temptxt

Name

temptxt - serves TXT records for validation purposes (eg. ACME DNS-01 challenge) updated through a HTTP api.

Description

The temptxt plugin is useful for delegating the configuration of TXT records for purposes such as certificate validation (eg. ACME DNS-01).

Users can update the content of the TXT records through a HTTP API. Authentication to the API is handled by a HTTP header passed from the upstream reverse proxy.

Syntax

temptxt [PREFIX] [SUFFIX] {
    [txt FQDN REGEXP1 REGEXP2 ...]
    [txt_alias ACTUAL_FQDN UPDATE_FQDN REGEXP1 REGEXP2 ...]

    [auth_header X-Forwarded-User]
    [clean_interval DURATION]
    [max_age DURATION]
    [listen ADDRESS]
}

• PREFIX - Prefix to add to FQDNs. This only affects DNS queries. Updates through the API need to use the FQDN without the prefix (txt_alias doesn't used prefix).
• SUFFIX - Suffix to add to FQDNs. This only affects DNS queries. Updates through the API need to use the FQDN without the suffix (txt_alias doesn't used suffix).
• txt - FQDN to serve txt records for. If one of the regexps matches the username, the API request will be allowed. Regexps are automatically anchored with ^ and $.
• txt_alias - Useful in use cases like example 2. UPDATE_FQDN is the FQDN that is used when calling the API, but the TXT record for ACTUAL_FQDN will be the one that is actually updated.
• auth_header - The header that contains the username for API authentication. Make sure that this a user cannot set the contents of the header. Default: X-Forwarded-User
• clean_interval - The interval that records will be periodically cleared. Set to 0 to disable cleaning. Default: 0.
• max_age - If the time since the record has last been updated is greater than the given duration, the contents will be cleared. Default: 15m0s
• listen - The address to listen on. Default: :8080

Example 1 - ACME DNS-01

Use temptxt for acme DNS-01 validation for test1.example.com and test2.example.com. CoreDNS is authoritative for example.com.

Configuration

1. CoreDNS configuration

   temptxt _acme-challenge. {
       txt test1.example.com user1
       txt test2.example.com user[0-2] user4
   }
   

   Also equivalent:

   temptxt {
       txt _acme-challenge.test1.example.com user1
       txt _acme-challenge.test2.example.com user[0-2] user4
   }
   

2. Configure the ACME client to call the temptxt API.

Outcome

• The content of _acme-challenge.test1.example.com can be updated by user1.

• The content of _acme-challenge.test2.example.com can be updated by user1, user2, and user4.

• Queries for other _acme-challenge.*.example.com records will fallthrough.

• If the content of the txt record is "", NXDOMAIN will be returned.

Example 2 - ACME DNS Alias

• The is similar to acme-dns. It allows temptxt to be used for validation when CoreDNS is not the authoritative server for a given zone using CNAMEs.

Configuration

1. Create NS records for acme-dns.example.com pointing to this server.

2. Create a CNAME from _acme-challenge.www.example.com to www.acme-dns.example.com on the DNS server for example.com

3. Configure CoreDNS

   temptxt {
       txt_alias www.acme-dns.example.com www.example.com user1
   }
   

4. Configure the ACME client to call the temptxt API.

Results

1. The ACME client will update the TXT record for www.acme-dns.example.com using the API.

2. Since there is a CNAME from _acme-challenge.www.example.com the ACME server will query temptxt for the validation string.

Example certbot hooks

Update using basic auth

curl -X POST \
    -d "fqdn=www.example.com&content=$CERTBOT_TOKEN" \
    -u username:password \
    https://acme-dns.example.com/update

Clear record using certificate auth

curl -X POST \
    -d "fqdn=www.example.com&content=test" \
    --cert ./cert.crt \
    --key ./cert.key \
    https://acme-dns.example.com/update