1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
{- git-annex crypto
-
- Currently using gpg; could later be modified to support different
- crypto backends if neccessary.
-
- Copyright 2011-2014 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE Rank2Types #-}
module Crypto (
Cipher,
KeyIds(..),
EncKey,
StorableCipher(..),
genEncryptedCipher,
genSharedCipher,
updateEncryptedCipher,
describeCipher,
decryptCipher,
encryptKey,
isEncKey,
feedFile,
feedBytes,
readBytes,
encrypt,
decrypt,
getGpgEncParams,
prop_HmacSha1WithCipher_sane
) where
import qualified Data.ByteString.Lazy as L
import Data.ByteString.UTF8 (fromString)
import qualified Data.Map as M
import Control.Monad.IO.Class
import Common.Annex
import qualified Utility.Gpg as Gpg
import Types.Key
import Types.Crypto
import Types.Remote
{- The beginning of a Cipher is used for MAC'ing; the remainder is used
- as the GPG symmetric encryption passphrase when using the hybrid
- scheme. Note that the cipher itself is base-64 encoded, hence the
- string is longer than 'cipherSize': 683 characters, padded to 684.
-
- The 256 first characters that feed the MAC represent at best 192
- bytes of entropy. However that's more than enough for both the
- default MAC algorithm, namely HMAC-SHA1, and the "strongest"
- currently supported, namely HMAC-SHA512, which respectively need
- (ideally) 64 and 128 bytes of entropy.
-
- The remaining characters (320 bytes of entropy) is enough for GnuPG's
- symetric cipher; unlike weaker public key crypto, the key does not
- need to be too large.
-}
cipherBeginning :: Int
cipherBeginning = 256
cipherSize :: Int
cipherSize = 512
cipherPassphrase :: Cipher -> String
cipherPassphrase (Cipher c) = drop cipherBeginning c
cipherPassphrase (MacOnlyCipher _) = error "MAC-only cipher"
cipherMac :: Cipher -> String
cipherMac (Cipher c) = take cipherBeginning c
cipherMac (MacOnlyCipher c) = c
{- Creates a new Cipher, encrypted to the specified key id. -}
genEncryptedCipher :: String -> EncryptedCipherVariant -> Bool -> IO StorableCipher
genEncryptedCipher keyid variant highQuality = do
ks <- Gpg.findPubKeys keyid
random <- Gpg.genRandom highQuality size
encryptCipher (mkCipher random) variant ks
where
(mkCipher, size) = case variant of
Hybrid -> (Cipher, cipherSize) -- used for MAC + symmetric
PubKey -> (MacOnlyCipher, cipherBeginning) -- only used for MAC
{- Creates a new, shared Cipher. -}
genSharedCipher :: Bool -> IO StorableCipher
genSharedCipher highQuality =
SharedCipher <$> Gpg.genRandom highQuality cipherSize
{- Updates an existing Cipher, re-encrypting it to add or remove keyids,
- depending on whether the first component is True or False. -}
updateEncryptedCipher :: [(Bool, String)] -> StorableCipher -> IO StorableCipher
updateEncryptedCipher _ SharedCipher{} = error "Cannot update shared cipher"
updateEncryptedCipher [] encipher = return encipher
updateEncryptedCipher newkeys encipher@(EncryptedCipher _ variant (KeyIds ks)) = do
dropKeys <- listKeyIds [ k | (False, k) <- newkeys ]
forM_ dropKeys $ \k -> unless (k `elem` ks) $
error $ "Key " ++ k ++ " was not present; cannot remove."
addKeys <- listKeyIds [ k | (True, k) <- newkeys ]
let ks' = (addKeys ++ ks) \\ dropKeys
when (null ks') $
error "Cannot remove the last key."
cipher <- decryptCipher encipher
encryptCipher cipher variant $ KeyIds ks'
where
listKeyIds = concat <$$> mapM (keyIds <$$> Gpg.findPubKeys)
describeCipher :: StorableCipher -> String
describeCipher (SharedCipher _) = "shared cipher"
describeCipher (EncryptedCipher _ variant (KeyIds ks)) =
scheme ++ " with gpg " ++ keys ks ++ " " ++ unwords ks
where
scheme = case variant of
Hybrid -> "hybrid cipher"
PubKey -> "pubkey crypto"
keys [_] = "key"
keys _ = "keys"
{- Encrypts a Cipher to the specified KeyIds. -}
encryptCipher :: Cipher -> EncryptedCipherVariant -> KeyIds -> IO StorableCipher
encryptCipher c variant (KeyIds ks) = do
-- gpg complains about duplicate recipient keyids
let ks' = nub $ sort ks
let params = Gpg.pkEncTo ks' ++ Gpg.stdEncryptionParams False
encipher <- Gpg.pipeStrict params cipher
return $ EncryptedCipher encipher variant (KeyIds ks')
where
cipher = case c of
Cipher x -> x
MacOnlyCipher x -> x
{- Decrypting an EncryptedCipher is expensive; the Cipher should be cached. -}
decryptCipher :: StorableCipher -> IO Cipher
decryptCipher (SharedCipher t) = return $ Cipher t
decryptCipher (EncryptedCipher t variant _) =
mkCipher <$> Gpg.pipeStrict [ Param "--decrypt" ] t
where
mkCipher = case variant of
Hybrid -> Cipher
PubKey -> MacOnlyCipher
type EncKey = Key -> Key
{- Generates an encrypted form of a Key. The encryption does not need to be
- reversable, nor does it need to be the same type of encryption used
- on content. It does need to be repeatable. -}
encryptKey :: Mac -> Cipher -> EncKey
encryptKey mac c k = stubKey
{ keyName = macWithCipher mac c (key2file k)
, keyBackendName = encryptedBackendNamePrefix ++ showMac mac
}
encryptedBackendNamePrefix :: String
encryptedBackendNamePrefix = "GPG"
isEncKey :: Key -> Bool
isEncKey k = encryptedBackendNamePrefix `isPrefixOf` keyBackendName k
type Feeder = Handle -> IO ()
type Reader m a = Handle -> m a
feedFile :: FilePath -> Feeder
feedFile f h = L.hPut h =<< L.readFile f
feedBytes :: L.ByteString -> Feeder
feedBytes = flip L.hPut
readBytes :: (MonadIO m) => (L.ByteString -> m a) -> Reader m a
readBytes a h = liftIO (L.hGetContents h) >>= a
{- Runs a Feeder action, that generates content that is symmetrically
- encrypted with the Cipher (unless it is empty, in which case
- public-key encryption is used) using the given gpg options, and then
- read by the Reader action. Note: For public-key encryption,
- recipients MUST be included in 'params' (for instance using
- 'getGpgEncParams'). -}
encrypt :: (MonadIO m, MonadMask m) => [CommandParam] -> Cipher -> Feeder -> Reader m a -> m a
encrypt params cipher = case cipher of
Cipher{} -> Gpg.feedRead (params ++ Gpg.stdEncryptionParams True) $
cipherPassphrase cipher
MacOnlyCipher{} -> Gpg.pipeLazy $ params ++ Gpg.stdEncryptionParams False
{- Runs a Feeder action, that generates content that is decrypted with the
- Cipher (or using a private key if the Cipher is empty), and read by the
- Reader action. -}
decrypt :: (MonadIO m, MonadMask m) => Cipher -> Feeder -> Reader m a -> m a
decrypt cipher = case cipher of
Cipher{} -> Gpg.feedRead [Param "--decrypt"] $ cipherPassphrase cipher
MacOnlyCipher{} -> Gpg.pipeLazy [Param "--decrypt"]
macWithCipher :: Mac -> Cipher -> String -> String
macWithCipher mac c = macWithCipher' mac (cipherMac c)
macWithCipher' :: Mac -> String -> String -> String
macWithCipher' mac c s = calcMac mac (fromString c) (fromString s)
{- Ensure that macWithCipher' returns the same thing forevermore. -}
prop_HmacSha1WithCipher_sane :: Bool
prop_HmacSha1WithCipher_sane = known_good == macWithCipher' HmacSha1 "foo" "bar"
where
known_good = "46b4ec586117154dacd49d664e5d63fdc88efb51"
{- Return some options suitable for GnuPG encryption, symmetric or not. -}
class LensGpgEncParams a where getGpgEncParams :: a -> [CommandParam]
{- Extract the GnuPG options from a pair of a Remote Config and a Remote
- Git Config. -}
instance LensGpgEncParams (RemoteConfig, RemoteGitConfig) where
getGpgEncParams (c,gc) = map Param (remoteAnnexGnupgOptions gc) ++ getGpgEncParams c
where
{- Extract the GnuPG options from a Remote Config, ignoring any
- git config settings. (Which is ok if the remote is just being set up
- and so doesn't have any.)
-
- If the remote is configured to use public-key encryption,
- look up the recipient keys and add them to the option list.-}
instance LensGpgEncParams RemoteConfig where
getGpgEncParams c = case M.lookup "encryption" c of
Just "pubkey" -> Gpg.pkEncTo $ maybe [] (split ",") $ M.lookup "cipherkeys" c
_ -> []
{- Extract the GnuPG options from a Remote. -}
instance LensGpgEncParams (RemoteA a) where
getGpgEncParams r = getGpgEncParams (config r, gitconfig r)
|
