update postfix settings due to DROWN attack

diff --git a/src/configuration/MailServers/Postfix/main.cf b/src/configuration/MailServers/Postfix/main.cf
index cd7b9b0..11934b3 100644 (file)
--- a/src/configuration/MailServers/Postfix/main.cf
+++ b/src/configuration/MailServers/Postfix/main.cf
@@ -32,7 +32,16 @@ smtp_tls_loglevel = 1
 smtpd_tls_auth_only = yes
 tls_ssl_options = NO_COMPRESSION
 
 smtpd_tls_auth_only = yes
 tls_ssl_options = NO_COMPRESSION
 

+# be explicit about turning off SSLv2 / v3 due to the DROWN attack
+smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
+smtp_tls_protocols = !SSLv2, !SSLv3
+
+lmtp_tls_mandatory_protocols = !SSLv2, !SSLv3
+lmtp_tls_protocols = !SSLv2, !SSLv3
+

 smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
 smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3

+smtpd_tls_protocols = !SSLv2, !SSLv3
+

 smtpd_tls_mandatory_ciphers=high
 tls_high_cipherlist=EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA256:EECDH:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!DSS:!RC4:!SEED:!IDEA:!ECDSA:kEDH:CAMELLIA128-SHA:AES128-SHA
 smtpd_tls_eecdh_grade=ultra
 smtpd_tls_mandatory_ciphers=high
 tls_high_cipherlist=EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA256:EECDH:+CAMELLIA128:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!DSS:!RC4:!SEED:!IDEA:!ECDSA:kEDH:CAMELLIA128-SHA:AES128-SHA
 smtpd_tls_eecdh_grade=ultra

diff --git a/src/practical_settings/mailserver.tex b/src/practical_settings/mailserver.tex
index bafe904..2534046 100644 (file)
--- a/src/practical_settings/mailserver.tex
+++ b/src/practical_settings/mailserver.tex
@@ -17,7 +17,7 @@ Office Protocol (POP).
 
 As MSAs and MTAs both use SMTP as transfer protocols, both functionalities may
 often may be implemented with the same software. On the other hand, MDA software
 
 As MSAs and MTAs both use SMTP as transfer protocols, both functionalities may
 often may be implemented with the same software. On the other hand, MDA software

-may or may not implement both IMAP and POP.
+might or might not implement both IMAP and POP.

 
 %% ----------------------------------------------------------------------
 \subsection{TLS usage in mail server protocols}
 
 %% ----------------------------------------------------------------------
 \subsection{TLS usage in mail server protocols}


@@ -50,6 +50,8 @@ We recommend to use the following settings for Mail Transfer Agents:
   \item do not use self signed certificates
   \item accept all cipher suites, as the alternative would be to fall back to
     cleartext transmission
   \item do not use self signed certificates
   \item accept all cipher suites, as the alternative would be to fall back to
     cleartext transmission

+  \item an execption to the last sentence is that MTAs \textit{MUST NOT} 
+    enable SSLv2 protocol support, due to the DROWN attack\footnote{\url{https://drownattack.com/drown-attack-paper.pdf}}.

 \end{itemize*}
 
 For MSA operation we recommend:
 \end{itemize*}
 
 For MSA operation we recommend:


@@ -58,7 +60,7 @@ For MSA operation we recommend:
   \item optionally listen on port 465 with Implicit TLS
   \item enforce SMTP AUTH even for local networks
   \item ensure that SMTP AUTH is not allowed on unencrypted connections
   \item optionally listen on port 465 with Implicit TLS
   \item enforce SMTP AUTH even for local networks
   \item ensure that SMTP AUTH is not allowed on unencrypted connections

-  \item use the recommended cipher suites if all connecting MUAs support them
+  \item only use the recommended cipher suites if all connecting MUAs support them

 \end{itemize*}
 
 For MDA operation we recommend:
 \end{itemize*}
 
 For MDA operation we recommend:


@@ -69,6 +71,7 @@ For MDA operation we recommend:
   \item enforce authentication even for local networks
   \item make sure that authentication is not allowed on unencrypted connections
   \item use the recommended cipher suites if all connecting MUAs support them
   \item enforce authentication even for local networks
   \item make sure that authentication is not allowed on unencrypted connections
   \item use the recommended cipher suites if all connecting MUAs support them

+  \item turn off SSLv2 (DROWN attack\footnote{\url{https://drownattack.com/drown-attack-paper.pdf}})

 \end{itemize*}
 
 %% ----------------------------------------------------------------------
 \end{itemize*}
 
 %% ----------------------------------------------------------------------


@@ -245,7 +248,7 @@ For the MSA \verb|smtpd| process which communicates with mail clients, we first
 define the ciphers that are acceptable for the ``mandatory'' security level,
 again in \verb|main.cf|:
 
 define the ciphers that are acceptable for the ``mandatory'' security level,
 again in \verb|main.cf|:
 

-\configfile{main.cf}{35-37}{MSA TLS configuration in Postfix}
+\configfile{main.cf}{36-45}{MSA TLS configuration in Postfix}

 
 Then, we configure the MSA smtpd in \verb|master.cf| with two
 additional options that are only used for this instance of smtpd:
 
 Then, we configure the MSA smtpd in \verb|master.cf| with two
 additional options that are only used for this instance of smtpd:


@@ -253,7 +256,7 @@ additional options that are only used for this instance of smtpd:
 \configfile{master.cf}{12-14}{MSA smtpd service configuration in Postfix}
 
 For those users who want to use EECDH key exchange, it is possible to customize this via:
 \configfile{master.cf}{12-14}{MSA smtpd service configuration in Postfix}
 
 For those users who want to use EECDH key exchange, it is possible to customize this via:

-\configfile{main.cf}{38-38}{EECDH customization in Postfix}
+\configfile{main.cf}{46-46}{EECDH customization in Postfix}

 The default value since Postfix 2.8 is ``strong''.
 
 \subsubsection{Limitations}
 The default value since Postfix 2.8 is ``strong''.
 
 \subsubsection{Limitations}