doc-txt updates for the security changes

[exim.git] / doc / doc-txt / NewStuff

$Cambridge: exim/doc/doc-txt/NewStuff,v 1.176 2010/06/14 18:51:10 pdp Exp $

New Features in Exim
--------------------

This file contains descriptions of new features that have been added to Exim.
Before a formal release, there may be quite a lot of detail so that people can
test from the snapshots or the CVS before the documentation is updated. Once
the documentation is updated, this file is reduced to a short list.


Version 4.73
------------

 NOTE: this version is not guaranteed backwards-compatible, please read the
       items below carefully

 1. A new main configuration option, "openssl_options", is available if Exim
    is built with SSL support provided by OpenSSL.  The option allows
    administrators to specify OpenSSL options to be used on connections;
    typically this is to set bug compatibility features which the OpenSSL
    developers have not enabled by default.  There may be security
    consequences for certain options, so these should not be changed
    frivolously.

 2. A new pipe transport option, "permit_coredumps", may help with problem
    diagnosis in some scenarios.  Note that Exim is typically installed as
    a setuid binary, which on most OSes will inhibit coredumps by default,
    so that safety mechanism would have to be overriden for this option to
    be able to take effect.

 3. ClamAV 0.95 is now required for ClamAV support in Exim, unless
    Local/Makefile sets: WITH_OLD_CLAMAV_STREAM=yes
    Note that this switches Exim to use a new API ("INSTREAM") and a future
    release of ClamAV will remove support for the old API ("STREAM").

    The av_scanner option, when set to "clamd", now takes an optional third
    part, "local", which causes Exim to pass a filename to ClamAV instead of
    the file content.  This is the same behaviour as when clamd is pointed at
    a Unix-domain socket.  For example:

      av_scanner = clamd:192.0.2.3 1234:local

    ClamAV's ExtendedDetectionInfo response format is now handled.

 4. There is now a -bmalware option, restricted to admin users.  This option
    takes one parameter, a filename, and scans that file with Exim's
    malware-scanning framework.  This is intended purely as a debugging aid
    to ensure that Exim's scanning is working, not to replace other tools.
    Note that the ACL framework is not invoked, so if av_scanner references
    ACL variables without a fallback then this will fail.

 5. There is a new expansion operator, "reverse_ip", which will reverse IP
    addresses; IPv4 into dotted quad, IPv6 into dotted nibble.  Examples:

      ${reverse_ip:192.0.2.4}
       -> 4.2.0.192
      ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3}
       -> 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2

 6. There is a new ACL control called "debug", to enable debug logging.
    This allows selective logging of certain incoming transactions within
    production environments, with some care.  It takes two options, "tag"
    and "opts"; "tag" is included in the filename of the log and "opts"
    is used as per the -d<options> command-line option.  Examples, which
    don't all make sense in all contexts:

      control = debug
      control = debug/tag=.$sender_host_address
      control = debug/opts=+expand+acl
      control = debug/tag=.$message_exim_id/opts=+expand

 7. It has always been implicit in the design and the documentation that
    "the Exim user" is not root.  src/EDITME said that using root was
    "very strongly discouraged".  This is not enough to keep people from
    shooting themselves in the foot in days when many don't configure Exim
    themselves but via package build managers.  The security consequences of
    running various bits of network code are severe if there should be bugs in
    them.  As such, the Exim user may no longer be root.  If configured
    statically, Exim will refuse to build.  If configured as ref:user then Exim
    will exit shortly after start-up.  If you must shoot yourself in the foot,
    then henceforth you will have to maintain your own local patches to strip
    the safeties off.

 8. There is a new expansion operator, bool_lax{}.  Where bool{} uses the ACL
    condition logic to determine truth/failure and will fail to expand many
    strings, bool_lax{} uses the router condition logic, where most strings
    do evaluate true.
    Note: bool{00} is false, bool_lax{00} is true.

 9. Routers now support multiple "condition" tests,

10. There is now a runtime configuration option "tcp_wrappers_daemon_name".
    Setting this allows an admin to define which entry in the tcpwrappers
    config file will be used to control access to the daemon.  This option
    is only available when Exim is built with USE_TCP_WRAPPERS.  The
    default value is set at build time using the TCP_WRAPPERS_DAEMON_NAME
    build option.

11. [POSSIBLE CONFIG BREAKAGE] The default value for system_filter_user is now
    the Exim run-time user, instead of root.

12. [POSSIBLE CONFIG BREAKAGE] ALT_CONFIG_ROOT_ONLY is no longer optional and
    is forced on.  This is mitigated by the new build option
    TRUSTED_CONFIG_PREFIX_LIST which defines a list of pathname prefices which
    are trusted; if a config file is owned by root and is under that prefix,
    then it may be used by the Exim run-time user.

13. [POSSIBLE CONFIG BREAKAGE] The Exim user is no longer automatically
    trusted to supply -D<Macro[=Value]> overrides on the command-line.  Going
    forward, we recommend using TRUSTED_CONFIG_PREFIX_LIST with shim configs
    that include the main config.  As a transition mechanism, we are
    temporarily providing a work-around: the new build option
    WHITELIST_D_MACROS provides a colon-separated list of macro names which
    may be overriden by the Exim run-time user.  The values of these macros
    are constrained to the regex ^[A-Za-z0-9_/.-]*$ (which explicitly does
    allow for empty values).


Version 4.72
------------

 1. TWO SECURITY FIXES: one relating to mail-spools which are globally
    writable, the other to locking of MBX folders (not mbox).

 2. MySQL stored procedures are now supported.

 3. The dkim_domain transport option is now a list, not a single string, and
    messages will be signed for each element in the list (discarding
    duplicates).

 4. The 4.70 release unexpectedly changed the behaviour of dnsdb TXT lookups
    in the presence of multiple character strings within the RR. Prior to 4.70,
    only the first string would be returned.  The dnsdb lookup now, by default,
    preserves the pre-4.70 semantics, but also now takes an extended output
    separator specification.  The separator can be followed by a semicolon, to
    concatenate the individual text strings together with no join character,
    or by a comma and a second separator character, in which case the text
    strings within a TXT record are joined on that second character.
    Administrators are reminded that DNS provides no ordering guarantees
    between multiple records in an RRset.  For example:

      foo.example.  IN TXT "a" "b" "c"
      foo.example.  IN TXT "d" "e" "f"

      ${lookup dnsdb{>/ txt=foo.example}}   -> "a/d"
      ${lookup dnsdb{>/; txt=foo.example}}  -> "def/abc"
      ${lookup dnsdb{>/,+ txt=foo.example}} -> "a+b+c/d+e+f"


Version 4.70 / 4.71
-------------------

 1. Native DKIM support without an external library.
    (Note that if no action to prevent it is taken, a straight upgrade will
    result in DKIM verification of all signed incoming emails.  See spec
    for details on conditionally disabling)

 2. Experimental DCC support via dccifd (contributed by Wolfgang Breyha).

 3. There is now a bool{} expansion condition which maps certain strings to
    true/false condition values (most likely of use in conjunction with the
    and{} expansion operator).

 4. The $spam_score, $spam_bar and $spam_report variables are now available
    at delivery time.

 5. exim -bP now supports "macros", "macro_list" or "macro MACRO_NAME" as
    options, provided that Exim is invoked by an admin_user.

 6. There is a new option gnutls_compat_mode, when linked against GnuTLS,
    which increases compatibility with older clients at the cost of decreased
    security.  Don't set this unless you need to support such clients.

 7. There is a new expansion operator, ${randint:...} which will produce a
    "random" number less than the supplied integer.  This randomness is
    not guaranteed to be cryptographically strong, but depending upon how
    Exim was built may be better than the most naive schemes.

 8. Exim now explicitly ensures that SHA256 is available when linked against
    OpenSSL.

 9. The transport_filter_timeout option now applies to SMTP transports too.


Version 4.69
------------

 1. Preliminary DKIM support in Experimental.


Version 4.68
------------

 1. The body_linecount and body_zerocount C variables are now exported in the
    local_scan API.

 2. When a dnslists lookup succeeds, the key that was looked up is now placed
    in $dnslist_matched. When the key is an IP address, it is not reversed in
    this variable (though it is, of course, in the actual lookup). In simple
    cases, for example:

      deny dnslists = spamhaus.example

    the key is also available in another variable (in this case,
    $sender_host_address). In more complicated cases, however, this is not
    true. For example, using a data lookup might generate a dnslists lookup
    like this:

      deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...

    If this condition succeeds, the value in $dnslist_matched might be
    192.168.6.7 (for example).

 3. Authenticators now have a client_condition option. When Exim is running as
    a client, it skips an authenticator whose client_condition expansion yields
    "0", "no", or "false". This can be used, for example, to skip plain text
    authenticators when the connection is not encrypted by a setting such as:

      client_condition = ${if !eq{$tls_cipher}{}}

    Note that the 4.67 documentation states that $tls_cipher contains the
    cipher used for incoming messages. In fact, during SMTP delivery, it
    contains the cipher used for the delivery. The same is true for
    $tls_peerdn.

 4. There is now a -Mvc <message-id> option, which outputs a copy of the
    message to the standard output, in RFC 2822 format. The option can be used
    only by an admin user.

 5. There is now a /noupdate option for the ratelimit ACL condition. It
    computes the rate and checks the limit as normal, but it does not update
    the saved data. This means that, in relevant ACLs, it is possible to lookup
    the existence of a specified (or auto-generated) ratelimit key without
    incrementing the ratelimit counter for that key.

    In order for this to be useful, another ACL entry must set the rate
    for the same key somewhere (otherwise it will always be zero).

    Example:

    acl_check_connect:
      # Read the rate; if it doesn't exist or is below the maximum
      # we update it below
      deny ratelimit = 100 / 5m / strict / noupdate
           log_message = RATE: $sender_rate / $sender_rate_period \
                         (max $sender_rate_limit)

      [... some other logic and tests...]

      warn ratelimit = 100 / 5m / strict / per_cmd
           log_message = RATE UPDATE: $sender_rate / $sender_rate_period \
                         (max $sender_rate_limit)
           condition = ${if le{$sender_rate}{$sender_rate_limit}}

      accept

 6. The variable $max_received_linelength contains the number of bytes in the
    longest line that was received as part of the message, not counting the
    line termination character(s).

 7. Host lists can now include +ignore_defer and +include_defer, analagous to
    +ignore_unknown and +include_unknown. These options should be used with
    care, probably only in non-critical host lists such as whitelists.

 8. There's a new option called queue_only_load_latch, which defaults true.
    If set false when queue_only_load is greater than zero, Exim re-evaluates
    the load for each incoming message in an SMTP session. Otherwise, once one
    message is queued, the remainder are also.

 9. There is a new ACL, specified by acl_smtp_notquit, which is run in most
    cases when an SMTP session ends without sending QUIT. However, when Exim
    itself is is bad trouble, such as being unable to write to its log files,
    this ACL is not run, because it might try to do things (such as write to
    log files) that make the situation even worse.

    Like the QUIT ACL, this new ACL is provided to make it possible to gather
    statistics. Whatever it returns (accept or deny) is immaterial. The "delay"
    modifier is forbidden in this ACL.

    When the NOTQUIT ACL is running, the variable $smtp_notquit_reason is set
    to a string that indicates the reason for the termination of the SMTP
    connection. The possible values are:

      acl-drop                 Another ACL issued a "drop" command
      bad-commands             Too many unknown or non-mail commands
      command-timeout          Timeout while reading SMTP commands
      connection-lost          The SMTP connection has been lost
      data-timeout             Timeout while reading message data
      local-scan-error         The local_scan() function crashed
      local-scan-timeout       The local_scan() function timed out
      signal-exit              SIGTERM or SIGINT
      synchronization-error    SMTP synchronization error
      tls-failed               TLS failed to start

    In most cases when an SMTP connection is closed without having received
    QUIT, Exim sends an SMTP response message before actually closing the
    connection. With the exception of acl-drop, the default message can be
    overridden by the "message" modifier in the NOTQUIT ACL. In the case of a
    "drop" verb in another ACL, it is the message from the other ACL that is
    used.

10. For MySQL and PostgreSQL lookups, it is now possible to specify a list of
    servers with individual queries. This is done by starting the query with
    "servers=x:y:z;", where each item in the list may take one of two forms:

    (1) If it is just a host name, the appropriate global option (mysql_servers
        or pgsql_servers) is searched for a host of the same name, and the
        remaining parameters (database, user, password) are taken from there.

    (2) If it contains any slashes, it is taken as a complete parameter set.

    The list of servers is used in exactly the same was as the global list.
    Once a connection to a server has happened and a query has been
    successfully executed, processing of the lookup ceases.

    This feature is intended for use in master/slave situations where updates
    are occurring, and one wants to update a master rather than a slave. If the
    masters are in the list for reading, you might have:

      mysql_servers = slave1/db/name/pw:slave2/db/name/pw:master/db/name/pw

    In an updating lookup, you could then write

      ${lookup mysql{servers=master; UPDATE ...}

    If, on the other hand, the master is not to be used for reading lookups:

      pgsql_servers = slave1/db/name/pw:slave2/db/name/pw

    you can still update the master by

      ${lookup pgsql{servers=master/db/name/pw; UPDATE ...}

11. The message_body_newlines option (default FALSE, for backwards
    compatibility) can be used to control whether newlines are present in
    $message_body and $message_body_end. If it is FALSE, they are replaced by
    spaces.


Version 4.67
------------

 1. There is a new log selector called smtp_no_mail, which is not included in
    the default setting. When it is set, a line is written to the main log
    whenever an accepted SMTP connection terminates without having issued a
    MAIL command.

 2. When an item in a dnslists list is followed by = and & and a list of IP
    addresses, the behaviour was not clear when the lookup returned more than
    one IP address. This has been solved by the addition of == and =& for "all"
    rather than the default "any" matching.

 3. Up till now, the only control over which cipher suites GnuTLS uses has been
    for the cipher algorithms. New options have been added to allow some of the
    other parameters to be varied.

 4. There is a new compile-time option called ENABLE_DISABLE_FSYNC. When it is
    set, Exim compiles a runtime option called disable_fsync.

 5. There is a new variable called $smtp_count_at_connection_start.

 6. There's a new control called no_pipelining.

 7. There are two new variables called $sending_ip_address and $sending_port.
    These are set whenever an SMTP connection to another host has been set up.

 8. The expansion of the helo_data option in the smtp transport now happens
    after the connection to the server has been made.

 9. There is a new expansion operator ${rfc2047d: that decodes strings that
    are encoded as per RFC 2047.

10. There is a new log selector called "pid", which causes the current process
    id to be added to every log line, in square brackets, immediately after the
    time and date.

11. Exim has been modified so that it flushes SMTP output before implementing
    a delay in an ACL. It also flushes the output before performing a callout,
    as this can take a substantial time. These behaviours can be disabled by
    obeying control = no_delay_flush or control = no_callout_flush,
    respectively, at some earlier stage of the connection.

12. There are two new expansion conditions that iterate over a list. They are
    called forany and forall.

13. There's a new global option called dsn_from that can be used to vary the
    contents of From: lines in bounces and other automatically generated
    messages ("delivery status notifications" - hence the name of the option).

14. The smtp transport has a new option called hosts_avoid_pipelining.

15. By default, exigrep does case-insensitive matches. There is now a -I option
    that makes it case-sensitive.

16. A number of new features ("addresses", "map", "filter", and "reduce") have
    been added to string expansions to make it easier to process lists of
    items, typically addresses.

17. There's a new ACL modifier called "continue". It does nothing of itself,
    and processing of the ACL always continues with the next condition or
    modifier. It is provided so that the side effects of expanding its argument
    can be used.

18. It is now possible to use newline and other control characters (those with
    values less than 32, plus DEL) as separators in lists.

19. The exigrep utility now has a -v option, which inverts the matching
    condition.

20. The host_find_failed option in the manualroute router can now be set to
    "ignore".


Version 4.66
------------

No new features were added to 4.66.


Version 4.65
------------

No new features were added to 4.65.


Version 4.64
------------

 1. ACL variables can now be given arbitrary names, as long as they start with
    "acl_c" or "acl_m" (for connection variables and message variables), are at
    least six characters long, with the sixth character being either a digit or
    an underscore.

 2. There is a new ACL modifier called log_reject_target. It makes it possible
    to specify which logs are used for messages about ACL rejections.

 3. There is a new authenticator called "dovecot". This is an interface to the
    authentication facility of the Dovecot POP/IMAP server, which can support a
    number of authentication methods.

 4. The variable $message_headers_raw provides a concatenation of all the
    messages's headers without any decoding. This is in contrast to
    $message_headers, which does RFC2047 decoding on the header contents.

 5. In a DNS black list, if two domain names, comma-separated, are given, the
    second is used first to do an initial check, making use of any IP value
    restrictions that are set. If there is a match, the first domain is used,
    without any IP value restrictions, to get the TXT record.

 6. All authenticators now have a server_condition option.

 7. There is a new command-line option called -Mset. It is useful only in
    conjunction with -be (that is, when testing string expansions). It must be
    followed by a message id; Exim loads the given message from its spool
    before doing the expansions.

 8. Another similar new command-line option is called -bem. It operates like
    -be except that it must be followed by the name of a file that contains a
    message.

 9. When an address is delayed because of a 4xx response to a RCPT command, it
    is now the combination of sender and recipient that is delayed in
    subsequent queue runs until its retry time is reached.

10. Unary negation and the bitwise logical operators and, or, xor, not, and
    shift, have been added to the eval: and eval10: expansion items.

11. The variables $interface_address and $interface_port have been renamed
    as $received_ip_address and $received_port, to make it clear that they
    relate to message reception rather than delivery. (The old names remain
    available for compatibility.)

12. The "message" modifier can now be used on "accept" and "discard" acl verbs
    to vary the message that is sent when an SMTP command is accepted.


Version 4.63
------------

1. There is a new Boolean option called filter_prepend_home for the redirect
   router.

2. There is a new acl, set by acl_not_smtp_start, which is run right at the
   start of receiving a non-SMTP message, before any of the message has been
   read.

3. When an SMTP error message is specified in a "message" modifier in an ACL,
   or in a :fail: or :defer: message in a redirect router, Exim now checks the
   start of the message for an SMTP error code.

4. There is a new parameter for LDAP lookups called "referrals", which takes
   one of the settings "follow" (the default) or "nofollow".

5. Version 20070721.2 of exipick now included, offering these new options:
    --reverse
        After all other sorting options have bee processed, reverse order
        before displaying messages (-R is synonym).
    --random
        Randomize order of matching messages before displaying.
    --size
        Instead of displaying the matching messages, display the sum
        of their sizes.
    --sort <variable>[,<variable>...]
        Before displaying matching messages, sort the messages according to
        each messages value for each variable.
    --not
        Negate the value for every test (returns inverse output from the
        same criteria without --not).


Version 4.62
------------

1. The ${readsocket expansion item now supports Internet domain sockets as well
   as Unix domain sockets. If the first argument begins "inet:", it must be of
   the form "inet:host:port". The port is mandatory; it may be a number or the
   name of a TCP port in /etc/services. The host may be a name, or it may be an
   IP address. An ip address may optionally be enclosed in square brackets.
   This is best for IPv6 addresses. For example:

     ${readsocket{inet:[::1]:1234}{<request data>}...

   Only a single host name may be given, but if looking it up yield more than
   one IP address, they are each tried in turn until a connection is made. Once
   a connection has been made, the behaviour is as for ${readsocket with a Unix
   domain socket.

2. If a redirect router sets up file or pipe deliveries for more than one
   incoming address, and the relevant transport has batch_max set greater than
   one, a batch delivery now occurs.

3. The appendfile transport has a new option called maildirfolder_create_regex.
   Its value is a regular expression. For a maildir delivery, this is matched
   against the maildir directory; if it matches, Exim ensures that a
   maildirfolder file is created alongside the new, cur, and tmp directories.


Version 4.61
------------

The documentation is up-to-date for the 4.61 release. Major new features since
the 4.60 release are:

. An option called disable_ipv6, to disable the use of IPv6 completely.

. An increase in the number of ACL variables to 20 of each type.

. A change to use $auth1, $auth2, and $auth3 in authenticators instead of $1,
  $2, $3, (though those are still set) because the numeric variables get used
  for other things in complicated expansions.

. The default for rfc1413_query_timeout has been changed from 30s to 5s.

. It is possible to use setclassresources() on some BSD OS to control the
  resources used in pipe deliveries.

. A new ACL modifier called add_header, which can be used with any verb.

. More errors are detectable in retry rules.

There are a number of other additions too.


Version 4.60
------------

The documentation is up-to-date for the 4.60 release. Major new features since
the 4.50 release are:

. Support for SQLite.

. Support for IGNOREQUOTA in LMTP.

. Extensions to the "submission mode" features.

. Support for Client SMTP Authorization (CSA).

. Support for ratelimiting hosts and users.

. New expansion items to help with the BATV "prvs" scheme.

. A "match_ip" condition, that matches an IP address against a list.

There are many more minor changes.

****