Expand the documentation about the new submission mode behaviour.
[exim.git] / doc / doc-txt / NewStuff
4df1e33e 1$Cambridge: exim/doc/doc-txt/NewStuff,v 1.44 2005/05/23 15:44:06 fanf2 Exp $
3New Features in Exim
6This file contains descriptions of new features that have been added to Exim,
7but have not yet made it into the main manual (which is most conveniently
8updated when there is a relatively large batch of changes). The doc/ChangeLog
9file contains a listing of all changes, including bug fixes.
12Exim version 4.52
15TF/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
28 for legitimate email.
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 [], 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. 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.
71PH/01 The amount of output produced by the "make" process has been reduced,
72 because the compile lines are often rather long, making it all pretty
73 unreadable. The new style is along the lines of the 2.6 Linux kernel:
74 just a short line for each module that is being compiled or linked.
75 However, it is still possible to get the full output, by calling "make"
76 like this:
78 FULLECHO='' make -e
80 The value of FULLECHO defaults to "@", the flag character that suppresses
81 command reflection in "make". When you ask for the full output, it is
82 given in addition to the the short output.
4df1e33e 84TF/02 There have been two changes concerned with submission mode:
87ba3f5f 85
86 Until now submission mode always left the return path alone, whereas
87 locally-submitted messages from untrusted users have the return path
88 fixed to the user's email address. Submission mode now fixes the return
89 path to the same address as is used to create the Sender: header. If
90 /sender_retain is specified then both the Sender: header and the return
91 path are left alone.
87ba3f5f 92
93 Note that the changes caused by submission mode take effect after the
94 predata ACL. This means that any sender checks performed before the
95 fix-ups will use the untrusted sender address specified by the user, not
96 the trusted sender address specified by submission mode. Although this
97 might be slightly unexpected, it does mean that you can configure ACL
98 checks to spot that a user is trying to spoof another's address, for
99 example.
87ba3f5f 100
101 There is also a new /name= option for submission mode which allows you
102 to specify the user's full name to be included in the Sender: header.
103 For example:
105 accept authenticated = *
106 control = submission/name=${lookup {$authenticated_id} \
107 lsearch {/etc/exim/namelist} }
109 The namelist file contains entries like
111 fanf: Tony Finch
113 And the resulting Sender: header looks like
115 Sender: Tony Finch <fanf@exim.org>
117TF/03 The control = fakereject ACL modifier now has a fakedefer counterpart,
118 which works in exactly the same way except it causes a fake SMTP 450
119 response after the message data instead of a fake SMTP 550 response.
120 You must take care when using fakedefer because it will cause messages
121 to be duplicated when the sender retries. Therefore you should not use
122 fakedefer if the message will be delivered normally.
e5a9dba6 124
125Version 4.51
128PH/01 The format in which GnuTLS parameters are written to the gnutls-param
129 file in the spool directory has been changed. This change has been made
130 to alleviate problems that some people had with the generation of the
131 parameters by Exim when /dev/random was exhausted. In this situation,
132 Exim would hang until /dev/random acquired some more entropy.
134 The new code exports and imports the DH and RSA parameters in PEM
135 format. This means that the parameters can be generated externally using
136 the certtool command that is part of GnuTLS.
138 To replace the parameters with new ones, instead of deleting the file
139 and letting Exim re-create it, you can generate new parameters using
140 certtool and, when this has been done, replace Exim's cache file by
141 renaming. The relevant commands are something like this:
143 # rm -f new.params
144 # touch new.params
145 # chown exim:exim new.params
146 # chmod 0400 new.params
147 # certtool --generate-privkey --bits 512 >new.params
148 # echo "" >>new.params
149 # certtool --generate-dh-params --bits 1024 >> new.params
150 # mv new.params params
152 If Exim never has to generate the parameters itself, the possibility of
153 stalling is removed.
155PH/02 A new expansion item for dynamically loading and calling a locally-
156 written C function is now provided, if Exim is compiled with
160 set in Local/Makefile. The facility is not included by default (a
161 suitable error is given if you try to use it when it is not there.)
163 If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
164 router option forbid_filter_dlfunc. If you have unprivileged users on
165 your system who are permitted to create filter files, you might want to
166 set forbid_filter_dlfunc=true in the appropriate router, to stop them
167 using ${dlfunc to run code within Exim.
169 You load and call an external function like this:
171 ${dlfunc{/some/file}{function}{arg1}{arg2}...}
173 Once loaded, Exim remembers the dynamically loaded object so that it
174 doesn't reload the same object file in the same Exim process (but of
175 course Exim does start new processes frequently).
177 There may be from zero to eight arguments to the function. When compiling
178 a local function that is to be called in this way, local_scan.h should be
179 included. The Exim variables and functions that are defined by that API
180 are also available for dynamically loaded functions. The function itself
181 must have the following type:
183 int dlfunction(uschar **yield, int argc, uschar *argv[])
185 Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
186 function should return one of the following values:
188 OK Success. The string that is placed in "yield" is put into
189 the expanded string that is being built.
191 FAIL A non-forced expansion failure occurs, with the error
192 message taken from "yield", if it is set.
194 FAIL_FORCED A forced expansion failure occurs, with the error message
195 taken from "yield" if it is set.
197 ERROR Same as FAIL, except that a panic log entry is written.
199 When compiling a function that is to be used in this way with gcc,
200 you need to add -shared to the gcc command. Also, in the Exim build-time
201 configuration, you must add -export-dynamic to EXTRALIBS.
b5aea5e1 202
203TF/01 $received_time is a new expansion variable containing the time and date
204 as a number of seconds since the start of the Unix epoch when the
205 current message was received.
b5aea5e1 206
207PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
208 Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
209 in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
210 possible to detect the different versions automatically.
212PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
213 MIME parts in non-SMTP messages. It operates in exactly the same way as
214 acl_smtp_mime
216PH/05 It is now possible to redefine a macro within the configuration file.
217 The macro must have been previously defined within the configuration (or
218 an included file). A definition on the command line using the -D option
219 causes all definitions and redefinitions within the file to be ignored.
220 In other words, -D overrides any values that are set in the file.
221 Redefinition is specified by using '==' instead of '='. For example:
223 MAC1 = initial value
224 ...
225 MAC1 == updated value
227 Redefinition does not alter the order in which the macros are applied to
228 the subsequent lines of the configuration file. It is still the same
229 order in which the macros were originally defined. All that changes is
230 the macro's value. Redefinition makes it possible to accumulate values.
231 For example:
233 MAC1 = initial value
234 ...
235 MAC1 == MAC1 and something added
237 This can be helpful in situations where the configuration file is built
238 from a number of other files.
240PH/06 Macros may now be defined or redefined between router, transport,
241 authenticator, or ACL definitions, as well as in the main part of the
242 configuration. They may not, however, be changed within an individual
243 driver or ACL, or in the local_scan, retry, or rewrite sections of the
244 configuration.
246PH/07 $acl_verify_message is now set immediately after the failure of a
247 verification in an ACL, and so is available in subsequent modifiers. In
248 particular, the message can be preserved by coding like this:
250 warn !verify = sender
251 set acl_m0 = $acl_verify_message
253 Previously, $acl_verify_message was set only while expanding "message"
254 and "log_message" when a very denied access.
256PH/08 The redirect router has two new options, sieve_useraddress and
257 sieve_subaddress. These are passed to a Sieve filter to specify the :user
258 and :subaddress parts of an address. Both options are unset by default.
259 However, when a Sieve filter is run, if sieve_useraddress is unset, the
260 entire original local part (including any prefix or suffix) is used for
261 :user. An unset subaddress is treated as an empty subaddress.
475fe28a 262
263PH/09 Quota values can be followed by G as well as K and M.
265PH/10 $message_linecount is a new variable that contains the total number of
266 lines in the header and body of the message. Compare $body_linecount,
267 which is the count for the body only. During the DATA and
268 content-scanning ACLs, $message_linecount contains the number of lines
269 received. Before delivery happens (that is, before filters, routers, and
270 transports run) the count is increased to include the Received: header
271 line that Exim standardly adds, and also any other header lines that are
272 added by ACLs. The blank line that separates the message header from the
273 body is not counted. Here is an example of the use of this variable in a
276 deny message = Too many lines in message header
277 condition = \
278 ${if <{250}{${eval: $message_linecount - $body_linecount}}}
280 In the MAIL and RCPT ACLs, the value is zero because at that stage the
281 message has not yet been received.
283PH/11 In a ${run expansion, the variable $value (which contains the standard
284 output) is now also usable in the "else" string.
286PH/12 In a pipe transport, although a timeout while waiting for the pipe
287 process to complete was treated as a delivery failure, a timeout while
288 writing the message to the pipe was logged, but erroneously treated as a
289 successful delivery. Such timeouts include transport filter timeouts. For
290 consistency with the overall process timeout, these timeouts are now
291 treated as errors, giving rise to delivery failures by default. However,
292 there is now a new Boolean option for the pipe transport called
293 timeout_defer, which, if set TRUE, converts the failures into defers for
294 both kinds of timeout. A transport filter timeout is now identified in
295 the log output.
7766a4f0 297
f7b63901 298Version 4.50
b9e40c51 301The documentation is up-to-date for the 4.50 release.