@@ -4,73 +4,218 @@
4 Stability: beta
4 Stability: beta
5 Portability: portable
5 Portability: portable
7− Obtain entropy from system sources or x86 RDRAND when available.
7+ Obtain entropy from system sources.
8+ Currently, windows and *nix systems with a /dev/urandom are supported.
9− Currently supporting:
19+import Control.Monad (liftM, when)
20+import Data.ByteString as B
21+import System.IO (openFile, hClose, IOMode(..), Handle, withBinaryFile)
23+#if defined(isWindows)
24+{- C example for windows rng - taken from a blog, can't recall which one but thank you!
11− - Windows via CryptoAPI
25+ #include <Windows.h>
12− - *nix systems via @\/dev\/urandom@
26+ #include <Wincrypt.h>
13− - Includes QNX
27+ ...
14− - ghcjs/browser via JavaScript crypto API.
28+ //
29+ // DISCLAIMER: Don't forget to check your error codes!!
30+ // I am not checking as to make the example simple...
32+ HCRYPTPROV hCryptCtx = NULL;
33+ BYTE randomArray[128];
35+ CryptAcquireContext(&hCryptCtx, NULL, MS_DEF_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
36+ CryptGenRandom(hCryptCtx, 128, randomArray);
37+ CryptReleaseContext(hCryptCtx, 0);
17−module System.Entropy
40+import Data.ByteString.Internal as BI
18− ( getEntropy,
41+import Data.Int (Int32)
19− getHardwareEntropy,
42+import Data.Word (Word32, Word8)
20− CryptHandle,
43+import Foreign.C.String (CString, withCString)
21− openHandle,
44+import Foreign.C.Types
22− hGetEntropy,
45+import Foreign.Ptr (Ptr, nullPtr, castPtr)
23− closeHandle
46+import Foreign.Marshal.Alloc (alloca)
24− ) where
47+import Foreign.Marshal.Utils (toBool)
25−
48+import Foreign.Storable (peek)
26−#ifdef ghcjs_HOST_OS
49+
27−import System.EntropyGhcjs
50+#ifdef arch_x86_64
28−#elif defined(isWindows)
51+foreign import ccall unsafe "cpu_has_rdrand"
29−import System.EntropyWindows
52+ c_cpu_has_rdrand :: IO CInt
31−import System.EntropyNix
54+foreign import ccall unsafe "get_rand_bytes"
55+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
57+cpuHasRdRand :: IO Bool
58+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
34−import qualified Data.ByteString as B
61+newtype CryptHandle
35−import Control.Exception (bracket)
62+ = CH Word32
37−-- |Get a specific number of bytes of cryptographically
67+-- Define the constants we need from WinCrypt.h
38−-- secure random data using the *system-specific* sources.
68+msDefProv :: String
39−-- (As of 0.4. Versions <0.4 mixed system and hardware sources)
69+msDefProv = "Microsoft Base Cryptographic Provider v1.0"
40−--
70+provRSAFull :: Word32
41−-- The returned random value is considered cryptographically secure but not true entropy.
71+provRSAFull = fromIntegral 1
42−--
72+cryptVerifyContext :: Word32
43−-- On some platforms this requires a file handle which can lead to resource
73+cryptVerifyContext = fromIntegral 0xF0000000
44−-- exhaustion in some situations.
74+
45−getEntropy :: Int -- ^ Number of bytes
75+-- Declare the required CryptoAPI imports
76+foreign import stdcall unsafe "CryptAcquireContextA"
77+ c_cryptAcquireCtx :: Ptr Word32 -> CString -> CString -> Word32 -> Word32 -> IO Int32
78+foreign import stdcall unsafe "CryptGenRandom"
79+ c_cryptGenRandom :: Word32 -> Word32 -> Ptr Word8 -> IO Int32
80+foreign import stdcall unsafe "CryptReleaseContext"
81+ c_cryptReleaseCtx :: Word32 -> Word32 -> IO Int32
83+cryptAcquireCtx :: IO Word32
85+ alloca $ \handlePtr ->
86+ withCString msDefProv $ \provName -> do
87+ stat <- c_cryptAcquireCtx handlePtr nullPtr provName (fromIntegral 1) (fromIntegral cryptVerifyContext)
90+ else fail "c_cryptAcquireCtx"
46− -> IO B.ByteString
92+cryptGenRandom :: Word32 -> Int -> IO B.ByteString
47−getEntropy = bracket openHandle closeHandle . flip hGetEntropy
93+cryptGenRandom h i =
48−
94+ BI.create i $ \c_buffer -> do
49−-- |Get a specific number of bytes of cryptographically
95+ stat <- c_cryptGenRandom (fromIntegral h) (fromIntegral i) c_buffer
50−-- secure random data using a supported *hardware* random bit generator.
96+ if (toBool stat)
52−-- If there is no hardware random number generator then @Nothing@ is returned.
98+ else fail "c_cryptGenRandom"
53−-- If any call returns non-Nothing then it should never be @Nothing@ unless
99+
54−-- there has been a hardware failure.
100+cryptReleaseCtx :: Word32 -> IO ()
55−--
101+cryptReleaseCtx h = do
56−-- If trust of the CPU allows it and no context switching is important,
102+ stat <- c_cryptReleaseCtx h 0
57−-- a bias to the hardware rng with system rng as fall back is trivial:
103+ if (toBool stat)
59−-- @
105+ else fail "c_cryptReleaseCtx"
60−-- let fastRandom nr = maybe (getEntropy nr) pure =<< getHardwareEntropy nr
106+
61−-- @
107+-- |Inefficiently get a specific number of bytes of cryptographically
62−--
108+-- secure random data using the system-specific facilities.
63−-- The old, @<0.4@, behavior is possible using @xor@ from 'Data.Bits':
65−-- @
110+-- This function will return zero bytes
66−-- let oldRandom nr =
111+-- on platforms without a secure RNG!
67−-- do hwRnd <- maybe (replicate nr 0) BS.unpack <$> getHardwareEntropy nr
112+getEntropy :: Int -> IO B.ByteString
68−-- sysRnd <- BS.unpack <$> getEntropy nr
113+getEntropy n = do
69−-- pure $ BS.pack $ zipWith xor sysRnd hwRnd
114+#ifdef arch_x86_64
70−-- @
115+ b <- cpuHasRdRand
116+ if b then hGetEntropy UseRdRand n
119+ h <- cryptAcquireCtx
120+ bs <- cryptGenRandom h n
125+-- |Open a handle from which random data can be read
126+openHandle :: IO CryptHandle
130+ if b then return UseRdRand
133+ liftM CH cryptAcquireCtx
135+-- |Close the `CryptHandle`
136+closeHandle (CH h) = cryptReleaseCtx h
138+-- |Read from `CryptHandle`
139+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
140+hGetEntropy (CH h) = cryptGenRandom h
142+hGetEntropy UseRdRand =
143+ B.create n $ \ptr -> do
144+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
146+ (fail "RDRand failed to gather entropy")
150+{- Not windows, assuming nix with a /dev/urandom -}
151+import Foreign.C.Types
153+import Data.ByteString.Internal as B
156+source = "/dev/urandom"
158+-- |Handle for manual resource mangement
165+-- |Open a `CryptHandle`
166+openHandle :: IO CryptHandle
170+ if b then return UseRdRand
173+ liftM CH (openFile source ReadMode)
175+-- |Close the `CryptHandle`
176+closeHandle :: CryptHandle -> IO ()
177+closeHandle (CH h) = hClose h
179+closeHandle UseRdRand = return ()
182+-- |Read random data from a `CryptHandle`
183+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
184+hGetEntropy (CH h) = B.hGet h
186+hGetEntropy UseRdRand = \n -> do
187+ B.create n $ \ptr -> do
188+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
190+ (fail "RDRand failed to gather entropy")
194+foreign import ccall unsafe "cpu_has_rdrand"
195+ c_cpu_has_rdrand :: IO CInt
197+foreign import ccall unsafe "get_rand_bytes"
198+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
200+cpuHasRdRand :: IO Bool
201+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
204+-- |Inefficiently get a specific number of bytes of cryptographically
205+-- secure random data using the system-specific facilities.
72−-- A less maliable mixing can be accomplished by replacing `xor` with a
207+-- Use '/dev/urandom' on *nix and CryptAPI when on Windows. In short,
73−-- composition of concat and cryptographic hash.
208+-- this entropy is considered "cryptographically secure" but not true
74−getHardwareEntropy :: Int -- ^ Number of bytes
209+-- entropy.
75− -> IO (Maybe B.ByteString)
210+getEntropy :: Int -> IO B.ByteString
76−getHardwareEntropy = hardwareRandom
211+getEntropy n = do
214+ if b then hGetEntropy UseRdRand n
218+ withBinaryFile source ReadMode (`B.hGet` n)