Name

dnscrypt-wrapper - A server-side dnscrypt proxy.

Table of Contents

• Description
• Installation
• Usage
  • Quick start
  • Running unauthenticated DNS and the dnscrypt service on the same port
  • Key rotation
• Chinese
• See also

Description

This is dnscrypt wrapper (server-side dnscrypt proxy), which helps to add dnscrypt support to any name resolver.

This software is modified from dnscrypt-proxy.

Installation

Install libsodium and libevent 2.1.1+ first.

On Linux:

$ ldconfig # if you install libsodium from source
$ git clone git://github.com/cofyc/dnscrypt-wrapper.git
$ cd dnscrypt-wrapper
$ make configure
$ ./configure
$ make install

On FreeBSD:

$ pkg install dnscrypt-wrapper

On OpenBSD:

$ pkg_add -r gmake autoconf
$ pkg_add -r libevent
$ git clone git://github.com/cofyc/dnscrypt-wrapper.git
$ cd dnscrypt-wrapper
$ gmake LDFLAGS='-L/usr/local/lib/' CFLAGS=-I/usr/local/include/

On MacOS:

$ brew install dnscrypt-wrapper

In Docker:

See https://github.com/jedisct1/dnscrypt-server-docker.

Usage

Quick Start

1. Generate the provider key pair:

$ dnscrypt-wrapper --gen-provider-keypair \
  --provider-name=2.dnscrypt-cert.<yourdomain> --ext-address=<external server ip>

If your server doesn't store logs, add --nolog and if it supports DNSSEC, add --dnssec.

This will create two files in the current directory: public.key and secret.key.

This is a long-term key pair that is never supposed to change unless the secret key is compromised. Make sure that secret.key is securely stored and backuped.

It will also print the stamp for dnscrypt-proxy version 2.x.

If you forgot to save your provider public key:

$ dnscrypt-wrapper --show-provider-publickey --provider-publickey-file <your-publickey-file>

This will print it out.

2. Generate a time-limited secret key, which will be used to encrypt and authenticate DNS queries. Also generate a certificate for it:

$ dnscrypt-wrapper --gen-crypt-keypair --crypt-secretkey-file=1.key
$ dnscrypt-wrapper --gen-cert-file --crypt-secretkey-file=1.key --provider-cert-file=1.cert \
                   --provider-publickey-file=public.key --provider-secretkey-file=secret.key

In this example, the time-limited secret key will be saved as 1.key and its related certificate as 1.cert in the current directory.

Time-limited secret keys and certificates can be updated at any time without requiring clients to update their configuration.

NOTE: By default, secret key expires in 1 day (24 hours) for safety. You can change it by adding --cert-file-expire-days=<your-expected-expiraiton-days>, but it's better to use short-term secret key and use key-rotation mechanism.

3. Run the program with a given key, a provider name and the most recent certificate:

$ dnscrypt-wrapper --resolver-address=8.8.8.8:53 --listen-address=0.0.0.0:443 \
                   --provider-name=2.dnscrypt-cert.<yourdomain> \
                   --crypt-secretkey-file=1.key --provider-cert-file=1.cert

The provider name can be anything; it doesn't have to be within an existing domain name. However, it has to start with 2.dnscrypt-cert., e.g. 2.dnscrypt-cert.example.com.

When the service is started with the --provider-cert-file switch, the proxy will automatically serve the certificate as a TXT record when a query for the provider name is received.

As an alternative, the TXT record can be served by a name server for an actual DNS zone you are authoritative for. In that scenario, the --provider-cert-file option is not required, and instructions for Unbound and TinyDNS are displayed by the program when generating a provider certificate.

You can get instructions later by running:

$ dnscrypt-wrapper --show-provider-publickey-dns-records
                   --provider-cert-file <path/to/your/provider_cert_file>

4. Run dnscrypt-proxy to check if it works:

$ dnscrypt-proxy --local-address=127.0.0.1:55 --resolver-address=127.0.0.1:443 \
                 --provider-name=2.dnscrypt-cert.<yourdomain> \
                 --provider-key=<provider_public_key>
$ dig -p 55 google.com @127.0.0.1

<provider_public_key> is public key generated by dnscrypt-wrapper --gen-provider-keypair, which looks like 4298:5F65:C295:DFAE:2BFB:20AD:5C47:F565:78EB:2404:EF83:198C:85DB:68F1:3E33:E952.

Optionally, add -d/--daemonize flag to run as a daemon.

Run dnscrypt-wrapper -h to view command line options.

Running unauthenticated DNS and the dnscrypt service on the same port

By default, and with the exception of records used for the certificates, only queries using the DNSCrypt protocol will be accepted.

If you want to run a service only accessible using DNSCrypt, this is what you want.

If you want to run a service accessible both with and without DNSCrypt, what you usually want is to keep the standard DNS port for the unauthenticated DNS service (53), and use a different port for DNSCrypt. You don't have to change anything for this either.

However, if you want to run both on the same port, maybe because only port 53 is reachable on your server, you can add the -U (--unauthenticated) switch to the command-line. This is not recommended.

Key rotation

Time-limited keys are bound to expire.

dnscrypt-proxy can check if the current key for a given server is not going to expire soon:

$ dnscrypt-proxy --resolver-address=127.0.0.1:443 \
                 --provider-name=2.dnscrypt-cert.<yourdomain> \
                 --provider-key=<provider_public_key> \
                 --test=10080

The --test option is followed by a "grace margin".

The command will immediately exit after verifying the certificate validity.

The exit code is 0 if a valid certificate can be used, 2 if no valid certificates can be used, 3 if a timeout occurred, and 4 if a currently valid certificate is going to expire before the margin.

The margin is always specified in minutes.

This can be used in a cron tab to trigger an alert before a key is going to expire.

In order to switch to a fresh new key:

First, create a new time-limited key (do not change the provider key!) and its certificate:

$ dnscrypt-wrapper --gen-crypt-keypair --crypt-secretkey-file=2.key
$ dnscrypt-wrapper --gen-cert-file --crypt-secretkey-file=2.key --provider-cert-file=2.cert \
                   --provider-publickey-file=public.key --provider-secretkey-file=secret.key \
                   --cert-file-expire-days=1

Second, Tell new users to use the new certificate but still accept the old key until all clients have loaded the new certificate:

$ dnscrypt-wrapper --resolver-address=8.8.8.8:53 --listen-address=0.0.0.0:443 \
                   --provider-name=2.dnscrypt-cert.<yourdomain> \
                   --crypt-secretkey-file=1.key,2.key --provider-cert-file=1.cert,2.cert

Note that both 1.key and 2.key have be specified, in order to accept both the previous and the current key.

Third, Clients automatically check for new certificates every hour. So, after one hour, the old certificate can be refused, by leaving only the new one in the configuration:

$ dnscrypt-wrapper --resolver-address=8.8.8.8:53 --listen-address=0.0.0.0:443 \
                   --provider-name=2.dnscrypt-cert.<yourdomain> \
                   --crypt-secretkey-file=2.key --provider-cert-file=2.cert

Please note that on Linux systems (kernel >= 3.9), multiples instances of dnscrypt-wrapper can run at the same time. Therefore, in order to switch to a new configuration, one can start a new daemon without killing the previous instance, and only kill the previous instance after the new one started.

This also allows upgrades with zero downtime.

Blocking

For servers willing to block specific domain names (ads, malware), the --blacklist-file parameter can be added. That blacklist file accepts patterns such as:

• example.com: blocks example.com as well as www.example.com
• *.example.com: identical, just more explicit
• *example*: blocks the example substring no matter where it appears
• ads.*: blocks the ads. prefix

Prefix and suffix lookups are fast and can scale to very large lists.

Chinese

• CentOS/Debian/Ubuntu 下编译 dnscrypt-wrapper: http://03k.org/centos-make-dnscrypt-wrapper.html
• dnscrypt-wrapper 使用方法: http://03k.org/dnscrypt-wrapper-usage.html

注：第三方文档可能未及时与最新版本同步，以 README.md 为准。

See also

• https://dnscrypt.info/
• https://github.com/jedisct1/dnscrypt-proxy
• https://github.com/cofyc/dnscrypt-wrapper