Doc: s/DNS/domains/ in new text

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 3e73de6c3c22c59bb7f1d155fe1e0a2d31733b79..2f06f126fc0d1a74f972bd21a2c89dd97b35876d 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -15710,7 +15710,7 @@ ignored. See section &<<SECTopenvsgnu>>& for further details.
 .new
 If the DH bit-count from loading the file is greater than tls_dh_max_bits then
 it will be ignored.
 .new
 If the DH bit-count from loading the file is greater than tls_dh_max_bits then
 it will be ignored.

-.end
+.wen

 
 
 .option tls_on_connect_ports main "string list" unset
 
 
 .option tls_on_connect_ports main "string list" unset


@@ -17103,6 +17103,40 @@ look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
 case routing fails.
 
 
 case routing fails.
 
 

+.new
+.section "Declining addresses by dnslookup" "SECTdnslookupdecline"
+.cindex "&(dnslookup)& router" "declines"
+There are a few cases where a &(dnslookup)& router will decline to accept
+an address; if such a router is expected to handle "all remaining non-local
+domains", then it is important to set &%no_more%&.
+
+Reasons for a &(dnslookup)& router to decline currently include:
+.ilist
+The domain does not exist in DNS
+.next
+The domain exists but the MX record's host part is just "."; this is a common
+convention (borrowed from SRV) used to indicate that there is no such service
+for this domain and to not fall back to trying A/AAAA records.
+.next
+Ditto, but for SRV records, when &%check_srv%& is set on this router.
+.next
+MX record points to a non-existent host.
+.next
+MX record points to an IP address and the main section option
+&%allow_mx_to_ip%& is not set.
+.next
+MX records exist and point to valid hosts, but all hosts resolve only to
+addresses blocked by the &%ignore_target_hosts%& generic option on this router.
+.next
+The domain is not syntactically valid (see also &%allow_utf8_domains%& and
+&%dns_check_names_pattern%& for handling one variant of this)
+.next
+&%check_secondary_mx%& is set on this router but the local host can
+not be found in the MX records (see below)
+.endlist
+.wen
+
+

 
 
 .section "Private options for dnslookup" "SECID118"
 
 
 .section "Private options for dnslookup" "SECID118"


@@ -25068,7 +25102,10 @@ There is a function in the OpenSSL library that can be passed a list of cipher
 suites before the cipher negotiation takes place. This specifies which ciphers
 are acceptable. The list is colon separated and may contain names like
 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
 suites before the cipher negotiation takes place. This specifies which ciphers
 are acceptable. The list is colon separated and may contain names like
 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&

-directly to this function call. The following quotation from the OpenSSL
+directly to this function call.
+Many systems will install the OpenSSL manual-pages, so you may have
+&'ciphers(1)'& available to you.
+The following quotation from the OpenSSL

 documentation specifies what forms of item are allowed in the cipher string:
 
 .ilist
 documentation specifies what forms of item are allowed in the cipher string:
 
 .ilist


@@ -25105,6 +25142,26 @@ includes any ciphers already present they will be ignored: that is, they will
 not be moved to the end of the list.
 .endlist
 
 not be moved to the end of the list.
 .endlist
 

+.new
+The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
+string:
+.code
+# note single-quotes to get ! past any shell history expansion
+$ openssl ciphers 'HIGH:!MD5:!SHA1'
+.endd
+
+This example will let the library defaults be permitted on the MX port, where
+there's probably no identity verification anyway, but ups the ante on the
+submission ports where the administrator might have some influence on the
+choice of clients used:
+.code
+# OpenSSL variant; see man ciphers(1)
+tls_require_ciphers = ${if =={$received_port}{25}\
+                           {DEFAULT}\
+                           {HIGH:!MD5:!SHA1}}
+.endd
+.wen
+

 
 
 .new
 
 
 .new


@@ -25132,11 +25189,27 @@ aware of future feature enhancements of GnuTLS.
 
 Documentation of the strings accepted may be found in the GnuTLS manual, under
 "Priority strings".  This is online as
 
 Documentation of the strings accepted may be found in the GnuTLS manual, under
 "Priority strings".  This is online as

-&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html).
+&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html),
+but beware that this relates to GnuTLS 3, which may be newer than the version
+installed on your system.  If you are using GnuTLS 3,
+&url(http://www.gnu.org/software/gnutls/manual/html_node/Listing-the-ciphersuites-in-a-priority-string.html, then the example code)
+on that site can be used to test a given string.

 
 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
 "&%gnutls_require_protocols%&".  &%tls_require_ciphers%& was an Exim list.
 
 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
 "&%gnutls_require_protocols%&".  &%tls_require_ciphers%& was an Exim list.

+
+This example will let the library defaults be permitted on the MX port, where
+there's probably no identity verification anyway, and lowers security further
+by increasing compatibility; but this ups the ante on the submission ports
+where the administrator might have some influence on the choice of clients
+used:
+.code
+# GnuTLS variant
+tls_require_ciphers = ${if =={$received_port}{25}\
+                           {NORMAL:%COMPAT}\
+                           {SECURE128}}
+.endd

 .wen
 
 
 .wen