From: Jeremy Allison <jra@samba.org>
Date: Mon, 28 Jun 2021 20:54:52 +0000 (-0700)
Subject: s3: smbd: Explicitly code the semantics of "dos filemode" into the chown code.
X-Git-Tag: talloc-2.3.3~82
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0657db26447ad9b0d2130fe07163e953eba2bcc2;p=thirdparty%2Fsamba.git

s3: smbd: Explicitly code the semantics of "dos filemode" into the chown code.

We actually don't need this to get the right semantics, as the open or the
set_sd() code catches the correct cases and returns ACCESS_DENIED, but it
makes me much happier to see the prerequisites needed expressed in code here
right at the point of use.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Tue Jul 13 08:11:36 UTC 2021 on sn-devel-184
---

diff --git a/source3/smbd/posix_acls.c b/source3/smbd/posix_acls.c
index 8bfaea27e39..899e7dc3c1e 100644
--- a/source3/smbd/posix_acls.c
+++ b/source3/smbd/posix_acls.c
@@ -3440,9 +3440,24 @@ NTSTATUS try_chown(files_struct *fsp, uid_t uid, gid_t gid)
 	}
 
 	/* Case (4). */
+	/* If "dos filemode" isn't set, we're done. */
 	if (!lp_dos_filemode(SNUM(fsp->conn))) {
 		return NT_STATUS_ACCESS_DENIED;
 	}
+	/*
+	 * If we have a writable handle, obviously we
+	 * can write to the file.
+	 */
+	if (!fsp->fsp_flags.can_write) {
+		/*
+		 * If we don't have a writable handle, we
+		 * need to read the ACL on the file to
+		 * see if we can write to it.
+		 */
+		if (!can_write_to_fsp(fsp)) {
+			return NT_STATUS_ACCESS_DENIED;
+		}
+	}
 
 	/* only allow chown to the current user. This is more secure,
 	   and also copes with the case where the SID in a take ownership ACL is