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forked from folbricht/routedns

DNS stub resolver, proxy and router with support for DoT and DoH

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BSD-3-Clause license
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cmd/routedns
cmd/routedns
 
 
doc
doc
 
 
testdata
testdata
 
 
LICENSE
LICENSE
 
 
README.md
README.md
 
 
blocklist.go
blocklist.go
 
 
blocklist_test.go
blocklist_test.go
 
 
dnsclient.go
dnsclient.go
 
 
dnsclient_test.go
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dnslistener.go
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doc.go
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dohclient.go
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dohclient_test.go
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dohlistener.go
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dohlistener_test.go
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dotclient.go
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dotclient_test.go
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dotlistener.go
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dotlistener_test.go
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errors.go
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example_test.go
example_test.go
 
 
failback.go
failback.go
 
 
failback_test.go
failback_test.go
 
 
failrotate.go
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failrotate_test.go
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go.mod
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go.sum
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listener.go
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logger.go
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padding.go
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padding_test.go
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pipeline.go
pipeline.go
 
 
query.go
query.go
 
 
replace.go
replace.go
 
 
replace_test.go
replace_test.go
 
 
resolver.go
resolver.go
 
 
resolver_test.go
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roundrobin.go
roundrobin.go
 
 
roundrobin_test.go
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router.go
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router_test.go
router_test.go
 
 
tls.go
tls.go
 
 

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RouteDNS - DNS stub resolver, proxy and router

GoDoc

RouteDNS acts as a stub resolver and proxy that offers flexible configuration options with a focus on providing privacy as well as resiliency. It supports several DNS protocols such as plain UDP and TCP, DNS-over-TLS and DNS-over-HTTPS as input and output. In addition it's possible to build complex configurations allowing routing of queries based on query name, type or source address as well as blocklists and name translation. Upstream resolvers can be grouped in various ways to provide failover, load-balancing, or performance.

Features:

  • Support for DNS-over-TLS (DoT, RFC7858), client and server
  • Support for DNS-over-HTTPS (DoH, RFC8484), client and server with HTTP2
  • Custom CAs and mutual-TLS
  • Support for plain DNS, UDP and TCP for incoming and outgoing requests
  • Connection reuse and pipelining queries for efficiency
  • Multiple failover and load-balancing algorithms
  • Custom blocklists
  • In-line query modification and translation
  • Routing of queries based on query type, query name, or client IP
  • EDNS0 query and response padding (RFC7830, RFC8467)
  • Support for bootstrap addresses to avoid the initial service name lookup
  • Written in Go - Platform independent

Installation

Get the binary, this will put it under $GOPATH/bin, ~/go/bin if $GOPATH is not set:

go get -u github.com/folbricht/routedns/cmd/routedns

Run it:

routedns config.toml

An example systemd service file is provided here

Example configuration files for a number of use-cases can be found here

Configuration

RouteDNS uses a config file in TOML format which is passed to the tool as argument in the command line. The configuration is broken up into sections, not all of which are necessary for simple uses.

The config file defines listeners which represent open ports and protocols on which incoming DNS queries are received. These queries are then forwarded to routers, groups or resolvers. Routers can redirect queries based on information in the query, while groups can be be used to perform failover between upstream resolvers, or to modify/block queries. A more complex configuration could look like this.

configuration

Resolvers

The [resolvers]-section is used to define and upstream resolvers and the protocol to use when using them. Each of the resolvers requires a unique identifier which may be reference in the following sections. Only defining the resolvers will not actually mean they are used. This section can contain unused upstream resolvers.

The following protocols are supportes:

  • udp - Plain (unencrypted) DNS over UDP
  • tcp - Plain (unencrypted) DNS over TCP
  • dot - DNS-over-TLS
  • doh - DNS-over-HTTP

The following example defines several well-known resolvers, one using DNS-over-TLS, one DNS-over-HTTP while the other two use plain DNS. A more extensive list of configurations for public DNS services can be found here.

[resolvers]

  [resolvers.cloudflare-dot]
  address = "1.1.1.1:853"
  protocol = "dot"

  [resolvers.cloudflare-doh]
  address = "https://1.1.1.1/dns-query{?dns}"
  protocol = "doh"

  [resolvers.google-udp-8-8-8-8]
  address = "8.8.8.8:53"
  protocol = "udp"

  [resolvers.google-udp-8-8-4-4]
  address = "8.8.4.4:53"
  protocol = "udp"

Secure resolvers (DoT and DoH) also support additional option to set the trusted CA certificates or even set client key and certificates. Certificate and key files need to be in PEM format. Specify ca to only trust a specific set of CAs. If not specified, the resolver will use the system trust store.

  [resolvers.cloudflare-dot-with-ca]
  address = "1.1.1.1:853"
  protocol = "dot"
  ca = "/path/to/DigiCertECCSecureServerCA.pem"

For full mutual TLS with a private DNS server that expects the client to present a certificate, the client-key and client-crt options can be used to specify the key and certificate files.

  [resolvers.my-mutual-tls]
  address = "myserver:853"
  protocol = "dot"
  ca = "/path/to/my-ca.pem"
  client-key = "/path/to/my-key.pem"
  client-crt = "/path/to/my-crt.pem"

Bootstrapping

When upstream services are configured using their hostnames, routedns will first have to resolve the hostname of the service before establishing a secure connection with it. There are a couple of potenial issues with this:

  • The initial lookup is using the OS' resolver which could be using plain unencrypted DNS. This may not be desirable or fail if no other DNS is available.
  • The service does not support querying it by IP directly and a hostname is needed. Google for example does not support DoH using https://8.8.8.8/dns-query. The endpoint has to be configured as https://dns.google/dns-query.

To solve these issues, it is possible to add a bootstrap IP address to the config. This will use the IP to connect to the service without first having to do a lookup while still preserving the DoH URL or DoT hostname for the TLS handshake. The bootstrap-address option is available on both, DoT and DoH resolvers.

  [resolvers.google-doh-post-bootstrap]
  address = "https://dns.google/dns-query"
  protocol = "doh"
  bootstrap-address = "8.8.8.8"

Groups

Multiple resolvers can be combined into a group to implement different failover or loadbalancing algorithms within that group. Some groups are used as query modifiers (e.g. blocklist) and only have one upstream resolver. Again, each group requires a unique identifier.

Each group has resolvers which is and array of one or more resolver-identifiers. These can either be resolvers defined above, or other groups defined earlier.

The type determines which algorithm is being used. Available types:

  • round-robin - Each resolver in the group receives an equal number of queries. There is no failover.
  • fail-rotate - One resolver is active. If it fails the next becomes active and the request is retried. If the last one fails the first becomes the active again. There's no time-based automatic fail-back.
  • fail-back - Similar to fail-rotate but will attempt to fall back to the original order (prioritizing the first) if there are no failures for a minute.
  • replace - Applies regular expressions to query strings and replaces them before forwarding the query. Useful to map hostnames to a different domain on-the-fly or append domain names to short hostname queries.
  • blocklist - A blocklist has just one upstream resolver and forwards anything that does not match its expressions unmodified. If a query matches a block expression, it'll be answered with NXDOMAIN.

In this example, two upstream resolvers are grouped together and will be used alternating:

[groups]

  [groups.google-udp]
  resolvers = ["google-udp-8-8-8-8", "google-udp-8-8-4-4"]
  type = "round-robin"

Routers

Routers are used to send queries to specific upstream resolvers, groups, or to other routers based on the query type or name. Routers too require a unique identifier. Each router contains at least one route. Routes are are evaluated in the order they are defined and the first match will be used. Typically the last route should not have a type or name, making it the default route.

A route has the following fields:

  • type - If defined, only matches queries of this type
  • name - A regular expession that is applied to the query name. Note that dots in domain names need to be escaped
  • source - Network in CIDR notation. Used to route based on client IP.
  • resolver - The identifier of a resolver, group, or another router that was defined earlier.

Below, router1 sends all queries for the MX record of google.com and all its sub-domains to a group consisting of Google's DNS servers. Anything else is sent to a DNS-over-TLS resolver.

[routers]

  [routers.router1]

    [[routers.router1.routes]]
    type = "MX"
    name = '(^|\.)google\.com\.$'
    resolver="google-udp"

    [[routers.router1.routes]] # A route without type and name becomes the default route for all other queries
    resolver="cloudflare-dot"

Listeners

Listers specify how queries are received and how they should be handled. Listeners can send queries to routers, groups, or to resolvers directly. Listeners have a listen address, a protocol (udp, tcp, dot or doh), and specify the handler identifier in resolver.

[listeners]

  [listeners.local-udp]
  address = "127.0.0.1:53"
  protocol = "udp"
  resolver = "router1"

  [listeners.local-tcp]
  address = "127.0.0.1:53"
  protocol = "tcp"
  resolver = "router1"

Some listeners, namely DoH and DoT, can be configured with certificates and can enforce mutual-TLS. A secure listener of this type requires at least the server-crt and server-key options. Other options such as ca and mutual-tls can be used in more secure configurations. A listener using DoH and requiring client certificates would look like this:

  [listeners.local-doh]
  address = ":443"
  protocol = "doh"
  resolver = "upstream-dot"
  server-crt = "/path/to/server.crt"
  server-key = "/path/to/server.key"
  ca = "/path/to/ca.crt"
  mutual-tls = true

Use-cases / Examples

Use case 1: Use DNS-over-TLS for all queries locally

In this example, the goal is to send all DNS queries on the local machine encrypted via DNS-over-TLS to Cloudflare's DNS server 1.1.1.1. For this, the nameserver IP in /etc/resolv.conf is changed to 127.0.0.1. Since there is only one upstream resolver, and everything should be sent there, no group or router is needed. Both listeners are using the loopback device as only the local machine should be able to use RouteDNS. The config file would look like this:

[resolvers]

  [resolvers.cloudflare-dot]
  address = "1.1.1.1:853"
  protocol = "dot"

[listeners]

  [listeners.local-udp]
  address = "127.0.0.1:53"
  protocol = "udp"
  resolver = "cloudflare-dot"

  [listeners.local-tcp]
  address = "127.0.0.1:53"
  protocol = "tcp"
  resolver = "cloudflare-dot"

Use case 2: Prefer secure DNS in a corporate environment

In a corporate environment it's necessary to use the potentially slow and insecure company DNS servers. Only these servers are able to resolve some resources hosted in the corporate network. A router can be used to secure DNS whenever possible while still being able to resolve internal hosts.

[resolvers]

  # Define the two company DNS servers. Both use plain (insecure) DNS over UDP
  [resolvers.mycompany-dns-a]
  address = "10.0.0.1:53"
  protocol = "udp"

  [resolvers.mycompany-dns-b]
  address = "10.0.0.2:53"
  protocol = "udp"

  # Define the Cloudflare DNS-over-HTTPS resolver (GET methods) since that is most likely allowed outbound
  [resolvers.cloudflare-doh-1-1-1-1-get]
  address = "https://1.1.1.1/dns-query{?dns}"
  protocol = "doh"
  doh = { method = "GET" }

[groups]

  # Since the company DNS servers have a habit of failing, group them into a group that switches on failure
  [groups.mycompany-dns]
  resolvers = ["mycompany-dns-a", "mycompany-dns-b"]
  type = "fail-rotate"

[routers]

  [routers.router1]
  routes = [
    { name = '(^|\.)mycompany\.com\.$', resolver="mycompany-dns" }, # Use company DNS, perhaps through a VPN tunnel
    { resolver="cloudflare-doh-1-1-1-1-get" },                      # Everything else can go securely to Cloudflare
  ]

[listeners]

  [listeners.local-udp]
  address = "127.0.0.1:53"
  protocol = "udp"
  resolver = "router1"

  [listeners.local-tcp]
  address = "127.0.0.1:53"
  protocol = "tcp"
  resolver = "router1"

Use case 3: Restrict access to potentially harmful content

The goal here is to single out children's devices on the network and apply a custom blocklist to their DNS resolution. Anything on the blocklist will fail to resolve with an NXDOMAIN response. Names that aren't on the blocklist are then sent on to CleanBrowsing for any further filtering. All other devices on the network will have unfiltered access via Cloudflare's DNS server, and all queries are done using DNS-over-TLS. The config file can also be found here

[resolvers]

  [resolvers.cleanbrowsing-dot]
  address = "family-filter-dns.cleanbrowsing.org:853"
  protocol = "dot"

  [resolvers.cloudflare-dot]
  address = "1.1.1.1:853"
  protocol = "dot"

[groups]

  [groups.cleanbrowsing-filtered]
  type = "blocklist"
  resolvers = ["cleanbrowsing-dot"] # Anything that passes the filter is sent on to this resolver
  blocklist = [                     # Define the names to be blocked
    '(^|\.)facebook\.com\.$',
    '(^|\.)twitter\.com\.$',
  ]

[routers]

  [routers.router1]
  routes = [
    { source = "192.168.1.123/32", resolver="cleanbrowsing-filtered" }, # The IP or network that will use the blocklist in CIDR notation
    { resolver="cloudflare-dot" }, # Default for everyone else
  ]

[listeners]

  [listeners.local-udp]
  address = ":53"
  protocol = "udp"
  resolver = "router1"

  [listeners.local-tcp]
  address = ":53"
  protocol = "tcp"
  resolver = "router1"

Use case 4: Replace queries for short names with FQDN

If adding a search list to /etc/resolv.conf is not an option, a replace group can be used to add the correct domain based on the name in the query. It's possible to modify or expand query strings by matching on a regex and replacing it with an alternative expression. The replace string supports expansion like $1 to refer to a match in the regex. The replace can be combined with routers and resolvers as with all the other groups.

In this example, queries for short names starting with my- will have the domain home-domain.com. appended to them and the prefix removed. A query for my-server. from the client will result in a query for server.home-domain.com. to Cloudflare. The response to the client will reference my-server. with the response from Cloudflare. More than one replace rule can be defined and they are applied to the query name in order. Any other queries will pass without modification.

[resolvers]

  [resolvers.cloudflare-dot]
  address = "1.1.1.1:853"
  protocol = "dot"

[groups]

  [groups.append-my-domain]
  type = "replace"
  resolvers = ["cloudflare-dot"]
  replace = [
    { from = '^my-([^.]+\.)$', to = '${1}home-domain.com.' },
  ]

[listeners]

  [listeners.local-udp]
  address = ":53"
  protocol = "udp"
  resolver = "append-my-domain"

Use case 5: Proxying out of a restricted or untrusted location

In this use case the goal is to use get access to unfiltered and unmonitored DNS services in a location that does not offer it normally. Direct access to well-known public DoT or DoH providers may be blocked, forcing plain DNS. It may be possible to setup an instansce of RouteDNS in a less restricted location to act as proxy, offering DoH which is harder to detect and block. To prevent unauthorized access to the proxy, the config will enforce mutual-TLS with a client certificate signed by a custom CA.

The following config on the server will accept queries over DNS-over-HTTPS from authorized clients (with valid and signed certificate), and forward all queries to Cloudflare using DNS-over-TLS.

[resolvers]

  [resolvers.cloudflare-dot]
  address = "1.1.1.1:853"
  protocol = "dot"

[listeners]

  [listeners.proxy-doh]
  address =
5EBA
 ":443"
  protocol = "doh"
  resolver = "cloudflare-dot"
  server-crt = "/path/to/server.crt"
  server-key = "/path/to/server.key"
  ca = "/path/to/ca.crt"
  mutual-tls = true

The client is configured to act as local DNS resolver, handling all queries from the local OS. Every query is then forwarded to the proxy using DoH. The client needs to have a signed certificate as the proxy is configured to require it.

[resolvers]

  [resolvers.proxy-doh]
  address = "https://<Proxy-IP>:443/dns-query"
  protocol = "doh"
  ca = "/path/to/ca.crt"
  client-crt = "/path/to/client.crt"
  client-key = "/path/to/client.crt"

[listeners]

  [listeners.local]
  address = ":53"
  protocol = "udp"
  resolver = "proxy-doh"

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DNS stub resolver, proxy and router with support for DoT and DoH

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