man/keyctl_describe.3

.\"
.\" Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
.\" Written by David Howells (dhowells@redhat.com)
.\"
.\" This program is free software; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License
.\" as published by the Free Software Foundation; either version
.\" 2 of the License, or (at your option) any later version.
.\"
.TH KEYCTL_DESCRIBE 3 "4 May 2006" Linux "Linux Key Management Calls"
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.SH NAME
keyctl_describe \- describe a key
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.SH SYNOPSIS
.nf
.B #include <keyutils.h>
.sp
.BI "long keyctl_describe(key_serial_t " key ", char *" buffer ,
.BI "size_t" buflen ");"
.sp
.BI "long keyctl_describe_alloc(key_serial_t " key ", char **" _buffer ");"
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.SH DESCRIPTION
.BR keyctl_describe ()
describes the attributes of a key as a NUL-terminated string.
.P
The caller must have
.B view
permission on a key to be able to get a description of it.
.P
.I buffer
and
.I buflen
specify the buffer into which the key description will be placed.  If the
buffer is too small, the full size of the description will be returned, and no
copy will take place.
.P
.BR keyctl_describe_alloc ()
is similar to
.BR keyctl_describe ()
except that it allocates a buffer big enough to hold the description and
places the description in it.  If successful, A pointer to the buffer is
placed in
.IR *_buffer .
The caller must free the buffer.
.P
The description will be a string of format:
.IP
.B "\*(lq%s;%d;%d;%08x;%s\*(rq"
.P
where the arguments are: key type name, key UID, key GID, key permissions mask
and key description.
.P
.B NOTE!
The key description will not contain any semicolons, so that should be
separated out by working backwards from the end of the string.  This permits
extra information to be inserted before it by later versions of the kernel
simply by inserting more semicolon-terminated substrings.
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.SH RETURN VALUE
On success
.BR keyctl_describe ()
returns the amount of data placed into the buffer.  If the buffer was too
small, then the size of buffer required will be returned, but no data will be
transferred.  On error, the value
.B -1
will be returned and
.I errno
will have been set to an appropriate error.
.P
On success
.BR keyctl_describe_alloc ()
returns the amount of data in the buffer, less the NUL terminator.  On error, the value
.B -1
will be returned and
.I errno
will have been set to an appropriate error.
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.SH ERRORS
.TP
.B ENOKEY
The key specified is invalid.
.TP
.B EKEYEXPIRED
The key specified has expired.
.TP
.B EKEYREVOKED
The key specified had been revoked.
.TP
.B EACCES
The key exists, but is not
.B viewable
by the calling process.
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.SH LINKING
This is a library function that can be found in
.IR libkeyutils .
When linking,
.B \-lkeyutils
should be specified to the linker.
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.SH SEE ALSO
.ad l
.nh
.BR keyctl (1),
.BR add_key (2),
.BR keyctl (2),
.BR request_key (2),
.BR keyctl (3),
.BR keyrings (7),
.BR keyutils (7)