module Hackage.Security.Trusted.TCB (
    -- * Trusted values
    Trusted(DeclareTrusted)
  , trusted
  , trustStatic
  , trustVerified
  , trustApply
  , trustElems
    -- * Verification errors
  , VerificationError(..)
  , RootUpdated(..)
  , VerificationHistory
    -- * Role verification
  , SignaturesVerified -- opaque
  , signaturesVerified
  , verifyRole'
  , verifyFingerprints
    -- * Re-exports
  , StaticPtr
  ) where

import Prelude
import Control.Exception
import Control.Monad (when, unless)
import Control.Monad.Except (Except, runExcept, throwError)
import Data.Typeable
import Data.Time
import Hackage.Security.TUF
import Hackage.Security.JSON
import Hackage.Security.Key
import Hackage.Security.Util.Pretty
import qualified Hackage.Security.Util.Lens as Lens

import GHC.StaticPtr

-- | Trusted values
--
-- Trusted values originate in only two ways:
--
-- * Anything that is statically known is trusted ('trustStatic')
-- * If we have "dynamic" data we can trust it once we have verified the
--   the signatures (trustSigned).
--
-- NOTE: Trusted is NOT a functor. If it was we could define
--
-- > trustAnything :: a -> Trusted a
-- > trustAnything a = fmap (const a) (trustStatic (static ()))
--
-- Consequently, it is neither a monad nor a comonad. However, we _can_ apply
-- trusted functions to trusted arguments ('trustApply').
--
-- The 'DeclareTrusted' constructor is exported, but any use of it should be
-- verified.
newtype Trusted a = DeclareTrusted { forall a. Trusted a -> a
trusted :: a }
  deriving (Trusted a -> Trusted a -> Bool
(Trusted a -> Trusted a -> Bool)
-> (Trusted a -> Trusted a -> Bool) -> Eq (Trusted a)
forall a. Eq a => Trusted a -> Trusted a -> Bool
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: forall a. Eq a => Trusted a -> Trusted a -> Bool
== :: Trusted a -> Trusted a -> Bool
$c/= :: forall a. Eq a => Trusted a -> Trusted a -> Bool
/= :: Trusted a -> Trusted a -> Bool
Eq, Int -> Trusted a -> ShowS
[Trusted a] -> ShowS
Trusted a -> String
(Int -> Trusted a -> ShowS)
-> (Trusted a -> String)
-> ([Trusted a] -> ShowS)
-> Show (Trusted a)
forall a. Show a => Int -> Trusted a -> ShowS
forall a. Show a => [Trusted a] -> ShowS
forall a. Show a => Trusted a -> String
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: forall a. Show a => Int -> Trusted a -> ShowS
showsPrec :: Int -> Trusted a -> ShowS
$cshow :: forall a. Show a => Trusted a -> String
show :: Trusted a -> String
$cshowList :: forall a. Show a => [Trusted a] -> ShowS
showList :: [Trusted a] -> ShowS
Show)

trustStatic :: StaticPtr a -> Trusted a
trustStatic :: forall a. StaticPtr a -> Trusted a
trustStatic = a -> Trusted a
forall a. a -> Trusted a
DeclareTrusted (a -> Trusted a) -> (StaticPtr a -> a) -> StaticPtr a -> Trusted a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. StaticPtr a -> a
forall a. StaticPtr a -> a
deRefStaticPtr

trustVerified :: SignaturesVerified a -> Trusted a
trustVerified :: forall a. SignaturesVerified a -> Trusted a
trustVerified = a -> Trusted a
forall a. a -> Trusted a
DeclareTrusted (a -> Trusted a)
-> (SignaturesVerified a -> a) -> SignaturesVerified a -> Trusted a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. SignaturesVerified a -> a
forall a. SignaturesVerified a -> a
signaturesVerified

-- | Equivalent of '<*>'
--
-- Trusted isn't quite applicative (no pure, not a functor), but it is
-- somehow Applicative-like: we have the equivalent of '<*>'
trustApply :: Trusted (a -> b) -> Trusted a -> Trusted b
trustApply :: forall a b. Trusted (a -> b) -> Trusted a -> Trusted b
trustApply (DeclareTrusted a -> b
f) (DeclareTrusted a
x) = b -> Trusted b
forall a. a -> Trusted a
DeclareTrusted (a -> b
f a
x)

-- | Trust all elements of some trusted (traversable) container
--
-- If we have, say, a trusted list of values, we should be able to get a list
-- of trusted values out of it.
--
-- > trustElems :: Trusted [a] -> [Trusted a]
--
-- NOTE. It might appear that the more natural primitive to offer is a
-- 'sequenceA'-like operator such as
--
-- > trustSeq :: Applicative f => Trusted (f a) -> f (Trusted a)
--
-- However, this is unsound. To see this, consider that @((->) a)@ is
-- 'Applicative' (it's the reader monad); hence, we can instantiate 'trustSeq'
-- at
--
-- > trustSeq :: Trusted (a -> a) -> a -> Trusted a
--
-- and by passing @trustStatic (static id)@ make 'Trusted' a functor, which we
-- certainly don't want to do (see comments for 'Trusted').
--
-- So why is it okay when we insist on 'Traversable' rather than 'Applicative'?
-- To see this, it's instructive to consider how we might make a @((->) a)@ an
-- instance of 'Traversable'. If we define the domain of enumerable types as
--
-- > class Eq a => Enumerable a where
-- >   enumerate :: [a]
--
-- then we can make @((->) r)@ traversable by
--
-- > instance Enumerable r => Traversable ((->) r) where
-- >   sequenceA f = rebuild <$> sequenceA ((\r -> (r,) <$> f r) <$> enumerate)
-- >     where
-- >       rebuild :: [(r, a)] -> r -> a
-- >       rebuild fun arg = fromJust (lookup arg fun)
--
-- The idea is that if the domain of a function is enumerable, we can apply the
-- function to each possible input, collect the outputs, and construct a new
-- function by pairing the inputs with the outputs. I.e., if we had something of
-- type
--
-- > a -> IO b
--
-- and @a@ is enumerable, we just run the @IO@ action on each possible @a@ and
-- collect all @b@s to get a pure function @a -> b@. Of course, you probably
-- don't want to be doing that, but the point is that as far as the type system
-- is concerned you could.
--
-- In the context of 'Trusted', this means that we can derive
--
-- > enumPure :: Enumerable a => a -> Trusted a
--
-- but in a way this this makes sense anyway. If a domain is enumerable, it
-- would not be unreasonable to change @Enumerable@ to
--
-- > class Eq a => Enumerable a where
-- >   enumerate :: [StaticPtr a]
--
-- so we could define @enumPure@ as
--
-- > enumPure :: Enumerable a => a -> Trusted a
-- > enumPure x = trustStatic
-- >            $ fromJust (find ((== x) . deRefStaticPtr) enumerate)
--
-- In other words, we just enumerate the entire domain as trusted values
-- (because we defined them locally) and then return the one that matched the
-- untrusted value.
--
-- The conclusion from all of this is that the types of untrusted input  (like
-- the types of the TUF files we download from the server) should probably not
-- be considered enumerable.
trustElems :: Traversable f => Trusted (f a) -> f (Trusted a)
trustElems :: forall (f :: * -> *) a.
Traversable f =>
Trusted (f a) -> f (Trusted a)
trustElems (DeclareTrusted f a
fa) = a -> Trusted a
forall a. a -> Trusted a
DeclareTrusted (a -> Trusted a) -> f a -> f (Trusted a)
forall a b. (a -> b) -> f a -> f b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` f a
fa

{-------------------------------------------------------------------------------
  Role verification
-------------------------------------------------------------------------------}

newtype SignaturesVerified a = SignaturesVerified { forall a. SignaturesVerified a -> a
signaturesVerified :: a }

-- | Errors thrown during role validation
data VerificationError =
     -- | Not enough signatures signed with the appropriate keys
     VerificationErrorSignatures TargetPath -- what were we verifying?
                                 Integer    -- threshold
                                 [KeyId]    -- trusted keys
                                 [KeyId]    -- found signing keys

     -- | The file is expired
   | VerificationErrorExpired TargetPath

     -- | The file version is less than the previous version
   | VerificationErrorVersion TargetPath

     -- | File information mismatch
   | VerificationErrorFileInfo TargetPath

     -- | We tried to lookup file information about a particular target file,
     -- but the information wasn't in the corresponding @targets.json@ file.
   | VerificationErrorUnknownTarget TargetPath

     -- | The metadata for the specified target is missing a SHA256
   | VerificationErrorMissingSHA256 TargetPath

     -- | Some verification errors materialize as deserialization errors
     --
     -- For example: if we try to deserialize a timestamp file but the timestamp
     -- key has been rolled over, deserialization of the file will fail with
     -- 'DeserializationErrorUnknownKey'.
   | VerificationErrorDeserialization TargetPath DeserializationError

     -- | The spec stipulates that if a verification error occurs during
     -- the check for updates, we must download new root information and
     -- start over. However, we limit how often we attempt this.
     --
     -- We record all verification errors that occurred before we gave up.
   | VerificationErrorLoop VerificationHistory
   deriving (Typeable)

-- | Root metadata updated (as part of the normal update process)
data RootUpdated = RootUpdated
  deriving (Typeable)

type VerificationHistory = [Either RootUpdated VerificationError]

deriving instance Show VerificationError
deriving instance Show RootUpdated
instance Exception VerificationError where displayException :: VerificationError -> String
displayException = VerificationError -> String
forall a. Pretty a => a -> String
pretty
instance Exception RootUpdated where displayException :: RootUpdated -> String
displayException = RootUpdated -> String
forall a. Pretty a => a -> String
pretty

indentedLines :: [String] -> String
indentedLines :: [String] -> String
indentedLines = [String] -> String
unlines ([String] -> String)
-> ([String] -> [String]) -> [String] -> String
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ShowS -> [String] -> [String]
forall a b. (a -> b) -> [a] -> [b]
map (String
"  " String -> ShowS
forall a. [a] -> [a] -> [a]
++)

instance Pretty VerificationError where
  pretty :: VerificationError -> String
pretty (VerificationErrorSignatures TargetPath
file Integer
threshold [KeyId]
trusted [KeyId]
sigs) =
      TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" does not have enough signatures signed with the appropriate keys\n"
   String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
"Expected at least " String -> ShowS
forall a. [a] -> [a] -> [a]
++ Integer -> String
forall a. Show a => a -> String
show Integer
threshold  String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" signatures from:\n"
   String -> ShowS
forall a. [a] -> [a] -> [a]
++ [String] -> String
indentedLines ((KeyId -> String) -> [KeyId] -> [String]
forall a b. (a -> b) -> [a] -> [b]
map KeyId -> String
keyIdString [KeyId]
trusted)
   String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
"Found signatures from:\n"
   String -> ShowS
forall a. [a] -> [a] -> [a]
++ [String] -> String
indentedLines ((KeyId -> String) -> [KeyId] -> [String]
forall a b. (a -> b) -> [a] -> [b]
map KeyId -> String
keyIdString [KeyId]
sigs)
  pretty (VerificationErrorExpired TargetPath
file) =
      TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" is expired"
  pretty (VerificationErrorVersion TargetPath
file) =
      String
"Version of " String -> ShowS
forall a. [a] -> [a] -> [a]
++ TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" is less than the previous version"
  pretty (VerificationErrorFileInfo TargetPath
file) =
      String
"Invalid hash for " String -> ShowS
forall a. [a] -> [a] -> [a]
++ TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file
  pretty (VerificationErrorUnknownTarget TargetPath
file) =
      TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" not found in corresponding target metadata"
  pretty (VerificationErrorMissingSHA256 TargetPath
file) =
      String
"Missing SHA256 hash for " String -> ShowS
forall a. [a] -> [a] -> [a]
++ TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file
  pretty (VerificationErrorDeserialization TargetPath
file DeserializationError
err) =
      String
"Could not deserialize " String -> ShowS
forall a. [a] -> [a] -> [a]
++ TargetPath -> String
forall a. Pretty a => a -> String
pretty TargetPath
file String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
": " String -> ShowS
forall a. [a] -> [a] -> [a]
++ DeserializationError -> String
forall a. Pretty a => a -> String
pretty DeserializationError
err
  pretty (VerificationErrorLoop VerificationHistory
es) =
      String
"Verification loop. Errors in order:\n"
   String -> ShowS
forall a. [a] -> [a] -> [a]
++ [String] -> String
indentedLines ((Either RootUpdated VerificationError -> String)
-> VerificationHistory -> [String]
forall a b. (a -> b) -> [a] -> [b]
map ((RootUpdated -> String)
-> (VerificationError -> String)
-> Either RootUpdated VerificationError
-> String
forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either RootUpdated -> String
forall a. Pretty a => a -> String
pretty VerificationError -> String
forall a. Pretty a => a -> String
pretty) VerificationHistory
es)

instance Pretty RootUpdated where
  pretty :: RootUpdated -> String
pretty RootUpdated
RootUpdated = String
"Root information updated"

-- | Role verification
--
-- NOTE: We throw an error when the version number _decreases_, but allow it
-- to be the same. This is sufficient: the file number is there so that
-- attackers cannot replay old files. It cannot protect against freeze attacks
-- (that's what the expiry date is for), so "replaying" the same file is not
-- a problem. If an attacker changes the contents of the file but not the
-- version number we have an inconsistent situation, but this is not something
-- we need to worry about: in this case the attacker will need to resign the
-- file or otherwise the signature won't match, and if the attacker has
-- compromised the key then he might just as well increase the version number
-- and resign.
--
-- NOTE 2: We are not actually verifying the signatures _themselves_ here
-- (we did that when we parsed the JSON). We are merely verifying the provenance
-- of the keys.
verifyRole' :: forall a. HasHeader a
            => Trusted (RoleSpec a)     -- ^ For signature validation
            -> TargetPath               -- ^ File source (for error messages)
            -> Maybe FileVersion        -- ^ Previous version (if available)
            -> Maybe UTCTime            -- ^ Time now (if checking expiry)
            -> Signed a -> Either VerificationError (SignaturesVerified a)
verifyRole' :: forall a.
HasHeader a =>
Trusted (RoleSpec a)
-> TargetPath
-> Maybe FileVersion
-> Maybe UTCTime
-> Signed a
-> Either VerificationError (SignaturesVerified a)
verifyRole' (Trusted (RoleSpec a) -> RoleSpec a
forall a. Trusted a -> a
trusted -> RoleSpec{roleSpecThreshold :: forall a. RoleSpec a -> KeyThreshold
roleSpecThreshold = KeyThreshold Int54
threshold, [Some PublicKey]
roleSpecKeys :: [Some PublicKey]
roleSpecKeys :: forall a. RoleSpec a -> [Some PublicKey]
..})
            TargetPath
targetPath
            Maybe FileVersion
mPrev
            Maybe UTCTime
mNow
            Signed{signatures :: forall a. Signed a -> Signatures
signatures = Signatures [Signature]
sigs, a
signed :: a
signed :: forall a. Signed a -> a
..} =
    Except VerificationError (SignaturesVerified a)
-> Either VerificationError (SignaturesVerified a)
forall e a. Except e a -> Either e a
runExcept Except VerificationError (SignaturesVerified a)
go
  where
    go :: Except VerificationError (SignaturesVerified a)
    go :: Except VerificationError (SignaturesVerified a)
go = do
      -- Verify expiry date
      case Maybe UTCTime
mNow of
        Just UTCTime
now ->
          Bool
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (UTCTime -> FileExpires -> Bool
isExpired UTCTime
now (LensLike' (Const FileExpires) a FileExpires -> a -> FileExpires
forall a s. LensLike' (Const a) s a -> s -> a
Lens.get LensLike' (Const FileExpires) a FileExpires
forall a. HasHeader a => Lens' a FileExpires
Lens' a FileExpires
fileExpires a
signed)) (ExceptT VerificationError Identity ()
 -> ExceptT VerificationError Identity ())
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$
            VerificationError -> ExceptT VerificationError Identity ()
forall a. VerificationError -> ExceptT VerificationError Identity a
forall e (m :: * -> *) a. MonadError e m => e -> m a
throwError (VerificationError -> ExceptT VerificationError Identity ())
-> VerificationError -> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$ TargetPath -> VerificationError
VerificationErrorExpired TargetPath
targetPath
        Maybe UTCTime
_otherwise ->
          () -> ExceptT VerificationError Identity ()
forall a. a -> ExceptT VerificationError Identity a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

      -- Verify timestamp
      case Maybe FileVersion
mPrev of
        Maybe FileVersion
Nothing   -> () -> ExceptT VerificationError Identity ()
forall a. a -> ExceptT VerificationError Identity a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
        Just FileVersion
prev ->
          Bool
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (LensLike' (Const FileVersion) a FileVersion -> a -> FileVersion
forall a s. LensLike' (Const a) s a -> s -> a
Lens.get LensLike' (Const FileVersion) a FileVersion
forall a. HasHeader a => Lens' a FileVersion
Lens' a FileVersion
fileVersion a
signed FileVersion -> FileVersion -> Bool
forall a. Ord a => a -> a -> Bool
< FileVersion
prev) (ExceptT VerificationError Identity ()
 -> ExceptT VerificationError Identity ())
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$
            VerificationError -> ExceptT VerificationError Identity ()
forall a. VerificationError -> ExceptT VerificationError Identity a
forall e (m :: * -> *) a. MonadError e m => e -> m a
throwError (VerificationError -> ExceptT VerificationError Identity ())
-> VerificationError -> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$ TargetPath -> VerificationError
VerificationErrorVersion TargetPath
targetPath

      -- Verify signatures
      -- NOTE: We only need to verify the keys that were used; if the signature
      -- was invalid we would already have thrown an error constructing Signed.
      -- (Similarly, if two signatures were made by the same key, the FromJSON
      -- instance for Signatures would have thrown an error.)
      let nSigs :: Int
nSigs = [Signature] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length ((Signature -> Bool) -> [Signature] -> [Signature]
forall a. (a -> Bool) -> [a] -> [a]
filter Signature -> Bool
isRoleSpecKey [Signature]
sigs)
      Bool
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Int
nSigs Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int54 -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int54
threshold) (ExceptT VerificationError Identity ()
 -> ExceptT VerificationError Identity ())
-> ExceptT VerificationError Identity ()
-> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$
        VerificationError -> ExceptT VerificationError Identity ()
forall a. VerificationError -> ExceptT VerificationError Identity a
forall e (m :: * -> *) a. MonadError e m => e -> m a
throwError (VerificationError -> ExceptT VerificationError Identity ())
-> VerificationError -> ExceptT VerificationError Identity ()
forall a b. (a -> b) -> a -> b
$ TargetPath -> Integer -> [KeyId] -> [KeyId] -> VerificationError
VerificationErrorSignatures TargetPath
targetPath (Int54 -> Integer
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int54
threshold) [KeyId]
trustedKeys [KeyId]
signingKeys

      -- Everything is A-OK!
      SignaturesVerified a
-> Except VerificationError (SignaturesVerified a)
forall a. a -> ExceptT VerificationError Identity a
forall (m :: * -> *) a. Monad m => a -> m a
return (SignaturesVerified a
 -> Except VerificationError (SignaturesVerified a))
-> SignaturesVerified a
-> Except VerificationError (SignaturesVerified a)
forall a b. (a -> b) -> a -> b
$ a -> SignaturesVerified a
forall a. a -> SignaturesVerified a
SignaturesVerified a
signed

    isRoleSpecKey :: Signature -> Bool
    isRoleSpecKey :: Signature -> Bool
isRoleSpecKey Signature{ByteString
Some PublicKey
signature :: ByteString
signatureKey :: Some PublicKey
signature :: Signature -> ByteString
signatureKey :: Signature -> Some PublicKey
..} = Some PublicKey
signatureKey Some PublicKey -> [Some PublicKey] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Some PublicKey]
roleSpecKeys

    trustedKeys, signingKeys :: [KeyId]
    trustedKeys :: [KeyId]
trustedKeys = (Some PublicKey -> KeyId) -> [Some PublicKey] -> [KeyId]
forall a b. (a -> b) -> [a] -> [b]
map Some PublicKey -> KeyId
forall (key :: * -> *). HasKeyId key => Some key -> KeyId
someKeyId [Some PublicKey]
roleSpecKeys
    signingKeys :: [KeyId]
signingKeys = (Signature -> KeyId) -> [Signature] -> [KeyId]
forall a b. (a -> b) -> [a] -> [b]
map (Some PublicKey -> KeyId
forall (key :: * -> *). HasKeyId key => Some key -> KeyId
someKeyId (Some PublicKey -> KeyId)
-> (Signature -> Some PublicKey) -> Signature -> KeyId
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Signature -> Some PublicKey
signatureKey) [Signature]
sigs

-- | Variation on 'verifyRole' that uses key IDs rather than keys
--
-- This is used during the bootstrap process.
--
-- See <http://en.wikipedia.org/wiki/Public_key_fingerprint>.
verifyFingerprints :: [KeyId]
                   -> KeyThreshold
                   -> TargetPath      -- ^ For error messages
                   -> Signed Root
                   -> Either VerificationError (SignaturesVerified Root)
verifyFingerprints :: [KeyId]
-> KeyThreshold
-> TargetPath
-> Signed Root
-> Either VerificationError (SignaturesVerified Root)
verifyFingerprints [KeyId]
fingerprints
                   (KeyThreshold Int54
threshold)
                   TargetPath
targetPath
                   Signed{signatures :: forall a. Signed a -> Signatures
signatures = Signatures [Signature]
sigs, Root
signed :: forall a. Signed a -> a
signed :: Root
..} =
    if [KeyId] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length ((KeyId -> Bool) -> [KeyId] -> [KeyId]
forall a. (a -> Bool) -> [a] -> [a]
filter KeyId -> Bool
isTrustedKey [KeyId]
signingKeys) Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int54 -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int54
threshold
      then SignaturesVerified Root
-> Either VerificationError (SignaturesVerified Root)
forall a b. b -> Either a b
Right (SignaturesVerified Root
 -> Either VerificationError (SignaturesVerified Root))
-> SignaturesVerified Root
-> Either VerificationError (SignaturesVerified Root)
forall a b. (a -> b) -> a -> b
$ Root -> SignaturesVerified Root
forall a. a -> SignaturesVerified a
SignaturesVerified Root
signed
      else VerificationError
-> Either VerificationError (SignaturesVerified Root)
forall a b. a -> Either a b
Left (VerificationError
 -> Either VerificationError (SignaturesVerified Root))
-> VerificationError
-> Either VerificationError (SignaturesVerified Root)
forall a b. (a -> b) -> a -> b
$ TargetPath -> Integer -> [KeyId] -> [KeyId] -> VerificationError
VerificationErrorSignatures TargetPath
targetPath (Int54 -> Integer
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int54
threshold) [KeyId]
fingerprints [KeyId]
signingKeys
  where
    signingKeys :: [KeyId]
    signingKeys :: [KeyId]
signingKeys = (Signature -> KeyId) -> [Signature] -> [KeyId]
forall a b. (a -> b) -> [a] -> [b]
map (Some PublicKey -> KeyId
forall (key :: * -> *). HasKeyId key => Some key -> KeyId
someKeyId (Some PublicKey -> KeyId)
-> (Signature -> Some PublicKey) -> Signature -> KeyId
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Signature -> Some PublicKey
signatureKey) [Signature]
sigs

    isTrustedKey :: KeyId -> Bool
    isTrustedKey :: KeyId -> Bool
isTrustedKey KeyId
key = KeyId
key KeyId -> [KeyId] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [KeyId]
fingerprints