Allow unprivileged users to start fdns.
First install rust, then execute the following commands.
git clone https://github.com/rusty-snake/fdns4users.git
cd fdns4users
cargo build --release
sudo install -D -m 4755 -o root -g root target/release/fdns4users /usr/local/bin/fdns4users
🚨 This adds a new suid-executable to your system. 🚨
You can now start using it, here an example.
fdns4users --proxy-addr=127.70.74.68 --whitelist=debian.org &
firejail --dns=127.70.74.68 wget "https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-10.6.0-amd64-netinst.iso"
--proxy-addr must be the first argument and start with 127.70.74..
Instead of an own suid-exeutable you can use polkit or sudo.
Attention:
- Only edit sudoers if you know what you do!
- Read the relevant parts of the manpage!
- Always use
visudo! - Keep a root-shell open to undo mistakes, so you won't get locked out.
Allow the user john to start fdns --proxy-addr=127.70.74.<digit between 0 and 9> via sudo.
/etc/sudoers.d/40-fdns:
john ALL=(root) NOPASSWD: /usr/bin/fdns --proxy-addr=127.70.74.[0-9]
/etc/polkit-1/rules.d/40-fdns.rules:
polkit.addRule(function(action, subject) {
const USER = "john";
const PROGRAM = "/usr/bin/fdns";
const IP = "127\\.70\\.74\\.[0-9]{1,3}";
const PROXY_ADDR = `--proxy-addr=${IP}`;
const BLOCKLIST = `--blocklist=[A-Za-z0-9._-]+`;
const WHITELIST = `--whitelist=[A-Za-z0-9._-]+`;
const ZOM_BWLIST = `( ${WHITELIST}| ${BLOCKLIST})*`;
const RE = new RegExp(`^${PROGRAM} ${PROXY_ADDR}${ZOM_BWLIST}$`);
// Debugging: uncomment to see the final RegExp
//polkit.log(RE.toString());
if (action.id === "org.freedesktop.policykit.exec" &&
action.lookup("program") === PROGRAM &&
RE.test(action.lookup("command_line")) &&
subject.user === USER && subject.local && subject.active) {
return polkit.Result.YES;
}
});This allows the user john to start /usr/bin/fdns --proxy-addr=127.70.68.* with
--whitelist=example1.com, --whitelist=example2.com, --blocklist=example3.com ….
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