diff options
Diffstat (limited to 'doc/doc-txt/NewStuff')
| -rw-r--r-- | doc/doc-txt/NewStuff | 62 |
1 files changed, 61 insertions, 1 deletions
diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff index f0abee45a..98c6fe258 100644 --- a/doc/doc-txt/NewStuff +++ b/doc/doc-txt/NewStuff @@ -1,4 +1,4 @@ -$Cambridge: exim/doc/doc-txt/NewStuff,v 1.39 2005/05/03 14:20:00 ph10 Exp $ +$Cambridge: exim/doc/doc-txt/NewStuff,v 1.40 2005/05/10 10:19:11 ph10 Exp $ New Features in Exim -------------------- @@ -9,6 +9,66 @@ updated when there is a relatively large batch of changes). The doc/ChangeLog file contains a listing of all changes, including bug fixes. +Exim version 4.52 +----------------- + +TF/01 Support for checking Client SMTP Authorization has been added. CSA is a + system which allows a site to advertise which machines are and are not + permitted to send email. This is done by placing special SRV records in + the DNS, which are looked up using the client's HELO domain. At this + time CSA is still an Internet-Draft. + + Client SMTP Authorization checks are performed by the ACL condition + verify=csa. This will fail if the client is not authorized. If there is + a DNS problem, or if no valid CSA SRV record is found, or if the client + is authorized, the condition succeeds. These three cases can be + distinguished using the expansion variable $csa_status, which can take + one of the values "fail", "defer", "unknown", or "ok". The condition + does not itself defer because that would be likely to cause problems + for legitimate email. + + The error messages produced by the CSA code include slightly more + detail. If $csa_status is "defer" this may be because of problems + looking up the CSA SRV record, or problems looking up the CSA target + address record. There are four reasons for $csa_status being "fail": + the client's host name is explicitly not authorized; the client's IP + address does not match any of the CSA target IP addresses; the client's + host name is authorized but it has no valid target IP addresses (e.g. + the target's addresses are IPv6 and the client is using IPv4); or the + client's host name has no CSA SRV record but a parent domain has + asserted that all subdomains must be explicitly authorized. + + The verify=csa condition can take an argument which is the domain to + use for the DNS query. The default is verify=csa/$sender_helo_name. + + This implementation includes an extension to CSA. If the query domain + is an address literal such as [192.0.2.95], or if it is a bare IP + address, Exim will search for CSA SRV records in the reverse DNS as if + the HELO domain was e.g. 95.2.0.192.in-addr.arpa. Therefore it is + meaningful to say, for example, verify=csa/$sender_host_address - in + fact, this is the check that Exim performs if the client does not say + HELO. This extension can be turned off by setting the main + configuration option dns_csa_use_reverse = false. + + If a CSA SRV record is not found for the domain itself, then a search + is performed through its parent domains for a record which might be + making assertions about subdomains. The maximum depth of this search is + limited using the main configuration option dns_csa_search_limit, which + takes the value 5 by default. Exim does not look for CSA SRV records in + a top level domain, so the default settings handle HELO domains as long + as seven (hostname.five.four.three.two.one.com) which encompasses the + vast majority of legitimate HELO domains. + + The dnsdb lookup also has support for CSA. Although dnsdb already + supports SRV lookups, this is not sufficient because of the extra + parent domain search behaviour of CSA, and (as with PTR lookups) + dnsdb also turns IP addresses into lookups in the reverse DNS space. + The result of ${lookup dnsdb {csa=$sender_helo_name} } has two + space-separated fields: an authorization code and a target host name. + The authorization code can be "Y" for yes, "N" for no, "X" for explicit + authorization required but absent, or "?" for unknown. + + Version 4.51 ------------ |