DKIM: ensure that dkim_domain elements are lowercased before use. Bug 2371

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index bb486d678a0e98c638dd397a44ad936ab0c15eb3..415c727127913e4b3e6846794535534397a266ce 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -39534,7 +39534,7 @@ senders).
 .cindex "DKIM" "signing"
 
 For signing to be usable you must have published a DKIM record in DNS.
-Note that RFC 8301 says:
+Note that RFC 8301 (which does not cover EC keys) says:
 .code
 rsa-sha1 MUST NOT be used for signing or verifying.
 
@@ -39554,7 +39554,11 @@ These options take (expandable) strings as arguments.
 .option dkim_domain smtp string list&!! unset
 The domain(s) you want to sign with.
 After expansion, this can be a list.
-Each element in turn is put into the &%$dkim_domain%& expansion variable
+Each element in turn,
+.new
+lowercased,
+.wen
+is put into the &%$dkim_domain%& expansion variable
 while expanding the remaining signing options.
 If it is empty after expansion, DKIM signing is not done,
 and no error will result even if &%dkim_strict%& is set.
@@ -39755,6 +39759,14 @@ dkim_verify_signers = $sender_address_domain:$dkim_signers
 If a domain or identity is listed several times in the (expanded) value of
 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
 
+.new
+Note that if the option is set using untrustworthy data
+(such as the From: header)
+care should be taken to force lowercase for domains
+and for the domain part if identities.
+The default setting can be regarded as trustworthy in this respect.
+.wen
+
 If multiple signatures match a domain (or identity), the ACL is called once
 for each matching signature.
 
@@ -40192,6 +40204,8 @@ of the proxy):
 .endd
 If &$proxy_session$& is set but &$proxy_external_address$& is empty
 there was a protocol error.
+The variables &$sender_host_address$& and &$sender_host_port$&
+will have values for the actual client system, not the proxy.
 
 Since the real connections are all coming from the proxy, and the
 per host connection tracking is done before Proxy Protocol is