servers/mermet/unbound.nix

   1 { pkgs, lib, config, ... }:
   2 let inherit (config) users; in
   3 {
   4   networking.resolvconf.useLocalResolver = true;
   5   services.unbound = {
   6     enable = true;
   7     # DOC: https://calomel.org/unbound_dns.html
   8     extraConfig = ''
   9       port: 53
  10       verbosity: 1
  11
  12       # The file which contains the listing of primary root DNS servers.
  13       # To be updated once every six months.
  14       root-hints: /var/lib/unbound/named.root
  15
  16       # Do no answer id.server and hostname.bind queries.
  17       hide-identity: yes
  18       # Do not answer version.server and version.bind queries.
  19       hide-version: yes
  20
  21       # Will trust glue only if it is within the servers authority.
  22       # Harden against out of zone rrsets, to avoid spoofing attempts.
  23       # Hardening queries multiple name servers for the same data to make
  24       # spoofing significantly harder and does not mandate dnssec.
  25       harden-glue: yes
  26
  27       # Require DNSSEC data for trust-anchored zones, if such data is absent, the
  28       # zone becomes  bogus.  Harden against receiving dnssec-stripped data. If you
  29       # turn it off, failing to validate dnskey data for a trustanchor will trigger
  30       # insecure mode for that zone (like without a trustanchor).  Default on,
  31       # which insists on dnssec data for trust-anchored zones.
  32       harden-dnssec-stripped: yes
  33
  34       # Use 0x20-encoded random bits in the query to foil spoof attempts.
  35       # http://tools.ietf.org/html/draft-vixie-dnsext-dns0x20-00
  36       #
  37       # When Unbound sends a query to a remote server it sends the hostname
  38       # string in random upper and lower characters. The remote server must
  39       # resolve the hostname as if all the characters were lower case. The remote
  40       # server must then send the query back to Unbound in the same random upper
  41       # and lower characters that Unbound sent. If the characters of the hostname
  42       # in the response are in the same format as the query then the dns-0x20
  43       # check is satisfied.
  44       # Attackers hoping to poison a Unbound DNS cache must therefore guess the
  45       # mixed-case encoding of the query and the timing of the return dns answer
  46       # in addition to all other fields required in a DNS poisoning attack.
  47       # dns-0x20 increases the difficulty of the attack significantly.
  48       #
  49       # It may result in maybe 0.4% of domains getting no answers
  50       # due to no support on the authoritative server side
  51       use-caps-for-id: yes
  52
  53       #cache-min-ttl: 3600
  54       cache-max-ttl: 86400
  55
  56       # Perform prefetching of close to expired message cache entries.  If a client
  57       # requests the dns lookup and the TTL of the cached hostname is going to
  58       # expire in less than 10% of its TTL, unbound will (1st) return the IP of the
  59       # host to the client and (2nd) pre-fetch the DNS request from the remote DNS server.
  60       # This method has been shown to increase the amount of cached hits by
  61       # local clients by 10% on average.
  62       prefetch: yes
  63
  64       # Number of threads to create. 1 disables threading.
  65       # This should equal the number of CPU cores in the machine.
  66       num-threads: 4
  67
  68       # The number of slabs to use for cache and must be a power of 2 times the
  69       # number of num-threads set above. more slabs reduce lock contention,
  70       # but fragment memory usage.
  71       msg-cache-slabs: 8
  72       rrset-cache-slabs: 8
  73       infra-cache-slabs: 8
  74       key-cache-slabs: 8
  75
  76       # Increase the memory size of the cache. Use roughly twice as much rrset cache
  77       # memory as you use msg cache memory. Due to malloc overhead, the total memory
  78       # usage is likely to rise to double (or 2.5x) the total cache memory.
  79       rrset-cache-size: 32m
  80       msg-cache-size: 16m
  81
  82       # buffer size for UDP port 53 incoming (SO_RCVBUF socket option). This sets
  83       # the kernel buffer larger so that no messages are lost in spikes in the traffic.
  84       so-rcvbuf: 1m
  85
  86       # Enforce privacy of these addresses. Strips them away from answers.
  87       # It may cause DNSSEC validation to additionally mark it as bogus.
  88       # Protects against 'DNS Rebinding' (uses browser as network proxy).
  89       #  Only 'private-domain' and 'local-data' names are allowed
  90       # to have these private addresses. No default.
  91       private-address: 192.168.0.0/16
  92       private-address: 172.16.0.0/12
  93       private-address: 10.0.0.0/8
  94
  95       # Allow the domain (and its subdomains) to contain private addresses.
  96       # local-data statements are allowed to contain private addresses too.
  97       #private-domain: "home.lan"
  98
  99       # If nonzero, unwanted replies are not only reported in statistics, but also
 100       # a running total is kept per thread. If it reaches the threshold, a warning
 101       # is printed and a defensive action is taken, the cache is cleared to flush
 102       # potential poison out of it.  A suggested value is 10000000, the default is
 103       # 0 (turned off). calomel.org thinks 10K is a good value.
 104       unwanted-reply-threshold: 10000
 105
 106       # IMPORTANT FOR TESTING: If you are testing and setup NSD or BIND on
 107       # localhost you will want to allow the resolver to send queries to localhost.
 108       # Make sure to set do-not-query-localhost: yes.
 109       do-not-query-localhost: no
 110
 111       # Should additional section of secure message also be kept clean of unsecure
 112       # data. Useful to shield the users of this validator from potential bogus
 113       # data in the additional section. All unsigned data in the additional section
 114       # is removed from secure messages.
 115       val-clean-additional: yes
 116     '';
 117   };
 118   systemd.services.unbound.preStart = ''
 119     install -m 444 -o unbound -g nogroup \
 120      ${../../config/dns/named.root} \
 121      /var/lib/unbound/named.root
 122   '';
 123 }