unbound: improve startup and dhcp script robustness
- prevent rapid overlap in DHCP script updates
- check and allow localhost forwards with specific applications
- add option for rate limiting inbound queries
- change UCI list to table format with Unbound conf references
Signed-off-by: Eric Luehrsen <ericluehrsen@gmail.com>
Unbound may be useful on consumer grade embedded hardware. It is fully DNSSEC and TLS capable. It is _intended_ to be a recursive resolver only. NLnet Labs [NSD](https://www.nlnetlabs.nl/projects/nsd/) is _intended_ for the authoritative task. This is different than [ISC Bind](https://www.isc.org/downloads/bind/) and its inclusive functions. Unbound configuration effort and memory consumption may be easier to control. A consumer could have their own recursive resolver with 8/64 MB router, and remove potential issues from forwarding resolvers outside of their control.
This package builds on Unbounds capabilities with OpenWrt UCI. Not every Unbound option is in UCI, but rather, UCI simplifies the combination of related options. Unbounds native options are bundled and balanced within a smaller set of choices. Options include resources, DNSSEC, access control, and some TTL tweaking. The UCI also provides an escape option and works at the raw "unbound.conf" level.
This package builds on Unbounds capabilities with OpenWrt UCI. Not every Unbound option is in UCI, but rather, UCI simplifies the combination of related options. Unbounds native options are bundled and balanced within a smaller set of choices. Options include resources, DNSSEC, access control, and some TTL tweaking. The UCI also provides an escape option and works at the raw `unbound.conf` level.
## HOW TO: Ad Blocking
The UCI scripts will work with [net/adblock](https://github.com/openwrt/packages/blob/master/net/adblock/files/README.md), if it is installed and enabled. Its all detected and integrated automatically. In brief, the adblock scripts create distinct local-zone files that are simply included in the unbound conf file during UCI generation. If you don't want this, then disable adblock or reconfigure adblock to not send these files to Unbound.
@ -18,18 +18,18 @@ A few tweaks may be needed to enhance the realiability and effectiveness. Ad Blo
**/etc/config/firewall**:
```
config rule
option name 'Block-Public-DNS'
option enabled '1'
option src 'lan'
option dest 'wan'
option dest_port '53 853 5353'
option proto 'tcpudp'
option enabled '1'
option family 'any'
option name 'Block-Public-DNS'
option proto 'tcpudp'
option src 'lan'
option target 'REJECT'
```
## HOW TO: Integrate with DHCP
Some UCI options and scripts help Unbound to work with DHCP servers to load the local DNS. The examples provided here are serial dnsmasq-unbound, parallel dnsmasq-unbound, and unbound scripted with odhcpd.
Some UCI options and scripts help Unbound to work with DHCP servers to load the local DNS. The examples provided here are serial dnsmasq with unbound, parallel dnsmasq with unbound, and unbound scripted with odhcpd.
### Serial dnsmasq
In this case, dnsmasq is not changed *much* with respect to the default [OpenWrt](https://openwrt.org/docs/guide-user/base-system/dns_configuration) configuration. Here dnsmasq is forced to use the local Unbound instance as the lone upstream DNS server, instead of your ISP. This may be the easiest implementation, but performance degradation can occur in high volume networks. Unbound and dnsmasq effectively have the same information in memory, and all transfers are double handled.
@ -52,22 +52,22 @@ config unbound
config dnsmasq
option domain 'yourdomain'
option noresolv '1'
option resolvfile '/tmp/resolv.conf.auto'
option port '53'
option resolvfile '/tmp/resolv.conf.auto'
list server '127.0.0.1#1053'
list server '::1#1053'
...
```
### Parallel dnsmasq
In this case, Unbound serves your local network directly for all purposes. It will look over to dnsmasq for DHCP-DNS resolution. Unbound is generally accessible on port 53, and dnsmasq is only accessed at 127.0.0.1:1053 by Unbound. Although you can dig/drill/nslookup remotely with the proper directives.
In this case, Unbound serves your local network directly for all purposes. It will look over to dnsmasq for DHCP-DNS resolution. Unbound is generally accessible on port 53, and dnsmasq is only accessed at `127.0.0.1#1053` by Unbound. Although you can dig/drill/nslookup remotely with the proper directives.
**/etc/config/unbound**:
```
config unbound
# likely you want to match domain option between Unbound and dnsmasq
option domain 'yourdomain'
option dhcp_link 'dnsmasq'
option domain 'yourdomain'
option listen_port '53'
...
```
@ -77,8 +77,8 @@ config unbound
config dnsmasq
option domain 'yourdomain'
option noresolv '1'
option resolvfile '/tmp/resolv.conf.auto'
option port '1053'
option resolvfile '/tmp/resolv.conf.auto'
...
config dhcp 'lan'
@ -125,10 +125,10 @@ config dhcp 'lan'
...
config odhcpd 'odhcpd'
option maindhcp '1'
option leasefile '/var/lib/odhcpd/dhcp.leases'
# this is where the magic happens
option leasetrigger '/usr/lib/unbound/odhcpd.sh'
option maindhcp '1'
```
## HOW TO: Manual Override
@ -160,10 +160,10 @@ Unbound has the ability to AXFR a whole zone from an authoritative server to pre
list server '192.0.2.153@443#dns.alternate.example.org'
list zone_name '.'
option zone_type 'forward_zone'
```
## Optional Compile Switches
@ -195,254 +195,59 @@ Unbound can be changed by toggling switches within `make menuconfig` Libraries/N
Note: if you use python, then you will need to manual configure and you cannot use chroot. The scripts are not yet enhanced enough to set up the directory binding.
## Complete List of UCI Options
**/etc/config/unbound**:
```
config unbound
Currently only one instance is supported.
option add_extra_dns '0'
Level. Execute traditional DNS overrides found in `/etc/config/dhcp`.
Optional so you may use other Unbound conf or redirect to NSD instance.
0 - Ignore `/etc/config/dhcp`
1 - Use only 'domain' clause (host records)
2 - Use 'domain', 'mxhost', and 'srvhost' clauses
3 - Use all of 'domain', 'mxhost', 'srvhost', and 'cname' clauses
option add_local_fqdn '0'
Level. This puts your routers host name in the LAN (local) DNS.
Each level is more detailed and comprehensive.
0 - Disabled
1 - Host Name on only the primary address
2 - Host Name on all addresses found (except link)
3 - FQDN and host name on all addresses (except link)
4 - Above and interfaces named <iface>.<hostname>.<domain>
option add_wan_fqdn '0'
Level. Same as previous option only this applies to the WAN. WAN are
inferred by a UCI `config dhcp` entry that contains the 'option ignore 1'.
option dns_assist 'none'
Program Name. Use DNS helpers found on local host and match to their UCI.
Only program 'ipset-dns' is supported so far. NSD and Bind might be useful
but they don't have UCI to parse.
option dns64 '0'
Boolean. Enable DNS64 through Unbound in order to bridge networks that are
IPV6 only and IPV4 only (see RFC6052).
option dns64_prefix '64:ff9b::/96'
IPV6 Prefix. The IPV6 prefix wrapped on the IPV4 address for DNS64. You
should use RFC6052 "well known" address, unless you also redirect to a proxy
or gateway for your NAT64.
option dhcp_link 'none'
Program Name. Link to one of the supported programs we have scripts
for. You may also need to install a trigger script in the DHCP
servers configuration. See HOW TO above.
option dhcp4_slaac6 '0'
Boolean. Some DHCP servers do this natively (dnsmasq). Otherwise
the script provided with this package will try to fabricate SLAAC
IP6 addresses from DHCPv4 MAC records.
option domain 'lan'
Unbound local-zone: <domain><type>. This is used to suffix all
host records, and maintain a local zone. When dnsmasq is dhcp_link
however, then this option is ignored (dnsmasq does it all).
option domain_type 'static'
Unbound local-zone: <domain><type>. This allows you to lock
down or allow forwarding of the local zone. Notable types:
static - typical single router setup much like OpenWrt dnsmasq default
refuse - to answer overtly with DNS code REFUSED
deny - to drop queries for the local zone
transparent - to use your manually added forward-zone: or stub-zone: clause
option edns_size '1280'
Bytes. Extended DNS is necessary for DNSSEC. However, it can run
into MTU issues. Use this size in bytes to manage drop outs.
option extended_stats '0'
Boolean. extended statistics are printed from unbound-control.
Keeping track of more statistics takes time.
option hide_binddata '1'
Boolean. If enabled version.server, version.bind, id.server, and
hostname.bind queries are refused.
option interface_auto '1'
Boolean. If enabled DNS replies will have the same source address as
the request was sent to.
option listen_port '53'
Port. Incoming. Where Unbound will listen for queries.
option localservice '1'
Boolean. Prevent DNS amplification attacks. Only provide access to
Unbound from subnets this machine has interfaces on.
option manual_conf '0'
Boolean. Skip all this UCI nonsense. Manually edit the
configuration. Make changes to /etc/unbound/unbound.conf.
option num_threads '1'
Count. Enable multithreading with the "heavy traffic" variant. Base variant
spins each as whole proces and is not efficient. Two threads may be used,
but they use one shared cache slab. More edges into an industrial setup,
and UCI simplificaitons may not be appropriate.
option protocol 'mixed'
Unbound can limit its protocol used for recursive queries.
ip4_only - old fashioned IPv4 upstream and downstream
ip6_only - test environment only; could cauase problems
ip6_local - upstream IPv4 only and local network IPv4 and IPv6
ip6_prefer - both IPv4 and IPv6 but try IPv6 first
mixed - both IPv4 and IPv6
default - Unbound built-in defaults
option query_minimize '0'
Boolean. Enable a minor privacy option. Don't let each server know the next
recursion. Query one piece at a time.
option query_min_strict '0'
Boolean. Query minimize is best effort and will fall back to normal when it
must. This option prevents the fall back, but less than standard name
servers will fail to resolve their domains.
option rebind_localhost '0'
Boolean. Prevent loopback "127.0.0.0/8" or "::1/128" responses. These may
used by black hole servers for good purposes like ad-blocking or parental
access control. Obviously these responses may be used to for bad purposes.
option rebind_protection '1'
Level. Block your local address responses from global DNS. A poisoned
reponse within "192.168.0.0/24" or "fd00::/8" could turn a local browser
into an external attack proxy server. IP6 GLA may be vulnerable also.
0 - Off
1 - Only RFC 1918 and 4193 responses blocked
2 - Plus GLA /64 on designated interface(s)
3 - Plus DHCP-PD range passed down interfaces (not implemented)
option recursion 'passive'
Unbound has many options for recrusion but UCI is bundled for simplicity.
passive - slower until cache fills but kind on CPU load
default - Unbound built-in defaults
aggressive - uses prefetching to handle more requests quickly
option resource 'small'
Unbound has many options for resources but UCI is bundled for simplicity.
tiny - similar to published memory restricted configuration
small - about half of medium
medium - similar to default, but fixed for consistency
default - Unbound built-in defaults
large - about double of medium
option root_age '9'
Days. >90 Disables. Age limit for Unbound root data like root DNSSEC key.
Unbound uses RFC 5011 to manage root key. This could harm flash ROM. This
activity is mapped to "tmpfs," but every so often it needs to be copied back
to flash for the next reboot.
option ttl_min '120'
Seconds. Minimum TTL in cache. Recursion can be expensive without cache. A
low TTL is normal for server migration. A low TTL can be abused for snoop-
vertising (DNS hit counts; recording query IP). Typical to configure maybe
Boolean. Enable DNSSEC. Unbound names this the "validator" module.
option validator_ntp '1'
Boolean. Disable DNSSEC time checks at boot. Once NTP confirms global real
time, then DNSSEC is restarted at full strength. Many embedded devices don't
have a real time power off clock. NTP needs DNS to resolve servers. This
works around the chicken-and-egg.
option verbosity '1'
Level. Sets Unbounds logging intensity.
list domain_insecure 'ntp.somewhere.org'
Domain. Domains that you wish to skip DNSSEC. It is one way around NTP
chicken and egg. Your DHCP servered domains are automatically included.
list trigger_interface 'lan' 'wan'
Interface (logical). This option is a work around for netifd/procd
interaction with WAN DHCPv6. Minor RA or DHCP changes in IP6 can cause
netifd to execute procd interface reload. Limit Unbound procd triggers to
LAN and WAN (IP4 only) to prevent restart @2-3 minutes.
config zone
Create Unbounds forward-zone:, stub-zone:, or auth-zone: clauses
option enabled 1
Boolean. Enable the zone clause.
option fallback 1
Boolean. Permit normal recursion when the narrowly selected servers in this
zone are unresponsive or return empty responses. Disable, if there are
security concerns (forward only internal to organization).
option port 53
Port. Servers are contact on this port for plain DNS operations.
option resolv_conf 0
Boolean. Use "resolv.conf" as it was filled by the DHCP client. This can be
used to forward zones within your ISP (mail.example.net) or that have co-
located services (streamed-movies.example.com). Recursion may not yield the
most local result, but forwarding may instead.
option tls_index (n/a)
Domain. Name TLS certificates are signed for (dns.example.net). If this
option is ommitted, then Unbound will make connections but not validate.
option tls_port 853
Port. Servers are contact on this port for DNS over TLS operations.
option tls_upstream 0
Boolean. Use TLS to contact the zone server.
option url_dir
String. http or https path, directory part only, to the zone file for
auth_zone type only. Files "${zone_name}.zone" are expect in this path.
option zone_type (n/a)
State. Required field or the clause is effectively disabled. Check Unbound
documentation for clarity (unbound-conf).
auth_zone - prefetch whole zones from authoritative server (ICANN)
forward_zone - forward queries in these domains to the listed servers
stub_zone - force recursion of these domains to the listed servers
list server (n/a)
IP. Every zone must have one server. Stub and forward require IP to prevent
chicken and egg (due to UCI simplicity). Authoritative prefetch may use a
server name.
list zone_name
Domain. Every zone must represent some part of the DNS tree. It can be all
of it "." or you internal organization domain "example.com." Within each
zone clause all zone names will be matched to all servers.
```
## Replaced Options
config unbound / option prefetch_root
List the domains in a zone with type auth_zone and fill in the server or url
fields. Root zones are ready but disabled in default install UCI.
config unbound / list domain_forward
List the domains in a zone with type forward_zone and enable the
resolv_conf option.
config unbound / list rebind_interface
Enable rebind_protection at 2 and all DHCP interfaces are also protected for
IPV6 GLA (parallel to subnets in add_local_fqdn).
## Complete UCI
### config unbound
One instance is supported currently.
| UCI | Default | Units | Description | Unbound |
| --- | ------- | ----- | ----------- | ------- |
| add_extra_dns | 0 | level | Read OpenWrt traditional options for `dnsmasq`.<br>`0`: Disabled<br>`1`: Use only domain<br>`2`: Use domain, mxhost, and srvhost<br>`3`: Use all cname, domain, mxhost, and srvhost | local-data: |
| add_local_fqdn | 0 | level | Each level puts a more detailed router entry within the LAN DNS (except link).<br>`0`: Disabled<br>`1`: Host name on the primary address<br>`2`: Host name on all addresses<br>`3`: FQDN and host name on all addresses<br>`4`: FQDN defined by "iface.hostname.domain" | local-zone: local-data: |
| add_wan_fqdn | 0 | level | Same as `add_local_fqdn` but on WAN as inferred by `config dhcp` with `option ignore 1`. | local-zone: local-data: |
| dns64 | 0 | boolean | Enable DNS64 RFC6052 to bridge IPv4 and IPv6 networks. | module: dns64 |
| dns64_prefix | 64:ff9b::/96 | subnet | DNS64 RFC6052 IPv4 in IPv6 well known prefix. | dns64-prefix: |
| dhcp_link | none | program | Link to a DHCP server with supported scripts. See HOW TO above. | local-zone: local-data: forward-zone: |
| dhcp4_slaac6 | 0 | boolean | Infer SLAAC IE64 IPv6 addresses from DHCPv4 MAC in DHCP link scripts. | - |
| domain | lan | domain | This will suffix DHCP host records and be the default search domain. | local-zone: |
| domain_insecure | (empty) | domain | **List** domains that you wish to skip DNSSEC. It is one way around NTP chicken and egg. Your DHCP domains are automatically included. | domain-insecure: |
| domain_type | static | state | This allows you to lock down or allow forwarding of the local zone.<br>`static`: no forwarding like dnsmasq default<br>`refuse`: answer overtly with REFUSED<br>`deny`: covertly drop all queries<br>`transparent`: may continue forwarding or recusion | local-zone: |
| edns_size | 1280 | bytes | Extended DNS is necessary for DNSSEC. Use this to manage MTU issues. | edns-size: |
| extended_stats | 0 | boolean | Extended statistics are stored in Unbound memory for report by `unbound-control`. | extended-statistics: |
| hide_binddata | 1 | boolean | Refuse possible attack queries like version.server, version.bind, id.server, and hostname.bind. | hide-identity: hide-version: |
| interface_auto | 1 | boolean | RECOMMEND ENABLED otherwise Unbound answers to any attached address regardless of query in-address. | interface-automatic: |
| listen_port | 53 | port | Inbound port where Unbound will listen for queries. | port: |
| localservice | 1 | boolean | Prevent DNS amplification attacks. Only answer to subnets this machine has interfaces on. | access-control: |
| manual_conf | 0 | boolean | Skip all this UCI nonsense. Manually edit the configuration in `/etc/unbound/unbound.conf`. | - |
| num_threads | 1 | threads | Enable multithreading. Two are supported with only one cache slab. More becomes an industrial setup, and UCI simplificaitons may not be appropriate. | num-threads: |
| protocol | mixed | state | Limit Unbound protocols for recursion or forwarding.<br>`ip4_only`: old fashioned IPv4 upstream and downstream<br>`ip6_only`: test environment only; could cauase problems<br>`ip6_local`: upstream IPv4 only and local network IPv4 and IPv6<br>`ip6_prefer`: both IPv4 and IPv6 but try IPv6 first<br>`mixed`: both IPv4 and IPv6<br>`default`: built-in defaults | do-ip4: do-ip6: prefer-ip6: interface: |
| query_minimize | 0 | boolean | Enable a minor privacy option. Query one domain piece at a time (dot separator). | qname-minimisation: |
| query_min_strict | 0 | boolean | Query minimize may fall back to normal. This prevents the fall back, but non-standard name servers will fail. | qname-minimisation-strict: |
| rate_limit | 0 | query/s | Limit the total number of queries and queries per client by half that. Disabled by setting 0. | ratelimit: ip-ratelimit: |
| rebind_localhost | 0 | boolean | Prevent loopback addresses `127.0.0.0/8` or `::1` in upstream responses. They could be a good black hole server or a spring board attack. | private-address: |
| rebind_protection | 1 | level | Prevent your local addresses from being allowed in upstream responses. They could be a spring board attack.<br>`0`: Disabled<br>`1`: Only RFC 1918 and 4193 responses blocked<br>`2`: Above plus GLA /64 on machine<br>`3`: Above plus DHCP-PD passed down (not implemented) | private-address: |
| recursion | passive | state | Unbound has many options for recrusion but UCI is bundled for simplicity.<br>`passive`: slower until cache fills but kind on CPU load<br>`default`: built-in defaults<br>`aggressive`: uses prefetching to handle more requests quickly | (many) |
| resource | small | state | Unbound has many options for memory resources but UCI is bundled for simplicity.<br>`tiny`: similar to published memory restricted configuration<br>`small`: about half of medium<br>`medium`: similar to default<br>`default`: built-in defaults<br>`large`: about double of medium | \*-cache-size: |
| root_age | 9 | day | >90 Disables. Age limit for root data like root DNSSEC key. Scripts will copy from `tmps` to flash ROM with this limit to save write life. | - |
| trigger_interface | lan wan | interface | **List** interfaces to watch IFUP to restart Unbound. This works around `netifd` and `procd` hyper activity with WAN DHCPv6 (else restart each 2-3 minutes). | - |
| ttl_min | 120 | second | Minimum TTL in cache to avoid abused low TTL for snoop-vertising and non-standard load balancing. Typical to configure maybe 0~300 but 1800 is the maximum accepted. | cache-min-ttl: |
| unbound_control | 0 | level | Enables `unbound-control` application access ports.<br>`0`: None else add your own in unbound_ext.conf<br>`1`: Unencrypted Local Host Access<br>`2`: SSL Local Host Access w/ auto unbound-control-setup<br>`3`: SSL Network Access w/ auto unbound-control-setup<br>`4`: SSL Network Access; static key/pem files must already exist | unbound-control: ... (clause) |
| validator_ntp | 1 | boolean | Disable DNSSEC time checks at boot and restart when NTP locks in time. DNSSEC requires time validation and this breaks the chicken and egg. | - |
Confingure any mix of Unbound `forward-zone:`, `stub-zone:`, or `auth-zone:` clauses. These sections are more compact than Unbound and will unroll into Unbound's configuration syntax.
| UCI | Default | Units | Description | Unbound |
| --- | ------- | ----- | ----------- | ------- |
| dns_assist | none | program | Check against local host forwarding by requiring a target program to exist and be enabled else do not permit forwarding `127.0.0.0/8` or `::1`. Includes bind, dnsmasq, ipset-dns, and nsd. | forward-addr: |
| enabled | 0 | boolean | turn zone on or off without deleting it | - |
| fallback | 1 | boolean | Allow this zone to fall through to other zones or recursion. | forward-first: |
| port | 53 | port | Target server's target port for plain DNS operations. | (auto 192.0.2.53 \#53)
| resolv_conf | 0 | boolean | Use resolv.conf servers as it was filled by the DHCP client. For example your ISP services (mail.example.net) or co-located services (streamed-movies.example.com). | - |
| server | (empty) | address domain | Required **list** to target servers. Full form is accepted but not required `192.0.2.53#53@dns.exmple.net`. Stub zones must use an IP address. | master: forward-host: forward-addr: stub-addr: |
| tls_index | (empty) | domain | TLS certifiicated signature index. If ommitted, Unbound encrypts but does not validate. | (auto 192.0.2.53 \#853 \@dns.example.net) |
| tls_port | 853 | port | Target server's target port for TLS DNS operations. | (auto 192.0.2.53 \#853) |
| tls_upstream | 0 | boolean | Use TLS to contact the zone server. | forward-tls-upstream: |
| url_dir | (empty) | string | Directory only path by http or https to get authoritative zone files. | url: |
| zone_name | (empty) | domain | Required **list** to select domains subject to this zone section. You can forward the root `.` zone or just your organizaiton `example.com.` | name: |
| zone_type | (empty) | state | Required option to create an Unbound zone clause.<br>`auth_zone`: prefetch whole zones from authoritative server<br>`forward_zone`: forward queries by domain name (like dnsmasq)<br>`stub_zone`: direct authoritative lookup by domain name | auth-zone: forward-zone: stub-zone: ... (clauses) |
Eric Luehrsen
4 years ago