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# DNS récursif Ouvert DoH DoT & haute disponibilité

**45.67.81.23 - dns.aquilenet.fr**

On propos un DNS récursif ouvert cf https://www.aquilenet.fr/services/dns/ https://dns.aquilenet.fr/

On a mis aussi un DNS ouvert sur l'IP 45.67.81.23 car facile à retenir, avec l'adresse de dns.aquilenet.fr (voir [http://dns.aquilenet.fr](http://dns.aquilenet.fr)) . Nous en avons profité pour ajouter [DoH](https://fr.wikipedia.org/wiki/DNS_over_HTTPS) et [DoT](https://fr.wikipedia.org/wiki/DNS_over_TLS) et d'avoir cette adresse en IP Virtuelle partagée entre pan1 et pan2.

Cette IP virtuelle est portée par Keepalived sur pan1 le primaire et pan2 le secondaire. Si le démon Keepalived est arrêté sur pan1, l'ip bascule sur pan2. Si on redémarre le démon sur pan1, ce dernier reprend l'IP: pratique pour les mises à jour, le service continue à fonctionner.

Pan[1|2] portent l'ip 45.67.81.23 gracieusement offerte par les copains de https://yaal.coop/fr un vlan est dédié sur ce réseau de l'hyperviseur.

## Configurations communes à pan1 et pan2

### Nginx

* /etc/nginx/sites-enabled/default

~~~

server {

    listen       45.67.81.23:80 ;

    listen       [::]:80 ;

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

    location / {

        return 301 https://dns.aquilenet.fr;

        }

    server_name dns.aquilenet.fr; # managed by Certbot

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

}

server {

    listen       45.67.81.23:443 ssl http2;

    listen       [::]:443 ssl http2;

    root /var/www/dns.aquilenet.fr;

    index index.htm;

    ssl_certificate     /etc/unbound/ssl/dns.aquilenet.fr/fullchain.pem;

    ssl_certificate_key /etc/unbound/ssl/dns.aquilenet.fr/privkey.pem;

location /dns-query {

    grpc_pass grpc://127.0.0.1:443;

        }

}

root@pan1:/etc/unbound/ssl# vi /var/www/dns.aquilenet.fr/index.htm 

root@pan1:/etc/unbound/ssl# ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000

    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

    inet 127.0.0.1/8 scope host lo

       valid_lft forever preferred_lft forever

    inet6 ::1/128 scope host noprefixroute 

       valid_lft forever preferred_lft forever

2: enX0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000

    link/ether 00:16:3e:01:01:21 brd ff:ff:ff:ff:ff:ff

    inet 45.67.81.21/24 brd 45.67.81.255 scope global enX0

       valid_lft forever preferred_lft forever

    inet 45.67.81.23/32 scope global enX0

       valid_lft forever preferred_lft forever

    inet6 fe80::216:3eff:fe01:121/64 scope link 

       valid_lft forever preferred_lft forever

root@pan1:/etc/unbound/ssl# vi /var/www/dns.aquilenet.fr/index.htm 

root@pan1:/etc/unbound/ssl# vi /var/www/dns.aquilenet.fr/index.htm 

root@pan1:/etc/unbound/ssl# vi /var/www/dns.aquilenet.fr/index.htm 

root@pan1:/etc/unbound/ssl# vi /var/www/dns.aquilenet.fr/index.htm 

root@pan1:/etc/unbound/ssl# cat /etc/nginx/sites-enabled/default 

server {

    listen       45.67.81.23:80 ;

    listen       [::]:80 ;

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

    location / {

        return 301 https://dns.aquilenet.fr;

        }

    server_name dns.aquilenet.fr; # managed by Certbot

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

}

server {

    listen       45.67.81.23:443 ssl http2;

    listen       [::]:443 ssl http2;

    root /var/www/dns.aquilenet.fr;

    index index.htm;

    ssl_certificate     /etc/unbound/ssl/dns.aquilenet.fr/fullchain.pem;

    ssl_certificate_key /etc/unbound/ssl/dns.aquilenet.fr/privkey.pem;

location /dns-query {

    grpc_pass grpc://127.0.0.1:443;

        }

}

~~~

### Unbound

~~~

server {

    listen       45.67.81.23:80 ;

    listen       [::]:80 ;

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

    location / {

        return 301 https://dns.aquilenet.fr;

        }

    server_name dns.aquilenet.fr; # managed by Certbot

    location ~ /.well-known/acme-challenge {

        allow all;

        root /var/www/letsencrypt;

    }

}

server {

    listen       45.67.81.23:443 ssl http2;

    listen       [::]:443 ssl http2;

    root /var/www/dns.aquilenet.fr;

    index index.htm;

    ssl_certificate     /etc/unbound/ssl/dns.aquilenet.fr/fullchain.pem;

    ssl_certificate_key /etc/unbound/ssl/dns.aquilenet.fr/privkey.pem;

location /dns-query {

    grpc_pass grpc://127.0.0.1:443;

        }

}

root@pan1:/etc/unbound/ssl# cat /etc/unbound/unbound

cat: /etc/unbound/unbound: Aucun fichier ou dossier de ce type

root@pan1:/etc/unbound/ssl# cat /etc/unbound/unbound.conf

include-toplevel: "/etc/unbound/unbound.conf.d/*.conf"

server:

    verbosity: 1 

    access-control: 0.0.0.0/0 allow 

    interface: 45.67.81.23

#    interface: 45.67.81.23@443

    interface: 45.67.81.23@853

http-notls-downstream: yes

    interface: 127.0.0.1@443

    port: 53

    tls-port: 853

    https-port: 443

    root-hints: "/usr/share/dns/root.hints"

    harden-glue: yes

    harden-large-queries: yes

    harden-dnssec-stripped: yes

    harden-below-nxdomain: yes

    harden-referral-path: yes

    harden-algo-downgrade: no # false positives with improperly configured zones

    use-caps-for-id: no # makes lots of queries fail

    edns-buffer-size: 1232

    rrset-roundrobin: yes

    cache-min-ttl: 300

    cache-max-ttl: 86400

    serve-expired: yes

    harden-algo-downgrade: yes

    harden-short-bufsize: yes

    hide-identity: yes

    identity: "dns.aquilenet.fr"

    hide-version: yes

    do-daemonize: no

    neg-cache-size: 4m

    qname-minimisation: yes

    deny-any: yes

    minimal-responses: yes

    prefetch: yes

    prefetch-key: yes

    num-threads: 2 

    msg-cache-size: 50m

    rrset-cache-size: 100m

    so-reuseport: yes

    so-rcvbuf: 4m

    so-sndbuf: 4m

    unwanted-reply-threshold: 100000

    log-queries: no

    log-replies: no

    log-servfail: no

    log-local-actions: no

    logfile: /dev/null

    # imposer la QNAME minimisation (RFC 7816)

    qname-minimisation: yes

    # même si le serveur faisant autorité ne le veut pas

    #   après discussion, il est possible que cette option ne soit

    #   pas recommandée dans le cadre d'un résolveur ouvert

    qname-minimisation-strict: yes

   # DoH

   tls-service-key: "/etc/letsencrypt/live/dns.aquilenet.fr/privkey.pem"

   tls-service-pem: "/etc/letsencrypt/live/dns.aquilenet.fr/cert.pem"

~~~

### AppArmor

*  /etc/apparmor.d/usr.sbin.unbound

décomenter:

  include <local/usr.sbin.unbound>

* /etc/apparmor.d/local/usr.sbin.unbound

~~~

/etc/letsencrypt/archive/** r,

/etc/letsencrypt/live/** r,

~~~

appliquer avec: `apparmor_parser -r /etc/apparmor.d/usr.sbin.unbound`

### Iptables

~~~

*filter

:INPUT DROP

:FORWARD DROP

:OUTPUT ACCEPT

-A INPUT ! -i lo -s 127.0.0.0/8 -j DROP

-A INPUT -s 0.0.0.0 -i eth0 -j DROP

-A INPUT -d 0.0.0.0 -i eth0 -j DROP

-A INPUT -s 255.255.255.255 -i eth0 -j DROP

-A INPUT -d 255.255.255.255 -i eth0 -j DROP

-A INPUT -m conntrack --ctstate INVALID -j DROP

-A INPUT -p tcp -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

-A INPUT -p udp ! --dport 53 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

-A INPUT -i lo -j ACCEPT

-A OUTPUT -o lo -j ACCEPT

# SSH no more 10 attempts in 3 min

-A INPUT -i eth0 -p tcp --dport 55555 -m recent --name SSH --update --hitcount 10 --seconds 180 -j DROP

-A INPUT -i eth0 -p tcp --dport 55555 -m recent --name SSH --set -j ACCEPT

# Web

-A INPUT -p tcp --dport 80 -j ACCEPT

# smtp

-A INPUT -i eth0 -p tcp --dport 25 -j ACCEPT

# smtps

-A INPUT -i eth0 -p tcp --dport 465 -j ACCEPT

# submission

-A INPUT -i eth0 -p tcp --dport 587 -j ACCEPT

# DNS

# récursif, lisible par nos abonnés seulement

-N dns_limit

-A dns_limit -s 185.233.100.0/22 -j ACCEPT

-A INPUT -d 45.67.81.23 -p tcp -m tcp --dport 53 -j dns_limit

-A INPUT -d 45.67.81.23 -p udp -m udp --dport 53 -j dns_limit

-A INPUT -d 45.67.81.23 -p tcp -m tcp --dport 443 -j dns_limit

-A INPUT -d 45.67.81.23 -p tcp -m tcp --dport 853 -j dns_limit

# mais aussi par le reste d'Internet, mais en rate-limit

-A dns_limit -m string --algo bm --hex-string "|00 00 ff 00 01|" --from 28 -m hashlimit --hashlimit-above 1/sec --hashlimit-burst 2 --hashlimit-mode srcip --hashlimit-name RL-DNS-ANY-v4 --hashlimit-srcmask 28 -m comment --comment "RATE-LIMIT DNS ANY QTYPE 1/s burst 2" -j DROP

-A dns_limit -m string --algo bm --hex-string "|00 00 ff 00 01|" --from 28 -m hashlimit --hashlimit-above 20/min --hashlimit-mode srcip --hashlimit-name RL-DNS-ANY-v4-LOG --hashlimit-srcmask 28 -m comment --comment "RATE-LIMIT DNS ANY QTYPE 20/min" -j LOG --log-prefix "DNS-FLOOD "

-A dns_limit -m hashlimit --hashlimit-above 10/sec --hashlimit-burst 100 --hashlimit-mode srcip --hashlimit-name DNS --hashlimit-srcmask 28 -m comment --comment "RATE-LIMIT DNS 10/src burst 100" -j DROP

-A dns_limit -j ACCEPT

# ICMP

-A INPUT -p icmp -j ACCEPT

-A INPUT -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT

# NRPE

-A INPUT -s 185.233.100.230 -p tcp --dport 5666 -j ACCEPT

# Keepalived

-A INPUT -s 45.67.81.0/24 -p vrrp -j ACCEPT

COMMIT

~~~

## Configurations spécifiques

### Génération du certificat SSL sur Hades

~~~

certbot --apache --agree-tos --email sysop@aquilenet.fr -d dns.aquilenet.fr

chgrp bind /etc/letsencrypt/live/dns.aquilenet.fr/privkey.pem

chmod 0640 /etc/letsencrypt/live/dns.aquilenet.fr/privkey.pem

openssl dhparam -out /etc/bind/dhparam.pem 4096

~~~

Copie du certificat sur gaia

* /etc/letsencrypt/renewal-hooks/post/sync-cert.sh

#!/bin/bash

rsync -aPHSA /etc/letsencrypt/archive/dns.aquilenet.fr gaia:/etc/letsencrypt/archive/

~~~

### Clée sdns (auth par épinglage de la clé / key pining)

* A partir de la clé

~~~

hades|19:21:08|:~# openssl rsa -in /etc/letsencrypt/live/dns.aquilenet.fr/privkey.pem -outform der -pubout | openssl dgst -sha256 -binary | openssl enc -base64

writing RSA key

lBk09CRIPJ+J4O9rmbvJkEiGYoH5r9rxOIQdxkYxyII=

~~~

* ou à partir du certificat

~~~

hades|19:22:21|:~# openssl x509 -in /etc/letsencrypt/live/dns.aquilenet.fr/cert.pem -pubkey -noout | openssl rsa -pubin -outform der | openssl dgst -sha256 -binary | openssl enc -base64

writing RSA key

lBk09CRIPJ+J4O9rmbvJkEiGYoH5r9rxOIQdxkYxyII=

~~~

### Keepalived

#### Hades Master

* /etc/keepalived/keepalived.conf

~~~

global_defs {

  notification_email {

    sysop@aquilenet.fr

  }

  notification_email_from vrrp-dns@aquilenet.fr.fr

  smtp_server localhost

  smtp_connect_timeout 30

}

vrrp_instance DNS {

  state MASTER 

  interface eth0

  virtual_router_id 101 

  priority 100

  advert_int 2

  smtp_alert

  unicast_src_ip 185.233.100.16 

  unicast_peer {

    185.233.100.2

  }

  virtual_ipaddress {

    45.67.81.23/32 dev eth1 scope global # VIP

  }

}

~~~

#### Gaia Slave

* /etc/keepalived/keepalived.conf

~~~

global_defs {

  notification_email {

    sysop@aquilenet.fr

  }

  notification_email_from vrrp-dns@aquilenet.fr.fr

  smtp_server localhost

  smtp_connect_timeout 30

}

vrrp_instance DNS {

  state BACKUP

  interface eth0

  virtual_router_id 101

  priority 50

  advert_int 2

  smtp_alert

  unicast_src_ip 185.233.100.2

  unicast_peer {

    185.233.100.16

  }

  virtual_ipaddress {

    45.67.81.23/32 dev eth1 scope global # VIP

  }

}

~~~

## Validation

* test du service

~~~

dig +short dns.aquilenet.fr @45.67.81.23 

45.67.81.23

dig +https +short dns.aquilenet.fr @45.67.81.23      

45.67.81.23

dig +tls +short dns.aquilenet.fr @45.67.81.23      

45.67.81.23

~~~

* bascule keepalived

sur hades: `systemctl stop keepalived`

sur gaia: `ip a |grep /32`doit donner "inet 45.67.81.23/32 scope global eth1"

http://dns.aquilenet.fr/host permet de savoir quel est le serveur qui porte l'IP virtuelle

## Indexes de serveurs DNS ouverts:

https://github.com/curl/curl/wiki/DNS-over-HTTPS#publicly-available-servers <= fait

https://diyisp.org/dokuwiki/doku.php?id=technical:dnsresolver <= fait

https://diyisp.org/dokuwiki/doku.php?id=technical:dnsresolver <= fait

https://dnsprivacy.org/public_resolvers/

## Ressources

https://www.bortzmeyer.org/doh-bortzmeyer-fr-policy.html

https://www.bortzmeyer.org/7858.html

https://kb.isc.org/docs/aa-01386