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OpenZFS 6762 - POSIX write should imply DELETE_CHILD on directories
- and some additional considerations Authored by: Kevin Crowe <kevin.crowe@nexenta.com> Reviewed by: Gordon Ross <gwr@nexenta.com> Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Paul B. Henson <henson@acm.org> OpenZFS-issue: https://www.illumos.org/issues/6762 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/1eb4e906ec Closes #10266
This commit is contained in:
Paul B. Henson
Brian Behlendorf
parent
99495ba6ab
commit
235a856576
@ -20,8 +20,8 @@
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*/
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/*
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* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
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* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
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* Copyright (c) 2013 by Delphix. All rights reserved.
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* Copyright 2014 Nexenta Systems, Inc. All rights reserved.
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*/
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@ -2681,47 +2681,30 @@ zfs_zaccess_unix(znode_t *zp, mode_t mode, cred_t *cr)
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return (zfs_zaccess(zp, v4_mode, 0, B_FALSE, cr));
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}
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static int
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zfs_delete_final_check(znode_t *zp, znode_t *dzp,
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mode_t available_perms, cred_t *cr)
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{
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int error;
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uid_t downer;
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downer = zfs_fuid_map_id(ZTOZSB(dzp), KUID_TO_SUID(ZTOI(dzp)->i_uid),
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cr, ZFS_OWNER);
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error = secpolicy_vnode_access2(cr, ZTOI(dzp),
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downer, available_perms, S_IWUSR|S_IXUSR);
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if (error == 0)
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error = zfs_sticky_remove_access(dzp, zp, cr);
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return (error);
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}
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/* See zfs_zaccess_delete() */
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int zfs_write_implies_delete_child = 1;
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/*
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* Determine whether Access should be granted/deny, without
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* consulting least priv subsystem.
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* Determine whether delete access should be granted.
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*
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* The following chart is the recommended NFSv4 enforcement for
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* ability to delete an object.
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*
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* -------------------------------------------------------
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* | Parent Dir | Target Object Permissions |
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* | Parent Dir | Target Object Permissions |
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* | permissions | |
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* -------------------------------------------------------
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* | | ACL Allows | ACL Denies| Delete |
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* | | Delete | Delete | unspecified|
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* -------------------------------------------------------
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* | ACL Allows | Permit | Permit | Permit |
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* | DELETE_CHILD | |
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* | ACL Allows | Permit | Permit * | Permit |
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* | DELETE_CHILD | | | |
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* -------------------------------------------------------
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* | ACL Denies | Permit | Deny | Deny |
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* | ACL Denies | Permit * | Deny | Deny |
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* | DELETE_CHILD | | | |
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* -------------------------------------------------------
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* | ACL specifies | | | |
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* | only allow | Permit | Permit | Permit |
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* | only allow | Permit | Permit * | Permit |
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* | write and | | | |
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* | execute | | | |
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* -------------------------------------------------------
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@ -2731,91 +2714,175 @@ zfs_delete_final_check(znode_t *zp, znode_t *dzp,
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* -------------------------------------------------------
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* ^
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* |
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* No search privilege, can't even look up file?
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* Re. execute permission on the directory: if that's missing,
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* the vnode lookup of the target will fail before we get here.
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*
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* Re [*] in the table above: We are intentionally disregarding the
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* NFSv4 committee recommendation for these three cells of the matrix
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* because that recommendation conflicts with the behavior expected
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* by Windows clients for ACL evaluation. See acl.h for notes on
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* which ACE_... flags should be checked for which operations.
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* Specifically, the NFSv4 committee recommendation is in conflict
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* with the Windows interpretation of DENY ACEs, where DENY ACEs
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* should take precedence ahead of ALLOW ACEs.
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*
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* This implementation takes a conservative approach by checking for
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* DENY ACEs on both the target object and it's container; checking
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* the ACE_DELETE on the target object, and ACE_DELETE_CHILD on the
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* container. If a DENY ACE is found for either of those, delete
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* access is denied. (Note that DENY ACEs are very rare.)
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*
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* Note that after these changes, entire the second row and the
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* entire middle column of the table above change to Deny.
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* Accordingly, the logic here is somewhat simplified.
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*
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* First check for DENY ACEs that apply.
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* If either target or container has a deny, EACCES.
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*
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* Delete access can then be summarized as follows:
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* 1: The object to be deleted grants ACE_DELETE, or
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* 2: The containing directory grants ACE_DELETE_CHILD.
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* In a Windows system, that would be the end of the story.
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* In this system, (2) has some complications...
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* 2a: "sticky" bit on a directory adds restrictions, and
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* 2b: existing ACEs from previous versions of ZFS may
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* not carry ACE_DELETE_CHILD where they should, so we
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* also allow delete when ACE_WRITE_DATA is granted.
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*
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* Note: 2b is technically a work-around for a prior bug,
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* which hopefully can go away some day. For those who
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* no longer need the work around, and for testing, this
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* work-around is made conditional via the tunable:
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* zfs_write_implies_delete_child
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*/
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int
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zfs_zaccess_delete(znode_t *dzp, znode_t *zp, cred_t *cr)
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{
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uint32_t wanted_dirperms;
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uint32_t dzp_working_mode = 0;
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uint32_t zp_working_mode = 0;
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int dzp_error, zp_error;
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mode_t available_perms;
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boolean_t dzpcheck_privs = B_TRUE;
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boolean_t zpcheck_privs = B_TRUE;
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/*
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* We want specific DELETE permissions to
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* take precedence over WRITE/EXECUTE. We don't
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* want an ACL such as this to mess us up.
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* user:joe:write_data:deny,user:joe:delete:allow
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*
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* However, deny permissions may ultimately be overridden
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* by secpolicy_vnode_access().
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*
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* We will ask for all of the necessary permissions and then
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* look at the working modes from the directory and target object
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* to determine what was found.
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*/
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boolean_t dzpcheck_privs;
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boolean_t zpcheck_privs;
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if (zp->z_pflags & (ZFS_IMMUTABLE | ZFS_NOUNLINK))
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return (SET_ERROR(EPERM));
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/*
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* First row
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* If the directory permissions allow the delete, we are done.
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*/
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if ((dzp_error = zfs_zaccess_common(dzp, ACE_DELETE_CHILD,
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&dzp_working_mode, &dzpcheck_privs, B_FALSE, cr)) == 0)
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return (0);
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/*
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* If target object has delete permission then we are done
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*/
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if ((zp_error = zfs_zaccess_common(zp, ACE_DELETE, &zp_working_mode,
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&zpcheck_privs, B_FALSE, cr)) == 0)
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return (0);
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ASSERT(dzp_error && zp_error);
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if (!dzpcheck_privs)
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return (dzp_error);
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if (!zpcheck_privs)
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return (zp_error);
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/*
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* Second row
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* Case 1:
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* If target object grants ACE_DELETE then we are done. This is
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* indicated by a return value of 0. For this case we don't worry
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* about the sticky bit because sticky only applies to the parent
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* directory and this is the child access result.
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*
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* If directory returns EACCES then delete_child was denied
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* due to deny delete_child. In this case send the request through
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* secpolicy_vnode_remove(). We don't use zfs_delete_final_check()
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* since that *could* allow the delete based on write/execute permission
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* and we want delete permissions to override write/execute.
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* If we encounter a DENY ACE here, we're also done (EACCES).
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* Note that if we hit a DENY ACE here (on the target) it should
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* take precedence over a DENY ACE on the container, so that when
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* we have more complete auditing support we will be able to
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* report an access failure against the specific target.
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* (This is part of why we're checking the target first.)
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*/
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if (dzp_error == EACCES)
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zp_error = zfs_zaccess_common(zp, ACE_DELETE, &zp_working_mode,
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&zpcheck_privs, B_FALSE, cr);
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if (zp_error == EACCES) {
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/* We hit a DENY ACE. */
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if (!zpcheck_privs)
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return (SET_ERROR(zp_error));
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return (secpolicy_vnode_remove(cr));
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/*
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* Third Row
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* only need to see if we have write/execute on directory.
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*/
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}
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if (zp_error == 0)
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return (0);
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dzp_error = zfs_zaccess_common(dzp, ACE_EXECUTE|ACE_WRITE_DATA,
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/*
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* Case 2:
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* If the containing directory grants ACE_DELETE_CHILD,
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* or we're in backward compatibility mode and the
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* containing directory has ACE_WRITE_DATA, allow.
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* Case 2b is handled with wanted_dirperms.
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*/
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wanted_dirperms = ACE_DELETE_CHILD;
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if (zfs_write_implies_delete_child)
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wanted_dirperms |= ACE_WRITE_DATA;
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dzp_error = zfs_zaccess_common(dzp, wanted_dirperms,
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&dzp_working_mode, &dzpcheck_privs, B_FALSE, cr);
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if (dzp_error != 0 && !dzpcheck_privs)
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return (dzp_error);
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if (dzp_error == EACCES) {
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/* We hit a DENY ACE. */
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if (!dzpcheck_privs)
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return (SET_ERROR(dzp_error));
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return (secpolicy_vnode_remove(cr));
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}
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/*
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* Fourth row
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* Cases 2a, 2b (continued)
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*
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* Note: dzp_working_mode now contains any permissions
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* that were NOT granted. Therefore, if any of the
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* wanted_dirperms WERE granted, we will have:
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* dzp_working_mode != wanted_dirperms
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* We're really asking if ANY of those permissions
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* were granted, and if so, grant delete access.
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*/
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if (dzp_working_mode != wanted_dirperms)
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dzp_error = 0;
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available_perms = (dzp_working_mode & ACE_WRITE_DATA) ? 0 : S_IWUSR;
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available_perms |= (dzp_working_mode & ACE_EXECUTE) ? 0 : S_IXUSR;
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/*
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* dzp_error is 0 if the container granted us permissions to "modify".
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* If we do not have permission via one or more ACEs, our current
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* privileges may still permit us to modify the container.
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*
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* dzpcheck_privs is false when i.e. the FS is read-only.
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* Otherwise, do privilege checks for the container.
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*/
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if (dzp_error != 0 && dzpcheck_privs) {
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uid_t owner;
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return (zfs_delete_final_check(zp, dzp, available_perms, cr));
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/*
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* The secpolicy call needs the requested access and
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* the current access mode of the container, but it
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* only knows about Unix-style modes (VEXEC, VWRITE),
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* so this must condense the fine-grained ACE bits into
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* Unix modes.
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*
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* The VEXEC flag is easy, because we know that has
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* always been checked before we get here (during the
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* lookup of the target vnode). The container has not
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* granted us permissions to "modify", so we do not set
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* the VWRITE flag in the current access mode.
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*/
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owner = zfs_fuid_map_id(ZTOZSB(dzp),
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KUID_TO_SUID(ZTOI(dzp)->i_uid), cr, ZFS_OWNER);
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dzp_error = secpolicy_vnode_access2(cr, ZTOI(dzp),
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owner, S_IXUSR, S_IWUSR|S_IXUSR);
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}
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if (dzp_error != 0) {
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/*
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* Note: We may have dzp_error = -1 here (from
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* zfs_zacess_common). Don't return that.
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*/
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return (SET_ERROR(EACCES));
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}
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/*
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* At this point, we know that the directory permissions allow
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* us to modify, but we still need to check for the additional
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* restrictions that apply when the "sticky bit" is set.
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*
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* Yes, zfs_sticky_remove_access() also checks this bit, but
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* checking it here and skipping the call below is nice when
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* you're watching all of this with dtrace.
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*/
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if ((dzp->z_mode & S_ISVTX) == 0)
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return (0);
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/*
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* zfs_sticky_remove_access will succeed if:
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* 1. The sticky bit is absent.
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* 2. We pass the sticky bit restrictions.
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* 3. We have privileges that always allow file removal.
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*/
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return (zfs_sticky_remove_access(dzp, zp, cr));
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}
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int
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