Docs: update info on MTA-STS. Bug 3091

[exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index e51e540d9bd73da346e2b68ff275911bc51f62e6..182e5644ccfae4daae13984909cfe00ec05d7279 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -2886,6 +2886,11 @@ available to admin users.
 
 The word &"set"& at the start of a line, followed by a single space,
 is recognised specially as defining a value for a variable.
+.new
+.cindex "tainted data" "expansion testing"
+If the sequence &",t"& is inserted before the space,
+the value is marked as tainted.
+.wen
 The syntax is otherwise the same as the ACL modifier &"set ="&.
 
 .cmdopt -bem <&'filename'&>
@@ -6896,8 +6901,8 @@ key is found. The first key that matches is used; there is no attempt to find a
 lookup types support only literal keys.
 
 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
-the implicit key is the host's IP address rather than its name (see section
-&<<SECThoslispatsikey>>&).
+the implicit key is the host's IP address rather than its name
+(see section &<<SECThoslispatsikey>>&).
 
 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
@@ -9230,8 +9235,9 @@ is not used.
 
 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
 keys in the file, not IP addresses. If you want to do lookups based on IP
-addresses, you must precede the search type with &"net-"& (see section
-&<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
+addresses, you must precede the search type with &"net-"&
+(see section &<<SECThoslispatsikey>>&).
+There is, however, no reason why you could not use
 two items in the same list, one doing an address lookup and one doing a name
 lookup, both using the same file.
 
@@ -12051,7 +12057,8 @@ where the first item in the list is the empty string.
 .next
 The item @[] matches any of the local host's interface addresses.
 .next
-Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
+Single-key lookups are assumed to be like &"net-"& style lookups in host lists
+(see section &<<SECThoslispatsikey>>&),
 even if &`net-`& is not specified. There is never any attempt to turn the IP
 address into a host name. The most common type of linear search for
 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
@@ -30535,12 +30542,17 @@ Section 4.3 of that document.
 .subsection General
 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
 
-DANE is specified in published RFCs and decouples certificate authority trust
+DANE is specified in RFC 6698. It decouples certificate authority trust
 selection from a "race to the bottom" of "you must trust everything for mail
 to get through".
-There is an alternative technology called MTA-STS, which
-instead publishes MX trust anchor information on an HTTPS website.  At the
-time this text was last updated, MTA-STS was still a draft, not yet an RFC.
+It does retain the need to trust the assurances provided by the DNSSEC tree.
+
+There is an alternative technology called MTA-STS (RFC 8461), which
+instead publishes MX trust anchor information on an HTTPS website.
+The discovery of the address for that website does not (per standard)
+require DNSSEC, and could be regarded as being less secure than DANE
+as a result.
+
 Exim has no support for MTA-STS as a client, but Exim mail server operators
 can choose to publish information describing their TLS configuration using
 MTA-STS to let those clients who do use that protocol derive trust
@@ -31066,7 +31078,8 @@ option to do this.)
 .section "Format of an ACL" "SECID199"
 .cindex "&ACL;" "format of"
 .cindex "&ACL;" "verbs, definition of"
-An individual ACL consists of a number of statements. Each statement starts
+An individual ACL definition consists of a number of statements.
+Each statement starts
 with a verb, optionally followed by a number of conditions and &"modifiers"&.
 Modifiers can change the way the verb operates, define error and log messages,
 set variables, insert delays, and vary the processing of accepted messages.
@@ -31085,6 +31098,9 @@ happens then depends on the verb (and in one case, on a special modifier). Not
 all the conditions make sense at every testing point. For example, you cannot
 test a sender address in the ACL that is run for a VRFY command.
 
+The definition of an ACL ends where another starts,
+or a different configuration section starts.
+
 
 .section "ACL verbs" "SECID200"
 The ACL verbs are as follows:
@@ -41600,8 +41616,11 @@ Exim's DKIM implementation allows for
 .olist
 Signing outgoing messages: This function is implemented in the SMTP transport.
 It can co-exist with all other Exim features
-(including transport filters)
-except cutthrough delivery.
+(including transport filters) except cutthrough delivery.
+.new
+However, signing options may not depend on headers modified by
+routers, the transport or a transport filter.
+.wen
 .next
 Verifying signatures in incoming messages: This is implemented by an additional
 ACL (acl_smtp_dkim), which can be called several times per message, with