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
|
-- |
-- Module : Foundation.System.Entropy.Unix
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : experimental
-- Portability : Good
--
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE ForeignFunctionInterface #-}
module Foundation.System.Entropy.Unix
( EntropyCtx
, entropyOpen
, entropyGather
, entropyClose
, entropyMaximumSize
) where
import Foreign.Ptr
import Control.Exception as E
import Control.Monad
import System.IO
import System.IO.Unsafe (unsafePerformIO)
import Basement.Compat.Base
import Basement.Compat.C.Types
import Prelude (fromIntegral)
import Foundation.System.Entropy.Common
import Foundation.Numerical
data EntropyCtx =
EntropyCtx Handle
| EntropySyscall
entropyOpen :: IO EntropyCtx
entropyOpen = do
if supportSyscall
then return EntropySyscall
else do
mh <- openDev "/dev/urandom"
case mh of
Nothing -> E.throwIO EntropySystemMissing
Just h -> return $ EntropyCtx h
-- | try to fill the ptr with the amount of data required.
-- Return the number of bytes, or a negative number otherwise
entropyGather :: EntropyCtx -> Ptr Word8 -> Int -> IO Bool
entropyGather (EntropyCtx h) ptr n = gatherDevEntropy h ptr n
entropyGather EntropySyscall ptr n = (==) 0 <$> c_sysrandom_linux ptr (fromIntegral n)
entropyClose :: EntropyCtx -> IO ()
entropyClose (EntropyCtx h) = hClose h
entropyClose EntropySyscall = return ()
entropyMaximumSize :: Int
entropyMaximumSize = 4096
openDev :: [Char] -> IO (Maybe Handle)
openDev filepath = (Just `fmap` openAndNoBuffering) `E.catch` \(_ :: IOException) -> return Nothing
where openAndNoBuffering = do
h <- openBinaryFile filepath ReadMode
hSetBuffering h NoBuffering
return h
gatherDevEntropy :: Handle -> Ptr Word8 -> Int -> IO Bool
gatherDevEntropy h ptr sz = loop ptr sz `E.catch` failOnException
where
loop _ 0 = return True
loop p n = do
r <- hGetBufSome h p n
if r >= 0
then loop (p `plusPtr` r) (n - r)
else return False
failOnException :: E.IOException -> IO Bool
failOnException _ = return False
supportSyscall :: Bool
supportSyscall = unsafePerformIO ((==) 0 <$> c_sysrandom_linux nullPtr 0)
{-# NOINLINE supportSyscall #-}
-- return 0 on success, !0 for failure
foreign import ccall unsafe "foundation_sysrandom_linux"
c_sysrandom_linux :: Ptr Word8 -> CSize -> IO Int
|
