option.
+.new
+.option dane_require_tls_ciphers smtp string&!! unset
+.cindex "TLS" "requiring specific ciphers for DANE"
+.cindex "cipher" "requiring specific"
+.cindex DANE "TLS ciphers"
+This option may be used to override &%tls_require_ciphers%& for connections
+where DANE has been determined to be in effect.
+If not set, then &%tls_require_ciphers%& will be used.
+Normal SMTP delivery is not able to make strong demands of TLS cipher
+configuration, because delivery will fall back to plaintext. Once DANE has
+been determined to be in effect, there is no plaintext fallback and making the
+TLS cipherlist configuration stronger will increase security, rather than
+counter-intuitively decreasing it.
+If the option expands to be empty or is forced to fail, then it will
+be treated as unset and &%tls_require_ciphers%& will be used instead.
+.wen
+
+
.option data_timeout smtp time 5m
This sets a timeout for the transmission of each block in the data portion of
the message. As a result, the overall timeout for a message depends on the size
to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
DNSSEC.
2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
-3) offer a server certificate, or certificate chain, in TLS connections which is traceable to the one
-defined by (one of?) the TSLA records
+3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
There are no changes to Exim specific to server-side operation of DANE.
Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
-For client-side DANE there are two new smtp transport options, &%hosts_try_dane%& and &%hosts_require_dane%&.
-The latter variant will result in failure if the target host is not DNSSEC-secured.
+For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
+and &%dane_require_tls_ciphers%&.
+The require variant will result in failure if the target host is not DNSSEC-secured.
DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
will be required for the host. If it does not, the host will not
be used; there is no fallback to non-DANE or non-TLS.
+If DANE is requested and usable, then the TLS cipher list configuration
+prefers to use the option &%dane_require_tls_ciphers%& and falls
+back to &%tls_require_ciphers%& only if that is unset.
+This lets you configure "decent crypto" for DANE and "better than nothing
+crypto" as the default. Note though that while GnuTLS lets the string control
+which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
+limited to ciphersuite constraints.
+
If DANE is requested and useable (see above) the following transport options are ignored:
.code
hosts_require_tls
There is a new variable &$tls_out_dane$& which will have "yes" if
verification succeeded using DANE and "no" otherwise (only useful
-in combination with EXPERIMENTAL_EVENT), and a new variable &$tls_out_tlsa_usage$& (detailed above).
+in combination with events; see &<<CHAPevents>>&),
+and a new variable &$tls_out_tlsa_usage$& (detailed above).
+
+.cindex DANE reporting
+An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
+to achieve DANE-verified connection, if one was either requested and offered, or
+required. This is intended to support TLS-reporting as defined in
+&url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
+The &$event_data$& will be one of the Result Types defined in
+Section 4.3 of that document.
Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
.wen
.vitem &%avast%&
.cindex "virus scanners" "avast"
This is the scanner daemon of Avast. It has been tested with Avast Core
-Security (currently at version 1.1.7).
-You can get a trial version at &url(http://www.avast.com) or for Linux
-at &url(http://www.avast.com/linux-server-antivirus).
+Security (currently at version 2.2.0).
+You can get a trial version at &url(https://www.avast.com) or for Linux
+at &url(https://www.avast.com/linux-server-antivirus).
This scanner type takes one option,
which can be either a full path to a UNIX socket,
or host and port specifiers separated by white space.
PACK
.endd
+Only the first virus detected will be reported.
+
.vitem &%aveserver%&
.cindex "virus scanners" "Kaspersky"
This might, for instance, be done to enforce a policy restriction on
hash-method or key-size:
.code
- warn condition = ${if eq {$dkim_algo}{rsa-sha1}}
- condition = ${if eq {$dkim_verify_status}{pass}}
+ warn condition = ${if eq {$dkim_verify_status}{pass}}
+ condition = ${if eq {$len_3:$dkim_algo}{rsa}}
+ condition = ${if or {eq {$dkim_algo}{rsa-sha1}} \
+ {< {$dkim_key_length}{1024}} }
logwrite = NOTE: forcing dkim verify fail (was pass)
set dkim_verify_status = fail
- set dkim_verify_reason = hash too weak
+ set dkim_verify_reason = hash too weak or key too short
.endd
After all the DKIM ACL runs have completed, the value becomes a
signature to be treated as "expired". When this was not specified by the
signer, "9999999999999" is returned. This makes it possible to do useful
integer size comparisons against this value.
+.new
+Note that Exim does not check this value.
+.wen
.vitem &%$dkim_headernames%&
A colon-separated list of names of headers included in the signature.
To enforce this you must have a DKIM ACL which checks this variable
and overwrites the &$dkim_verify_status$& variable as discussed above.
+As EC keys are much smaller, the check should only do this for RSA keys.
.wen
.endlist
The current list of events is:
.display
+&`dane:fail after transport `& per connection
&`msg:complete after main `& per message
&`msg:delivery after transport `& per recipient
&`msg:rcpt:host:defer after transport `& per recipient per host
An additional variable, &$event_data$&, is filled with information varying
with the event type:
.display
+&`dane:fail `& failure reason
&`msg:delivery `& smtp confirmation message
&`msg:rcpt:host:defer `& error string
&`msg:rcpt:defer `& error string
return an empty string. Should it return anything else the
following will be forced:
.display
-&`msg:delivery `& (ignored)
-&`msg:host:defer `& (ignored)
-&`msg:fail:delivery`& (ignored)
&`tcp:connect `& do not connect
-&`tcp:close `& (ignored)
&`tls:cert `& refuse verification
&`smtp:connect `& close connection
.endd
-No other use is made of the result string.
+All other message types ignore the result string, and
+no other use is made of it.
For a tcp:connect event, if the connection is being made to a proxy
then the address and port variables will be that of the proxy and not
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