Samba file permissions: Linux Server, Mac Client

The permissions are set on the server and are 100% dependent on ACL.

You have two options in order to attempt to solve your issue.

1st option (which may better suit your needs): try to map/match Windows and Unix ACLs.

Edit the SMB server's smb.conf file and add these parameters to the [global] section:

[global]
nt acl support = yes
acl map full control = no

The two parameters above will cause the SMB server to attempt to map/match Windows and Unix ACLs.

From the smb.conf manpage:

nt acl support (S)

       This boolean parameter controls whether smbd(8) will attempt to map
       UNIX permissions into Windows NT access control lists. The UNIX
       permissions considered are the traditional UNIX owner and group
       permissions, as well as POSIX ACLs set on any files or directories.

acl map full control (S)

       This boolean parameter controls whether smbd(8) maps a POSIX ACE
       entry of "rwx" (read/write/execute), the maximum allowed POSIX
       permission set, into a Windows ACL of "FULL CONTROL". If this
       parameter is set to true any POSIX ACE entry of "rwx" will be
       returned in a Windows ACL as "FULL CONTROL", is this parameter is
       set to false any POSIX ACE entry of "rwx" will be returned as the
       specific Windows ACL bits representing read, write and execute.

2nd option (workaround): set specific ACLs for each one of your shares.

In a nutshell, the RWX (read, write and execute) parameters are defined by these equivalent SMB parameters:

• writeable = no is equivalent to R (read only)
• writeable = yes is equivalent to RW (read and write)
• acl allow execute always = true or acl allow execute always = yes is equivalent to X (execute)

In order to set file/folder permissions for all your shares, it's necessary to edit the server's smb.conf file and then add this global setting:

[global]
acl allow execute always = false
guest ok = no
writeable = yes
available = yes
browseable = yes
printable = no
locking = yes

...which will by default force all your shared folders to forbid execution of files (acl allow execute always = false), forbid guest access (guest ok = no), allow read and edit/(re)write access to files and folders (writeable = yes), make all your shares available for use by the remote (client) users (available = yes) and make the available shares visible (browseable = yes), forbid using your shares as a printing spool directory (printable = no), and force locking of your shares if the client sends such request to the SMB server (locking = yes).

From the smb.conf manpage:

acl allow execute always (S)

       This boolean parameter controls the behaviour of smbd(8) when
       receiving a protocol request of "open for execution" from a Windows
       client. With Samba 3.6 and older, the execution right in the ACL
       was not checked, so a client could execute a file even if it did
       not have execute rights on the file. In Samba 4.0, this has been
       fixed, so that by default, i.e. when this parameter is set to
       "False", "open for execution" is now denied when execution
       permissions are not present.

       If this parameter is set to "True", Samba does not check execute
       permissions on "open for execution", thus re-establishing the
       behaviour of Samba 3.6. This can be useful to smoothen upgrades
       from older Samba versions to 4.0 and newer. This setting is not
       meant to be used as a permanent setting, but as a temporary relief:
       It is recommended to fix the permissions in the ACLs and reset this
       parameter to the default after a certain transition period.

Note: if acl allow execute always = false doesn't work, try acl allow execute always = no.

guest ok (S)

       If this parameter is yes for a service, then no password is
       required to connect to the service. Privileges will be those of the
       guest account.

       This parameter nullifies the benefits of setting restrict anonymous
       = 2

       See the section below on security for more information about this
       option.

writeable (S)

       Inverted synonym for read only.

read only (S)

       An inverted synonym is writeable.

       If this parameter is yes, then users of a service may not create or
       modify files in the service's directory.

       Note that a printable service (printable = yes) will ALWAYS allow
       writing to the directory (user privileges permitting), but only via
       spooling operations.

available (S)

       This parameter lets you "turn off" a service. If available = no,
       then ALL attempts to connect to the service will fail. Such
       failures are logged.

browseable (S)

       This controls whether this share is seen in the list of available
       shares in a net view and in the browse list.

printable (S)

       If this parameter is yes, then clients may open, write to and
       submit spool files on the directory specified for the service.

       Note that a printable service will ALWAYS allow writing to the
       service path (user privileges permitting) via the spooling of print
       data. The read only parameter controls only non-printing access to
       the resource.

locking (S)

       This controls whether or not locking will be performed by the
       server in response to lock requests from the client.

       If locking = no, all lock and unlock requests will appear to
       succeed and all lock queries will report that the file in question
       is available for locking.

       If locking = yes, real locking will be performed by the server.

       This option may be useful for read-only filesystems which may not
       need locking (such as CDROM drives), although setting this
       parameter of no is not really recommended even in this case.

       Be careful about disabling locking either globally or in a specific
       service, as lack of locking may result in data corruption. You
       should never need to set this parameter.