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Server Hide Reference |
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$Id$ |
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Copyright (c) 2001-2020 ircd-hybrid development team |
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---------------------------------------------------------------------- |
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Due to pressures from abusers, the Hybrid developers have created a set of |
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options to limit what users can and cannot do on the server. Each option |
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can be enabled or disabled at runtime. |
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This document describes the ircd-hybrid implementation of the server hiding |
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ideas originated by (and credited to) numerous people. |
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* LINKS as a file: This option is always enabled. It will generate a |
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file at a certain interval, defined by the flatten_links_delay in |
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ircd.conf, that contains the current LINKS data. This data is sent |
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to users whenever a LINKS is requested. Opers will always see the |
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current server structure. |
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The file that the LINKS data is stored in is by default var/lib/links.txt. |
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The benefits of this are that transient splits will not be seen by |
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users issuing LINKS commands, and if a server is split, users can |
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still see what other servers are normally available. |
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* Flattened LINKS: This option forces every server to look as if it is |
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connected to the local server. Users will see a flat LINKS tree. |
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The benefit to using LINKS flattening is that users cannot get |
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information on how servers are routed. |
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The flatten_links in the serverhide {} block in the ircd.conf controls |
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this feature. |
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As a side effect, all netsplit quit messages will appear to originate |
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from the local server. |
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+--------------------------------------------------------------------+ |
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| Flattened LINKS is needed for any network that uses the hidden hub | |
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| option. See below for more details. | |
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+--------------------------------------------------------------------+ |
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* Hidden server option: This option will hide the server from a |
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flattened LINKS list on other servers. Opers will of course see the |
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true routing of the network. |
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This is controlled by the hidden option in ircd.conf. |
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+--------------------------------------------------------------------+ |
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| Technically, this code is a hack. With this option enabled, the | |
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| server will prepend '(H) ' to the server info field when | |
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| connecting to other servers. Other servers must understand that | |
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| the (H) means hidden. | |
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+--------------------------------------------------------------------+ |
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* The hide_servers option forces the server to not be shown when a user |
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issues WHOIS and other commands which may show what server a user is |
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on. |
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Local user counts, as normally displayed in LUSERS, and the 255 |
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numeric, will be shown with the same values as the global counts. |
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Displaying it this way will help protect servers and avoid breaking |
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scripts that depend on the 265 and 266 numerics on connect. |
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To be effective, this option must be used network wide. |
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* The disable_remote_commands option takes care of most of the remaining |
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issues. These include, for example, "ADMIN some.hub.server", "VERSION |
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someuser", and similar commands. A server with this option enabled will |
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only prevent local users from issuing remote commands. Remote users |
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will not be affected. |
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Remote WHOIS is not blocked. It is, however, restricted to only |
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querying WHOIS nick nick. The ircd will disregard the server parameter |
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and always use queried nick. |
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* All server modes appear to originate from the server you are using. |
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This feature is not tunable; and opers also do not see the real server |
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setting the mode. |
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Each item is briefly described in the serverhide {} block in reference.conf. |
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---------------------------------------------------------------------- |
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Using Non-QS Compliant Hubs |
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The flattened LINKS option will, as a side effect, display all user QUITs |
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due to network splits in the following format: |
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:user QUIT :*.net *.split |
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This works extremely well as long as all servers on your network are |
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compliant with the QS capability, which sends a single SQUIT to the |
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network when a server (or tree of servers) splits. All quit messages are |
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generated on the local server. Certain older servers do not have this |
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ability, and as such will generate their own quit messages for users who |
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left because of the split. This can cause leaks in the hub server names |
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and the structure of the network. |
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A quick example is the following network structure: |
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servA(Hyb7) --- hubA(nonQS) --- servB(not-important) |
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When servB splits from hubA, hubA will generate a QUIT command for every |
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user on servB (and anything behind servB). Since the QUIT message was not |
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created on your server, with server hiding enabled, the QUIT message will |
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contain the real server names. |
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The only way to prevent this leak on a network is to only use hubs |
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supporting the QS capability. Hybrid 6 (and above) and csircd all are |
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currently running daemons that support QS. Hybrid 5 and 2.8.21+CSr servers |
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do not support QS, and will leak server names (and therefore routing |
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information) on splits. |
