• Ralph Seichter via dovecot schrieb am 06.09.23 um 22:43 Uhr:

Hello,

I cannot seem to send STARTTLS protected mail to talvi.dovecot.org, and I was wondering if anybody else sees similar problems:

Sep 6 22:29:10 ra postfix/smtp[15748]: SSL_connect error to talvi.dovecot.org[94.237.105.223]:25: -1 Sep 6 22:29:10 ra postfix/smtp[15748]: warning: TLS library problem: error:0A000417:SSL routines::sslv3 alert illegal parameter:../openssl-3.0.9/ssl/record/rec_layer_s3.c:1586:SSL alert number 47: Sep 6 22:29:10 ra postfix/smtp[15748]: 1AAE4BE0031: Cannot start TLS: handshake failure Sep 6 22:29:10 ra postfix/smtp[15748]: SSL_connect error to talvi.dovecot.org[2a04:3545:1000:720:acc1:5bff:fe5e:459]:25: -1 Sep 6 22:29:10 ra postfix/smtp[15748]: warning: TLS library problem: error:0A000417:SSL routines::sslv3 alert illegal parameter:../openssl-3.0.9/ssl/record/rec_layer_s3.c:1586:SSL alert number 47: Sep 6 22:29:10 ra postfix/smtp[15748]: 1AAE4BE0031: to=<dovecot@dovecot.org>, relay=talvi.dovecot.org[2a04:3545:1000:720:acc1:5bff:fe5e:459]:25, delay=1.6, delays=0.02/0.01/1.6/0, dsn=4.7.5, status=deferred (Cannot start TLS: handshake failure) Sep 6 22:30:05 ra postfix/smtpd[15616]: timeout after END-OF-MESSAGE from localhost[127.0.0.1] Sep 6 22:30:05 ra postfix/smtpd[15616]: disconnect from localhost[127.0.0.1] ehlo=1 xforward=1 mail=1 rcpt=1 data=1 commands=5

The originating server uses Postfix 3.8.2 and OpenSSL library 3.0.9. To be able to send messages to dovecot.org at all, I had to use Postfix's "smtp_tls_policy_maps" setting to explicitly disable TLS for this destination domain.

Your openssl-3.0.9 (I suppose gentoo stable?) will not allow TLSv1 or sslv3 connections bei default anymore.

Wild guess: you need to explicitely allow for example DEFAULT@SECLEVEL=0 ciphersuite in postfix to make *your* openssl accept this remote sslv3 connection

Cheers -Marc

-- [*] sys4 AG

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On 07/09/2023 03:49 EEST Ralph Seichter via dovecot <dovecot@dovecot.org> wrote:

• Marc Schiffbauer via dovecot:

...

Wild guess: you need to explicitely allow for example DEFAULT@SECLEVEL=0 ciphersuite in postfix to make *your* openssl accept this remote sslv3 connection

Thanks, Marc. I had thought about this, and have tried various Postfix parameters related to TLS ciphers and protocols. So far, no dice. In the meantime, I also ran tests using Swaks, and this resulted in a possible different route of investigation: Postfix uses a certificate issued by Let's Encrypt (secp384r1) for both in- and outbound connections with STARTTLS. If I use the same certificate with Swaks, I see the same error as I do with Postfix. If I use Swaks *without* specifying a local TLS certificate, the STARTTLS handshake works:

=== Trying talvi.dovecot.org:25... === Connected to talvi.dovecot.org. <- 220 talvi.dovecot.org ESMTP Postfix (Debian/GNU) -> EHLO ra.horus-it.com <- 250-talvi.dovecot.org <- 250-PIPELINING <- 250-SIZE 104857600 <- 250-ETRN <- 250-STARTTLS <- 250-ENHANCEDSTATUSCODES <- 250-8BITMIME <- 250-DSN <- 250 CHUNKING -> STARTTLS <- 220 2.0.0 Ready to start TLS === TLS started with cipher TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256 === TLS no local certificate set === TLS peer DN="/CN=talvi.dovecot.org"

Looks the combination of certificate ciphers and OpenSSL library versions on my end and on the talvi.dovecot.org end is causing some bother. The original error message points to a protocol issue, not a cipher problem, and how SSLv3 gets into the mix is anybody's guess. Perhaps I'll see clearer after some much needed sleep.

-Ralph

I updated the settings a bit on the server as well. Maybe it works better now?

Aki

On 07/09/2023 20:46 EEST Ralph Seichter via dovecot <dovecot@dovecot.org> wrote:

• Aki Tuomi via dovecot:

...

I updated the settings a bit on the server as well. Maybe it works better now?

Yes, it does indeed:

Sep 7 19:33:23 ra postfix/smtp[14429]: Trusted TLS connection established to talvi.dovecot.org[2a04:3545:1000:720:acc1:5bff:fe5e:459]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature ECDSA (secp384r1) client-digest SHA384 Sep 7 19:33:24 ra postfix/smtp[14429]: 1989FBE002A: to=<dovecot-request@dovecot.org>, relay=talvi.dovecot.org[2a04:3545:1000:720:acc1:5bff:fe5e:459]:25, delay=4.3, delays=0.01/0.01/3.6/0.73, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as D22D55DEF4)

Thank you, Aki. Would you be willing to share what was changed in your server's settings and/or certificates? I am still wondering what exactly caused the issue. By the way, I have reverted all TLS-related changes previously used for testing on my end, returning to Postfix's defaults.

-Ralph

Mostly just disabled older TLS stuff and in particular enabled TLSv1.3.

Aki