1 files changed, 29 insertions, 0 deletions

diff --git a/lib/OpenPGP.hs b/lib/OpenPGP.hs
index aeadc47..7a1508e 100644
--- a/lib/OpenPGP.hs
+++ b/lib/OpenPGP.hs
@@ -127,6 +127,35 @@ secret_key_fields RSA_S   = secret_key_fields RSA
 secret_key_fields ELGAMAL = ['x']
 secret_key_fields DSA     = ['x']
 
+-- Need this seperate for trailer calculation
+signature_packet_start :: Packet -> LZ.ByteString
+signature_packet_start (SignaturePacket {
+        version = 4,
+        signature_type = signature_type,
+        key_algorithm = key_algorithm,
+        hash_algorithm = hash_algorithm,
+        hashed_subpackets = hashed_subpackets
+}) =
+        LZ.concat $ [
+                encode (0x04 :: Word8),
+                encode signature_type,
+                encode key_algorithm,
+                encode hash_algorithm,
+                encode ((fromIntegral $ LZ.length hashed_subs) :: Word16),
+                hashed_subs
+        ]
+        where hashed_subs = LZ.concat $ map encode hashed_subpackets
+
+-- The trailer is just the top of the body plus some crap
+calculate_signature_trailer :: Packet -> LZ.ByteString
+calculate_signature_trailer p =
+        LZ.concat [
+                signature_packet_start p,
+                encode (0x04 :: Word8),
+                encode (0xff :: Word8),
+                encode ((fromIntegral (LZ.length $ signature_packet_start p)) :: Word32)
+        ]
+
 parse_packet :: Word8 -> Get Packet
 -- SignaturePacket, http://tools.ietf.org/html/rfc4880#section-5.2
 parse_packet  2 = do