Re: [autofs] sshfs and autofs

[Stef Bon]

Marc Weber wrote:
The script I posted last let's still other users access your mounts
which is bad.
This script only queries the ssh-agents run by the uid specified in
mount options (uid=..)
It also uses sudo -u#uid to run ssfs causing a user mount.
So other causes can still cause the mount. But they can't access the
filesystem contents:

# ls -l /auto/mlin;
ls: cannot open directory /auto/mlin: Permission denied

#  ls -l /auto
ls: cannot access /auto/mlin: Permission denied
total 0
d????????? ? ? ? ?                ? mlin
  
Well the question marks mean that glibc cannot figure out the 
permissions. This means probably
that the mount has not been succesfull.

Whatever those question marks mean?


Updated script

    # setuid-wrappers for fusermount
    export 
PATH=/var/setuid-wrappers:${pkgs.coreutils}/bin:${pkgs.sshfsFuse}/bin:${pkgs.openssh}/bin:${pkgs.procps}/bin:${pkgs.lsof}/bin:${pkgs.gnused}/bin/:${pkgs.sudo}/bin
    pids=`pgrep ssh-agent`
    # get uid=nr from arguments
    uid=$(echo "$@"| sed -n 's...@.*uid=\([0123456789]\+\)....@\1@p')
    connect(){
      sudo=$1; shift
      $sudo sshfs -o ssh_command="ssh -o NumberOfPasswordPrompts=0" "$@" \
       && exit 0 || true
    }
    # Change ownership of mountpoint. Ownership will be overridden when mount 
suceeds.
    # Otherwise fusermount can't access it (?!)
    chown $uid "$2"
    chmod u+w "$2"
    for p in $pids; do
      res="$(lsof -p $p -a -U  -Fnu)"
      user_id=$(echo "$res"| sed -n 's/^u//p')
      if [ "$user_id" == "$uid" ]; then
        export SSH_AUTH_SOCK=$(echo "$res"| sed -n 's/^n//p')
        export SSH_AGENT_PID=$p
        echo "trying to connect using ssh-agent $p $SSH_AUTH_SOCK" 1>&2
        # by using sudo -u allow accessing mount by target user - Is there a 
better way to achieve this??
        connect "sudo -E -u#$user_id" "$@"
        echo -n " .. failed" 1>&2
      fi
    done
    unset SSH_AGENT_PID; unset SSH_AUTH_SOCK

    # no ssh-agent found or they all belong to different users..
    # Try again. Maybe there is a key without password ?
    # You should not be using this!
    connect "" "$@"
    exit 1

  
Does this work. I do not know anything about ssh agents.

I n my construction I'm using the following command:

sshfs "$unc_address" "$mountpoint" -o allow_other -o 
PasswordAuthentication='no' -o IdentityFile="$homedir/.ssh/id_dsa" -o 
UserKnownHostsFile="$homedir/.ssh/known_hosts" -o Compression='yes'

where unc_address is of the form %us...@192.168.0.1:

where user is like sbon (me) or root.
$homedir is the homedirectory of this user, and there has been a check 
the files like $homedir/.ssh/id_dsa are present.


This works. There is no construction to prevent other users to activate 
the mount.

I've created earlier a constrcution to mount ssh, and this was working 
with a mount.sshfs wrapper, which on his turn
called sshfs through above commands. This was working.

Now I'm working on a new construction which creates an seperate 
mountpoint for every user:

/mnt/mount.md5key/%USER%/mount

wher USER is again the user like sbon.

the directory /mnt/mount.md5key/%USER%
is owned by the user and has permissions 700, so no other user except 
root can access (and also activate) any mount.

Hope this helps.

Stef Bon



Can I make automount create those key directories with user permissions
as well so that other users can't even cause a mount?

Is there a better way to restrict acess to a user only compared to using
sudo?

Marc Weber

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