There are some possibilities to grant access to the router (or to any PC/Server):
signature
instead of a password
(e.g. SSH with signature.authentication)If you ask for username/password, an attacker has to guess the combination. If you use an unencrypted connection, he could eavesdrop on you and obtain them.
If you use an encrypted connection, any eavesdropper would have to decrypt the packets first. This is always possible. How long it takes to decrypt the content, depends on the algorithm and key length you used.
Also, as long as an attacker has network access to the console, he can always run a brute-force attack to find out username and password. He does not have to do that himself: he can let his computer(s) do the guessing. To render this option improbable or even impossible you can:
root
root
If you have an external disk you may want to encrypt it.
logtrigger
.Example that adds a user called nicolaus:
opkg update opkg install shadow-useradd useradd nicolaus
Or add the user by hand (Take care that uid/gid (e.g.=1000) are not already in use!)
/etc/passwd: USER:x:1000:1000:GROUP:/mnt/usb:/bin/false /etc/group: GROUP:x:1000: /etc/shadow: USER:RANDOMSTUFWillBeUpdatedWithPasswd:16666:0:99999:7::: passwd USER
However, you can't ssh to this user yet. To enable ssh access, you should make a password for that user, create his home folder and most importantly indicate the shell of that user:
passwd nicolaus mkdir /home mkdir /home/nicolaus chown nicolaus /home/nicolaus vi /etc/passwd nicolaus:x:1000:1000:nicolaus:/home/nicolaus:/bin/ash
First, you should install sudo
:
opkg install sudo
Additionally, you must allow your desired user by manipulating '/etc/sudoers
' by tool visudo
. Now you can follow ONE of the methods below to choose how the user should be able to run commands as root
:
In this method any user can temporarily run commands as root only if he knows the root password. This way when the user runs a command with sudo
he should enter root's password instead of his password.
For enabling this method you should open the file '/etc/sudoers
' by entering the command
visudo
Then uncomment the 2 lines below in that file and then save
## Uncomment to allow any user to run sudo if they know the password ## of the user they are running the command as (root by default). Defaults targetpw # Ask for the password of the target user ALL ALL=(ALL) ALL # WARNING: only use this together with 'Defaults targetpw'
This method is more secure because you don't need to protect both root and privileged (sudoer) users to keep the whole system safe.
One usecase can be allowing remote ssh with password from WAN: For more security (still less than RSA key) you can only allow users other than root to ssh with their password (optionally on a custom port) from WAN. And for even more security you can request root's password after running sudo
. Therefor in this scenario a hacker should find 3 different strings user's username, user's password and root's password to get full access to the system. Even if the user's account get compromised, then the intruder still can't damage your system because he doesn't have root password yet.
In this method, after logging in by the desired user, when you enter sudo
you should enter the user's password again. The end result is similar to how you use sudo
in Ubuntu or other popular Linux disros, but this method doesn't utilize group 'sudo' for this purpose.
For enabling this method you should also enter the command
visudo
And then add a line allowing your user, under comment “## User privilege specification”:
## ## User privilege specification ## root ALL=(ALL) ALL nicolaus ALL=(ALL) ALL
This method is very similar to Method 2, except that it allows any member of group 'sudo' to use sudo
with their own password. This method is exactly the same one used in Ubuntu and other popular Linux distros to allow 'sudo
' access for a user.
For activating this method first you should allow group 'sudo' to use command sudo
by entering
visudo
And then uncomment the line below:
## Uncomment to allow members of group sudo to execute any command %sudo ALL=(ALL) ALL
Second you should create group 'sudo'. You can do it by manually editing '/etc/group
' but it's more standard to install and use tools for this purpose:
opkg install shadow-groupadd groupadd --system sudo
And finally add your current user to the group 'sudo'. You can directly append your user to '/etc/group
' but again it's better to use usermod
:
opkg install shadow-usermod usermod -a -G sudo nicolaus
This method is more convenient because you can simply allow sudo
access for any user you want, just by usermod -a -G sudo <USER>
but takes more space (for installing new packages) than method 2 which may be more suitable for systems with very limited space.
If you are using ppp in the default configuration with username and password in /etc/config/network
, then the unprivileged user can read it from pppd's command line (with e.g. ps w
). To prevent that, you can add “user <username>
” to /etc/ppp/options
and “<username> * <password>
” to /etc/ppp/{chap|pap}-secrets
and then remove the username / password options from uci configuration.
Of course /etc/ppp/{chap|pap}-secrets
should not be world readable:
chmod go-rw /etc/ppp/chap-secrets
For secure web access, OpenWrt can be accessed via HTTPS (TLS) instead of the unencrypted HTTP protocol. If HTTP is not secure enough for you, you can disable the existing (unencrypted) web access and either
opkg install luci-ssl
uci delete uhttpd.main.listen_http ; uci commit
OR Rebind to LAN only and redirect all http requests to https:
uci set uhttpd.main.listen_http=192.168.1.1:80 uci set uhttpd.main.listen_https='192.168.1.1:443' uci set uhttpd.main.redirect_https='1' uci commit
/etc/init.d/uhttpd restart
opkg remove px5g
Can mandatory client certificate checking be set up with uhttpd? → not possible with uhttpd
If you require remote SSH access, follow the hardening instructions on SSH mentioned above.