diff options
Diffstat (limited to 'Types/Key.hs')
| -rw-r--r-- | Types/Key.hs | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/Types/Key.hs b/Types/Key.hs index 23648dd03..d4a4d3728 100644 --- a/Types/Key.hs +++ b/Types/Key.hs @@ -1,6 +1,6 @@ {- git-annex Key data type - - - Copyright 2011-2016 Joey Hess <id@joeyh.name> + - Copyright 2011-2017 Joey Hess <id@joeyh.name> - - Licensed under the GNU GPL version 3 or higher. -} @@ -104,7 +104,7 @@ file2key s _ -> Nothing findfields (c:v) (Just k) - | c == fieldSep = Just $ k { keyName = v } + | c == fieldSep = addkeyname k v | otherwise = sepfield k v $ addfield c findfields _ v = v @@ -134,6 +134,31 @@ file2key s _ -> Nothing addfield _ _ _ = Nothing + addkeyname k v + | validKeyName k v = Just $ k { keyName = v } + | otherwise = Nothing + +{- A key with a backend ending in "E" is an extension preserving key, + - using some hash. + - + - The length of the extension is limited in order to mitigate against + - SHA1 collision attacks (specifically, chosen-prefix attacks). + - In such an attack, the extension of the key could be made to contain + - the collision generation data, with the result that a signed git commit + - including such keys would not be secure. + - + - The maximum extension length ever generated for such a key was 8 + - characters; 20 is used here to give a little future wiggle-room. + - The SHA1 common-prefix attack used 128 bytes of data. + - + - This code is here, and not in Backend.Hash (where it really belongs) + - so that file2key can check it whenever a Key is constructed. + -} +validKeyName :: Key -> String -> Bool +validKeyName k v + | end (keyBackendName k) == "E" = length (takeExtensions v) <= 20 + | otherwise = True + instance ToJSON Key where toJSON = toJSON . key2file |