From: Volker Lendecke <vl@samba.org>
Date: Tue, 20 Dec 2022 20:26:10 +0000 (+0100)
Subject: smbd: Hide the SMB1 posix symlink behaviour behind UCF_LCOMP_LNK_OK
X-Git-Tag: talloc-2.4.0~152
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=636daef0fef98d79161377aab78ca6c403cb71c3;p=thirdparty%2Fsamba.git

smbd: Hide the SMB1 posix symlink behaviour behind UCF_LCOMP_LNK_OK

This will be used in the future to also open symlinks as reparse
points, so this won't be specific to only SMB1 posix extensions.

I have tried to avoid additional flags for several weeks by making
openat_pathref_fsp or other flavors of this to always open fsp's with
symlink O_PATH opens, because I think NT_STATUS_OBJECT_NAME_NOT_FOUND
with a valid stat is a really bad and racy way to express that we just
hit a symlink, but I miserably failed. Adding additional flags (another one
will follow) is wrong, but I don't see another way right now.

Signed-off-by: Volker Lendecke <vl@samba.org>
---

diff --git a/source3/smbd/filename.c b/source3/smbd/filename.c
index be24854f89c..73e88add2c3 100644
--- a/source3/smbd/filename.c
+++ b/source3/smbd/filename.c
@@ -41,6 +41,10 @@ uint32_t ucf_flags_from_smb_request(struct smb_request *req)
 
 	if (req->posix_pathnames) {
 		ucf_flags |= UCF_POSIX_PATHNAMES;
+
+		if (!req->sconn->using_smb2) {
+			ucf_flags |= UCF_LCOMP_LNK_OK;
+		}
 	}
 	if (req->flags2 & FLAGS2_DFS_PATHNAMES) {
 		ucf_flags |= UCF_DFS_PATHNAME;
@@ -1251,7 +1255,7 @@ static NTSTATUS filename_convert_dirfsp_nosymlink(
 		 * In SMB1 posix mode, if this is a symlink,
 		 * allow access to the name with a NULL smb_fname->fsp.
 		 */
-		if (!conn->sconn->using_smb2 && posix) {
+		if (ucf_flags & UCF_LCOMP_LNK_OK) {
 			SMB_ASSERT(smb_fname_rel->fsp == NULL);
 			SMB_ASSERT(streamname == NULL);
 
diff --git a/source3/smbd/smbd.h b/source3/smbd/smbd.h
index 6cf2b64a5a1..1c98bea4334 100644
--- a/source3/smbd/smbd.h
+++ b/source3/smbd/smbd.h
@@ -84,6 +84,10 @@ struct trans_state {
 #define UCF_POSIX_PATHNAMES		0x00000008
 /* #define UCF_UNIX_NAME_LOOKUP 0x00000010 is no longer used. */
 #define UCF_PREP_CREATEFILE		0x00000020
+/*
+ * Return a non-fsp smb_fname for a symlink
+ */
+#define UCF_LCOMP_LNK_OK                0x00000040
 /*
  * Use the same bit as FLAGS2_REPARSE_PATH
  * which means the same thing.