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freebsd/sys/kern/kern_acl.c
Robert Watson 5293465fef o Introduce filesystem-independent POSIX.1e ACL utility routines to
support implementations of ACLs in file systems.  Introduce the
  following new functions:

      vaccess_acl_posix1e()          vaccess() that accepts an ACL
      acl_posix1e_mode_to_perm()     Convert mode bits to ACL rights
      acl_posix1e_mode_to_entry()    Build ACL entry from mode/uid/gid
      acl_posix1e_perms_to_mode()    Generate file mode from ACL
      acl_posix1e_check()            Syntax verification for ACL

  These functions allow a file system to rely on central ACL evaluation
  and syntax checking, as well as providing useful utilities to
  allow ACL-based file systems to generate mode/owner/etc information
  to return via VOP_GETATTR(), and to support file systems that split
  their ACL information over their existing inode storage (mode, uid,
  gid) and extended ACL into extended attributes (additional users,
  groups, ACL mask).

o Add prototypes for exported functions to sys/acl.h, sys/vnode.h

Reviewed by:	trustedbsd-discuss, freebsd-arch
Obtained from:	TrustedBSD Project
2001-03-06 17:28:24 +00:00

715 lines
18 KiB
C

/*-
* Copyright (c) 1999, 2000, 2001 Robert N. M. Watson
* All rights reserved.
*
* 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.
*
* $FreeBSD$
*/
/*
* Developed by the TrustedBSD Project.
* Support for POSIX.1e access control lists.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/lock.h>
#include <sys/namei.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/sysent.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/acl.h>
MALLOC_DEFINE(M_ACL, "acl", "access control list");
static int vacl_set_acl(struct proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp);
static int vacl_get_acl(struct proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp);
static int vacl_aclcheck(struct proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp);
/*
* Implement a version of vaccess() that understands POSIX.1e ACL semantics.
* Return 0 on success, else an errno value. Should be merged into
* vaccess() eventually.
*/
int
vaccess_acl_posix1e(enum vtype type, struct acl *acl, mode_t acc_mode,
struct ucred *cred, int *privused)
{
struct acl_entry *acl_other, *acl_mask;
mode_t dac_granted;
mode_t cap_granted;
mode_t acl_mask_granted;
int group_matched, i;
/*
* Look for a normal, non-privileged way to access the file/directory
* as requested. If it exists, go with that. Otherwise, attempt
* to use privileges granted via cap_granted. In some cases,
* which privileges to use may be ambiguous due to "best match",
* in which case fall back on first match for the time being.
*/
if (privused != NULL)
*privused = 0;
/*
* Determine privileges now, but don't apply until we've found
* a DAC match that has failed to allow access.
*/
#ifndef CAPABILITIES
if (suser_xxx(cred, NULL, PRISON_ROOT) == 0)
cap_granted = (VEXEC | VREAD | VWRITE | VADMIN);
else
cap_granted = 0;
#else
cap_granted = 0;
if (type == VDIR) {
if ((acc_mode & VEXEC) && !cap_check(cred, NULL,
CAP_DAC_READ_SEARCH, PRISON_ROOT))
cap_granted |= VEXEC;
} else {
if ((acc_mode & VEXEC) && !cap_check(cred, NULL,
CAP_DAC_EXECUTE, PRISON_ROOT))
cap_granted |= VEXEC;
}
if ((acc_mode & VREAD) && !cap_check(cred, NULL, CAP_DAC_READ_SEARCH,
PRISON_ROOT))
cap_granted |= VREAD;
if ((acc_mode & VWRITE) && !cap_check(cred, NULL, CAP_DAC_WRITE,
PRISON_ROOT))
cap_granted |= VWRITE;
if ((acc_mode & VADMIN) && !cap_check(cred, NULL, CAP_FOWNER,
PRISON_ROOT))
cap_granted |= VADMIN;
#endif /* CAPABILITIES */
/*
* Check the owner.
* Also, record locations of ACL_MASK and ACL_OTHER for reference
* later if the owner doesn't match.
*/
acl_mask = acl_other = NULL;
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_USER_OBJ:
if (acl->acl_entry[i].ae_id != cred->cr_uid)
break;
dac_granted = 0;
dac_granted |= VADMIN;
if (acl->acl_entry[i].ae_perm & ACL_PERM_EXEC)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_PERM_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_PERM_WRITE)
dac_granted |= VWRITE;
if ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) ==
acc_mode) {
if (privused != NULL)
*privused = 1;
return (0);
}
goto error;
case ACL_MASK:
acl_mask = &acl->acl_entry[i];
break;
case ACL_OTHER:
acl_other = &acl->acl_entry[i];
break;
default:
}
}
/*
* Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields
* are masked by an ACL_MASK entry, if any. As such, first identify
* the ACL_MASK field, then iterate through identifying potential
* user matches, then group matches. If there is no ACL_MASK,
* assume that the mask allows all requests to succeed.
* Also keep track of the location of ACL_OTHER for later consumption.
*/
if (acl_other == NULL) {
/*
* XXX: This should never happen. Only properly formatted
* ACLs should be passed to vaccess_acl_posix1e.
* Should make this a panic post-debugging.
*/
printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
return (EPERM);
}
if (acl_mask != NULL) {
acl_mask_granted = 0;
if (acl_mask->ae_perm & ACL_PERM_EXEC)
acl_mask_granted |= VEXEC;
if (acl_mask->ae_perm & ACL_PERM_READ)
acl_mask_granted |= VREAD;
if (acl_mask->ae_perm & ACL_PERM_WRITE)
acl_mask_granted |= VWRITE;
} else
acl_mask_granted = VEXEC | VREAD | VWRITE;
/*
* We have to check each type even if we know ACL_MASK will reject,
* as we need to know what match there might have been, and
* therefore what further types we might be allowed to check.
* Do the checks twice -- once without privilege, and a second time
* with, if there was a match.
*/
/*
* Check ACL_USER ACL entries.
*/
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_USER:
if (acl->acl_entry[i].ae_id != cred->cr_uid)
break;
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_PERM_EXEC)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_PERM_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_PERM_WRITE)
dac_granted |= VWRITE;
dac_granted &= acl_mask_granted;
if ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) ==
acc_mode) {
if (privused != NULL)
*privused = 1;
return (0);
}
goto error;
}
}
/*
* Group match is best-match, not first-match, so find a
* "best" match. Iterate across, testing each potential group
* match. Make sure we keep track of whether we found a match
* or not, so that we know if we can move on to ACL_OTHER.
*/
group_matched = 0;
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_GROUP_OBJ:
case ACL_GROUP:
if (groupmember(acl->acl_entry[i].ae_id, cred)) {
dac_granted = 0;
if (acl->acl_entry[i].ae_perm & ACL_PERM_EXEC)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm & ACL_PERM_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm & ACL_PERM_WRITE)
dac_granted |= VWRITE;
dac_granted &= acl_mask_granted;
if ((acc_mode & dac_granted) == acc_mode)
return (0);
group_matched = 1;
}
default:
}
}
if (group_matched == 1) {
/*
* There was a match, but it did not grant rights via
* pure DAC. Try again, this time with privilege.
*/
for (i = 0; i < acl->acl_cnt; i++) {
switch (acl->acl_entry[i].ae_tag) {
case ACL_GROUP_OBJ:
case ACL_GROUP:
if (groupmember(acl->acl_entry[i].ae_id,
cred)) {
dac_granted = 0;
if (acl->acl_entry[i].ae_perm &
ACL_PERM_EXEC)
dac_granted |= VEXEC;
if (acl->acl_entry[i].ae_perm &
ACL_PERM_READ)
dac_granted |= VREAD;
if (acl->acl_entry[i].ae_perm &
ACL_PERM_WRITE)
dac_granted |= VWRITE;
dac_granted &= acl_mask_granted;
if ((acc_mode & (dac_granted |
cap_granted)) == acc_mode) {
if (privused != NULL)
*privused = 1;
return (0);
}
}
default:
}
}
/*
* Even with privilege, group membership was not sufficient.
* Return failure.
*/
goto error;
}
/*
* Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
*/
dac_granted = 0;
if (acl_other->ae_perm & ACL_PERM_EXEC)
dac_granted |= VEXEC;
if (acl_other->ae_perm & ACL_PERM_READ)
dac_granted |= VREAD;
if (acl_other->ae_perm & ACL_PERM_WRITE)
dac_granted |= VWRITE;
if ((acc_mode & dac_granted) == acc_mode)
return (0);
if ((acc_mode & (dac_granted | cap_granted)) == acc_mode) {
if (privused != NULL)
*privused = 1;
return (0);
}
error:
return ((acc_mode & VADMIN) ? EPERM : EACCES);
}
/*
* For the purposes of file systems maintaining the _OBJ entries in an
* inode with a mode_t field, this routine converts a mode_t entry
* to an acl_perm_t.
*/
acl_perm_t
acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
{
acl_perm_t perm = 0;
switch(tag) {
case ACL_USER_OBJ:
if (mode & S_IXUSR)
perm |= ACL_PERM_EXEC;
if (mode & S_IRUSR)
perm |= ACL_PERM_READ;
if (mode & S_IWUSR)
perm |= ACL_PERM_WRITE;
return (perm);
case ACL_GROUP_OBJ:
if (mode & S_IXGRP)
perm |= ACL_PERM_EXEC;
if (mode & S_IRGRP)
perm |= ACL_PERM_READ;
if (mode & S_IWGRP)
perm |= ACL_PERM_WRITE;
return (perm);
case ACL_OTHER:
if (mode & S_IXOTH)
perm |= ACL_PERM_EXEC;
if (mode & S_IROTH)
perm |= ACL_PERM_READ;
if (mode & S_IWOTH)
perm |= ACL_PERM_WRITE;
return (perm);
default:
printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
return (0);
}
}
/*
* Given inode information (uid, gid, mode), return an acl entry of the
* appropriate type.
*/
struct acl_entry
acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
{
struct acl_entry acl_entry;
acl_entry.ae_tag = tag;
acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
switch(tag) {
case ACL_USER_OBJ:
acl_entry.ae_id = uid;
break;
case ACL_GROUP_OBJ:
acl_entry.ae_id = gid;
break;
case ACL_OTHER:
acl_entry.ae_id = 0;
break;
default:
acl_entry.ae_id = 0;
printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
}
return (acl_entry);
}
/*
* Utility function to generate a file mode given appropriate ACL entries.
*/
mode_t
acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
{
mode_t mode;
mode = 0;
if (acl_user_obj_entry->ae_perm & ACL_PERM_EXEC)
mode |= S_IXUSR;
if (acl_user_obj_entry->ae_perm & ACL_PERM_READ)
mode |= S_IRUSR;
if (acl_user_obj_entry->ae_perm & ACL_PERM_WRITE)
mode |= S_IWUSR;
if (acl_group_obj_entry->ae_perm & ACL_PERM_EXEC)
mode |= S_IXGRP;
if (acl_group_obj_entry->ae_perm & ACL_PERM_READ)
mode |= S_IRGRP;
if (acl_group_obj_entry->ae_perm & ACL_PERM_WRITE)
mode |= S_IWGRP;
if (acl_other_entry->ae_perm & ACL_PERM_EXEC)
mode |= S_IXOTH;
if (acl_other_entry->ae_perm & ACL_PERM_READ)
mode |= S_IROTH;
if (acl_other_entry->ae_perm & ACL_PERM_WRITE)
mode |= S_IWOTH;
return (mode);
}
/*
* Perform a syntactic check of the ACL, sufficient to allow an
* implementing file system to determine if it should accept this and
* rely on the POSIX.1e ACL properties.
*/
int
acl_posix1e_check(struct acl *acl)
{
int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
int num_acl_mask, num_acl_other, i;
/*
* Verify that the number of entries does not exceed the maximum
* defined for acl_t.
* Verify that the correct number of various sorts of ae_tags are
* present:
* Exactly one ACL_USER_OBJ
* Exactly one ACL_GROUP_OBJ
* Exactly one ACL_OTHER
* If any ACL_USER or ACL_GROUP entries appear, then exactly one
* ACL_MASK entry must also appear.
* Verify that all ae_perm entries are in ACL_PERM_BITS.
* Verify all ae_tag entries are understood by this implementation.
* Note: Does not check for uniqueness of qualifier (ae_id) field.
*/
num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
num_acl_mask = num_acl_other = 0;
if (acl->acl_cnt > ACL_MAX_ENTRIES || acl->acl_cnt < 0)
return (EINVAL);
for (i = 0; i < acl->acl_cnt; i++) {
/*
* Check for a valid tag.
*/
switch(acl->acl_entry[i].ae_tag) {
case ACL_USER_OBJ:
num_acl_user_obj++;
break;
case ACL_GROUP_OBJ:
num_acl_group_obj++;
break;
case ACL_USER:
num_acl_user++;
break;
case ACL_GROUP:
num_acl_group++;
break;
case ACL_OTHER:
num_acl_other++;
break;
case ACL_MASK:
num_acl_mask++;
break;
default:
return (EINVAL);
}
/*
* Check for valid perm entries.
*/
if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
ACL_PERM_BITS)
return (EINVAL);
}
if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
(num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
return (EINVAL);
if (((num_acl_group != 0) || (num_acl_user != 0)) &&
(num_acl_mask != 1))
return (EINVAL);
return (0);
}
/*
* 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 proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl inkernacl;
int error;
error = copyin(aclp, &inkernacl, sizeof(struct acl));
if (error)
return(error);
VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
error = VOP_SETACL(vp, type, &inkernacl, p->p_ucred, p);
VOP_UNLOCK(vp, 0, p);
return(error);
}
/*
* Given a vnode, get its ACL.
*/
static int
vacl_get_acl(struct proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl inkernelacl;
int error;
VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
error = VOP_GETACL(vp, type, &inkernelacl, p->p_ucred, p);
VOP_UNLOCK(vp, 0, p);
if (error == 0)
error = copyout(&inkernelacl, aclp, sizeof(struct acl));
return (error);
}
/*
* Given a vnode, delete its ACL.
*/
static int
vacl_delete(struct proc *p, struct vnode *vp, acl_type_t type)
{
int error;
VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
error = VOP_SETACL(vp, ACL_TYPE_DEFAULT, 0, p->p_ucred, p);
VOP_UNLOCK(vp, 0, p);
return (error);
}
/*
* Given a vnode, check whether an ACL is appropriate for it
*/
static int
vacl_aclcheck(struct proc *p, struct vnode *vp, acl_type_t type,
struct acl *aclp)
{
struct acl inkernelacl;
int error;
error = copyin(aclp, &inkernelacl, sizeof(struct acl));
if (error)
return(error);
error = VOP_ACLCHECK(vp, type, &inkernelacl, p->p_ucred, p);
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
__acl_get_file(struct proc *p, struct __acl_get_file_args *uap)
{
struct nameidata nd;
int error;
/* what flags are required here -- possible not LOCKLEAF? */
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
error = namei(&nd);
if (error)
return(error);
error = vacl_get_acl(p, nd.ni_vp, SCARG(uap, type), SCARG(uap, aclp));
NDFREE(&nd, 0);
return (error);
}
/*
* Given a file path, set an ACL for it
*/
int
__acl_set_file(struct proc *p, struct __acl_set_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
error = namei(&nd);
if (error)
return(error);
error = vacl_set_acl(p, nd.ni_vp, SCARG(uap, type), SCARG(uap, aclp));
NDFREE(&nd, 0);
return (error);
}
/*
* Given a file descriptor, get an ACL for it
*/
int
__acl_get_fd(struct proc *p, struct __acl_get_fd_args *uap)
{
struct file *fp;
int error;
error = getvnode(p->p_fd, SCARG(uap, filedes), &fp);
if (error)
return(error);
return vacl_get_acl(p, (struct vnode *)fp->f_data, SCARG(uap, type),
SCARG(uap, aclp));
}
/*
* Given a file descriptor, set an ACL for it
*/
int
__acl_set_fd(struct proc *p, struct __acl_set_fd_args *uap)
{
struct file *fp;
int error;
error = getvnode(p->p_fd, SCARG(uap, filedes), &fp);
if (error)
return(error);
return vacl_set_acl(p, (struct vnode *)fp->f_data, SCARG(uap, type),
SCARG(uap, aclp));
}
/*
* Given a file path, delete an ACL from it.
*/
int
__acl_delete_file(struct proc *p, struct __acl_delete_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
error = namei(&nd);
if (error)
return(error);
error = vacl_delete(p, nd.ni_vp, SCARG(uap, type));
NDFREE(&nd, 0);
return (error);
}
/*
* Given a file path, delete an ACL from it.
*/
int
__acl_delete_fd(struct proc *p, struct __acl_delete_fd_args *uap)
{
struct file *fp;
int error;
error = getvnode(p->p_fd, SCARG(uap, filedes), &fp);
if (error)
return(error);
error = vacl_delete(p, (struct vnode *)fp->f_data, SCARG(uap, type));
return (error);
}
/*
* Given a file path, check an ACL for it
*/
int
__acl_aclcheck_file(struct proc *p, struct __acl_aclcheck_file_args *uap)
{
struct nameidata nd;
int error;
NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
error = namei(&nd);
if (error)
return(error);
error = vacl_aclcheck(p, nd.ni_vp, SCARG(uap, type), SCARG(uap, aclp));
NDFREE(&nd, 0);
return (error);
}
/*
* Given a file descriptor, check an ACL for it
*/
int
__acl_aclcheck_fd(struct proc *p, struct __acl_aclcheck_fd_args *uap)
{
struct file *fp;
int error;
error = getvnode(p->p_fd, SCARG(uap, filedes), &fp);
if (error)
return(error);
return vacl_aclcheck(p, (struct vnode *)fp->f_data, SCARG(uap, type),
SCARG(uap, aclp));
}