Fix an "insufficient buffer space" bug in Botan.Low.Cipher.cipherUpdate

botan-low/CHANGELOG.md

@@ -42,6 +42,9 @@
 * PATCH: fix an "insufficient buffer space" bug in
   `Botan.Low.PubKey.Encrypt.encrypt` and `Botan.Low.PubKey.Decrypt.decrypt`. See
   PR [#79](https://github.com/haskell-cryptography/botan/pull/79).
+* PATCH: Fix an "insufficient buffer space" bug in
+  `Botan.Low.Cipher.cipherUpdate`. See PR
+  [#84](https://github.com/haskell-cryptography/botan/pull/84)
 
 ## 0.0.2.0 -- 2025-09-17
 

botan-low/src/Botan/Low/Cipher.hs

@@ -97,15 +97,14 @@ module Botan.Low.Cipher (
 
   ) where
 
-import qualified Data.ByteString as ByteString
-
 import           Botan.Bindings.Cipher
-
 import           Botan.Low.BlockCipher
 import           Botan.Low.Error
 import           Botan.Low.Make
 import           Botan.Low.Prelude
 import           Botan.Low.Remake
+import           Data.Bits ((.&.))
+import qualified Data.ByteString as ByteString
 
 {- $introduction
 
@@ -442,31 +441,50 @@ cipherStart = mkWithObjectSetterCBytesLen withCipher botan_cipher_start
 --  https://github.com/randombit/botan/blob/72dc18bbf598f2c3bef81a4fb2915e9c3c524ac4/src/lib/ffi/ffi_cipher.cpp#L133
 --
 -- Some ciphers (ChaChaPoly, EAX) may consume less input than the reported ideal granularity
-cipherUpdate
-    :: Cipher               -- ^ __cipher__
-    -> CipherUpdateFlags    -- ^ __flags__
-    -> Int                  -- ^ __output_size__
-    -> ByteString           -- ^ __input_bytes[]__
-    -> IO (Int,ByteString)  -- ^ __(input_consumed,output[])__
-cipherUpdate ctx flags outputSz input = withCipher ctx $ \ ctxPtr -> do
-    unsafeAsBytesLen input $ \ inputPtr inputSz -> do
-        alloca $ \ consumedPtr -> do
-            alloca $ \ writtenPtr -> do
-                output <- allocBytes outputSz $ \ outputPtr -> do
-                    throwBotanIfNegative_ $ botan_cipher_update
-                        ctxPtr
-                        (fromIntegral flags)
-                        outputPtr
-                        (fromIntegral outputSz)
-                        writtenPtr
-                        (ConstPtr inputPtr)
-                        inputSz
-                        consumedPtr
-                consumed <- fromIntegral <$> peek consumedPtr
-                written <- fromIntegral <$> peek writtenPtr
-                -- NOTE: The safety of this function is suspect - may require deepseq
-                let processed = ByteString.take written output
-                    in processed `seq` return (consumed,processed)
+cipherUpdate ::
+     Cipher               -- ^ __cipher__
+  -> CipherUpdateFlags    -- ^ __flags__
+  -> Int                  -- ^ __output_size__
+  -> ByteString           -- ^ __input_bytes[]__
+  -> IO (Int,ByteString)  -- ^ __(input_consumed,output[])__
+cipherUpdate ctx flags outputSz input =
+    withCipher ctx $ \ ctxPtr ->
+    unsafeAsBytesLen input $ \ inputPtr inputSz ->
+    alloca $ \ consumedPtr ->
+    alloca $ \ writtenPtr -> do
+      eithOutput <-
+        try $ allocBytes outputSz $ \ outputPtr ->do
+          throwBotanIfNegative_ $ botan_cipher_update
+              ctxPtr
+              (fromIntegral flags)
+              outputPtr
+              (fromIntegral outputSz)
+              writtenPtr
+              (ConstPtr inputPtr)
+              inputSz
+              consumedPtr
+      -- If inssuficient buffer space, try again
+      output <- case eithOutput of
+        Left InsufficientBufferSpaceException{} -> do
+          outputSz' <- peek writtenPtr
+          allocBytes (fromIntegral outputSz') $ \ outputPtr ->do
+            throwBotanIfNegative_ $ botan_cipher_update
+                ctxPtr
+                (fromIntegral flags)
+                outputPtr
+                outputSz'
+                writtenPtr
+                (ConstPtr inputPtr)
+                -- No input should be provided on the second try if the first
+                -- try had the FINAL flag set
+                (if flags .&. BOTAN_CIPHER_UPDATE_FLAG_FINAL /= 0 then 0 else inputSz)
+                consumedPtr
+        Right bs -> pure bs
+      consumed <- fromIntegral <$> peek consumedPtr
+      written <- fromIntegral <$> peek writtenPtr
+      -- NOTE: The safety of this function is suspect - may require deepseq
+      let processed = ByteString.take written output
+          in processed `seq` return (consumed,processed)
 
 {- |
 Encrypt and finalize a complete piece of data.

botan-low/test/Test/Botan/Low/Cipher.hs

@@ -3,9 +3,14 @@
 
 module Test.Botan.Low.Cipher (tests) where
 
+import           Botan.Bindings.Version (botan_version_major,
+                     botan_version_minor)
 import           Botan.Low.Cipher
 import           Botan.Low.RNG
 import           Control.Monad
+import           Data.ByteString (ByteString)
+import qualified Data.ByteString as BS
+import           System.IO.Unsafe (unsafePerformIO)
 import           Test.Hspec
 import           Test.Tasty
 import           Test.Tasty.Hspec
@@ -17,13 +22,25 @@ tests = do
     specs <- testSpec "spec_cipher" spec_cipher
     pure $ testGroup "Test.Botan.Low.Cipher" [
         specs
-        -- TODO: temporarily disabled because the test suite fails. See issue
-        -- #33.
-      | False
       ]
 
+testModes :: [ByteString]
+testModes = filter p (cipherModes ++ aeads)
+  where
+    p s
+      -- TODO: also test "Lion" and "Cascade"
+      | "Lion" `BS.isPrefixOf` s || "Cascade" `BS.isPrefixOf` s
+      = False
+      -- SIV and CCM have bugs on versions earlier than 3.5
+      | unsafePerformIO botan_version_major == 3
+      , unsafePerformIO botan_version_minor <= 4
+      , "SIV" `BS.isSuffixOf` s || "CCM" `BS.isSuffixOf` s
+      = False
+      | otherwise
+      = True
+
 spec_cipher :: Spec
-spec_cipher = testSuite (cipherModes ++ aeads) chars $ \ cipher -> do
+spec_cipher = testSuite testModes chars $ \ cipher -> do
     it "can initialize a cipher encryption context" $ do
         _ctx <- cipherInit cipher Encrypt
         pass
@@ -221,10 +238,7 @@ spec_cipher = testSuite (cipherModes ++ aeads) chars $ \ cipher -> do
         cipherStart offlinectx n
         g <- cipherGetIdealUpdateGranularity onlinectx
         msg <- systemRNGGet (8 * g)
-        putStrLn "    Testing online encryption:"
         onlinemsg <- cipherEncryptOnline onlinectx msg
-        putStrLn "    Testing offline encryption:"
         offlinemsg <- cipherEncrypt offlinectx msg
-        putStrLn "    Result:"
         onlinemsg `shouldBe` offlinemsg
         pass