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<div class="moz-cite-prefix">Am 24.09.2024 um 08:47 schrieb
gnitzsche via Postfixbuch-users:<br>
</div>
<blockquote type="cite"
cite="mid:e0b5fe5ef23b891412f8468353f405ce@netcologne.de">
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<p id="reply-intro">On 2024-09-24 07:43, Frank Kirschner via
Postfixbuch-users wrote:</p>
<blockquote type="cite"
style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div id="replybody1">
<div>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Hallo
zusammen,</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Ich
kann von einer großen Versicherung keine Emails
empfangen (Postfix 2.10.1):</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Sep
24 06:17:52 farm11 postfix/smtpd[2767072]: warning: TLS
library problem: 2767072:error:1408A0C1:SSL
routines:ssl3_get_client_hello:no shared
cipher:s3_srvr.c:1435:<br>
Sep 24 06:17:52 farm11 postfix/smtpd[2767072]: lost
connection after STARTTLS from
mail1.gothaer.de[194.126.228.24]<br>
Sep 24 06:17:52 farm11 postfix/smtpd[2767072]:
disconnect from mail1.gothaer.de[194.126.228.24]</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Der
Grund hierfür ist, dass meine SSL Konfig so aussieht:</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">smtpd_tls_mandatory_protocols
= !SSLv2, !SSLv3, !TLSv1, !TLSv1.1<br>
smtpd_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1<br>
smtpd_tls_mandatory_ciphers = medium</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Ich
interpretiere das Problem daher, dass der sendende MTA
SSLv3 verwendet, welches ich ja nicht erlaube.<br>
OpenSSL ist wie folgt compiliert:</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">[op1@farm11]#
openssl ciphers -v | awk '{print $2}' | sort | uniq<br>
SSLv3<br>
TLSv1.2</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Gibt
es eine Möglichkeit nur für diesen sendenden Host SSLv3
zu erlauben? <br>
Er scheint auch kein Fallback auf unverschlüsselt
konfiguriert zu haben, da ich </span><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">smtpd_tls_mandatory_ciphers
= medium eingestellt habe und somit die Chance dazu
wäre.</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Oder
bin ich auf einem komplett falschen Weg?</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">lg
Frank<br>
</span></p>
</div>
</div>
</blockquote>
<p><br>
</p>
<p>Denke, das liegt an dem "<span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">no
shared cipher". </span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Hier
kommt mail1.gothaer.de an mit TLSv1.2 mit Cipher
DHE-RSA-AES256-GCM-SHA384 (256/256 bits)</span></p>
</blockquote>
<p>Hmm, folgende cipherlist habe ich konfiguriert:<br>
</p>
<p>tls_medium_cipherlist =
ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384</p>
<p>Die <span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">DHE-RSA-AES256-GCM-SHA384
habe ich am Ende der Liste ja eigentlich drin. <br>
</span></p>
<p><span
style="font-family: Helvetica, Arial, sans-serif; font-size: small;">Wenn
ich per testssl.sh mir die verfügbaren cipher unter TLS 1.2 für
den Server an Port 25 ansehe, fehlt dieses aber:</span></p>
<p>TLSv1.2 (server order)<br>
xc019 AECDH-AES256-SHA ECDH 256 AES
256 TLS_ECDH_anon_WITH_AES_256_CBC_SHA<br>
xa7 ADH-AES256-GCM-SHA384 DH 2048 AESGCM
256 TLS_DH_anon_WITH_AES_256_GCM_SHA384<br>
x6d ADH-AES256-SHA256 DH 2048 AES
256 TLS_DH_anon_WITH_AES_256_CBC_SHA256<br>
x3a ADH-AES256-SHA DH 2048 AES
256 TLS_DH_anon_WITH_AES_256_CBC_SHA<br>
x89 ADH-CAMELLIA256-SHA DH 2048 Camellia
256 TLS_DH_anon_WITH_CAMELLIA_256_CBC_SHA<br>
xc02c ECDHE-ECDSA-AES256-GCM-SHA384 ECDH 256 AESGCM
256 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384<br>
xc024 ECDHE-ECDSA-AES256-SHA384 ECDH 256 AES
256 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384<br>
xc00a ECDHE-ECDSA-AES256-SHA ECDH 256 AES
256 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA<br>
xc018 AECDH-AES128-SHA ECDH 256 AES
128 TLS_ECDH_anon_WITH_AES_128_CBC_SHA<br>
xa6 ADH-AES128-GCM-SHA256 DH 2048 AESGCM
128 TLS_DH_anon_WITH_AES_128_GCM_SHA256<br>
x6c ADH-AES128-SHA256 DH 2048 AES
128 TLS_DH_anon_WITH_AES_128_CBC_SHA256<br>
x34 ADH-AES128-SHA DH 2048 AES
128 TLS_DH_anon_WITH_AES_128_CBC_SHA<br>
x9b ADH-SEED-SHA DH 2048 SEED
128 TLS_DH_anon_WITH_SEED_CBC_SHA<br>
x46 ADH-CAMELLIA128-SHA DH 2048 Camellia
128 TLS_DH_anon_WITH_CAMELLIA_128_CBC_SHA<br>
xc02b ECDHE-ECDSA-AES128-GCM-SHA256 ECDH 256 AESGCM
128 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256<br>
xc023 ECDHE-ECDSA-AES128-SHA256 ECDH 256 AES
128 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256<br>
xc009 ECDHE-ECDSA-AES128-SHA ECDH 256 AES
128 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA<br>
xc017 AECDH-DES-CBC3-SHA ECDH 256 3DES
168 TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA<br>
x1b ADH-DES-CBC3-SHA DH 2048 3DES
168 TLS_DH_anon_WITH_3DES_EDE_CBC_SHA<br>
xc008 ECDHE-ECDSA-DES-CBC3-SHA ECDH 256 3DES
168 TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA<br>
xc016 AECDH-RC4-SHA ECDH 256 RC4
128 TLS_ECDH_anon_WITH_RC4_128_SHA<br>
x18 ADH-RC4-MD5 DH 2048 RC4
128 TLS_DH_anon_WITH_RC4_128_MD5<br>
xc007 ECDHE-ECDSA-RC4-SHA ECDH 256 RC4
128 TLS_ECDHE_ECDSA_WITH_RC4_128_SHA</p>
<p><br>
</p>
<p>Openssl stellt aber DHE-RSA-AES256-GCM-SHA384 zur Verfügung:<br>
</p>
<p># openssl ciphers -v \<br>
>
'aNULL:-aNULL:kEECDH:kEDH:+RC4:!eNULL:!EXPORT:!LOW:@STRENGTH' |<br>
> awk '{printf "%-32s %s\n", $1, $3}'<br>
AECDH-AES256-SHA Kx=ECDH<br>
ECDHE-RSA-AES256-GCM-SHA384 Kx=ECDH<br>
ECDHE-ECDSA-AES256-GCM-SHA384 Kx=ECDH<br>
ECDHE-RSA-AES256-SHA384 Kx=ECDH<br>
ECDHE-ECDSA-AES256-SHA384 Kx=ECDH<br>
ECDHE-RSA-AES256-SHA Kx=ECDH<br>
ECDHE-ECDSA-AES256-SHA Kx=ECDH<br>
ADH-AES256-GCM-SHA384 Kx=DH<br>
ADH-AES256-SHA256 Kx=DH<br>
ADH-AES256-SHA Kx=DH<br>
ADH-CAMELLIA256-SHA Kx=DH<br>
DHE-DSS-AES256-GCM-SHA384 Kx=DH<br>
DHE-RSA-AES256-GCM-SHA384 Kx=DH<br>
DHE-RSA-AES256-SHA256 Kx=DH<br>
DHE-DSS-AES256-SHA256 Kx=DH<br>
DHE-RSA-AES256-SHA Kx=DH<br>
DHE-DSS-AES256-SHA Kx=DH<br>
DHE-RSA-CAMELLIA256-SHA Kx=DH<br>
DHE-DSS-CAMELLIA256-SHA Kx=DH<br>
AECDH-AES128-SHA Kx=ECDH<br>
ECDHE-RSA-AES128-GCM-SHA256 Kx=ECDH<br>
ECDHE-ECDSA-AES128-GCM-SHA256 Kx=ECDH<br>
ECDHE-RSA-AES128-SHA256 Kx=ECDH<br>
ECDHE-ECDSA-AES128-SHA256 Kx=ECDH<br>
ECDHE-RSA-AES128-SHA Kx=ECDH<br>
ECDHE-ECDSA-AES128-SHA Kx=ECDH<br>
ADH-AES128-GCM-SHA256 Kx=DH<br>
ADH-AES128-SHA256 Kx=DH<br>
ADH-AES128-SHA Kx=DH<br>
ADH-SEED-SHA Kx=DH<br>
ADH-CAMELLIA128-SHA Kx=DH<br>
DHE-DSS-AES128-GCM-SHA256 Kx=DH<br>
DHE-RSA-AES128-GCM-SHA256 Kx=DH<br>
DHE-RSA-AES128-SHA256 Kx=DH<br>
DHE-DSS-AES128-SHA256 Kx=DH<br>
DHE-RSA-AES128-SHA Kx=DH<br>
DHE-DSS-AES128-SHA Kx=DH<br>
DHE-RSA-SEED-SHA Kx=DH<br>
DHE-DSS-SEED-SHA Kx=DH<br>
DHE-RSA-CAMELLIA128-SHA Kx=DH<br>
DHE-DSS-CAMELLIA128-SHA Kx=DH<br>
AECDH-DES-CBC3-SHA Kx=ECDH<br>
ECDHE-RSA-DES-CBC3-SHA Kx=ECDH<br>
ECDHE-ECDSA-DES-CBC3-SHA Kx=ECDH<br>
ADH-DES-CBC3-SHA Kx=DH<br>
EDH-RSA-DES-CBC3-SHA Kx=DH<br>
EDH-DSS-DES-CBC3-SHA Kx=DH<br>
AECDH-RC4-SHA Kx=ECDH<br>
ECDHE-RSA-RC4-SHA Kx=ECDH<br>
ECDHE-ECDSA-RC4-SHA Kx=ECDH<br>
ADH-RC4-MD5 Kx=DH</p>
<p>Habe ich irgend etwas falsch angegeben?<br>
</p>
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