Add SHA256 support

src/Crypto/Saltine/Core/Hash.hs

@@ -41,18 +41,28 @@
 -- This is version 2010.08.30 of the hash.html web page. Information
 -- about SipHash has been added.
 module Crypto.Saltine.Core.Hash (
+  -- * Documentation
   ShorthashKey,
   hash,
   shorthash, newShorthashKey,
   GenerichashKey,
   newGenerichashKey,
   GenerichashOutLen,
-  generichashOutLen, generichash
+  generichashOutLen, generichash,
+
+  -- * Advanced: SHA-2
+  --
+  -- | The SHA-256 function is provided for interoperability with
+  -- other applications. If you are looking for a generic hash
+  -- function and not specifically SHA-2, using 'generichash'
+  -- (BLAKE2b) might be a better choice.
+  sha256
   ) where
 
 import Crypto.Saltine.Internal.Hash
             ( c_hash
             , c_generichash
+            , c_hash_sha256
             , shorthash
             , ShorthashKey(..)
             , GenerichashKey(..)
@@ -72,7 +82,7 @@
      -> ByteString
      -- ^ Hash
 hash m = snd . buildUnsafeByteString Bytes.hash_bytes $ \ph ->
   constByteStrings [m] $ \[(pm, _)] -> c_hash ph pm (fromIntegral $ S.length m)
 
 -- | Randomly generates a new key for 'shorthash'.
 newShorthashKey :: IO ShorthashKey
@@ -101,3 +111,8 @@
 generichash (GhK k) m (GhOL outLen) = snd . buildUnsafeByteString outLen $ \ph ->
   constByteStrings [k, m] $ \[(pk, _), (pm, _)] ->
     c_generichash ph (fromIntegral outLen) pm (fromIntegral $ S.length m) pk (fromIntegral $ S.length k)
+
+-- | Computes a SHA256 hash.
+sha256 :: ByteString -> ByteString
+sha256 m = snd . buildUnsafeByteString Bytes.hash_sha256_bytes $ \ph ->
+  constByteStrings [m] $ \[(pm,_)] -> c_hash_sha256 ph pm (fromIntegral $ S.length m)

src/Crypto/Saltine/Internal/Hash.hs

@@ -14,9 +14,11 @@
   , shorthash_keybytes
   , generichash_bytes_max
   , generichash_keybytes_max
+  , hash_sha256_bytes
   , c_hash
   , c_shorthash
   , c_generichash
+  , c_hash_sha256
   , nullShKey
   , shorthash
   , ShorthashKey(..)
@@ -30,7 +32,7 @@
 import Data.ByteString              (ByteString)
 import Data.Data                    (Data, Typeable)
 import Data.Hashable                (Hashable)
 import Data.Monoid
 import Foreign.C
 import Foreign.Ptr
 import GHC.Generics                 (Generic)
@@ -57,7 +59,7 @@
           -> ByteString
           -- ^ Hash
 shorthash (ShK k) m = snd . buildUnsafeByteString shorthash_bytes $ \ph ->
   constByteStrings [k, m] $ \[(pk, _), (pm, _)] ->
     c_shorthash ph pm (fromIntegral $ S.length m) pk
 
 instance IsEncoding ShorthashKey where
@@ -85,7 +87,7 @@
 
 newtype GenerichashOutLen = GhOL { unGhOL :: Int } deriving (Eq, Ord, Hashable, Data, Typeable, Generic, NFData)
 
-hash_bytes, shorthash_bytes, shorthash_keybytes, generichash_bytes_max, generichash_keybytes_max :: Int
+hash_bytes, shorthash_bytes, shorthash_keybytes, generichash_bytes_max, generichash_keybytes_max, hash_sha256_bytes :: Int
 
 -- Hashes
 -- | The size of a hash resulting from
@@ -103,6 +105,9 @@
 -- | The maximum key size of the generic hash function
 -- 'Crypto.Saltine.Core.Hash.generichash'
 generichash_keybytes_max = fromIntegral c_crypto_generichash_keybytes_max
+-- | The size of a hash resulting from
+-- 'Crypto.Saltine.Core.Hash.sha256'.
+hash_sha256_bytes = fromIntegral c_crypto_hash_sha256_bytes
 
 -- src/libsodium/crypto_generichash/crypto_generichash.c
 foreign import ccall "crypto_generichash_bytes_max"
@@ -122,6 +127,11 @@
 foreign import ccall "crypto_shorthash_keybytes"
   c_crypto_shorthash_keybytes :: CSize
 
+-- src/libsodium/crypto_hash/sha256/hash_sha256.c
+-- src/libsodium/include/sodium/crypto_hash_sha256.h
+foreign import ccall "crypto_hash_sha256_bytes"
+  c_crypto_hash_sha256_bytes :: CSize
+
 
 foreign import ccall "crypto_hash"
   c_hash :: Ptr CChar
@@ -160,3 +170,13 @@
                 -- ^ Key buffer length
                 -> IO CInt
                 -- ^ Always 0
+
+foreign import ccall "crypto_hash_sha256"
+  c_hash_sha256 :: Ptr CChar
+                -- ^ Output hash buffer
+                -> Ptr CChar
+                -- ^ Constant message buffer
+                -> CULLong
+                -- ^ Message buffer length
+                -> IO CInt
+                -- ^ Always 0