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.\" $Id: VOP_ACCESS.9,v 1.2 1997/03/04 06:20:41 mpp Exp $ 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.Fd #include <sys/vnode.h> 40.Ft int 41.Fn VOP_ACCESS "struct vnode *vp" "int mode" "struct ucred *cred" "struct proc *p" 42.Sh DESCRIPTION 43This entry point checks the access permissions of the file against the 44given credentials. 45.Pp 46Its arguments are: 47.Bl -tag -width mode 48.It Ar vp 49the vnode of the file to check 50.It Ar mode 51the type of access required 52.It Ar cred 53the user credentials to check 54.It Ar p 55the process which is checking 56.El 57.Pp 58The 59.Fa mode 60is a mask which can contain 61.Dv VREAD , 62.Dv VWRITE or 63.Dv VEXEC. 64.Sh LOCKS 65The vnode should be locked on entry. 66.Sh RETURN VALUES 67If the file is accessible in the specified way, then zero is returned, 68otherwise an appropriate error code is returned. 69.Sh PSEUDOCODE 70.Bd -literal 71int 72vop_access(struct vnode *vp, int mode, struct ucred *cred, struct proc *p) 73{ 74 int error; 75 76 /* 77 * Disallow write attempts on read-only file systems; 78 * unless the file is a socket, fifo, or a block or 79 * character device resident on the file system. 80 */ 81 if (mode & VWRITE) { 82 switch (vp->v_type) { 83 case VDIR: 84 case VLNK: 85 case VREG: 86 if (vp->v_mount->mnt_flag & MNT_RDONLY) 87 return EROFS; 88 89 break; 90 } 91 } 92 93 /* If immutable bit set, nobody gets to write it. */ 94 if ((mode & VWRITE) && vp has immutable bit set) 95 return EPERM; 96 97 /* Otherwise, user id 0 always gets access. */ 98 if (cred->cr_uid == 0) 99 return 0; 100 101 mask = 0; 102 103 /* Otherwise, check the owner. */ 104 if (cred->cr_uid == owner of vp) { 105 if (mode & VEXEC) 106 mask |= S_IXUSR; 107 if (mode & VREAD) 108 mask |= S_IRUSR; 109 if (mode & VWRITE) 110 mask |= S_IWUSR; 111 return (((mode of vp) & mask) == mask ? 0 : EACCES); 112 } 113 114 /* Otherwise, check the groups. */ 115 for (i = 0, gp = cred->cr_groups; i < cred->cr_ngroups; i++, gp++) 116 if (group of vp == *gp) { 117 if (mode & VEXEC) 118 mask |= S_IXGRP; 119 if (mode & VREAD) 120 mask |= S_IRGRP; 121 if (mode & VWRITE) 122 mask |= S_IWGRP; 123 return (((mode of vp) & mask) == mask ? 0 : EACCES); 124 } 125 126 /* Otherwise, check everyone else. */ 127 if (mode & VEXEC) 128 mask |= S_IXOTH; 129 if (mode & VREAD) 130 mask |= S_IROTH; 131 if (mode & VWRITE) 132 mask |= S_IWOTH; 133 return (((mode of vp) & mask) == mask ? 0 : EACCES); 134} 135.Ed 136.Sh ERRORS 137.Bl -tag -width Er 138.It Bq Er EPERM 139An attempt was made to change an immutable file 140.It Bq Er EACCES 141Permission denied 142.El 143.Sh SEE ALSO 144.Xr vnode 9 145.Sh AUTHORS 146This man page was written by Doug Rabson. 147