137 lines
4.6 KiB
Bash
Executable File
137 lines
4.6 KiB
Bash
Executable File
#!/bin/bash
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# DNS
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# -----------------------------------------------
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# This script installs packages, but the DNS zone files are only
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# created by the /dns/update API in the management server because
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# the set of zones (domains) hosted by the server depends on the
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# mail users & aliases created by the user later.
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source setup/functions.sh # load our functions
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source /etc/mailinabox.conf # load global vars
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# Install the packages.
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#
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# * nsd: The non-recursive nameserver that publishes our DNS records.
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# * ldnsutils: Helper utilities for signing DNSSEC zones.
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# * openssh-client: Provides ssh-keyscan which we use to create SSHFP records.
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echo "Installing nsd (DNS server)..."
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apt_install nsd ldnsutils openssh-client
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# Prepare nsd's configuration.
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mkdir -p /var/run/nsd
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cat > /etc/nsd/nsd.conf << EOF;
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# Do not edit. Overwritten by Mail-in-a-Box setup.
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server:
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hide-version: yes
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# identify the server (CH TXT ID.SERVER entry).
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identity: ""
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# The directory for zonefile: files.
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zonesdir: "/etc/nsd/zones"
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# Allows NSD to bind to IP addresses that are not (yet) added to the
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# network interface. This allows nsd to start even if the network stack
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# isn't fully ready, which apparently happens in some cases.
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# See https://www.nlnetlabs.nl/projects/nsd/nsd.conf.5.html.
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ip-transparent: yes
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EOF
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# Since we have bind9 listening on localhost for locally-generated
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# DNS queries that require a recursive nameserver, and the system
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# might have other network interfaces for e.g. tunnelling, we have
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# to be specific about the network interfaces that nsd binds to.
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for ip in $PRIVATE_IP $PRIVATE_IPV6; do
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echo " ip-address: $ip" >> /etc/nsd/nsd.conf;
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done
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echo "include: /etc/nsd/zones.conf" >> /etc/nsd/nsd.conf;
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# Create DNSSEC signing keys.
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mkdir -p "$STORAGE_ROOT/dns/dnssec";
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# TLDs don't all support the same algorithms, so we'll generate keys using a few
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# different algorithms. RSASHA1-NSEC3-SHA1 was possibly the first widely used
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# algorithm that supported NSEC3, which is a security best practice. However TLDs
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# will probably be moving away from it to a a SHA256-based algorithm.
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#
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# Supports `RSASHA1-NSEC3-SHA1` (didn't test with `RSASHA256`):
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#
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# * .info
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# * .me
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#
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# Requires `RSASHA256`
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#
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# * .email
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# * .guide
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#
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# Supports `RSASHA256` (and defaulting to this)
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#
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# * .fund
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FIRST=1 #NODOC
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for algo in RSASHA1-NSEC3-SHA1 RSASHA256; do
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if [ ! -f "$STORAGE_ROOT/dns/dnssec/$algo.conf" ]; then
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if [ $FIRST == 1 ]; then
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echo "Generating DNSSEC signing keys..."
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FIRST=0 #NODOC
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fi
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# Create the Key-Signing Key (KSK) (with `-k`) which is the so-called
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# Secure Entry Point. The domain name we provide ("_domain_") doesn't
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# matter -- we'll use the same keys for all our domains.
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#
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# `ldns-keygen` outputs the new key's filename to stdout, which
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# we're capturing into the `KSK` variable.
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#
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# ldns-keygen uses /dev/random for generating random numbers by default.
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# This is slow and unecessary if we ensure /dev/urandom is seeded properly,
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# so we use /dev/urandom. See system.sh for an explanation. See #596, #115.
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KSK=$(umask 077; cd $STORAGE_ROOT/dns/dnssec; ldns-keygen -r /dev/urandom -a $algo -b 2048 -k _domain_);
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# Now create a Zone-Signing Key (ZSK) which is expected to be
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# rotated more often than a KSK, although we have no plans to
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# rotate it (and doing so would be difficult to do without
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# disturbing DNS availability.) Omit `-k` and use a shorter key length.
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ZSK=$(umask 077; cd $STORAGE_ROOT/dns/dnssec; ldns-keygen -r /dev/urandom -a $algo -b 1024 _domain_);
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# These generate two sets of files like:
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#
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# * `K_domain_.+007+08882.ds`: DS record normally provided to domain name registrar (but it's actually invalid with `_domain_`)
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# * `K_domain_.+007+08882.key`: public key
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# * `K_domain_.+007+08882.private`: private key (secret!)
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# The filenames are unpredictable and encode the key generation
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# options. So we'll store the names of the files we just generated.
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# We might have multiple keys down the road. This will identify
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# what keys are the current keys.
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cat > $STORAGE_ROOT/dns/dnssec/$algo.conf << EOF;
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KSK=$KSK
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ZSK=$ZSK
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EOF
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fi
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# And loop to do the next algorithm...
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done
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# Force the dns_update script to be run every day to re-sign zones for DNSSEC
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# before they expire. When we sign zones (in `dns_update.py`) we specify a
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# 30-day validation window, so we had better re-sign before then.
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cat > /etc/cron.daily/mailinabox-dnssec << EOF;
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#!/bin/bash
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# Mail-in-a-Box
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# Re-sign any DNS zones with DNSSEC because the signatures expire periodically.
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`pwd`/tools/dns_update
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EOF
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chmod +x /etc/cron.daily/mailinabox-dnssec
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# Permit DNS queries on TCP/UDP in the firewall.
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ufw_allow domain
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