filter out control characters in error messages

giveup changed to filter out control characters. (It is too low level to
make it use StringContainingQuotedPath.)

error still does not, but it should only be used for internal errors,
where the message is not attacker-controlled.

Changed a lot of existing error to giveup when it is not strictly an
internal error.

Of course, other exceptions can still be thrown, either by code in
git-annex, or a library, that include some attacker-controlled value.
This does not guard against those.

Sponsored-by: Noam Kremen on Patreon

Utility/WebApp.hs

@@ -87,7 +87,7 @@ getSocket h = do
 	-- getAddrInfo didn't used to work on windows; current status
 	-- unknown.
 	when (isJust h) $
-		error "getSocket with HostName not supported on this OS"
+		giveup "getSocket with HostName not supported on this OS"
 	let addr = tupleToHostAddress (127,0,0,1)
 	sock <- socket AF_INET Stream defaultProtocol
 	preparesocket sock
@@ -99,7 +99,7 @@ getSocket h = do
 	case (partition (\a -> addrFamily a == AF_INET) addrs) of
 		(v4addr:_, _) -> go v4addr
 		(_, v6addr:_) -> go v6addr
-		_ -> error "unable to bind to a local socket"
+		_ -> giveup "unable to bind to a local socket"
   where
 	hostname = fromMaybe localhost h
 	localhost = "localhost"
@@ -108,7 +108,7 @@ getSocket h = do
 	 - unknown reason on OSX. -} 
 	go addr = go' 100 addr
 	go' :: Int -> AddrInfo -> IO Socket
-	go' 0 _ = error "unable to bind to local socket"
+	go' 0 _ = giveup "unable to bind to local socket"
 	go' n addr = do
 		r <- tryIO $ bracketOnError (open addr) close (useaddr addr)
 		either (const $ go' (pred n) addr) return r
@@ -129,9 +129,9 @@ webAppSessionBackend :: Yesod.Yesod y => y -> IO (Maybe Yesod.SessionBackend)
 webAppSessionBackend _ = do
 	g <- newGenIO :: IO SystemRandom
 	case genBytes 96 g of
-		Left e -> error $ "failed to generate random key: " ++ show e
+		Left e -> giveup $ "failed to generate random key: " ++ show e
 		Right (s, _) -> case CS.initKey s of
-			Left e -> error $ "failed to initialize key: " ++ show e
+			Left e -> giveup $ "failed to initialize key: " ++ show e
 			Right key -> use key
   where
 	timeout = 120 * 60 -- 120 minutes