[NTOS:CM] Implement cache lookup and cleanup subkey information for cache consistency

During an open or create procedure of a registry key, the registry parser grabs
a key control block (KCB) from the parser object and uses its information to do the
necessary work in order to obtain a pointer to the newly created or opened registry key.

However, the registry parsers faces several issues. First, we don't do subkey cache cleaning
information against gathered KCBs so whenever we do a registry parse we end up with KCBs
that have cache inconsistencies. Moreover we don't do any locking of whatever KCB we
are grabing during a parse procedure.

=== PROPOSED CHANGES ===

* Implement CmpComputeHashValue and CmpLookInCache functions. With CmpComputeHashValue we can
compute the convkey hashes of each subkey in the path name of a key so we can lock them
with CmpBuildAndLockKcbArray. CmpLookInCache is a function that searches for the suitable
KCB in the cache. The factors that determine if a KCB is "suitable" are:

-- the currently found KCB in the hash list has the same levels as that of the
given KCB from the parse object;

-- The key names from the computed hash values match with the block name of
the KCB;

-- The currently found KCB is not deleted.

The KCB will be changed if the key path name points to a partial match name in
the cache. The KCB from the parse object will be used if we have a full match
of remaining levels.

* Add missing CMP_LOCK_HASHES_FOR_KCB flags on CmpCreateKeyControlBlock calls
that create KCBs during a parse procedure. Such lock has to be preserved until
we're done with the registry parsing.

* On CmpDoCreateChild, preserve the exclusive lock of the KCB when we are
enlisting the key body.

* On CmpDoCreate, make sure that the passed parent KCB is locked exclusively and
lock the hiver flusher as we don't want the flusher to kick in during a key
creation on the given hive. Cleanup the subkey info when we're creating a key
object. Also implement missing cleanup path codes. Furthermore, avoid key
object creation if the parent KCB is protected with a read-only switch.

* Soft rewrite the CmpDoOpen function, namely how we manage a direct open vs
create KCB on open scenario. When a KCB is found in cache avoid touching
the key node. If the symbolic link has been resolved (aka found) then lock
exclusively the symbolic KCB. Otherwise just give the cached KCB to the caller.

If it were for the caller to request a KCB creation, we must check the passed
KCB from the parser object is locked exclusively, unlike on the case above
the caller doesn't want to create a KCB because there's already one in the cache.
We don't want anybody to touch our KCB while we are still toying with it during
its birth. Furthermore, enlist the key body but mind the kind of lock it's been
used.

* On CmpCreateLinkNode, avoid creating a key object if the parent KCB is protected
with a read-only switch. In addition, add missing hive flusher locks for both
the target hive and its child. Cleanup the subkey information of the KCB when
creating a link node, this ensures our cached KCB data remains consistent.

* Do a direct open on CmpParseKey if no remaining subkey levels have been found
during hash computation and cache lookup, in this case the given KCB is the
block that points to the exact key. This happens when for example someone tried
to call RegOpenKeyExW but submitting NULL to the lpSubKey argument parameter.

CORE-10581
ROSTESTS-198
This commit is contained in:
George Bișoc 2023-02-16 21:42:26 +01:00
parent 8cb56e77a6
commit f4de5ceb9e
No known key found for this signature in database
GPG key ID: 688C4FBE25D7DEF6
2 changed files with 761 additions and 73 deletions

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@ -1133,12 +1133,12 @@ CmpCreateLinkNode(
IN PHHIVE Hive,
IN HCELL_INDEX Cell,
IN PACCESS_STATE AccessState,
IN PULONG KcbsLocked,
IN UNICODE_STRING Name,
IN KPROCESSOR_MODE AccessMode,
IN ULONG CreateOptions,
IN PCM_PARSE_CONTEXT Context,
IN PCM_KEY_CONTROL_BLOCK ParentKcb,
IN PULONG KcbsLocked,
OUT PVOID *Object
);