[Bug 1787353] Re: fstab setting "user" and mount.cifs "user=" conflict and trigger unexpected behavior

[ Christian Ehrhardt ]

Since this is probably documentation only I set prio to low

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https://bugs.launchpad.net/bugs/1787353

Title:
  fstab setting "user" and mount.cifs "user=" conflict and trigger
  unexpected behavior

Status in cifs-utils package in Ubuntu:
  Invalid

Bug description:
  
  My FSTAB so far had this entry
    //10.7.0.231/documents /mnt/nas/documents cifs user,noauto,user=paelzer,vers=3.0 0 0

  I found after a reboot (to free up of the crashes above) that I need to change this.
  I wondered why the logins won't work anymore until I realized it was trying to authenticate root@<NAS> which is wrong.

  So far it had correctly authenticated for user=paelzer.

    //10.7.0.231/documents /mnt/nas/documents cifs
  user,noauto,username=paelzer,vers=3.0 0 0

  man mount.cifs specifies
  username=arg|user=arg
  specifies the username to connect as. If this is not given, then the environment variable USER is used.Earlier  versions  of  mount.cifs also allowed one to specify the username in a user%password or workgroup/user or workgroup/user%password to allow the password and workgroup to be specified as part of the username. Support for those alternate username formats is now deprecated and should no longer  be used.  Users  should  use  the discrete password= and domain= to specify those values. While some versions of the cifs kernel module accept user= as an abbreviation for this option, its use can confuse the standard mount program into thinking that this is a non-superuser mount. It is  therefore  recommended to use the full username= option name.

  But it seems for me "user=" no more works.
  There was a recent security update for samba (server side), but not CIFS utils.
  The only component I'd know of in this chain that has changed was the kernel part of it.

  I tracked this down to the following:
  I had so far:
  $ grep documents /etc/fstab 
  //10.7.0.231/documents /mnt/nas/documents cifs user,noauto,user=paelzer,vers=3.0 0 0

  Of these "user" is of fstab that is supposed to allow everybody to mount.
  and "user=" is for cifs to set the user.

  It turns out that "user" + "user=" is equal to only setting "user" and the effective login is derived from the current user id.
  So a sudo gives me root and without sudo I have my user.

  Now that is worth a not in the man page, but not more.
  I initially thought the kernel update would be involved and this be part of bug 1787328, but it isn't this is "normal" behavior.

  My mind still is on that other bug with the kernel crash, I think for
  this aspect here we would open a bug/proposed change to the cifs man
  page to clarify? Other suggestions?

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