Re: [exim] TLS "certificate expired" warnings on inbound con…

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Autor: Tim Jackson
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A: exim-users
Assumpte: Re: [exim] TLS "certificate expired" warnings on inbound connections
On 31/05/2022 21:14, Viktor Dukhovni via Exim-users wrote:

> TLS alerts report error conditions from the remote peer. If your server
> logs a TLS alert, that alert was generated on the remote end. So if
> this is a connection from a client to your server, then the "certificate
> expired" condition is something that the client believes to be the case.


Thanks for the clarification. So the issue is the client verification of the
server cert, not a client cert.

>> Certificate chain
>>    0 s:CN = mx1.firecluster.net
>>      i:C = US, O = Let's Encrypt, CN = R3
>>    1 s:C = US, O = Let's Encrypt, CN = R3
>>      i:C = US, O = Internet Security Research Group, CN = ISRG Root X1
>>    2 s:C = US, O = Internet Security Research Group, CN = ISRG Root X1
>>      i:O = Digital Signature Trust Co., CN = DST Root CA X3

>
> The DST Root CA is expired. You can configure LE to build a
> "fullchain.pem" using the ISRG root instead. The only downside is that
> old Android systems may no longer be able to verify your chain.


OK, so my original theory was right (and, if I understand rightly, this is an
outdated client implementation). Is the solution 'certbot --preferred-chain
"ISRG Root X1"' then? (As I mentioned, I currently use acme-tiny rather than
certbot, which unfortunately doesn't seem to support choosing the chain [1],
so I guess I have to switch)

> You can use a different cert chain for submission than for port 25
> (where you're unlikely to need Android support).


Indeed.


Thank you very much for the advice!


Tim

[1] https://github.com/diafygi/acme-tiny/issues/255