-$Cambridge: exim/doc/doc-txt/NewStuff,v 1.26 2005/02/17 12:24:00 ph10 Exp $
+$Cambridge: exim/doc/doc-txt/NewStuff,v 1.40 2005/05/10 10:19:11 ph10 Exp $
New Features in Exim
--------------------
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
+------------
+
+PH/01 The format in which GnuTLS parameters are written to the gnutls-param
+ file in the spool directory has been changed. This change has been made
+ to alleviate problems that some people had with the generation of the
+ parameters by Exim when /dev/random was exhausted. In this situation,
+ Exim would hang until /dev/random acquired some more entropy.
+
+ The new code exports and imports the DH and RSA parameters in PEM
+ format. This means that the parameters can be generated externally using
+ the certtool command that is part of GnuTLS.
+
+ To replace the parameters with new ones, instead of deleting the file
+ and letting Exim re-create it, you can generate new parameters using
+ certtool and, when this has been done, replace Exim's cache file by
+ renaming. The relevant commands are something like this:
+
+ # rm -f new.params
+ # touch new.params
+ # chown exim:exim new.params
+ # chmod 0400 new.params
+ # certtool --generate-privkey --bits 512 >new.params
+ # echo "" >>new.params
+ # certtool --generate-dh-params --bits 1024 >> new.params
+ # mv new.params params
+
+ If Exim never has to generate the parameters itself, the possibility of
+ stalling is removed.
+
+PH/02 A new expansion item for dynamically loading and calling a locally-
+ written C function is now provided, if Exim is compiled with
+
+ EXPAND_DLFUNC=yes
+
+ set in Local/Makefile. The facility is not included by default (a
+ suitable error is given if you try to use it when it is not there.)
+
+ If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
+ router option forbid_filter_dlfunc. If you have unprivileged users on
+ your system who are permitted to create filter files, you might want to
+ set forbid_filter_dlfunc=true in the appropriate router, to stop them
+ using ${dlfunc to run code within Exim.
+
+ You load and call an external function like this:
+
+ ${dlfunc{/some/file}{function}{arg1}{arg2}...}
+
+ Once loaded, Exim remembers the dynamically loaded object so that it
+ doesn't reload the same object file in the same Exim process (but of
+ course Exim does start new processes frequently).
+
+ There may be from zero to eight arguments to the function. When compiling
+ a local function that is to be called in this way, local_scan.h should be
+ included. The Exim variables and functions that are defined by that API
+ are also available for dynamically loaded functions. The function itself
+ must have the following type:
+
+ int dlfunction(uschar **yield, int argc, uschar *argv[])
+
+ Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
+ function should return one of the following values:
+
+ OK Success. The string that is placed in "yield" is put into
+ the expanded string that is being built.
+
+ FAIL A non-forced expansion failure occurs, with the error
+ message taken from "yield", if it is set.
+
+ FAIL_FORCED A forced expansion failure occurs, with the error message
+ taken from "yield" if it is set.
+
+ ERROR Same as FAIL, except that a panic log entry is written.
+
+ When compiling a function that is to be used in this way with gcc,
+ you need to add -shared to the gcc command. Also, in the Exim build-time
+ configuration, you must add -export-dynamic to EXTRALIBS.
+
+TF/01 $received_time is a new expansion variable containing the time and date
+ as a number of seconds since the start of the Unix epoch when the
+ current message was received.
+
+PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
+ Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
+ in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
+ possible to detect the different versions automatically.
+
+PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
+ MIME parts in non-SMTP messages. It operates in exactly the same way as
+ acl_smtp_mime
+
+PH/05 It is now possible to redefine a macro within the configuration file.
+ The macro must have been previously defined within the configuration (or
+ an included file). A definition on the command line using the -D option
+ causes all definitions and redefinitions within the file to be ignored.
+ In other words, -D overrides any values that are set in the file.
+ Redefinition is specified by using '==' instead of '='. For example:
+
+ MAC1 = initial value
+ ...
+ MAC1 == updated value
+
+ Redefinition does not alter the order in which the macros are applied to
+ the subsequent lines of the configuration file. It is still the same
+ order in which the macros were originally defined. All that changes is
+ the macro's value. Redefinition makes it possible to accumulate values.
+ For example:
+
+ MAC1 = initial value
+ ...
+ MAC1 == MAC1 and something added
+
+ This can be helpful in situations where the configuration file is built
+ from a number of other files.
+
+PH/06 Macros may now be defined or redefined between router, transport,
+ authenticator, or ACL definitions, as well as in the main part of the
+ configuration. They may not, however, be changed within an individual
+ driver or ACL, or in the local_scan, retry, or rewrite sections of the
+ configuration.
+
+PH/07 $acl_verify_message is now set immediately after the failure of a
+ verification in an ACL, and so is available in subsequent modifiers. In
+ particular, the message can be preserved by coding like this:
+
+ warn !verify = sender
+ set acl_m0 = $acl_verify_message
+
+ Previously, $acl_verify_message was set only while expanding "message"
+ and "log_message" when a very denied access.
+
+PH/08 The redirect router has two new options, sieve_useraddress and
+ sieve_subaddress. These are passed to a Sieve filter to specify the :user
+ and :subaddress parts of an address. Both options are unset by default.
+ However, when a Sieve filter is run, if sieve_useraddress is unset, the
+ entire original local part (including any prefix or suffix) is used for
+ :user. An unset subaddress is treated as an empty subaddress.
+
+PH/09 Quota values can be followed by G as well as K and M.
+
+PH/10 $message_linecount is a new variable that contains the total number of
+ lines in the header and body of the message. Compare $body_linecount,
+ which is the count for the body only. During the DATA and
+ content-scanning ACLs, $message_linecount contains the number of lines
+ received. Before delivery happens (that is, before filters, routers, and
+ transports run) the count is increased to include the Received: header
+ line that Exim standardly adds, and also any other header lines that are
+ added by ACLs. The blank line that separates the message header from the
+ body is not counted. Here is an example of the use of this variable in a
+ DATA ACL:
+
+ deny message = Too many lines in message header
+ condition = \
+ ${if <{250}{${eval: $message_linecount - $body_linecount}}}
+
+ In the MAIL and RCPT ACLs, the value is zero because at that stage the
+ message has not yet been received.
+
+PH/11 In a ${run expansion, the variable $value (which contains the standard
+ output) is now also usable in the "else" string.
+
+PH/12 In a pipe transport, although a timeout while waiting for the pipe
+ process to complete was treated as a delivery failure, a timeout while
+ writing the message to the pipe was logged, but erroneously treated as a
+ successful delivery. Such timeouts include transport filter timeouts. For
+ consistency with the overall process timeout, these timeouts are now
+ treated as errors, giving rise to delivery failures by default. However,
+ there is now a new Boolean option for the pipe transport called
+ timeout_defer, which, if set TRUE, converts the failures into defers for
+ both kinds of timeout. A transport filter timeout is now identified in
+ the log output.
+
+
Version 4.50
------------
git://git.exim.org / users / heiko / exim.git / blobdiff