-Early pipelining support
-------------------------
-Ref: https://datatracker.ietf.org/doc/draft-harris-early-pipe/
-
-If compiled with EXPERIMENTAL_PIPE_CONNECT support is included for this feature.
-The server advertises the feature in its EHLO response, currently using the name
-"X_PIPE_CONNECT" (this will change, some time in the future).
-A client may cache this information, along with the rest of the EHLO response,
-and use it for later connections. Those later ones can send esmtp commands before
-a banner is received.
-
-Up to 1.5 roundtrip times can be taken out of cleartext connections, 2.5 on
-STARTTLS connections.
-
-In combination with the traditional PIPELINING feature the following example
-sequences are possible (among others):
-
-(client) (server)
-
-EHLO,MAIL,RCPT,DATA ->
- <- banner,EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-message-data ->
-------
-
-EHLO,MAIL,RCPT,BDAT ->
- <- banner,EHLO-resp,MAIL-ack,RCPT-ack
-message-data ->
-------
-
-EHLO,STARTTLS ->
- <- banner,EHLO-resp,TLS-goahead
-TLS1.2-client-hello ->
- <- TLS-server-hello,cert,hello-done
-client-Kex,change-cipher,finished ->
- <- change-cipher,finished
-EHLO,MAIL,RCPT,DATA ->
- <- EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-
-------
-(tls-on-connect)
-TLS1.2-client-hello ->
- <- TLS-server-hello,cert,hello-done
-client-Kex,change-cipher,finished ->
- <- change-cipher,finshed
- <- banner
-EHLO,MAIL,RCPT,DATA ->
- <- EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-
-Where the initial client packet is SMTP, it can combine with the TCP Fast Open
-feature and be sent in the TCP SYN.
-
-
-A main-section option "pipelining_connect_advertise_hosts" (default: *)
-and an smtp transport option "hosts_pipe_connect" (default: unset)
-control the feature.
-
-If the "pipelining" log_selector is enabled, the "L" field in server <=
-log lines has a period appended if the feature was advertised but not used;
-or has an asterisk appended if the feature was used. In client => lines
-the "L" field has an asterisk appended if the feature was used.
-
-The "retry_data_expire" option controls cache invalidation.
-Entries are also rewritten (or cleared) if the adverised features
-change.
-
-
-NOTE: since the EHLO command must be constructed before the connection is
-made it cannot depend on the interface IP address that will be used.
-Transport configurations should be checked for this. An example avoidance:
-
- helo_data = ${if def:sending_ip_address \
- {${lookup dnsdb{>! ptr=$sending_ip_address} \
- {${sg{$value} {^([^!]*).*\$} {\$1}}} fail}} \
- {$primary_hostname}}
-
-
-
-
TLS Session Resumption
----------------------
TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
vulnarability surface. An attacker able to decrypt it would have access
all connections using the resumed session.
The session ticket encryption key is not committed to storage by the server
- and is rotated regularly. Tickets have limited lifetime.
+ and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
+ overlap; GnuTLS 6hr but does not specify any overlap).
+ Tickets have limited lifetime (2hr, and new ones issued after 1hr under
+ OpenSSL. GnuTLS 2hr, appears to not do overlap).
There is a question-mark over the security of the Diffie-Helman parameters
used for session negotiation. TBD. q-value; cf bug 1895
Issues:
In a resumed session:
- $tls_{in,out}_certificate_verified will be set, and verify = certificate
- will be true, when verify failed but tls_try_verify_hosts allowed the
- connection (under OpenSSL)
$tls_{in,out}_cipher will have values different to the original (under GnuTLS)
$tls_{in,out}_ocsp will be "not requested" or "no response", and
- hosts_require_ocsp will fail
+ hosts_require_ocsp will fail
--------------------------------------------------------------
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