1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.40 2005/05/10 10:19:11 ph10 Exp $
6 This file contains descriptions of new features that have been added to Exim,
7 but have not yet made it into the main manual (which is most conveniently
8 updated when there is a relatively large batch of changes). The doc/ChangeLog
9 file contains a listing of all changes, including bug fixes.
15 TF/01 Support for checking Client SMTP Authorization has been added. CSA is a
16 system which allows a site to advertise which machines are and are not
17 permitted to send email. This is done by placing special SRV records in
18 the DNS, which are looked up using the client's HELO domain. At this
19 time CSA is still an Internet-Draft.
21 Client SMTP Authorization checks are performed by the ACL condition
22 verify=csa. This will fail if the client is not authorized. If there is
23 a DNS problem, or if no valid CSA SRV record is found, or if the client
24 is authorized, the condition succeeds. These three cases can be
25 distinguished using the expansion variable $csa_status, which can take
26 one of the values "fail", "defer", "unknown", or "ok". The condition
27 does not itself defer because that would be likely to cause problems
30 The error messages produced by the CSA code include slightly more
31 detail. If $csa_status is "defer" this may be because of problems
32 looking up the CSA SRV record, or problems looking up the CSA target
33 address record. There are four reasons for $csa_status being "fail":
34 the client's host name is explicitly not authorized; the client's IP
35 address does not match any of the CSA target IP addresses; the client's
36 host name is authorized but it has no valid target IP addresses (e.g.
37 the target's addresses are IPv6 and the client is using IPv4); or the
38 client's host name has no CSA SRV record but a parent domain has
39 asserted that all subdomains must be explicitly authorized.
41 The verify=csa condition can take an argument which is the domain to
42 use for the DNS query. The default is verify=csa/$sender_helo_name.
44 This implementation includes an extension to CSA. If the query domain
45 is an address literal such as [192.0.2.95], or if it is a bare IP
46 address, Exim will search for CSA SRV records in the reverse DNS as if
47 the HELO domain was e.g. 95.2.0.192.in-addr.arpa. Therefore it is
48 meaningful to say, for example, verify=csa/$sender_host_address - in
49 fact, this is the check that Exim performs if the client does not say
50 HELO. This extension can be turned off by setting the main
51 configuration option dns_csa_use_reverse = false.
53 If a CSA SRV record is not found for the domain itself, then a search
54 is performed through its parent domains for a record which might be
55 making assertions about subdomains. The maximum depth of this search is
56 limited using the main configuration option dns_csa_search_limit, which
57 takes the value 5 by default. Exim does not look for CSA SRV records in
58 a top level domain, so the default settings handle HELO domains as long
59 as seven (hostname.five.four.three.two.one.com) which encompasses the
60 vast majority of legitimate HELO domains.
62 The dnsdb lookup also has support for CSA. Although dnsdb already
63 supports SRV lookups, this is not sufficient because of the extra
64 parent domain search behaviour of CSA, and (as with PTR lookups)
65 dnsdb also turns IP addresses into lookups in the reverse DNS space.
66 The result of ${lookup dnsdb {csa=$sender_helo_name} } has two
67 space-separated fields: an authorization code and a target host name.
68 The authorization code can be "Y" for yes, "N" for no, "X" for explicit
69 authorization required but absent, or "?" for unknown.
75 PH/01 The format in which GnuTLS parameters are written to the gnutls-param
76 file in the spool directory has been changed. This change has been made
77 to alleviate problems that some people had with the generation of the
78 parameters by Exim when /dev/random was exhausted. In this situation,
79 Exim would hang until /dev/random acquired some more entropy.
81 The new code exports and imports the DH and RSA parameters in PEM
82 format. This means that the parameters can be generated externally using
83 the certtool command that is part of GnuTLS.
85 To replace the parameters with new ones, instead of deleting the file
86 and letting Exim re-create it, you can generate new parameters using
87 certtool and, when this has been done, replace Exim's cache file by
88 renaming. The relevant commands are something like this:
92 # chown exim:exim new.params
93 # chmod 0400 new.params
94 # certtool --generate-privkey --bits 512 >new.params
95 # echo "" >>new.params
96 # certtool --generate-dh-params --bits 1024 >> new.params
97 # mv new.params params
99 If Exim never has to generate the parameters itself, the possibility of
102 PH/02 A new expansion item for dynamically loading and calling a locally-
103 written C function is now provided, if Exim is compiled with
107 set in Local/Makefile. The facility is not included by default (a
108 suitable error is given if you try to use it when it is not there.)
110 If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
111 router option forbid_filter_dlfunc. If you have unprivileged users on
112 your system who are permitted to create filter files, you might want to
113 set forbid_filter_dlfunc=true in the appropriate router, to stop them
114 using ${dlfunc to run code within Exim.
116 You load and call an external function like this:
118 ${dlfunc{/some/file}{function}{arg1}{arg2}...}
120 Once loaded, Exim remembers the dynamically loaded object so that it
121 doesn't reload the same object file in the same Exim process (but of
122 course Exim does start new processes frequently).
124 There may be from zero to eight arguments to the function. When compiling
125 a local function that is to be called in this way, local_scan.h should be
126 included. The Exim variables and functions that are defined by that API
127 are also available for dynamically loaded functions. The function itself
128 must have the following type:
130 int dlfunction(uschar **yield, int argc, uschar *argv[])
132 Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
133 function should return one of the following values:
135 OK Success. The string that is placed in "yield" is put into
136 the expanded string that is being built.
138 FAIL A non-forced expansion failure occurs, with the error
139 message taken from "yield", if it is set.
141 FAIL_FORCED A forced expansion failure occurs, with the error message
142 taken from "yield" if it is set.
144 ERROR Same as FAIL, except that a panic log entry is written.
146 When compiling a function that is to be used in this way with gcc,
147 you need to add -shared to the gcc command. Also, in the Exim build-time
148 configuration, you must add -export-dynamic to EXTRALIBS.
150 TF/01 $received_time is a new expansion variable containing the time and date
151 as a number of seconds since the start of the Unix epoch when the
152 current message was received.
154 PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
155 Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
156 in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
157 possible to detect the different versions automatically.
159 PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
160 MIME parts in non-SMTP messages. It operates in exactly the same way as
163 PH/05 It is now possible to redefine a macro within the configuration file.
164 The macro must have been previously defined within the configuration (or
165 an included file). A definition on the command line using the -D option
166 causes all definitions and redefinitions within the file to be ignored.
167 In other words, -D overrides any values that are set in the file.
168 Redefinition is specified by using '==' instead of '='. For example:
172 MAC1 == updated value
174 Redefinition does not alter the order in which the macros are applied to
175 the subsequent lines of the configuration file. It is still the same
176 order in which the macros were originally defined. All that changes is
177 the macro's value. Redefinition makes it possible to accumulate values.
182 MAC1 == MAC1 and something added
184 This can be helpful in situations where the configuration file is built
185 from a number of other files.
187 PH/06 Macros may now be defined or redefined between router, transport,
188 authenticator, or ACL definitions, as well as in the main part of the
189 configuration. They may not, however, be changed within an individual
190 driver or ACL, or in the local_scan, retry, or rewrite sections of the
193 PH/07 $acl_verify_message is now set immediately after the failure of a
194 verification in an ACL, and so is available in subsequent modifiers. In
195 particular, the message can be preserved by coding like this:
197 warn !verify = sender
198 set acl_m0 = $acl_verify_message
200 Previously, $acl_verify_message was set only while expanding "message"
201 and "log_message" when a very denied access.
203 PH/08 The redirect router has two new options, sieve_useraddress and
204 sieve_subaddress. These are passed to a Sieve filter to specify the :user
205 and :subaddress parts of an address. Both options are unset by default.
206 However, when a Sieve filter is run, if sieve_useraddress is unset, the
207 entire original local part (including any prefix or suffix) is used for
208 :user. An unset subaddress is treated as an empty subaddress.
210 PH/09 Quota values can be followed by G as well as K and M.
212 PH/10 $message_linecount is a new variable that contains the total number of
213 lines in the header and body of the message. Compare $body_linecount,
214 which is the count for the body only. During the DATA and
215 content-scanning ACLs, $message_linecount contains the number of lines
216 received. Before delivery happens (that is, before filters, routers, and
217 transports run) the count is increased to include the Received: header
218 line that Exim standardly adds, and also any other header lines that are
219 added by ACLs. The blank line that separates the message header from the
220 body is not counted. Here is an example of the use of this variable in a
223 deny message = Too many lines in message header
225 ${if <{250}{${eval: $message_linecount - $body_linecount}}}
227 In the MAIL and RCPT ACLs, the value is zero because at that stage the
228 message has not yet been received.
230 PH/11 In a ${run expansion, the variable $value (which contains the standard
231 output) is now also usable in the "else" string.
233 PH/12 In a pipe transport, although a timeout while waiting for the pipe
234 process to complete was treated as a delivery failure, a timeout while
235 writing the message to the pipe was logged, but erroneously treated as a
236 successful delivery. Such timeouts include transport filter timeouts. For
237 consistency with the overall process timeout, these timeouts are now
238 treated as errors, giving rise to delivery failures by default. However,
239 there is now a new Boolean option for the pipe transport called
240 timeout_defer, which, if set TRUE, converts the failures into defers for
241 both kinds of timeout. A transport filter timeout is now identified in
248 The documentation is up-to-date for the 4.50 release.
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