PR-DNSd - Passive-Recursive DNS Daemon

PR-DNSd – Passive-Recursive DNS Daemon

August 1, 2022 Comments Off

Passive-Recursive DNS daemon.

Quickstart

nameserver 127.0.0.1 | sudo tee /etc/resolv.conf dig google.com dig -x $(dig +short google.com)”>

go get github.com/korc/PR-DNSd
sudo setcap cap_net_bind_service,cap_sys_chroot=ep go/bin/PR-DNSd
go/bin/PR-DNSd -upstream 9.9.9.9:53 -listen 127.0.0.1:53
echo nameserver 127.0.0.1 | sudo tee /etc/resolv.conf
dig google.com
dig -x $(dig +short google.com)

If you can’t use setcap, you have to use -chroot "" and -listen :<high_port> options, or run as root.

Use cases

run as local host DNS service, to fix your netstat/tcpview/lsof etc. output
as enterprise-internal DNS server, to also be able to do meaningful EDR/IR and log analysis
as cloud service, to also collect Passive DNS data from non-enterprise (home, BYOD etc.) devices
- hint: you probably want to configure DDoS protection options
in cloud as DNS-over-TLS server, to additionally provide private DNS for supporting devices (ex: Android 9’s private DNS setting)
- ex: domain pattern based firewall/proxy configuration for mobile devices

Running as your own private server for Android9’s Private DNS settings

After appropriate setcap, run:

PR-DNSd -tlslisten :853 -cert YOUR_SERVER_CRT_KEY_PEM -upstream 1.1.1.1:53 -store pr-dnsd

Options

-cert string
    TCP-TLS listener certificate (required for tls listener)
-chroot string
    chroot to directory after start (default "/var/tmp")
-count int
    Count of replies allowed before debounce delay is applied (default 100)
-ctmout string
    Client timeout for upstream queries
-debounce string
    Required time duration between UDP replies to single IP to prevent DoS (default "200ms")
-key string
    TCP-TLS certificate key (default same as -cert value)
-listen string
    listen address (default ":53")
-silent
    Don't report normal data
-store string
    Store PTR data to specified file
-tlslisten string
    TCP-TLS listener address (default ":853")
-upstream string
    upstream DNS serv   er (tcp-tls:// prefix for DoT) (default "1.1.1.1:53")
    (with tls and chroot, ensure ca-certificates and resolv.conf in chroot are properly set up)