IPvFuture host literals with uppercase `V`, a multi-digit version or `:` are rejected

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
82/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
haskell
Domain
backend-api-design

Research direction

The parser and character predicate are in Network/URI.hs; start by reading the ipvFuture definition and its surrounding URI parser code. Check the existing parser tests, then cover uppercase V, multiple version digits, and : in the address. Done when isURI, parseURI, and parseURIReference accept the reported valid forms.

Written by the indexing model from the issue text.

Description

The parser for IPvFuture host literals accepts less than the RFC 3986 §3.2.2 rule

IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )

>>> isURI "http://[v1.a]/"
True
>>> isURI "http://[v1.a:b]/"
False
>>> isURI "http://[v1F.a]/"
False
>>> isURI "http://[V1.a]/"
False

All four should be True; parseURI and parseURIReference return Nothing for the last three.

The code is in Network/URI.hs:

ipvFuture =
    do  { _ <- char 'v'
        ; h <- hexDigitChar
        ; _ <- char '.'
        ; a <- many1 (satisfy isIpvFutureChar)
        ; return $ 'v':h:'.':a
        }

isIpvFutureChar c = isUnreserved c || isSubDelims c || (c==';')
  • (c==';') is where the grammar has ":". ; is already a sub-delim, so this looks like a typo.
  • The version is a single hexDigitChar, the grammar has 1*HEXDIG.
  • Only lowercase v is accepted. The RFC text says "an IP-literal that starts with "v" (case-insensitive)".

A possible fix:

 ipvFuture =
-    do  { _ <- char 'v'
-        ; h <- hexDigitChar
+    do  { v <- char 'v' <|> char 'V'
+        ; h <- many1 hexDigitChar
         ; _ <- char '.'
         ; a <- many1 (satisfy isIpvFutureChar)
-        ; return $ 'v':h:'.':a
+        ; return $ v:h ++ '.':a
         }
 
 isIpvFutureChar :: Char -> Bool
-isIpvFutureChar c = isUnreserved c || isSubDelims c || (c==';')
+isIpvFutureChar c = isUnreserved c || isSubDelims c || (c==':')

No IPvFuture format is in use as far as I know, so this is low priority.

Tested with network-uri 2.6.4.2 and current master, GHC 9.6.7.

Dominant language
Haskell
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