In my first reading of POSIX.1e, I misinterpreted handling of the

ACL_USER_OBJ and ACL_GROUP_OBJ fields, believing that modification of the
access ACL could be used by privileged processes to change file/directory
ownership.  In fact, this is incorrect; ACL_*_OBJ (+ ACL_MASK and
ACL_OTHER) should have undefined ae_id fields; this commit attempts
to correct that misunderstanding.

o Modify arguments to vaccess_acl_posix1e() to accept the uid and gid
  associated with the vnode, as those can no longer be extracted from
  the ACL passed as an argument.  Perform all comparisons against
  the passed arguments.  This actually has the effect of simplifying
  a number of components of this call, as well as reducing the indent
  level, but now seperates handling of ACL_GROUP_OBJ from ACL_GROUP.

o Modify acl_posix1e_check() to return EINVAL if the ae_id field of
  any of the ACL_{USER_OBJ,GROUP_OBJ,MASK,OTHER} entries is a value
  other than ACL_UNDEFINED_ID.  As a temporary work-around to allow
  clean upgrades, set the ae_id field to ACL_UNDEFINED_ID before
  each check so that this cannot cause a failure in the short term
  (this work-around will be removed when the userland libraries and
  utilities are updated to take this change into account).

o Modify ufs_sync_acl_from_inode() so that it forces
  ACL_{USER_OBJ,GROUP_OBJ,MASK,OTHER} ae_id fields to ACL_UNDEFINED_ID
  when synchronizing the ACL from the inode.

o Modify ufs_sync_inode_from_acl to not propagate uid and gid
  information to the inode from the ACL during ACL update.  Also
  modify the masking of permission bits that may be set from
  ALLPERMS to (S_IRWXU|S_IRWXG|S_IRWXO), as ACLs currently do not
  carry none-ACCESSPERMS (S_ISUID, S_ISGID, S_ISTXT).

o Modify ufs_getacl() so that when it emulates an access ACL from
  the inode, it initializes the ae_id fields to ACL_UNDEFINED_ID.

o Clean up ufs_setacl() substantially since it is no longer possible
  to perform chown/chgrp operations using vop_setacl(), so all the
  access control for that can be eliminated.

o Modify ufs_access() so that it passes owner uid and gid information
  into vaccess_acl_posix1e().

Pointed out by:	jedger
Obtained from:	TrustedBSD Project

2 files changed, 12 insertions, 88 deletions

diff --git a/sys/ufs/ufs/ufs_acl.c b/sys/ufs/ufs/ufs_acl.c
index 042136c..c78b0a4 100644
--- a/sys/ufs/ufs/ufs_acl.c
+++ b/sys/ufs/ufs/ufs_acl.c
@@ -79,23 +79,23 @@ ufs_sync_acl_from_inode(struct inode *ip, struct acl *acl)
 		case ACL_USER_OBJ:
 			acl->acl_entry[i].ae_perm = acl_posix1e_mode_to_perm(
 			    ACL_USER_OBJ, ip->i_mode);
-			acl->acl_entry[i].ae_id = ip->i_uid;
+			acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID;
 			break;
 	
 		case ACL_GROUP_OBJ:
 			acl_group_obj = &acl->acl_entry[i];
-			acl->acl_entry[i].ae_id = ip->i_gid;
+			acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID;
 			break;
 
 		case ACL_OTHER:
 			acl->acl_entry[i].ae_perm = acl_posix1e_mode_to_perm(
 			    ACL_OTHER, ip->i_mode);
-			acl->acl_entry[i].ae_id = 0;
+			acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID;
 			break;
 
 		case ACL_MASK:
 			acl_mask = &acl->acl_entry[i];
-			acl->acl_entry[i].ae_id = 0;
+			acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID;
 			break;
 
 		case ACL_USER:
@@ -159,12 +159,10 @@ ufs_sync_inode_from_acl(struct acl *acl, struct inode *ip,
 		switch (acl->acl_entry[i].ae_tag) {
 		case ACL_USER_OBJ:
 			acl_user_obj = &acl->acl_entry[i];
-			ip->i_uid = acl->acl_entry[i].ae_id;
 			break;
 
 		case ACL_GROUP_OBJ:
 			acl_group_obj = &acl->acl_entry[i];
-			ip->i_gid = acl->acl_entry[i].ae_id;
 			break;
 
 		case ACL_OTHER:
@@ -191,14 +189,14 @@ ufs_sync_inode_from_acl(struct acl *acl, struct inode *ip,
 		/*
 		 * There is no ACL_MASK, so use the ACL_GROUP_OBJ entry.
 		 */
-		ip->i_mode &= ~ALLPERMS;
+		ip->i_mode &= ~(S_IRWXU|S_IRWXG|S_IRWXO);
 		ip->i_mode |= acl_posix1e_perms_to_mode(acl_user_obj,
 		    acl_group_obj, acl_other);
 	} else {
 		/*
 		 * Use the ACL_MASK entry.
 		 */
-		ip->i_mode &= ~ALLPERMS;
+		ip->i_mode &= ~(S_IRWXU|S_IRWXG|S_IRWXO);
 		ip->i_mode |= acl_posix1e_perms_to_mode(acl_user_obj,
 		    acl_mask, acl_other);
 	}
@@ -257,13 +255,13 @@ ufs_getacl(ap)
 			 */
 			ap->a_aclp->acl_cnt = 3;
 			ap->a_aclp->acl_entry[0].ae_tag = ACL_USER_OBJ;
-			ap->a_aclp->acl_entry[0].ae_id = 0;
+			ap->a_aclp->acl_entry[0].ae_id = ACL_UNDEFINED_ID;
 			ap->a_aclp->acl_entry[0].ae_perm = 0;
 			ap->a_aclp->acl_entry[1].ae_tag = ACL_GROUP_OBJ;
-			ap->a_aclp->acl_entry[1].ae_id = 0;
+			ap->a_aclp->acl_entry[1].ae_id = ACL_UNDEFINED_ID;
 			ap->a_aclp->acl_entry[1].ae_perm = 0;
 			ap->a_aclp->acl_entry[2].ae_tag = ACL_OTHER;
-			ap->a_aclp->acl_entry[2].ae_id = 0;
+			ap->a_aclp->acl_entry[2].ae_id = ACL_UNDEFINED_ID;
 			ap->a_aclp->acl_entry[2].ae_perm = 0;
 			ufs_sync_acl_from_inode(ip, ap->a_aclp);
 			error = 0;
@@ -359,11 +357,8 @@ ufs_setacl(ap)
 	} */ *ap;
 {
 	struct inode *ip = VTOI(ap->a_vp);
-	struct acl_entry *acl_user_obj, *acl_group_obj, *acl_other;
 	mode_t old_mode, preserve_mask;
-	uid_t old_uid, new_uid = 0;
-	gid_t old_gid, new_gid = 0;
-	int error, i;
+	int error;
 
 	/*
 	 * If this is a set operation rather than a delete operation,
@@ -405,64 +400,6 @@ ufs_setacl(ap)
 	if ((error = VOP_ACCESS(ap->a_vp, VADMIN, ap->a_cred, ap->a_p)))
 		return (error);
 
-	/*
-	 * ACL_TYPE_ACCESS may involve the changing of ownership, sticky
-	 * bit, setugid bits on the file or directory.  As such, it requires
-	 * special handling to identify these changes, and to authorize
-	 * them.
-	 * ACL_TYPE_DEFAULT does not require this, and ap->a_aclp should
-	 * not be dereferenced without a NULL check, as it may be a delete
-	 * operation.
-	 */
-	switch(ap->a_type) {
-	case ACL_TYPE_ACCESS:
-		/*
-		 * Identify ACL_USER_OBJ, ACL_GROUP_OBJ, and determine if
-		 * they have changed.  If so, authorize in the style of
-		 * ufs_chown().  While we're at it, identify ACL_OTHER.
-	 	 */
-		acl_user_obj = acl_group_obj = acl_other = NULL;
-		for (i = 0; i < ap->a_aclp->acl_cnt; i++)
-			switch(ap->a_aclp->acl_entry[i].ae_tag) {
-			case ACL_USER_OBJ:
-				acl_user_obj = &ap->a_aclp->acl_entry[i];
-				new_uid = acl_user_obj->ae_id;
-				break;
-			case ACL_GROUP_OBJ:
-				acl_group_obj = &ap->a_aclp->acl_entry[i];
-				new_gid = acl_group_obj->ae_id;
-				break;
-			case ACL_OTHER:
-				acl_other = &ap->a_aclp->acl_entry[i];
-				break;
-			default:
-			}
-		old_uid = ip->i_uid;
-		old_gid = ip->i_gid;
-
-		/*
-		 * Authorize changes to base object ownership in the style
-		 * of ufs_chown().
-		 */
-		if (new_uid != old_uid && (error = suser_xxx(ap->a_cred,
-		    ap->a_p, PRISON_ROOT)))
-			return (error);
-		if (new_gid != old_gid && !groupmember(new_gid, ap->a_cred) &&
-		    (error = suser_xxx(ap->a_cred, ap->a_p, PRISON_ROOT)))
-			return (error);
-
-	case ACL_TYPE_DEFAULT:
-		/*
-		 * ACL_TYPE_DEFAULT can literally be written straight into
-		 * the EA unhindered, as it has gone through sanity checking
-		 * already.
-	 	 */
-		break;
-
-	default:
-		panic("ufs_setacl(): unknown acl type\n");
-	}
-
 	switch(ap->a_type) {
 	case ACL_TYPE_ACCESS:
 		error = vn_extattr_set(ap->a_vp, IO_NODELOCKED,
@@ -509,22 +446,9 @@ ufs_setacl(ap)
 		 * Now that the EA is successfully updated, update the
 		 * inode and mark it as changed.
 		 */
-		old_uid = ip->i_uid;
-		old_gid = ip->i_gid;
 		old_mode = ip->i_mode;
 		preserve_mask = ISVTX | ISGID | ISUID;
 		ufs_sync_inode_from_acl(ap->a_aclp, ip, preserve_mask);
-
-		/*
-		 * Clear the ISGID and ISUID bits if the ownership has
-		 * changed, or appropriate privilege is not available.
-		 * XXX: This should probably be a check for broadening
-		 * availability of the bits, but it's not clear from the
-		 * spec.
-		 */
-		if (suser_xxx(ap->a_cred, NULL, PRISON_ROOT) &&
-		    (ip->i_gid != old_gid || ip->i_uid != old_uid))
-			ip->i_mode &= ~(ISUID | ISGID);
 		ip->i_flag |= IN_CHANGE;
 	}
 
diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
index 9db19e2..0b65496 100644
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -353,8 +353,8 @@ ufs_access(ap)
 		    ap->a_mode, ap->a_cred, NULL);
 		break;
 	case 0:
-		error = vaccess_acl_posix1e(vp->v_type, acl, ap->a_mode,
-		    ap->a_cred, NULL);
+		error = vaccess_acl_posix1e(vp->v_type, ip->i_uid, ip->i_gid,
+		    acl, ap->a_mode, ap->a_cred, NULL);
 		break;
 	default:
 		printf("ufs_access(): Error retrieving ACL on object (%d).\n",