unrealircd/doc/RELEASE-NOTES

UnrealIRCd 5.0.0-alpha1 Release Notes
======================================

IMPORTANT: UnrealIRCd 5 is currently in "alpha" phase. This means it
may crash or behave weird. Do not run this on production servers!
The alpha releases are there to show the current state of UnrealIRCd 5.
UnrealIRCd 5 is not yet feature complete at this point; about 80% of
the planned functionality is there.

Summary
--------
The most visible change to end-users is channel history.
Various modules from Gottem have been integrated and enhanced.
Channel settings of +P channels and *LINES are saved in a database and
restored on startup (via 'channeldb' and 'tkldb' respectively).
Channel mode +L has a slight change of meaning, the existing floodprot
mode (+f) has a new type to prevent repeated messages and a new drop action.
A few extended bans have been added as well (~f and ~p).
For advanced users we now have more dynamic configuration options
where you can define variables and use them in the configuration file.
Finally, there have been speed improvements, we use better defaults and
have added more countermeasures and options against spambots.
Under the hood a lot of the source code was changed and cleaned up.

Enhancements
-------------
* Support for server generated message tags, which allows us to communicate
  additional information in protocol messages such as in JOIN and PRIVMSG.
  Currently implemented and permitted message tags are:
  * account: communicate the services account that a user uses
  * msgid: assign an unique message id to each message
  * time: assign a time label to each message
  The last two are mainly for history playback.
* Support for IRCv3 "echo-message", which helps clients, among other things,
  to see if the message you sent was altered in any way, eg: censored,
  stripped from color, etc.
* Support for IRCv3 "BATCH", needed for some other features.
* Recording and playback of channel history when channel mode +H is set.
  The syntax is: +H max-lines-to-record:max-time-to-record-in-minutes.
  For example: +H 50:1440 means the last 50 messages will be stored and no
  message will be stored longer than 1440 minutes (1 day).
  The channel history is then played back when joining such a channel,
  but with two things to keep in mind:
  1) The client must support the 'server-time' CAP ('time' message tag),
     otherwise history is not shown. Any modern IRC client supports this.
  2) Only a maximum of 15 lines are played back on-join by default
  The reason for the maximum 15 lines on-join playback is that this can
  be quite annoying if you rejoin repeatedly and as to not flood the users
  screen too much (unwanted). In the future we will support a mechanism
  for clients to "fetch" history - rather than sending it on-join - so
  they can fetch more than the 15 lines, up to the number of lines and
  time configured in the +H channel mode.
  You can configure the exact number of lines that are played back and
  all the limits that apply to +H via set::history::channel.
* For saving and retrieving history we currently have the following options:
  * history_backend_mem: channel history is stored in memory.
    This is very fast but also means history is lost on restart.
  * history_backend_null: don't store channel history at all.
    This can be useful to load on servers with no users on it, such as a
    hub server, where storing history is unnecessary.
  As you can see there is currently no 'disk' backend. However, in the
  future more options may be added. Also note that 3rd party modules
  can add history backends as well.
* Channel mode +L now kicks in for any rejected join, so not just for +l but
  also for +b, +i, +O, +z, +R and +k. If, for example, the channel is
  +L #insecure and also +z then, when an insecure user ties to join, they
  will be redirected to #insecure.
* New extended ban ~f to forward users to the specified channel if the ban
  matches. Example: +b ~f:#badisp:*!*@*.isp.org
* Channel mode +f now has a 'd' action: drop message. This will send an
  error message to the user and not show the message in the channel but
  otherwise do nothing (no kick or ban). Example: +f [5t#d]:15 will limit
  sending a maximum of 5 messages per 15 seconds per-user and drop any
  messages sent above that limit.
* Channel mode +f now has 'r' floodtype to prevent repeated lines. This will
  compare the current message to the last message and the one before that
  the user sent to the channel. If it's a repeat then the user can be
  kicked (the default action), the message can be dropped ('d') or the
  user can be banned ('b'). Example: +f [1r#d]:15.
  If you want to permit 1 repeated line but not 2 then use: +f [2r#d]:15
* New module tkldb (loaded by default): all *LINES and spamfilters are now
  saved across reboots. No need for services for that anymore.
* New module channeldb (loaded by default): saves and restores all channel
  settings including topic, modes, bans etc. of +P (persistent) channels.
* New module restrict-commands, which allows you to restrict any IRC
  command based on criteria such as "how long is this user connected",
  "is this user registered (has a services account)" etc.
  The example.conf now ships with configuration to disable LIST the
  first 60 seconds and disable INVITE the first 120 seconds.
  If you are having spambot problems then tweaking this configuration
  may be helpful to you.
  See https://www.unrealircd.org/docs/Set_block#set::restrict-commands
* New module rmtkl (loaded by default): this allows you to remove TKL's
  such as GLINEs easily via the /RMTKL command.
* New module webredir. Quite some people run their IRCd on port 443 or 80
  so their users can avoid firewall restrictions in place. In such a case,
  with this module, you can now send a HTTP redirect in case some user
  enters your IRC server name in their browser. Eg https://irc.example.org/
  can be made to redirect to https://www.example.org/
  See https://www.unrealircd.org/docs/Set_block#set::webredir::url
* The reputation and connthrottle modules are now loaded by default.
  Just as a reminder, what these do is classifying your users in "known
  users (known IP's)" and "unknown IP's" for IP's that have not been
  seen before (or only for a short amount of time). Then, when there
  is a connection flood, unknown/new IP addresses are throttled at
  20 connections per minute, while known users are always allowed in.
  For more information, see https://www.unrealircd.org/docs/Connthrottle
* Add support for more dynamic configuration via @define and @if.
  This is mostly for power users, in particular users who share the same
  configuration file across several servers. New features are:
  * You can define variables, like:
    @define $SERVER "hub.example.org"
    ..and then use $SERVER anywhere in the configuration file such as:
    me {
            name "$SERVER";
            [..]
    }
  * You can have conditional configuration as well:
    @if $SERVER == "hub.example.org"
    link {
            [..]
    }
    @endif
  * In @if you can use module-loaded() to have conditional configuration
    based on if a module is loaded or not. For example, we have the
    following code in help.conf for HELPOP CHMODES so the line is only
    displayed if the chanmodes/noctcp module is loaded:
    helpop chmodes {
            [..]
    @if module-loaded("chanmodes/noctcp")
            " C = No CTCPs allowed in the channel [h]";
    @endif
    }
* New extban ~p (+b ~p:*!*@*.nl) to hide PART and QUIT messages.
* You will now see a warning when a server is not responding even
  before they time out. How long to wait for a PONG reply upon PING
  can be changed via set::ping-warning and defaults to 15 seconds.
  If you see the warning frequently then your connection is flakey.
* Add new setting set::broadcast-channel-messages which defines when
  channel messages are sent across server links. The default setting
  is 'auto' which is the correct setting for pretty much everyone.
* Add new option set::part-instead-of-quit-on-comment-change:
  when a QUIT message is changed due to channel restrictions, such as
  stripping color or censoring a word, we normally change the QUIT
  message. This has an effect on ALL channels, not just the one that
  imposed the restrictions. While we feel that is the best tradeoff,
  there is now also this new option (off by default) that will change
  the QUIT into a PART in such a case, so the other channels that
  do not have the restrictions (eg: are -S and -G) can still see the
  original QUIT message.

Changed
--------
* Modules lost their m_ prefix, so for example m_map is now just map.
  Also the modules in cap/ are now directly in modules.
* More modules that were previously PERM (permanent) can now be unloaded
  and reloaded on the fly. This allows more "hotfixing" without restart
  in case of a bug and also more control for admins at runtime.
  Only <5 modules out of 173 are permanent now.
* User mode +T now blocks channel CTCPs as well.
* The authprompt module is now loaded by default. This means that if
  you do a soft kline on someone (eg: KLINE %*@*.badisp) then the user
  has a chance to authenticate to services, even without SASL, and
  bypass the ban if (s)he is authenticated.
* The WHOX module is now used by default. Previously it was optional.
  WHOX enhances the "WHO" output, providing additional information to
  IRC clients such as the services account that someone is using.
  It is also more universal than standard WHO. Unfortunately this also
  means the WHO syntax changed to something less logical.
* At many places the term "SSL" has been changed to "SSL/TLS" or "TLS".
  Configuration items (eg: set::ssl to set::tls) have been renamed
  as well and so have directories (eg: conf/ssl to conf/tls).
  The old configuration names still work and currently does NOT raise
  any warning. Also, when upgrading an existing installation on *NIX,
  the conf/tls directory will be symlinked to conf/ssl as to not break
  any Let's Encrypt certificate scripts.
* It is now mandatory to have at least one open SSL/TLS port, otherwise
  UnrealIRCd will refuse to boot. Previously this was a warning.
* IRCOps now need to use SSL/TLS in order to oper up, as the
  set::plaintext-policy::oper default setting is now 'deny'.
  Similarly, set::outdated-tls-policy::oper is now also 'deny'.
* set::outdated-tls-policy::server is now 'deny' as well, since all
  servers should use reasonable SSL/TLS protocols and ciphers.
* The default generated certificated has been changed from RSA 4096 bits
  to Elliptic Curve Cryptography "384r1". This provides the same amount
  of security but at higher speed. This only affects the default self-
  signed certificate. You can still use RSA certificates just fine.
* If you do use an RSA certificate, we now require it to be at least
  2048 bits otherwise UnrealIRCd will refuse to boot.
* When matching allow { } blocks, we now always continue with the next
  block (if any) if the password did not match or no password was
  specified. In other words, allow::options::nopasscont is now the
  default and we behave as if there was a ::wrongpasscont too.
* All snomasks are now oper-only. Previously some were not, which
  was confusing and could lead to information leaks.
  Also removed weird set::snomask-on-connect accordingly.
* The IRCd now uses hash tables that are resilient against hash table
  attacks. Also, the hash tables have increased in size to speed things
  up when looking up nick names etc.
* Server options in VERSION (eg: Fhin6OoEMR3) are no longer shown to
  normal users. They don't mean much nowadays anyway.
* We now default to system libs (eg: --with-system-pcre2 is assumed)

Minor issues fixed
-------------------
* Specifying a custom OpenSSL/LibreSSL path works now

Removed
--------
* Extended ban ~R (registered nick): this was the old method to match
  registered users. Everyone should use ~a (services account) instead.
* The old TRE 'posix' regex method has been removed because the TRE
  library is no longer maintained for over a decade and contains many
  bugs. (It was already deprecated in UnrealIRCd 4.2.3). Use type
  'regex' instead, which uses the modern PCRE2 regex engine.
* Timesync support has been removed. Use your OS time synchronization
  instead. (Note that Timesync was already disabled by default in 2018)
* Changing time offsets via TSCTL OFFSET and TSCTL SVSTIME are no longer
  supported. Use your OS time synchronization (NTP!). Adjustments via
  TSCTL are simply not accurate enough.
* The 'nopost' module was removed since it no longer serves any useful
  purpose. UnrealIRCd already protects against these kind of attacks
  via ping cookies (set::ping-cookie, enabled by default).

Developers
-----------
IMPORTANT: As long as UnrealIRCd 5 is in alpha stage, we do not suggest
3rd party module authors to start porting modules yet from U4 to U5.
Of course you may, but the module API is still very likely to change
so you may have to do certain (other) changes again next alpha release.
It is therefore best to wait until beta1. You have been warned ;).
* In UnrealIRCd 5, during development, --enable-asan is ON by default
  to catch more bugs. This also means an up to 10x slowdown and more
  memory usage. When we reach 5.0.0 stable this will be turned off.
* We now use our own BuildBot infrastructure, so Travis-CI and AppVeyor
  have been removed.
* We now use a new test framework.
* New function new_message() which should be called when a new message
  is sent, or at least for all channel events. It adds (or inherits)
  message tags like 'account', 'msgid', 'time', etc.
* Many send functions now take an extra MessageTag *mtags parameter,
  including but not limited to: sendto_one() and sendto_server().
* New single unified sendto_channel() and sendto_local_common_channels()
  functions that are used by all the channel commands.
* Numerics should now be sent using sendnumeric(). There's also
  a format string version sendnumericfmt() in case you need it.
* The parameters in several hooks have changed. Many now have an
  extra MessageTag *mtags parameter. Sometimes there are other changes
  as well, for example HOOKTYPE_CHANMSG now has 4 extra parameters.
* New HOOKTYPE_IS_HANDSHAKE_FINISHED. If a module returns 0 there, then
  the register_user() function will not be called and the user will
  not come online (yet). This is used by CAP and some other stuff.
  Can be useful if your module needs to "hold" a user in the registration
  phase.
* The function is_module_loaded() now takes a relative path like
  "usermodes/noctcp" because with just "ctcp" one could not see the
  difference between usermodes/noctcp and chanmodes/noctcp.
* CHFL_CHANPROT is now CHFL_CHANADMIN, is_chanprot() is now is_chanadmin()
* All hash tables now use SipHash, which is a hash function that is
  resilient against hash table attacks. If you, as a module dev, too
  use any hash tables anywhere (note: this is quite rare), then you
  are recommended to use our functions, see the functions siphash()
  and siphash_nocase() in src/hash.c.
* The random generator has been updated to use ChaCha (more modern).
* You can now save pointers and integers etc. across rehashes by using
  LoadPersistentPointer() and SavePersistentPointer(). For an example,
  see src/modules/chanmodes/floodprot.c how this can be used.
  Note that there can be no struct or type changes between rehashes.
* New ModData types: MODDATA_LOCALVAR and MODDA_GLOBALVAR. These are
  settings or things that are locally or globally identified by the
  variable name only and not attached to any user/channel.
* Various files have been renamed. As previously mentioned, the m_
  prefix was dropped in src/modules/m_*.c. Similarly the s_ prefix
  was dropped in src/s_*.c since it no longer had meaning. Also some
  files have been deleted and integrated elsewhere or renamed to
  have a name that better reflects their true meaning.

Server protocol
----------------
* Surprisingly little has been changed in the server to server protocol
  between UnrealIRCd 4 and UnrealIRCd 5.
* "PROTOCTL MTAGS" indicates that the server is capable of handling
  message tags and that the server can cope with 4K lines. (Note that
  the ordinary non-message-tag part is still limited to 512 bytes).