[exim] Tainted filenames?

I'm 'de-tainting' my old exim config file, but i've found a trouble.

I've a transport that have:

    dkim_private_key = ${if exists{/etc/exim4/dkim/DKIM_DOMAIN-DKIM_SELECTOR-private.pem}{/etc/exim4/dkim/DKIM_DOMAIN-DKIM_SELECTOR-private.pem}{0}}

that lead to:

    2024-08-22 12:19:34 1sh4uf-000Dka-JC Warning: Tainted filename '/etc/exim4/dkim/lists.pnlug.it-XXXX-private.pem'

clearly 'DKIM_DOMAIN' and 'DKIM_SELECTOR' are macros.


How can i detaint it? Thanks.

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