# Stubby for OpenWRT
## Stubby Description
-[Stubby](https://dnsprivacy.org/wiki/display/DP/DNS+Privacy+Daemon+-+Stubby) is an application that acts as a local DNS Privacy stub resolver (using DNS-over-TLS). Stubby encrypts DNS queries sent from a client machine (desktop or laptop) to a DNS Privacy resolver increasing end user privacy.
+
+[Stubby](https://dnsprivacy.org/wiki/display/DP/DNS+Privacy+Daemon+-+Stubby) is
+an application that acts as a local DNS Privacy stub resolver (using
+DNS-over-TLS). Stubby encrypts DNS queries sent from a client machine to a DNS
+Privacy resolver increasing end user privacy.
+
+Stubby is useful on an OpenWRT device, because it can sit between the usual DNS
+resolver (dnsmasq by default) and the upstream DNS resolver and be used to
+ensure that DNS traffic is encrypted between the OpenWRT device and the
+resolver.
Stubby is developed by the [getdns](http://getdnsapi.net/) project.
-For more background and FAQ see our [About Stubby](https://dnsprivacy.org/wiki/display/DP/About+Stubby) page. Stubby is in the early stages of development but is suitable for technical/advanced users. A more generally user-friendly version is on the way!
+For more background and FAQ see the [About
+Stubby](https://dnsprivacy.org/wiki/display/DP/About+Stubby) page.
+
+
+## Installation
+
+Installation of this package can be achieved at the command line using `opkg
+install stubby`, or via the LUCI Web Interface. Installing the stubby package
+will also install the required dependency packages, including the
+`ca-certificates` package.
+
+## Configuration
+
+The default configuration of the package has been chosen to ensure that stubby
+should work after installation.
+
+By default, configuration of stubby is integrated with the OpenWRT UCI system
+using the file `/etc/config/stubby`. The configuration options available are
+also documented in that file. If for some reason you wish to configure stubby
+using the `/etc/stubby/stubby.yml` file, then you simply need to set `option
+manual '1'` in `/etc/config/stubby` and all other settings in
+`/etc/config/stubby` will be ignored.
+
+### Stubby port and addresses
+
+The default configuration ensures that stubby listens on port 5453 on the
+loopback interfaces for IPv4 and IPv6. As such, by default, stubby will respond
+only to lookups from the OpenWRT device itself.
+
+By setting the listening ports to non-standard values, this allows users to keep
+the main name server daemon in place (dnsmasq/unbound/etc.) and have that name
+server forward to stubby.
+
+### Upstream resolvers
+
+The default package configuration uses the CloudFlare resolvers, configured for
+both IPv4 and IPv6.
+
+CloudFlare have not published SPKI pinsets, and even though they are available,
+they have made no commitment to maintaining them. Using the currently known SPKI
+pinsets for CloudFlare brings the risk that in the future they may be changed by
+CloudFlare, and DNS would stop working. The default configuration has those SPKI
+entries commented out for this reason.
+
+[CloudFlare's privacy
+statement](https://developers.cloudflare.com/1.1.1.1/commitment-to-privacy/)
+details how they treat data from DNS requests.
+
+More resolvers are available in the [upstream stubby example
+configuration](https://github.com/getdnsapi/stubby/blob/develop/stubby.yml.example)
+and the [DNS Privacy
+list](https://dnsprivacy.org/wiki/display/DP/DNS+Privacy+Test+Servers).
+
+## Integration of stubby with dnsmasq
+
+The recommended way to use stubby on an OpenWRT device is to integrate it with a
+caching resolver. The default caching resolver in OpenWRT is dnsmasq.
+
+### Set dnsmasq to send DNS requests to stubby
+
+Since dnsmasq responds to LAN DNS requests on port 53 of the OpenWRT device by
+default, all that is required is to have dnsmasq forward those requests to
+stubby which is listening on port 5453 of the OpenWRT device. To achieve this,
+we need to set the `server` option in the dnsmasq configuration in the
+`/etc/config/dhcp` file to `'127.0.0.1#5453'`. We also need to tell dnsmasq not
+to use resolvers found in `/etc/resolv.conf` by setting the dnsmasq option
+`noresolv` to `1` in the same file. This can be achieved by editing the
+`/etc/config/dhcp` file directly or executing the following commands at the
+command line:
+
+ uci add_list dhcp.@dnsmasq[-1].server='127.0.0.1#5453'
+ uci dhcp.@dnsmasq[-1].noresolv=1
+ uci commit
+
+The same outcome can be achieved in the LUCI web interface as follows:
+
+1. Select the Network->DHCP and DNS menu entry.
+2. In the "General Settings" tab, enter the address `127.0.0.1#5453` as the only
+ entry in the "DNS Forwardings" dialogue.
+3. In the "Resolv and Host files" tab tick the "Ignore resolve file" checkbox.
+
+### Disable sending DNS requests to ISP provided DNS servers
+
+The configuration changes in the previous section ensure that DNS queries are
+sent over TLS encrypted connections *once dnsmasq and stubby are started*. When
+the OpenWRT device is first brought up, there is a possibility that DNS queries
+can go to ISP provided DNS servers ahead of dnsmasq and stubby being active. In
+order to mitigate this leakage, it's necessary to ensure that upstream resolvers
+aren't available, and the only DNS resolver used by the system is
+dnsmasq+stubby.
+
+This requires setting the option `peerdns` to `0` and the option `dns` to the
+loopback address for both the `wan` and `wan6` interfaces in the
+`/etc/config/network` file. This can be achieved by editing the
+`/etc/config/network` file directly, or by executing the following commands:
+
+ uci set network.wan.peerdns='0'
+ uci set network.wan.dns='127.0.0.1'
+ uci set network.wan6.peerdns='0'
+ uci set network.wan6.dns='0::1'
+ uci commit
+
+The same outcome can also be achieved using the LUCI web interface as follows:
+
+1. Select the Network->Interfaces menu entry.
+2. Click on Edit for the WAN interfaces.
+3. Choose the Advanced Settings tab.
+4. Unselect the "Use DNS servers advertised by peer" checkbox
+5. Enter `127.0.0.1` in the "Use custom DNS servers" dialogue box.
+6. Repeat the above steps for the WAN6 interface, but use the address `0::1`
+ instead of `127.0.0.1`.
+
+### Enabling DNSSEC
+
+The configuration described above ensures that DNS queries are executed over TLS
+encrypted links. However, the responses themselves are not validated; DNSSEC
+provides the ability to validate returned DNS responses, and mitigate against
+DNS poisoning risks.
+
+With the combination of stubby+dnsmasq there are two possible ways to enable
+DNSSEC:
+
+1. Configure stubby to perform DNSSEC validation, and configure dnsmasq to proxy
+ the DNSSEC data to clients.
+2. Configure stubby not to perform DNSSEC validation and configure dnsmasq to
+ require DNSSEC validation.
+
+Either option achieves the same outcome, and there appears to be little reason
+for choosing one over the other other than that the second option is easier to
+configure in the LUCI web interface. Both options are detailed below, and both
+require that the `dnsmasq` package on the OpenWRT device is replaced with the
+`dnsmasq-full` package. That can be achieved by running the following command:
+
+ opkg install dnsmasq-full --download-only && opkg remove dnsmasq && opkg install dnsmasq-full --cache . && rm *.ipk
+
+#### DNSSEC by stubby
+
+Configuring stubby to perform DNSSEC validation requires setting the stubby
+configuration option `dnssec_return_status` to `'1'` in `/etc/config/stubby`,
+which can be done by editing the file directly or by executing the commands:
+
+ uci set stubby.global.dnssec_return_status=1
+ uci commit
+
+With stubby performing DNSSEC validation, dnsmasq needs to be configured to
+proxy the DNSSEC data to clients. This requires setting the option `proxydnssec`
+to 1 in the dnsmasq configuration in `/etc/config/dhcp`. That can be achieved by
+the following commands:
+
+ uci set dhcp.@dnsmasq[-1].proxydnssec=1
+ uci commit
+
+#### DNSSEC by dnsmasq
+
+Configuring dnsmasq to perform DNSSEC validation requires setting the dnsmasq
+option `dnssec` to `1` in the `/etc/config/dhcp` file. In addition, it is
+advisable to also set the dnsmasq option `dnsseccheckunsigned` to `1`. this can
+be achieved by editing the file `/etc/config/dhcp` or by executing the following
+commands:
+
+ uci set dhcp.@dnsmasq[-1].dnssec=1
+ uci set dhcp.@dnsmasq[-1].dnsseccheckunsigned=1
+ uci commit
+
+The same options can be set in the LUCI web interface as follows:
+
+1. Select the "Network->DHCP and DNS" menu entry.
+2. Select the "Advanced Settings" tab.
+3. Ensure both the "DNSSEC" and "DNSSEC check unsigned" check boxes are ticked.
+
+#### Validating DNSSEC operation
+
+Having configured DNSSEC validation using one of the two approaches above, it's
+important to check it's actually working. The following command can be used:
+
+ dig dnssectest.sidn.nl +dnssec +multi @192.168.1.1
+
+This command should return output like the following:
+
+ ; <<>> DiG 9.11.4-P1-RedHat-9.11.4-5.P1.fc28 <<>> dnssectest.sidn.nl +dnssec +multi @192.168.1.1
+ ;; global options: +cmd
+ ;; Got answer:
+ ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26579
+ ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
+
+ ;; OPT PSEUDOSECTION:
+ ; EDNS: version: 0, flags: do; udp: 512
+ ;; QUESTION SECTION:
+ ;dnssectest.sidn.nl. IN A
+
+ ;; ANSWER SECTION:
+ dnssectest.sidn.nl. 14399 IN A 213.136.9.12
+ dnssectest.sidn.nl. 14399 IN RRSIG A 8 3 14400 (
+ 20181104071058 20181005071058 42033 sidn.nl.
+ YAQl3tef36M9EQUOmCneHKCCkxox3csLpfUOql5i/6ND
+ zPrQFsNr3g32HPoxOsi+hD2BE5+bEsnARayDSVLyx0qU
+ 6Hpi2rzQ0zGNZZkCJhCsdp3wnM1BWlMgPrCD0iIsJDok
+ +DH5zu+yYufVUdSLQrMqA3MZDFUIqDUqSZuYDF4= )
+
+ ;; Query time: 77 msec
+ ;; SERVER: 192.168.1.1#53(192.168.1.1)
+ ;; WHEN: Sat Oct 06 20:36:25 BST 2018
+ ;; MSG SIZE rcvd: 230
+
+The key thing to note is the `flags: qr rd ra ad` part - the `ad` flag signifies
+that DNSSEC validation is working. If that flag is absent DNSSEC validation is
+not working.
+
+## Appendix: stubby configuration options
+
+This section details the options available for use in the `/etc/config/stubby`
+file. The `global` configuration section specifies the configuration parameters
+for the stubby daemon. One or more `resolver` sections are used to configure
+upstream resolvers for the stubby daemon to use.
+
+### `global` section options
+
+#### `option manual`
+
+Specify whether to use this file to configure the stubby service. If this is set
+to `'1'` stubby will be configured using the file `/etc/stubby/stubby.yml`. If this
+is set to `'0'`, configuration options will be taken from this file, and the service
+will be managed through UCI.
+
+#### `option trigger`
+
+This specifies an interface to trigger stubby start up on; stubby startup will
+be triggered by a procd signal associated with this interface being ready. If
+this interface is restarted, stubby will also be restarted.
+
+This option can also be set to `'timed'`, in which case a time, specified by the
+option `triggerdelay`, will be waited before starting stubby.
+
+
+#### `option triggerdelay`
+
+If the `trigger` option specifies an interface, this option sets the time that
+is waited after the procd signal is received before starting stubby.
+
+If `trigger` is set to `'timed'` then this is the delay before starting stubby.
+This option is specified in seconds and defaults to the value `'2'`.
+
+#### `list dns_transport`
+
+The `dns_transport` list specifies the allowed transports. Allowed values are:
+`GETDNS_TRANSPORT_UDP`, `GETDNS_TRANSPORT_TCP` and `GETDNS_TRANSPORT_TLS`. The
+transports are tried in the order listed.
+
+#### `option tls_authentication`
+
+This option specifies whether TLS authentication is mandatory. A value of `'1'`
+mandates TLS authentication, and is the default.
+
+If this is set to `'0'`, and `GETDNS_TRANSPORT_TCP` or `GETDNS_TRANSPORT_UDP`
+appears in the `dns_transport` list, stubby is allowed to fall back to non-TLS
+authenticated lookups. You probably don't want this though.
+
+#### `option tls_query_padding_blocksize`
+
+This option specifies the block size to pad DNS queries to. You shouldn't need
+to set this to anything but `'128'` (the default), as recommended by
+https://tools.ietf.org/html/draft-ietf-dprive-padding-policy-03
+
+#### `option tls_connection_retries`
+
+This option specifies the number of connection failures stubby permits before
+Stubby backs-off from using an individual upstream resolver. You shouldn't need
+to change this from the default value of `'2'`.
+
+#### `option tls_backoff_time`
+
+This option specifies the maximum time in seconds Stubby will back-off from
+using an individual upstream after failures. You shouldn't need to change this
+from the default value of `'3600'`.
+
+#### `option timeout`
+
+This option specifies the timeout on getting a response to an individual
+request. This is specified in milliseconds. You shouldn't need to change this
+from the default value of ` '5000'`.
+
+#### `option dnssec_return_status`
+
+This option specifies whether stubby should require DNSSEC validation. Specify
+to `'1'` to turn on validation, and `'0'` to turn it off. By default it is off.
+
+#### `option appdata_dir`
+
+This option specifies the location for storing stubby runtime data. In
+particular, if DNSSEC is turned on, stubby will store its automatically
+retrieved trust anchor data here. The default value is `'/var/lib/stubby'`.
+
+#### `option dnssec_trust_anchors`
+
+This option sets the location of the file containing the trust anchor data used
+for DNSSEC validation. If this is not specified, stubby will automatically
+retrieve a trust anchor at startup. It's unlikely you'll want to manage the
+trust anchor data manually, so in most cases this is not needed. By default,
+this is unset.
+
+#### `option edns_client_subnet_private`
+
+This option specifies whether to enforce ECS client privacy. The default is
+`'1'`. Set to `'0'` to disable client privacy.
+
+For more details see Section 7.1.2 [here](https://tools.ietf.org/html/rfc7871).
+
+#### `option idle_timeout`
+
+This option specifies the time (in milliseconds) to hold TLS connections open to
+avoid the overhead of opening a new connection for every query. You should not
+normally need to change this from the default value (currently `'10000'`).
+
+See [here](https://tools.ietf.org/html/rfc7828) for more details.
+
+#### `option round_robin_upstreams`
-## Prerequisites
+This option specifies how stubby will use the upstream DNS resolvers. Set to
+`'1'` (the default) to instruct stubby to distribute queries across all
+available name servers - this will use multiple simultaneous connections which
+can give better performance in most (but not all) cases. Set to `'0'` to treat
+the upstream resolvers as an ordered list and use a single upstream resolver
+until it becomes unavailable, then use the next one.
-You must have a ca cert bundle installed on your device for stubby to make the TLS enabled connections.
+#### `list listen_address`
-- You can install this by running the following: opkg install ca-certificates
-- You can also install this through the LUCI web interface
+This list sets the addresses and ports for the stubby daemon to listen for
+requests on. the default configuration configures stubby to listen on port 5453
+on the loopback interface for both IPv4 and IPv6.
-## Package Overview
-This package has some modifications that makes it differ from the default upstream configuration. They are outlined below.
+#### `option log_level`
-### General Cleanup
-Comments are removed, etc.
+If set, this option specifies the level of logging from the stubby
+daemon. By default, this option is not set.
-### EDNS Client-Subnet Option
-The value of "edns_client_subnet_private" is '1' in the upstream default config. This informs the upstream resolver to NOT forward your connection's IP to any other upstream servers. This is good for privacy, but could result in sub-optimal routing to CDNs, etc.
+The possible levels are:
-We retain the upstream value since privacy is a key user motivation for using DNS-over-TLS, but note users encountering poor routing may consider changing it.
+ '0': EMERG - System is unusable
+ '1': ALERT - Action must be taken immediately
+ '2': CRIT - Critical conditions
+ '3': ERROR - Error conditions
+ '4': WARN - Warning conditions
+ '5': NOTICE - Normal, but significant, condition
+ '6': INFO - Informational message
+ '7': DEBUG - Debug-level message
-### Default Listening Ports Changed
-The value of "listen_addresses" in the default config does not list port numbers, which will cause stubby to default to port 53. However, Openwrt defaults to dnsmasq as the main name server daemon, which runs on port 53. By setting the listening ports to non-standard values, this allows users to keep the main name server daemon in place (dnsmasq/unbound/etc.) and have that name server forward to stubby.
+#### `option command_line_arguments`
-Additionally, due to the slight overhead involved with DNS-over-TLS, it is recommended to have a caching name server on the network.
+This option specifies additional command line arguments for
+stubby daemon. By default, this is an empty string.
+
+### `resolver` section options
-### Round Robin Upstream Setting Changed
+#### `option address`
-The default stubby config list multiple upstream resolvers, and because of this, it makes sense to "load balance" between them. However, in this package's default stubby config, the only upstream service listed is Cloudflare. One entry is for ipv6 and one for ipv4.
+This option specifies the resolver IP address, and can either be an IPv4 or an
+IPv6 address.
-By setting the "round_robin_upstreams" value to 0, we are simply forcing stubby to try and use ipv6 connectivity to Cloudflare first, and if not available, simply use the ipv4 service.
+#### `option tls_auth_name`
-Cloudflare is an Anycast DNS service. This should take care of any needed "failover" in the event that one of Cloudflare's nodes goes down.
+This option specifies the upstream domain name used for TLS authentication with
+the supplied server certificate
-### Upstream Resolvers Changed
+#### `list spki`
-Most of the default resolvers for stubby are in Europe. To provide a better experience for a larger number of users, this package defaults to using Cloudflare's DNS service. Cloudflare's DNS service has been ranked number one in speed against many other top resolvers.
+This list specifies the SPKI pinset which is verified against the keys in the
+server cerrtificate. The values takes the form `'<digest type>/value>'`, where
+the `digest type` is the hashing algorithm used, and the value is the Base64
+encoded hash of the public key. At present, only `sha256` is
+supported for the digest type.
-https://developers.Cloudflare.com/1.1.1.1/commitment-to-privacy/
-https://www.dnsperf.com/dns-resolver/1-1-1-1
+This should ONLY be used if the upstream resolver has committed to maintaining
+the pinset. CloudFlare have made no such commitment, and so we do not specify
+the SPKI values in the default configuration, even though they are available.
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