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102 lines
3.4 KiB
Haskell
102 lines
3.4 KiB
Haskell
{- git-annex VURL backend -- like URL, but with hash-based verification
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- of transfers between git-annex repositories.
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-
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- Copyright 2024 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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module Backend.VURL (
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backends,
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) where
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import Annex.Common
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import Types.Key
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import Types.Backend
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import Logs.EquivilantKeys
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import Backend.Variety
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import Backend.Hash (descChecksum)
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import Utility.Hash
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import Backend.VURL.Utilities
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backends :: [Backend]
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backends = [backendVURL]
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backendVURL :: Backend
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backendVURL = Backend
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{ backendVariety = VURLKey
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, genKey = Nothing
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, verifyKeyContent = Just $ \k f -> do
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equivkeys k >>= \case
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-- Normally there will always be an key
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-- recorded when a VURL's content is available,
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-- because downloading the content from the web in
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-- the first place records one.
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[] -> return False
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eks -> do
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let check ek = getbackend ek >>= \case
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Nothing -> pure False
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Just b -> case verifyKeyContent b of
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Just verify -> verify ek f
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Nothing -> pure False
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anyM check eks
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, verifyKeyContentIncrementally = Just $ \k -> do
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-- Run incremental verifiers for each equivalent key together,
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-- and see if any of them succeed.
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eks <- equivkeys k
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let get = \ek -> getbackend ek >>= \case
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Nothing -> pure Nothing
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Just b -> case verifyKeyContentIncrementally b of
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Nothing -> pure Nothing
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Just va -> Just <$> va ek
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l <- catMaybes <$> forM eks get
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return $ IncrementalVerifier
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{ updateIncrementalVerifier = \s ->
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forM_ l $ flip updateIncrementalVerifier s
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-- If there are no equivalent keys recorded somehow,
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-- or if none of them support incremental verification,
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-- this will return Nothing, which indicates that
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-- incremental verification was not able to be
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-- performed.
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, finalizeIncrementalVerifier = do
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r <- forM l finalizeIncrementalVerifier
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return $ case catMaybes r of
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[] -> Nothing
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r' -> Just (or r')
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, unableIncrementalVerifier =
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forM_ l unableIncrementalVerifier
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, positionIncrementalVerifier =
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getM positionIncrementalVerifier l
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, descIncrementalVerifier = descChecksum
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}
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, canUpgradeKey = Nothing
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, fastMigrate = Just migrateFromVURLToURL
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-- Even if a hash is recorded on initial download from the web and
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-- is used to verify every subsequent transfer including other
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-- downloads from the web, in a split-brain situation there
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-- can be more than one hash and different versions of the content.
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-- So the content is not stable.
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, isStableKey = const False
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-- Not all keys using this backend are necessarily
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-- cryptographically secure.
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, isCryptographicallySecure = False
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-- A key is secure when all recorded equivalent keys are.
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-- If there are none recorded yet, it's secure because when
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-- downloaded, an equivalent key that is cryptographically secure
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-- will be constructed then.
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, isCryptographicallySecureKey = \k ->
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equivkeys k >>= \case
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[] -> return True
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l -> do
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let check ek = getbackend ek >>= \case
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Nothing -> pure False
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Just b -> isCryptographicallySecureKey b ek
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allM check l
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}
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where
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equivkeys k = filter allowedequiv <$> getEquivilantKeys k
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-- Don't allow using VURL keys as equivalent keys, because that
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-- could let a crafted git-annex branch cause an infinite loop.
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allowedequiv ek = fromKey keyVariety ek /= VURLKey
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varietymap = makeVarietyMap regularBackendList
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getbackend ek = maybeLookupBackendVarietyMap (fromKey keyVariety ek) varietymap
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