acme-dns: continue the process when the CNAME is handled by the storage

[ldez]

#2437 (comment)

[ldez]

My implementation is wrong, I will fix that

[dmke]

This makes sense 👍

[skippyprime]

Well, I found one more issue (and I think this is the last) in the flow.

Since the call to Fetch() will return an error for a new challenge, account will be nil. The register function will create the new account and must return that to the caller so it can be used in the UpdateTXTRecord call. It is currently always nil for new challenges.

The Present function should probably look like this:

func (d *DNSProvider) Present(domain, _, keyAuth string) error {
	ctx := context.Background()

	// Compute the challenge response FQDN and TXT value for the domain based on the keyAuth.
	info := dns01.GetChallengeInfo(domain, keyAuth)

	// Check if credentials were previously saved for this domain.
	account, err := d.storage.Fetch(ctx, domain)
	if err != nil {
		if !errors.Is(err, storage.ErrDomainNotFound) {
			return err
		}

		// The account did not exist.
		// Create a new one and return an error indicating the required one-time manual CNAME setup.
		account, err = d.register(ctx, domain, info.FQDN)
		if err != nil {
			return err
		}
	}

	// Update the acme-dns TXT record.
	return d.client.UpdateTXTRecord(ctx, account, info.Value)
}

And register function needs to return the new account:

func (d *DNSProvider) register(ctx context.Context, domain, fqdn string) (goacmedns.Account, error) {
	newAcct, err := d.client.RegisterAccount(ctx, d.config.AllowList)
	if err != nil {
		return newAcct, err
	}

	var cnameCreated bool

	// Store the new account in the storage and call save to persist the data.
	err = d.storage.Put(ctx, domain, newAcct)
	if err != nil {
		cnameCreated = errors.Is(err, internal.ErrCNAMEAlreadyCreated)
		if !cnameCreated {
			return newAcct, err
		}
	}

	err = d.storage.Save(ctx)
	if err != nil {
		return newAcct, err
	}

	if cnameCreated {
		return newAcct, nil
	}

	// Stop issuance by returning an error.
	// The user needs to perform a manual one-time CNAME setup in their DNS zone
	// to complete the setup of the new account we created.
	return newAcct, ErrCNAMERequired{
		Domain: domain,
		FQDN:   fqdn,
		Target: newAcct.FullDomain,
	}
}

[ldez]

#2445