@@ -4,218 +4,73 @@
4 Stability: beta
4 Stability: beta
5 Portability: portable
5 Portability: portable
7− Obtain entropy from system sources.
7+ Obtain entropy from system sources or x86 RDRAND when available.
8− Currently, windows and *nix systems with a /dev/urandom are supported.
19−import Control.Monad (liftM, when)
9+ Currently supporting:
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!
25− #include <Windows.h>
11+ - Windows via CryptoAPI
26− #include <Wincrypt.h>
12+ - *nix systems via @\/dev\/urandom@
27− ...
13+ - Includes QNX
28− //
14+ - ghcjs/browser via JavaScript crypto API.
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);
40−import Data.ByteString.Internal as BI
17+module System.Entropy
41−import Data.Int (Int32)
18+ ( getEntropy,
42−import Data.Word (Word32, Word8)
19+ getHardwareEntropy,
43−import Foreign.C.String (CString, withCString)
20+ CryptHandle,
44−import Foreign.C.Types
21+ openHandle,
45−import Foreign.Ptr (Ptr, nullPtr, castPtr)
46−import Foreign.Marshal.Alloc (alloca)
47−import Foreign.Marshal.Utils (toBool)
48−import Foreign.Storable (peek)
51−foreign import ccall unsafe "cpu_has_rdrand"
52− c_cpu_has_rdrand :: IO CInt
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
67−-- Define the constants we need from WinCrypt.h
69−msDefProv = "Microsoft Base Cryptographic Provider v1.0"
71−provRSAFull = fromIntegral 1
72−cryptVerifyContext :: Word32
73−cryptVerifyContext = fromIntegral 0xF0000000
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"
92−cryptGenRandom :: Word32 -> Int -> IO B.ByteString
94− BI.create i $ \c_buffer -> do
95− stat <- c_cryptGenRandom (fromIntegral h) (fromIntegral i) c_buffer
98− else fail "c_cryptGenRandom"
100−cryptReleaseCtx :: Word32 -> IO ()
101−cryptReleaseCtx h = do
102− stat <- c_cryptReleaseCtx h 0
105− else fail "c_cryptReleaseCtx"
107−-- |Inefficiently get a specific number of bytes of cryptographically
108−-- secure random data using the system-specific facilities.
110−-- This function will return zero bytes
111−-- on platforms without a secure RNG!
112−getEntropy :: Int -> IO B.ByteString
116− if b then hGetEntropy UseRdRand n
22+ hGetEntropy,
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
23+ closeHandle
138−-- |Read from `CryptHandle`
25+
139−hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
26+#ifdef ghcjs_HOST_OS
140−hGetEntropy (CH h) = cryptGenRandom h
27+import System.EntropyGhcjs
141−#ifdef arch_x86_64
28+#elif defined(isWindows)
142−hGetEntropy UseRdRand =
29+import System.EntropyWindows
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 -}
31+import System.EntropyNix
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`
34+import qualified Data.ByteString as B
176−closeHandle :: CryptHandle -> IO ()
35+import Control.Exception (bracket)
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
37+-- |Get a specific number of bytes of cryptographically
205−-- secure random data using the system-specific facilities.
38+-- secure random data using the *system-specific* sources.
39+-- (As of 0.4. Versions <0.4 mixed system and hardware sources)
207−-- Use '/dev/urandom' on *nix and CryptAPI when on Windows. In short,
208−-- this entropy is considered "cryptographically secure" but not true
41+-- The returned random value is considered cryptographically secure but not true entropy.
43+-- On some platforms this requires a file handle which can lead to resource
44+-- exhaustion in some situations.
45+getEntropy :: Int -- ^ Number of bytes
210−getEntropy :: Int -> IO B.ByteString
46+ -> IO B.ByteString
211−getEntropy n = do
47+getEntropy = bracket openHandle closeHandle . flip hGetEntropy
213− b <- cpuHasRdRand
49+-- |Get a specific number of bytes of cryptographically
214− if b then hGetEntropy UseRdRand n
50+-- secure random data using a supported *hardware* random bit generator.
216−#endif
52+-- If there is no hardware random number generator then @Nothing@ is returned.
217−{- arch_x86 -}
53+-- If any call returns non-Nothing then it should never be @Nothing@ unless
218− withBinaryFile source ReadMode (`B.hGet` n)
54+-- there has been a hardware failure.
220−{- OS Test -}
56+-- If trust of the CPU allows it and no context switching is important,
221−
57+-- a bias to the hardware rng with system rng as fall back is trivial:
60+-- let fastRandom nr = maybe (getEntropy nr) pure =<< getHardwareEntropy nr
63+-- The old, @<0.4@, behavior is possible using @xor@ from 'Data.Bits':
67+-- do hwRnd <- maybe (replicate nr 0) BS.unpack <$> getHardwareEntropy nr
68+-- sysRnd <- BS.unpack <$> getEntropy nr
69+-- pure $ BS.pack $ zipWith xor sysRnd hwRnd
72+-- A less maliable mixing can be accomplished by replacing `xor` with a
73+-- composition of concat and cryptographic hash.
74+getHardwareEntropy :: Int -- ^ Number of bytes
75+ -> IO (Maybe B.ByteString)
76+getHardwareEntropy = hardwareRandom