Created attachment 18657 [details]
unx_mode variable is set correctly with variable smb_fname->st.st_ex_mode

Problem description
File creation via SMB protocol in folders with ACL inheritance

It has identified potential security leak or data access loss issue for files created from SMB clients. The issue may appear when SMB clients create files in folders that use ACL inheritance to change ACLs (additional access to groups, reduced access to a users primary group) from the default access mask.

Detailed Description:

To reproduce:

1) Have a directory with an NFSV4 ACL where permissions are inherited to
at least new files, e.g like this:

| # mmgetacl .
| #NFSv4 ACL
| #owner:<user>
| #group:<group>
| special:owner@:rwxc:allow:FileInherit:DirInherit:Inherited
|  (X)READ/LIST (X)WRITE/CREATE (X)APPEND/MKDIR (X)SYNCHRONIZE (X)READ_ACL  (X)READ_ATTR  (X)READ_NAMED
|  (X)DELETE    (X)DELETE_CHILD (-)CHOWN        (X)EXEC/SEARCH (X)WRITE_ACL (X)WRITE_ATTR (X)WRITE_NAMED
|
| special:group@:rwxc:allow:FileInherit:DirInherit:Inherited
|  (X)READ/LIST (X)WRITE/CREATE (X)APPEND/MKDIR (X)SYNCHRONIZE (X)READ_ACL  (X)READ_ATTR  (X)READ_NAMED
|  (X)DELETE    (X)DELETE_CHILD (-)CHOWN        (X)EXEC/SEARCH (X)WRITE_ACL (X)WRITE_ATTR (X)WRITE_NAMED
|
| special:everyone@:----:allow:FileInherit:DirInherit:Inherited
|  (-)READ/LIST (-)WRITE/CREATE (-)APPEND/MKDIR (-)SYNCHRONIZE (-)READ_ACL  (-)READ_ATTR  (-)READ_NAMED
|  (-)DELETE    (-)DELETE_CHILD (-)CHOWN        (-)EXEC/SEARCH (-)WRITE_ACL (-)WRITE_ATTR (-)WRITE_NAMED

2) From windows command line, where the SMB mounted directory is current
directory, create a file the simplest way possible to exclude the
possibility that some software overrrides permissions, e.g:

| dir > dir.txt

3) Check the ACL for the new file:

| # mmgetacl dir.txt

4) Has the new file inherited file permissions as it should, or is it
the same wrong permissions we see?

| #NFSv4 ACL
| #owner:<user>
| #group:<group>
| #ACL flags:
| #  NULL_DACL
| #  NULL_SACL
| special:owner@:rwxc:allow:Inherited
|  (X)READ/LIST (X)WRITE/CREATE (X)APPEND/MKDIR (X)SYNCHRONIZE (X)READ_ACL  (X)READ_ATTR  (X)READ_NAMED
|  (X)DELETE    (X)DELETE_CHILD (-)CHOWN        (X)EXEC/SEARCH (X)WRITE_ACL (X)WRITE_ATTR (X)WRITE_NAMED
|
| special:group@:r--c:allow:Inherited
|  (X)READ/LIST (-)WRITE/CREATE (-)APPEND/MKDIR (X)SYNCHRONIZE (X)READ_ACL  (X)READ_ATTR  (X)READ_NAMED
|  (X)DELETE    (X)DELETE_CHILD (-)CHOWN        (-)EXEC/SEARCH (X)WRITE_ACL (X)WRITE_ATTR (X)WRITE_NAMED
|
| special:everyone@:r---:allow:Inherited
|  (X)READ/LIST (-)WRITE/CREATE (-)APPEND/MKDIR (-)SYNCHRONIZE (-)READ_ACL  (-)READ_ATTR  (-)READ_NAMED
|  (-)DELETE    (-)DELETE_CHILD (-)CHOWN        (-)EXEC/SEARCH (-)WRITE_ACL (-)WRITE_ATTR (-)WRITE_NAMED
 
Fix:
unx_mode and st_ex_mode are compared and executing the SMB_VFS_FCHMOD which not expected, so unx_mode need to be set correctly in function possibly_set_archive.