2009/174 VERY SHORT TIMEOUT smbfs mount permissions

[Jordan Brown]

I'm sponsoring the following for fast-track approval.  The need for this 
case came up at rather the last minute, and to maintain planned push 
schedules we need a very short timeout - I'm asking for 14:00 Pacific 
tomorrow, Friday March 13, the end of the business day on the East Coast 
where the engineer is.  Thank you for your indulgence.

1. Technical Description

    More restrictive default permissions on smbfs mounts (CR 6800703)

2. Details
     2.1 Background and motivation

     The Solaris CIFS Client [PSARC 2005/695] provides the ability to
     mount CIFS shares from Windows-compatible servers on Solaris.

     When you mount a remote file system using the CIFS client, you
     supply a username and password.  All access to the remote file
     system is done *as the mount owner*, not as the user making the
     current file system request.  (This is arguably a weakness in the
     design of smbfs, but fixing it is a large project.)  If you don't
     want other people accessing the remote server as you, you have to
     arrange that the permissions on the mount don't allow them to.

     As documented in mount_smbfs(1m), the existing permissions on the
     mount point (which, mind you, must be owned by the user doing the
     mount) are used as the defaults.  This could easily lead to a user
     being surprised that others may access the server as that user.
     This is also arguably not "secure by default".

     We propose to change the default "fileperms" to 0700.  per:
     CR 6800703 smbfs default permissions may lead to surprises
     The release binding is: Patch.

3. Interface table
     (no change)

4. Documentation

     The mount_smbfs(1m) man page will be updated by CR (TBD)
     Here is a summary of the nsmbrc(4) changes:

     Current text:

          dirperms=octaltriplet

              Specifies the permissions to be assigned  to  direc-
              tories. The value must be specified as an octal tri-
              plet, such as 755. The default value for the  direc-
              tory mode adds the execute permission.

              Note that these permissions have no relation to  the
              rights granted by the CIFS server.

          fileperms=octaltriplet

              Specifies the permissions to be assigned  to  files.
              The  value  must  be  specified as an octal triplet,
              such as 644. The default value for the file mode  is
              taken from the mount point and adds the read permis-
              sion.

              Note that these permissions have no relation to  the
              rights granted by the CIFS server.

    Proposed text:

          dirperms=octaltriplet

              Specifies the permissions to be assigned  to  direc-
              tories. The value must be specified as an octal tri-
              plet, such as 755. The default value for the  direc-
              tory mode is taken from the fileperms setting, with
	     execute permission added where fileperms has read.

              Note that these permissions have no relation to  the
              rights granted by the CIFS server.

          fileperms=octaltriplet

              Specifies the permissions to be assigned  to  files.
              The  value  must  be  specified as an octal triplet,
              such as 644. The default value is 700.

              Note that these permissions have no relation to  the
              rights granted by the CIFS server.


5. References

    http://sac.sfbay/PSARC/2005/695/
    http://docs.sun.com/app/docs/doc/819-2240/mount-smbfs-1m

6. Resources and Schedule

    n/a