planet grml

I’m one of the few folks left who run and maintain mail servers. Recently I had major troubles receiving mails from the mail servers used by a bank, and when asking my favourite search engine, I’m clearly not the only one who ran into such an issue. Actually, I should have checked off the issue and not become a customer at that bank, but the tech nerd in me couldn’t resist getting to the bottom of the problem. Since I got it working and this might be useful for others, here we are. :)

I was trying to get an online banking account set up, but the corresponding account creation mail didn’t arrive me, at all. Looking at my mail server logs, my postfix mail server didn’t accept the mail due to:

postfix/smtpd[3319640]: warning: TLS library problem: error:1417A0C1:SSL routines:tls_post_process_client_hello:no shared cipher:../ssl/statem/statem_srvr.c:2283:
postfix/smtpd[3319640]: lost connection after STARTTLS from mx01.arz.at[193.110.182.61]

Huh, what’s going on here?! Let’s increase the TLS loglevel (setting smtpd_tls_loglevel = 2) and retry. But how can I retry receiving yet another mail? Luckily, on the registration website of the bank there was a URL available, that let me request a one-time password. This triggered another mail, so I did that and managed to grab this in the logs:

postfix/smtpd[3320018]: initializing the server-side TLS engine
postfix/tlsmgr[3320020]: open smtpd TLS cache btree:/var/lib/postfix/smtpd_scache
postfix/tlsmgr[3320020]: tlsmgr_cache_run_event: start TLS smtpd session cache cleanup
postfix/smtpd[3320018]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: setting up TLS connection from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: mx01.arz.at[193.110.182.61]: TLS cipher list "aNULL:-aNULL:HIGH:MEDIUM:+RC4:@STRENGTH"
postfix/smtpd[3320018]: SSL_accept:before SSL initialization
postfix/smtpd[3320018]: SSL_accept:before SSL initialization
postfix/smtpd[3320018]: SSL3 alert write:fatal:handshake failure
postfix/smtpd[3320018]: SSL_accept:error in error
postfix/smtpd[3320018]: SSL_accept error from mx01.arz.at[193.110.182.61]: -1
postfix/smtpd[3320018]: warning: TLS library problem: error:1417A0C1:SSL routines:tls_post_process_client_hello:no shared cipher:../ssl/statem/statem_srvr.c:2283:
postfix/smtpd[3320018]: lost connection after STARTTLS from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 starttls=0/1 commands=1/2
postfix/smtpd[3320018]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[3320018]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2

Ok, so this TLS cipher list “aNULL:-aNULL:HIGH:MEDIUM:+RC4:@STRENGTH” looked like the tls_medium_cipherlist setting in postfix, but which ciphers might we expect? Let’s see what their SMTP server would speak to us:

% testssl --cipher-per-proto -t=smtp mx01.arz.at:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
TLS 1.1
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 256   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 256   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 256   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 256   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 256   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 256   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
TLS 1.3

Looks like a very small subset of ciphers, and they don’t seem to be talking TLS v1.3 at all? Not great. :(

A nice web service to verify the situation from another point of view is checktls, which also confirmed this:

[000.705] 	<-- 	220 2.0.0 Ready to start TLS
[000.705] 		STARTTLS command works on this server
[001.260] 		Connection converted to SSL
		SSLVersion in use: TLSv1_2
		Cipher in use: ECDHE-RSA-AES256-GCM-SHA384
		Perfect Forward Secrecy: yes
		Session Algorithm in use: Curve P-256 DHE(256 bits)
		Certificate #1 of 3 (sent by MX):
		Cert VALIDATED: ok
		Cert Hostname VERIFIED (mx01.arz.at = *.arz.at | DNS:*.arz.at | DNS:arz.at)
[...]
[001.517] 		TLS successfully started on this server

I got distracted by some other work, and when coming back to this problem, the one-time password procedure no longer worked, as the password reset URL was no longer valid. :( I managed to find the underlying URL, and with some web developer tools tinkering I could still use the website to let me trigger sending further one-time password mails, phew.

Let’s continue, so my mail server was running Debian/bullseye with postfix v3.5.18-0+deb11u1 and openssl v1.1.1n-0+deb11u5, let’s see what it offers:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
TLS 1.1
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
TLS 1.2
 xc02c   ECDHE-ECDSA-AES256-GCM-SHA384     ECDH 253   AESGCM      256      TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
 xc024   ECDHE-ECDSA-AES256-SHA384         ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
 xc00a   ECDHE-ECDSA-AES256-SHA            ECDH 253   AES         256      TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
 xcca9   ECDHE-ECDSA-CHACHA20-POLY1305     ECDH 253   ChaCha20    256      TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
 xc0af   ECDHE-ECDSA-AES256-CCM8           ECDH 253   AESCCM8     256      TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8
 xc0ad   ECDHE-ECDSA-AES256-CCM            ECDH 253   AESCCM      256      TLS_ECDHE_ECDSA_WITH_AES_256_CCM
 xc073   ECDHE-ECDSA-CAMELLIA256-SHA384    ECDH 253   Camellia    256      TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_CBC_SHA384
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 xa7     ADH-AES256-GCM-SHA384             DH 2048    AESGCM      256      TLS_DH_anon_WITH_AES_256_GCM_SHA384
 x6d     ADH-AES256-SHA256                 DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA256
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 xc5     ADH-CAMELLIA256-SHA256            DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA256
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 xc05d   ECDHE-ECDSA-ARIA256-GCM-SHA384    ECDH 253   ARIAGCM     256      TLS_ECDHE_ECDSA_WITH_ARIA_256_GCM_SHA384
 xc02b   ECDHE-ECDSA-AES128-GCM-SHA256     ECDH 253   AESGCM      128      TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
 xc023   ECDHE-ECDSA-AES128-SHA256         ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
 xc009   ECDHE-ECDSA-AES128-SHA            ECDH 253   AES         128      TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
 xc0ae   ECDHE-ECDSA-AES128-CCM8           ECDH 253   AESCCM8     128      TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
 xc0ac   ECDHE-ECDSA-AES128-CCM            ECDH 253   AESCCM      128      TLS_ECDHE_ECDSA_WITH_AES_128_CCM
 xc072   ECDHE-ECDSA-CAMELLIA128-SHA256    ECDH 253   Camellia    128      TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_CBC_SHA256
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 xa6     ADH-AES128-GCM-SHA256             DH 2048    AESGCM      128      TLS_DH_anon_WITH_AES_128_GCM_SHA256
 x6c     ADH-AES128-SHA256                 DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA256
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 xbf     ADH-CAMELLIA128-SHA256            DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA256
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 xc05c   ECDHE-ECDSA-ARIA128-GCM-SHA256    ECDH 253   ARIAGCM     128      TLS_ECDHE_ECDSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

Not so bad, but sadly no overlap with any of the ciphers that mx01.arz.at offers.

What about disabling STARTTLS for the mx01.arz.at (+ mx02.arz.at being another one used by the relevant domain) mail servers when talking to mine? Let’s try that:

% sudo postconf -nf smtpd_discard_ehlo_keyword_address_maps
smtpd_discard_ehlo_keyword_address_maps =
    hash:/etc/postfix/smtpd_discard_ehlo_keywords

% cat /etc/postfix/smtpd_discard_ehlo_keywords
# *disable* starttls for mx01.arz.at / mx02.arz.at:
193.110.182.61 starttls
193.110.182.62 starttls

But the remote mail server doesn’t seem to send mails without TLS:

postfix/smtpd[4151799]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[4151799]: discarding EHLO keywords: STARTTLS
postfix/smtpd[4151799]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2

Let’s verify this further, but without fiddling with the main mail server too much. We can add a dedicated service to postfix (see serverfault), and run it in verbose mode, to get more detailled logging:

% sudo postconf -Mf
[...]
10025      inet  n       -       -       -       -       smtpd
    -o syslog_name=postfix/smtpd/badstarttls
    -o smtpd_tls_security_level=none
    -o smtpd_helo_required=yes
    -o smtpd_helo_restrictions=pcre:/etc/postfix/helo_badstarttls_allow,reject
    -v

[...]

% cat /etc/postfix/helo_badstarttls_allow
/mx01.arz.at/ OK
/mx02.arz.at/ OK
/193.110.182.61/ OK
/193.110.182.62/ OK

We redirect the traffic from mx01.arz.at + mx02.arz.at towards our new postfix service, listening on port 10025:

% sudo iptables -t nat -A PREROUTING -p tcp -s 193.110.182.61 --dport 25 -j REDIRECT --to-port 10025
% sudo iptables -t nat -A PREROUTING -p tcp -s 193.110.182.62 --dport 25 -j REDIRECT --to-port 10025

With this setup we get very detailed logging, and it seems to confirm our suspicion that the mail server doesn’t want to talk unencrypted with us:

[...]
postfix/smtpd/badstarttls/smtpd[3491900]: connect from mx01.arz.at[193.110.182.61]
[...]
postfix/smtpd/badstarttls/smtpd[3491901]: disconnect from mx01.arz.at[193.110.182.61] ehlo=1 quit=1 commands=2
postfix/smtpd/badstarttls/smtpd[3491901]: master_notify: status 1
postfix/smtpd/badstarttls/smtpd[3491901]: connection closed
[...]

Let’s step back and revert those changes, back to our original postfix setup. Might the problem be related to our Let’s Encrypt certificate? Let’s see what we have:

% echo QUIT | openssl s_client -connect mail.example.com:25 -starttls
[...]
issuer=C = US, O = Let's Encrypt, CN = R3

---
No client certificate CA names sent
Peer signing digest: SHA384
Peer signature type: ECDSA
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 4455 bytes and written 427 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 384 bit
[...]

We have an ECDSA based certificate, what about switching to RSA instead? Thanks to the wonderful dehydrated, this is as easy as:

% echo KEY_ALGO=rsa > certs/mail.example.com/config
% ./dehydrated -c --domain mail.example.com --force
% sudo systemctl reload postfix

With switching to RSA type key we get:

% echo QUIT | openssl s_client -connect mail.example.com:25 -starttls smtp
CONNECTED(00000003)
[...]
issuer=C = US, O = Let's Encrypt, CN = R3

---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: RSA-PSS
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 5295 bytes and written 427 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 4096 bit

Which ciphers do we offer now? Let’s check:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]
Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
TLS 1.1
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 253   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9f     DHE-RSA-AES256-GCM-SHA384         DH 2048    AESGCM      256      TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
 xcca8   ECDHE-RSA-CHACHA20-POLY1305       ECDH 253   ChaCha20    256      TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xccaa   DHE-RSA-CHACHA20-POLY1305         DH 2048    ChaCha20    256      TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xc0a3   DHE-RSA-AES256-CCM8               DH 2048    AESCCM8     256      TLS_DHE_RSA_WITH_AES_256_CCM_8
 xc09f   DHE-RSA-AES256-CCM                DH 2048    AESCCM      256      TLS_DHE_RSA_WITH_AES_256_CCM
 x6b     DHE-RSA-AES256-SHA256             DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 xc077   ECDHE-RSA-CAMELLIA256-SHA384      ECDH 253   Camellia    256      TLS_ECDHE_RSA_WITH_CAMELLIA_256_CBC_SHA384
 xc4     DHE-RSA-CAMELLIA256-SHA256        DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA256
 x88     DHE-RSA-CAMELLIA256-SHA           DH 2048    Camellia    256      TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc019   AECDH-AES256-SHA                  ECDH 253   AES         256      TLS_ECDH_anon_WITH_AES_256_CBC_SHA
 xa7     ADH-AES256-GCM-SHA384             DH 2048    AESGCM      256      TLS_DH_anon_WITH_AES_256_GCM_SHA384
 x6d     ADH-AES256-SHA256                 DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA256
 x3a     ADH-AES256-SHA                    DH 2048    AES         256      TLS_DH_anon_WITH_AES_256_CBC_SHA
 xc5     ADH-CAMELLIA256-SHA256            DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA256
 x89     ADH-CAMELLIA256-SHA               DH 2048    Camellia    256      TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 xc0a1   AES256-CCM8                       RSA        AESCCM8     256      TLS_RSA_WITH_AES_256_CCM_8
 xc09d   AES256-CCM                        RSA        AESCCM      256      TLS_RSA_WITH_AES_256_CCM
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc0     CAMELLIA256-SHA256                RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA256
 x84     CAMELLIA256-SHA                   RSA        Camellia    256      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
 xc051   ARIA256-GCM-SHA384                RSA        ARIAGCM     256      TLS_RSA_WITH_ARIA_256_GCM_SHA384
 xc053   DHE-RSA-ARIA256-GCM-SHA384        DH 2048    ARIAGCM     256      TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc061   ECDHE-ARIA256-GCM-SHA384          ECDH 253   ARIAGCM     256      TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 253   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9e     DHE-RSA-AES128-GCM-SHA256         DH 2048    AESGCM      128      TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
 xc0a2   DHE-RSA-AES128-CCM8               DH 2048    AESCCM8     128      TLS_DHE_RSA_WITH_AES_128_CCM_8
 xc09e   DHE-RSA-AES128-CCM                DH 2048    AESCCM      128      TLS_DHE_RSA_WITH_AES_128_CCM
 xc0a0   AES128-CCM8                       RSA        AESCCM8     128      TLS_RSA_WITH_AES_128_CCM_8
 xc09c   AES128-CCM                        RSA        AESCCM      128      TLS_RSA_WITH_AES_128_CCM
 x67     DHE-RSA-AES128-SHA256             DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 xc076   ECDHE-RSA-CAMELLIA128-SHA256      ECDH 253   Camellia    128      TLS_ECDHE_RSA_WITH_CAMELLIA_128_CBC_SHA256
 xbe     DHE-RSA-CAMELLIA128-SHA256        DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA256
 x9a     DHE-RSA-SEED-SHA                  DH 2048    SEED        128      TLS_DHE_RSA_WITH_SEED_CBC_SHA
 x45     DHE-RSA-CAMELLIA128-SHA           DH 2048    Camellia    128      TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc018   AECDH-AES128-SHA                  ECDH 253   AES         128      TLS_ECDH_anon_WITH_AES_128_CBC_SHA
 xa6     ADH-AES128-GCM-SHA256             DH 2048    AESGCM      128      TLS_DH_anon_WITH_AES_128_GCM_SHA256
 x6c     ADH-AES128-SHA256                 DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA256
 x34     ADH-AES128-SHA                    DH 2048    AES         128      TLS_DH_anon_WITH_AES_128_CBC_SHA
 xbf     ADH-CAMELLIA128-SHA256            DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA256
 x9b     ADH-SEED-SHA                      DH 2048    SEED        128      TLS_DH_anon_WITH_SEED_CBC_SHA
 x46     ADH-CAMELLIA128-SHA               DH 2048    Camellia    128      TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 xba     CAMELLIA128-SHA256                RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA256
 x96     SEED-SHA                          RSA        SEED        128      TLS_RSA_WITH_SEED_CBC_SHA
 x41     CAMELLIA128-SHA                   RSA        Camellia    128      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
 xc050   ARIA128-GCM-SHA256                RSA        ARIAGCM     128      TLS_RSA_WITH_ARIA_128_GCM_SHA256
 xc052   DHE-RSA-ARIA128-GCM-SHA256        DH 2048    ARIAGCM     128      TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256
 xc060   ECDHE-ARIA128-GCM-SHA256          ECDH 253   ARIAGCM     128      TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

With switching our SSL certificate to RSA, we gained around 51 new cipher options, amongst them being ones that also mx01.arz.at claimed to support.

FTR, the result from above is what you get with the default settings for postfix v3.5.18, being:

smtpd_tls_ciphers = medium
smtpd_tls_mandatory_ciphers = medium
smtpd_tls_mandatory_exclude_ciphers =
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3

But the delay between triggering the password reset mail and getting a mail server connect was getting bigger and bigger. Therefore while waiting for the next mail to arrive, I decided to capture the network traffic, to be able to look further into this if it should continue to be failing:

% sudo tshark -n -i eth0 -s 65535 -w arz.pcap -f "host 193.110.182.61 or host 193.110.182.62"

A few hours later the mail server connected again, and the mail went through!

postfix/smtpd[4162835]: connect from mx01.arz.at[193.110.182.61]
postfix/smtpd[4162835]: Anonymous TLS connection established from mx01.arz.at[193.110.182.61]: TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)
postfix/smtpd[4162835]: E50D6401E6: client=mx01.arz.at[193.110.182.61]
postfix/smtpd[4162835]: disconnect from mx01.arz.at[193.110.182.61] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7

Now also having the captured network traffic, we can check the details there:

[...]
% tshark -o smtp.decryption:true -r arz.pcap
    1 0.000000000 193.110.182.61 → 203.0.113.42 TCP 74 24699 → 25 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=2261106119 TSecr=0 WS=128
    2 0.000042827 203.0.113.42 → 193.110.182.61 TCP 74 25 → 24699 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3233422181 TSecr=2261106119 WS=128
    3 0.020719269 193.110.182.61 → 203.0.113.42 TCP 66 24699 → 25 [ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=2261106139 TSecr=3233422181
    4 0.022883259 203.0.113.42 → 193.110.182.61 SMTP 96 S: 220 mail.example.com ESMTP
    5 0.043682626 193.110.182.61 → 203.0.113.42 TCP 66 24699 → 25 [ACK] Seq=1 Ack=31 Win=29312 Len=0 TSval=2261106162 TSecr=3233422203
    6 0.043799047 193.110.182.61 → 203.0.113.42 SMTP 84 C: EHLO mx01.arz.at
    7 0.043811363 203.0.113.42 → 193.110.182.61 TCP 66 25 → 24699 [ACK] Seq=31 Ack=19 Win=65280 Len=0 TSval=3233422224 TSecr=2261106162
    8 0.043898412 203.0.113.42 → 193.110.182.61 SMTP 253 S: 250-mail.example.com | PIPELINING | SIZE 20240000 | VRFY | ETRN | AUTH PLAIN | AUTH=PLAIN | ENHANCEDSTATUSCODES | 8BITMIME | DSN | SMTPUTF8 | CHUNKING
    9 0.064625499 193.110.182.61 → 203.0.113.42 SMTP 72 C: QUIT
   10 0.064750257 203.0.113.42 → 193.110.182.61 SMTP 81 S: 221 2.0.0 Bye
   11 0.064760200 203.0.113.42 → 193.110.182.61 TCP 66 25 → 24699 [FIN, ACK] Seq=233 Ack=25 Win=65280 Len=0 TSval=3233422245 TSecr=2261106183
   12 0.085573715 193.110.182.61 → 203.0.113.42 TCP 66 24699 → 25 [FIN, ACK] Seq=25 Ack=234 Win=30336 Len=0 TSval=2261106204 TSecr=3233422245
   13 0.085610229 203.0.113.42 → 193.110.182.61 TCP 66 25 → 24699 [ACK] Seq=234 Ack=26 Win=65280 Len=0 TSval=3233422266 TSecr=2261106204
   14 1799.888108373 193.110.182.61 → 203.0.113.42 TCP 74 10330 → 25 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=2262906007 TSecr=0 WS=128
   15 1799.888161311 203.0.113.42 → 193.110.182.61 TCP 74 25 → 10330 [SYN, ACK] Seq=0 Ack=1 Win=65160 Len=0 MSS=1460 SACK_PERM=1 TSval=3235222069 TSecr=2262906007 WS=128
   16 1799.909030335 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=2262906028 TSecr=3235222069
   17 1799.956621011 203.0.113.42 → 193.110.182.61 SMTP 96 S: 220 mail.example.com ESMTP
   18 1799.977229656 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=1 Ack=31 Win=29312 Len=0 TSval=2262906096 TSecr=3235222137
   19 1799.977229698 193.110.182.61 → 203.0.113.42 SMTP 84 C: EHLO mx01.arz.at
   20 1799.977266759 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=31 Ack=19 Win=65280 Len=0 TSval=3235222158 TSecr=2262906096
   21 1799.977351663 203.0.113.42 → 193.110.182.61 SMTP 267 S: 250-mail.example.com | PIPELINING | SIZE 20240000 | VRFY | ETRN | STARTTLS | AUTH PLAIN | AUTH=PLAIN | ENHANCEDSTATUSCODES | 8BITMIME | DSN | SMTPUTF8 | CHUNKING
   22 1800.011494861 193.110.182.61 → 203.0.113.42 SMTP 76 C: STARTTLS
   23 1800.011589267 203.0.113.42 → 193.110.182.61 SMTP 96 S: 220 2.0.0 Ready to start TLS
   24 1800.032812294 193.110.182.61 → 203.0.113.42 TLSv1 223 Client Hello
   25 1800.032987264 203.0.113.42 → 193.110.182.61 TLSv1.2 2962 Server Hello
   26 1800.032995513 203.0.113.42 → 193.110.182.61 TCP 1266 25 → 10330 [PSH, ACK] Seq=3158 Ack=186 Win=65152 Len=1200 TSval=3235222214 TSecr=2262906151 [TCP segment of a reassembled PDU]
   27 1800.053546755 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=186 Ack=3158 Win=36096 Len=0 TSval=2262906172 TSecr=3235222214
   28 1800.092852469 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=186 Ack=4358 Win=39040 Len=0 TSval=2262906212 TSecr=3235222214
   29 1800.092892905 203.0.113.42 → 193.110.182.61 TLSv1.2 900 Certificate, Server Key Exchange, Server Hello Done
   30 1800.113546769 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=186 Ack=5192 Win=41856 Len=0 TSval=2262906232 TSecr=3235222273
   31 1800.114763363 193.110.182.61 → 203.0.113.42 TLSv1.2 192 Client Key Exchange, Change Cipher Spec, Encrypted Handshake Message
   32 1800.115000416 203.0.113.42 → 193.110.182.61 TLSv1.2 117 Change Cipher Spec, Encrypted Handshake Message
   33 1800.136070200 193.110.182.61 → 203.0.113.42 TLSv1.2 113 Application Data
   34 1800.136155526 203.0.113.42 → 193.110.182.61 TLSv1.2 282 Application Data
   35 1800.158854473 193.110.182.61 → 203.0.113.42 TLSv1.2 162 Application Data
   36 1800.159254794 203.0.113.42 → 193.110.182.61 TLSv1.2 109 Application Data
   37 1800.180286407 193.110.182.61 → 203.0.113.42 TLSv1.2 144 Application Data
   38 1800.223005960 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=5502 Ack=533 Win=65152 Len=0 TSval=3235222404 TSecr=2262906299
   39 1802.230300244 203.0.113.42 → 193.110.182.61 TLSv1.2 146 Application Data
   40 1802.251994333 193.110.182.61 → 203.0.113.42 TCP 2962 [TCP segment of a reassembled PDU]
   41 1802.252034015 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=5582 Ack=3429 Win=63616 Len=0 TSval=3235224433 TSecr=2262908371
   42 1802.252279083 193.110.182.61 → 203.0.113.42 TLSv1.2 1295 Application Data
   43 1802.252288316 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=5582 Ack=4658 Win=64128 Len=0 TSval=3235224433 TSecr=2262908371
   44 1802.272816060 193.110.182.61 → 203.0.113.42 TLSv1.2 833 Application Data, Application Data
   45 1802.272827542 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=5582 Ack=5425 Win=64128 Len=0 TSval=3235224453 TSecr=2262908392
   46 1802.338807683 203.0.113.42 → 193.110.182.61 TLSv1.2 131 Application Data
   47 1802.398968611 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=5425 Ack=5647 Win=44800 Len=0 TSval=2262908518 TSecr=3235224519
   48 1863.257457500 193.110.182.61 → 203.0.113.42 TLSv1.2 101 Application Data
   49 1863.257495688 203.0.113.42 → 193.110.182.61 TCP 66 25 → 10330 [ACK] Seq=5647 Ack=5460 Win=64128 Len=0 TSval=3235285438 TSecr=2262969376
   50 1863.257654942 203.0.113.42 → 193.110.182.61 TLSv1.2 110 Application Data
   51 1863.257721010 203.0.113.42 → 193.110.182.61 TLSv1.2 97 Encrypted Alert
   52 1863.278242216 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [ACK] Seq=5460 Ack=5691 Win=44800 Len=0 TSval=2262969397 TSecr=3235285438
   53 1863.278464176 193.110.182.61 → 203.0.113.42 TCP 66 10330 → 25 [RST, ACK] Seq=5460 Ack=5723 Win=44800 Len=0 TSval=2262969397 TSecr=3235285438

% tshark -O tls -r arz.pcap
[...]
Transport Layer Security
    TLSv1 Record Layer: Handshake Protocol: Client Hello
        Content Type: Handshake (22)
        Version: TLS 1.0 (0x0301)
        Length: 152
        Handshake Protocol: Client Hello
            Handshake Type: Client Hello (1)
            Length: 148
            Version: TLS 1.2 (0x0303)
            Random: 4575d1e7c93c09a564edc00b8b56ea6f5d826f8cfe78eb980c451a70a9c5123f
                GMT Unix Time: Dec  5, 2006 21:09:11.000000000 CET
                Random Bytes: c93c09a564edc00b8b56ea6f5d826f8cfe78eb980c451a70a9c5123f
            Session ID Length: 0
            Cipher Suites Length: 26
            Cipher Suites (13 suites)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (0xc030)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (0xc028)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (0xc027)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014)
                Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013)
                Cipher Suite: TLS_RSA_WITH_AES_256_GCM_SHA384 (0x009d)
                Cipher Suite: TLS_RSA_WITH_AES_128_GCM_SHA256 (0x009c)
                Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA256 (0x003d)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA256 (0x003c)
                Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA (0x0035)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
                Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
[...]
Transport Layer Security
    TLSv1.2 Record Layer: Handshake Protocol: Server Hello
        Content Type: Handshake (22)
        Version: TLS 1.2 (0x0303)
        Length: 89
        Handshake Protocol: Server Hello
            Handshake Type: Server Hello (2)
            Length: 85
            Version: TLS 1.2 (0x0303)
            Random: cf2ed24e3300e95e5f56023bf8b4e5904b862bb2ed8a5796444f574e47524401
                GMT Unix Time: Feb 23, 2080 23:16:46.000000000 CET
                Random Bytes: 3300e95e5f56023bf8b4e5904b862bb2ed8a5796444f574e47524401
            Session ID Length: 32
            Session ID: 63d041b126ecebf857d685abd9d4593c46a3672e1ad76228f3eacf2164f86fb9
            Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (0xc030)
[...]

In this network dump we see what cipher suites are offered, and the TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 here is the Cipher Suite Name in IANA/RFC speak. Whis corresponds to the ECDHE-RSA-AES256-GCM-SHA384 in openssl speak (see Mozilla’s Mozilla’s cipher suite correspondence table), which we also saw in the postfix log.

Mission accomplished! :)

Now, if we’re interested in avoiding certain ciphers and increase security level, we can e.g. get rid of the SEED, CAMELLIA and all anonymous ciphers, and could accept only TLS v1.2 + v1.3, by further adjusting postfix’s main.cf:

smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = aNULL CAMELLIA
smtpd_tls_mandatory_ciphers = high
smtpd_tls_mandatory_protocols = TLSv1.2 TLSv1.3
smtpd_tls_protocols = TLSv1.2 TLSv1.3

Which would then gives us:

% testssl --cipher-per-proto -t=smtp mail.example.com:25
[...]

Hexcode  Cipher Suite Name (OpenSSL)       KeyExch.   Encryption  Bits     Cipher Suite Name (IANA/RFC)
-----------------------------------------------------------------------------------------------------------------------------
SSLv2
SSLv3
TLS 1
TLS 1.1
TLS 1.2
 xc030   ECDHE-RSA-AES256-GCM-SHA384       ECDH 253   AESGCM      256      TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
 xc028   ECDHE-RSA-AES256-SHA384           ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
 xc014   ECDHE-RSA-AES256-SHA              ECDH 253   AES         256      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
 x9f     DHE-RSA-AES256-GCM-SHA384         DH 2048    AESGCM      256      TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
 xcca8   ECDHE-RSA-CHACHA20-POLY1305       ECDH 253   ChaCha20    256      TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xccaa   DHE-RSA-CHACHA20-POLY1305         DH 2048    ChaCha20    256      TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 xc0a3   DHE-RSA-AES256-CCM8               DH 2048    AESCCM8     256      TLS_DHE_RSA_WITH_AES_256_CCM_8
 xc09f   DHE-RSA-AES256-CCM                DH 2048    AESCCM      256      TLS_DHE_RSA_WITH_AES_256_CCM
 x6b     DHE-RSA-AES256-SHA256             DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
 x39     DHE-RSA-AES256-SHA                DH 2048    AES         256      TLS_DHE_RSA_WITH_AES_256_CBC_SHA
 x9d     AES256-GCM-SHA384                 RSA        AESGCM      256      TLS_RSA_WITH_AES_256_GCM_SHA384
 xc0a1   AES256-CCM8                       RSA        AESCCM8     256      TLS_RSA_WITH_AES_256_CCM_8
 xc09d   AES256-CCM                        RSA        AESCCM      256      TLS_RSA_WITH_AES_256_CCM
 x3d     AES256-SHA256                     RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA256
 x35     AES256-SHA                        RSA        AES         256      TLS_RSA_WITH_AES_256_CBC_SHA
 xc051   ARIA256-GCM-SHA384                RSA        ARIAGCM     256      TLS_RSA_WITH_ARIA_256_GCM_SHA384
 xc053   DHE-RSA-ARIA256-GCM-SHA384        DH 2048    ARIAGCM     256      TLS_DHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc061   ECDHE-ARIA256-GCM-SHA384          ECDH 253   ARIAGCM     256      TLS_ECDHE_RSA_WITH_ARIA_256_GCM_SHA384
 xc02f   ECDHE-RSA-AES128-GCM-SHA256       ECDH 253   AESGCM      128      TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 xc027   ECDHE-RSA-AES128-SHA256           ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
 xc013   ECDHE-RSA-AES128-SHA              ECDH 253   AES         128      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
 x9e     DHE-RSA-AES128-GCM-SHA256         DH 2048    AESGCM      128      TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
 xc0a2   DHE-RSA-AES128-CCM8               DH 2048    AESCCM8     128      TLS_DHE_RSA_WITH_AES_128_CCM_8
 xc09e   DHE-RSA-AES128-CCM                DH 2048    AESCCM      128      TLS_DHE_RSA_WITH_AES_128_CCM
 xc0a0   AES128-CCM8                       RSA        AESCCM8     128      TLS_RSA_WITH_AES_128_CCM_8
 xc09c   AES128-CCM                        RSA        AESCCM      128      TLS_RSA_WITH_AES_128_CCM
 x67     DHE-RSA-AES128-SHA256             DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
 x33     DHE-RSA-AES128-SHA                DH 2048    AES         128      TLS_DHE_RSA_WITH_AES_128_CBC_SHA
 x9c     AES128-GCM-SHA256                 RSA        AESGCM      128      TLS_RSA_WITH_AES_128_GCM_SHA256
 x3c     AES128-SHA256                     RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA256
 x2f     AES128-SHA                        RSA        AES         128      TLS_RSA_WITH_AES_128_CBC_SHA
 xc050   ARIA128-GCM-SHA256                RSA        ARIAGCM     128      TLS_RSA_WITH_ARIA_128_GCM_SHA256
 xc052   DHE-RSA-ARIA128-GCM-SHA256        DH 2048    ARIAGCM     128      TLS_DHE_RSA_WITH_ARIA_128_GCM_SHA256
 xc060   ECDHE-ARIA128-GCM-SHA256          ECDH 253   ARIAGCM     128      TLS_ECDHE_RSA_WITH_ARIA_128_GCM_SHA256
TLS 1.3
 x1302   TLS_AES_256_GCM_SHA384            ECDH 253   AESGCM      256      TLS_AES_256_GCM_SHA384
 x1303   TLS_CHACHA20_POLY1305_SHA256      ECDH 253   ChaCha20    256      TLS_CHACHA20_POLY1305_SHA256
 x1301   TLS_AES_128_GCM_SHA256            ECDH 253   AESGCM      128      TLS_AES_128_GCM_SHA256

Don’t forget to also adjust the smpt_tls_* accordingly (for your sending side). For further information see the Postfix TLS Support documentation. Also check out options like tls_ssl_options (setting it to e.g. NO_COMPRESSION) and tls_preempt_cipherlist (setting it to yes would prefer the servers’ order of ciphers over clients).

Conclusions:

• no matter what you change in your mail server settings, be aware that the type of your SSL certificate also matters for what ciphers are offered and used
• there are mail servers out there that don’t support SSL certificates with ECDSA, using RSA for those ensure better compatibility (nowadays postfix supports parallel usage of ECDSA and RSA keys BTW, check out the smtpd_tls_eccert_file + smtpd_tls_eckey_file options)
• testssl is a very useful tool, especially with its –cipher-per-proto -t=smtp option to check SMTP servers
• if you’re uncertain what’s going on, consider capturing network data (tshark/tcpdump/… are your friends)
• review your postfix configuration and logs every now and then :)

Wow, how time flies! 20 years ago grml.org was registered by Mika, and in 2004 we had our first public Grml release. 🥳

We're glad about such a wonderful community and are celebrating this with a small Easter egg in our Grml daily ISOs! 😜

And now for another 20 years? 🤓

Debian v12 with codename bookworm was released as new stable release on 10th of June 2023. Similar to what we had with #newinbullseye and previous releases, now it’s time for #newinbookworm!

I was the driving force at several of my customers to be well prepared for bookworm. As usual with major upgrades, there are some things to be aware of, and hereby I’m starting my public notes on bookworm that might be worth also for other folks. My focus is primarily on server systems and looking at things from a sysadmin perspective.

Further readings

As usual start at the official Debian release notes, make sure to especially go through What’s new in Debian 12 + Issues to be aware of for bookworm.

Package versions

As a starting point, let’s look at some selected packages and their versions in bullseye vs. bookworm as of 2023-02-10 (mainly having amd64 in mind):

Linux Kernel

The bookworm release ships a Linux kernel based on version 6.1, whereas bullseye shipped kernel 5.10. As usual there are plenty of changes in the kernel area, including better hardware support, and this might warrant a separate blog entry, but to highlight some changes:

• a.out support is gone
• initial support for Rust
• lots of io_uring related improvements
• lots of BPF improvements
• support for Intel Software Guard eXtensions (SGX)
• ID mapping for mounted filesystems
• unprivileged overlayfs mounts and ID mapping in overlayfs
• NFS re-exporting support
• eager NFS writes with new writes=lazy/eager/wait mount options
• Landlock security module
• initial support for Apple M2
• new misc cgroup and new cgroup.kill file
• new memfd_secret(2) system call
• new NTFS file system implementation
• file system monitoring with fanotify
• lots of improvements around perf, including the new daemon, kwork and iostat commands, and JSON output option for stat

See Kernelnewbies.org for further changes between kernel versions.

Configuration management

puppet‘s upstream sadly still doesn’t provide packages for bookworm (see PA-4995), though Debian provides puppet-agent and puppetserver packages, and even puppetdb is back again, see release notes for further information.

ansible is also available and made it with version 2.14 into bookworm.

Prometheus stack

Prometheus server was updated from v2.24.1 to v2.42.0 and all the exporters that got shipped with bullseye are still around (in more recent versions of course).

Virtualization

docker (v20.10.24), ganeti (v3.0.2-3), libvirt (v9.0.0-4), lxc (v5.0.2-1), podman (v4.3.1), openstack (Zed), qemu/kvm (v7.2), xen (v4.17.1) are all still around.

Vagrant is available in version 2.3.4, also Vagrant upstream provides their packages for bookworm already.

If you’re relying on VirtualBox, be aware that upstream doesn’t provide packages for bookworm yet (see ticket 21524), but thankfully version 7.0.8-dfsg-2 is available from Debian/unstable (as of 2023-06-10) (VirtualBox isn’t shipped with stable releases since quite some time due to lack of cooperation from upstream on security support for older releases, see #794466).

rsync

rsync was updated from v3.2.3 to v3.2.7, and we got a few new options:

• --fsync: fsync every written file
• --old-dirs: works like –dirs when talking to old rsync
• --old-args: disable the modern arg-protection idiom
• --secluded-args, -s: use the protocol to safely send the args (replaces –protect-args option)
• --trust-sender: trust the remote sender’s file list

OpenSSH

OpenSSH was updated from v8.4p1 to v9.2p1, so if you’re interested in all the changes, check out the release notes between those version (8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1 + 9.2). Let’s highlight some notable new features:

• new system for restricting forwarding and use of keys added to ssh-agent(1), see SSH agent restriction for details)
• switched scp(1) from using the legacy scp/rcp protocol to using the SFTP protocol by default (see release notes for v9.0 for details
• ssh(1): when prompting the user to accept a new hostkey, display any other host names/addresses already associated with the key
• ssh(1): allow UserKnownHostsFile=none to indicate that no known_hosts file should be used to identify host keys
• ssh(1): add a ssh_config KnownHostsCommand option that allows the client to obtain known_hosts data from a command in addition to the usual files
• ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum RSA key length
• ssh(1): add a “host” line to the output of ssh -G showing the original hostname argument
• ssh-keygen -A (generate all default host key types) will no longer generate DSA keys
• ssh-keyscan(1): allow scanning of complete CIDR address ranges, e.g. ssh-keyscan 192.168.0.0/24

One important change you might wanna be aware of is that as of OpenSSH v8.8, RSA signatures using the SHA-1 hash algorithm got disabled by default, but RSA/SHA-256/512 AKA RSA-SHA2 gets used instead. OpenSSH has supported RFC8332 RSA/SHA-256/512 signatures since release 7.2 and existing ssh-rsa keys will automatically use the stronger algorithm where possible. A good overview is also available at SSH: Signature Algorithm ssh-rsa Error.

Now tools/libraries not supporting RSA-SHA2 fail to connect to OpenSSH as present in bookworm. For example python3-paramiko v2.7.2-1 as present in bullseye doesn’t support RSA-SHA2. It tries to connect using the deprecated RSA-SHA-1, which is no longer offered by default with OpenSSH as present in bookworm, and then fails. Support for RSA/SHA-256/512 signatures in Paramiko was requested e.g. at #1734, and eventually got added to Paramiko and in the end the change made it into Paramiko versions >=2.9.0. Paramiko in bookworm works fine, and a backport by rebuilding the python3-paramiko package from bookworm for bullseye solves the problem (BTDT).

Misc unsorted

• new non-free-firmware component/repository (see Debian Wiki for details)
• support only the merged-usr root filesystem layout (see Debian Wiki for details)
• the asterisk package didn’t make it into bookworm (see #1031046)
• e2fsprogs: the breaking change related to metadata_csum_seed and orphan_file (see #1031325) was reverted with v1.47.0-2 for bookworm (also see #1031622 + #1030939)
• rsnapshot is back again (see #986709)
• crmadmin of pacemaker no longer interprets the timeout option (-t/–timeout) in milliseconds (as it used to be until v2.0.5), but as of v2.1.0 (and v2.1.5 is present in bookworm) it now interprets the argument as second by default

Thanks to everyone involved in the release, happy upgrading to bookworm, and let’s continue with working towards Debian/trixie. :)

Die HTU Bigband ist zurück! Am 27. Juni 2023 findet im Innenhof der TU Graz (Alte Technik, Rechbauerstraße 12, 8010 Graz) das nächste Konzert statt (bei Schlechtwetter geht es in den Hörsaal 2, der ebenfalls an der gleichen Adresse ist). Mit einem fulminanten Programm von Swing, über Soul, Funk, Latin bis Pop ist alles dabei – es gibt über 2 Stunden Musik vom Feinsten, und das Ganze bei freiem Eintritt.

Für diejenigen mit Facebook-Account unter euch gibt es auch das passende Facebook-Event.

Ich bin als Schlagzeuger und Percussionist mit von der Partie und würde mich über bekannte Gesichter freuen, ich hoffe man sieht und hört sich! 8-)

Auf den Grazer Linuxtagen 2023 (GLT23) war ich als Referent mit einem Vortrag zum Thema “Debugging für Sysadmins” vertreten. In meinem Vortrag gibt es einen Überblick, welche Tools und Strategien rund ums Debugging in der Toolbox von Sysadmins nicht fehlen dürfen.

Es gibt den Vortrag dank des wunderbaren c3voc-Teams bereits als Videomitschnitt online. Meine Vortragsfolien (1.2MB, PDF) stehen ebenfalls online zur Verfügung. Viel Spaß beim Anschauen!

BTW: weil ich schon mehrfach gefragt wurde, den Vortrag gibt es auch in längerer Workshop-Version, bei Interesse einfach bei mir melden.

While I am not the biggest fan of Docker, I must admit it has quite some reach across various service providers and can often be seen as an API for running things in isolated environments.

One such service provider is GitHub when it comes to their Actions service.

I have no idea what isolation technology GitHub uses on the outside of Actions, but inside you just get an Ubuntu system and can run whatever you want via Docker as that comes pre-installed and pre-configured. This especially means you can run things inside vanilla Debian containers, that are free from any GitHub or Canonical modifications one might not want ;-)

So, if you want to run, say, lintian from sid, you can define a job to do so:

  lintian:
    runs-on: ubuntu-latest
    container: debian:sid
    steps:
      - [ do something to get a package to run lintian on ]
      - run: apt-get update
      - run: apt-get install -y --no-install-recommends lintian
      - run: lintian --info --display-info *.changes

This will run on Ubuntu (latest right now means 22.04 for GitHub), but then use Docker to run the debian:sid container and execute all further steps inside it. Pretty short and straight forward, right?

Now lintian does static analysis of the package, it doesn't need to install it. What if we want to run autopkgtest that performs tests on an actually installed package?

autopkgtest comes with various "virt servers", which are providing isolation of the testbed, so that it does not interfere with the host system. The simplest available virt server, autopkgtest-virt-null doesn't actually provide any isolation, as it runs things directly on the host system. This might seem fine when executed inside an ephemeral container in an CI environment, but it also means that multiple tests have the potential to influence each other as there is no way to revert the testbed to a clean state. For that, there are other, "real", virt servers available: chroot, lxc, qemu, docker and many more. They all have one in common: to use them, one needs to somehow provide an "image" (a prepared chroot, a tarball of a chroot, a vm disk, a container, …, you get it) to operate on and most either bring a tool to create such an "image" or rely on a "registry" (online repository) to provide them.

Most users of autopkgtest on GitHub (that I could find with their terrible search) are using either the null or the lxd virt servers. Probably because these are dead simple to set up (null) or the most "native" (lxd) in the Ubuntu environment.

As I wanted to execute multiple tests that for sure would interfere with each other, the null virt server was out of the discussion pretty quickly.

The lxd one also felt odd, as that meant I'd need to set up lxd (can be done in a few commands, but still) and it would need to download stuff from Canonical, incurring costs (which I couldn't care less about) and taking time which I do care about!).

Enter autopkgtest-virt-docker, which recently was added to autopkgtest! No need to set things up, as GitHub already did all the Docker setup for me, and almost no waiting time to download the containers, as GitHub does heavy caching of stuff coming from Docker Hub (or at least it feels like that).

The only drawback? It was added in autopkgtest 5.23, which Ubuntu 22.04 doesn't have. "We need to go deeper" and run autopkgtest from a sid container!

With this idea, our current job definition would look like this:

  autopkgtest:
    runs-on: ubuntu-latest
    container: debian:sid
    steps:
      - [ do something to get a package to run autopkgtest on ]
      - run: apt-get update
      - run: apt-get install -y --no-install-recommends autopkgtest autodep8 docker.io
      - run: autopkgtest *.changes --setup-commands="apt-get update" -- docker debian:sid

(--setup-commands="apt-get update" is needed as the container comes with an empty apt cache and wouldn't be able to find dependencies of the tested package)

However, this will fail:

# autopkgtest *.changes --setup-commands="apt-get update" -- docker debian:sid
autopkgtest [10:20:54]: starting date and time: 2023-04-07 10:20:54+0000
autopkgtest [10:20:54]: version 5.28
autopkgtest [10:20:54]: host a82a11789c0d; command line:
  /usr/bin/autopkgtest bley_2.0.0-1_amd64.changes '--setup-commands=apt-get update' -- docker debian:sid
Unexpected error:
Traceback (most recent call last):
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 829, in mainloop
    command()
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 758, in command
    r = f(c, ce)
        ^^^^^^^^
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 692, in cmd_copydown
    copyupdown(c, ce, False)
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 580, in copyupdown
    copyupdown_internal(ce[0], c[1:], upp)
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 607, in copyupdown_internal
    copydown_shareddir(sd[0], sd[1], dirsp, downtmp_host)
  File "/usr/share/autopkgtest/lib/VirtSubproc.py", line 562, in copydown_shareddir
    shutil.copy(host, host_tmp)
  File "/usr/lib/python3.11/shutil.py", line 419, in copy
    copyfile(src, dst, follow_symlinks=follow_symlinks)
  File "/usr/lib/python3.11/shutil.py", line 258, in copyfile
    with open(dst, 'wb') as fdst:
         ^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/autopkgtest-virt-docker.shared.kn7n9ioe/downtmp/wrapper.sh'
autopkgtest [10:21:07]: ERROR: testbed failure: unexpected eof from the testbed

Running the same thing locally of course works, so there has to be something special about the setup at GitHub. But what?!

A bit of digging revealed that autopkgtest-virt-docker tries to use a shared directory (using Dockers --volume) to exchange things with the testbed (for the downtmp-host capability). As my autopkgtest is running inside a container itself, nothing it tells the Docker deamon to mount will be actually visible to it.

In retrospect this makes total sense and autopkgtest-virt-docker has a switch to "fix" the issue: --remote as the Docker deamon is technically remote when viewed from the place autopkgtest runs at.

I'd argue this is not a bug in autopkgtest(-virt-docker), as the situation is actually cared for. There is even some auto-detection of "remote" daemons in the code, but that doesn't "know" how to detect the case where the daemon socket is mounted (vs being set as an environment variable). I've opened an MR (assume remote docker when running inside docker) which should detect the case of running inside a Docker container which kind of implies the daemon is remote.

Not sure the patch will be accepted (it is a band-aid after all), but in the meantime I am quite happy with using --remote and so could you ;-)

Update on 2023-03-23: thanks to Daniel Roschka for mentioning the Mandos and TPM approaches, which might be better alternatives, depending on your options and needs. Peter Palfrader furthermore pointed me towards clevis-initramfs and tang.

A customer of mine runs dedicated servers inside a foreign data-center, remote hands only. In such an environment you might need a disk replacement because you need bigger or faster disks, though also a disk might (start to) fail and you need a replacement. One has to be prepared for such a scenario, but fully wiping your used disk then might not always be an option, especially once disks (start to) fail. On the other hand you don’t want to end up with (partial) data on your disk handed over to someone unexpected.

By encrypting the data on your disks upfront you can prevent against this scenario. But if you have a fleet of servers you might not want to manually jump on servers during boot and unlock crypto volumes manually. It’s especially annoying if it’s about the root filesystem where a solution like dropbear-initramfs needs to be used for remote access during initramfs boot stage. So my task for the customer was to adjust encrypted LUKS devices such that no one needs to manually unlock the encrypted device during server boot (with some specific assumptions about possible attack vectors one has to live with, see the disclaimer at the end).

The documentation about this use-case was rather inconsistent, especially because special rules apply for the root filesystem (no key file usage), we see different behavior between what’s supported by systemd (hello key file again), initramfs-tools and dracut, not to mention the changes between different distributions. Since tests with this tend to be rather annoying (better make sure to have a Grml live system available :)), I’m hereby documenting what worked for us (Debian/bullseye with initramfs-tools and cryptsetup-initramfs).

The system was installed with LVM on-top of an encrypted Software-RAID device, only the /boot partition is unencrypted. But even if you don’t use Software-RAID nor LVM the same instructions apply. The system looks like this:

% mount -t ext4 -l
/dev/mapper/foobar-root_1 on / type ext4 (rw,relatime,errors=remount-ro)

% sudo pvs
  PV                    VG     Fmt  Attr PSize   PFree
  /dev/mapper/md1_crypt foobar lvm2 a--  445.95g 430.12g

% sudo vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  foobar   1   2   0 wz--n- 445.95g 430.12g

% sudo lvs
  LV     VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root_1 foobar -wi-ao---- <14.90g

% lsblk
NAME                  MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
[...]
sdd                     8:48   0 447.1G  0 disk
├─sdd1                  8:49   0   571M  0 part  /boot/efi
├─sdd2                  8:50   0   488M  0 part
│ └─md0                 9:0    0   487M  0 raid1 /boot
└─sdd3                  8:51   0 446.1G  0 part
  └─md1                 9:1    0   446G  0 raid1
    └─md1_crypt       253:0    0   446G  0 crypt
      ├─foobar-root_1 253:1    0  14.9G  0 lvm   /
[...]
sdf                     8:80   0 447.1G  0 disk
├─sdf1                  8:81   0   571M  0 part
├─sdf2                  8:82   0   488M  0 part
│ └─md0                 9:0    0   487M  0 raid1 /boot
└─sdf3                  8:83   0 446.1G  0 part
  └─md1                 9:1    0   446G  0 raid1
    └─md1_crypt       253:0    0   446G  0 crypt
      ├─foobar-root_1 253:1    0  14.9G  0 lvm   /

The actual crypsetup configuration is:

% cat /etc/crypttab
md1_crypt UUID=77246138-b666-4151-b01c-5a12db54b28b none luks,discard

Now, to automatically open the crypto device during boot we can instead use:

% cat /etc/crypttab 
md1_crypt UUID=77246138-b666-4151-b01c-5a12db54b28b none luks,discard,keyscript=/etc/initramfs-tools/unlock.sh

# touch /etc/initramfs-tools/unlock.sh
# chmod 0700 /etc/initramfs-tools/unlock.sh
# $EDITOR etc/initramfs-tools/unlock.sh
# cat /etc/initramfs-tools/unlock.sh
#!/bin/sh
echo -n "provide_the_actual_password_here"

# update-initramfs -k all -u
[...]

The server will then boot without prompting for a crypto password.

Note that initramfs-tools by default uses an insecure umask of 0022, resulting in the initrd being accessible to everyone. But if you have the dropbear-initramfs package installed, its `/usr/share/initramfs-tools/conf-hooks.d/dropbear` sets `UMASK=0077`, so the resulting /boot/initrd* file should automatically have proper permissions (0600). The cryptsetup hook warns about a permissive umask configuration during update-initramfs runs, but if you want to be sure, explicitly set it via e.g.:

# cat > /etc/initramfs-tools/conf.d/umask << EOF
# restrictive umask to avoid non-root access to initrd:
UMASK=0077
EOF
# update-initramfs -k all -u

Disclaimer: Of course you need to trust users with access to /etc/initramfs-tools/unlock.sh as well as the initramfs/initrd on your system. Furthermore you should wipe the boot partition (to destroy the keyfile information) before handing over such a disk. But that is a risk my customer can live with, YMMV.

Ich habe 2022 keine Bookdumps geschrieben, weil es mir einerseits zu viel Aufwand war, andererseits wollte ich mir auch nicht immer bzw. zeitnahe zu jedem Buch eine Meinung bilden (müssen). 2022 war aus verschiedenen Gründen intensiv, daher habe ich meine Lese-Gewohnheit von 2021 nicht ganz halten können, aber schlussendlich sind es doch 82 Bücher (ca. 19k Seiten) geworden.

Im Gegensatz zu den Vorjahren habe ich diesmal nicht auf das Verhältnis von Autorin zu Autor geachtet, und entsprechend sind es leider auch nur 27 Autorinnen zu 55 Autoren geworden. Ich bin leider noch immer ziemlich schlecht beim Abbrechen von Büchern, aber es waren fast alle Bücher gut. Daher hier nur eine kleine Auswahl jener Bücher, die ich besonders lesenswert fand bzw. empfehlen möchte (die Reihenfolge entspricht dem Foto und stellt keinerlei Reihung oder dergleichen dar):

• Maksym, Dirk Stermann. Ein wichtiges Thema (Aufteilung der Kinderbetreuung) ist hier in eine unterhaltsam zu lesende Autofiktion verpackt. Das Buch hat meinen Humor im Sommerurlaub perfekt getroffen und wer mit kabarettistischem Humor kein Problem hat, sollte hier nicht enttäuscht werden.
• Müll (Brenner #9), Wolf Haas. Ich hatte zuvor noch kein Buch von Haas gelesen, weil ich einmal den Spruch “wenn man nicht weiß was man lesen soll greift man zu Haas” aufgeschnappt habe und mich damit nicht angesprochen fühlte. Großer Fehler, Hilfsausdruck. Auf Empfehlung von Daniela Strigl hin habe ich mir den neuesten Brenner-Roman von Haas besorgt und fühlte mich total abgeholt. Ich habe darauf hin gleich weitere Bücher von Haas gelesen. Danke für den Stupser, Frau Strigl.
• Eine runde Sache, Tomer Gardi. Zwei Geschichten in einem Buch die miteinander lose verbunden sind – zuerst eine Odyssee mit einem Schäferhund in gebrochenem Deutsch, dann die Lebensgeschichte des indonesischen Malers Raden Saleh von Java. Danke für die Empfehlung, Insa Wilke.
• Das blinde Licht, Benjamín Labatut. In vier Geschichten erzählt Benjamín Labatut vom schmalen Grat zwischen Genie und Wahnsinn, von menschlicher Hybris und der zwiespältigen Kraft der Wissenschaft. Ein wunderbares Buch, das ich nur aufs Wärmste weiterempfehlen kann.
• Die verschissene Zeit, Barbi Marković. Ein wunderbarer popkultureller Ausflug in das Belgrad der Neunziger.
• Coventry: Essays, Rachel Cusk. Unaufgeregte Beobachtungen des Alltags die zum Denken anregen. Ich bin leider erst im Nachhinein drauf gekommen, dass die deutsche Übersetzung wohl um einige Kapitel gekürzt ist, sprachlich hat mich die deutsche Ausgabe trotzdem absolut abgeholt.
• Das hier ist Wasser / This is water, David Foster Wallace. Ein 64 Seiten schlankes Buch, das im ersten Teil die deutsche Übersetzung und im zweiten Teil das englische Original beinhaltet. Inspirierende Gedanken rund um Bildung, Denken und Leben.
• Kummer aller Art, Mariana Leky. Mir war noch Lekys “Was man von hier aus sehen kann” in guter Erinnerung, hatte die Autorin aber irgendwie aus den Augen verloren. Dieses Buch war ein Weihnachtsgeschenk an mich – und wow, was für ein Volltreffer. Ein fantastisches Buch, ich habe mir umgehend weitere Bücher von Mariana Leky besorgt. Klare Leseempfehlung.
• Was ist der Mensch? Ein Gespräch über die Welt und Gott, Mark Twain. Ein philosophisches Zwiegespräch über den freien Willen des Menschen. Sehr anregend, danke für die Empfehlung, Darsha.
• Herr Lehmann (Frank Lehmann #1), Sven Regener. Das Buch wurde 2001 veröffentlicht und 2003 verfilmt, hat es aber erst 2022 auf mein Buchregal geschafft. Für mich hat sich in der Sommerzeit mit diesem Buch ein wunderbarer Lesesog ergeben, ich habe daraufhin gleich weitere Bücher von Regener besorgt und gelesen.
• Reise durch Ruinen, George Orwell. Orwell folgte als Kriegsberichterstatter den alliierten Streitkräften durch Deutschland und Österreich. Naturgemäß keine leichte Kost.
• On Writing: A Memoir of the Craft, Stephen King. Dank eines Geburtstagsgeschenks (thx, Kathi + Karl!) habe ich 2022 endlich den Kosmos “Stephen King” betreten. Sprachlich hat mich in “Finderlohn“, der deutschen Ausgabe von “Finders Keepers” aber irgendetwas irritiert, ohne es wirklich benennen zu können. Im Zuge des Lesens von “On Writing: A Memoir of the Craft” habe ich stellenweise das englischsprachige Original mit dessen deutscher Übersetzung “Das Leben und das Schreiben” verglichen und festgestellt, dass ich den “englischen King” unvergleichlich lesenswerter empfinde. Dieses Buch gibt einen lesenswerten Einblick in den Werdegang von King und seinem Zugang zum Schreiben. Und ich möchte hier ganz klar für die englische Ausgabe dieses Buches werben.

This Grml release provides fresh software packages from Debian bookworm. As usual it also incorporates current hardware support and fixes known bugs from previous Grml releases.

More information is available in the release notes of Grml 2022.11.

Grab the latest Grml ISO(s) and spread the word!

Thanks to everyone contributing to Grml and this release, stay healthy and happy Grml-ing!

We are proud to announce the first release candidate of the upcoming version 2022.11, code-named 'MalGuckes'!

This Grml release provides fresh software packages from Debian bookworm. As usual it also incorporates current hardware support and fixes known bugs from the previous Grml release.

For detailed information about the changes between 2021.07 and 2022.11(-rc1) have a look at the official release announcement.

Please test the ISOs and everything you usually use and rely on, and report back, so we can complete the stable release soon. If no major problems come up, the next iteration will be the stable release, which is scheduled for end of November 2022.