@@ -8,69 +8,242 @@
9 Currently supporting:
9 Currently supporting:
11− - Windows via CryptoAPI
11+ - Windows via CryptoAPO
12 - *nix systems via @\/dev\/urandom@
12 - *nix systems via @\/dev\/urandom@
13− - Includes QNX
13+ - QNX
14− - ghcjs/browser via JavaScript crypto API.
14+ - Xen only when RDRAND is available.
17module System.Entropy
17module System.Entropy
18− ( getEntropy,
18+ ( getEntropy
20− CryptHandle,
19+ , CryptHandle
21− openHandle,
20+ , openHandle
22− hGetEntropy,
21+ , hGetEntropy
23− closeHandle
22+ , closeHandle
26−#ifdef ghcjs_HOST_OS
25+import Control.Monad (liftM, when)
27−import System.EntropyGhcjs
26+import System.IO.Error (mkIOError, eofErrorType, ioeSetErrorString)
27+import Foreign (allocaBytes)
28+import Data.ByteString as B
28−#elif defined(isWindows)
30+#if defined(isWindows)
29−import System.EntropyWindows
31+{- C example for windows rng - taken from a blog, can't recall which one but thank you!
30−#else
32+ #include <Windows.h>
31−import System.EntropyNix
33+ #include <Wincrypt.h>
36+ // DISCLAIMER: Don't forget to check your error codes!!
37+ // I am not checking as to make the example simple...
39+ HCRYPTPROV hCryptCtx = NULL;
40+ BYTE randomArray[128];
42+ CryptAcquireContext(&hCryptCtx, NULL, MS_DEF_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
43+ CryptGenRandom(hCryptCtx, 128, randomArray);
44+ CryptReleaseContext(hCryptCtx, 0);
47+import Data.ByteString.Internal as BI
48+import Data.Int (Int32)
49+import Data.Word (Word32, Word8)
50+import Foreign.C.String (CString, withCString)
51+import Foreign.C.Types
52+import Foreign.Ptr (Ptr, nullPtr, castPtr)
53+import Foreign.Marshal.Alloc (alloca)
54+import Foreign.Marshal.Utils (toBool)
55+import Foreign.Storable (peek)
58+foreign import ccall unsafe "cpu_has_rdrand"
59+ c_cpu_has_rdrand :: IO CInt
61+foreign import ccall unsafe "get_rand_bytes"
62+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
64+cpuHasRdRand :: IO Bool
65+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
34−import qualified Data.ByteString as B
68+data CryptHandle
35−import Control.Exception (bracket)
69+ = CH Word32
37−-- |Get a specific number of bytes of cryptographically
74+-- Define the constants we need from WinCrypt.h
38−-- secure random data using the *system-specific* sources.
75+msDefProv :: String
39−-- (As of 0.4. Versions <0.4 mixed system and hardware sources)
76+msDefProv = "Microsoft Base Cryptographic Provider v1.0"
40−--
77+provRSAFull :: Word32
41−-- The returned random value is considered cryptographically secure but not true entropy.
78+provRSAFull = fromIntegral 1
42−--
79+cryptVerifyContext :: Word32
43−-- On some platforms this requires a file handle which can lead to resource
80+cryptVerifyContext = fromIntegral 0xF0000000
44−-- exhaustion in some situations.
81+
45−getEntropy :: Int -- ^ Number of bytes
82+-- Declare the required CryptoAPI imports
83+foreign import stdcall unsafe "CryptAcquireContextA"
84+ c_cryptAcquireCtx :: Ptr Word32 -> CString -> CString -> Word32 -> Word32 -> IO Int32
85+foreign import stdcall unsafe "CryptGenRandom"
86+ c_cryptGenRandom :: Word32 -> Word32 -> Ptr Word8 -> IO Int32
87+foreign import stdcall unsafe "CryptReleaseContext"
88+ c_cryptReleaseCtx :: Word32 -> Word32 -> IO Int32
90+cryptAcquireCtx :: IO Word32
92+ alloca $ \handlePtr ->
93+ withCString msDefProv $ \provName -> do
94+ stat <- c_cryptAcquireCtx handlePtr nullPtr provName (fromIntegral 1) (fromIntegral cryptVerifyContext)
97+ else fail "c_cryptAcquireCtx"
46− -> IO B.ByteString
99+cryptGenRandom :: Word32 -> Int -> IO B.ByteString
47−getEntropy = bracket openHandle closeHandle . flip hGetEntropy
100+cryptGenRandom h i =
48−
101+ BI.create i $ \c_buffer -> do
49−-- |Get a specific number of bytes of cryptographically
102+ stat <- c_cryptGenRandom (fromIntegral h) (fromIntegral i) c_buffer
50−-- secure random data using a supported *hardware* random bit generator.
103+ if (toBool stat)
52−-- If there is no hardware random number generator then @Nothing@ is returned.
105+ else fail "c_cryptGenRandom"
53−-- If any call returns non-Nothing then it should never be @Nothing@ unless
106+
54−-- there has been a hardware failure.
107+cryptReleaseCtx :: Word32 -> IO ()
55−--
108+cryptReleaseCtx h = do
56−-- If trust of the CPU allows it and no context switching is important,
109+ stat <- c_cryptReleaseCtx h 0
57−-- a bias to the hardware rng with system rng as fall back is trivial:
110+ if (toBool stat)
59−-- @
112+ else fail "c_cryptReleaseCtx"
60−-- let fastRandom nr = maybe (getEntropy nr) pure =<< getHardwareEntropy nr
113+
61−-- @
114+-- |Inefficiently get a specific number of bytes of cryptographically
62−--
115+-- secure random data using the system-specific facilities.
63−-- The old, @<0.4@, behavior is possible using @xor@ from 'Data.Bits':
65−-- @
117+-- This function will return zero bytes
66−-- let oldRandom nr =
118+-- on platforms without a secure RNG!
67−-- do hwRnd <- maybe (replicate nr 0) BS.unpack <$> getHardwareEntropy nr
119+getEntropy :: Int -> IO B.ByteString
68−-- sysRnd <- BS.unpack <$> getEntropy nr
120+getEntropy n = do
69−-- pure $ BS.pack $ zipWith xor sysRnd hwRnd
121+#ifdef HAVE_RDRAND
70−-- @
122+ b <- cpuHasRdRand
123+ if b then hGetEntropy UseRdRand n
126+ h <- cryptAcquireCtx
127+ bs <- cryptGenRandom h n
132+-- |Open a handle from which random data can be read
133+openHandle :: IO CryptHandle
137+ if b then return UseRdRand
140+ liftM CH cryptAcquireCtx
142+-- |Close the `CryptHandle`
143+closeHandle (CH h) = cryptReleaseCtx h
145+-- |Read from `CryptHandle`
146+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
147+hGetEntropy (CH h) n = cryptGenRandom h n
149+hGetEntropy UseRdRand n =
150+ B.create n $ \ptr -> do
151+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
153+ (fail "RDRand failed to gather entropy")
157+{- Not windows, assuming nix with a /dev/urandom -}
159+import Foreign.C.Types
160+import Data.ByteString.Internal as B
162+data CryptHandle = UseRdRand -- or die trying
164+import System.Posix (openFd, closeFd, fdReadBuf, OpenMode(..), defaultFileFlags, Fd)
167+source = "/dev/urandom"
169+-- |Handle for manual resource mangement
177+-- |Open a `CryptHandle`
178+openHandle :: IO CryptHandle
182+ if b then return UseRdRand
186+ error "entropy: On halvm there is no entropy other than RDRAND."
188+ liftM CH (openFd source ReadOnly Nothing defaultFileFlags)
191+-- |Close the `CryptHandle`
192+closeHandle :: CryptHandle -> IO ()
194+closeHandle (CH h) = closeFd h
197+closeHandle UseRdRand = return ()
201+fdReadBS :: Fd -> Int -> IO B.ByteString
203+ allocaBytes n $ \buf -> do
204+ rc <- fdReadBuf fd buf (fromIntegral n)
206+ 0 -> ioError (ioeSetErrorString (mkIOError eofErrorType "fdRead" Nothing Nothing) "EOF")
207+ n' -> B.packCStringLen (castPtr buf, fromIntegral n')
210+-- |Read random data from a `CryptHandle`
211+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
213+hGetEntropy (CH h) = fdReadBS h
216+hGetEntropy UseRdRand = \n -> do
217+ B.create n $ \ptr -> do
218+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
220+ (fail "RDRand failed to gather entropy")
226+foreign import ccall unsafe "cpu_has_rdrand"
227+ c_cpu_has_rdrand :: IO CInt
229+foreign import ccall unsafe "get_rand_bytes"
230+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
232+cpuHasRdRand :: IO Bool
233+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
236+-- |Inefficiently get a specific number of bytes of cryptographically
237+-- secure random data using the system-specific facilities.
72−-- A less maliable mixing can be accomplished by replacing `xor` with a
239+-- Use '/dev/urandom' on *nix and CryptAPI when on Windows. In short,
73−-- composition of concat and cryptographic hash.
240+-- this entropy is considered cryptographically secure but not true
74−getHardwareEntropy :: Int -- ^ Number of bytes
241+-- entropy.
75− -> IO (Maybe B.ByteString)
242+getEntropy :: Int -> IO B.ByteString
76−getHardwareEntropy = hardwareRandom
243+getEntropy n = do
245+ e <- hGetEntropy h n