partially complete gcrypt remote (local send done; rest not)

This is a git-remote-gcrypt encrypted special remote. Only sending files
in to the remote works, and only for local repositories.

Most of the work so far has involved making initremote work. A particular
problem is that remote setup in this case needs to generate its own uuid,
derivied from the gcrypt-id. That required some larger changes in the code
to support.

For ssh remotes, this will probably just reuse Remote.Rsync's code, so
should be easy enough. And for downloading from a web remote, I will need
to factor out the part of Remote.Git that does that.

One particular thing that will need work is supporting hot-swapping a local
gcrypt remote. I think it needs to store the gcrypt-id in the git config of the
local remote, so that it can check it every time, and compare with the
cached annex-uuid for the remote. If there is a mismatch, it can change
both the cached annex-uuid and the gcrypt-id. That should work, and I laid
some groundwork for it by already reading the remote's config when it's
local. (Also needed for other reasons.)

This commit was sponsored by Daniel Callahan.

Remote/GCrypt.hs

@@ -0,0 +1,164 @@
+{- git remotes encrypted using git-remote-gcrypt
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Remote.GCrypt (remote, gen) where
+
+import qualified Data.Map as M
+
+import Common.Annex
+import Types.Remote
+import Types.GitConfig
+import Types.Crypto
+import qualified Git
+import qualified Git.Command
+import qualified Git.Config
+import qualified Git.GCrypt
+import qualified Git.Types as Git ()
+import qualified Annex.Branch
+import qualified Annex.Content
+import Config
+import Config.Cost
+import Remote.Helper.Git
+import Remote.Helper.Encryptable
+import Utility.Metered
+import Crypto
+import Annex.UUID
+
+remote :: RemoteType
+remote = RemoteType {
+	typename = "gcrypt",
+	-- Remote.Git takes care of enumerating gcrypt remotes too,
+	-- and will call our gen on them.
+	enumerate = return [],
+	generate = gen,
+	setup = gCryptSetup
+}
+
+gen :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> Annex Remote
+gen gcryptr u c gc = do
+	g <- gitRepo
+	-- get underlying git repo with real path, not gcrypt path
+	r <- liftIO $ Git.GCrypt.encryptedRepo g gcryptr
+	let r' = r { Git.remoteName = Git.remoteName gcryptr }
+	-- read config of underlying repo if it's local
+	r'' <- if Git.repoIsLocalUnknown r'
+		then liftIO $ catchDefaultIO r' $ Git.Config.read r'
+		else return r'
+	gen' r'' u c gc
+
+gen' :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> Annex Remote
+gen' r u c gc = new <$> remoteCost gc defcst
+  where
+	defcst = if repoCheap r then nearlyCheapRemoteCost else expensiveRemoteCost
+	new cst = encryptableRemote c
+		(store this)
+		(retrieve this)
+		this
+	  where
+		this = Remote 
+			{ uuid = u
+			, cost = cst
+			, name = Git.repoDescribe r
+			, storeKey = \_ _ _ -> noCrypto
+			, retrieveKeyFile = \_ _ _ _ -> noCrypto
+			, retrieveKeyFileCheap = \_ _ -> return False
+			, removeKey = remove
+			, hasKey = checkPresent this
+			, hasKeyCheap = repoCheap r
+			, whereisKey = Nothing
+			, config = M.empty
+			, localpath = localpathCalc r
+			, repo = r
+			, gitconfig = gc { remoteGitConfig = Just $ extractGitConfig r }
+			, readonly = Git.repoIsHttp r
+			, globallyAvailable = globallyAvailableCalc r
+			, remotetype = remote
+			}
+
+noCrypto :: Annex a
+noCrypto = error "cannot use gcrypt remote without encryption enabled"
+
+gCryptSetup :: Maybe UUID -> RemoteConfig -> Annex (RemoteConfig, UUID)
+gCryptSetup mu c = go $ M.lookup "gitrepo" c
+  where
+	remotename = fromJust (M.lookup "name" c)
+  	go Nothing = error "Specify gitrepo="
+	go (Just gitrepo) = do
+		c' <- encryptionSetup c
+		inRepo $ Git.Command.run 
+			[ Params "remote add"
+			, Param remotename
+			, Param $ Git.GCrypt.urlPrefix ++ gitrepo
+			]
+
+		{- Configure gcrypt to use the same list of keyids that
+		 - were passed to initremote, unless shared encryption
+		 - was used. -}
+		case extractCipher c' of
+			Nothing -> noCrypto
+			Just (EncryptedCipher _ _ (KeyIds { keyIds = ks})) ->
+				setConfig (ConfigKey $ Git.GCrypt.remoteParticipantConfigKey remotename) (unwords ks)
+			_ -> noop
+
+		{- Run a git fetch and a push to the git repo in order to get
+		 - its gcrypt-id set up, so that later git annex commands
+		 - will use the remote as a ggcrypt remote. The fetch is
+		 - needed if the repo already exists; the push is needed
+		 - if the repo has not yet been initialized by gcrypt. -}
+		void $ inRepo $ Git.Command.runBool
+			[ Param "fetch"
+			, Param remotename
+			]
+		void $ inRepo $ Git.Command.runBool
+			[ Param "push"
+			, Param remotename
+			, Param $ show $ Annex.Branch.fullname
+			]
+		g <- inRepo Git.Config.reRead
+		case Git.GCrypt.remoteRepoId g (Just remotename) of
+			Nothing -> error "unable to determine gcrypt-id of remote"
+			Just v -> do
+				let u = genUUIDInNameSpace gCryptNameSpace v
+				if Just u == mu || mu == Nothing
+					then return (c', u)
+					else error "uuid mismatch"
+
+store :: Remote -> (Cipher, Key) -> Key -> MeterUpdate -> Annex Bool
+store r (cipher, enck) k p
+	| not $ Git.repoIsUrl (repo r) = guardUsable (repo r) False $
+		sendwith $ \meterupdate h -> do
+			createDirectoryIfMissing True $ parentDir dest
+			readBytes (meteredWriteFile meterupdate dest) h
+			return True
+	| Git.repoIsSsh (repo r) = sendwith $ \h -> undefined
+	| otherwise = error "storing on non-ssh remote repo not supported"
+  where
+	dest = gCryptLocation r enck
+  	sendwith a = metered (Just p) k $ \meterupdate ->
+		Annex.Content.sendAnnex k noop $ \src ->
+			liftIO $ catchBoolIO $
+				encrypt (getGpgEncParams r) cipher (feedFile src) (a meterupdate)
+
+retrieve :: Remote -> (Cipher, Key) -> Key -> FilePath -> MeterUpdate -> Annex Bool
+retrieve r (cipher, enck) k d p = undefined
+
+remove :: Key -> Annex Bool
+remove k = undefined
+
+checkPresent :: Remote -> Key -> Annex (Either String Bool)
+checkPresent r k
+	| not $ Git.repoIsUrl (repo r) =
+		guardUsable (repo r) unknown $
+			liftIO $ catchDefaultIO unknown $
+				Right <$> doesFileExist (gCryptLocation r k)
+	| Git.repoIsSsh (repo r) = undefined
+	| otherwise = error "storing on non-ssh remote repo not supported"
+  where
+	unknown = Left $ "unable to check " ++ Git.repoDescribe (repo r) ++ show (repo r)
+
+gCryptLocation :: Remote -> Key -> FilePath
+gCryptLocation r key = Git.repoLocation (repo r) </> annexLocation key hashDirLower