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diff --git a/doc/torrc_format.txt b/doc/torrc_format.txt new file mode 100644 index 0000000000..7a809901d9 --- /dev/null +++ b/doc/torrc_format.txt @@ -0,0 +1,205 @@ + +This document specifies the current format and semantics of the torrc +file, as of July 2015. Note that we make no guarantee about the +stability of this format. If you write something designed for strict +compatibility with this document, please expect us to break it sooner or +later. + +Yes, some of this is quite stupid. My goal here is to explain what it +does, not what it should do. + + - Nick + + + +1. File Syntax + + ; The syntax here is defined an Augmented Backus-Naur form, as + ; specified in RFC5234. + + ; A file is interpreted as every Entry in the file, in order. + TorrcFile = *Line + + Line = BlankLine / Entry + + BlankLine = *WSP OptComment LF + BlankLine =/ *WSP LF + + OptComment = [ Comment ] + + Comment = "#" *NonLF + + ; Each Entry is interpreted as an optional "Magic" flag, a key, and a + ; value. + Entry = *WSP [ Magic ] Key 1*(1*WSP / "\" NL *WSP) Val LF + Entry =/ *WSP [ Magic ] Key *( *WSP / "\" NL *WSP) LF + + Magic = "+" / "/" + + ; Keys are always specified verbatim. They are case insensitive. It + ; is an error to specify a key that Tor does not recognize. + Key = 1*KC + + ; Sadly, every kind of value is decoded differently... + Val = QuotedVal / ContinuedVal / PlainVal + + ; The text of a PlainVal is the text of its PVBody portion, + ; plus the optional trailing backslash. + PlainVal = PVBody [ "\" ] *WSP OptComment + + ; Note that a PVBody is copied verbatim. Slashes are included + ; verbatim. No changes are made. Note that a body may be empty. + PVBody = * (VC / "\" NonLF ) + + ; The text of a ContinuedVal is the text of each of its PVBody + ; sub-elements, in order, concatenated. + ContinuedVal = CVal1 *CVal2 CVal3 + + CVal1 = PVBody "\" LF + CVal2 = PVBody ( "\" LF / Comment LF ) + CVal3 = PVBody + + ; The text of a QuotedVal is decoded as if it were a C string. + QuotedVal = DQ QVBody DQ *WSP Comment + + QVBody = QC + QVBody =/ "\" ( "n" / "r" / "t" / "\" / "'" / DQUOTE ) + QVBOdy =/ "\" ( "x" 2HEXDIG / 1*3OCTDIG ) + + ; Anything besides NUL and LF + NonLF = %x01-%x09 / %x0b - %xff + + OCTDIG = '0' - '7' + + KC = Any character except an isspace() character or '#' or NUL + VC = Any character except '\\', '\n', '#', or NUL + QC = Any character except '\n', '\\', '\"', or NUL + +2. Mid-level Semantics + + + There are four configuration "domains", from lowest to highest priority: + + * Built-in defaults + * The "torrc_defaults" file, if any + * The "torrc" file, if any + * Arguments provided on the command line, if any. + + Normally, values from high-priority domains override low-priority + domains, but see 'magic' below. + + Configuration keys fall into three categories: singletons, lists, and + groups. + + A singleton key may appear at most once in any domain. Its + corresponding value is equal to its value in the highest-priority + domain in which it occurs. + + A list key may appear any number of times in a domain. By default, + its corresponding value is equal to all of the values specified for + it in the highest-priority domain in which it appears. (See 'magic' + below). + + A group key may appear any number of times in a domain. It is + associated with a number of other keys in the same group. The + relative positions of entries with the keys in a single group + matters, but entries with keys not in the group may be freely + interspersed. By default, the group has a value equal to all keys + and values it contains, from the highest-priority domain in which any + of its keys occurs. + + Magic: + + If the '/' flag is specified for an entry, it sets the value for + that entry to an empty list. (This will cause a higher-priority + domain to clear a list from a lower-priority domain, without + actually adding any entries.) + + If the '+' flag is specified for the first entry in a list or a + group that appears in a given domain, that list or group is + appended to the list or group from the next-lowest-priority + domain, rather than replacing it. + +3. High-level semantics + + There are further constraints on the values that each entry can take. + These constraints are out-of-scope for this document. + +4. Examples + + (Indentation is removed in this section, to avoid confusion.) + +4.1. Syntax examples + +# Here is a simple configuration entry. The key is "Foo"; the value is +# "Bar" + +Foo Bar + +# A configuration entry can have spaces in its value, as below. Here the +# key is "Foo" and the value is "Bar Baz" +Foo Bar Baz + +# This configuration entry has space at the end of the line, but those +# spaces don't count, so the key and value are still "Foo" and "Bar Baz" +Foo Bar Baz + +# There can be an escaped newline between the value and the key. This +# is another way to say key="Hello", value="World" +Hello\ +World + +# In regular entries of this kind, you can have a comment at the end of +# the line, either with a space before it or not. Each of these is a +# different spelling of key="Hello", value="World" + +Hello World #today +Hello World#tomorrow + +# One way to encode a complex entry is as a C string. This is the same +# as key="Hello", value="World!" +Hello "World!" + +# The string can contain the usual set of C escapes. This entry has +# key="Hello", and value="\"World\"\nand\nuniverse" +Hello "\"World\"\nand\nuniverse" + +# And now we get to the more-or-less awful part. +# +# Multi-line entries ending with a backslash on each line aren't so +# bad. The backslash is removed, and everything else is included +# verbatim. So this entry has key="Hello" and value="Worldandfriends" +Hello\ +World\ +and\ +friends + +# Backslashes in the middle of a line are included as-is. The key of +# this one is "Too" and the value is "Many\\Backsl\ashes here" (with +# backslashes in that last string as-is) +Too \ +Many\\\ +Backsl\ashes \\ +here + +# And here's the really yucky part. If a comment appears in a multi-line +# entry, the entry is still able to continue on the next line, as in the +# following, where the key is "This" and the value is +# "entry and some are silly" +This entry \ + # has comments \ + and some \ + are # generally \ + silly + +# But you can also write that without the backslashes at the end of the +# comment lines. That is to say, this entry is exactly the same as the +# one above! +This entry \ + # has comments + and some \ + are # generally + silly + + + |