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/*-
* Copyright (c) 2008-2011 Robert N. M. Watson
* Copyright (c) 2010-2011 Jonathan Anderson
* 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 kernel capability facility.
*
* Currently, this file implements only capability mode; capabilities
* (rights-refined file descriptors) will follow.
*
*/
#include "opt_capsicum.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/capability.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sysproto.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/ucred.h>
#include <security/audit/audit.h>
#include <vm/uma.h>
#include <vm/vm.h>
#ifdef CAPABILITY_MODE
FEATURE(security_capabilities, "Capsicum Capability Mode");
/*
* System call to enter capability mode for the process.
*/
int
cap_enter(struct thread *td, struct cap_enter_args *uap)
{
struct ucred *newcred, *oldcred;
struct proc *p;
if (IN_CAPABILITY_MODE(td))
return (0);
newcred = crget();
p = td->td_proc;
PROC_LOCK(p);
oldcred = p->p_ucred;
crcopy(newcred, oldcred);
newcred->cr_flags |= CRED_FLAG_CAPMODE;
p->p_ucred = newcred;
PROC_UNLOCK(p);
crfree(oldcred);
return (0);
}
/*
* System call to query whether the process is in capability mode.
*/
int
cap_getmode(struct thread *td, struct cap_getmode_args *uap)
{
u_int i;
i = (IN_CAPABILITY_MODE(td)) ? 1 : 0;
return (copyout(&i, uap->modep, sizeof(i)));
}
#else /* !CAPABILITY_MODE */
int
cap_enter(struct thread *td, struct cap_enter_args *uap)
{
return (ENOSYS);
}
int
cap_getmode(struct thread *td, struct cap_getmode_args *uap)
{
return (ENOSYS);
}
#endif /* CAPABILITY_MODE */
#ifdef CAPABILITIES
/*
* struct capability describes a capability, and is hung off of its struct
* file f_data field. cap_file and cap_rightss are static once hooked up, as
* neither the object it references nor the rights it encapsulates are
* permitted to change. cap_filelist may change when other capabilites are
* added or removed from the same file, and is currently protected by the
* pool mutex for the object file descriptor.
*/
struct capability {
struct file *cap_object; /* Underlying object's file. */
struct file *cap_file; /* Back-pointer to cap's file. */
cap_rights_t cap_rights; /* Mask of rights on object. */
LIST_ENTRY(capability) cap_filelist; /* Object's cap list. */
};
/*
* Test whether a capability grants the requested rights.
*/
static int
cap_check(struct capability *c, cap_rights_t rights)
{
if ((c->cap_rights | rights) != c->cap_rights)
return (ENOTCAPABLE);
return (0);
}
/*
* Given a file descriptor, test it against a capability rights mask and then
* return the file descriptor on which to actually perform the requested
* operation. As long as the reference to fp_cap remains valid, the returned
* pointer in *fp will remain valid, so no extra reference management is
* required, and the caller should fdrop() fp_cap as normal when done with
* both.
*/
int
cap_funwrap(struct file *fp_cap, cap_rights_t rights, struct file **fpp)
{
struct capability *c;
int error;
if (fp_cap->f_type != DTYPE_CAPABILITY) {
*fpp = fp_cap;
return (0);
}
c = fp_cap->f_data;
error = cap_check(c, rights);
if (error)
return (error);
*fpp = c->cap_object;
return (0);
}
/*
* Slightly different routine for memory mapping file descriptors: unwrap the
* capability and check CAP_MMAP, but also return a bitmask representing the
* maximum mapping rights the capability allows on the object.
*/
int
cap_funwrap_mmap(struct file *fp_cap, cap_rights_t rights, u_char *maxprotp,
struct file **fpp)
{
struct capability *c;
u_char maxprot;
int error;
if (fp_cap->f_type != DTYPE_CAPABILITY) {
*fpp = fp_cap;
*maxprotp = VM_PROT_ALL;
return (0);
}
c = fp_cap->f_data;
error = cap_check(c, rights | CAP_MMAP);
if (error)
return (error);
*fpp = c->cap_object;
maxprot = 0;
if (c->cap_rights & CAP_READ)
maxprot |= VM_PROT_READ;
if (c->cap_rights & CAP_WRITE)
maxprot |= VM_PROT_WRITE;
if (c->cap_rights & CAP_MAPEXEC)
maxprot |= VM_PROT_EXECUTE;
*maxprotp = maxprot;
return (0);
}
#else /* !CAPABILITIES */
/*
* Stub Capability functions for when options CAPABILITIES isn't compiled
* into the kernel.
*/
int
cap_funwrap(struct file *fp_cap, cap_rights_t rights, struct file **fpp)
{
KASSERT(fp_cap->f_type != DTYPE_CAPABILITY,
("cap_funwrap: saw capability"));
*fpp = fp_cap;
return (0);
}
int
cap_funwrap_mmap(struct file *fp_cap, cap_rights_t rights, u_char *maxprotp,
struct file **fpp)
{
KASSERT(fp_cap->f_type != DTYPE_CAPABILITY,
("cap_funwrap_mmap: saw capability"));
*fpp = fp_cap;
*maxprotp = VM_PROT_ALL;
return (0);
}
#endif /* CAPABILITIES */
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