module Data.OpenPGP.Crypto (sign, verify, fingerprint) where
import Data.Word
import Data.List (find)
import Data.Map ((!))
import qualified Data.ByteString.Lazy as LZ
import qualified Data.ByteString.Lazy.UTF8 as LZ (fromString)
import Data.Binary
import Codec.Utils (fromOctets)
import qualified Codec.Encryption.RSA as RSA
import qualified Data.Digest.MD5 as MD5
import qualified Data.Digest.SHA1 as SHA1
import qualified Data.Digest.SHA256 as SHA256
import qualified Data.Digest.SHA384 as SHA384
import qualified Data.Digest.SHA512 as SHA512
import qualified Data.OpenPGP as OpenPGP
import qualified Data.BaseConvert as BaseConvert
fingerprint :: OpenPGP.Packet -> String
fingerprint p | OpenPGP.version p == 4 =
BaseConvert.toString 16 $ SHA1.toInteger $ SHA1.hash $
LZ.unpack (LZ.concat (OpenPGP.fingerprint_material p))
fingerprint p | OpenPGP.version p `elem` [2, 3] =
concatMap (BaseConvert.toString 16) $
MD5.hash $ LZ.unpack (LZ.concat (OpenPGP.fingerprint_material p))
fingerprint _ = error "Unsupported Packet version or type in fingerprint."
find_key :: OpenPGP.Message -> String -> Maybe OpenPGP.Packet
find_key (OpenPGP.Message (x@(OpenPGP.PublicKeyPacket {}):xs)) keyid =
find_key_ x xs keyid
find_key (OpenPGP.Message (x@(OpenPGP.SecretKeyPacket {}):xs)) keyid =
find_key_ x xs keyid
find_key _ _ = Nothing
find_key_ :: OpenPGP.Packet -> [OpenPGP.Packet] -> String -> Maybe OpenPGP.Packet
find_key_ x xs keyid =
if thisid == keyid then Just x else find_key (OpenPGP.Message xs) keyid
where thisid = reverse $
take (length keyid) (reverse (fingerprint x))
keyfield_as_octets :: OpenPGP.Packet -> Char -> [Word8]
keyfield_as_octets k f =
LZ.unpack $ LZ.drop 2 (encode (k' ! f))
where k' = OpenPGP.key k
emsa_pkcs1_v1_5_hash_padding :: OpenPGP.HashAlgorithm -> [Word8]
emsa_pkcs1_v1_5_hash_padding OpenPGP.MD5 = [0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10]
emsa_pkcs1_v1_5_hash_padding OpenPGP.SHA1 = [0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14]
emsa_pkcs1_v1_5_hash_padding OpenPGP.SHA256 = [0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20]
emsa_pkcs1_v1_5_hash_padding OpenPGP.SHA384 = [0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02, 0x05, 0x00, 0x04, 0x30]
emsa_pkcs1_v1_5_hash_padding OpenPGP.SHA512 = [0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05, 0x00, 0x04, 0x40]
emsa_pkcs1_v1_5_hash_padding _ =
error "Unsupported HashAlgorithm in emsa_pkcs1_v1_5_hash_padding."
hash :: OpenPGP.HashAlgorithm -> [Word8] -> [Word8]
hash OpenPGP.MD5 = MD5.hash
hash OpenPGP.SHA1 = reverse . drop 2 . LZ.unpack . encode . OpenPGP.MPI . SHA1.toInteger . SHA1.hash
hash OpenPGP.SHA256 = SHA256.hash
hash OpenPGP.SHA384 = SHA384.hash
hash OpenPGP.SHA512 = SHA512.hash
hash _ = error "Unsupported HashAlgorithm in hash."
emsa_pkcs1_v1_5_encode :: [Word8] -> Int -> OpenPGP.HashAlgorithm -> [Word8]
emsa_pkcs1_v1_5_encode m emLen algo =
[0, 1] ++ replicate (emLen length t 3) 0xff ++ [0] ++ t
where t = emsa_pkcs1_v1_5_hash_padding algo ++ hash algo m
verify :: OpenPGP.Message
-> OpenPGP.Message
-> Int
-> Bool
verify keys message sigidx =
encoded == RSA.encrypt (n, e) raw_sig
where
raw_sig = LZ.unpack $ LZ.drop 2 $ encode (OpenPGP.signature sig)
encoded = emsa_pkcs1_v1_5_encode signature_over
(length n) (OpenPGP.hash_algorithm sig)
signature_over = LZ.unpack $ dta `LZ.append` OpenPGP.trailer sig
(n, e) = (keyfield_as_octets k 'n', keyfield_as_octets k 'e')
Just k = find_key keys issuer
Just issuer = OpenPGP.signature_issuer sig
sig = sigs !! sigidx
(sigs, (OpenPGP.LiteralDataPacket {OpenPGP.content = dta}):_) =
OpenPGP.signatures_and_data message
sign :: OpenPGP.Message
-> OpenPGP.Message
-> OpenPGP.HashAlgorithm
-> String
-> Integer
-> OpenPGP.Packet
sign keys message hsh keyid timestamp =
sig {
OpenPGP.signature = OpenPGP.MPI $ toNum final,
OpenPGP.hash_head = toNum $ take 2 final
}
where
toNum l = fromOctets (256::Integer) l
final = dropWhile (==0) $ RSA.decrypt (n, d) encoded
encoded = emsa_pkcs1_v1_5_encode dta (length n) hsh
(n, d) = (keyfield_as_octets k 'n', keyfield_as_octets k 'd')
dta = LZ.unpack $ case signOver of {
OpenPGP.LiteralDataPacket {OpenPGP.content = c} -> c;
_ -> LZ.concat $ OpenPGP.fingerprint_material signOver ++ [
LZ.singleton 0xB4,
encode (fromIntegral (length firstUserID) :: Word32),
LZ.fromString firstUserID
]
} `LZ.append` OpenPGP.trailer sig
sig = let s = (findSigOrDefault (find isSignature m)) {
OpenPGP.key_algorithm = OpenPGP.RSA,
OpenPGP.hash_algorithm = hsh
} in s { OpenPGP.trailer = OpenPGP.calculate_signature_trailer s }
findSigOrDefault (Just s) = s
findSigOrDefault Nothing = OpenPGP.SignaturePacket {
OpenPGP.version = 4,
OpenPGP.key_algorithm = undefined,
OpenPGP.hash_algorithm = undefined,
OpenPGP.signature_type = defaultStype,
OpenPGP.hashed_subpackets = [
OpenPGP.SignatureCreationTimePacket $ fromIntegral timestamp,
OpenPGP.IssuerPacket keyid'
] ++ (case signOver of
OpenPGP.LiteralDataPacket {} -> []
_ -> []
),
OpenPGP.unhashed_subpackets = [],
OpenPGP.signature = undefined,
OpenPGP.trailer = undefined,
OpenPGP.hash_head = undefined
}
keyid' = reverse $ take 16 $ reverse $ fingerprint k
Just k = find_key keys keyid
Just (OpenPGP.UserIDPacket firstUserID) = find isUserID m
defaultStype = case signOver of
OpenPGP.LiteralDataPacket {OpenPGP.format = f} ->
if f == 'b' then 0x00 else 0x01
_ -> 0x13
Just signOver = find isSignable m
OpenPGP.Message m = message
isSignable (OpenPGP.LiteralDataPacket {}) = True
isSignable (OpenPGP.PublicKeyPacket {}) = True
isSignable (OpenPGP.SecretKeyPacket {}) = True
isSignable _ = False
isSignature (OpenPGP.SignaturePacket {}) = True
isSignature _ = False
isUserID (OpenPGP.UserIDPacket {}) = True
isUserID _ = False