4

I'm using Korora 23, which is based on Fedora 23.

Whenever I type a command in bash that's not available, bash asks if I want to install a package to provide the command. Problem is, if I type y, it installs package without asking for any password. It's not that sudo doesn't ask for password. Password prompt happens without fail when using sudo dnf install <package>, but not when bash tries to do that on its own. Where should I start looking for problems? enter image description here

Bash reference:

[12:06 mayank ~]$ nano
bash: nano: command not found...
Install package 'nano' to provide command 'nano'? [N/y] y


 * Waiting in queue... 
 * Loading list of packages.... 
The following packages have to be installed:
 nano-2.4.2-3.fc23.x86_64   A small text editor
Proceed with changes? [N/y] y


 * Waiting in queue... 
 * Waiting for authentication... 
 * Waiting in queue... 
 * Downloading packages... 
 * Requesting data... 
 * Testing changes... 
 * Installing packages... 
Received SIGHUP or SIGTERM

[12:06 mayank ~]$ sudo dnf remove nano
[sudo] password for mayank: 
Dependencies resolved.
===================================================================================================================================================================================================================
 Package                                        Arch                                             Version                                                  Repository                                          Size
===================================================================================================================================================================================================================
Removing:
 nano                                           x86_64                                           2.4.2-3.fc23                                             @updates                                           1.9 M

Transaction Summary
===================================================================================================================================================================================================================
Remove  1 Package

Installed size: 1.9 M
Is this ok [y/N]: y
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Erasing     : nano-2.4.2-3.fc23.x86_64                                                                                                                                                                       1/1 
  Verifying   : nano-2.4.2-3.fc23.x86_64                                                                                                                                                                       1/1 

Removed:
  nano.x86_64 2.4.2-3.fc23                                                                                                                                                                                         

Complete!

command_not_found_handle:

[12:49 mayank ~]$ type command_not_found_handle
command_not_found_handle is a function
command_not_found_handle () 
{ 
    local runcnf=1;
    local retval=127;
    [[ $- =~ i ]] || runcnf=0;
    [[ ! -S /var/run/dbus/system_bus_socket ]] && runcnf=0;
    [[ ! -x '/usr/libexec/packagekitd' ]] && runcnf=0;
    [[ -n ${COMP_CWORD-} ]] && runcnf=0;
    if [ $runcnf -eq 1 ]; then
        '/usr/libexec/pk-command-not-found' "$@";
        retval=$?;
    else
        if [[ -n "${BASH_VERSION-}" ]]; then
            printf 'bash: %scommand not found\n' "${1:+$1: }" 1>&2;
        fi;
    fi;
    return $retval
}

Sudoers file:

## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.
##
## Examples are provided at the bottom of the file for collections
## of related commands, which can then be delegated out to particular
## users or groups.
## 
## This file must be edited with the 'visudo' command.

## Host Aliases
## Groups of machines. You may prefer to use hostnames (perhaps using 
## wildcards for entire domains) or IP addresses instead.
# Host_Alias     FILESERVERS = fs1, fs2
# Host_Alias     MAILSERVERS = smtp, smtp2

## User Aliases
## These aren't often necessary, as you can use regular groups
## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname 
## rather than USERALIAS
# User_Alias ADMINS = jsmith, mikem


## Command Aliases
## These are groups of related commands...

## Networking
# Cmnd_Alias NETWORKING = /sbin/route, /sbin/ifconfig, /bin/ping, /sbin/dhclient, /usr/bin/net, /sbin/iptables, /usr/bin/rfcomm, /usr/bin/wvdial, /sbin/iwconfig, /sbin/mii-tool

## Installation and management of software
# Cmnd_Alias SOFTWARE = /bin/rpm, /usr/bin/up2date, /usr/bin/yum

## Services
# Cmnd_Alias SERVICES = /sbin/service, /sbin/chkconfig

## Updating the locate database
# Cmnd_Alias LOCATE = /usr/bin/updatedb

## Storage
# Cmnd_Alias STORAGE = /sbin/fdisk, /sbin/sfdisk, /sbin/parted, /sbin/partprobe, /bin/mount, /bin/umount

## Delegating permissions
# Cmnd_Alias DELEGATING = /usr/sbin/visudo, /bin/chown, /bin/chmod, /bin/chgrp 

## Processes
# Cmnd_Alias PROCESSES = /bin/nice, /bin/kill, /usr/bin/kill, /usr/bin/killall

## Drivers
# Cmnd_Alias DRIVERS = /sbin/modprobe

# Defaults specification

#
# Refuse to run if unable to disable echo on the tty.
#
Defaults   !visiblepw

Defaults    env_reset
Defaults    env_keep =  "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR LS_COLORS"
Defaults    env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE"
Defaults    env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES"
Defaults    env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE"
Defaults    env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY"

Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin

## Next comes the main part: which users can run what software on 
## which machines (the sudoers file can be shared between multiple
## systems).
## Syntax:
##
##  user    MACHINE=COMMANDS
##
## The COMMANDS section may have other options added to it.
##
## Allow root to run any commands anywhere 
root    ALL=(ALL)   ALL

## Allows members of the 'sys' group to run networking, software, 
## service management apps and more.
# %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS

## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)   ALL

## Same thing without a password
# %wheel    ALL=(ALL)   NOPASSWD: ALL

## Allows members of the users group to mount and unmount the 
## cdrom as root
# %users  ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom

## Allows members of the users group to shutdown this system
# %users  localhost=/sbin/shutdown -h now

## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment)
#includedir /etc/sudoers.d
#ALL ALL=(ALL) NOPASSWD:/usr/local/Mobile_Partner/Mobile_Partner/MobilePartner.sh
%admin ALL=(ALL)ALL
  • your sudoers file or type command_not_found_handle – llua Nov 25 '16 at 7:06
  • I've added sudoers file and output for type command_not_found_handle – Mayank Verma Nov 25 '16 at 7:44
  • I would imagine the command /usr/libexec/pk-command-not-found is what you are interested in.. – llua Nov 25 '16 at 8:12
5

According to RH# 1225788, this is intended behaviour:

It's by design that admin users (in the wheel group) can install software without having to enter a password. See https://pagure.io/fesco/issue/1115#comment-27002 and the discussion in the ticket for background information.

(URL edited to match exact comment.)

  • Then how is it that dnf requires password? – Mayank Verma Nov 25 '16 at 9:18
  • dnf doesn't require (prompt for) passwords, sudo does. And as per the above mentioned polkit policy, "admin users" are allowed to install (some) software - no passwords involved here. – ckujau Nov 26 '16 at 2:46
2

There was a file called /usr/share/polkit-1/rules.d/org.freedesktop.packagekit.rules which had the following content:

polkit.addRule(function(action, subject) {
    if (action.id == "org.freedesktop.packagekit.package-install" &&
        subject.active == true && subject.local == true &&
        subject.isInGroup("wheel")) {
            return polkit.Result.YES;
    }
});

Commenting the lines solved the problem. Now, whenever bash suggests me a package, it shows a dialog box during authentication phase.

  • The next update of polkit may overwrite this file, be sure to to adjust this file again if you really want to go that way. – ckujau Nov 26 '16 at 2:44
1

Both answers provide partially explain that it works and it is ok, but miss the reasons why.

Let me explain as in similar question on SU:

  • You are granted the access by the PolicyKit, not by sudo.
  • The CommandNotFound is part of PackageKit, not of dnf
  • It is not a problem but a feature

Why? The PackageKit application is a limited application, which allows you installing and updating packages from the graphical user interface. But only if:

  • the packages from already added repositories (therefore not any particular package from the Internet).
  • and your user is active, local and in the group wheel -- the Administrator check box when setting up new users.

The installation is therefore not unauthorized and even if someone would install something for you, it would be from the official repositories, which should not contain anything harmful.

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