Dnscrypt-proxy (简体中文)

翻译状态：本文是 DNSCrypt 的翻译。上次翻译日期：2018-06-30。如果英文版本有所更改，则您可以帮助同步翻译。

dnscrypt-proxy 可以加密和认证用户和 DNS 解析服务器之间的数据传输，支持 DNS over HTTPS 和 DNSCrypt，可以避免中间人攻击和窃听。dnscrypt-proxy 兼容 DNSSEC。

安装

安装 软件包 dnscrypt-proxy。

配置

启动

服务有两种启动方式，但是只能二选一：

• 启用 .service

注意： 必须指定 listen_addresses (即在配置文件中写好 listen_addresses = ['127.0.0.1:53', '[::1]:53'])

• 启用 .socket

注意： 必须留空 listen_addresses (即 listen_addresses = [ ])，systemd 会自己配置好 socket

选择解析服务器

By leaving server_names commented out in the configuration file /etc/dnscrypt-proxy/dnscrypt-proxy.toml, dnscrypt-proxy will choose the fastest server from the sources already configured under [sources] [1]. The lists will be downloaded, verified, and automatically updated. [2]. Thus, configuring a specific set of servers is optional.

To manually set which server is used, edit /etc/dnscrypt-proxy/dnscrypt-proxy.toml and uncomment the server_names variable, selecting one or more of the servers. For example, to use Cloudflare's servers:

server_names = ['cloudflare', 'cloudflare-ipv6']

A full list of resolvers is located at the upstream page or Github. If dnscrypt-proxy has run successfully on the system before, /var/cache/dnscrypt-proxy/public-resolvers.md will also contain a list. Look at the description for servers note which validate DNSSEC, do not log, and are uncensored. These requirements can be configured globally with the require_dnssec, require_nolog, require_nofilter options.

禁用其他占用53端口的服务

提示： 如果使用 #Unbound 提供本地 DNS 缓存，请跳过这一节，因为 unbound 默认监听 53。

查看占用 53 端口的服务：

 $ ss -lp 'sport = :domain'

如果输出除了表头还有其他内容，你就需要禁用占用53端口的那些服务，比如 systemd-resolved.service 和其他网络管理器包含的类似服务。把它们全部干掉，直到上面的命令的输出只剩这个样子：

 Netid               State                 Recv-Q                Send-Q                     Local Address:Port                                   Peer Address:Port

修改 resolv.conf

修改 resolv.conf，把现有的nameserver全部清掉，添一行指向 localhost 的地址（一般是 127.0.0.1）的nameserver；并增添一行 options [3]。示例如下：

nameserver ::1
nameserver 127.0.0.1
options edns0 single-request-reopen

其他程序可能会修改 resolv.conf，详见：resolv.conf#Overwriting of /etc/resolv.conf。

启动 systemd 服务

根据上面你选择的配置来 start/enable dnscrypt-proxy.service 或者 dnscrypt-proxy.socket

技巧

本地 DNS 缓存配置

提示： dnscrypt can cache entries without relying on another program. This feature is enabled by default with the line cache = true in your dnscrypt configuration file

It is recommended to run DNSCrypt as a forwarder for a local DNS cache if not using dnscrypt's cache feature; otherwise, every single query will make a round-trip to the upstream resolver. Any local DNS caching program should work. In addition to setting up dnscrypt-proxy, you must setup your local DNS cache program.

修改端口

In order to forward queries from a local DNS cache, dnscrypt-proxy should listen on a port different from the default 53, since the DNS cache itself needs to listen on 53 and query dnscrypt-proxy on a different port. Port number 53000 is used as an example in this section. In this example, the port number is larger than 1024 so dnscrypt-proxy is not required to be run by root.

There are two methods for changing the default port:

Socket method

Edit dnscrypt-proxy.socket with the following contents:

[Socket]
ListenStream=
ListenDatagram=
ListenStream=127.0.0.1:53000
ListenDatagram=127.0.0.1:53000

When queries are forwarded from the local DNS cache to 53000, dnscrypt-proxy.socket will start dnscrypt-proxy.service.

Service method

Edit the listen_addresses option in /etc/dnscrypt-proxy/dnscrypt-proxy.toml with the following:

listen_addresses = ['127.0.0.1:53000', '[::1]:53000']

本地 DNS 缓存配置举例

The following configurations should work with dnscrypt-proxy and assume that it is listening on port 53000.

Unbound

Configure Unbound to your liking (in particular, see Unbound#Local DNS server) and add the following lines to the end of the server section in /etc/unbound/unbound.conf:

  do-not-query-localhost: no
forward-zone:
  name: "."
  forward-addr: 127.0.0.1@53000

提示： If you are setting up a server, add interface: 0.0.0.0@53 and access-control: your-network/subnet-mask allow inside the server: section so that the other computers can connect to the server. A client must be configured with nameserver address-of-your-server in /etc/resolv.conf.

Restart unbound.service to apply the changes.

dnsmasq

Configure dnsmasq as a local DNS cache. The basic configuration to work with DNSCrypt:

/etc/dnsmasq.conf

no-resolv
server=127.0.0.1#53000
listen-address=127.0.0.1

If you configured DNSCrypt to use a resolver with enabled DNSSEC validation, make sure to enable it also in dnsmasq:

/etc/dnsmasq.conf

proxy-dnssec

Restart dnsmasq.service to apply the changes.

pdnsd

Install pdnsd. A basic configuration to work with DNSCrypt is:

/etc/pdnsd.conf

global {
    perm_cache = 1024;
    cache_dir = "/var/cache/pdnsd";
    run_as = "pdnsd";
    server_ip = 127.0.0.1;
    status_ctl = on;
    query_method = udp_tcp;
    min_ttl = 15m;       # Retain cached entries at least 15 minutes.
    max_ttl = 1w;        # One week.
    timeout = 10;        # Global timeout option (10 seconds).
    neg_domain_pol = on;
    udpbufsize = 1024;   # Upper limit on the size of UDP messages.
}

server {
    label = "dnscrypt-proxy";
    ip = 127.0.0.1;
    port = 53000;
    timeout = 4;
    proxy_only = on;
}

source {
    owner = localhost;
    file = "/etc/hosts";
}

Restart pdnsd.service to apply the changes.

沙盒隔离

Edit dnscrypt-proxy.service to include the following lines:

[Service]
CapabilityBoundingSet=CAP_IPC_LOCK CAP_SETGID CAP_SETUID CAP_NET_BIND_SERVICE
ProtectSystem=strict
ProtectHome=true
ProtectKernelTunables=true
ProtectKernelModules=true
ProtectControlGroups=true
PrivateTmp=true
PrivateDevices=true
MemoryDenyWriteExecute=true
NoNewPrivileges=true
RestrictRealtime=true
RestrictAddressFamilies=AF_INET AF_INET6
SystemCallArchitectures=native
SystemCallFilter=~@clock @cpu-emulation @debug @keyring @ipc @module @mount @obsolete @raw-io

See systemd.exec(5) and Systemd#Sandboxing application environments for more information. Additionally see upstream comments.

启用 EDNS0

Extension Mechanisms for DNS that, among other things, allows a client to specify how large a reply over UDP can be.

Add the following line to your /etc/resolv.conf:

options edns0

You may also wish to append the following to /etc/dnscrypt-proxy.conf:

EDNSPayloadSize <bytes>

Where <bytes> is a number, the default size being 1252, with values up to 4096 bytes being purportedly safe. A value below or equal to 512 bytes will disable this mechanism, unless a client sends a packet with an OPT section providing a payload size.

测试 EDNS0

Make use of the DNS Reply Size Test Server, use the drill command line tool to issue a TXT query for the name rs.dns-oarc.net:

$ drill rs.dns-oarc.net TXT

With EDNS0 supported, the "answer section" of the output should look similar to this:

rst.x3827.rs.dns-oarc.net.
rst.x4049.x3827.rs.dns-oarc.net.
rst.x4055.x4049.x3827.rs.dns-oarc.net.
"2a00:d880:3:1::a6c1:2e89 DNS reply size limit is at least 4055 bytes"
"2a00:d880:3:1::a6c1:2e89 sent EDNS buffer size 4096"