acme dns_duckdb error extracting the domain

Hi,

Can't renew certificate through DNS API.

To reproduce:

# export DuckDNS_Token="184b69af-5862-410f-be2b-883f0743b8f9"
# /usr/lib/acme/client/acme.sh --test --renew --home /etc/acme --domain test.duckdns.org
[Mon Feb 10 19:03:02 +07 2025] Using ACME_DIRECTORY: https://acme-staging-v02.api.letsencrypt.org/directory
[Mon Feb 10 19:03:02 +07 2025] Renew: 'test.duckdns.org'
[Mon Feb 10 19:03:02 +07 2025] Renew to Le_API=https://acme-v02.api.letsencrypt.org/directory
[Mon Feb 10 19:03:03 +07 2025] Using CA: https://acme-v02.api.letsencrypt.org/directory
[Mon Feb 10 19:03:04 +07 2025] Single domain='test.duckdns.org'
[Mon Feb 10 19:03:04 +07 2025] Getting domain auth token for each domain
[Mon Feb 10 19:03:07 +07 2025] Getting webroot for domain='test.duckdns.org'
[Mon Feb 10 19:03:07 +07 2025] Adding txt value: EQbV2_zKJf9C0oiqnUcdSqUOLLhjjoRRzs0ygLaVPFQ for domain:  _acme-challenge.test.duckdns.org
[Mon Feb 10 19:03:07 +07 2025] Error extracting the domain.
[Mon Feb 10 19:03:07 +07 2025] Error add txt for domain:_acme-challenge.test.duckdns.org
[Mon Feb 10 19:03:07 +07 2025] Please check log file for more details: /tmp/acme.log

Error raised from this: /usr/lib/acme/client/dnsapi/dns_duckdns.sh
dns_duckdns_add => _duckdns_get_domain => _egrep_o

_egrep_o seems uses sed which works incorrect with this regular expression. As result _duckdns_domain is always empty.

Source code links:

• https://github.com/acmesh-official/acme.sh/blob/3.0.7/dnsapi/dns_duckdns.sh#L102
• https://github.com/acmesh-official/acme.sh/blob/3.0.7/acme.sh#L929
• https://github.com/acmesh-official/acme.sh/blob/3.0.7/acme.sh#L936

OS info:

# cat /etc/os-release 
NAME="OpenWrt"
VERSION="24.10.0"
ID="openwrt"
ID_LIKE="lede openwrt"
PRETTY_NAME="OpenWrt 24.10.0"
VERSION_ID="24.10.0"
HOME_URL="https://openwrt.org/"
BUG_URL="https://bugs.openwrt.org/"
SUPPORT_URL="https://forum.openwrt.org/"
BUILD_ID="r28427-6df0e3d02a"
OPENWRT_BOARD="mediatek/filogic"
OPENWRT_ARCH="aarch64_cortex-a53"
OPENWRT_TAINTS=""
OPENWRT_DEVICE_MANUFACTURER="OpenWrt"
OPENWRT_DEVICE_MANUFACTURER_URL="https://openwrt.org/"
OPENWRT_DEVICE_PRODUCT="Generic"
OPENWRT_DEVICE_REVISION="v0"
OPENWRT_RELEASE="OpenWrt 24.10.0 r28427-6df0e3d02a"
OPENWRT_BUILD_DATE="1738624177"

# opkg list-installed | grep acme
acme - 4.0.0
acme-acmesh - 3.0.7-r2
acme-acmesh-dnsapi - 3.0.7-r2
acme-common - 1.4.0
luci-app-acme - 25.037.68331~42f464c

Also tried with this code:

if [ "$(echo abc | egrep -o b 2>/dev/null)" = "b" ]; then
  __USE_EGREP=1
else
  __USE_EGREP=""
fi

_egrep_o() {
  if [ "$__USE_EGREP" ]; then
    egrep -o -- "$1" 2>/dev/null
  else
    sed -n 's/.*\('"$1"'\).*/\1/p'
  fi
}

_lower_case() {
  # shellcheck disable=SC2018,SC2019
  tr '[A-Z]' '[a-z]'
}

fulldomain="_acme-challenge.test.duckdns.org"

_duckdns_domain="$(printf "%s" "$fulldomain" | _lower_case | _egrep_o '^(_acme-challenge\.)?([a-z0-9-]+\.)+duckdns\.org' | sed -n 's/^\([^.]\{1,\}\.\)*\([a-z0-9-]\{1,\}\)\.duckdns\.org$/\2/p;')"

echo "$__USE_EGREP"
echo "$fulldomain"
echo "$_duckdns_domain"

__USE_EGREP and _duckdns_domain is empty

Start with dnsapi/dns_duckdns.sh and the _egrep_o implementation around acme.sh lines 929 and 936. Reproduce the OpenWrt command and the standalone _duckdns_domain example, then verify that domain extraction succeeds and the renewal can add the TXT record for _acme-challenge.test.duckdns.org.