freebsd-dev/sys/kern/vfs_acl.c
Pawel Jakub Dawidek 7008be5bd7 Change the cap_rights_t type from uint64_t to a structure that we can extend
in the future in a backward compatible (API and ABI) way.

The cap_rights_t represents capability rights. We used to use one bit to
represent one right, but we are running out of spare bits. Currently the new
structure provides place for 114 rights (so 50 more than the previous
cap_rights_t), but it is possible to grow the structure to hold at least 285
rights, although we can make it even larger if 285 rights won't be enough.

The structure definition looks like this:

	struct cap_rights {
		uint64_t	cr_rights[CAP_RIGHTS_VERSION + 2];
	};

The initial CAP_RIGHTS_VERSION is 0.

The top two bits in the first element of the cr_rights[] array contain total
number of elements in the array - 2. This means if those two bits are equal to
0, we have 2 array elements.

The top two bits in all remaining array elements should be 0.
The next five bits in all array elements contain array index. Only one bit is
used and bit position in this five-bits range defines array index. This means
there can be at most five array elements in the future.

To define new right the CAPRIGHT() macro must be used. The macro takes two
arguments - an array index and a bit to set, eg.

	#define	CAP_PDKILL	CAPRIGHT(1, 0x0000000000000800ULL)

We still support aliases that combine few rights, but the rights have to belong
to the same array element, eg:

	#define	CAP_LOOKUP	CAPRIGHT(0, 0x0000000000000400ULL)
	#define	CAP_FCHMOD	CAPRIGHT(0, 0x0000000000002000ULL)

	#define	CAP_FCHMODAT	(CAP_FCHMOD | CAP_LOOKUP)

There is new API to manage the new cap_rights_t structure:

	cap_rights_t *cap_rights_init(cap_rights_t *rights, ...);
	void cap_rights_set(cap_rights_t *rights, ...);
	void cap_rights_clear(cap_rights_t *rights, ...);
	bool cap_rights_is_set(const cap_rights_t *rights, ...);

	bool cap_rights_is_valid(const cap_rights_t *rights);
	void cap_rights_merge(cap_rights_t *dst, const cap_rights_t *src);
	void cap_rights_remove(cap_rights_t *dst, const cap_rights_t *src);
	bool cap_rights_contains(const cap_rights_t *big, const cap_rights_t *little);

Capability rights to the cap_rights_init(), cap_rights_set(),
cap_rights_clear() and cap_rights_is_set() functions are provided by
separating them with commas, eg:

	cap_rights_t rights;

	cap_rights_init(&rights, CAP_READ, CAP_WRITE, CAP_FSTAT);

There is no need to terminate the list of rights, as those functions are
actually macros that take care of the termination, eg:

	#define	cap_rights_set(rights, ...)				\
		__cap_rights_set((rights), __VA_ARGS__, 0ULL)
	void __cap_rights_set(cap_rights_t *rights, ...);

Thanks to using one bit as an array index we can assert in those functions that
there are no two rights belonging to different array elements provided
together. For example this is illegal and will be detected, because CAP_LOOKUP
belongs to element 0 and CAP_PDKILL to element 1:

	cap_rights_init(&rights, CAP_LOOKUP | CAP_PDKILL);

Providing several rights that belongs to the same array's element this way is
correct, but is not advised. It should only be used for aliases definition.

This commit also breaks compatibility with some existing Capsicum system calls,
but I see no other way to do that. This should be fine as Capsicum is still
experimental and this change is not going to 9.x.

Sponsored by:	The FreeBSD Foundation
2013-09-05 00:09:56 +00:00

563 lines
13 KiB
C

/*-
* Copyright (c) 1999-2006 Robert N. M. Watson
* All rights reserved.
*
* This software was developed by Robert Watson for the TrustedBSD Project.
*
* 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.
*/
/*
* Developed by the TrustedBSD Project.
*
* ACL system calls and other functions common across different ACL types.
* Type-specific routines go into subr_acl_<type>.c.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/capability.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/proc.h>
#include <sys/sysent.h>
#include <sys/acl.h>
#include <security/mac/mac_framework.h>
CTASSERT(ACL_MAX_ENTRIES >= OLDACL_MAX_ENTRIES);
MALLOC_DEFINE(M_ACL, "acl", "Access Control Lists");
static int vacl_set_acl(struct thread *td, struct vnode *vp,
acl_type_t type, struct acl *aclp);
static int vacl_get_acl(struct thread *td, struct vnode *vp,
acl_type_t type, struct acl *aclp);
static int vacl_aclcheck(struct thread *td, struct vnode *vp,
acl_type_t type, struct acl *aclp);
int
acl_copy_oldacl_into_acl(const struct oldacl *source, struct acl *dest)
{
int i;
if (source->acl_cnt < 0 || source->acl_cnt > OLDACL_MAX_ENTRIES)
return (EINVAL);
bzero(dest, sizeof(*dest));
dest->acl_cnt = source->acl_cnt;
dest->acl_maxcnt = ACL_MAX_ENTRIES;
for (i = 0; i < dest->acl_cnt; i++) {
dest->acl_entry[i].ae_tag = source->acl_entry[i].ae_tag;
dest->acl_entry[i].ae_id = source->acl_entry[i].ae_id;
dest->acl_entry[i].ae_perm = source->acl_entry[i].ae_perm;
}
return (0);
}
int
acl_copy_acl_into_oldacl(const struct acl *source, struct oldacl *dest)
{
int i;
if (source->acl_cnt > OLDACL_MAX_ENTRIES)
return (EINVAL);
bzero(dest, sizeof(*dest));
dest->acl_cnt = source->acl_cnt;
for (i = 0; i < dest->acl_cnt; i++) {
dest->acl_entry[i].ae_tag = source->acl_entry[i].ae_tag;
dest->acl_entry[i].ae_id = source->acl_entry[i].ae_id;
dest->acl_entry[i].ae_perm = source->acl_entry[i].ae_perm;
}
return (0);
}
/*
* At one time, "struct ACL" was extended in order to add support for NFSv4
* ACLs. Instead of creating compatibility versions of all the ACL-related
* syscalls, they were left intact. It's possible to find out what the code
* calling these syscalls (libc) expects basing on "type" argument - if it's
* either ACL_TYPE_ACCESS_OLD or ACL_TYPE_DEFAULT_OLD (which previously were
* known as ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT), then it's the "struct
* oldacl". If it's something else, then it's the new "struct acl". In the
* latter case, the routines below just copyin/copyout the contents. In the
* former case, they copyin the "struct oldacl" and convert it to the new
* format.
*/
static int
acl_copyin(void *user_acl, struct acl *kernel_acl, acl_type_t type)
{
int error;
struct oldacl old;
switch (type) {
case ACL_TYPE_ACCESS_OLD:
case ACL_TYPE_DEFAULT_OLD:
error = copyin(user_acl, &old, sizeof(old));
if (error != 0)
break;
acl_copy_oldacl_into_acl(&old, kernel_acl);
break;
default:
error = copyin(user_acl, kernel_acl, sizeof(*kernel_acl));
if (kernel_acl->acl_maxcnt != ACL_MAX_ENTRIES)
return (EINVAL);
}
return (error);
}
static int
acl_copyout(struct acl *kernel_acl, void *user_acl, acl_type_t type)
{
int error;
struct oldacl old;
switch (type) {
case ACL_TYPE_ACCESS_OLD:
case ACL_TYPE_DEFAULT_OLD:
error = acl_copy_acl_into_oldacl(kernel_acl, &old);
if (error != 0)
break;
error = copyout(&old, user_acl, sizeof(old));
break;
default:
if (fuword32((char *)user_acl +
offsetof(struct acl, acl_maxcnt)) != ACL_MAX_ENTRIES)
return (EINVAL);
error = copyout(kernel_acl, user_acl, sizeof(*kernel_acl));
}
return (error);
}
/*
* Convert "old" type - ACL_TYPE_{ACCESS,DEFAULT}_OLD - into its "new"
* counterpart. It's required for old (pre-NFSv4 ACLs) libc to work
* with new kernel. Fixing 'type' for old binaries with new libc
* is being done in lib/libc/posix1e/acl_support.c:_acl_type_unold().
*/
static int
acl_type_unold(int type)
{
switch (type) {
case ACL_TYPE_ACCESS_OLD:
return (ACL_TYPE_ACCESS);
case ACL_TYPE_DEFAULT_OLD:
return (ACL_TYPE_DEFAULT);
default:
return (type);
}
}
/*
* These calls wrap the real vnode operations, and are called by the syscall
* code once the syscall has converted the path or file descriptor to a vnode
* (unlocked). The aclp pointer is assumed still to point to userland, so
* this should not be consumed within the kernel except by syscall code.
* Other code should directly invoke VOP_{SET,GET}ACL.
*/
/*
* Given a vnode, set its ACL.
*/
static int
vacl_set_acl(struct thread *td, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl *inkernelacl;
struct mount *mp;
int error;
inkernelacl = acl_alloc(M_WAITOK);
error = acl_copyin(aclp, inkernelacl, type);
if (error != 0)
goto out;
error = vn_start_write(vp, &mp, V_WAIT | PCATCH);
if (error != 0)
goto out;
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
#ifdef MAC
error = mac_vnode_check_setacl(td->td_ucred, vp, type, inkernelacl);
if (error != 0)
goto out_unlock;
#endif
error = VOP_SETACL(vp, acl_type_unold(type), inkernelacl,
td->td_ucred, td);
#ifdef MAC
out_unlock:
#endif
VOP_UNLOCK(vp, 0);
vn_finished_write(mp);
out:
acl_free(inkernelacl);
return (error);
}
/*
* Given a vnode, get its ACL.
*/
static int
vacl_get_acl(struct thread *td, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl *inkernelacl;
int error;
inkernelacl = acl_alloc(M_WAITOK | M_ZERO);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
#ifdef MAC
error = mac_vnode_check_getacl(td->td_ucred, vp, type);
if (error != 0)
goto out;
#endif
error = VOP_GETACL(vp, acl_type_unold(type), inkernelacl,
td->td_ucred, td);
#ifdef MAC
out:
#endif
VOP_UNLOCK(vp, 0);
if (error == 0)
error = acl_copyout(inkernelacl, aclp, type);
acl_free(inkernelacl);
return (error);
}
/*
* Given a vnode, delete its ACL.
*/
static int
vacl_delete(struct thread *td, struct vnode *vp, acl_type_t type)
{
struct mount *mp;
int error;
error = vn_start_write(vp, &mp, V_WAIT | PCATCH);
if (error != 0)
return (error);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
#ifdef MAC
error = mac_vnode_check_deleteacl(td->td_ucred, vp, type);
if (error != 0)
goto out;
#endif
error = VOP_SETACL(vp, acl_type_unold(type), 0, td->td_ucred, td);
#ifdef MAC
out:
#endif
VOP_UNLOCK(vp, 0);
vn_finished_write(mp);
return (error);
}
/*
* Given a vnode, check whether an ACL is appropriate for it
*/
static int
vacl_aclcheck(struct thread *td, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl *inkernelacl;
int error;
inkernelacl = acl_alloc(M_WAITOK);
error = acl_copyin(aclp, inkernelacl, type);
if (error != 0)
goto out;
error = VOP_ACLCHECK(vp, acl_type_unold(type), inkernelacl,
td->td_ucred, td);
out:
acl_free(inkernelacl);
return (error);
}
/*
* syscalls -- convert the path/fd to a vnode, and call vacl_whatever. Don't
* need to lock, as the vacl_ code will get/release any locks required.
*/
/*
* Given a file path, get an ACL for it
*/
int
sys___acl_get_file(struct thread *td, struct __acl_get_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_get_acl(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, get an ACL for it; don't follow links.
*/
int
sys___acl_get_link(struct thread *td, struct __acl_get_link_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_get_acl(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, set an ACL for it.
*/
int
sys___acl_set_file(struct thread *td, struct __acl_set_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_set_acl(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, set an ACL for it; don't follow links.
*/
int
sys___acl_set_link(struct thread *td, struct __acl_set_link_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_set_acl(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file descriptor, get an ACL for it.
*/
int
sys___acl_get_fd(struct thread *td, struct __acl_get_fd_args *uap)
{
struct file *fp;
cap_rights_t rights;
int error;
error = getvnode(td->td_proc->p_fd, uap->filedes,
cap_rights_init(&rights, CAP_ACL_GET), &fp);
if (error == 0) {
error = vacl_get_acl(td, fp->f_vnode, uap->type, uap->aclp);
fdrop(fp, td);
}
return (error);
}
/*
* Given a file descriptor, set an ACL for it.
*/
int
sys___acl_set_fd(struct thread *td, struct __acl_set_fd_args *uap)
{
struct file *fp;
cap_rights_t rights;
int error;
error = getvnode(td->td_proc->p_fd, uap->filedes,
cap_rights_init(&rights, CAP_ACL_SET), &fp);
if (error == 0) {
error = vacl_set_acl(td, fp->f_vnode, uap->type, uap->aclp);
fdrop(fp, td);
}
return (error);
}
/*
* Given a file path, delete an ACL from it.
*/
int
sys___acl_delete_file(struct thread *td, struct __acl_delete_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_delete(td, nd.ni_vp, uap->type);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, delete an ACL from it; don't follow links.
*/
int
sys___acl_delete_link(struct thread *td, struct __acl_delete_link_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_delete(td, nd.ni_vp, uap->type);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, delete an ACL from it.
*/
int
sys___acl_delete_fd(struct thread *td, struct __acl_delete_fd_args *uap)
{
struct file *fp;
cap_rights_t rights;
int error;
error = getvnode(td->td_proc->p_fd, uap->filedes,
cap_rights_init(&rights, CAP_ACL_DELETE), &fp);
if (error == 0) {
error = vacl_delete(td, fp->f_vnode, uap->type);
fdrop(fp, td);
}
return (error);
}
/*
* Given a file path, check an ACL for it.
*/
int
sys___acl_aclcheck_file(struct thread *td, struct __acl_aclcheck_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_aclcheck(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file path, check an ACL for it; don't follow links.
*/
int
sys___acl_aclcheck_link(struct thread *td, struct __acl_aclcheck_link_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->path, td);
error = namei(&nd);
if (error == 0) {
error = vacl_aclcheck(td, nd.ni_vp, uap->type, uap->aclp);
NDFREE(&nd, 0);
}
return (error);
}
/*
* Given a file descriptor, check an ACL for it.
*/
int
sys___acl_aclcheck_fd(struct thread *td, struct __acl_aclcheck_fd_args *uap)
{
struct file *fp;
cap_rights_t rights;
int error;
error = getvnode(td->td_proc->p_fd, uap->filedes,
cap_rights_init(&rights, CAP_ACL_CHECK), &fp);
if (error == 0) {
error = vacl_aclcheck(td, fp->f_vnode, uap->type, uap->aclp);
fdrop(fp, td);
}
return (error);
}
struct acl *
acl_alloc(int flags)
{
struct acl *aclp;
aclp = malloc(sizeof(*aclp), M_ACL, flags);
if (aclp == NULL)
return (NULL);
aclp->acl_maxcnt = ACL_MAX_ENTRIES;
return (aclp);
}
void
acl_free(struct acl *aclp)
{
free(aclp, M_ACL);
}