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core: use 12 bytes IV for WebRTC frame encryption with AES-GCM (#1951)

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* core: use 12 bytes IV for WebRTC frame encryption with AES-GCM

* refactor
This commit is contained in:
Evgeny Poberezkin
2023-02-25 17:52:23 +00:00
committed by GitHub
parent 6eddb5f30f
commit 50b90c4814
5 changed files with 36 additions and 37 deletions
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src/Simplex/Chat/Mobile/WebRTC.hs
+27 -29
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@@ -1,10 +1,15 @@
{-# LANGUAGE FlexibleContexts #-}
module Simplex.Chat.Mobile.WebRTC where
module Simplex.Chat.Mobile.WebRTC (
cChatEncryptMedia,
cChatDecryptMedia,
chatEncryptMedia,
chatDecryptMedia,
reservedSize,
) where
import Control.Monad.Except
import qualified Crypto.Cipher.Types as AES
import Crypto.Random (getRandomBytes)
import Data.Bifunctor (bimap)
import qualified Data.ByteArray as BA
import qualified Data.ByteString as B
@@ -41,44 +46,37 @@ cTransformMedia f cKey cFrame cFrameLen = do
chatEncryptMedia :: ByteString -> ByteString -> ExceptT String IO ByteString
chatEncryptMedia keyStr frame = do
checkFrameLen frame
len <- checkFrameLen frame
key <- decodeKey keyStr
iv <- liftIO $ getRandomBytes ivSize
let (frame', _) = B.splitAt (B.length frame - reservedSize) frame
(tag, frame'') <- withExceptT show $ C.encryptAESNoPad key (C.IV $ iv <> ivPad) frame'
let authTag = BA.convert $ C.unAuthTag tag
pure $ frame'' <> authTag <> iv
iv <- liftIO C.randomGCMIV
(tag, frame') <- withExceptT show $ C.encryptAESNoPad key iv $ B.take len frame
pure $ frame' <> BA.convert (C.unAuthTag tag) <> C.unGCMIV iv
chatDecryptMedia :: ByteString -> ByteString -> ExceptT String IO ByteString
chatDecryptMedia keyStr frame = do
checkFrameLen frame
len <- checkFrameLen frame
key <- decodeKey keyStr
let (rest, iv) = B.splitAt (B.length frame - ivSize) frame
(frame', tag) = B.splitAt (B.length rest - C.authTagSize) rest
let (frame', rest) = B.splitAt len frame
(tag, iv) = B.splitAt C.authTagSize rest
authTag = C.AuthTag $ AES.AuthTag $ BA.convert tag
frame'' <- withExceptT show $ C.decryptAESNoPad key (C.IV $ iv <> ivPad) frame' authTag
pure $ frame'' <> B.replicate reservedSize 0
withExceptT show $ do
iv' <- liftEither $ C.gcmIV iv
frame'' <- C.decryptAESNoPad key iv' frame' authTag
pure $ frame'' <> framePad
checkFrameLen :: ByteString -> ExceptT String IO ()
checkFrameLen frame =
when (B.length frame < reservedSize) $ throwError "frame has no [reserved space] IV and/or auth tag"
checkFrameLen :: ByteString -> ExceptT String IO Int
checkFrameLen frame = do
let len = B.length frame - reservedSize
when (len < 0) $ throwError "frame has no [reserved space for] IV and/or auth tag"
pure len
{-# INLINE checkFrameLen #-}
decodeKey :: ByteString -> ExceptT String IO C.Key
decodeKey = liftEither . bimap ("invalid key: " <>) C.Key . U.decode
{-# INLINE decodeKey #-}
authTagSize :: Int
authTagSize = C.authTagSize
{-# INLINE authTagSize #-}
ivSize :: Int
ivSize = 12
{-# INLINE ivSize #-}
ivPad :: ByteString
ivPad = B.replicate 4 0
reservedSize :: Int
reservedSize = authTagSize + ivSize
{-# INLINE reservedSize #-}
reservedSize = C.authTagSize + C.gcmIVSize
framePad :: ByteString
framePad = B.replicate reservedSize 0