150 lines
4.0 KiB
Groff
150 lines
4.0 KiB
Groff
.\" -*- nroff -*-
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.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1996 Doug Rabson
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.\"
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.\" All rights reserved.
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.\"
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.\" This program is free software.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 24, 1996
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.Os
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.Dt VOP_ACCESS 9
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.Sh NAME
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.Nm VOP_ACCESS
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.Nd "check access permissions of a file or Unix domain socket"
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.Sh SYNOPSIS
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.Fd #include <sys/param.h>
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.Fd #include <sys/vnode.h>
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.Ft int
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.Fn VOP_ACCESS "struct vnode *vp" "int mode" "struct ucred *cred" "struct proc *p"
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.Sh DESCRIPTION
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This entry point checks the access permissions of the file against the
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given credentials.
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.Pp
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Its arguments are:
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.Bl -tag -width mode
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.It Ar vp
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the vnode of the file to check
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.It Ar mode
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the type of access required
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.It Ar cred
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the user credentials to check
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.It Ar p
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the process which is checking
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.El
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.Pp
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The
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.Fa mode
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is a mask which can contain
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.Dv VREAD ,
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.Dv VWRITE
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or
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.Dv VEXEC .
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.Sh LOCKS
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The vnode will be locked on entry and should remain locked on return.
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.Sh RETURN VALUES
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If the file is accessible in the specified way, then zero is returned,
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otherwise an appropriate error code is returned.
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.Sh PSEUDOCODE
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.Bd -literal
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int
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vop_access(struct vnode *vp, int mode, struct ucred *cred, struct proc *p)
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{
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int error;
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/*
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* Disallow write attempts on read-only file systems;
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* unless the file is a socket, fifo, or a block or
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* character device resident on the file system.
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*/
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if (mode & VWRITE) {
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switch (vp->v_type) {
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case VDIR:
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case VLNK:
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case VREG:
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if (vp->v_mount->mnt_flag & MNT_RDONLY)
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return EROFS;
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break;
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}
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}
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/* If immutable bit set, nobody gets to write it. */
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if ((mode & VWRITE) && vp has immutable bit set)
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return EPERM;
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/* Otherwise, user id 0 always gets access. */
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if (cred->cr_uid == 0)
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return 0;
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mask = 0;
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/* Otherwise, check the owner. */
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if (cred->cr_uid == owner of vp) {
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if (mode & VEXEC)
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mask |= S_IXUSR;
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if (mode & VREAD)
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mask |= S_IRUSR;
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if (mode & VWRITE)
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mask |= S_IWUSR;
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return (((mode of vp) & mask) == mask ? 0 : EACCES);
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}
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/* Otherwise, check the groups. */
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for (i = 0, gp = cred->cr_groups; i < cred->cr_ngroups; i++, gp++)
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if (group of vp == *gp) {
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if (mode & VEXEC)
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mask |= S_IXGRP;
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if (mode & VREAD)
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mask |= S_IRGRP;
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if (mode & VWRITE)
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mask |= S_IWGRP;
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return (((mode of vp) & mask) == mask ? 0 : EACCES);
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}
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/* Otherwise, check everyone else. */
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if (mode & VEXEC)
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mask |= S_IXOTH;
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if (mode & VREAD)
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mask |= S_IROTH;
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if (mode & VWRITE)
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mask |= S_IWOTH;
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return (((mode of vp) & mask) == mask ? 0 : EACCES);
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}
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.Ed
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EPERM
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An attempt was made to change an immutable file
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.It Bq Er EACCES
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Permission denied
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.El
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.Sh SEE ALSO
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.Xr vnode 9
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.Sh AUTHORS
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This man page was written by
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.An Doug Rabson .
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