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diff --git a/doc/serverhide.txt b/doc/serverhide.txt new file mode 100644 index 0000000..83fd850 --- /dev/null +++ b/doc/serverhide.txt @@ -0,0 +1,120 @@ + Server Hide Reference + + $Id$ + + Copyright (c) 2001-2012 by ircd-hybrid team + + ---------------------------------------------------------------------- + + Due to pressures from abusers, the Hybrid developers have created a set of + options to limit what users can and cannot do on the server. Each option + can be enabled or disabled at runtime. + + This document describes the ircd-hybrid implementation of the server hiding + ideas originated by (and credited to) numerous people. + + * LINKS as a file: This option is always enabled. It will generate a + file at a certain interval, defined by the links_delay in ircd.conf, + that contains the current LINKS data. This data is sent to users + whenever a LINKS is requested. Opers will always see the current + server structure. + + The file that the LINKS data is stored in is by default etc/links.txt. + + The benefits of this are that transient splits will not be seen by + users issuing LINKS commands, and if a server is split, users can + still see what other servers are normally available. + + * Flattened LINKS: This option forces every server to look as if it is + connected to the local server. Users will see a flat LINKS tree. + + The benefit to using LINKS flattening is that users cannot get + information on how servers are routed. + + The flatten_links in the serverhide {} block in the ircd.conf controls + this feature. + + As a side effect, all netsplit quit messages will appear to originate + from the local server. + + +--------------------------------------------------------------------+ + | Flattened LINKS is needed for any network that uses the hidden hub | + | option. See below for more details. | + +--------------------------------------------------------------------+ + + + + * Hidden server option: This option will hide the server from a + flattened LINKS list on other servers. Opers will of course see the + true routing of the network. + + This is controlled by the hidden option in ircd.conf. + + +--------------------------------------------------------------------+ + | Technically, this code is a hack. With this option enabled, the | + | server will prepend '(H) ' to the server info field when | + | connecting to other servers. Other servers must understand that | + | the (H) means hidden. | + +--------------------------------------------------------------------+ + + * The allow_hidden option is needed to allow servers to use the hidden + server option described above. + + * The hide_servers option forces the server to not be shown when a user + issues WHOIS and other commands which may show what server a user is + on. + + Local user counts, as normally displayed in LUSERS, USERS, and the 255 + numeric, will be shown with the same values as the global counts. + Displaying it this way will help protect servers and avoid breaking + scripts that depend on the 265 and 266 numerics on connect. + + To be effective, this option must be used network wide. + + * The disable_remote_commands option takes care of most of the remaining + issues. These include, for example, ADMIN some.hub.server, VERSION + someuser, and similar commands. A server with this option enabled will + only prevent local users from issuing remote commands. Remote users + will not be affected. + + Remote WHOIS is not blocked. It is, however, restricted to only + querying WHOIS nick nick. The ircd will disregard the server parameter + and always use queried nick. + + * All server modes appear to originate from the server you are using. + This feature is not tunable; and opers also do not see the real server + setting the mode. + + Each item is briefly described in the serverhide {} block in ircd.conf. + + ---------------------------------------------------------------------- + +Using Non-QS Compliant Hubs + + The flattened LINKS option will, as a side effect, display all user QUITs + due to network splits in the following format: + + :user QUIT :*.net *.split + + This works extremely well as long as all servers on your network are + compliant with the QS capability, which sends a single SQUIT to the + network when a server (or tree of servers) splits. All quit messages are + generated on the local server. Certain older servers do not have this + ability, and as such will generate their own quit messages for users who + left because of the split. This can cause leaks in the hub server names + and the structure of the network. + + A quick example is the following network structure: + + servA(Hyb7) --- hubA(nonQS) --- servB(not-important) + + When servB splits from hubA, hubA will generate a QUIT command for every + user on servB (and anything behind servB). Since the QUIT message was not + created on your server, with server hiding enabled, the QUIT message will + contain the real server names. + + The only way to prevent this leak on a network is to only use hubs + supporting the QS capability. Hybrid 6, Hybrid 7, and csircd all are + currently running daemons that support QS. Hybrid 5 and 2.8.21+CSr servers + do not support QS, and will leak server names (and therefore routing + information) on splits. |