1.\" Copyright (c) 1996 Doug Rabson 2.\" 3.\" All rights reserved. 4.\" 5.\" This program is free software. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 17.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 20.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26.\" 27.\" $FreeBSD: src/share/man/man9/VOP_ACCESS.9,v 1.7.2.4 2001/12/17 11:30:18 ru Exp $ 28.\" 29.Dd July 24, 1996 30.Dt VOP_ACCESS 9 31.Os 32.Sh NAME 33.Nm VOP_ACCESS 34.Nd "check access permissions of a file or Unix domain socket" 35.Sh SYNOPSIS 36.In sys/param.h 37.In sys/vnode.h 38.Ft int 39.Fn VOP_ACCESS "struct vnode *vp" "int mode" "struct ucred *cred" "struct proc *p" 40.Sh DESCRIPTION 41This entry point checks the access permissions of the file against the 42given credentials. 43.Pp 44Its arguments are: 45.Bl -tag -width mode 46.It Ar vp 47the vnode of the file to check 48.It Ar mode 49the type of access required 50.It Ar cred 51the user credentials to check 52.It Ar p 53the process which is checking 54.El 55.Pp 56The 57.Fa mode 58is a mask which can contain 59.Dv VREAD , 60.Dv VWRITE 61or 62.Dv VEXEC . 63.Sh LOCKS 64The vnode will be locked on entry and should remain locked on return. 65.Sh RETURN VALUES 66If the file is accessible in the specified way, then zero is returned, 67otherwise an appropriate error code is returned. 68.Sh PSEUDOCODE 69.Bd -literal 70int 71vop_access(struct vnode *vp, int mode, struct ucred *cred, struct proc *p) 72{ 73 int error; 74 75 /* 76 * Disallow write attempts on read-only file systems; 77 * unless the file is a socket, fifo, or a block or 78 * character device resident on the file system. 79 */ 80 if (mode & VWRITE) { 81 switch (vp->v_type) { 82 case VDIR: 83 case VLNK: 84 case VREG: 85 if (vp->v_mount->mnt_flag & MNT_RDONLY) 86 return EROFS; 87 88 break; 89 } 90 } 91 92 /* If immutable bit set, nobody gets to write it. */ 93 if ((mode & VWRITE) && vp has immutable bit set) 94 return EPERM; 95 96 /* Otherwise, user id 0 always gets access. */ 97 if (cred->cr_uid == 0) 98 return 0; 99 100 mask = 0; 101 102 /* Otherwise, check the owner. */ 103 if (cred->cr_uid == owner of vp) { 104 if (mode & VEXEC) 105 mask |= S_IXUSR; 106 if (mode & VREAD) 107 mask |= S_IRUSR; 108 if (mode & VWRITE) 109 mask |= S_IWUSR; 110 return (((mode of vp) & mask) == mask ? 0 : EACCES); 111 } 112 113 /* Otherwise, check the groups. */ 114 for (i = 0, gp = cred->cr_groups; i < cred->cr_ngroups; i++, gp++) 115 if (group of vp == *gp) { 116 if (mode & VEXEC) 117 mask |= S_IXGRP; 118 if (mode & VREAD) 119 mask |= S_IRGRP; 120 if (mode & VWRITE) 121 mask |= S_IWGRP; 122 return (((mode of vp) & mask) == mask ? 0 : EACCES); 123 } 124 125 /* Otherwise, check everyone else. */ 126 if (mode & VEXEC) 127 mask |= S_IXOTH; 128 if (mode & VREAD) 129 mask |= S_IROTH; 130 if (mode & VWRITE) 131 mask |= S_IWOTH; 132 return (((mode of vp) & mask) == mask ? 0 : EACCES); 133} 134.Ed 135.Sh ERRORS 136.Bl -tag -width Er 137.It Bq Er EPERM 138An attempt was made to change an immutable file 139.It Bq Er EACCES 140Permission denied 141.El 142.Sh SEE ALSO 143.Xr vnode 9 144.Sh AUTHORS 145This man page was written by 146.An Doug Rabson . 147