@@ -8,246 +8,69 @@
9 Currently supporting:
9 Currently supporting:
11− - Windows via CryptoAPO
11+ - Windows via CryptoAPI
12 - *nix systems via @\/dev\/urandom@
12 - *nix systems via @\/dev\/urandom@
13− - QNX
13+ - Includes QNX
14− - Xen only when RDRAND is available.
14+ - ghcjs/browser via JavaScript crypto API.
17module System.Entropy
17module System.Entropy
18− ( getEntropy
18+ ( getEntropy,
19− , CryptHandle
20+ CryptHandle,
20− , openHandle
21+ openHandle,
21− , hGetEntropy
22+ hGetEntropy,
22− , closeHandle
23+ closeHandle
25−#ifndef XEN
26+#ifdef ghcjs_HOST_OS
26−import Control.Monad (liftM, when)
27+import System.EntropyGhcjs
27−import System.IO.Error (mkIOError, eofErrorType, ioeSetErrorString)
28+#elif defined(isWindows)
28−import Foreign (allocaBytes)
29+import System.EntropyWindows
30−import Control.Monad (when)
31+import System.EntropyNix
32−import Data.ByteString as B
34−#if defined(isWindows)
34+import qualified Data.ByteString as B
35−{- C example for windows rng - taken from a blog, can't recall which one but thank you!
35+import Control.Exception (bracket)
37− #include <Wincrypt.h>
40− // DISCLAIMER: Don't forget to check your error codes!!
41− // I am not checking as to make the example simple...
43− HCRYPTPROV hCryptCtx = NULL;
44− BYTE randomArray[128];
46− CryptAcquireContext(&hCryptCtx, NULL, MS_DEF_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
47− CryptGenRandom(hCryptCtx, 128, randomArray);
48− CryptReleaseContext(hCryptCtx, 0);
51−import Data.ByteString.Internal as BI
52−import Data.Int (Int32)
53−import Data.Word (Word32, Word8)
54−import Foreign.C.String (CString, withCString)
55−import Foreign.C.Types
56−import Foreign.Ptr (Ptr, nullPtr, castPtr)
57−import Foreign.Marshal.Alloc (alloca)
58−import Foreign.Marshal.Utils (toBool)
59−import Foreign.Storable (peek)
62−foreign import ccall unsafe "cpu_has_rdrand"
63− c_cpu_has_rdrand :: IO CInt
65−foreign import ccall unsafe "get_rand_bytes"
66− c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
68−cpuHasRdRand :: IO Bool
69−cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
78−-- Define the constants we need from WinCrypt.h
80−msDefProv = "Microsoft Base Cryptographic Provider v1.0"
82−provRSAFull = fromIntegral 1
83−cryptVerifyContext :: Word32
84−cryptVerifyContext = fromIntegral 0xF0000000
86−-- Declare the required CryptoAPI imports
87−foreign import stdcall unsafe "CryptAcquireContextA"
88− c_cryptAcquireCtx :: Ptr Word32 -> CString -> CString -> Word32 -> Word32 -> IO Int32
89−foreign import stdcall unsafe "CryptGenRandom"
90− c_cryptGenRandom :: Word32 -> Word32 -> Ptr Word8 -> IO Int32
91−foreign import stdcall unsafe "CryptReleaseContext"
92− c_cryptReleaseCtx :: Word32 -> Word32 -> IO Int32
94−cryptAcquireCtx :: IO Word32
96− alloca $ \handlePtr ->
97− withCString msDefProv $ \provName -> do
98− stat <- c_cryptAcquireCtx handlePtr nullPtr provName (fromIntegral 1) (fromIntegral cryptVerifyContext)
101− else fail "c_cryptAcquireCtx"
103−cryptGenRandom :: Word32 -> Int -> IO B.ByteString
105− BI.create i $ \c_buffer -> do
106− stat <- c_cryptGenRandom (fromIntegral h) (fromIntegral i) c_buffer
109− else fail "c_cryptGenRandom"
111−cryptReleaseCtx :: Word32 -> IO ()
112−cryptReleaseCtx h = do
113− stat <- c_cryptReleaseCtx h 0
116− else fail "c_cryptReleaseCtx"
118−-- |Inefficiently get a specific number of bytes of cryptographically
37+-- |Get a specific number of bytes of cryptographically
119−-- 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)
121−-- This function will return zero bytes
41+-- The returned random value is considered cryptographically secure but not true entropy.
122−-- on platforms without a secure RNG!
123−getEntropy :: Int -> IO B.ByteString
127− if b then hGetEntropy UseRdRand n
130− h <- cryptAcquireCtx
131− bs <- cryptGenRandom h n
136−-- |Open a handle from which random data can be read
137−openHandle :: IO CryptHandle
141− if b then return UseRdRand
144− liftM CH cryptAcquireCtx
146−-- |Close the `CryptHandle`
147−closeHandle (CH h) = cryptReleaseCtx h
149−-- |Read from `CryptHandle`
150−hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
151−hGetEntropy (CH h) = cryptGenRandom h
153−hGetEntropy UseRdRand =
154− B.create n $ \ptr -> do
155− r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
157− (fail "RDRand failed to gather entropy")
161−{- Not windows, assuming nix with a /dev/urandom -}
163−import Foreign.C.Types
164−import Data.ByteString.Internal as B
166−data CryptHandle = UseRdRand -- or die trying
168−import System.Posix (openFd, closeFd, fdReadBuf, OpenMode(..), defaultFileFlags, Fd)
171−source = "/dev/urandom"
173−-- |Handle for manual resource mangement
181−-- |Open a `CryptHandle`
182−openHandle :: IO CryptHandle
186− if b then return UseRdRand
190− error "entropy: On halvm there is no entropy other than RDRAND."
192− liftM CH (openFd source ReadOnly Nothing defaultFileFlags)
195−-- |Close the `CryptHandle`
196−closeHandle :: CryptHandle -> IO ()
198−closeHandle (CH h) = closeFd h
201−closeHandle UseRdRand = return ()
205−fdReadBS :: Fd -> Int -> IO B.ByteString
207− allocaBytes n $ \buf -> do
208− rc <- fdReadBuf fd buf (fromIntegral n)
210− 0 -> ioError (ioeSetErrorString (mkIOError eofErrorType "fdRead" Nothing Nothing) "EOF")
211− n' -> B.packCStringLen (castPtr buf, fromIntegral n')
214−-- |Read random data from a `CryptHandle`
215−hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
217−hGetEntropy (CH h) = fdReadBS h
220−hGetEntropy UseRdRand = \n -> do
221− B.create n $ \ptr -> do
222− r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
224− (fail "RDRand failed to gather entropy")
230−foreign import ccall unsafe "cpu_has_rdrand"
231− c_cpu_has_rdrand :: IO CInt
233−foreign import ccall unsafe "get_rand_bytes"
234− c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
236−cpuHasRdRand :: IO Bool
237−cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
240−-- |Inefficiently get a specific number of bytes of cryptographically
241−-- secure random data using the system-specific facilities.
243−-- Use '/dev/urandom' on *nix and CryptAPI when on Windows. In short,
43+-- On some platforms this requires a file handle which can lead to resource
244−-- this entropy is considered cryptographically secure but not true
44+-- exhaustion in some situations.
245−-- entropy.
45+getEntropy :: Int -- ^ Number of bytes
246−getEntropy :: Int -> IO B.ByteString
46+ -> IO B.ByteString
247−getEntropy n = do
47+getEntropy = bracket openHandle closeHandle . flip hGetEntropy
249− e <- hGetEntropy h n
49+-- |Get a specific number of bytes of cryptographically
250− closeHandle h
50+-- secure random data using a supported *hardware* random bit generator.
252−#endif
52+-- If there is no hardware random number generator then @Nothing@ is returned.
253−{- OS Test -}
53+-- If any call returns non-Nothing then it should never be @Nothing@ unless
54+-- there has been a hardware failure.
56+-- If trust of the CPU allows it and no context switching is important,
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