git-annex/Backend/GitRemoteAnnex.hs
Joey Hess c7731cdbd9
add Backend.GitRemoteAnnex
Making GITBUNDLE be in the backend list allows those keys to be
hashed to verify, both when git-remote-annex downloads them, and by other
transfers and by git fsck.

GITMANIFEST is not in the backend list, because those keys will never be
stored in .git/annex/objects and can't be verified in any case.

This does mean that git-annex version will include GITBUNDLE in the list
of backends.

Also documented these in backends.mdwn

Sponsored-by: Kevin Mueller on Patreon
2024-05-07 13:54:08 -04:00

76 lines
2.1 KiB
Haskell

{- Backends for git-remote-annex.
-
- GITBUNDLE keys store git bundles
- GITMANIFEST keys store ordered lists of GITBUNDLE keys
-
- Copyright 2024 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
{-# LANGUAGE OverloadedStrings #-}
module Backend.GitRemoteAnnex (
backends,
genGitBundleKey,
genManifestKey,
) where
import Annex.Common
import Types.Key
import Types.Backend
import Utility.Hash
import Utility.Metered
import qualified Backend.Hash as Hash
import qualified Data.ByteString.Short as S
backends :: [Backend]
backends = [gitbundle]
gitbundle :: Backend
gitbundle = Backend
{ backendVariety = GitBundleKey
, genKey = Nothing
-- ^ Not provided because these keys can only be generated by
-- git-remote-annex.
, verifyKeyContent = Just $ Hash.checkKeyChecksum sameCheckSum hash
, verifyKeyContentIncrementally = Just (liftIO . incrementalVerifier)
, canUpgradeKey = Nothing
, fastMigrate = Nothing
, isStableKey = const True
, isCryptographicallySecure = Hash.cryptographicallySecure hash
, isCryptographicallySecureKey = const $ pure $
Hash.cryptographicallySecure hash
}
-- git bundle keys use the sha256 hash.
hash :: Hash.Hash
hash = Hash.SHA2Hash (HashSize 256)
incrementalVerifier :: Key -> IO IncrementalVerifier
incrementalVerifier =
mkIncrementalVerifier sha2_256_context "checksum" . sameCheckSum
sameCheckSum :: Key -> String -> Bool
sameCheckSum key s = s == expected
where
-- The checksum comes after a UUID.
expected = reverse $ takeWhile (/= '-') $ reverse $
decodeBS $ S.fromShort $ fromKey keyName key
genGitBundleKey :: UUID -> RawFilePath -> MeterUpdate -> Annex Key
genGitBundleKey remoteuuid file meterupdate = do
filesize <- liftIO $ getFileSize file
s <- Hash.hashFile hash file meterupdate
return $ mkKey $ \k -> k
{ keyName = S.toShort $ fromUUID remoteuuid <> "-" <> encodeBS s
, keyVariety = GitBundleKey
, keySize = Just filesize
}
genManifestKey :: UUID -> Key
genManifestKey u = mkKey $ \kd -> kd
{ keyName = S.toShort (fromUUID u)
, keyVariety = OtherKey "GITMANIFEST"
}