[tor-bugs] #25188 [Core Tor/Tor]: Spec bug in formal definition of Document in dir-spec.txt

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#25188: Spec bug in formal definition of Document in dir-spec.txt
------------------------------+----------------------
     Reporter:  witchof0x20   |      Owner:  (none)
         Type:  enhancement   |     Status:  new
     Priority:  Very Low      |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Trivial       |   Keywords:  tor-spec
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 I was attempting to write a parser that reads vote/consensus documents
 using the the formal definition
 [https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n210 here].
 However, I noticed an ambiguity.

 Using only the formal definition, the following:

 {{{
 directory-signature 13241234321 12343234
 -----BEGIN SIGNATURE-----
 00thisisvalidbase64data12345
 -----END SIGNATURE-----
 }}}
 Could be potentially parsed as

 {{{
 Document(
   Item(
     KeywordLine(
       Keyword(KeywordChar+("directory-signature")),
       WS,
       ArgumentChar+("13241234321 12343234"),
       NL
     )
   ),
   Item(
     KeywordLine(
       Keyword(KeywordChar+("-----BEGIN")),
       WS,
       ArgumentChar+("SIGNATURE-----"),
       NL
     )
   ),
   Item(
     KeywordLine(
       Keyword(KeywordChar+("00thisisvalidbase64data12345"))
       WS,
       ArgumentChar+("SIGNATURE-----"),
       NL
     )
   ),
   Item(
     KeywordLine(
       Keyword(KeywordChar+("-----END")),
       WS,
       ArgumentChar+("SIGNATURE-----"),
       NL
     )
   ),
 )
 }}}
 When the correct parsing would be

 {{{
 Document(
   Item(
     KeywordLine(
       Keyword(KeywordChar+("directory-signature")),
       WS,
       ArgumentChar+("13241234321 12343234"),
       NL
     ),
     Object(
       BeginLine(
         "-----BEGIN ",
         Keyword(KeywordChar+("SIGNATURE")),
         "-----",
         NL
       ),
       Base64-encoded-data("00thisisvalidbase64data12345"),
       EndLine(
         "-----END ",
         Keyword(KeywordChar+("SIGNATURE")),
         "-----",
         NL
       ),
     ),
   ),
 )
 }}}
 A potential change to the spec (assuming that keywords will never start
 with "-") that would prevent would be to replace

 {{{
 Keyword = KeywordChar+
 KeywordChar ::= 'A' ... 'Z' | 'a' ... 'z' | '0' ... '9' | '-'
 }}}
 with

 {{{
 Keyword = KeywordStartChar KeywordChar*
 KeywordStartChar ::= 'A' ... 'Z' | 'a' ... 'z' | '0' ... '9'
 KeywordChar ::= 'A' ... 'Z' | 'a' ... 'z' | '0' ... '9' | '-'
 }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25188>
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