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|
{- git-annex assistant thread to listen for incoming pairing traffic
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.Threads.PairListener where
import Assistant.Common
import Assistant.Pairing
import Assistant.Pairing.Network
import Assistant.Pairing.MakeRemote
import Assistant.WebApp (UrlRenderer)
import Assistant.WebApp.Types
import Assistant.Alert
import Assistant.DaemonStatus
import Utility.ThreadScheduler
import Utility.Format
import Git
import Network.Multicast
import Network.Socket
import qualified Data.Text as T
import Data.Char
pairListenerThread :: UrlRenderer -> NamedThread
pairListenerThread urlrenderer = namedThread "PairListener" $ do
listener <- asIO1 $ go [] []
liftIO $ withSocketsDo $
runEvery (Seconds 60) $ void $ tryIO $
listener =<< getsock
where
{- Note this can crash if there's no network interface,
- or only one like lo that doesn't support multicast. -}
getsock = multicastReceiver (multicastAddress $ IPv4Addr undefined) pairingPort
go reqs cache sock = liftIO (getmsg sock []) >>= \msg -> case readish msg of
Nothing -> go reqs cache sock
Just m -> do
debug ["received", show msg]
sane <- checkSane msg
(pip, verified) <- verificationCheck m
=<< (pairingInProgress <$> getDaemonStatus)
let wrongstage = maybe False (\p -> pairMsgStage m <= inProgressPairStage p) pip
let fromus = maybe False (\p -> remoteSshPubKey (pairMsgData m) == remoteSshPubKey (inProgressPairData p)) pip
case (wrongstage, fromus, sane, pairMsgStage m) of
(_, True, _, _) -> do
debug ["ignoring message that looped back"]
go reqs cache sock
(_, _, False, _) -> go reqs cache sock
-- PairReq starts a pairing process, so a
-- new one is always heeded, even if
-- some other pairing is in process.
(_, _, _, PairReq) -> if m `elem` reqs
then go reqs (invalidateCache m cache) sock
else do
pairReqReceived verified urlrenderer m
go (m:take 10 reqs) (invalidateCache m cache) sock
(True, _, _, _) -> do
debug
["ignoring out of order message"
, show (pairMsgStage m)
, "expected"
, show (succ . inProgressPairStage <$> pip)
]
go reqs cache sock
(_, _, _, PairAck) -> do
cache' <- pairAckReceived verified pip m cache
go reqs cache' sock
(_,_ , _, PairDone) -> do
pairDoneReceived verified pip m
go reqs cache sock
{- As well as verifying the message using the shared secret,
- check its UUID against the UUID we have stored. If
- they're the same, someone is sending bogus messages,
- which could be an attempt to brute force the shared secret. -}
verificationCheck _ Nothing = return (Nothing, False)
verificationCheck m (Just pip)
| not verified && sameuuid = do
liftAnnex $ warning
"detected possible pairing brute force attempt; disabled pairing"
stopSending pip
return (Nothing, False)
|otherwise = return (Just pip, verified && sameuuid)
where
verified = verifiedPairMsg m pip
sameuuid = pairUUID (inProgressPairData pip) == pairUUID (pairMsgData m)
checkSane msg
{- Control characters could be used in a
- console poisoning attack. -}
| any isControl (filter (/= '\n') (decode_c msg)) = do
liftAnnex $ warning
"illegal control characters in pairing message; ignoring"
return False
| otherwise = return True
{- PairReqs invalidate the cache of recently finished pairings.
- This is so that, if a new pairing is started with the
- same secret used before, a bogus PairDone is not sent. -}
invalidateCache msg = filter (not . verifiedPairMsg msg)
getmsg sock c = do
(msg, n, _) <- recvFrom sock chunksz
if n < chunksz
then return $ c ++ msg
else getmsg sock $ c ++ msg
where
chunksz = 1024
{- Show an alert when a PairReq is seen. -}
pairReqReceived :: Bool -> UrlRenderer -> PairMsg -> Assistant ()
pairReqReceived True _ _ = noop -- ignore our own PairReq
pairReqReceived False urlrenderer msg = do
button <- mkAlertButton True (T.pack "Respond") urlrenderer (FinishLocalPairR msg)
void $ addAlert $ pairRequestReceivedAlert repo button
where
repo = pairRepo msg
{- When a verified PairAck is seen, a host is ready to pair with us, and has
- already configured our ssh key. Stop sending PairReqs, finish the pairing,
- and send a single PairDone. -}
pairAckReceived :: Bool -> Maybe PairingInProgress -> PairMsg -> [PairingInProgress] -> Assistant [PairingInProgress]
pairAckReceived True (Just pip) msg cache = do
stopSending pip
repodir <- repoPath <$> liftAnnex gitRepo
liftIO $ setupAuthorizedKeys msg repodir
finishedLocalPairing msg (inProgressSshKeyPair pip)
startSending pip PairDone $ multicastPairMsg
(Just 1) (inProgressSecret pip) (inProgressPairData pip)
return $ pip : take 10 cache
{- A stale PairAck might also be seen, after we've finished pairing.
- Perhaps our PairDone was not received. To handle this, we keep
- a cache of recently finished pairings, and re-send PairDone in
- response to stale PairAcks for them. -}
pairAckReceived _ _ msg cache = do
let pips = filter (verifiedPairMsg msg) cache
unless (null pips) $
forM_ pips $ \pip ->
startSending pip PairDone $ multicastPairMsg
(Just 1) (inProgressSecret pip) (inProgressPairData pip)
return cache
{- If we get a verified PairDone, the host has accepted our PairAck, and
- has paired with us. Stop sending PairAcks, and finish pairing with them.
-
- TODO: Should third-party hosts remove their pair request alert when they
- see a PairDone?
- Complication: The user could have already clicked on the alert and be
- entering the secret. Would be better to start a fresh pair request in this
- situation.
-}
pairDoneReceived :: Bool -> Maybe PairingInProgress -> PairMsg -> Assistant ()
pairDoneReceived False _ _ = noop -- not verified
pairDoneReceived True Nothing _ = noop -- not in progress
pairDoneReceived True (Just pip) msg = do
stopSending pip
finishedLocalPairing msg (inProgressSshKeyPair pip)
|
