/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2008-2011 Robert N. M. Watson
* Copyright (c) 2010-2011 Jonathan Anderson
* Copyright (c) 2012 FreeBSD Foundation
* All rights reserved.
*
* This software was developed at the University of Cambridge Computer
* Laboratory with support from a grant from Google, Inc.
*
* Portions of this software were developed by Pawel Jakub Dawidek under
* sponsorship from the FreeBSD Foundation.
*
* 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.
*
* Two kernel features are implemented here: capability mode, a sandboxed mode
* of execution for processes, and capabilities, a refinement on file
* descriptors that allows fine-grained control over operations on the file
* descriptor. Collectively, these allow processes to run in the style of a
* historic "capability system" in which they can use only resources
* explicitly delegated to them. This model is enforced by restricting access
* to global namespaces in capability mode.
*
* Capabilities wrap other file descriptor types, binding them to a constant
* rights mask set when the capability is created. New capabilities may be
* derived from existing capabilities, but only if they have the same or a
* strict subset of the rights on the original capability.
*
* System calls permitted in capability mode are defined in capabilities.conf;
* calls must be carefully audited for safety to ensure that they don't allow
* escape from a sandbox. Some calls permit only a subset of operations in
* capability mode -- for example, shm_open(2) is limited to creating
* anonymous, rather than named, POSIX shared memory objects.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_capsicum.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/syscallsubr.h>
#include <sys/sysproto.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/ucred.h>
#include <sys/uio.h>
#include <sys/ktrace.h>
#include <security/audit/audit.h>
#include <vm/uma.h>
#include <vm/vm.h>
bool __read_frequently trap_enotcap;
SYSCTL_BOOL(_kern, OID_AUTO, trap_enotcap, CTLFLAG_RWTUN, &trap_enotcap, 0,
"Deliver SIGTRAP on ENOTCAPABLE");
#ifdef CAPABILITY_MODE
#define IOCTLS_MAX_COUNT 256 /* XXX: Is 256 sane? */
FEATURE(security_capability_mode, "Capsicum Capability Mode");
/*
* System call to enter capability mode for the process.
*/
int
sys_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 = crcopysafe(p, newcred);
newcred->cr_flags |= CRED_FLAG_CAPMODE;
proc_set_cred(p, newcred);
PROC_UNLOCK(p);
crfree(oldcred);
return (0);
}
/*
* System call to query whether the process is in capability mode.
*/
int
sys_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
sys_cap_enter(struct thread *td, struct cap_enter_args *uap)
{
return (ENOSYS);
}
int
sys_cap_getmode(struct thread *td, struct cap_getmode_args *uap)
{
return (ENOSYS);
}
#endif /* CAPABILITY_MODE */
#ifdef CAPABILITIES
FEATURE(security_capabilities, "Capsicum Capabilities");
MALLOC_DECLARE(M_FILECAPS);
static inline int
_cap_check(const cap_rights_t *havep, const cap_rights_t *needp,
enum ktr_cap_fail_type type)
{
if (!cap_rights_contains(havep, needp)) {
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_CAPFAIL))
ktrcapfail(type, needp, havep);
#endif
return (ENOTCAPABLE);
}
return (0);
}
/*
* Test whether a capability grants the requested rights.
*/
int
cap_check(const cap_rights_t *havep, const cap_rights_t *needp)
{
return (_cap_check(havep, needp, CAPFAIL_NOTCAPABLE));
}
int
cap_check_failed_notcapable(const cap_rights_t *havep, const cap_rights_t *needp)
{
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_CAPFAIL))
ktrcapfail(CAPFAIL_NOTCAPABLE, needp, havep);
#endif
return (ENOTCAPABLE);
}
/*
* Convert capability rights into VM access flags.
*/
vm_prot_t
cap_rights_to_vmprot(const cap_rights_t *havep)
{
vm_prot_t maxprot;
maxprot = VM_PROT_NONE;
if (cap_rights_is_set(havep, CAP_MMAP_R))
maxprot |= VM_PROT_READ;
if (cap_rights_is_set(havep, CAP_MMAP_W))
maxprot |= VM_PROT_WRITE;
if (cap_rights_is_set(havep, CAP_MMAP_X))
maxprot |= VM_PROT_EXECUTE;
return (maxprot);
}
/*
* Extract rights from a capability for monitoring purposes -- not for use in
* any other way, as we want to keep all capability permission evaluation in
* this one file.
*/
const cap_rights_t *
cap_rights_fde(const struct filedescent *fdep)
{
return (cap_rights_fde_inline(fdep));
}
const cap_rights_t *
cap_rights(struct filedesc *fdp, int fd)
{
return (cap_rights_fde(&fdp->fd_ofiles[fd]));
}
int
kern_cap_rights_limit(struct thread *td, int fd, cap_rights_t *rights)
{
struct filedesc *fdp;
struct filedescent *fdep;
u_long *ioctls;
int error;
fdp = td->td_proc->p_fd;
FILEDESC_XLOCK(fdp);
fdep = fdeget_locked(fdp, fd);
if (fdep == NULL) {
FILEDESC_XUNLOCK(fdp);
return (EBADF);
}
ioctls = NULL;
error = _cap_check(cap_rights(fdp, fd), rights, CAPFAIL_INCREASE);
if (error == 0) {
seqc_write_begin(&fdep->fde_seqc);
fdep->fde_rights = *rights;
if (!cap_rights_is_set(rights, CAP_IOCTL)) {
ioctls = fdep->fde_ioctls;
fdep->fde_ioctls = NULL;
fdep->fde_nioctls = 0;
}
if (!cap_rights_is_set(rights, CAP_FCNTL))
fdep->fde_fcntls = 0;
seqc_write_end(&fdep->fde_seqc);
}
FILEDESC_XUNLOCK(fdp);
free(ioctls, M_FILECAPS);
return (error);
}
/*
* System call to limit rights of the given capability.
*/
int
sys_cap_rights_limit(struct thread *td, struct cap_rights_limit_args *uap)
{
cap_rights_t rights;
int error, version;
cap_rights_init_zero(&rights);
error = copyin(uap->rightsp, &rights, sizeof(rights.cr_rights[0]));
if (error != 0)
return (error);
version = CAPVER(&rights);
if (version != CAP_RIGHTS_VERSION_00)
return (EINVAL);
error = copyin(uap->rightsp, &rights,
sizeof(rights.cr_rights[0]) * CAPARSIZE(&rights));
if (error != 0)
return (error);
/* Check for race. */
if (CAPVER(&rights) != version)
return (EINVAL);
if (!cap_rights_is_valid(&rights))
return (EINVAL);
if (version != CAP_RIGHTS_VERSION) {
rights.cr_rights[0] &= ~(0x3ULL << 62);
rights.cr_rights[0] |= ((uint64_t)CAP_RIGHTS_VERSION << 62);
}
#ifdef KTRACE
if (KTRPOINT(td, KTR_STRUCT))
ktrcaprights(&rights);
#endif
AUDIT_ARG_FD(uap->fd);
AUDIT_ARG_RIGHTS(&rights);
return (kern_cap_rights_limit(td, uap->fd, &rights));
}
/*
* System call to query the rights mask associated with a capability.
*/
int
sys___cap_rights_get(struct thread *td, struct __cap_rights_get_args *uap)
{
struct filedesc *fdp;
cap_rights_t rights;
int error, fd, i, n;
if (uap->version != CAP_RIGHTS_VERSION_00)
return (EINVAL);
fd = uap->fd;
AUDIT_ARG_FD(fd);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
if (fget_locked(fdp, fd) == NULL) {
FILEDESC_SUNLOCK(fdp);
return (EBADF);
}
rights = *cap_rights(fdp, fd);
FILEDESC_SUNLOCK(fdp);
n = uap->version + 2;
if (uap->version != CAPVER(&rights)) {
/*
* For older versions we need to check if the descriptor
* doesn't contain rights not understood by the caller.
* If it does, we have to return an error.
*/
for (i = n; i < CAPARSIZE(&rights); i++) {
if ((rights.cr_rights[i] & ~(0x7FULL << 57)) != 0)
return (EINVAL);
}
}
error = copyout(&rights, uap->rightsp, sizeof(rights.cr_rights[0]) * n);
#ifdef KTRACE
if (error == 0 && KTRPOINT(td, KTR_STRUCT))
ktrcaprights(&rights);
#endif
return (error);
}
/*
* Test whether a capability grants the given ioctl command.
* If descriptor doesn't have CAP_IOCTL, then ioctls list is empty and
* ENOTCAPABLE will be returned.
*/
int
cap_ioctl_check(struct filedesc *fdp, int fd, u_long cmd)
{
struct filedescent *fdep;
u_long *cmds;
ssize_t ncmds;
long i;
KASSERT(fd >= 0 && fd < fdp->fd_nfiles,
("%s: invalid fd=%d", __func__, fd));
fdep = fdeget_locked(fdp, fd);
KASSERT(fdep != NULL,
("%s: invalid fd=%d", __func__, fd));
ncmds = fdep->fde_nioctls;
if (ncmds == -1)
return (0);
cmds = fdep->fde_ioctls;
for (i = 0; i < ncmds; i++) {
if (cmds[i] == cmd)
return (0);
}
return (ENOTCAPABLE);
}
/*
* Check if the current ioctls list can be replaced by the new one.
*/
static int
cap_ioctl_limit_check(struct filedescent *fdep, const u_long *cmds,
size_t ncmds)
{
u_long *ocmds;
ssize_t oncmds;
u_long i;
long j;
oncmds = fdep->fde_nioctls;
if (oncmds == -1)
return (0);
if (oncmds < (ssize_t)ncmds)
return (ENOTCAPABLE);
ocmds = fdep->fde_ioctls;
for (i = 0; i < ncmds; i++) {
for (j = 0; j < oncmds; j++) {
if (cmds[i] == ocmds[j])
break;
}
if (j == oncmds)
return (ENOTCAPABLE);
}
return (0);
}
int
kern_cap_ioctls_limit(struct thread *td, int fd, u_long *cmds, size_t ncmds)
{
struct filedesc *fdp;
struct filedescent *fdep;
u_long *ocmds;
int error;
AUDIT_ARG_FD(fd);
if (ncmds > IOCTLS_MAX_COUNT) {
error = EINVAL;
goto out_free;
}
fdp = td->td_proc->p_fd;
FILEDESC_XLOCK(fdp);
fdep = fdeget_locked(fdp, fd);
if (fdep == NULL) {
error = EBADF;
goto out;
}
error = cap_ioctl_limit_check(fdep, cmds, ncmds);
if (error != 0)
goto out;
ocmds = fdep->fde_ioctls;
seqc_write_begin(&fdep->fde_seqc);
fdep->fde_ioctls = cmds;
fdep->fde_nioctls = ncmds;
seqc_write_end(&fdep->fde_seqc);
cmds = ocmds;
error = 0;
out:
FILEDESC_XUNLOCK(fdp);
out_free:
free(cmds, M_FILECAPS);
return (error);
}
int
sys_cap_ioctls_limit(struct thread *td, struct cap_ioctls_limit_args *uap)
{
u_long *cmds;
size_t ncmds;
int error;
ncmds = uap->ncmds;
if (ncmds > IOCTLS_MAX_COUNT)
return (EINVAL);
if (ncmds == 0) {
cmds = NULL;
} else {
cmds = malloc(sizeof(cmds[0]) * ncmds, M_FILECAPS, M_WAITOK);
error = copyin(uap->cmds, cmds, sizeof(cmds[0]) * ncmds);
if (error != 0) {
free(cmds, M_FILECAPS);
return (error);
}
}
return (kern_cap_ioctls_limit(td, uap->fd, cmds, ncmds));
}
int
sys_cap_ioctls_get(struct thread *td, struct cap_ioctls_get_args *uap)
{
struct filedesc *fdp;
struct filedescent *fdep;
u_long *cmdsp, *dstcmds;
size_t maxcmds, ncmds;
int16_t count;
int error, fd;
fd = uap->fd;
dstcmds = uap->cmds;
maxcmds = uap->maxcmds;
AUDIT_ARG_FD(fd);
fdp = td->td_proc->p_fd;
cmdsp = NULL;
if (dstcmds != NULL) {
cmdsp = malloc(sizeof(cmdsp[0]) * IOCTLS_MAX_COUNT, M_FILECAPS,
M_WAITOK | M_ZERO);
}
FILEDESC_SLOCK(fdp);
fdep = fdeget_locked(fdp, fd);
if (fdep == NULL) {
error = EBADF;
FILEDESC_SUNLOCK(fdp);
goto out;
}
count = fdep->fde_nioctls;
if (count != -1 && cmdsp != NULL) {
ncmds = MIN(count, maxcmds);
memcpy(cmdsp, fdep->fde_ioctls, sizeof(cmdsp[0]) * ncmds);
}
FILEDESC_SUNLOCK(fdp);
/*
* If all ioctls are allowed (fde_nioctls == -1 && fde_ioctls == NULL)
* the only sane thing we can do is to not populate the given array and
* return CAP_IOCTLS_ALL.
*/
if (count != -1) {
if (cmdsp != NULL) {
error = copyout(cmdsp, dstcmds,
sizeof(cmdsp[0]) * ncmds);
if (error != 0)
goto out;
}
td->td_retval[0] = count;
} else {
td->td_retval[0] = CAP_IOCTLS_ALL;
}
error = 0;
out:
free(cmdsp, M_FILECAPS);
return (error);
}
/*
* Test whether a capability grants the given fcntl command.
*/
int
cap_fcntl_check_fde(struct filedescent *fdep, int cmd)
{
uint32_t fcntlcap;
fcntlcap = (1 << cmd);
KASSERT((CAP_FCNTL_ALL & fcntlcap) != 0,
("Unsupported fcntl=%d.", cmd));
if ((fdep->fde_fcntls & fcntlcap) != 0)
return (0);
return (ENOTCAPABLE);
}
int
cap_fcntl_check(struct filedesc *fdp, int fd, int cmd)
{
KASSERT(fd >= 0 && fd < fdp->fd_nfiles,
("%s: invalid fd=%d", __func__, fd));
return (cap_fcntl_check_fde(&fdp->fd_ofiles[fd], cmd));
}
int
sys_cap_fcntls_limit(struct thread *td, struct cap_fcntls_limit_args *uap)
{
struct filedesc *fdp;
struct filedescent *fdep;
uint32_t fcntlrights;
int fd;
fd = uap->fd;
fcntlrights = uap->fcntlrights;
AUDIT_ARG_FD(fd);
AUDIT_ARG_FCNTL_RIGHTS(fcntlrights);
if ((fcntlrights & ~CAP_FCNTL_ALL) != 0)
return (EINVAL);
fdp = td->td_proc->p_fd;
FILEDESC_XLOCK(fdp);
fdep = fdeget_locked(fdp, fd);
if (fdep == NULL) {
FILEDESC_XUNLOCK(fdp);
return (EBADF);
}
if ((fcntlrights & ~fdep->fde_fcntls) != 0) {
FILEDESC_XUNLOCK(fdp);
return (ENOTCAPABLE);
}
seqc_write_begin(&fdep->fde_seqc);
fdep->fde_fcntls = fcntlrights;
seqc_write_end(&fdep->fde_seqc);
FILEDESC_XUNLOCK(fdp);
return (0);
}
int
sys_cap_fcntls_get(struct thread *td, struct cap_fcntls_get_args *uap)
{
struct filedesc *fdp;
struct filedescent *fdep;
uint32_t rights;
int fd;
fd = uap->fd;
AUDIT_ARG_FD(fd);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
fdep = fdeget_locked(fdp, fd);
if (fdep == NULL) {
FILEDESC_SUNLOCK(fdp);
return (EBADF);
}
rights = fdep->fde_fcntls;
FILEDESC_SUNLOCK(fdp);
return (copyout(&rights, uap->fcntlrightsp, sizeof(rights)));
}
#else /* !CAPABILITIES */
/*
* Stub Capability functions for when options CAPABILITIES isn't compiled
* into the kernel.
*/
int
sys_cap_rights_limit(struct thread *td, struct cap_rights_limit_args *uap)
{
return (ENOSYS);
}
int
sys___cap_rights_get(struct thread *td, struct __cap_rights_get_args *uap)
{
return (ENOSYS);
}
int
sys_cap_ioctls_limit(struct thread *td, struct cap_ioctls_limit_args *uap)
{
return (ENOSYS);
}
int
sys_cap_ioctls_get(struct thread *td, struct cap_ioctls_get_args *uap)
{
return (ENOSYS);
}
int
sys_cap_fcntls_limit(struct thread *td, struct cap_fcntls_limit_args *uap)
{
return (ENOSYS);
}
int
sys_cap_fcntls_get(struct thread *td, struct cap_fcntls_get_args *uap)
{
return (ENOSYS);
}
#endif /* CAPABILITIES */
