1.\" -*- nroff -*- 2.\" -*- nroff -*- 3.\" 4.\" Copyright (c) 1996 Doug Rabson 5.\" 6.\" All rights reserved. 7.\" 8.\" This program is free software. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 20.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 23.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29.\" 30.\" $FreeBSD$ 31.\" 32.Dd July 24, 1996 33.Os 34.Dt VOP_ACCESS 9 35.Sh NAME 36.Nm VOP_ACCESS 37.Nd "check access permissions of a file or Unix domain socket" 38.Sh SYNOPSIS 39.In sys/param.h 40.In sys/vnode.h 41.Ft int 42.Fn VOP_ACCESS "struct vnode *vp" "int mode" "struct ucred *cred" "struct proc *p" 43.Sh DESCRIPTION 44This entry point checks the access permissions of the file against the 45given credentials. 46.Pp 47Its arguments are: 48.Bl -tag -width mode 49.It Ar vp 50the vnode of the file to check 51.It Ar mode 52the type of access required 53.It Ar cred 54the user credentials to check 55.It Ar p 56the process which is checking 57.El 58.Pp 59The 60.Fa mode 61is a mask which can contain 62.Dv VREAD , 63.Dv VWRITE 64or 65.Dv VEXEC . 66.Sh LOCKS 67The vnode will be locked on entry and should remain locked on return. 68.Sh RETURN VALUES 69If the file is accessible in the specified way, then zero is returned, 70otherwise an appropriate error code is returned. 71.Sh PSEUDOCODE 72.Bd -literal 73int 74vop_access(struct vnode *vp, int mode, struct ucred *cred, struct proc *p) 75{ 76 int error; 77 78 /* 79 * Disallow write attempts on read-only file systems; 80 * unless the file is a socket, fifo, or a block or 81 * character device resident on the file system. 82 */ 83 if (mode & VWRITE) { 84 switch (vp->v_type) { 85 case VDIR: 86 case VLNK: 87 case VREG: 88 if (vp->v_mount->mnt_flag & MNT_RDONLY) 89 return EROFS; 90 91 break; 92 } 93 } 94 95 /* If immutable bit set, nobody gets to write it. */ 96 if ((mode & VWRITE) && vp has immutable bit set) 97 return EPERM; 98 99 /* Otherwise, user id 0 always gets access. */ 100 if (cred->cr_uid == 0) 101 return 0; 102 103 mask = 0; 104 105 /* Otherwise, check the owner. */ 106 if (cred->cr_uid == owner of vp) { 107 if (mode & VEXEC) 108 mask |= S_IXUSR; 109 if (mode & VREAD) 110 mask |= S_IRUSR; 111 if (mode & VWRITE) 112 mask |= S_IWUSR; 113 return (((mode of vp) & mask) == mask ? 0 : EACCES); 114 } 115 116 /* Otherwise, check the groups. */ 117 for (i = 0, gp = cred->cr_groups; i < cred->cr_ngroups; i++, gp++) 118 if (group of vp == *gp) { 119 if (mode & VEXEC) 120 mask |= S_IXGRP; 121 if (mode & VREAD) 122 mask |= S_IRGRP; 123 if (mode & VWRITE) 124 mask |= S_IWGRP; 125 return (((mode of vp) & mask) == mask ? 0 : EACCES); 126 } 127 128 /* Otherwise, check everyone else. */ 129 if (mode & VEXEC) 130 mask |= S_IXOTH; 131 if (mode & VREAD) 132 mask |= S_IROTH; 133 if (mode & VWRITE) 134 mask |= S_IWOTH; 135 return (((mode of vp) & mask) == mask ? 0 : EACCES); 136} 137.Ed 138.Sh ERRORS 139.Bl -tag -width Er 140.It Bq Er EPERM 141An attempt was made to change an immutable file 142.It Bq Er EACCES 143Permission denied 144.El 145.Sh SEE ALSO 146.Xr vnode 9 147.Sh AUTHORS 148This man page was written by 149.An Doug Rabson . 150