Re: openssl3+postfix issue (ca md too weak)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Mon, Nov 13, 2023 at 10:58:38PM +0100, Steffen Nurpmeso wrote:
> Manuel Bouyer wrote in
>  <ZVKXHU06IovpfKIt%antioche.eu.org@localhost>:
>  |On Mon, Nov 13, 2023 at 10:24:56PM +0100, Steffen Nurpmeso wrote:
>  |> Manuel Bouyer wrote in
>  |>  <ZVJ6LIrEPxlCEbNB%antioche.eu.org@localhost>:
>  |>|Hello
>  |>|I'm facing an issue with postfix+openssl3 which may be critical (dependi\
>  |>|ng
>  |>|on how it can be fixed).
>  |>|
>  |>|Now my postfix setup fails to send mails with
>  ...
>  |>|>From what I understood, this is the remote certificate which is not \
>  |>|>accepted:
>  |>|openssl 3 deprecated some signature algorithm, which are no longer \
>  |>|accepted
>  ...
>  |> Isn't that just postfix config.
>  |
>  |It's possible; but I didn't find anything relevant in the postfix docs
>  |
>  |> Btw *i* have no problem with
>  |> 
>  |>   smtpd_tls_ask_ccert = no
>  |>   smtpd_tls_auth_only = yes
>  |>   smtpd_tls_loglevel = 1
>  |>   #SMART The next is usually nice but when using client certificates
>  |>   smtpd_tls_received_header = no
>  |>   smtpd_tls_fingerprint_digest = sha256
>  |>   smtpd_tls_mandatory_protocols = >=TLSv1.2
>  |>   smtpd_tls_protocols = $smtpd_tls_mandatory_protocols
>  |>   # super modern, forward secrecy TLSv1.2 / TLSv1.3 selection..
>  |>   tls_high_cipherlist = EECDH+AESGCM:EECDH+AES256:EDH+AESGCM:CHACHA20
>  |>   smtpd_tls_mandatory_ciphers = high
>  |>   smtpd_tls_mandatory_exclude_ciphers = TLSv1
>  |> 
>  |> ^ This works in practice without any noticeable trouble.
>  |> (But then i again i do not have to make money from that or my
>  |> customers who must talk to ten year old refrigerators.)
>  |
>  |this is only server-side configuration; my problem is with client-side
>  |rejecting the server's certificate
> 
> Well i have
> 
>   #SMART comment out next
>   smtp_tls_security_level = may

I have
smtp_tls_security_level = verify

and this is what I need because a username/passwd is sent as part of
the smtp transaction

>   # To always go directly SMTPS/SUBMISSIONS
>   #smtp_tls_wrappermode = yes
>   smtp_tls_fingerprint_digest = $smtpd_tls_fingerprint_digest
>   smtp_tls_mandatory_protocols = $smtpd_tls_mandatory_protocols
>   smtp_tls_protocols = $smtpd_tls_protocols
>   #SMART When only relaying to smarthost, the next should be =high _or_better_!
>   smtp_tls_mandatory_ciphers = $smtpd_tls_mandatory_ciphers
>   smtp_tls_mandatory_exclude_ciphers = $smtpd_tls_mandatory_exclude_ciphers
>   smtp_tls_ciphers = $smtpd_tls_ciphers
>   smtp_tls_exclude_ciphers = $smtpd_tls_exclude_ciphers
>   smtp_tls_connection_reuse = yes
> 
> But if you have a problem with only one permanent remote partner

In my config I have 2 possible relays (depending on the from of the email)
and both shows the same problem (yet with different certificates signed by
different CAs).

> you surely want a dedicated map for that one.

No, I need a strong encrypted connection

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--