2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
155 lines
5 KiB
Groff
155 lines
5 KiB
Groff
.\" $NetBSD: access.2,v 1.26 2010/05/03 05:53:56 jruoho Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)access.2 8.2 (Berkeley) 4/1/94
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.\"
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.Dd May 3, 2010
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.Dt ACCESS 2
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.Os
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.Sh NAME
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.Nm access
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.Nd check access permissions of a file or pathname
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn access "const char *path" "int mode"
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.Sh DESCRIPTION
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The
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.Fn access
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function checks the accessibility of the
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file named by
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.Fa path
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for the access permissions indicated by
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.Fa mode .
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The value of
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.Fa mode
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is the bitwise inclusive OR of the access permissions to be
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checked
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.Pf ( Dv R_OK
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for read permission,
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.Dv W_OK
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for write permission and
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.Dv X_OK
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for execute/search permission) or the existence test,
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.Dv F_OK .
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All components of the pathname
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.Fa path
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are checked for access permissions (including
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.Dv F_OK ) .
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.Pp
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The real user ID is used in place of the effective user ID
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and the real group access list
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(including the real group ID) are
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used in place of the effective ID for verifying permission.
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.Pp
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If a process has super-user privileges and indicates success for
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.Dv R_OK
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or
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.Dv W_OK ,
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the file may not actually have read or write permission bits set.
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If a process has super-user privileges and indicates success for
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.Dv X_OK ,
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at least one of the user, group, or other execute bits is set.
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(However, the file may still not be executable.
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See
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.Xr execve 2 . )
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.Sh RETURN VALUES
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If
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.Fa path
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cannot be found or if any of the desired access modes would
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not be granted, then a \-1 value is returned; otherwise
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a 0 value is returned.
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.Sh ERRORS
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Access to the file is denied if:
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.Bl -tag -width Er
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.It Bq Er EACCES
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Permission bits of the file mode do not permit the requested
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access, or search permission is denied on a component of the
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path prefix.
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The owner of a file has permission checked with respect to the
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.Dq owner
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read, write, and execute mode bits, members of the file's group
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other than the owner have permission checked with respect to the
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.Dq group
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mode bits, and all others have permissions checked with respect to
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the
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.Dq other
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mode bits.
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.It Bq Er EFAULT
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.Fa path
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points outside the process's allocated address space.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er EROFS
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Write access is requested for a file on a read-only file system.
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.It Bq Er ETXTBSY
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Write access is requested for a pure procedure (shared text)
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file presently being executed.
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.El
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.Sh SEE ALSO
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.Xr chmod 2 ,
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.Xr execve 2 ,
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.Xr stat 2 ,
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.Xr secure_path 3
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.Sh STANDARDS
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The
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.Fn access
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function conforms to
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.St -p1003.1-90 .
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.Sh SECURITY CONSIDERATIONS
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The
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.Fn access
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system call is a potential security hole due to race conditions.
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It should never be used.
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Set-user-ID and set-group-ID applications should restore the
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effective user or group ID, and perform actions directly rather than use
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.Fn access
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to simulate access checks for the real user or group ID.
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.Pp
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The
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.Fn access
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system call may however have some value in providing clues to users as to
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whether certain operations make sense for a particular filesystem object.
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Arguably it also allows a cheaper file existence test than
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.Xr stat 2 .
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