diff options
author | Joey Hess <joeyh@joeyh.name> | 2016-12-09 13:34:00 -0400 |
---|---|---|
committer | Joey Hess <joeyh@joeyh.name> | 2016-12-09 13:34:32 -0400 |
commit | 6aac10c5215e822b2252897b777b41b97abbfb33 (patch) | |
tree | 27e4dccea180a5f44e9fbc96977ba08a9566de9f | |
parent | 2ae57936186caad6c025184104efb2bb9d28571a (diff) |
git-annex-shell, remotedaemon, git remote: Fix some memory DOS attacks.
The attacker could just send a very lot of data, with no \n and it would
all be buffered in memory until the kernel killed git-annex or perhaps OOM
killed some other more valuable process.
This is a low impact security hole, only affecting communication between
local git-annex and git-annex-shell on the remote system. (With either
able to be the attacker). Only those with the right ssh key can do it. And,
there are probably lots of ways to construct git repositories that make git
use a lot of memory in various ways, which would have similar impact as
this attack.
The fix in P2P/IO.hs would have been higher impact, if it had made it to a
released version, since it would have allowed DOSing the tor hidden
service without needing to authenticate.
(The LockContent and NotifyChanges instances may not be really
exploitable; since the line is read and ignored, it probably gets read
lazily and does not end up staying buffered in memory.)
-rw-r--r-- | CHANGELOG | 1 | ||||
-rw-r--r-- | Command/LockContent.hs | 3 | ||||
-rw-r--r-- | Command/NotifyChanges.hs | 3 | ||||
-rw-r--r-- | Command/TransferInfo.hs | 3 | ||||
-rw-r--r-- | P2P/IO.hs | 5 | ||||
-rw-r--r-- | Remote/Git.hs | 5 | ||||
-rw-r--r-- | RemoteDaemon/Transport/Ssh.hs | 4 | ||||
-rw-r--r-- | Utility/SimpleProtocol.hs | 44 |
8 files changed, 49 insertions, 19 deletions
@@ -23,6 +23,7 @@ git-annex (6.20161119) UNRELEASED; urgency=medium * rekey: Added --batch mode. * add: Stage modified non-large files when running in indirect mode. (This was already done in v6 mode and direct mode.) + * git-annex-shell, remotedaemon, git remote: Fix some memory DOS attacks. -- Joey Hess <id@joeyh.name> Mon, 21 Nov 2016 11:27:50 -0400 diff --git a/Command/LockContent.hs b/Command/LockContent.hs index 35342c529..202ba20d1 100644 --- a/Command/LockContent.hs +++ b/Command/LockContent.hs @@ -10,6 +10,7 @@ module Command.LockContent where import Command import Annex.Content import Remote.Helper.Ssh (contentLockedMarker) +import Utility.SimpleProtocol cmd :: Command cmd = noCommit $ @@ -37,7 +38,7 @@ start [ks] = do ( liftIO $ do putStrLn contentLockedMarker hFlush stdout - _ <- getLine + _ <- getProtocolLine stdin return True , return False ) diff --git a/Command/NotifyChanges.hs b/Command/NotifyChanges.hs index f1c149d54..bb9b10eee 100644 --- a/Command/NotifyChanges.hs +++ b/Command/NotifyChanges.hs @@ -13,6 +13,7 @@ import Utility.DirWatcher.Types import qualified Git import Git.Sha import RemoteDaemon.Transport.Ssh.Types +import Utility.SimpleProtocol import Control.Concurrent import Control.Concurrent.Async @@ -52,7 +53,7 @@ start = do -- No messages need to be received from the caller, -- but when it closes the connection, notice and terminate. - let receiver = forever $ void getLine + let receiver = forever $ void $ getProtocolLine stdin void $ liftIO $ concurrently sender receiver stop diff --git a/Command/TransferInfo.hs b/Command/TransferInfo.hs index 6870c84f0..1db633484 100644 --- a/Command/TransferInfo.hs +++ b/Command/TransferInfo.hs @@ -13,6 +13,7 @@ import Types.Transfer import Logs.Transfer import qualified CmdLine.GitAnnexShell.Fields as Fields import Utility.Metered +import Utility.SimpleProtocol cmd :: Command cmd = noCommit $ @@ -62,4 +63,4 @@ start (k:[]) = do start _ = giveup "wrong number of parameters" readUpdate :: IO (Maybe Integer) -readUpdate = readish <$> getLine +readUpdate = maybe Nothing readish <$> getProtocolLine stdin @@ -102,10 +102,11 @@ runNet conn runner f = case f of Left e -> return (Left (show e)) Right () -> runner next ReceiveMessage next -> do - v <- liftIO $ tryNonAsync $ hGetLine (connIhdl conn) + v <- liftIO $ tryNonAsync $ getProtocolLine (connIhdl conn) case v of Left e -> return (Left (show e)) - Right l -> case parseMessage l of + Right Nothing -> return (Left "protocol error") + Right (Just l) -> case parseMessage l of Just m -> runner (next m) Nothing -> runner $ do let e = ERROR $ "protocol parse error: " ++ show l diff --git a/Remote/Git.hs b/Remote/Git.hs index 37a9f48b3..5eb6fbc9e 100644 --- a/Remote/Git.hs +++ b/Remote/Git.hs @@ -45,6 +45,7 @@ import Utility.CopyFile #endif import Utility.Env import Utility.Batch +import Utility.SimpleProtocol import Remote.Helper.Git import Remote.Helper.Messages import qualified Remote.Helper.Ssh as Ssh @@ -390,7 +391,7 @@ lockKey r key callback , std_out = CreatePipe , std_err = UseHandle nullh } - v <- liftIO $ tryIO $ hGetLine hout + v <- liftIO $ tryIO $ getProtocolLine hout let signaldone = void $ tryNonAsync $ liftIO $ mapM_ tryNonAsync [ hPutStrLn hout "" , hFlush hout @@ -408,7 +409,7 @@ lockKey r key callback void $ waitForProcess p failedlock Right l - | l == Ssh.contentLockedMarker -> bracket_ + | l == Just Ssh.contentLockedMarker -> bracket_ noop signaldone (withVerifiedCopy LockedCopy r checkexited callback) diff --git a/RemoteDaemon/Transport/Ssh.hs b/RemoteDaemon/Transport/Ssh.hs index 73c88054c..205165062 100644 --- a/RemoteDaemon/Transport/Ssh.hs +++ b/RemoteDaemon/Transport/Ssh.hs @@ -68,8 +68,8 @@ transportUsingCmd' cmd params (RemoteRepo r _) url transporthandle ichan ochan = send (DONESYNCING url ok) handlestdout fromh = do - l <- hGetLine fromh - case parseMessage l of + ml <- getProtocolLine fromh + case parseMessage =<< ml of Just SshRemote.READY -> do send (CONNECTED url) handlestdout fromh diff --git a/Utility/SimpleProtocol.hs b/Utility/SimpleProtocol.hs index 473129218..7ab3c8c77 100644 --- a/Utility/SimpleProtocol.hs +++ b/Utility/SimpleProtocol.hs @@ -1,6 +1,6 @@ {- Simple line-based protocols. - - - Copyright 2013-2014 Joey Hess <id@joeyh.name> + - Copyright 2013-2016 Joey Hess <id@joeyh.name> - - License: BSD-2-clause -} @@ -20,6 +20,7 @@ module Utility.SimpleProtocol ( parse2, parse3, dupIoHandles, + getProtocolLine, ) where import Data.Char @@ -48,6 +49,16 @@ class Serializable a where serialize :: a -> String deserialize :: String -> Maybe a +instance Serializable [Char] where + serialize = id + deserialize = Just + +instance Serializable ExitCode where + serialize ExitSuccess = "0" + serialize (ExitFailure n) = show n + deserialize "0" = Just ExitSuccess + deserialize s = ExitFailure <$> readish s + {- Parsing the parameters of messages. Using the right parseN ensures - that the string is split into exactly the requested number of words, - which allows the last parameter of a message to contain arbitrary @@ -93,12 +104,25 @@ dupIoHandles = do stderr `hDuplicateTo` stdout return (readh, writeh) -instance Serializable [Char] where - serialize = id - deserialize = Just - -instance Serializable ExitCode where - serialize ExitSuccess = "0" - serialize (ExitFailure n) = show n - deserialize "0" = Just ExitSuccess - deserialize s = ExitFailure <$> readish s +{- Reads a line, but to avoid super-long lines eating memory, returns + - Nothing if 32 kb have been read without seeing a '\n' + - + - If there is a '\r' before the '\n', it is removed, to support + - systems using "\r\n" at ends of lines + - + - This implementation is not super efficient, but as long as the Handle + - supports buffering, it avoids reading a character at a time at the + - syscall level. + -} +getProtocolLine :: Handle -> IO (Maybe String) +getProtocolLine h = go (32768 :: Int) [] + where + go 0 _ = return Nothing + go n l = do + c <- hGetChar h + if c == '\n' + then return $ Just $ reverse $ + case l of + ('\r':rest) -> rest + _ -> l + else go (n-1) (c:l) |