Bind: “nsupdate -l” failed with status “update failed: REFUSED”

bindddnsdomain-name-systemdynamic-dnsnsupdate

I just switched to bind 9.9.5 dynamic DNS feature with semi-automatic management of DNSSEC entries, the whole process went good and my zone files were updated well, but now I can't update or add entries via nsupdate tool.

The /etc/bind/named.conf.local:

// 1
view "localhost_view" {
    
    allow-query-on { 127.0.0.1; };
    allow-query { localhost_acl; };
    match-clients { localhost_acl; };

    zone "somehost.tld" {
            type master;
            file "/etc/bind/db.somehost.tld_10";
    };

    zone "168.192.in-addr.arpa" {
            type master;
            notify no;
            file "/etc/bind/db.192.168.10";
    };

    // formerly named.conf.default-zones

        zone "." {
                type hint;
                file "/etc/bind/db.root";
        };

        zone "localhost" {
                type master;
                file "/etc/bind/db.local";
        };

        zone "127.in-addr.arpa" {
                type master;
                file "/etc/bind/db.127";
        };

        zone "0.in-addr.arpa" {
                type master;
                file "/etc/bind/db.0";
        };

        zone "255.in-addr.arpa" {
                type master;
                file "/etc/bind/db.255";
        };

    // formerly zones.rfc1918

        zone "10.in-addr.arpa"      { type master; file "/etc/bind/db.empty"; };
        zone "16.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "17.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "18.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "19.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "20.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "21.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "22.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "23.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "24.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "25.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "26.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "27.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "28.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "29.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "30.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "31.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };

};

// 2
view "internal_10_view" {
    
    allow-query-on { 192.168.10.1; };
    allow-query { internal_10_acl; };
    match-clients { internal_10_acl; };

    zone "somehost.tld" {
            type master;
            file "/etc/bind/db.somehost.tld_10";
    };

    zone "168.192.in-addr.arpa" {
            type master;
            notify no;
            file "/etc/bind/db.192.168.10";
    };

    // formerly named.conf.default-zones

        zone "." {
                type hint;
                file "/etc/bind/db.root";
        };

        zone "localhost" {
                type master;
                file "/etc/bind/db.local";
        };

        zone "127.in-addr.arpa" {
                type master;
                file "/etc/bind/db.127";
        };

        zone "0.in-addr.arpa" {
                type master;
                file "/etc/bind/db.0";
        };

        zone "255.in-addr.arpa" {
                type master;
                file "/etc/bind/db.255";
        };

    // formerly zones.rfc1918

        zone "10.in-addr.arpa"      { type master; file "/etc/bind/db.empty"; };
        zone "16.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "17.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "18.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "19.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "20.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "21.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "22.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "23.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "24.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "25.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "26.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "27.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "28.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "29.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "30.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "31.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };

};

// 3
view "internal_150_view" {

        allow-query-on { 192.168.150.1; };
        allow-query { internal_150_acl; };
    match-clients { internal_150_acl; };

    zone "somehost.tld" {
            type master;
            file "/etc/bind/db.somehost.tld_150";
    };

    zone "168.192.in-addr.arpa" {
            type master;
            notify no;
            file "/etc/bind/db.192.168.150";
    };

    // formerly named.conf.default-zones

        zone "." {
                type hint;
                file "/etc/bind/db.root";
        };

        zone "localhost" {
                type master;
                file "/etc/bind/db.local";
        };

        zone "127.in-addr.arpa" {
                type master;
                file "/etc/bind/db.127";
        };

        zone "0.in-addr.arpa" {
                type master;
                file "/etc/bind/db.0";
        };

        zone "255.in-addr.arpa" {
                type master;
                file "/etc/bind/db.255";
        };

    // formerly zones.rfc1918

        zone "10.in-addr.arpa"      { type master; file "/etc/bind/db.empty"; };
        zone "16.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "17.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "18.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "19.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "20.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "21.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "22.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "23.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "24.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "25.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "26.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "27.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "28.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "29.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "30.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "31.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };

};

// 4
view "vpn_view" {
    
    allow-query-on { 192.168.200.1; };
    allow-query { vpn_acl; };
    match-clients { vpn_acl; };
        
    zone "somehost.tld" {
        type master;
        file "/etc/bind/db.somehost.tld_vpn";
    };

    // formerly named.conf.default-zones

        zone "." {
                type hint;
                file "/etc/bind/db.root";
        };

        zone "localhost" {
                type master;
                file "/etc/bind/db.local";
        };

        zone "127.in-addr.arpa" {
                type master;
                file "/etc/bind/db.127";
        };

        zone "0.in-addr.arpa" {
                type master;
                file "/etc/bind/db.0";
        };

        zone "255.in-addr.arpa" {
                type master;
                file "/etc/bind/db.255";
        };

    // formerly zones.rfc1918

        zone "10.in-addr.arpa"      { type master; file "/etc/bind/db.empty"; };
        zone "16.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "17.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "18.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "19.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "20.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "21.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "22.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "23.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "24.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "25.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "26.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "27.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "28.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "29.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "30.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "32.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };

};

// 5
view "global_view" {
    
    allow-query-on { 1.2.3.4; };
//  match-clients { any; !localhost_acl; !internal_10_acl; !internal_150_acl; !vpn_acl; };
    recursion no;
        
    zone "somehost.tld" {

        type master;

        update-policy local;
        auto-dnssec maintain;

        file "/etc/bind/db.somehost.tld_global";

        key-directory "/etc/bind/keys";

    };

    zone "26/4.3.2.1.in-addr.arpa" IN {
        type master;
        file "/etc/bind/db.rev";
    };

    // formerly named.conf.default-zones

        zone "." {
                type hint;
                file "/etc/bind/db.root";
        };

        zone "localhost" {
                type master;
                file "/etc/bind/db.local";
        };

        zone "127.in-addr.arpa" {
                type master;
                file "/etc/bind/db.127";
        };

        zone "0.in-addr.arpa" {
                type master;
                file "/etc/bind/db.0";
        };

        zone "255.in-addr.arpa" {
                type master;
                file "/etc/bind/db.255";
        };

    // formerly zones.rfc1918

        zone "10.in-addr.arpa"      { type master; file "/etc/bind/db.empty"; };
        zone "16.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "17.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "18.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "19.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "20.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "21.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "22.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "23.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "24.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "25.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "26.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "27.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "28.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "29.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "30.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };
        zone "32.172.in-addr.arpa"  { type master; file "/etc/bind/db.empty"; };

};

ACLs:

acl localhost_acl {
        127.0.0.0/8;
};

acl internal_10_acl {
        192.168.10.0/24;
};

acl internal_150_acl {
        192.168.150.0/24;
};

acl vpn_acl {
        192.168.200.2;
        192.168.200.5;
};

So the update-policy local; is here, /var/run/named/session.key is successfully generated and user bind readable, but when I perform the add command via nsupdate -l (as root), I always get the update failed: REFUSED error (here with debug messages):

root@somehost:/etc/bind# nsupdate -l -v -D
setup_system()
Creating key...
namefromtext
keycreate
reset_system()
user_interaction()
> ttl 46000
do_next_command()
> zone somehost.tld.
do_next_command()
> update add whatever.somehost.tld. A 1.1.1.1
do_next_command()
evaluate_update()
update_addordelete()
> send
do_next_command()
start_update()
send_update()
Sending update to 127.0.0.1#53
show_message()
Outgoing update query:
;; ->>HEADER<<- opcode: UPDATE, status: NOERROR, id:  15363
;; flags:; ZONE: 1, PREREQ: 0, UPDATE: 1, ADDITIONAL: 1
;; ZONE SECTION:
;somehost.tld.                      IN      SOA

;; UPDATE SECTION:
whatever.somehost.tld.  46000   IN      A       1.1.1.1

;; TSIG PSEUDOSECTION:
local-ddns.             0       ANY     TSIG    hmac-sha256. 1446539060 300 32 r2lt18dGihGnJepoUjvIKx8l5BPMohNJvsLoO+WQiBE                                                                         = 15363 NOERROR 0

update_completed()
tsig verification successful
show_message()

Reply from update query:
;; ->>HEADER<<- opcode: UPDATE, status: REFUSED, id:  15363
;; flags: qr ra; ZONE: 1, PREREQ: 0, UPDATE: 0, ADDITIONAL: 1
;; ZONE SECTION:
;somehost.tld.                      IN      SOA

;; TSIG PSEUDOSECTION:
local-ddns.             0       ANY     TSIG    hmac-sha256. 1446539060 300 32 Cnh9Tgg5vhKngPRk2J8n0wiRzdBLlQrp0F0qmfUotN8                                                                         = 15363 NOERROR 0

done_update()
reset_system()
user_interaction()
> quit

It is some kind of permission issue? What's wrong?

Best Answer

Finally figured it out. Thanks to @Håkan Lindqvist for inspiration.

These solutions are probably Debian/Ubuntu-specific and weren't tested in other distros.

1. FIRST SOLUTION

(Using update-policy local;).

You may actually use update-policy local; directive in /etc/bind/named.conf.local in each zone declaration you want, which restricts update requests from the internet or LAN for better security. In this case the key is generated automatically and nsupdate will use it if run with -l option.

Instead of server X.X.X.X command one should use local X.X.X.X. It accepts even public IP as argument if it is local to the system!

Note: the key is not world-readable, so use sudo.

Example:

me@somehost:~$ sudo nsupdate -l
> local 1.2.3.4
> zone somehost.tld
> update add something.somehost.tld. 86400 A 1.1.1.1
> send
> quit

2. SECOND SOLUTION

(Using ddns-confgen).

I have plenty of views (localhost_view, global_view etc.), some of which have common zones (somehost.tld in my example). If I want to dynamically update them, I should use server X.X.X.X command when do nsupdate. Therefore nsupdate will send an update request to the appropriate interface and the appropriate view will handle it.

update-policy local; is not suitable in this configuration because it forbids use of the server command in nsupdate. So it is needed to generate a DDNS key and specify it in all of the zones declarations, which should be dynamically updated by nsupdate. In the Debian universe there is a ddns-confgen command which simplifies this task a lot:

me@somehost:~$ ddns-confgen
# To activate this key, place the following in named.conf, and
# in a separate keyfile on the system or systems from which nsupdate
# will be run:
key "ddns-key" {
        algorithm hmac-sha256;
        secret "pXohPnPR7dyri9ADfDLtSz+lHw/QliISyiEe0wg0a14=";
};

# Then, in the "zone" statement for each zone you wish to dynamically
# update, place an "update-policy" statement granting update permission
# to this key.  For example, the following statement grants this key
# permission to update any name within the zone:
update-policy {
        grant ddns-key zonesub ANY;
};

# After the keyfile has been placed, the following command will
# execute nsupdate using this key:
nsupdate -k <keyfile>

The output of this command is quite self-descriptive. It is needed to add key... snippet to the /etc/bind/named.conf and separate file with any name, and update-policy... snippet into each zone declaration, which will be managed by nsupdate.

To properly use nsupdate tool in multi-view BIND environment, it is needed to explicitly specify a server directive before executing any other command. So, for updating localhost_view's somehost.tld zone (considering key... snippet was saved to the /etc/bind/ddns-key.key) the commands are as follows (note the server 127.0.0.1):

me@somehost:~$ nsupdate -k /etc/bind/ddns-key.key
> server 127.0.0.1
> zone somehost.tld
> update add something.somehost.tld. 86400 A 1.1.1.1
> send
> quit

whereas to manipulate global_view's somehost.tld zone the commands are essentially the same, but with different server. In this case it is needed to use public IP (1.2.3.4 in my example):

me@somehost:~$ nsupdate -k /etc/bind/ddns-key.key
> server 1.2.3.4
> zone somehost.tld
> update add something.somehost.tld. 86400 A 1.1.1.1
> send
> quit

Therefore nsupdate sends a request to a proper interface (which may or may not be the local one) and a specific view works.

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