hosts/mermet/unbound.nix

   1 { pkgs, lib, config, host, ... }:
   2 let
   3   inherit (config.services) unbound;
   4   inherit (config.users) users;
   5 in
   6 {
   7 networking.resolvconf.useLocalResolver = true;
   8 # Avoid: warning: so-rcvbuf 1048576 was not granted. Got 425984.
   9 # To fix: start with root permissions(linux)
  10 # or sysctl bigger net.core.rmem_max(linux)
  11 # or kern.ipc.maxsockbuf(bsd) values.
  12 boot.kernel.sysctl."net.core.rmem_max" = 1048576;
  13 services.unbound = {
  14   enable = true;
  15   # DOC: https://calomel.org/unbound_dns.html
  16   settings = {
  17     remote-control = {
  18       control-enable = true;
  19       control-interface = "/run/unbound/unbound.socket";
  20     };
  21     server = {
  22       log-queries = false;
  23       verbosity = 1;
  24       interface = [
  25         "127.0.0.1"
  26         "::1"
  27       ];
  28       access-control = [
  29         "0.0.0.0/0 refuse"
  30         "::0/0 refuse"
  31         "127.0.0.0/8 allow"
  32         "::1 allow"
  33       ];
  34       prefer-ip4 = !config.networking.enableIPv6;
  35       port = 53;
  36
  37       # The file which contains the listing of primary root DNS servers.
  38       # To be updated once every six months.
  39       root-hints = "/var/lib/unbound/named.root";
  40
  41       # Do no answer id.server and hostname.bind queries.
  42       hide-identity = true;
  43       # Do not answer version.server and version.bind queries.
  44       hide-version = true;
  45
  46       # Will trust glue only if it is within the servers authority.
  47       # Harden against out of zone rrsets, to avoid spoofing attempts.
  48       # Hardening queries multiple name servers for the same data to make
  49       # spoofing significantly harder and does not mandate dnssec.
  50       harden-glue = true;
  51
  52       # Require DNSSEC data for trust-anchored zones, if such data is absent, the
  53       # zone becomes  bogus.  Harden against receiving dnssec-stripped data. If you
  54       # turn it off, failing to validate dnskey data for a trustanchor will trigger
  55       # insecure mode for that zone (like without a trustanchor).  Default on,
  56       # which insists on dnssec data for trust-anchored zones.
  57       harden-dnssec-stripped = true;
  58
  59       # Use 0x20-encoded random bits in the query to foil spoof attempts.
  60       # http://tools.ietf.org/html/draft-vixie-dnsext-dns0x20-00
  61       #
  62       # When Unbound sends a query to a remote server it sends the hostname
  63       # string in random upper and lower characters. The remote server must
  64       # resolve the hostname as if all the characters were lower case. The remote
  65       # server must then send the query back to Unbound in the same random upper
  66       # and lower characters that Unbound sent. If the characters of the hostname
  67       # in the response are in the same format as the query then the dns-0x20
  68       # check is satisfied.
  69       # Attackers hoping to poison a Unbound DNS cache must therefore guess the
  70       # mixed-case encoding of the query and the timing of the return dns answer
  71       # in addition to all other fields required in a DNS poisoning attack.
  72       # dns-0x20 increases the difficulty of the attack significantly.
  73       #
  74       # It may result in maybe 0.4% of domains getting no answers
  75       # due to no support on the authoritative server side
  76       use-caps-for-id = true;
  77
  78       #cache-min-ttl = 3600;
  79       cache-max-ttl = 86400;
  80
  81       # Perform prefetching of close to expired message cache entries.  If a client
  82       # requests the dns lookup and the TTL of the cached hostname is going to
  83       # expire in less than 10% of its TTL, unbound will (1st) return the IP of the
  84       # host to the client and (2nd) pre-fetch the DNS request from the remote DNS server.
  85       # This method has been shown to increase the amount of cached hits by
  86       # local clients by 10% on average.
  87       prefetch = true;
  88
  89       # Number of threads to create. 1 disables threading.
  90       # This should equal the number of CPU cores in the host.
  91       num-threads = host.CPUs;
  92
  93       # The number of slabs to use for cache and must be a power of 2 times the
  94       # number of num-threads set above. more slabs reduce lock contention,
  95       # but fragment memory usage.
  96       msg-cache-slabs = 8;
  97       rrset-cache-slabs = 8;
  98       infra-cache-slabs = 8;
  99       key-cache-slabs = 8;
 100
 101       # Increase the memory size of the cache. Use roughly twice as much rrset cache
 102       # memory as you use msg cache memory. Due to malloc overhead, the total memory
 103       # usage is likely to rise to double (or 2.5x) the total cache memory.
 104       rrset-cache-size = "32m";
 105       msg-cache-size = "16m";
 106
 107       # buffer size for UDP port 53 incoming (SO_RCVBUF socket option). This sets
 108       # the kernel buffer larger so that no messages are lost in spikes in the traffic.
 109       so-rcvbuf = "1m";
 110
 111       # Enforce privacy of these addresses. Strips them away from answers.
 112       # It may cause DNSSEC validation to additionally mark it as bogus.
 113       # Protects against 'DNS Rebinding' (uses browser as network proxy).
 114       #  Only 'private-domain' and 'local-data' names are allowed
 115       # to have these private addresses. No default.
 116       private-address = [
 117         "192.168.0.0/16"
 118         "172.16.0.0/12"
 119         "10.0.0.0/8"
 120       ];
 121
 122       # Allow the domain (and its subdomains) to contain private addresses.
 123       # local-data statements are allowed to contain private addresses too.
 124       #private-domain = "home.lan";
 125
 126       # If nonzero, unwanted replies are not only reported in statistics, but also
 127       # a running total is kept per thread. If it reaches the threshold, a warning
 128       # is printed and a defensive action is taken, the cache is cleared to flush
 129       # potential poison out of it.  A suggested value is 10000000, the default is
 130       # 0 (turned off). calomel.org thinks 10K is a good value.
 131       unwanted-reply-threshold = 10000;
 132
 133       # IMPORTANT FOR TESTING: If you are testing and setup NSD or BIND on
 134       # localhost you will want to allow the resolver to send queries to localhost.
 135       # Make sure to set do-not-query-localhost = true;.
 136       do-not-query-localhost = true;
 137
 138       # Should additional section of secure message also be kept clean of unsecure
 139       # data. Useful to shield the users of this validator from potential bogus
 140       # data in the additional section. All unsigned data in the additional section
 141       # is removed from secure messages.
 142       val-clean-additional = true;
 143     };
 144   };
 145 };
 146 networking.nftables.ruleset = ''
 147   table inet filter {
 148     chain output-net {
 149       skuid ${users.unbound.name} \
 150         meta l4proto { udp, tcp } th dport domain \
 151         counter accept comment "unbound"
 152     }
 153   }
 154 '';
 155 systemd.services.unbound = {
 156   serviceConfig = {
 157     #RuntimeDirectoryMode = "0700";
 158     BindReadOnlyPaths = [
 159      "${../../networking/named.root}:/var/lib/unbound/named.root"
 160     ];
 161   };
 162 };
 163 }