Improved determination of root domain for the Variomedia DNS API

[peterkelm]

Rewrite of _get_root() to address an issue with the handling of subdomains in the /domains call of the Variomedia DNS API. See #2564.

[Neilpang]

the value of "i" should be beginning from 1, not 2.

In dns alias mode, the fulldomain can be no _acme-challenge prefix

[morlac]

it's been tested:

• successfully with i=2
• unsuccessfully with i=1

[fraenki]

@peterkelm Using this patch, I can confirm that it fixes the creation of TXT records with acme.sh. However, in my case it failed to remove the TXT records afterwards. Some unusual cURL output is shown and then a failure is reported:

[Mon Feb 21 00:21:46 CET 2022] Here is the curl dump log:
[Mon Feb 21 00:21:46 CET 2022] == Info:   Trying 81.28.224.32:443...
== Info: Connected to api.variomedia.de (81.28.224.32) port 443 (#0)
== Info: ALPN, offering h2
== Info: ALPN, offering http/1.1
== Info:  CAfile: /usr/local/etc/ssl/cert.pem
== Info:  CApath: none
=> Send SSL data, 5 bytes (0x5)
...
[Mon Feb 21 00:21:46 CET 2022] ret='3'
[Mon Feb 21 00:21:46 CET 2022] Error dns-records?filter[domain]=example.com
[Mon Feb 21 00:21:46 CET 2022] Error
[Mon Feb 21 00:21:46 CET 2022] Error removing txt for domain:_acme-challenge.example.com

[TobiasGrave]

@peterkelm Using this patch, I can confirm that it fixes the creation of TXT records with acme.sh. However, in my case it failed to remove the TXT records afterwards. Some unusual cURL output is shown and then a failure is reported:

[Mon Feb 21 00:21:46 CET 2022] Here is the curl dump log:
[Mon Feb 21 00:21:46 CET 2022] == Info:   Trying 81.28.224.32:443...
== Info: Connected to api.variomedia.de (81.28.224.32) port 443 (#0)
== Info: ALPN, offering h2
== Info: ALPN, offering http/1.1
== Info:  CAfile: /usr/local/etc/ssl/cert.pem
== Info:  CApath: none
=> Send SSL data, 5 bytes (0x5)
...
[Mon Feb 21 00:21:46 CET 2022] ret='3'
[Mon Feb 21 00:21:46 CET 2022] Error dns-records?filter[domain]=example.com
[Mon Feb 21 00:21:46 CET 2022] Error
[Mon Feb 21 00:21:46 CET 2022] Error removing txt for domain:_acme-challenge.example.com

The removal of the the TXT record fails when its content starts with a -.

This problem is caused by grep "$txtvalue" in the following line:
record_id="$(echo "$response" | cut -d '[' -f2 | cut -d']' -f1 | sed 's/},[ \t]*{/\},§\{/g' | tr § '\n' | grep "$_sub_domain" | grep "$txtvalue" | sed 's/^{//;s/}[,]?$//' | tr , '\n' | tr -d '\"' | grep ^id | cut -d : -f2 | tr -d ' ')"

This is due to grep interpreting everything starting with a - as an option and not as a search term.
In order to fix this, the option -- has to be added before the search term (https://www.gnu.org/software/grep/manual/grep.html#index-_002d_002d):
_record_id="$(echo "$response" | cut -d '[' -f2 | cut -d']' -f1 | sed 's/},[ \t]*{/\},§\{/g' | tr § '\n' | grep "$_sub_domain" | grep -- "$txtvalue" | sed 's/^{//;s/}[,]?$//' | tr , '\n' | tr -d '\"' | grep ^id | cut -d : -f2 | tr -d ' ')"