core: add signatureToText function and tests

- make NarSignature's Show instance more legible
- add Arbitrary instance for NarSignature
- add roundtrip quickcheck tests for NarSignature encoding

Author: squalus

hnix-store-core/src/System/Nix/Signature.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NamedFieldPuns #-}
 {-|
 Description : Nix-relevant interfaces to NaCl signatures.
 -}
@@ -8,22 +9,23 @@ module System.Nix.Signature
   , NarSignature(..)
   , signatureParser
   , parseSignature
+  , signatureToText
   ) where
 
+import Crypto.Error (CryptoFailable(..))
+import Data.ByteString (ByteString)
+import Data.Text (Text)
 import GHC.Generics (Generic)
+import System.Nix.Base (decodeWith, encodeWith, BaseEncoding(Base64))
 
-import qualified Crypto.PubKey.Ed25519
-import Crypto.Error (CryptoFailable(..))
+import qualified Crypto.PubKey.Ed25519 as Ed25519
 import qualified Data.Attoparsec.Text
-import qualified Data.Char
 import qualified Data.ByteArray
-import qualified Data.ByteString as BS
-import Data.Text (Text)
-import qualified System.Nix.Base
-import System.Nix.Base (BaseEncoding(Base64))
+import qualified Data.Char
+import qualified Data.Text
 
 -- | An ed25519 signature.
-newtype Signature = Signature Crypto.PubKey.Ed25519.Signature
+newtype Signature = Signature Ed25519.Signature
   deriving (Eq, Generic, Show)
 
 -- | A detached signature attesting to a nix archive's validity.
@@ -33,29 +35,34 @@ data NarSignature = NarSignature
   , -- | The archive's signature.
     sig :: !Signature
   }
-  deriving (Eq, Generic, Ord, Show)
+  deriving (Eq, Generic, Ord)
 
 instance Ord Signature where
   compare (Signature x) (Signature y) = let
-    xBS = Data.ByteArray.convert x :: BS.ByteString
-    yBS = Data.ByteArray.convert y :: BS.ByteString
+    xBS = Data.ByteArray.convert x :: ByteString
+    yBS = Data.ByteArray.convert y :: ByteString
     in compare xBS yBS
 
 signatureParser :: Data.Attoparsec.Text.Parser NarSignature
 signatureParser = do
   publicKey <- Data.Attoparsec.Text.takeWhile1 (/= ':')
   _ <- Data.Attoparsec.Text.string ":"
   encodedSig <- Data.Attoparsec.Text.takeWhile1 (\c -> Data.Char.isAlphaNum c || c == '+' || c == '/' || c == '=')
-  decodedSig <- case System.Nix.Base.decodeWith Base64 encodedSig of
+  decodedSig <- case decodeWith Base64 encodedSig of
     Left e -> fail e
     Right decodedSig -> pure decodedSig
-  sig <- case Crypto.PubKey.Ed25519.signature decodedSig of
+  sig <- case Ed25519.signature decodedSig of
     CryptoFailed e -> (fail . show) e
     CryptoPassed sig -> pure sig
   pure $ NarSignature publicKey (Signature sig)
 
-parseSignature
-  :: Text -> Either String NarSignature
-parseSignature =
-  Data.Attoparsec.Text.parseOnly signatureParser
+parseSignature :: Text -> Either String NarSignature
+parseSignature = Data.Attoparsec.Text.parseOnly signatureParser
+
+signatureToText :: NarSignature -> Text
+signatureToText NarSignature {publicKey, sig=Signature sig'} = let
+  b64Encoded = encodeWith Base64 (Data.ByteArray.convert sig' :: ByteString)
+  in mconcat [ publicKey, ":", b64Encoded ]
 
+instance Show NarSignature where
+  show narSig = Data.Text.unpack (signatureToText narSig)

hnix-store-tests/hnix-store-tests.cabal

@@ -41,6 +41,7 @@ library
     , System.Nix.Arbitrary.Derivation
     , System.Nix.Arbitrary.DerivedPath
     , System.Nix.Arbitrary.Hash
+    , System.Nix.Arbitrary.Signature
     , System.Nix.Arbitrary.Store.Types
     , System.Nix.Arbitrary.StorePath
     , Test.Hspec.Nix
@@ -67,6 +68,7 @@ test-suite props
       DerivationSpec
       DerivedPathSpec
       StorePathSpec
+      SignatureSpec
   hs-source-dirs:
     tests
   build-tool-depends:

hnix-store-tests/src/System/Nix/Arbitrary.hs

@@ -5,5 +5,6 @@ import System.Nix.Arbitrary.ContentAddress ()
 import System.Nix.Arbitrary.Derivation ()
 import System.Nix.Arbitrary.DerivedPath ()
 import System.Nix.Arbitrary.Hash ()
+import System.Nix.Arbitrary.Signature ()
 import System.Nix.Arbitrary.Store.Types ()
 import System.Nix.Arbitrary.StorePath ()

hnix-store-tests/src/System/Nix/Arbitrary/Signature.hs

@@ -0,0 +1,36 @@
+-- due to recent generic-arbitrary
+{-# OPTIONS_GHC -fconstraint-solver-iterations=0 #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+{-# LANGUAGE OverloadedStrings #-}
+module System.Nix.Arbitrary.Signature where
+
+import qualified Crypto.PubKey.Ed25519
+import Crypto.Random (drgNewTest, withDRG)
+import qualified Data.ByteString as BS
+import qualified Data.Text as Text
+import Test.QuickCheck.Arbitrary.Generic (GenericArbitrary(..))
+import Test.QuickCheck.Instances ()
+import Test.QuickCheck
+
+import System.Nix.Signature
+
+instance Arbitrary Crypto.PubKey.Ed25519.Signature where
+  arbitrary = do
+    seeds <- (,,,,) <$> arbitraryBoundedRandom <*> arbitraryBoundedRandom <*> arbitraryBoundedRandom <*> arbitraryBoundedRandom <*> arbitraryBoundedRandom
+    let drg = drgNewTest seeds
+        (secretKey, _) = withDRG drg Crypto.PubKey.Ed25519.generateSecretKey
+        publicKey = Crypto.PubKey.Ed25519.toPublic secretKey
+        msg :: BS.ByteString = "msg"
+    pure $ Crypto.PubKey.Ed25519.sign secretKey publicKey msg
+
+deriving via GenericArbitrary Signature
+  instance Arbitrary Signature
+
+instance Arbitrary NarSignature where
+  arbitrary = do
+    name <- Text.pack . getPrintableString <$> suchThat arbitrary (\(PrintableString str) -> validName str)
+    NarSignature name <$> arbitrary
+
+validName :: String -> Bool
+validName txt = not (null txt) && not (elem ':' txt)
+

hnix-store-tests/tests/SignatureSpec.hs

@@ -0,0 +1,13 @@
+module SignatureSpec where
+
+import Test.Hspec (Spec, describe)
+import Test.Hspec.Nix (roundtrips)
+import Test.Hspec.QuickCheck (prop)
+
+import System.Nix.Signature (signatureToText, parseSignature)
+import System.Nix.Arbitrary ()
+
+spec :: Spec
+spec = do
+  describe "Signature" $ do
+    prop "roundtrips" $ roundtrips signatureToText parseSignature