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{-| Implementation of the Ganeti confd utilities.

This holds a few utility functions that could be useful in both

clients and servers.

-}

{-

Copyright (C) 2011, 2012 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Confd.Utils

  ( getClusterHmac

  , parseRequest

  , parseMessage

  , signMessage

  ) where

import qualified Data.ByteString as B

import qualified Text.JSON as J

import Ganeti.BasicTypes

import Ganeti.Confd.Types

import Ganeti.Hash

import qualified Ganeti.Constants as C

import qualified Ganeti.Path as Path

import Ganeti.JSON

import Ganeti.Utils

-- | Type-adjusted max clock skew constant.

maxClockSkew :: Integer

maxClockSkew = fromIntegral C.confdMaxClockSkew

-- | Returns the HMAC key.

getClusterHmac :: IO HashKey

getClusterHmac = Path.confdHmacKey >>= fmap B.unpack . B.readFile

-- | Parses a signed request.

parseRequest :: HashKey -> String -> Result (String, String, ConfdRequest)

parseRequest key str = do

  (SignedMessage hmac msg salt) <- fromJResult "parsing request" $ J.decode str

  req <- if verifyMac key (Just salt) msg hmac

           then fromJResult "parsing message" $ J.decode msg

           else Bad "HMAC verification failed"

  return (salt, msg, req)

-- | Message parsing. This can either result in a good, valid message,

-- or fail in the Result monad.

parseMessage :: HashKey -> String -> Integer

             -> Result (String, ConfdRequest)

parseMessage hmac msg curtime = do

  (salt, origmsg, request) <- parseRequest hmac msg

  ts <- tryRead "Parsing timestamp" salt::Result Integer

  if abs (ts - curtime) > maxClockSkew

    then fail "Too old/too new timestamp or clock skew"

    else return (origmsg, request)

-- | Signs a message with a given key and salt.

signMessage :: HashKey -> String -> String -> SignedMessage

signMessage key salt msg =

  SignedMessage { signedMsgMsg  = msg

                , signedMsgSalt = salt

                , signedMsgHmac = hmac

                }

    where hmac = computeMac key (Just salt) msg