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https-dns-proxy

https_dns_proxy is a light-weight DNS<-->HTTPS, non-caching translation proxy for the RFC 8484 DNS-over-HTTPS standard. It receives regular (UDP) DNS requests and issues them via DoH.

Google's DNS-over-HTTPS service is default, but Cloudflare's service also works with trivial commandline flag changes.

Using Google

# ./https_dns_proxy -u nobody -g nogroup -d -b 8.8.8.8,8.8.4.4 \
    -r "https://dns.google/dns-query"

Using Cloudflare

# ./https_dns_proxy -u nobody -g nogroup -d -b 1.1.1.1,1.0.0.1 \
    -r "https://cloudflare-dns.com/dns-query"

Why?

Using DNS over HTTPS makes eavesdropping and spoofing of DNS traffic between you and the HTTPS DNS provider (Google/Cloudflare) much less likely. This of course only makes sense if you trust your DoH provider.

Features

  • Tiny Size (<30kiB).
  • Uses curl for HTTP/2 and pipelining, keeping resolve latencies extremely low.
  • Single-threaded, non-blocking select() server for use on resource-starved embedded systems.
  • Designed to sit in front of dnsmasq or similar caching resolver for transparent use.

Build

Depends on c-ares (>=1.11.0), libcurl (>=7.64.0), libev (>=4.25).

On Debian-derived systems those are libc-ares-dev, libcurl4-{openssl,nss,gnutls}-dev and libev-dev respectively. On Redhat-derived systems those are c-ares-devel, libcurl-devel and libev-devel.

On MacOS, you may run into issues with curl headers. Others have had success when first installing curl with brew.

brew install curl --with-openssl --with-c-ares --with-libssh2 --with-nghttp2 --with-gssapi --with-libmetalink
brew link curl --force

On Ubuntu

apt-get install cmake libc-ares-dev libcurl4-openssl-dev libev-dev build-essential

If all pre-requisites are met, you should be able to build with:

$ cmake .
$ make

Build with HTTP/3 support

  • If system libcurl supports it by default nothing else has to be done

  • If a custom build of libcurl supports HTTP/3 which is installed in a different location, that can be set when running cmake:

$ cmake -D CUSTOM_LIBCURL_INSTALL_PATH=/absolute/path/to/custom/libcurl/install .
  • Just to test HTTP/3 support for development purpose, simply run the following command and wait for a long time:
$ ./development_build_with_http3.sh

INSTALL

Install built program

This method work fine on most Linux operating system, which uses systemd.
Like: Raspberry Pi OS / Raspbian, Debian, Ubuntu, etc.

To install the program binary, systemd service and munin plugin (if munin is pre-installed), simply execute the following after build:

$ sudo make install

To activate munin plugin, restart munin services:

$ sudo systemctl restart munin munin-node

To overwrite default service options use:

$ sudo systemctl edit https_dns_proxy.service

And re-define ExecStart with desired options:

[Service]
ExecStart=
ExecStart=/usr/local/bin/https_dns_proxy \
  -u nobody -g nogroup -r https://doh.opendns.com/dns-query

OpenWRT package install

There is a package in the OpenWRT packages repository as well. You can install as follows:

root@OpenWrt:~# opkg update
root@OpenWrt:~# opkg install https-dns-proxy
root@OpenWrt:~# /etc/init.d/https-dns-proxy enable
root@OpenWrt:~# /etc/init.d/https-dns-proxy start

OpenWrt's init script automatically updates the dnsmasq config to include only DoH servers on its start and restores old settings on stop. Additional information on OpenWrt-specific configuration is available at the README.

If you are using any other resolver on your router you will need to manually replace any previously used servers with entries like:

127.0.0.1#5053

You may also want to prevent your resolver from using /etc/resolv.conf DNS servers, leaving only our proxy server.

There's also a WebUI package available for OpenWrt (luci-app-https-dns-proxy) which contains the list of supported and tested DoH providers.

archlinux package install

There is also an externally maintained AUR package for latest git version. You can install as follows:

user@arch:~# yay -S https-dns-proxy-git

Docker install

There is also an externally maintained Docker image for latest git version. Documentation, Dockerfile, and entrypoint script can be viewed on GitHub. An example run:

### points towards AdGuard DNS, only use IPv4, increase logging ###

docker run --name "https-dns-proxy" -p 5053:5053/udp  \
  -e DNS_SERVERS="94.140.14.14,94.140.15.15" \
  -e RESOLVER_URL="https://dns.adguard.com/dns-query" \
  -d bwmoran/https-dns-proxy \
  -4 -vvv

Usage

Just run it as a daemon and point traffic at it. Commandline flags are:

Usage: ./https_dns_proxy [-a <listen_addr>] [-p <listen_port>]
        [-d] [-u <user>] [-g <group>] [-b <dns_servers>]
        [-i <polling_interval>] [-4] [-r <resolver_url>]
        [-t <proxy_server>] [-l <logfile>] [-c <dscp_codepoint>]
        [-x] [-q] [-s <statistic_interval>] [-v]+ [-V] [-h]

  -a listen_addr         Local IPv4/v6 address to bind to. (127.0.0.1)
  -p listen_port         Local port to bind to. (5053)
  -d                     Daemonize.
  -u user                Optional user to drop to if launched as root.
  -g group               Optional group to drop to if launched as root.
  -b dns_servers         Comma-separated IPv4/v6 addresses and ports (addr:port)
                         of DNS servers to resolve resolver host (e.g. dns.google).
                         When specifying a port for IPv6, enclose the address in [].
                         (8.8.8.8,1.1.1.1,8.8.4.4,1.0.0.1,145.100.185.15,145.100.185.16,185.49.141.37)
  -i polling_interval    Optional polling interval of DNS servers.
                         (Default: 120, Min: 5, Max: 3600)
  -4                     Force IPv4 hostnames for DNS resolvers non IPv6 networks.
  -r resolver_url        The HTTPS path to the resolver URL. Default: https://dns.google/dns-query
  -t proxy_server        Optional HTTP proxy. e.g. socks5://127.0.0.1:1080
                         Remote name resolution will be used if the protocol
                         supports it (http, https, socks4a, socks5h), otherwise
                         initial DNS resolution will still be done via the
                         bootstrap DNS servers.
  -l logfile             Path to file to log to. ("-")
  -c dscp_codepoint      Optional DSCP codepoint[0-63] to set on upstream DNS server
                         connections.
  -x                     Use HTTP/1.1 instead of HTTP/2. Useful with broken
                         or limited builds of libcurl. (false)
  -q                     Use HTTP/3 (QUIC) only. (false)
  -s statistic_interval  Optional statistic printout interval.
                         (Default: 0, Disabled: 0, Min: 1, Max: 3600)
  -v                     Increase logging verbosity. (Default: error)
                         Levels: fatal, stats, error, warning, info, debug
                         Request issues are logged on warning level.
  -V                     Print version and exit.
  -h                     Print help and exit.

Testing

Functional tests can be executed using Robot Framework.

dig and valgrind commands are expected to be available.

pip3 install robotframework
python3 -m robot.run tests/robot/functional_tests.robot

TODO

  • Add some tests.
  • Improve IPv6 handling and add automatic fallback to IPv4

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