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diff --git a/doc/spec/proposals/170-user-path-config.txt b/doc/spec/proposals/170-user-path-config.txt new file mode 100644 index 000000000..fa74c76f7 --- /dev/null +++ b/doc/spec/proposals/170-user-path-config.txt @@ -0,0 +1,95 @@ +Title: Configuration options regarding circuit building +Filename: 170-user-path-config.txt +Author: Sebastian Hahn +Created: 01-March-2010 +Status: Draft + +Overview: + + This document outlines how Tor handles the user configuration + options to influence the circuit building process. + +Motivation: + + Tor's treatment of the configuration *Nodes options was surprising + to many users, and quite a few conspiracy theories have crept up. We + should update our specification and code to better describe and + communicate what is going during circuit building, and how we're + honoring configuration. So far, we've been tracking a bugreport + about this behaviour ( + https://bugs.torproject.org/flyspray/index.php?do=details&id=1090 ) + and Nick replied in a thread on or-talk ( + http://archives.seul.org/or/talk/Feb-2010/msg00117.html ). + + This proposal tries to document our intention for those configuration + options. + +Design: + + Five configuration options are available to users to influence Tor's + circuit building. EntryNodes and ExitNodes define a list of nodes + that are for the Entry/Exit position in all circuits. ExcludeNodes + is a list of nodes that are used for no circuit, and + ExcludeExitNodes is a list of nodes that aren't used as the last + hop. StrictNodes defines Tor's behaviour in case of a conflict, for + example when a node that is excluded is the only available + introduction point. Setting StrictNodes to 1 breaks Tor's + functionality in that case, and it will refuse to build such a + circuit. + + Neither Nick's email nor bug 1090 have clear suggestions how we + should behave in each case, so I tried to come up with something + that made sense to me. + +Security implications: + + Deviating from normal circuit building can break one's anonymity, so + the documentation of the above option should contain a warning to + make users aware of the pitfalls. + +Specification: + + It is proposed that the "User configuration" part of path-spec + (section 2.2.2) be replaced with this: + + Users can alter the default behavior for path selection with + configuration options. In case of conflicts (excluding and requiring + the same node) the "StrictNodes" option is used to determine + behaviour. If a nodes is both excluded and required via a + configuration option, the exclusion takes preference. + + - If "ExitNodes" is provided, then every request requires an exit + node on the ExitNodes list. If a request is supported by no nodes + on that list, and "StrictNodes" is false, then Tor treats that + request as if ExitNodes were not provided. + + - "EntryNodes" behaves analogously. + + - If "ExcludeNodes" is provided, then no circuit uses any of the + nodes listed. If a circuit requires an excluded node to be used, + and "StrictNodes" is false, then Tor uses the node in that + position while not using any other of the excluded nodes. + + - If "ExcludeExitNodes" is provided, then Tor will not use the nodes + listed for the exit position in a circuit. If a circuit requires + an excluded node to be used in the exit position and "StrictNodes" + is false, then Tor builds that circuit as if ExcludeExitNodes were + not provided. + + - If a user tries to connect to or resolve a hostname of the form + <target>.<servername>.exit and the "AllowDotExit" configuration + option is set to 1, the request is rewritten to a request for + <target>, and the request is only supported by the exit whose + nickname or fingerprint is <servername>. If "AllowDotExit" is set + to 0 (default), any request for <anything>.exit is denied. + + - When any of the *Nodes settings are changed, all circuits are + expired immediately, to prevent a situation where a previously + built circuit is used even though some of its nodes are now + excluded. + + +Compatibility: + + The old Strict*Nodes options are deprecated, and the StrictNodes + option is new. Tor users may need to update their configuration file. |