# doh-client
`doh-client` is a DNS over HTTPS client, which opens a local UDP (DNS) port and forwards all DNS queries to a remote
HTTP/2.0 server. By default, the client will connect to the Cloudflare DNS service. It uses [Tokio](https://tokio.rs/)
for all asynchronous IO operations and [Rustls](https://github.com/ctz/rustls) to connect to the HTTPS server.
The client uses a private HTTP cache (see [RFC 7234](https://tools.ietf.org/html/rfc7234#section-5.2)) to increase the
performance if the `--cache-size` is not zero.
[](https://travis-ci.org/LinkTed/doh-client)
[](https://deps.rs/repo/github/linkted/doh-client)
[](https://crates.io/crates/doh-client)
[](https://opensource.org/licenses/BSD-3-Clause)
## Getting Started
`doh-client` is written in [Rust](https://www.rust-lang.org/). To build it you need the
[Rust](https://www.rust-lang.org/) compiler and build system `cargo`.
### Build
```
$ cargo build
```
Or to build it as a release build:
```
$ cargo build --release
```
On default, the feature socks5 proxy([RFC 1928](https://tools.ietf.org/html/rfc1928)) is enabled.
To build the client without the feature use the following command:
```
$ cargo build --no-default-features
```
### Run
To run the binary, you need one positional argument (see [Usage](#Usage)).
```
$ ./doh-client /path/to/the/ca/file.pem
```
For example, if you use [Arch Linux](https://www.archlinux.org/) then the following command uses the system cert store:
```
# ./doh-client /etc/ca-certificates/extracted/tls-ca-bundle.pem
```
#### Linux (`systemd`)
To run the `doh-client` as a daemon and without `root` under Linux with `systemd` as init system follow the instructions.
This example will connect to the Cloudflare DNS service.
1. Build the binary (see [Build](#Build)).
2. Copy the binary to `/usr/bin` as `root`:
```
# cp target/release/doh-client /usr/bin/
```
3. Copy the config files to `/etc/systemd/system/` as `root`:
```
# cp doh-client.service doh-client.socket /etc/systemd/system
```
If the location of the binary is different from above then change the path in `doh-client.service` under `ExecStart`.
In the config file `doh-client.service` the path of the CA file is set to
`/etc/ca-certificates/extracted/tls-ca-bundle.pem`, adjust the path before going further (The path should be correct
if you use [Arch Linux](https://www.archlinux.org/)).
4. Reload `systemd` manager configuration:
```
# systemctl daemon-reload
```
5. Enable the `doh-client` as a daemon:
```
# systemctl enable doh-client
```
6. Reboot the system or start the daemon manually:
```
# systemctl start doh-client
```
7. Adjust the `/etc/resolv.conf` by adding the following line:
```
nameserver 127.0.0.1
```
##### Additional
If [AppArmor](https://gitlab.com/apparmor/apparmor/wikis/home/) is used then the `doh-client` profile from the
repository can be applied to [AppArmor](https://gitlab.com/apparmor/apparmor/wikis/home/).
1. Copy the profile file `usr.bin.doh-client` to `/etc/apparmor.d/` as `root`:
```
# cp usr.bin.doh-client /etc/apparmor.d/
```
If the location of the CA file is different from `/etc/ca-certificates/extracted/tls-ca-bundle.pem` then change the
path in `usr.bin.doh-client`.
2. Reboot the system or reload all profiles:
```
# systemctl restart apparmor.service
```
##### Arch Linux
There is an [AUR](https://aur.archlinux.org/packages/doh-client) package available.
#### Mac OS (`launchd`)
To run the `doh-client` as a daemon and without `root` under Mac OS with `launchd` as init system.
This example will connect to the Cloudflare DNS service.
1. Build the binary (see [Build](#Build)).
2. Copy the binary to `/usr/local/bin` as `root`:
```
# cp target/release/doh-client /usr/local/bin/
```
3. Copy the `launchd` config files to `/Library/LaunchDaemons/` as `root`:
```
# cp com.doh-client.daemon.plist /Library/LaunchDaemons
```
If the location of the binary is different from above then change the path in `com.doh-client.daemon.plist` under
`ProgramArguments`. In the config file `com.doh-client.daemon.plist` the path of the CA file is set to
`/usr/local/share/doh-client/DigiCert_Global_Root_CA.pem`, download the pem file under the following
[link](https://dl.cacerts.digicert.com/DigiCertGlobalRootCA.crt). Before copy the pem file to
`/usr/local/share/doh-client/`, make the directory `doh-client` with `mkdir`.
4. Load and start the config file as follow:
```
# launchctl load -w /Library/LaunchDaemons/com.doh-client.daemon.plist
```
5. Adjust the `/etc/resolv.conf` by adding the following line:
```
nameserver 127.0.0.1
```
## Usage
`doh-client` has one required positional argument, `CAFILE` which sets the path to a pem file, which contains the
trusted CA certificates.
```
$ ./doh-client --help
DNS over HTTPS client 2.2.0
link.ted@mailbox.org
Open a local UDP (DNS) port and forward DNS queries to a remote HTTP/2.0 server.
By default, the client will connect to the Cloudflare DNS service.
This binary uses the env_logger as logger implementations. See https://github.com/sebasmagri/env_logger/
USAGE:
doh-client [FLAGS] [OPTIONS] <CAFILE>
FLAGS:
--cache-fallback Use expired cache entries if no response is received from the server
-g, --get Use the GET method for the HTTP/2.0 request
-h, --help Prints help information
--listen-activation Use file descriptor 3 under Unix as UDP socket or launch_activate_socket() under Mac OS
-V, --version Prints version information
OPTIONS:
-c, --cache-size <UNSIGNED LONG> The size of the private HTTP cache
If the size is 0 then the private HTTP cache is not used (ignores cache-control)
[default: 1024]
-d, --domain <Domain> The domain name of the remote server [default: cloudflare-dns.com]
-l, --listen-addr <Addr> Listen address [default: 127.0.0.1:53]
-p, --path <STRING> The path of the URI [default: dns-query]
-r, --remote-host <Addr/Name> Remote address/hostname to the DOH server (If a hostname is used then another
DNS server has to be configured) [default: 1.1.1.1:443]
--retries <UNSIGNED INT> The number of retries to connect to the remote server [default: 3]
--socks5 <URL> Socks5 proxy URL
(example: socks5://user:password@example.com or socks5h://example.com)
-t, --timeout <UNSIGNED LONG> The time in seconds after that the connection would be closed if no response is
received from the server [default: 2]
ARGS:
<CAFILE> The path to the pem file, which contains the trusted CA certificates
```
## Cache performance
To demonstrate that the private HTTP cache (see [RFC 7234](https://tools.ietf.org/html/rfc7234#section-5.2)) increases
the performance of the client, make a request to `github.com`:
```
$ dig github.com +nocookie
; <<>> DiG 9.13.5 <<>> github.com +nocookie
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19752
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;github.com. IN A
;; ANSWER SECTION:
github.com. 8 IN A 192.30.253.112
github.com. 8 IN A 192.30.253.113
;; Query time: 35 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sa Jan 05 20:00:20 CET 2019
;; MSG SIZE rcvd: 71
```
The query took 35 milliseconds. If the request is made again (**quick**, before the response is removed from the cache):
```
$ dig github.com +nocookie
; <<>> DiG 9.13.5 <<>> github.com +nocookie
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52653
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;github.com. IN A
;; ANSWER SECTION:
github.com. 8 IN A 192.30.253.112
github.com. 8 IN A 192.30.253.113
;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sa Jan 05 20:00:21 CET 2019
;; MSG SIZE rcvd: 71
```
Now, the query took 0 milliseconds, because it was cached.
How long is a DNS request and response in the cache?
1. If `control-cache: max-age=XXX` is present in the HTTP header then this value is used. For example, if the server responds with a
`control-cache: max-age=100` then the DNS request and response is in the cache for 100 seconds. After 100 seconds,
the client will forward the request to the server again.
2. If `control-cache: max-age=XXX` is not present then the smallest TTL in the answer section of the DNS response is used.
3. If there is no resource records in the answer section then authority section of the DNS response is used.
4. If there is no resource records in the authority section then additional section of the DNS response is used.