core: encrypt/decrypt WebRTC frames (#1935)

* core: encrypt/decrypt WebRTC frames

* swift API

* add decrypt stub

* change name

* remove unused type

* move functions

* update cabal file

* copy bytes from encrypted string

apps/ios/SimpleXChat/SimpleX.h

@@ -22,3 +22,5 @@ extern char *chat_recv_msg(chat_ctrl ctl);
 extern char *chat_recv_msg_wait(chat_ctrl ctl, int wait);
 extern char *chat_parse_markdown(char *str);
 extern char *chat_parse_server(char *str);
+extern void chat_encrypt_media(char *key, char *frame, int len);
+extern void chat_decrypt_media(char *key, char *frame, int len);

simplex-chat.cabal

@@ -85,6 +85,7 @@ library
       Simplex.Chat.Migrations.M20230129_drop_chat_items_group_idx
       Simplex.Chat.Migrations.M20230206_item_deleted_by_group_member_id
       Simplex.Chat.Mobile
+      Simplex.Chat.Mobile.WebRTC
       Simplex.Chat.Options
       Simplex.Chat.ProfileGenerator
       Simplex.Chat.Protocol

src/Simplex/Chat/Mobile.hs

@@ -18,6 +18,7 @@ import Data.Functor (($>))
 import Data.List (find)
 import qualified Data.List.NonEmpty as L
 import Data.Maybe (fromMaybe)
+import Data.Word (Word8)
 import Database.SQLite.Simple (SQLError (..))
 import qualified Database.SQLite.Simple as DB
 import Foreign.C.String
@@ -29,6 +30,7 @@ import GHC.Generics (Generic)
 import Simplex.Chat
 import Simplex.Chat.Controller
 import Simplex.Chat.Markdown (ParsedMarkdown (..), parseMaybeMarkdownList)
+import Simplex.Chat.Mobile.WebRTC
 import Simplex.Chat.Options
 import Simplex.Chat.Store
 import Simplex.Chat.Types
@@ -63,6 +65,10 @@ foreign export ccall "chat_parse_markdown" cChatParseMarkdown :: CString -> IO C
 
 foreign export ccall "chat_parse_server" cChatParseServer :: CString -> IO CJSONString
 
+foreign export ccall "chat_encrypt_media" cChatEncryptMedia :: CString -> Ptr Word8 -> CInt -> IO ()
+
+foreign export ccall "chat_decrypt_media" cChatDecryptMedia :: CString -> Ptr Word8 -> CInt -> IO ()
+
 -- | check / migrate database and initialize chat controller on success
 cChatMigrateInit :: CString -> CString -> Ptr (StablePtr ChatController) -> IO CJSONString
 cChatMigrateInit fp key ctrl = do

src/Simplex/Chat/Mobile/WebRTC.hs

@@ -0,0 +1,43 @@
+module Simplex.Chat.Mobile.WebRTC where
+
+import qualified Data.ByteString as B
+import Data.ByteString.Internal (ByteString(PS), memcpy)
+import Foreign.C (CInt, CString)
+import Foreign.Ptr (Ptr, plusPtr)
+import Foreign.ForeignPtr (newForeignPtr_)
+import Foreign.ForeignPtr.Unsafe (unsafeForeignPtrToPtr)
+import Control.Monad (when)
+import Data.Word (Word8)
+
+cChatEncryptMedia :: CString -> Ptr Word8 -> CInt -> IO ()
+cChatEncryptMedia = cTransformMedia chatEncryptMedia
+
+cChatDecryptMedia :: CString -> Ptr Word8 -> CInt -> IO ()
+cChatDecryptMedia = cTransformMedia chatDecryptMedia
+
+cTransformMedia :: (ByteString -> ByteString -> ByteString) -> CString -> Ptr Word8 -> CInt -> IO ()
+cTransformMedia f cKey cFrame cFrameLen = do
+  key <- B.packCStringLen (cKey, 32)
+  frame <- getByteString cFrame cFrameLen
+  let frame' = f key frame
+  putByteString frame' cFrame cFrameLen
+{-# INLINE cTransformMedia #-}
+
+chatEncryptMedia :: ByteString -> ByteString -> ByteString
+chatEncryptMedia _key frame = frame
+
+chatDecryptMedia :: ByteString -> ByteString -> ByteString
+chatDecryptMedia _key frame = frame
+
+getByteString :: Ptr Word8 -> CInt -> IO ByteString
+getByteString p size = do
+  fp <- newForeignPtr_ p
+  pure $ PS fp 0 $ fromIntegral size
+{-# INLINE getByteString #-}
+
+putByteString :: ByteString -> Ptr Word8 -> CInt -> IO ()
+putByteString bs@(PS fp offset _) to size = do
+  let len = B.length bs
+      p = unsafeForeignPtrToPtr fp `plusPtr` offset
+  when (len <= fromIntegral size) $ memcpy to p len
+{-# INLINE putByteString #-}