2021-11-24 Unix "libcanlock 3.3.0 manual"
.\"
.\"
.\"=============================================================================
.\" NAME section
.\"
.SH NAME
cl_get_key - Create Cancel-Key with libcanlock
.\"
.\"
.\"=============================================================================
.\" SYNOPSIS section
.\"
.SH SYNOPSIS
.nf
.B #include <libcanlock-3/canlock.h>
.sp
.BI "char *cl_get_key(cl_hash_version " hash ,
.BI "                 const unsigned char *" sec ", size_t " sec_len ,
.BI "                 const unsigned char *" msg ", size_t " msg_len );
.fi
.sp
Supported values for
.I hash
(by version 3.0.0 of libcanlock):
.br
CL_SHA1 CL_SHA224 CL_SHA256 CL_SHA384 CL_SHA512
.\"
.\"
.\"=============================================================================
.\" DESCRIPTION section
.\"
.SH DESCRIPTION
The
.BR cl_get_key ()
function creates a <c-key> element according to the algorithm recommended by
RFC 8315 in Section 4. The hash algorithm selected for <scheme> is used for the
HMAC operation too.
.sp
The hash algorithm for <scheme> is selected with
.IR "hash" .
.sp
The local secret is specified with
.IR sec " (" sec_len
must be set to the length of
.IR "sec" ).
.br
The length of the local secret should be at least the length of the hash
that was selected for <scheme> (32 octets for SHA256).
.sp
The Message-ID of the target article (the one that should be cancelled or
superseded) is specified with
.IR msg " (" msg_len
must be set to the length of
.IR "msg" ).
.sp
The Message-ID
.IR "msg"
can be prepended with an optional User-ID. The length of the User-ID must be
added to
.IR "msg_len" .
The User-ID must not contain angle brackets.
.\"
.\"
.\"=============================================================================
.\" RETURN VALUE section
.\"
.SH RETURN VALUE
Upon successful completion a pointer to the result string is returned.
Otherwise,
.B NULL
is returned.
.sp
On success the caller is responsible to call
.BR free ()
for the pointer returned as result.
.\"
.\"
.\"=============================================================================
.\" AUTHORS section
.\"
.SH AUTHORS
Dennis Preiser
.br
(Based in part on the implementation from G. J. Andruk for Version 2)
.sp
The base64 implementation is written by Kungliga Tekniska Hogskolan
(Royal Institute of Technology, Stockholm, Sweden)
.sp
The hash algorithms are implemented with code from RFC 6234
.\"
.\"
.\"=============================================================================
.\" REPORTING BUGS section
.\"
.SH REPORTING BUGS
Report bugs to <mailto:michael.baeuerle@gmx.net>.
.\"
.\"
.\"=============================================================================
.\" STANDARDS section
.\"
.SH STANDARDS
.B libcanlock
tries to comply with the following standards:
.PP
RFC 5537, RFC 6234, RFC 8315
.\"
.\"
.\"=============================================================================
.\" SEE ALSO section
.\"
.SH SEE ALSO
.BR free (3),
.BR cl_clear_secret (3),
.BR cl_get_lock (3),
.BR cl_split (3),
.BR cl_verify (3),
.BR cl_verify_multi (3),
.BR canlock (1)
.\"
.\"
.\" EOF