doc/doc-txt/NewStuff

   1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.38 2005/04/28 13:29:27 ph10 Exp $
   2
   3 New Features in Exim
   4 --------------------
   5
   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.
  10
  11
  12 Version 4.51
  13 ------------
  14
  15 PH/01 The format in which GnuTLS parameters are written to the gnutls-param
  16       file in the spool directory has been changed. This change has been made
  17       to alleviate problems that some people had with the generation of the
  18       parameters by Exim when /dev/random was exhausted. In this situation,
  19       Exim would hang until /dev/random acquired some more entropy.
  20
  21       The new code exports and imports the DH and RSA parameters in PEM
  22       format. This means that the parameters can be generated externally using
  23       the certtool command that is part of GnuTLS.
  24
  25       To replace the parameters with new ones, instead of deleting the file
  26       and letting Exim re-create it, you can generate new parameters using
  27       certtool and, when this has been done, replace Exim's cache file by
  28       renaming. The relevant commands are something like this:
  29
  30         # rm -f new.params
  31         # touch new.params
  32         # chown exim:exim new.params
  33         # chmod 0400 new.params
  34         # certtool --generate-privkey --bits 512 >new.params
  35         # echo "" >>new.params
  36         # certtool --generate-dh-params --bits 1024 >> new.params
  37         # mv new.params params
  38
  39       If Exim never has to generate the parameters itself, the possibility of
  40       stalling is removed.
  41
  42 PH/02 A new expansion item for dynamically loading and calling a locally-
  43       written C function is now provided, if Exim is compiled with
  44
  45         EXPAND_DLFUNC=yes
  46
  47       set in Local/Makefile. The facility is not included by default (a
  48       suitable error is given if you try to use it when it is not there.)
  49
  50       If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
  51       router option forbid_filter_dlfunc. If you have unprivileged users on
  52       your system who are permitted to create filter files, you might want to
  53       set forbid_filter_dlfunc=true in the appropriate router, to stop them
  54       using ${dlfunc to run code within Exim.
  55
  56       You load and call an external function like this:
  57
  58         ${dlfunc{/some/file}{function}{arg1}{arg2}...}
  59
  60       Once loaded, Exim remembers the dynamically loaded object so that it
  61       doesn't reload the same object file in the same Exim process (but of
  62       course Exim does start new processes frequently).
  63
  64       There may be from zero to eight arguments to the function. When compiling
  65       a local function that is to be called in this way, local_scan.h should be
  66       included. The Exim variables and functions that are defined by that API
  67       are also available for dynamically loaded functions. The function itself
  68       must have the following type:
  69
  70         int dlfunction(uschar **yield, int argc, uschar *argv[])
  71
  72       Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
  73       function should return one of the following values:
  74
  75       OK            Success. The string that is placed in "yield" is put into
  76                     the expanded string that is being built.
  77
  78       FAIL          A non-forced expansion failure occurs, with the error
  79                     message taken from "yield", if it is set.
  80
  81       FAIL_FORCED   A forced expansion failure occurs, with the error message
  82                     taken from "yield" if it is set.
  83
  84       ERROR         Same as FAIL, except that a panic log entry is written.
  85
  86       When compiling a function that is to be used in this way with gcc,
  87       you need to add -shared to the gcc command. Also, in the Exim build-time
  88       configuration, you must add -export-dynamic to EXTRALIBS.
  89
  90 TF/01 $received_time is a new expansion variable containing the time and date
  91       as a number of seconds since the start of the Unix epoch when the
  92       current message was received.
  93
  94 PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
  95       Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
  96       in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
  97       possible to detect the different versions automatically.
  98
  99 PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
 100       MIME parts in non-SMTP messages. It operates in exactly the same way as
 101       acl_smtp_mime
 102
 103 PH/05 It is now possible to redefine a macro within the configuration file.
 104       The macro must have been previously defined within the configuration (or
 105       an included file). A definition on the command line using the -D option
 106       causes all definitions and redefinitions within the file to be ignored.
 107       In other words, -D overrides any values that are set in the file.
 108       Redefinition is specified by using '==' instead of '='. For example:
 109
 110         MAC1 =  initial value
 111         ...
 112         MAC1 == updated value
 113
 114       Redefinition does not alter the order in which the macros are applied to
 115       the subsequent lines of the configuration file. It is still the same
 116       order in which the macros were originally defined. All that changes is
 117       the macro's value. Redefinition makes it possible to accumulate values.
 118       For example:
 119
 120         MAC1 =  initial value
 121         ...
 122         MAC1 == MAC1 and something added
 123
 124       This can be helpful in situations where the configuration file is built
 125       from a number of other files.
 126
 127 PH/06 Macros may now be defined or redefined between router, transport,
 128       authenticator, or ACL definitions, as well as in the main part of the
 129       configuration. They may not, however, be changed within an individual
 130       driver or ACL, or in the local_scan, retry, or rewrite sections of the
 131       configuration.
 132
 133 PH/07 $acl_verify_message is now set immediately after the failure of a
 134       verification in an ACL, and so is available in subsequent modifiers. In
 135       particular, the message can be preserved by coding like this:
 136
 137          warn  !verify = sender
 138                set acl_m0 = $acl_verify_message
 139
 140       Previously, $acl_verify_message was set only while expanding "message"
 141       and "log_message" when a very denied access.
 142
 143 PH/08 The redirect router has two new options, sieve_useraddress and
 144       sieve_subaddress. These are passed to a Sieve filter to specify the :user
 145       and :subaddress parts of an address. Both options are unset by default.
 146       However, when a Sieve filter is run, if sieve_useraddress is unset, the
 147       entire original local part (including any prefix or suffix) is used for
 148       :user. An unset subaddress is treated as an empty subaddress.
 149
 150 PH/09 Quota values can be followed by G as well as K and M.
 151
 152 PH/10 $message_linecount is a new variable that contains the total number of
 153       lines in the header and body of the message. Compare $body_linecount,
 154       which is the count for the body only. During the DATA and
 155       content-scanning ACLs, $message_linecount contains the number of lines
 156       received. Before delivery happens (that is, before filters, routers, and
 157       transports run) the count is increased to include the Received: header
 158       line that Exim standardly adds, and also any other header lines that are
 159       added by ACLs. The blank line that separates the message header from the
 160       body is not counted. Here is an example of the use of this variable in a
 161       DATA ACL:
 162
 163         deny message   = Too many lines in message header
 164              condition = \
 165                ${if <{250}{${eval: $message_linecount - $body_linecount}}}
 166
 167       In the MAIL and RCPT ACLs, the value is zero because at that stage the
 168       message has not yet been received.
 169
 170 PH/11 In a ${run expansion, the variable $value (which contains the standard
 171       output) is now also usable in the "else" string.
 172
 173
 174 Version 4.50
 175 ------------
 176
 177 The documentation is up-to-date for the 4.50 release.
 178
 179 ****