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Make cap_new(2) and cap_getmode(2) symbols from libc public so applications

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can link against them.  Add man pages for the new system calls, with one
errant forward reference to changes not yet present in FreeBSD, but soon
will be.

Reviewed by:	anderson
Obtained from:	Capsicum Project
Sponsored by:	Google, Inc.
Discussed with:	benl, kris, pjd
MFC after:	3 months
This commit is contained in:
Robert Watson 2011-03-03 11:31:08 +00:00
parent 31cd487f40
commit d2deca0335
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=219224
3 changed files with 105 additions and 1 deletions
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3
lib/libc/sys/Makefile.inc
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@ -74,7 +74,7 @@ ${SPSEUDO}:
MAN+= abort2.2 accept.2 access.2 acct.2 adjtime.2 \
aio_cancel.2 aio_error.2 aio_read.2 aio_return.2 \
aio_suspend.2 aio_waitcomplete.2 aio_write.2 \
bind.2 brk.2 chdir.2 chflags.2 \
bind.2 brk.2 cap_enter.2 chdir.2 chflags.2 \
chmod.2 chown.2 chroot.2 clock_gettime.2 close.2 closefrom.2 \
connect.2 cpuset.2 cpuset_getaffinity.2 dup.2 execve.2 _exit.2 \
extattr_get_file.2 fcntl.2 fhopen.2 flock.2 fork.2 fsync.2 \
@ -115,6 +115,7 @@ MAN+= sctp_generic_recvmsg.2 sctp_generic_sendmsg.2 sctp_peeloff.2 \
MLINKS+=access.2 eaccess.2 access.2 faccessat.2
MLINKS+=brk.2 sbrk.2
MLINKS+=cap_enter.2 cap_getmode.2
MLINKS+=chdir.2 fchdir.2
MLINKS+=chflags.2 fchflags.2 chflags.2 lchflags.2
MLINKS+=chmod.2 fchmod.2 chmod.2 fchmodat.2 chmod.2 lchmod.2

2
lib/libc/sys/Symbol.map
View File

@ -330,6 +330,8 @@ FBSD_1.0 {
FBSD_1.1 {
__semctl;
cap_enter;
cap_getmode;
closefrom;
cpuset;
cpuset_getid;

101
lib/libc/sys/cap_enter.2 Normal file
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@ -0,0 +1,101 @@
.\"
.\" Copyright (c) 2008-2009 Robert N. M. Watson
.\" All rights reserved.
.\"
.\" This software was developed at the University of Cambridge Computer
.\" Laboratory with support from a grant from Google, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd June 11, 2009
.Dt CAP_ENTER 2
.Os
.Sh NAME
.Nm cap_enter ,
.Nm cap_getmode
.Nd Capability mode system calls
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/capability.h
.Ft int
.Fn cap_enter "void"
.Ft int
.Fn cap_getmode "u_int *modep"
.Sh DESCRIPTION
.Fn cap_enter
places the current process into capability mode, a mode of execution in which
processes may only issue system calls operating on file descriptors or
reading limited global system state.
Access to global name spaces, such as file system or IPC name spaces, is
prevented.
If the process is already in a capability mode sandbox, the system call is a
no-op.
Future process descendants create with
.Xr fork 2
or
.Xr pdfork 2
will be placed in capability mode from inception.
.Pp
When combined with capabilities created with
.Xr cap_new 2 ,
.Fn cap_enter
may be used to create kernel-enforced sandboxes in which
appropriately-crafted applications or application components may be run.
.Pp
.Fn cap_getmode
returns a flag indicating whether or not the process is in a capability mode
sandbox.
.Sh CAVEAT
Creating effecive process sandboxes is a tricky process that involves
identifying the least possible rights required by the process and then
passing those rights into the process in a safe manner.
See the CAVEAT
section of
.Xr cap_new 2
for why this is particularly tricky with UNIX file descriptors as the
canonical representation of a right.
Consumers of
.Fn cap_enter
should also be aware of other inherited rights, such as access to VM
resources, memory contents, and other process properties that should be
considered.
It is advisable to use
.Xr fexecve 2
to create a runtime environment inside the sandbox that has as few implicitly
acquired rights as possible.
.Sh RETURN VALUES
.Rv -std cap_enter cap_getmode
.Sh SEE ALSO
.Xr cap_new 2 ,
.Xr fexecve 2
.Sh HISTORY
Support for capabilities and capabilities mode was developed as part of the
.Tn TrustedBSD
Project.
.Sh AUTHORS
These functions and the capability facility were created by
.An "Robert N. M. Watson"
at the University of Cambridge Computer Laboratory with support from a grant
from Google, Inc.